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= December 25 = | |||
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== Mass of oscillating neutrino == | |||
= June 11 = | |||
From the ] it follows that a particle that is not subject to external forces must have constancy of mass. | |||
== Balloon on bus accelerating forward. == | |||
If I am right, this means that the mass of the neutrino cannot change during the ], although its flavoring may. Is this written down somewhere? Thank you. ] (]) 19:24, 25 December 2024 (UTC) | |||
This was a problem from a physics book I vaguely remember; I never quite figured it out and someone else's question reminded me. | |||
:Any (flavored) neutrino that is really observed is a superposition of two or three mass eigenstates. This is actually the cause of ]. So, the answer to your question is complicated. ]_] 19:40, 25 December 2024 (UTC) | |||
A bus is accelerating forward. A balloon is tied to a string attached to a chair. Why does the balloon go forward as well. If I remember correctly it was from one of the Feynman lectures on physics book so I doubt the question is wrong. But to me it would seem the balloon should go backwards, not forwards. Any possible explanations that involve simple Newtonian mechanics (nothing about fluids or pressure; I don't think it said WHAT the balloon was filled with but I'm assuming standard balloon with helium.] (]) 03:16, 11 June 2009 (UTC) | |||
:Important note: particle physicists today generally only ever use "mass" to mean "]" and never anything else: . Like the term says, invariant mass is well, invariant, it never changes ever, no matter what "external forces" may or may not be involved. Being proper particle-icans and following the standard practice in the field, then, the three neutrino masses are constant values. ..."Wait, three?" Yeah sure, turns out ]. As mentioned, due to Quantum Weirdness we aren't able to get these different states "alone by themselves" to measure each by itself, so we only know the differences of the squares of the masses. Yeah welcome to quantum mechanics. | |||
:]: "Quantum mechanics describes nature as absurd from the point of view of common sense. And yet it fully agrees with experiment. So I hope you can accept nature as She is {{snd}} absurd." --] (]) 06:06, 26 December 2024 (UTC) | |||
::The equation <math>E^2 = (p c)^2 + \left(m_0 c^2\right)^2</math> uses invariant mass {{math|''m''<sub>0</sub>}} which is constant if {{math|''E''}} and {{math|''p''}} are constant. The traveling neutrino has a varying mass mixture of different flavors with different masses. If a mixture of different masses changes, you would expect the resulting mass to change with it. But somehow this does not happen as the neutrino mass mixture changes. These mixture changes cannot be any changes. The changes must be such that the resulting mass of the traveling neutrino remains constant. My question is whether this is described somewhere. ] (]) 11:16, 26 December 2024 (UTC) | |||
:::I freely confess I'm uncertain exactly what's being "asked for" or "gotten at" here. Have you looked at the ] article? From it: {{tpq|That is, the three neutrino states that interact with the charged leptons in ]s are each a different ] of the three (propagating) neutrino states of definite mass. Neutrinos are emitted and absorbed in weak processes in flavor ]s '''but travel as mass eigenstates.'''}} | |||
:::What is it that we're "doing" with the ] here? For the neutrino, we don't have a single value of "mass" to plug in for <math>m_0</math>, because we can't "see" the individual mass eigenstates, only some ] of them. What you want for describing neutrino interactions is ], which is special relativity + QM. (Remember, relativity is a "classical" theory, which presumes everything always has single well-defined values of everything. Which isn't true in quantum-world.) --] (]) 18:41, 26 December 2024 (UTC) | |||
::::Not all potential evolutions of a linear combination of unequal values produce constant results. Constancy can only be guaranteed by a constraint on the evolutions. Does the fact that this constraint is satisfied in the case of neutrino oscillation follow from the ], or does this formulation allow evolutions of the mass mixture for which the combination is not constant? If the unequal values are unknown, I have no idea of how such a constraint might be formulated. I think the OP is asking whether this constraint is described somewhere. --] 00:51, 27 December 2024 (UTC) | |||
<s>:By who's perspective? To a person on the bus, the balloon will drift backwards, until the string stops it, and then it will go forwards with the bus. However, to a person standing on the street, the balloon will drift ''forwards'' but at a rate slower than the bus does, since the air in the bus generates a small amount of friction on the balloon, and will push if forward slightly. --].].] 03:28, 11 June 2009 (UTC)</s> | |||
= December 27 = | |||
::No Jayron, the balloon actually moves foward (even from the perspective of the person inside the bus) because the air around the balloon is heavier than the balloon and moves backward forcing the balloon forward (just as it falls downward, forcing the balloon upward). ] (]) 03:48, 11 June 2009 (UTC) | |||
== Low-intensity exercise == | |||
:::Ah yes, of course. That makes sense. Scratch my earlier reply. --].].] 03:56, 11 June 2009 (UTC) | |||
If you exercise at a low intensity for an extended period of time, does the ] still occur if you do it for long enough? Or does it only occur above a certain threshold intensity of exercise? ] (]) 20:13, 27 December 2024 (UTC) | |||
::::'''Actually''' ... when the bus accelerates '''several''' forces will affect the ballon's motion: | |||
:Hows about you try it and report back? :) ←] <sup>'']''</sup> ]→ 21:31, 27 December 2024 (UTC) | |||
::::*the motion of the bus, pulling the string -- the most significant force, causing the balloon to move forwards with the bus | |||
::I wanted to try it just today, but I had to exchange the under-desk ] I got for Christmas for a different model with more inclined treadles because with the one I got, my knees would hit the desk at the top of every cycle. Anyway, I was hoping someone else tried it first (preferably as part of a formal scientific study) so I would know if I could control whether I got a runner's high from exercise or not? ] (]) 03:09, 28 December 2024 (UTC) | |||
::::*the balloon's inertial mass -- causing it to drift backwards relative to the passengers | |||
Also, sorry for adding to my own question, but here's a related one: is it known whether the length of a person's ] (which is inversely correlated with its sensitivity) influences whether said person gets a runner's high from exercise (and especially from low-intensity exercise)? ] (]) 03:14, 28 December 2024 (UTC) | |||
::::*assuming calm atmospheric conditions (no wind), air pressure or friction would be a small factor opposing the balloon's drifting motion <small><span class="autosigned">—Preceding ] comment added by ] (] • ]) 09:35, 11 June 2009 (UTC)</span></small><!-- Template:Unsigned --> <!--Autosigned by SineBot--> | |||
:::::You forgot its bouyancy, which is the one which causes it to drift forwards relative to the bus. ] (]) 10:14, 11 June 2009 (UTC) | |||
:::::Also, the bus will pull the string in the opposite direction the balloon is being pushed. If it is indeed moving forward, the bus will pull the balloon back. — ] 14:10, 11 June 2009 (UTC) | |||
:Yes bouyancy is the key here. The gas in the balloon is lighter than air (which is why it's floating). Imagine a cork floating in a glass of water in the bus. As the bus accelerates forwards - the water in the glass sloshes towards the back of the bus - which forces the lighter cork to move forwards. That's very easy to visualize because you can see the water. However, the same thing is happening with the balloon which is floating in the air. When the bus accelerates, the air sloshes towards the back of the bus - forcing the balloon to move forwards...it seems counter-intuitive - but that's because we're not used to seeing things that are lighter than air. ] (]) 12:06, 11 June 2009 (UTC) | |||
::We need to state that we are referring to a balloon that has positive buoyancy--it would rise toward the ceiling if untied. My daughter's physics class was given this problem, and the debate was so fierce that she drove to a store, purchased a balloon, and verified by experiment that the balloon goes forward. I pointed out to her that one result of ] is that accelerated frames of reference are indistinguishable, if the buoyant force opposes gravity, it must also oppose any other acceleration. on the bus, if you tie a plumb bob and a balloon to the same pivot point, the two strings will form a straight line in steady state tilt or steady state acceleration. -] (]) 13:03, 11 June 2009 (UTC) | |||
:::Yes, the equivalence principle is the easy way to see this. A bus accelerating forward is equivalent to a bus tilted backward (in both cases you're pressed into your seat). A helium balloon has to behave the same relative to the frame of the bus in both cases, and that means moving diagonally in the front-ceiling direction. -- ] (]) 16:17, 11 June 2009 (UTC) | |||
::::Why would the balloon move forward? I don't understand the part about the air inside the bus "sloshing" backwards. Yes, there will be "sloshing," but will it be only backwards? I think such "sloshing" will be complex, going around the seats and any other complexity to what otherwise might be a simple geometric volume. Supposing instead of a bus, we were considering a hollow cylinder. And instead of windows, which might be opened or closed, we considered the cylinder totally closed. Would the balloon still move forward? If so, that would be assuming that the air at the back of the cylinder became more dense, or compressed, than the air at the front of the cylinder. But is this really the case, to any appreciable degree, at acceleration rates concerning busses? I have my doubts about that. In theory that sort of reasoning might apply. But I am not so sure it applies in a bus accelerating from a standstill, no matter how fast the driver attempted to accelerate the bus. I think a more likely explanation for the balloon moving forward might be complex air currents resulting especially from open windows. But I am not sure. ] (]) 16:37, 11 June 2009 (UTC) | |||
:::::Yes, even in your cylinder example, it would happen. Yes, the acceleration causes an increase in density at the rear of the bus. If the bus starts turning left, the density will increase on the right and the balloon wil move to the left.--] (]) 16:42, 11 June 2009 (UTC) | |||
== ] vs ] == | |||
:::::Yes, that's exactly what happens. The air at the back of the balloon becomes more dense than the air at the front of it creating a pressure gradient force on the balloon that's enought to push it forwards. This is entirely equivalent to the vertical pressure gradient that makes the balloon float. ] (]) 18:24, 11 June 2009 (UTC) | |||
:::::Do you understand why the balloon floats in the first place? The reason it moves forward under acceleration is exactly the same as the reason it floats. In a completely sealed cylinder in steady-state 1G forward acceleration, the balloon will be at an angle of 45 degrees even though there is no air movement whatsoever. You really need to purchase a balloon and get someone else to drive you and accelerate. The effect is dramatic, not subtle at all. -] (]) 19:55, 11 June 2009 (UTC) | |||
Hi, | |||
::::::Interesting. Thank you. ] (]) 18:28, 11 June 2009 (UTC) | |||
What is the difference between an auxotroph and a fastidious organism? It seems to me the second one would have more requirements than the first one, but the limit between the two definitions is rather unclear to me. | |||
::::::: Aight thanks guys ] (]) 19:25, 11 June 2009 (UTC) | |||
Thank you ] (]) 23:17, 27 December 2024 (UTC) | |||
== Y Chromosome == | |||
:I'm not 100% sure, but it seems to me that an auxotroph is a specific type of a fastidious organism. ] (]) 03:02, 28 December 2024 (UTC) | |||
:Symbiosis aside, it would seem that most auxotrophs would be fastidious organisms, but there could be many more fastidious organisms that aren't auxotrophs. Auxotrophs specifically can't produce organic compounds on their own. There are a LOT of organisms that rely on the availability of non-organic nutrients, such as specific elements/minerals. For instance, vertebrates require access to calcium. Calcium is an element; our inability to produce it does not make us auxotrophs. | |||
:But perhaps symbiosis would allow an organism to be an auxotroph without being a fastidious organism? For instance, mammals tend to have bacteria in our guts that can digest nutrients that our bodies can't on their own. Perhaps some of those bacteria also assemble certain nutrients that our bodies can't? -- ] (]) 14:27, 28 December 2024 (UTC) | |||
= December 28 = | |||
If I understand genetics correctly (hopefully I do) then everything that makes a person male comes from their father via the Y chromosome, whereas what makes a person female comes from one X chromosome of the mother and father respectively. | |||
== Paper with wrong enantiomer in a figure == | |||
Therefore does this fact of nature indicate that generally men (or male animals even, if this helps rule out the cultural and psychology influences) would prefer the birth of a son? | |||
In the following reference: | |||
In other words, a father completely influences the male characteristics of his sons but only half the female characteristics of his daughters. So in the interest of passing on one's genes (which according to ] and natural selection indicates is the main reason for competition for mates and for having children) wouldn't men prefer sons while women would be indifferent? Perhaps this also explains why inheritance laws have typically favored sons in most cultures? ] (]) 09:54, 11 June 2009 (UTC) | |||
:{{cite journal |last1=Quack |first1=Martin |last2=Seyfang |first2=Georg |last3=Wichmann |first3=Gunther |title=Perspectives on parity violation in chiral molecules: theory, spectroscopic experiment and biomolecular homochirality |journal=Chemical Science |date=2022 |volume=13 |issue=36 |pages=10598–10643 |doi=10.1039/d2sc01323a |pmid=36320700}} | |||
:It seems to me that since males have no female parts, they wouldn't influence a female offspring at all. Rather, the fathers female ancestors gens, plus the mothers genes, would control the female parts. | |||
it is stated in the caption of Fig. 8 that ''S''–] is predicted to be lower in energy due to ], but in the figure the wrong enantiomer is shown on this side. Which enantiomer is more stable, according to the original sources for this data? –] (]]) 08:18, 28 December 2024 (UTC) | |||
== Where can I find data on the circulation and citation rates of these journals? == | |||
:As for whether this affects favoritism or not, is beyond me.]rew ] ] 10:31, 11 June 2009 (UTC) | |||
::My apologies if I'm stating the obvious, but men are XY and women are XX. Therefore men do influence half of what makes their daughters female (in terms of sex chromosomes; female being the "default" sex is an issue beyond the scope of this question). You know: | |||
::Xm1Ym1 (father) + Xf1Xf2 (mother) | |||
::could result in Xm1Xf1 (female) , Xm1Xf2 (female), Ym1Xf1 (male) or Ym1Xf2 (male). | |||
Hello everyone, To write an article about a scientist, you need to know, where can I find data on circulation and citation rates of journals from ? ] (]) 09:58, 28 December 2024 (UTC) | |||
::Of course the man's X chromosome came from their own mother but the man's Y came from his father; we could got back generation after generation but I don't see how this impacts the original question: Do men favor son's because they completely contribute what makes their sons male but only contribute half of what makes their daughters female. ] (]) 10:53, 11 June 2009 (UTC) | |||
== So-called “Hydrogen water” == | |||
:::The XY chromosome system is the ] in most mammals, but not in all animals - birds have an entirely different genetic system (see ]); some reptiles have a non-genetic ]; some fish and molluscs can even change sex. So in evolutionary terms the Y chromsome is a fairly recent arrival. Even if we stick to mammals, a father contributes more genetic material to his daughters than to his sons (the ] is 153 million base pairs long; the ] only 60 million base pairs) so an evolutionary argument could predict favouring daughters over sons. OTOH, if there are fewer males than females in the adult population, then a son will produce more grandchildren, on average, than a daughter ... ] (]) 11:02, 11 June 2009 (UTC) | |||
I saw an ad promoting a device which presumable splits water into | |||
:There are ~25,000 genes that affect a person's physical characteristics, most of which are NOT on the X or Y chromosome. Early in ], the gender is completely indeterminate -- males and females all have the same embryonic tissues (]s and ]s) that will go on to form the basic internal genital structures through the process of ]. The embryonic ] and genital folds will develop into the external genital structures. Therefore, you should think of the Y chromosome as having a "switch" (the ] gene) that turns on a complex genetic program that results in the embryonic ]s becoming ] in a male, whereas the absence of the SRY gene (which is true in XX females but also in ] and ]) the default is to form ovaries. Everything follows from that point in development -- testes produce ] that causes regression of the female internal structures, and ] that promotes development of characteristic male external genitalia. In the absence of these signals (and probably in the presence of some X-linked gene signals), the system defaults to a female phenotype. Most of the genes that are involved in this process are actually NOT on the sex chromosomes, so would allow contributions from both parents, even though the switch that starts off the process is on the Y. Why would it make sense for the small number of genes on the Y chromosome to be more "selfish" than all the others? There are far more genes on the ]. --- ] (]) 11:41, 11 June 2009 (UTC) | |||
hydrogen and oxygen and infuses water with extra hydrogen, to | |||
::Aren't you overlooking the importance of the SRY "switch"? It seems rather easy to argue gender has a profound effect on many other genes. My hypothesis is that men would favor sons as they are genetically and ultimately phenotypically more related to their fathers versus daughters. The gene/chromosome is exclusive to one parent and has a massive influence on the development of the individual. ] (]) 12:05, 11 June 2009 (UTC) | |||
a claimed surplus of perhaps 5 ppm, which doesn’t seem like much. I found a review article which looked at several dozen related studies that found benefits:https://pmc.ncbi.nlm.nih.gov/articles/PMC10816294/ . | |||
I’ve noticed that carbon dioxide or chlorine (chloramine?) dissolved in water work their way out pretty easily, so I wonder if dissolved hydrogen could similarly exit hydrogen enriched water and be burped or farted out, rather than entering the blood stream and having health benefits. is it more than the latest snake oil? ] (]) 23:01, 28 December 2024 (UTC) | |||
: OK - these explanations have gone WAY off the rails. It's not complicated: | |||
:Yes, the dissolved hydrogen will exit the water just as quickly (even faster, because of its low ] and complete lack of ] or capability for ]), and even if it does enter the bloodstream, it will likewise get back out in short order before it can actually do anything (which, BTW, is why ]s use it in their breathing mixes -- because it gets out of the bloodstream so much faster and therefore doesn't ]) -- so, I don't think it will do much! ] (]) 01:50, 29 December 2024 (UTC) | |||
::It's conceivable it might take out the chloramine, I guess. I don't think there's very much of it, but it tastes awful, which is why I add a tiny bit of vitamin C when I drink tap water. It seems to take very little. Of course it's hard to tell whether it's just being masked by the taste of the vitamin C. --] (]) 02:12, 29 December 2024 (UTC) | |||
:If you just want to split water into hydrogen and oxygen all you need is ]. You don't say where you saw this ad but if it was on a socia media site forget it. ]|] 11:47, 29 December 2024 (UTC) | |||
::If this so-called hydrogen water was emitting hydrogen bubbles, would it be possible to set it afire? ←] <sup>'']''</sup> ]→ 14:03, 1 January 2025 (UTC) | |||
:We once had an article on this topic, but see ]. ] (]) 22:27, 1 January 2025 (UTC) | |||
::I don't know if it is rubbish or not but a quick look on the web indicates to me it is notable enough for Misplaced Pages. I didn't see anything indicating it definitely did anything useful so such an article should definitely have caveats. I haven't seen any expression of a potential worry either so it isn't like we'd be saying bleach is a good medicine for covid. ] (]) 23:07, 1 January 2025 (UTC) | |||
:'']'' does not sound of exceptionally high quality. ] (]) 01:05, 2 January 2025 (UTC) | |||
= December 29 = | |||
: Women have two X chromosomes - men have one X and one Y. The child gets one of the mother's sex chromosomes and one of the father's - but it's random which one. So if the baby is a girl, she got one of her mother's X chromosomes (it's random which one) and the X chromosome from her father. If the baby is a boy - he gets one of his mother's X chromosomes (again, at random) and the Y chromosome from the father. Either way - the kid got one of the two genes from the mother and one from the father so that is no reason to prefer to have a boy child. | |||
== Potential energy vs. kinetic energy. Why not also "]" vs. "]"? E.g. in the following case: == | |||
: Where the confusion lies is that someone here thinks that a girl baby could get both of her X chromosomes from the mother and a baby boy could get both the X and the Y from the father. '''That's NOT what happens!''' But if that were the case then in the case of a girl, it would be true to say that there are two possibilities: Both X's from mommy or one X from mommy and one from daddy. There would therefore ''hypothetically'' be (on average) 75% of the genetic material in girls coming from the mother and 25% from the father. In the case of a boy - there would certainly have to have gotten the Y from the father but the X could come from either parent - so on average, 75% of the genetic material in boys would come from the father and 25% from the mother. It would then make evolutionary sense for the father to 'prefer' boys to girls because on average they'd contain more of his genetic material. I think that's what the OP imagines. ''But that's '''not''' what happens.'' | |||
In a ], reaching the highest point involves - both a minimal kinetic energy - along with a maximal potential energy, whereas reaching the lowest point involves - both a maximal kinetic energy - along with a minimal potential energy. Thus the mechanical energy becomes the sum of kinetic energy + potential energy, and ''is a conserved quantity''. | |||
: '''If''' fathers prefer their boy offspring to their girls (and I'm not convinced of that) - it's more likely to be that it is the traditional role of the father to pass on male-dominated skills (hunting, tracking, boat-building, beer-drinking, whatever) to their sons and for women to pass on traditionally female-oriented skills <small>(nagging, shopping, etc??<shrug>)</small> to their daughters - so it would perhaps make evolutionary sense for the males to preferentially bond with their sons and the females to bond with their daughters. ] (]) 12:26, 11 June 2009 (UTC) | |||
::Basically what I said, except alot clearer and alot more complicated...Meh, whatever.]rew ] ] 12:40, 11 June 2009 (UTC) | |||
So I wonder if it's reasonable to define also "potential velocity" vs. "kinetic velocity", and claim that in a harmonic oscillator, reaching the highest point involves - both a ''minimal'' "kinetic velocity" (i.e. involves what we usually call ''a rest'') - along with a ''maximal'' "potential velocity", whereas reaching the lowest point involves - both a ''maximal'' "kinetic velocity" (i.e. involves what we usually call ''the actual velocity'') - along with a ''minimal'' "potential velocity". Thus we can also define "mechanical velocity" as the sum of "kinetic velocity" + "potential velocity", and ''claim that the mechanical velocity is a conserved quantity'' - at least as far as a harmonic oscillator is concerned. | |||
::As to whether fathers prefer boy offspring, depressingly it seems to be so. Here is a little evidence on the subject. . Interestingly, it seems that the preference-behaviour is shown by people who would say, and probably believe, that they have no such preference. ] (]) 19:59, 11 June 2009 (UTC) | |||
Reasonable? | |||
:I don't disagree with any of the above but I just want to point out that, unless I'm missing something, evolutionary arguments regarding sex-preference don't add up. The only way a gene causing men to prefer sons would be selected for is if it caused such a strong preference that it made men kill their daughters (or render them infertile somehow). Can such a gene be selected otherwise? ] (]) 13:13, 11 June 2009 (UTC) | |||
Note that I could also ask an analogous question - as to the concept of "potential momentum", but this term is already used in the theory of ] for another meaning, so for the time being I'm focusing on velocity. | |||
Okay, this is getting silly. '''No one here''' (at least that I'm aware of) thinks both X's come from the mother. See what I posted above in response to Drew... | |||
] (]) 12:26, 29 December 2024 (UTC) | |||
Xm1Ym1 (father) + Xf1Xf2 (mother) | |||
: 'kinetic velocity' is just 'velocity'. 'potential velocity' has no meaning. ] (]) 13:56, 29 December 2024 (UTC) | |||
could result in Xm1Xf1 (female) , Xm1Xf2 (female), Ym1Xf1 (male) or Ym1Xf2 (male). | |||
::Per my suggestion, the ratio between distance and time is not called "velocity" but rather "kinetic velocity". | |||
::Further, per my suggestion, if you don't indicate whether the "velocity" you're talking about is a "kinetic velocity" or a "potential velocity" or a "mechanical velocity", the very concept of "velocity" alone has no meaning! | |||
::On the other hand, "potential velocity" is defined as the difference between the "mechanical velocity" and the "kinetic velocity"! Just as, this is the case if we replace "velocity" by "energy". For more details, see the example above, about the harmonic oscillator. ] (]) 15:14, 29 December 2024 (UTC) | |||
:::You could define the ''potential velocity'' of a body at a particular height as the velocity it would hit the ground at if dropped from that height. But the sum of the potential and kinetic velocities would not be conserved; rather <math>v_{\mathrm{tot}} = \sqrt{v_{p}^{2} + v_{k}^{2}}</math> would be constant. ] (]) 18:54, 29 December 2024 (UTC) | |||
::::Thank you. ] (]) 20:07, 29 December 2024 (UTC) | |||
::: 'Potential velocity' has no meaning. You seem to be arguing that in a system where energy is conserved, but is transforming between kinetic and potential energy, (You might also want to compare this to ].) then you can express that instead through a new conservation law based on velocity. But this doesn't work. There's no relation between velocity and potential energy. | |||
::: In a harmonic oscillator, the potential energy is typically coming from some central restoring force with a relationship to ''position'', nothing at all to do with velocity. Where some axiomatic external rule (such as ] applying, because the system is a mass on a spring) ''happens'' to relate the position and velocity through a suitable relation, then the system will then (]) behave as a harmonic oscillator. But a different system (swap the spring for a ]) doesn't have this, thus won't oscillate. ] (]) 00:00, 30 December 2024 (UTC) | |||
::::Let me quote a sentence from my original post: {{tq|Thus we can also...claim that the mechanical velocity is a conserved quantity - '''at least as far as a harmonic oscillator is concerned'''.}} | |||
::::What's wrong in this quotation? ] (]) 07:52, 30 December 2024 (UTC) | |||
:::::It is true, not only for harmonic oscillators, provided that you define {{math|1='''v'''<sub>pot</sub> = − '''v'''<sub>kin</sub>}}. --] 09:07, 30 December 2024 (UTC) | |||
::::* You have defined some arbitrary values for new 'velocities', where their ''only'' definition is that they then demonstrate some new conservation law. Which is really the conservation of energy, but you're refusing to use that term for some reason. | |||
::::: As Catslash pointed out, the conserved quantity here is proportional to the square of velocity, so your conservation equation has to include that. It's simply wrong that any linear function of velocity would be conserved here. Not merely we can't prove that, but we can prove (the sum of the squares diverges from the sum) that it's actually contradicted. For any definition of 'another velocity' which is a linear function of velocity. | |||
::::: Lambiam's definition isn't a conservation law, it's merely a ]. The sum of any value and its ] is always ]. ] (]) 14:04, 30 December 2024 (UTC) | |||
::::::{{small|It is a law of conservation of ''sanity''. Lacking a definition of potential energy, other than by having been informed that kinetic energy + potential energy is a conserved quantity, there is not much better we can do.}} --] 11:20, 31 December 2024 (UTC) | |||
::::::: We have a perfectly viable definition of potential energy. For a pendulum it's based on the change in height of the pendulum bob against gravity. For some other oscillators it would involve the work done against a spring. ] (]) 16:33, 31 December 2024 (UTC) | |||
::::::::Oops, I mistyped. I meant to write: | |||
:::::::::"{{small|Lacking a definition of potential velocity, other than by having been informed that kinetic velocity + potential velocity is a conserved quantity, there is not much better we can do.}}" | |||
:::::::: --] 23:32, 31 December 2024 (UTC) | |||
= December 30 = | |||
It seems like a simple misunderstanding but Steve, I would appreciate if you would cross out that section of your discussion since no one is advocating that point of view. | |||
== Saltiness comparison == | |||
Anyway, what I '''AM''' saying is the Y chromosome is ultimately responsible for the creation of a male child. The father is the only one with a Y chromosome and thus 100% responsible for the gender characteristics of a male (XY) child (X from the mother, Y from the father). In the case of a daughter both parents contribute equally to the gender characteristics as one X comes from the mother and one from the father. | |||
Is there some test one might easily perform in a home ] to compare the ] (due to the concentration of ] ]s) of two liquid preparations, without involving biological ]s? --] 09:22, 30 December 2024 (UTC) | |||
Therefore as a father is wholly responsible for the male characteristics of the son but only 50% responsible for the gender characteristics of a daughter it follows that men would prefer sons. ] (]) 13:40, 11 June 2009 (UTC) | |||
:The gender is decided by the Y chromosome, but the characteristics are decided by the combination. Let me pose a hypothetical question that may make things a little clearer. What would happen if someone where born with two Y chromosomes?]rew ] ] 14:02, 11 June 2009 (UTC) | |||
::That's not possible, the embryo would fail to develop. XYY can occur but YY can not as there are many genes on X which people require to live. However I am not sure this hypothetical applies to the question... I think the terminology may be throwing people off. Also Drew, can you provide a citation or example for confirmation of your statement "The gender is decided by the Y chromosome, but the characteristics are decided by the combination."? | |||
::The male gender characteristics are the result of the activation of a male phenotype by the SRY gene. Therefore what makes a person male and all the male characteristics (not ALL characteristics but those which are unique to males) are caused by the Y chromosome which comes from the father. Does this clear up any confusion on the point I am trying to make? ] (]) 14:44, 11 June 2009 (UTC) | |||
::According to ] he'd be some kind of a super-hero. In reality, he'd have ] which I suggest you read. Note that there are also ]...<small>(which, strangely, seem to be advertised a helluva lot in certain parts of downtown Dallas)</small>. If you're suggesting someone with two Y chromosomes and no X - they'd certainly never get as far as being born because there are a shit-load of genes on the X chromosome that you can't survive without - so the question is moot. ] (]) 14:41, 11 June 2009 (UTC) | |||
:Put two equally sized drops, one of each liquid, on a warm surface, wait for them to evaporate, and compare how much salt residue each leaves? Not very precise or measurable, but significant differences should be noticeable. {The poster formerly known as 87.81.230.195} ] (]) 10:21, 30 December 2024 (UTC) | |||
:That point of view makes no sense to me. An X chromosome has more genes than a Y chromosome which means that a man actually passes more of his genes to his dauthers than to his sons so, if anything, that naive application of the selfish gene principle would lead to men prefering their dauthers. ] (]) 14:37, 11 June 2009 (UTC) | |||
::Except I'm not refering to the number of genes, but rather to the impact the SRY gene has on the resulting phenotype caused by all the other genes. The Selfish Gene was an earlier work of Dawkins which he expanded on in ] which may explain a bit more the theory behind my reasoning. Essentially the father has a much greater impact on the phenotype of a son versus a daugther as everything which makes that son male comes from the father. For daughters the contribution is shared equally. ] (]) 14:50, 11 June 2009 (UTC) | |||
:::"Everything which makes that son male comes from the father" is a trick of language. It has no scientific meaning. The father's genetic material determines the sex of the child, whether male or female. The father supplies 50% of the genetic material whether the child is male or female (slightly less than 50% for a male). That includes 50% of the genes that are preferentially expressed in males and 50% of the genes that are preferentially expressed in females. The mother and father contribute equally to the phenotype of a male child and they contribute equally to the phenotype of a female child. -- ] (]) 15:24, 11 June 2009 (UTC) | |||
::::It's about activation, not just numbers. See my responses to Daruto and Looie below. ] (]) 16:44, 11 June 2009 (UTC) | |||
This reminds me of the work by ] on ] which is related to ] and ]. ] ] 15:03, 11 June 2009 (UTC) | |||
:Halleujah! This is what I've been getting at the whole time. I can't claim expertise in this stuff though and the articles actually seem a bit sparse, so can anybody explain whether any evidence confirm or contradicts my hypothesis that the father has a much greater impact on the phenotype of a son versus a daugther as everything which makes that son male comes from the father and thus men would prefer sons? ] (]) 15:43, 11 June 2009 (UTC) | |||
::Your hypothesis is false. As MedicalGeneticist explained (but maybe in too complicated a way), the things that make a man male are scattered all over the genome. The Y chromosome is tiny, and the main thing it contains is a set of "switches" whose function is to activate the male-related genes on other chromosomes. In females, these genes are present but they don't get activated. The contents of the Y chromosome differ very little across people. Therefore, the mother and father both have essentially equal impacts on the phenotype of a son. ] (]) 16:16, 11 June 2009 (UTC) | |||
:::Yet the switch makes all the difference. When the other genes are not activated then they do not impact the phenotype so ultimately the father DOES make a larger determination. ] (]) 16:28, 11 June 2009 (UTC) | |||
::The principle is sound, but the residue from one drop won't be measurable using kitchen equipment -- better to put equal amounts of each liquid in two warm pans (use enough liquid to cover the bottom of each pan with a thin layer), wait for them to evaporate and then weigh the residue! Or, if you're not afraid of doing some ], you could also try an indirect method -- bring both liquids to a boil, measure the temperature of both, and then use the formula for ] to calculate the saltiness of each! ] (]) 18:22, 30 December 2024 (UTC) | |||
::Clearly you're not refering to the number of genes. My point is that you probabily should be refering to the number of genes, unless you can show us that the inheritance of that single gene present in the Y chromosome is more relevant than the inheritance of all the genes present in the X chromosome which you haven't done so far, as far as I can see. Just saying that you are not talking about my point doesn't make it go away, mind you. ] (]) 16:21, 11 June 2009 (UTC) | |||
:::See above, it's more important because this gene controls the activation of the other genes you are refering to. If they aren't activated the phenotype doesn't change so ultimately the fact that it controls the activation makes it more important than the pure number of inactive genes. ] (]) 16:28, 11 June 2009 (UTC) | |||
::: |
:::Presumably the ''liquid preparations'' are not simple saline solutions, but contain other solutes - or else one could simply use a hydrometer. It is unlikely that Lambian is afraid of doing some algebra. ] (]) 18:57, 30 December 2024 (UTC) | ||
:<s>Assuming the liquid preparations are water-based and don't contain alcohols and/or detergents one can measure their rates of dispersion. Simply add a drop of food dye to each liquid and then time how rapidly droplets of each liquid disperse in distilled water. Materials needed: food dye, eye dropper, distilled water, small clear containers and a timer.</s> ] (]) 21:09, 30 December 2024 (UTC) | |||
:::The ] of a solution will indicate its molarity, but not identify the solute. ''Liquid preparations'' that might be found in a kitchen are likely to contain both salt and sugar. Electrical conductivity is a property that will be greatly affected by the salt but not the sugar (this does not help in distinguishing Na<sup>+</sup> from K<sup>+</sup> ions though). ] (]) 22:23, 30 December 2024 (UTC) | |||
::::I think it's rather obvious if something has control over a process then it is rather important. Not necessarily more important than the process but in this case it influences the outcome of gender, something the other genes don't do. I would also argue the fact that it alone determines gender makes it extremely important. The differences that result biologically because of gender are very far reaching. ] (]) 18:52, 11 June 2009 (UTC) | |||
::::That's what I'm thinking too -- use an ] to measure the ] of the preparation, and compare to that of solutions with known NaCl concentration (using a ]-type method). ] (]) 20:18, 31 December 2024 (UTC) | |||
:::::Well, I would argue that since all that gene does is determine gender that makes it extremely '''un'''important as far as it concerns the matter of wheather a father would prefer a son or a dauther. You've simply asserted the oposite point of view but without giving any real reasons for us to accept it. On the other hand I know for a fact that fathers love their dauthers. ] (]) 19:06, 11 June 2009 (UTC) | |||
:Quantitative urine test-strips for sodium seem to be available. They're probably covering the concentration range of tens to hundreds millimolar. ] (]) 00:58, 2 January 2025 (UTC) | |||
::Thanks, test strips seem more practical in the kitchen setting than an ohmmeter (why not call it a "]meter"?), for which I'd need to devise a way (or so I think) to keep the terminals apart at a steady distance. Test strips require a colour comparison, but I expect that a significant difference in salinity will result in a perceptible colour difference when one strip is placed across the other. Only experiment can tell whether this expectation will come true. Salinity is usually measured in g/L; for kitchen preparations a ballpark figure is 1 g/L. If I'm not mistaken this corresponds to {{nowrap|1=(1 g/L) / (58.443 g/mol) ≈}} {{nowrap|1=0.017 M = 17 ].}} I also see offers for salinity test strips, 0–1000 ppm, for "Science Education". --] 11:40, 2 January 2025 (UTC) | |||
:::Test strips surely come with a printed color-chart. But if all you are trying to do is determine which is more salty, then that's even easier than quantifying each separately. Caveat for what you might find for sale: some "salinity" tests are based on the chloride not the sodium, so a complex matrix that has components other than NaCl could fool it. ] (]) 18:44, 2 January 2025 (UTC) | |||
== The (uncommon?) terms "relativistic length", and "relativistic time". == | |||
:Getting back to the original question about "selfish genes" and wanting to pass on one's genes, the idea that a male should prefer sons based on wanting to pass on his genes has been adequately refuted. A male actually passes on slightly more genes to his daughters since the X chromosome carries more genes. Look at the ] article -- in some species, there are only 4 genes on the Y chromosome. Your argument attaches too much importance to the SRY gene. What if I "hypothesized" that people with orange eyes would rather have children with orange eyes because the "orange eye gene" is selfish? It just doesn't make sense. There are enough social/cultural reasons given for sex preference in offspring that your theory about a genetic basis just doesn't add anything useful. --- ] (]) 17:19, 11 June 2009 (UTC) | |||
::If the SRY gene determines gender then it influences a person's morphology more than pretty much any other gene (yes there are ] but these don't get passed on only half the time). So what I'm saying is it is reasonable the "selfishness" of this gene would be extremely influencial. As a consequence of a gene contributed by only one parent the child's morphology is vastly changed. | |||
::If a father has a son everything that makes that son male comes from the father. If a father has a daughter the gender characteristics are cause by both the mother and father. Therefore, a father wishing to pass on his genes would prefer sons as the sons will pass on his male characteristics to their children, daughters will not. ] (]) 19:01, 11 June 2009 (UTC) | |||
:::A father wishing to pass on his genes would prefer a daughter as the daughter will have more of his genes than a son. Being a male is not that important, really. ] (]) 19:13, 11 June 2009 (UTC) | |||
::::This is becoming a circular argument, as I said earlier it's not about the number of genes it's about the end result. Let's try this: do you agree that the gender of a child is determined by the genetic contribution of only the father? ] (]) 20:23, 11 June 2009 (UTC) | |||
:::::No one is arguing that the contribution of the SRY gene is unimportant in determining the gender. It is a critical switch between a male and female phenotype. However, you are incorrect in your assertion that "everything that makes that son male comes from the father". Have a look at the ] and ] articles and then tell me whether you still think that the mother does not contribute to the male phenotype in her sons. --- ] (]) 20:48, 11 June 2009 (UTC) | |||
::::::Androgen receptors are present in men and women; the information is interesting but it doesn't refute the fact that only the contributions of the father determine whether a male is born. The father is solely responsible for whether the switch is triggered and child becomes a boy or a girl. That's where the importance lies; all the genes that interact as a result of this trigger are still dependent on SRY in the first place. ] (]) 21:12, 11 June 2009 (UTC) | |||
:::::::I don't think anyone has denied this last statement of yours. What is your point? ] (]) 22:38, 11 June 2009 (UTC) | |||
:::::Besides, the genes themselves don't care about the phenotypical outcome as long as they get to be inthe next generation. That's what's meant by selfish gene. And all those genes on the X chromosome are selfish and want to be in the next generation and don't care that much wheather it is a male or a female. The SRY gene is outnumbered and, despite of what you said, I think that does matter. ] (]) 21:30, 11 June 2009 (UTC) | |||
1. In Misplaced Pages, the page ] is automatically redirected to our article ], ''which actually doesn't mention the term "relativistic length" at all''. '''I wonder if there is an accepted term for the concept of relativistic length'''. | |||
:Going back to the first principles of evolution, suppose a mutation occurs on the Y chromosome being passed on to a son. The son with the mutated Y chromosome has a 50% chance of passing it on to a child; he'll definitely pass it to sons and definitely not pass it to daughters. | |||
:Now suppose a mutation occurs on the X chromosome being passed on to a daughter. That daughter has a 50% chance of passing it on to a child; all her children receive an X from her, but only half will receive the mutated X. So both sons and daughters have a 50% chance of giving the mutation to their children. Being on the Y chromosome offers no advantage. --] (]) 03:22, 12 June 2009 (UTC) | |||
2. A similar qusestion arises, at to the concept of relativistic time: The page ], is automatically redirected to our article ], which prefers the abbreviated term "time dilation" (59 times) to the term "relativistic time dilation" (8 times only), and ''nowhere'' mentions the term "relativistic time" alone (i.e. without the third word "dilation") - although it does mention the term "proper time" for the shortest time. Further, this article doesn't even mention the term "dilated time" either. It does mention, though, another term: ], but regardless of time dilation in ''Special'' relativity. '''To sum up, I wonder what's the accepted term used for the dilated time (mainly is Special relativity): Is it "coordinate time"? "Relativistic time"?''' | |||
== How can you make black through mixing colors? == | |||
] (]) 09:32, 30 December 2024 (UTC) | |||
Hi all, | |||
:Are you reading these things as "contraction of relativistic length" etc.? It is "relativistic contraction of length" and "relativistic dilation of time". --] (]) 09:37, 30 December 2024 (UTC) | |||
If you had only ] available, would it be possible to mix them together in such a way to make perfect black? (We can assume hypothetically perfect primary colors.) If not, what colors are needed in order to produce perfect black? | |||
::When I wrote: {{tq|The page ] is automatically redirected to our article ] which...nowhere mentions the term "relativistic time" alone (i.e. without the third word "dilation")}}, I had already guessed that the term "dilation of relativistic time" (i.e, with the word "dilation" preceding the words "relativistic time") existed nowhere (at least in Misplaced Pages), and that this redirected page actually meant "relativistic dilation of time". The same is true for the redirected page "relativistic length contraction": I had already gussed it didn't mean "contraction of relativistic length", because (as I had already written): {{tq|the article ]...doesn't mention the term "relativistic length" at all}}. | |||
::Anyway, I'm still waiting for an answer to my original question: Are there accepted terms for the concepts, of relativistic length - as opposed to ], and of relativistic time - as opposed to ]? ] (]) 10:12, 30 December 2024 (UTC) | |||
:::A term that will be understood in the context of relativistic length contraction is ''relative length'' – that is, length relative to an observer.<sup></sup> --] 10:55, 31 December 2024 (UTC) | |||
::::Thank you. The middle source uses the term "comparative length", rather than "relative length". I couldn't open the third source. ] (]) 08:04, 1 January 2025 (UTC) | |||
:::::The text under the graph labelled '''Comparative length''' on page 20 of the middle source reads: | |||
::::::Graph of the relative length of a stationary rod on earth, as observed from the reference frame of a traveling rod of 100cm proper length. | |||
:::::A similar use of "relative length" can be seen on the preceding page. --] 10:23, 2 January 2025 (UTC) | |||
== What did Juan Maldacena say after "Geometry of" in this video? == | |||
Thanks! --Sam <span style="font-size: smaller;" class="autosigned">—Preceding ] comment added by ] (]) 13:17, 11 June 2009 (UTC)</span><!-- Template:UnsignedIP --> <!--Autosigned by SineBot--> | |||
I was watching this video ] and ] as they explore a wealth of developments connecting black holes, string theory etc, ] said something right after "'''Geometry of'''" Here is the spot: https://www.youtube.com/live/yNNXia9IrZs?si=G7S90UT4C8Bb-OnG&t=4484 What is that? ] (]) 20:46, 30 December 2024 (UTC) | |||
: It depends. Are we talking about Addition of Colors? (Like mixing colored light) Or are we talking about Subtraction of Colors? (Like mixing paint). Check out ] to learn the difference. But briefly, if you're subtracting colors, then yes, you can mix <s>red, blue and green</s>Yellow, Magenta and Cyan, to form black. But if you're adding colors, then mixing red,blue and green will form white. ] (]) 13:28, 11 June 2009 (UTC) | |||
:]. --] (]) 21:05, 30 December 2024 (UTC) | |||
::Thank you, its the ]'s accent which made me post here. ] (]) 21:18, 30 December 2024 (UTC) | |||
= December 31 = | |||
::<small>The three primary colors in subtractive mixing are yellow, magenta, and cyan, not red, blue and green. ] (]) 20:32, 11 June 2009 (UTC) </small> | |||
:::<small> Of course! I knew that. I was ... just testing. ] (]) 23:43, 11 June 2009 (UTC) </small> | |||
== Brightest spot of a discharge tube == | |||
:(ec) In theory, yes, see ]. In reality, you end up with some kind of dark mud colour because some light is still being reflected. This is the reason printers always use three colours plus black in full colour printing - the "mixed black" is just not good enough for quality documents. ] 13:30, 11 June 2009 (UTC) | |||
::Our article is also a little misleading, you might get a nice dark black as shown with subtractive mixing using ] but it won't happen with pigments as the article claims. I might just go edit that. ] 13:37, 11 June 2009 (UTC) | |||
] | |||
::: Some inkjet printers can produce a perfectly usable black with only the CMY pigments. ] (]) 14:03, 11 June 2009 (UTC) | |||
] | |||
What causes the discharge tubes to have their brightest spots at different positions? ] (]) 13:12, 31 December 2024 (UTC) | |||
: See also the pictures at ]. --] (]) 13:26, 31 December 2024 (UTC) | |||
:For additive mixing - mixing light - such as you do on a computer screen - then using zero amounts of the three primary colors gets you black. For subtractive mixing - paint, dyes, etc - you'd theoretically use the maximum amount of all of the primary colors. The problem with subtractive mixing is that firstly, the three primary colors that you'd ideally want are not perfectly manufacturable with available chemicals - and secondly that the means by which dyes, inks and paint pigments work means that they really cannot do a perfect job. ] (]) 14:32, 11 June 2009 (UTC) | |||
= January 1 = | |||
::I can mix a good subtractive black with clear pigments in acrylic paints. I seldom want flat black because it rarely occurs in nature, but I can mix it. I spent an hour learning how. Most of the time, however, I want black with an edge, a punch, and that means a red-black, a blue-black or whatever suits the painting. ] (]) 03:31, 12 June 2009 (UTC) | |||
== Two unit questions == | |||
== Is this person mentally challenged? == | |||
#Is there any metric unit whose ratio is not power of 10, and is divisible by 3? Is there any common use for things like "{{frac|2|3}} km", "{{frac|5|12}} kg", "{{frac|3|1|6}} m"? | |||
Someone online told me a few days ago that the solution to the world's problems was to "have a party for everyone." Now, obviously if you can't diagnosed OPs, you can't diagnose people. :-) But, is this a normal thing for an adult to think? (Okay, I'll admit they may just be saying they're an adult - but you'd think someone pretending to be an adult wouldn't be talking about magically bringing Mideast peace by having a party for everyone.) | |||
#Is a one-tenth of nautical mile (185.2 m) used in English-speaking countries? Is there a name for it? | |||
--] (]) 10:41, 1 January 2025 (UTC) | |||
:1 not that I know of (engineer who has worked with SI for 50 years) | |||
What psychological reason would a person have for believing that by jsut throwing a party and inviting everyone, that: A. the people will come; and, B. that they'll put aside so much hatred? I know that in some cases, ordinary citizens have come together peacefully, but that's not the same thing as everyone stopping it.] (]) 15:00, 11 June 2009 (UTC) | |||
:2 not that I know of (yacht's navigator for many years on and off) | |||
:Well it worked in south park with Timmy and the bloods and the crips. It would have to be one bitchin' party though. ] (]) 15:06, 11 June 2009 (UTC) | |||
:] (]) 11:35, 1 January 2025 (UTC) | |||
::In Finland, ''kaapelinmitta'' is 185.2 m. Is there an English equivalent? --] (]) 18:11, 1 January 2025 (UTC) | |||
:::]. --] (]) 18:26, 1 January 2025 (UTC) | |||
::::Good article. I was wrong ] (]) 22:26, 1 January 2025 (UTC) | |||
:Perhaps he was referring to a party in his mouth in which obviously everyone is invited. It's actual not a horrible idea; a world peace day celebration couldn't cause much harm. ] (]) 15:11, 11 June 2009 (UTC) | |||
:::The answer can be found by looking up '']'' on Wiktionary. --] 00:14, 2 January 2025 (UTC) | |||
== What is more physiological (for a right-hander) left-hand drive or right-hand drive? == | |||
:: Unless someone used it to cover their sneak attack. Then it would just make things worse. I think people make the mistake that all of the world leaders are rational, which may or may not be the case. ] (]) <span style="font-size: smaller;" class="autosigned">—Preceding ] comment added 15:36, 11 June 2009 (UTC).</span><!--Template:Undated--> <!--Autosigned by SineBot--> | |||
Has anyone determined whether it is better for a right-hander to have the left hand on the steering wheel and the right hand on the gear shift stick, or the other way round? Are there other tests of whether left-hand drive or right-hand drive is physiologically better (for a right-hander at least)? ] (]) 12:03, 1 January 2025 (UTC) | |||
:<small>Supplementary question: I've only driven right-hand-drive vehicles (being in the UK) where the light stalk is on the left of the steering column and the wiper & washer controls are (usually) on the right. On a l-h-drive vehicle, is this usually the same, or reversed? {The poster formerly known as 87.81.230.195} ] (]) 12:12, 2 January 2025 (UTC)</small> | |||
:::This sentiment also embodies the naive assumption that all wars, violence, and feuds are fundamentally "bad" for everybody, and that if we just agreed to stop having wars, violence, and feuds, ''everyone'' would be happier. Unfortunately, human history has shown us many times that wars are often beneficial to one or more responsible players. These players have no incentive to stop the war/violence/feud. Most often, they are able to separate themselves from the negative repercussions of conflict, either via ], effective defense, or some other method. They can then reap all the benefits while subjected to minimal harm, and are inclined to perpetuate the conflict indefinitely (until some strategic situational change). ] (]) 16:04, 11 June 2009 (UTC) | |||
::<small>Modern cars are designed for mass production in RH- and LH-drive versions with a minimum difference of parts. Steering columns with attached controls are therefore unchanged between versions. ] (]) 12:29, 2 January 2025 (UTC) | |||
:::In the UK nowadays, are cars still mostly manual transmission, or has automatic become the norm? ←] <sup>'']''</sup> ]→ 12:38, 2 January 2025 (UTC) | |||
::::In the UK, sales of new automatics have just recently overtaken manuals - so probably still more manuals than automatics on the road. ] (]) 14:37, 2 January 2025 (UTC)</small> | |||
:::::<small>This may be tied to the rise of EVs, since they have automatic transmissions by default. {The poster formerly known as 87.81.230.195} ] (]) 05:29, 3 January 2025 (UTC)</small> | |||
:::In Australia, we drive on the left, and the indicator and wiper stalks are the opposite way to the UK. Having moved back from the UK after 30 years, it took me a while to stop indicating with wipers. ] (]) 05:08, 3 January 2025 (UTC) | |||
::::This depends more on where the car came from I think. For European or American cars it tends to be in the UK direction. For Asian cars or I guess those odd Australian made cars which are out there, it tends to be in the other. See e.g. . The UK being a bigger market I think most manufacturers have come to follow the new UK norm for cars they intend to sell there although I suspect to some extent it's still true in the sense that I think most Asian car brands, at least assemble their cars in the EU or maybe the UK if they're destined for the UK (made a lot of sense pre-Brexit) . It sounds like the new UK norm is fairly recent perhaps arising in the 1980s-1990s after European manufacturers stopped bothering changing that part of the production for the reasons mentioned by Philvoids. As mentioned in one of the Reddit threads, the UK direction does make it difficult to adjust indicators while changing gear which seems a disadvantage which is fairly ironic considering the the UK has much more of a preference for manuals than many other RHD places with the other direction. ] (]) 04:31, 6 January 2025 (UTC) | |||
:::::<small><p>For further clarity, AFAICT, LHD vehicles generally have their indicators on the left and wipers on the right. As mentioned, assuming the gear stick is in the middle which AFAIK it is for most cars by now, this seems the better positioning especially on manual cars since you're much more likely to want to need to indicate while changing gear than you are going to want to adjust your wipers even in the rainy UK. The UK being LHT/RHD especially with their own manufactured cars tended to have the indicators on the right and wipers on the left in the more distant past so again the positions that made most sense. </p><p>While I don't have a source for this going by the history and comments, it sounds to me like what happened is European manufacturers who were primarily making LHD vehicles, with the UK and Ireland their main RHD markets but still small compared to the LHD market stopped bothering changing positions for RHD vehicles as a cost saving measure. So they began to put wipers on the right and indicators on the left even in their RHD vehicles no matter the disadvantage. I'm not so sure what the American manufacturers did or when and likewise the British but I think they were a fairly small part of the market by then and potentially even for them LHD was still a big part of their target market. </p><p>Meanwhile Asian manufacturers however still put their indicators on the right and wipers on the left in RHD vehicles, noting that Japan itself is LHT/RHD. I suspect Japanese manufacturers suspected, correctly, that it well worth the cost of making something else once they began to enter the LHD markets like the US, to help gain acceptance. And so they put the indicators on the left and wipers on the right for LHD vehicles even if they did the opposite in their own home market and continued forever more. Noting that the predominance of RHT/LHD means even for Japanese manufacturers it's generally likely to be their main target by now anyway. </p><p>Later I assume South Korea manufacturers and even later Chinese felt it worth any added cost to increase acceptance of their vehicles in LHT/RHD markets in Asia and Australia+NZ competing against Japanese vehicles which were like this. And this has largely continued even if it means they need to make two different versions of the steering column or whatever. It sounds like the European and American brands didn't bother but they were primarily luxury vehicles in such markets so it didn't matter so much. </p><p>This lead to an interesting case for the UK. For the Asian manufacturer, probably many of them were still making stuff which would allow them to keep putting the indicators on the right and wipers on the left for RHD vehicles as they were doing for other RHD markets mostly Asian. And even if they were assembling them in the EU, I suspect the added cost of needing to ship and keep the different components etc and any difference it made to the assembly line wasn't a big deal. </p><p>So some of did what they were doing for the Asian markets for vehicles destined for UK. If they weren't assembling in the EU, it made even more sense since this was likely what their existing RHD assembly line was doing. But overtime the UK basically adopted the opposite direction as the norm no matter the disadvantages to the extent consumers and vehicle enthusiast magazines etc were complaining about the "wrong" positions. So even Asian manufacturers ended up changing to the opposite for vehicles destined to the UK to keep them happy. So the arguably better position was abandoned even in cases where it wasn't much of a cost saving measure or might have been even adding costs. </p><p>] (]) 05:43, 6 January 2025 (UTC)</p></small> | |||
::I've driven different (automatic) left-hand-drive vehicles with the light stalk on each side, but left side has been more common. Perhaps because the right hand is more likely to be busy with the gear shift? (Even in the US, where automatic has been heavily dominant since before I learned to drive.) -- ] (]) 17:32, 2 January 2025 (UTC) | |||
:It's better for a right-hander to have both hands on the steering wheel regardless of where the gear lever is. See . I suspect the same goes for a left-hander. ] (]) 14:39, 2 January 2025 (UTC) | |||
::I suppose that the question is whether right-handers have an easier time operating the gear stick when changing gears in manual-transmission cars designed for left-hand traffic, with the steering wheel on the right (like in the UK) or right-hand traffic, with the steering wheel on the left (like in most of continental Europe). Obviously, drivers will use their hand at the side where the gear stick is, so if it is in the middle and the driver, behind the wheel, sits in the right front seat, they'll use their left hand, regardless of their handedness. But this may be more awkward for a rightie. Or not. | |||
::--] 16:30, 2 January 2025 (UTC) | |||
:::In my personal experience (more than 10 years driving on each side of the road, in all four combinations of car handedness and road handedness) the question which hand to use for shifting gears is fairly insignificant. Switching from one type of car to the other is a bit awkward though. —] (]) 18:33, 2 January 2025 (UTC) | |||
::::My first car, a ], had the gearstick on the left and the handbreak on the right, which was a bit of a juggle in traffic. ] (]) 19:13, 3 January 2025 (UTC) | |||
== Distinguishing a picture of a sunset from the picture of a sunrise? == | |||
:Attempting a serious response: People mature psychologically in different ways. Some people may have difficulty formulating a realistic ] and fail to appreciate the potential threat of coercing various hostile ] to attend a mass "social" gathering. However, people who '''voluntarily''' attend such a gathering would presumably share your friend's hope that we can all get along. | |||
Is there a way (if you don't know which way is west and which way is east in a particular location) to distinguish a picture of a sunset from the picture of a sunrise? ] (]) 12:08, 1 January 2025 (UTC) | |||
:Several political movements have attempted to overcome the inherent fractiousness of ], by setting a singular purpose for their followers. ] teaches that religion, culture, and ethnicity are secondary to the great historical class struggle for economic justice. ] teaches that money, sex and power are secondary to the holy injunction to live a life worthy of Heaven. ] teaches that autonomy and freedom of thought are among the highest virtues, and the individual actualizes their dreams by hard work and merit. ]s (benevolent or otherwise) demand that the subject peoples submit to the will of the sovereign. All these systems have inherent flaws because humans exhibit behaviour spanning from wonderful atruism to despicable evil. | |||
:Generally, no, but there are a few tricks that sometimes work. In dry sunny weather, there's more dust in the air at sunset (due to thermals) than at sunrise, making the sky around the sun redder at sunset. But in moist weather, mist has the same effect at sunrise. If the picture is good enough to see ], comparing the distribution of sunspots to the known distribution of that day (this is routinely monitored) tells you where the North Pole of the sun is. At sunset, the North Pole points somewhat to the right; at sunrise, to the left. If you see any ] or ] clouds in the picture, it was a sunset, as such clouds form during the day and disappear around sunset, but absence of such clouds doesn't mean the picture was taken at sunrise. A very large cumulonimbus may survive the night. ] clouds are often very large, expanding into ], in the evening, but are much smaller at dawn as there's more air traffic during the day than at night, making the upper troposphere more moist towards the end of the day. Cirrostratus also contributes to red sunsets and (to lesser extend, as there's only natural cirrostratus) red sunrises. ], ], flowers and flocks of birds may also give an indication. And of course human activity: the beach is busier at sunset than at sunrise. ] (]) 13:41, 1 January 2025 (UTC) | |||
:The only way we can all "just get along" is if/when a large enough proportion of the population '''decides themselves''' to do so, through their shared belief and values. Otherwise humanity is always going to be a troublesome collection of competing tribes. ~~ ] (]) 17:50, 11 June 2009 (UTC) | |||
::Supposing the photograph has high enough resolution to show ]s it can be helpful to know that the pattern of spots at sunrise is reversed left-right at sunset. ] (]) 13:21, 3 January 2025 (UTC) | |||
:::At the equinox, the disk of the Sun with its pattern of sunspots appears to rotate clockwise from sunrise to sunset by 180 degrees minus twice your latitude (taking north positive). At my place, that's 75 degrees. Other times of the year it's less; at the start and end of polar day and polar night, there's no rotation. Sunset and sunrise merge then. | |||
:::And I forgot to mention: cirrostratus clouds will turn red just after sunset or just before sunrise. At the exact moment of sunrise or sunset, they appear pretty white. ] (]) 17:06, 3 January 2025 (UTC) | |||
::::I differ: the same rotation is involved everywhere on Earth. If you stand on tiptoe at a N. or S. pole to take a picture of the Sun it is you who must pirouette 15 degrees per hour to keep facing the Sun. The Earth rotates you at this rate at all non-polar locations. If you stand within the arctic or antarctic circles, for parts of the year the 24-hour night or 24-hour daylight seem to prevent photographs of sunrise or sunset. However the terms "sunrise" and "sunset" can then be interpreted as times that are related to particular timezones which are generally assigned by longitude. In photographing the 24-hour Sun the equatorial rise and set times for your own longitude are significant elevation maxima worth mentioning even though the minimum elevation remains above the horizon. I maintain that the sunspot pattern observed from any location on Earth rotates 360 degrees per 24 hours and that "night", the darkness from sunset to sunrise, is when the Earth's bulk interrupts one's view of the rotation but not the rotation itself which is continuous. | |||
:::::Taking the Earth as reference frame, the Sun rotates around the Earth's spin axis. The observer rotates around his own vertical axis. The better both axes are aligned, the smaller the wobble of the Sun. In the northern hemisphere, it rotates clockwise from about 6 till 18 by 180 degrees minus twice your latitude and counterclockwise at night, in the southern hemisphere it's the opposite. Try a planetarium program if you want to see it. ] shows some sunspots, does things right and is free and open source. ] (]) 10:27, 5 January 2025 (UTC) | |||
:::::]We deprecate the obselete ] and suggest Misplaced Pages references that are free and just one click away (no extra planetarium software needed). The axes of rotation of the Sun and Earth have never in millions of years aligned: the ] is the orbital plane of Earth around the Sun and Earth currently has an ] of about 23.44° without "wobbling" enough from this to concern us here. ] (]) 14:56, 5 January 2025 (UTC) | |||
::::::This isn't my field but sunspots aside, if you know the location and date, I assume the appearance of other astronomical objects like the moon or rarely another star probably Venus, in the photograph should be enough to work out if it's a sunset or sunrise. That said, to some extent by taking into account other details gathered from elsewhere's I wonder if we're going beyond the question. I mean even if you don't personally know which is east or west at the time, if you can see other stuff and you know the location or the stuff you can see is distinctive enough it can be worked out, you can also work out if it's sunset or sunrise just by working out if it's east or west that way. ] (]) 03:54, 6 January 2025 (UTC) | |||
:::::In my experience (Southern England) they tend to be pinker at dawn and oranger(!) at dusk. {The poster formerly known as 87.81.230.195} ] (]) 03:23, 4 January 2025 (UTC) | |||
::::::Pink clouds must result from blending of reddish clouds with the blue sky behind. There's actually more air between the observer and the clouds than behind the clouds, but for that nearby air the sun is below the horizon. ] (]) 10:27, 5 January 2025 (UTC) | |||
::::The questioner asks for interpretation of a single picture. It is beside the point that more would be revealed by a picture sequence such as of changing cloud colours. ] (]) 12:41, 4 January 2025 (UTC) | |||
:Recalling Leonard Maltin's comment about the ''Green Berets'' movie, which was filmed in the American state of Georgia: "Don't miss the closing scene, where the sun sets in the east!" ←] <sup>'']''</sup> ]→ 22:37, 5 January 2025 (UTC) | |||
::Which you can only tell if you know which way is east in the image. Maltin, or his writer, appears to have assumed that Vietnam has a seacoast only on the east, which is wrong. --] (]) 03:46, 6 January 2025 (UTC) | |||
:::Georgia has only an eastern seacoast. ←] <sup>'']''</sup> ]→ 10:31, 6 January 2025 (UTC) | |||
::::<small>] ] (]) 14:18, 6 January 2025 (UTC)</small> | |||
::::So what. Bugs? The claim is about the setting, not the filming location. --] (]) 07:30, 7 January 2025 (UTC) | |||
:::::But as it was filmed in (The US State of) Georgia, it must actually show a sunrise, regardless of what the story line says – how do you know that wasn't what Maltin actually meant? {The poster formerly known as 87.81.230.195} ] (]) 10:35, 7 January 2025 (UTC) | |||
:::::::*Because things filmed for movies often are not actually what they are shown as being, so that wouldn't be interesting and Maltin's guide wouldn't waste space on it. If what they show it as — for example, in '']'' — is wrong or impossible, that could be interesting. --] (]) 17:43, 8 January 2025 (UTC) | |||
::::::I assume (not having seen the film) that, <u>in the story line</u> of '']'' , the closing scene takes place in the late afternoon, which means it shows a sunset. The plot section of our article on the film places the closing scene at or near ], which is on the east coast of Vietnam. This means that Maltin did not make an unwarranted assumption; he was just seeking an excuse to bash the film. --] 13:55, 7 January 2025 (UTC) | |||
:::::::I've seen ] and confirm that the closing scene with End title is an offshore sunset. ] (]) 20:12, 7 January 2025 (UTC) | |||
= January 6 = | |||
The OP friend's call to "have a party for everyone" has been interpreted as "throw a party for everyone" which is difficult to do. However if the caller meant "have a '''political party''' for everyone" they may be postulating that ] would solve the world's problems better without political parties. Far from implying mental disease, that is a critical viewpoint that merits consideration. It supports the idea of ] whereby citizens vote on issues directly without intermediate representatives or parties. Examples of direct democracies are seen in ] in some Swiss ] and in many countries an occasional ] (plebiscite) that is held to resolve a specific issue. There are obvious practical difficulties with controlling government this way. However the speaker may have had a more ominous idea that only one political party should be ''permitted'' for everyone i.e. a ] such as a ] or a form of ]. All these are political standpoints that should be open to debate, though inapropriate for this Science desk, but there is ] for equating dissident political opinion with mental disease. ] (]) 20:26, 11 June 2009 (UTC) | |||
== Does the energy belonging to an electromagnetic field, also belong (or is considered to belong) to the space carrying that field? == | |||
::I think the one that works is not "have a party for everyone" but is "everyone has a party together and likes it" but that won't feed people who are hungry :( ~ ].].] 20:28, 11 June 2009 (UTC) | |||
] (]) 18:41, 6 January 2025 (UTC) | |||
::: Well I would assume this party has snacks and drinks, but yeah long term, they still have no food. And on a more serious note, you would have a very difficult time hosting a party for everyone on earth not only logistically, but also without gravely insulting at least one group. That means, your catering can have no alchohol or you will insult the Muslims, no pork products for the same reason. No beef because of Hindus. In fact, better go no meat at all for the vegans. Now you upset just about everyone else who was hoping for some beer and pizza. My point is that if you can't even get the catering to work out for all these groups, how do you expect them to work more serious issues out? I do not know this person and can not tell if they were serious, but they appear to be hopelessly idealistic. ] (]) 20:50, 11 June 2009 (UTC) | |||
:::: The best part about throwing an everybody-in-the-world party is that there are no neighbors to complain about the noise. ] (]) 21:02, 11 June 2009 (UTC) | |||
A fair amount of the world doesn't drink, would this be a dry party? ] (]) 21:17, 11 June 2009 (UTC) | |||
:It would be unusual to express the situation in such terms. Since the notion of energy "belonging to" some entity is not itself a physical concept – any practical approach to energy bookkeeping that satisfies the law of conservation of energy will do – this cannot be said to be wrong. It is, however, (IMO) not helpful. Does an apple belong to the space it occupies? Or does that space belong to the apple? --] 23:37, 6 January 2025 (UTC) | |||
::First, I let you replace the notion of energy "belonging to" some entity, by the notion of energy "attributed to" some entity, or by the notion of energy "carried by" some entity, and the like. In other words, I'm only asking about the abstract relation (no matter what words we use to express it), between the energy and the ''space'' carrying the electromagnetic field, rather than about the specific term "belong to". | |||
::Second, I'm only asking about ''what the common usage is'', rather than about whether such a usage is wrong or helpful. | |||
::The question is actually as follows: Since it's ''accepted'' to attribute energy to an electromagnetic field, is it also ''accepted'' to attribute energy to the ''space'' carrying that field? | |||
::So, is your first sentence a negative answer, also to my question when put in the clearer way I've just put it? ] (]) 03:28, 7 January 2025 (UTC) | |||
:::The answer remains the same. It would be a highly unusual use of language to "attribute" electromagnetic energy to a volume of space, in quite the same way as it would be strange to "attribute" the mass of an apple to the space the apple occupies. But as long as an author can define what they mean by this (and that meaning is consistent with the laws of physics), it is not wrong. --] 13:21, 7 January 2025 (UTC) | |||
::::An electromagnetic field that we may ] conceive to have the form of a massless photon has, like the aforementioned apple (a biological mass) its own unique history, that being a finite path in ]. I reject apparent effort to give spacetime any kind of identity capable of owning, or even anticipating owning or remembering having owned anything at all. Concepts of owning]], attributing] or whatever synonymous wordplay one chooses all assume identification that can never be attached to the spacial <i>location</i> of an em field. The energy of the photon is fully accounted for, usually as heat at its destination, when it is absorbed and no lasting trace remains anywhere. I am less patient than Lambian in my reaction to this OP who under guise of interest in surveying "what is commonly accepted" returns in pursuit of debate by patronisingly "allowing" us to reword his question in abstract "words that don't matter" to make it purportedly clearer and worth responders' time. ] (]) 14:55, 7 January 2025 (UTC) | |||
::::Thank you Lambiam for your full answer. I always appreciate your replies, as well as your assuming good faith, always. ] (]) 15:08, 7 January 2025 (UTC) | |||
Back to te original question. I doubt the person was serious. However, taking the question at face value, and assuming they were serious, I would have to say that, yes, this person is perfectly sane, but most likely wrong. There are many mature, rationale, successful (have an apartment and car) adults who would do nothing but party if given the chance. Now how many of those people are in politics? :) | |||
= January 8 = | |||
On a side note, war is not a bad thing. War distracts countries from developing dangerous technologies. War boosts the economy. War keeps the population under control. War is an outlet for aggression. Without war, society would collapse. Now bring on the insults and rebuttals, because I know they are coming.]rew ] ] 03:44, 12 June 2009 (UTC) | |||
== Australian for double-decked bridge? == | |||
: Rebuttal... Wars are excellent routes for technological advances. No one cares about the money you are spending on it, and you have a very strong motivation to develop new stuff to get the bad guys. ] (]) 13:19, 12 June 2009 (UTC) | |||
On a ] (or on any other kind of map, like a track diagram), what symbol represents a ] which is directly above and ] with another railroad which is either on a lower deck of the same bridge, or else is ] (as in, for example, a narrow-gauge line on a ] above a standard-gauge one)? ] (]) 06:35, 8 January 2025 (UTC) | |||
:::God forgive me but you pluck ones out to represent all of the differing opinions/religions etc. but you make sure 100% they will not kill or even badly injure each other ever. You put them all on a spacecraft like the Arthur C Clarke Rama with all they need to sustain themselves or party and tell them they are going to a far away star. Then just throw them into orbit and watch them like Big Brother. You have picked them all out correctly so none dominates, none suffers too severe depressions, competitiveness is mild and the environment gets adequate care (which means excellent care really). You sit back and watch them all and they instinctively produce the solution to human differences. Maybe thats what the Earth is already. ~ ].].] 15:33, 12 June 2009 (UTC) | |||
:Our ] article only lists two multi-level bridges in Australia, neither of which seem to fit your criteria. ] (]) 19:16, 8 January 2025 (UTC) | |||
::: How do you select them so that you know that they will never kill or intentionally injure each other? I suspect even the Amish (about as pacifist a group I have ever seen) probably have the rare murder. ] (]) 16:37, 12 June 2009 (UTC) | |||
::: WW2 was a good motivator for scientific progress, but is that typical of all wars? WW2 was a special case in many ways. For example, what technological advances has the civil war in Darfur produced? ] (]) 18:46, 12 June 2009 (UTC) | |||
:::: You mean Darfur Sudan??? Probably because everyone else did the technological advances that they are using in their war 20+ years ago. ] (]) 19:53, 12 June 2009 (UTC) | |||
:::::Ah! selecting them is the trick, I couldn't let you in on that. ~ ].].] 20:52, 12 June 2009 (UTC) | |||
Hey, doesn't this discussion belong on the Humanities desk instead? | |||
] (]) 03:47, 14 June 2009 (UTC) | |||
:Probably a combo of science and humanities. Anyway my comment on distracting countries from developing dangerous tech was a little misleading. Example: the A bomb would have been completed a lot sooner if not for WW2. The war diverted valuable funding away from the manhatten project.]rew ] ] 03:54, 14 June 2009 (UTC) | |||
= June 12 = | |||
== Cancer in Whales == | |||
I was wondering why whales don't die early from cancer but in fact can be very long lived and as usual have found it is a question other people have asked before and actually it's called Peto's Paradox. I haven't seen any statistics on it though. Do people study of whales that are caught to determine if they have tumours? | |||
:Can you explain why would you expect them do die early from cancer? ] (]) 01:26, 12 June 2009 (UTC) | |||
:: recent article from LiveScience may be relavent. ~<font color="blue">]]]</font><sup>(]]])</sup> 01:38, 12 June 2009 (UTC) | |||
:::And silly me. I was thinking with all the coal mining going on there, there was bound to be higher rates of lung cancer. <small>OK, that was the worst joke EVER. I didn't even laugh at that.</small>--].].] 03:22, 12 June 2009 (UTC) | |||
::::It took me a while to get it, but when I did I thought it was pretty good...]rew ] ] 03:46, 12 June 2009 (UTC) | |||
:As to the why, I was reading about ]s and how they can live over 200 years and are 50 tons in weight. If one in eight of people die of cancer then even if we ignore the extra time a cancer has to grow but each person weight bit of the whale has that chance of a malignant cancer then overall their chance of escaping it would be something like (1 - 1/8) to the power of (50*2000/200) which google calculator tells me is about 10<sup>-29</sup>, i.e. they should all die of cancer and it's a wonder they live so long. By the way that's very interesting about chimps having a much lower rate. ] (]) 08:36, 12 June 2009 (UTC) | |||
::I guess, more properly stated, my question really is why would anybody expect the whale cancer rate per cell to be the same as a human cancer rate per cell? I don't see why it should be. In fact I think it should be expected to be a much slower rate given that a huge animal like that is necessarily going to have a much slower methabolic rate per cell. ] (]) 13:10, 12 June 2009 (UTC) | |||
::Per Dauto's remark, the assumption of a uniform risk of malignant transformation per unit body weight does not bear scrutiny. Even within the human body, different tissues (and, for that matter, different cell types within those tissues) have vastly different probabilities of becoming cancers. Malignant tumours derived from fat cells (]s and their ilk) are exceedingly rare, whereas cancers of the mucosal lining of the colon and rectum (]) are depressingly common. While one should be cautious about carrying these assumptions across species, it is likely that all that whale ] – accounting for up to half the mass of the bowhead whale – is resistant to malignant transformation. ](]) 14:12, 12 June 2009 (UTC) | |||
:::As to the rate per cell the whale lives far longer so that should offset its slower metabolic rate, thats why I didn't put in a factor for their longer life. Also since the cells divide many more times there's more opportunity for them to go wrong I'd have thought even in normal growth. As to the different tissues the whales have the same tissues so corresponding organs can be compared, they have colons and rectums too only far far larger. ] (]) 14:45, 12 June 2009 (UTC) | |||
:Speculation: high metabolic rate + relatively low volume of cells = high possibility that for humans, cancer is going to kill you. Whales are low rate and high volume, even if one had cancer, would it become large enough to kill it? More interesting as Dmcq points are are high rate, low-volume animals that don't have cancer problems. --] (]) 15:40, 12 June 2009 (UTC) | |||
:I don't see that the size makes much difference once a cancer has gone malignant. It'll spread and multiply and the only difference the victim's size makes is that it'll take a little bit longer to kill a bigger one. | |||
:Going backwards from whales to humans I get that if humans had an equivalent rate then death from cancer would have to be about 0.2% or less - which sounds much more reasonable and attainable by evolution than the 10<sup>-29</sup> chance of surviving for whales I got the other way round. It still means whales must have some very good anti-cancer protection. I would have thought also it implies any ] for whales would run much slower than expected for smaller mammals which mightn't be too hard to check. ] (]) 17:52, 12 June 2009 (UTC) | |||
::Well, Bovines are very resistant to all kinds of cancer. Whales are much closer to cattle (both are ]) than to humans. This does not mean that they have the same defenses, but it does make it at least plausible that whales have good cancer resistance. --] (]) 22:25, 12 June 2009 (UTC) | |||
:::Where did you get that cows were resistant to cancer? I didn't find statistics but a web search seemed to show that cancer in cows was quite common and it having gone malignant was a common cause for condemning meat. And it's not as though they have long lives. ] (]) 09:43, 13 June 2009 (UTC) | |||
::::I got it from the Science Magazine Podcast from April 24th (first interview, on the sequencing of the cattle genome - "cattle rarely develop spontaneous cancers and almost never auto-immune diseases") - about 7'47" into the program. ,. Sorry, not much more there, and I cannot make out the name of the researcher. --] (]) 10:16, 13 June 2009 (UTC) | |||
:::::I couldn't find a podcast on that date but it is a veyr interesting site. Seemingly people with Down's syndrome only get half the rate of cancer and primates in general get only a tenth of the cancer of humans. The authors seem to think our cancer protection has been compromised in the interest of growing a bigger brain. The primate rate is only ten times as much as I was calculating a whale had so well within the reach of whale evolution I'd have thought considering it isn't anywhere near so important for primates. So I consider the question as probably resolved. Cancer rates can be very variable and human rates are particularly bad considering our size and lifespan. ] (]) 12:24, 13 June 2009 (UTC) | |||
::::::Sorry about the link - I mixed up the Science and the Nature Podcast sites (I had to check both to find the Podcast again). The Science Archive page is , but Misplaced Pages does not render that as a clickable link. The mp3 link above should work. --] (]) 13:19, 13 June 2009 (UTC) | |||
:::::::Thanks very much for that, another good site for me to bookmark. I'll try and follow it up. ] (]) 12:00, 15 June 2009 (UTC) | |||
== Tidally lock == | |||
] said Europa, Io is tidally lock from Jupiter. is Titan tidally lock from Saturn? Does that mean Europa is moving further away from Jupiter? Is Titan moving away from Saturn? Pluto is also tidally lock with Charon. Does that mean eventually their moon will escape away from planet, until the moon escapes and become a own planet. Even the source isn't too clear.--] (]) 04:01, 12 June 2009 (UTC) | |||
:See ]. We do have an article on this... --].].] 04:19, 12 June 2009 (UTC) | |||
:On ] they only gave lists of planet/moon in locking. But they didn't say if moon is moving away or closer to planet. Which ratio means moon s moving closer to planet is 3:2 or 2:3?--] (]) 04:30, 12 June 2009 (UTC) | |||
::The ratios have nothing to do with the movement closer to and farther from the respective planets; the ratios have to do with the nature of the tidal lock. The ratio 3:2 means that the object makes three rotations per two orbits; 2:3 would mean two rotations per three orbits. As far as moving away from or towards the planet, you would have to know whether or not the moon's rotational speed is getting faster or slower as a result of the tidal lock. If the moon had to slow down to become locked, then, by conservation of angular momentum, it will be move FASTER in its orbit, thus drifting away from its planet. If it had to speed up its rotation, then it will have to slow down its orbit, and will drift towards its planet. This is all explained in the article. --].].] 05:28, 12 June 2009 (UTC) | |||
:::The article ] explains in more detail about the drifting away from a planet by a moon as the result of Tidal locking. --].].] 05:31, 12 June 2009 (UTC) | |||
:Jayron's answer is slightly imprecise but he pointed to the article (]) that explains all that in detail. To answer the OP's questions: Yes, Europa is moving away from Jupiter but not because it is tidally locked. It does so because it's orbit around Jupiter is prograde with a period longer than Jupiter's rotational period. samething is true for Titan. Triton, on the other hand has a retrograde orbit and is therefore moving closer to Neptune. Charon's orbit is stable because Pluto itself is also tidally locked. ] (]) 06:01, 12 June 2009 (UTC) | |||
== Question about polish people == | |||
Do Poles have yellow skin like that of a chinaman? They appear to, despite being otherwise 'white' in appearance.--] (]) 10:50, 12 June 2009 (UTC) | |||
:There's a picture of some at the start of the ] article. I don't see what you're seeing. Perhaps you have an old picture that has gone a bit yellow? ] (]) 12:49, 12 June 2009 (UTC) | |||
::No, I saw a guy today who was obviously Polish/Slavic and he looked almost exactly the same as white British except with a yellow tone to his skin that white British people generally lack.--] (]) 13:11, 12 June 2009 (UTC) | |||
:::No, I don't. In fact, people frequently remark about how tan I am, but maybe I'm the exception to the rule. ] (]) 13:14, 12 June 2009 (UTC) | |||
::::Not sure what you are referring to. Most Poles are ], and so share similar characteristics to other Slavs, such as Russians or Ukranians. However, Poland is surround by nations of different ethnicities, so there is bound to be a wide variation in appearances as people intermarry. Consider that the ] of Hungary and the ] are both ] peoples originally from Central Asia, while the Germans likely originated on the Baltic shores of Scandanavia. The fact is there is far more variance than assumed in an "ethnic" group, and such definitions are fluid and hard to nail down. What makes ] French and ] Peruvian and ] Mexican-American is not just genetic lineage, but also environment. A person is Polish because they live in Poland, even if all eight of their great grandparents came from other countries... --].].] 13:25, 12 June 2009 (UTC) | |||
::::Discussing peoples in Europe is particularly dicey because they don't seem to have stayed put for any considerable length of time. IMHO quite a few Polish people have a pasty to rosy complexion. Compare Images Voelkerwanderungkarte.png, Karte völkerwanderung.jpg, Invasions of the Roman Empire 1.png] (]) 15:42, 12 June 2009 (UTC) | |||
:I just had a look at the corresponding pictures in the ] and ] articles. Comparing them against each other there is an overall slight difference in the shape of the heads I think but otherwise nothing at all obvious I think. Have you seen a lot of people from Poland? it doesn't sound like it if you're talking about one person, and you sure they were from Poland rather than it being obvious somehow? After all it's quite possible for individuals to have a yellower skin either from ancestry or kidney disease or a tan or there's just a great variation amongst people. Some of those British or Polish people in the pictures could be interchanged quite easily without anyone noticing I think. ] (]) 14:30, 12 June 2009 (UTC) | |||
:Troll. ] (]) 15:27, 12 June 2009 (UTC) | |||
::If you are referring to my blunder a minute ago: Nope just dusty old idiot nor knowing how to use a gallery. :-(] (]) 15:50, 12 June 2009 (UTC) | |||
::I've seen plenty of yellow looking British and I didn't think they were Chinese. Heavy drinkers. The Poles come over here and bang they are drinking around the clock (sometimes) you too would be gone yellow. Some of that yellow is natural anyway even if you were pure black. You think is a yellow colour but you also think that the best way to pronounce Belgique is Belgi-um. If you look at those and still see yellow, go to the fourth row down, compare the elderly orient-asian man with the elderly caucasian man. There is plenty of yellow in the skin colour but it is typical. Yellow/brown/pink (white man). You are just a bit of a snob, sorry. Don't worry about it it's good for you. ~ ].].] 15:56, 12 June 2009 (UTC) | |||
Since nobody has yet openly stated it, the original poster should be aware of a few things: | |||
*This sort of comparative racial ] is widely discredited by modern scientific analysis. (As mentioned above, mass migrations and population diffusion are so prevalent that they render the 19th-century ethnic archetypes wholly inaccurate). | |||
*Cultural definitions are more relevant than biological distinctions. Take a look at ] and ]. Most ] do not use skin pigment as a primary indicator of cultural identity. | |||
*The use of the term ] may be construed as pejorative (offensive) in most contexts. Our article discusses the debate surrounding use of this term. | |||
*The lumping of skin-color and a generally offensive term suggest that the question is not asked in good faith. | |||
Our general policy is to ] on your part - possibly, this original poster is not aware of the implications of such a question - and in deference to the possibility that English is not your first language, or you are unfamiliar with cultural norms, I have posted this response as such. However, racially offensive questions are not very well received. While we don't censor such questions, because we value ], I think this question is inappropriate and unscientific. If you have a specific scientific question about ethnic or cultural identity; or if you have a specific question about human skin pigments, you should rephrase your question. ] (]) 18:00, 12 June 2009 (UTC) | |||
::That is correct; the OP is a troll, and everyone who has responded, including myself, has been successfully trolled. ] (]) 22:00, 12 June 2009 (UTC) | |||
:Out of curiousity, are there visible differences between Koreans, Chinese and Japanese? IOW, if you see an Asian person, can you tell which country they are from? For example, can you tell that ] from ] really is Korean? ] (]) 18:18, 12 June 2009 (UTC) | |||
:I see nothing racially offensive about the content of the question though I know some people treat people of other races badly for no other good reason than their color. Personally I'm prejudiced in that I have liked both the Poles and Chinese I have come across, it's my negative prejudices I have to be a bit more careful about. And by the way yes I can tell Koreans Chinese and Japanese apart quite easily normally. ] (]) 18:32, 12 June 2009 (UTC) | |||
::Well, Jin's name is very Korean, that kind of gives it away. Like guessing the nationality of man named Sean O'Grady. ] (]) 19:02, 12 June 2009 (UTC) | |||
::really? I have asked this question of numerous japanese and Chinese people (and one mongolian) and they all said they could not tell the difference between Chinese and Japanese people until they heard a person speak (or only based on cues such as clothing). Don't many people depend on this fact? Spies, Korean-born-Japanese-pop-stars etc - if there are obvious visible differences, then the vast majority of people seem to be missing them. But then i am pretty sure that no English person could really identify a Pole under controlled conditions - people think they can because of subconcious social cues.]] 19:07, 12 June 2009 (UTC) | |||
::Well there are lots of different types of Chinese people so you get all sorts but I must admit I'm very surprised. My first language was Chinese though I'm not Chinese myself so that probably helps with seeing them as different. ] (]) 19:22, 12 June 2009 (UTC) | |||
::There's a test at . I didn't do as well as I though I would and seemingly lots of nationals from those countries do worse. ] (]) 20:44, 12 June 2009 (UTC) | |||
: I've read that carotene-based tanning products are popular in parts of Europe. That can give an unusual cast to someone's skin color. ] (]) 18:40, 12 June 2009 (UTC) | |||
<small>A bit late for ] but OP blocked. See ]. ] (]) 22:26, 12 June 2009 (UTC)</small> | |||
== tennis == | |||
What is a "winner" in a tennis game?] (]) 11:04, 12 June 2009 (UTC) | |||
: This was answered on the Miscellaneous desk. Please don't post the same question on multiple desks. ] (]) 11:20, 12 June 2009 (UTC) | |||
== Adolescent development == | |||
http://aces.nmsu.edu/pubs/_f/f-122.pdf Reading this it seems that late adolescents (17-19) are pretty much adults, they have empathy for others, have a clear identity and are able to think logically etc. So what factors still make them adolescents from a scientific point of view. ] (]) 11:43, 12 June 2009 (UTC) | |||
:From a biological point of view, you are adult since puberty. Thinking logically, having an identity or empathy are not signs that you are an adult, not matter how desirable these characteristics are.--] ] 12:42, 12 June 2009 (UTC) | |||
::Psychologically, such character traits may be used to distinguish adolescents and adults (depending on which theories are believed), which is called "psychological age". Cf. "chronological age", "biological age" and "social age". Chronological age is the most simple to detirmine, as one just counts from birth, but may not always be the most useful. Biological age has useful developmental markers such as puberty, but these may not correspond to social age - is a sexually functional 12 year old an adult? The answer is always culturally dependant. A 25 year old man could have the psychologically adaptive capabilities of a child, and his adult status may depend upon situations (eg. he is adult enough for sex, but all his money is stored in a trust fund controlled by others). So the scientific answer is "it depends on which science, and why the age is needed".]] 13:15, 12 June 2009 (UTC) | |||
::(EC with yobmod)However, from a sociological point of view, what makes one person capable of taking on adult responsibilities varies greatly from society to society, and people will tend to act as they are expected; thus when a society expects a 14-year old to be an adult, one will often find a 16-year old having adult-like psychology. When another society places the age at 18, they will find most 16-year olds to have child-like psychology. And the biological definition of adulthood is not a bright-line. Puberty is a process, and I would venture that it is the end of puberty, and not the start, that is a better definition of full adulthood, but reasonable people may disagree on when that occurs. --].].] 13:17, 12 June 2009 (UTC) | |||
:::Jepp - i didn't go into social age, but the textbook i am getting this from distinguishes that from psychological age. Social age means taking on responsibilites associated with a certain age, whereas psychological age is detirmined by "adaptive behavioural strategies". I don't think changing the social role necessarily changes the psychological age - teenage mother's need extra support as their social age is far advanced while their pschological age is not (and to some extent is dependant on biological age).]] 13:29, 12 June 2009 (UTC) | |||
(outdent)One hugely influential psych theory that differentiates between adolescenthood, young adulthood, middle adulthood etc is ]. And biological changes associated with growth continue much past puberty - chest hair growth for example may not have even started by age 19.]] 13:29, 12 June 2009 (UTC) | |||
There is a lot of evidence that brain development is not complete at age 18 - particularly the areas relating to self-restraint and risk-taking. Some studies show that full maturity does not arrive until perhaps age 25: | |||
* http://www.dartmouth.edu/~news/releases/2006/02/06.html | |||
* http://www.washingtonpost.com/wp-dyn/articles/A52687-2005Jan31.html | |||
* http://www.youthadvocacyproject.org/pdfs/Brain%20Annotated%20Bibliography.pdf (Loads more links in here) | |||
But we start to get into a fuzzy argument here - after all, people even later in life (in their 40's and 50's) start to change mental recall strategies from raw memory (which begins to fade) to using intelligence/logic-based strategies (which continues to strengthen). Should we argue that "brain development" continues into your 40's and 50's and declare all 30 to 40 year olds "under age" for some activities demanding cold, hard logic? Surely not?! But it's also arguable that humans evolved in a situation where they'd mostly be dead by age 25 (average longevity in the bronze age was 18 years!) - and even in ancient Rome, Greece and medieval europe 25 was about the average life-expectancy, so if brain development is still happening at age 25 - should we not consider 18 year-olds to be the "normal adults" (with their high risk-taking and poor self-restraint being considered "normal") and the 30+ year olds to be "post-adult" and incapable of considering "normal" degrees of risk? It's just a matter of terminology in the end. What we should perhaps be asking is whether it makes sense to impose limits on 17 to 19 year-olds because of this risk-taking difference. Limiting alcohol use and access to fast, dangerous machines might make sense even if we decided they were to be '''called''' "adult" because a "normal" level of risk-taking is still too risky when the stakes are that high. ] (]) 16:20, 12 June 2009 (UTC) | |||
Steve, although the average life expectancy in those times was 25 years or less, this was mostly a result of the large numbers of children born who did not make it to adulthood. A lot of times, if a person got past that first part, they would often live 50+ years. ] (]) 16:33, 12 June 2009 (UTC) | |||
:As mentioned, ] is a terribly misleading statistic, ''especially'' if the distribution of age at death is heavily ] (as is the case when infant mortality is statistically significant). ] (]) 17:31, 12 June 2009 (UTC) | |||
== Cutting Limes == | |||
Why is it when I cut limes, my hands are never sticky? Actually, when I cut limes sometimes I don't wash my hands because they smell nice afterwards? Is it the low sugar content? If so, what type of sugar? --] (]) 18:59, 12 June 2009 (UTC) | |||
::See ] the solvent action is mentioned in ]. ] (]) 20:49, 12 June 2009 (UTC) | |||
*To answer your question, when you cut out ], ] or ] your knife and your hands will never be sitcky, because it is not made of oils such as meat, chickens, or barbeques. When you wash dishes or hands with citrus fruits, watermelons, apples, or grapes all you have to do is rinse with water, but you don't have to clean it with your soap.--] (]) 22:20, 12 June 2009 (UTC) | |||
:May I ask a follow-up question, regarding the washing '''of''' fruit? It's common knowledge that one should wash, say an apple or grapefruit before eating, even though you don't necessarily eat the skin of the grapefruit - but my girlfriend has a tendency to wash an apple with washing-up liquid before eating it - a little drop on the sponge, wipe fruit, rinse fruit thoroughly. I find it awful. Is this practiced/common/uncommon/unspeakable? --] <small>(])</small> 06:40, 13 June 2009 (UTC) | |||
::Fruit gets washed mostly to get pesticide residues and waxes (the "make the fruit look pretty on display at the store stuff"). ] can contain lots of chemicals and you can't know how they might react with those you wish to get rid of. In addition those chemicals only get tested for irritating skin, not for what they do if the get ingested. In case your friend doesn't like the results she gets with plain water and a brush she might try adding a bit of ]. It's safe to eat (for all but a very few people with certain medical problems) and if nothing else has a slight ] effect. A study (sorry can't get at it) has found that vegetable washes they advertise aren't any more effective than plain water and a brush. ] (]) 07:09, 13 June 2009 (UTC) | |||
:::Thanks loads, 71.236. Cheers, ] <small>(])</small> 20:37, 13 June 2009 (UTC) | |||
:::One has to wonder: if residue from dishwashing soap is harmful to ingest, what about the residue left on washed plates, bowls, and silverware and subsequently transferred to the food served on them? -- ] (]) 21:02, 13 June 2009 (UTC) | |||
::::Here's a summary of the study I couldn't get at. They even did study dishwashing liquid which I hadn't remembered. As you can see it didn't show any beneficial effect. They didn't study residues from it though. I think there's a study on that out there somewhere, but the one I'm thinking of might be outdated by now. Rinsing your dishes after washing is a good idea. --] (]) 21:55, 13 June 2009 (UTC) | |||
== warm "blooded" plants == | |||
In his speculations about the possibility of the most ultimate spread of life into space in ], Freeman Dyson discussed the advantages of warmbloodedness and mused on the fact that plants have never evolved this trait. What conceivable advantages for plants could such a trait have? --] (]) 22:46, 12 June 2009 (UTC) | |||
:Plants have evolved other safeguards against temperature changes besides "warmbloodedness". The ability to maintain a constant temperature, aka ] is a fantastically wasteful process. You basically are eating all day just to keep your temperature up. There are certainly advantages to it, but seeing as plants evolved other systems to deal with the ups and downs of the external temperature, it doesn't seem like there was much need for them to evolve this trait, given the obvious disadvantages that come along with it. --].].] 23:12, 12 June 2009 (UTC) | |||
:I do believe it is lotus plants that elevate their temperature above the night-time surroundings. That to me would qualify as "warm-blooded" and it does convey an evolutionary advantage. I may need a few minutes to get the links though. (Especially since the 7th game of the ] final series starts in a half-hour) ] (]) 23:24, 12 June 2009 (UTC) | |||
::Whew, just in time. It is "Thermoregulating lotus flowers", R. Seymour & P. Schultze-Motel, Nature 383, 305 (26 September 1996) {{doi|10.1038/383305a0}} My ''Nature'' subscription only lets me access fulltext back to '97, but as I remember the content, the plant upregulates to 2-3 degrees above ambient temperature. Anthems are starting, the game is on, must go now. :) ] (]) 00:08, 13 June 2009 (UTC) | |||
:Warm bloodedness makes a more active life possible. You have to eat more, but you also have the energy to find the food. Plants, however, are rooted in the earth, which seriously limits their mobility and makes such a lifestyle unlikely. Unless they uproot themselves, like the ]. So it would make most sense if that trait evolved first. But I don't know of any real plants that can do this. The best chance of this happening seems to me to be in the water, where plants can float around and then still get their nutrients the plant way. Once they do that, the ability to swim may become an advantage, in which case warm bloodedness starts to make sense. | |||
:But then there is the necessity for muscles, which will be needed to use this energy. One way for plants to move is by growing. But then they would have to do that at an incredible pace and most of their energy would have to go into growing (and then splitting off in several plants, I imagine, something that plants are good at). The only other way that plants can move that I can think of is the way ] do it. The descriptions sounds a bit like the way muscles work (note that I'm not a biologist). And the way the signal is passed on even sounds a bit like a nervous system, which seems to me to be another necessity, for rapid response to the environment. Give these plants another million years of evolution, and who knows..... ] (]) 07:32, 13 June 2009 (UTC) | |||
::But none of those things actually require warm-bloodedness - the vast majority of animals that do these things are cold-blooded (or no blooded). Undersea life does not seem to have the same activity levels as land-based animals anyway - presumably most fish and crustaceans do not experience the daily temperature and associated activity levels of reptiles.]] 07:15, 14 June 2009 (UTC) | |||
* As I recall, Dyson thought "warmblooded" plants would have some kind of advantage in deep space. I'm trying to get at what that advantage could possibly be. --] (]) 20:57, 13 June 2009 (UTC) | |||
::: To make things harder, most plants have a high surface area to volume ratio compared to warm blooded animals, which means they are even less energy efficient in maintaining their heat. ] (]) 13:54, 15 June 2009 (UTC) | |||
= June 13 = | |||
== What is this bug? == | |||
In the past two days, I've seen two of little guys crawling around. Because I was too terrified to get a picture, I've done this awful MSPaint approximation. They're about 3/4 of a cm long, and the spots look like little fuzzy bits, and are arranged in a rectangle, with the darker orange on the outside and the beige on the inside. There is no shell or wings or anything, and they're not shiny. I'm in Toronto, Canada. I've never seen anything like it in my life -- what are they? And should I be worried? --<font size="3">]]]</font> 01:23, 13 June 2009 (UTC) | |||
::I don't know, but that's a great drawing, maybe you could ! ] ~~ ] (]) 03:36, 13 June 2009 (UTC) | |||
:::Oh, Ropata, that one made me laugh! Thanks, ] <small>(])</small> 06:44, 13 June 2009 (UTC) | |||
::: That drawing and your description makes me think these might be ](ladybug)larvae. There are many species of which the ] is causing a little concern in the UK following its invasion from mainland Europe over the last few years. Hereis an image of a Harlequin Ladybird larva. What I don't know is how common these beetles are in Canada. You have little need to be worried on a personal level as they eat aphids and other small creatures, unfortunately including the larvae of other ladybird species. ] (]) 07:18, 13 June 2009 (UTC) | |||
::::] is Canadian and has a pic of the larva in the article.] (]) 07:28, 13 June 2009 (UTC) | |||
:::::I second ladybug larvae. They are rather horrific looking but very peaceful (as long as you aren't an aphid). --] (]) 13:04, 13 June 2009 (UTC) | |||
Yes, it looks like it's probably some kind of juvenile ladybug. Frightening -- I hate ladybugs. (And all bugs. But ladybugs hold a special fury for me due to their invasion of 2003, and the fact that they tend to land on people.) Thanks guys. I guess I should be on the lookout for another ladybug invasion this summer. --<font size="3">]]]</font> 23:39, 13 June 2009 (UTC) | |||
== Carnivoran trait == | |||
Why do dogs, cats and bears have ridges on the roofs of their mouths? --] (]) 01:43, 13 June 2009 (UTC) | |||
:According to , | |||
:''Those ridges are called rugae. They are meant to help break down the food you are chewing, as food is pressed up against them during mastication.'' <small><span class="autosigned">—Preceding ] comment added by ] (] • ]) 06:20, 13 June 2009 (UTC)</span></small><!-- Template:Unsigned --> <!--Autosigned by SineBot--> | |||
:: Its not only carnivores, rodents also have palatal ]. ]<font color="black">e</font>] 18:36, 13 June 2009 (UTC) | |||
==Walking dinosaurs== | |||
When I naively looked at pictures of dinosaurs , I think I see a pattern. There seems to be two types of dinosaurs. | |||
1. Dinosaurs that walk/move on two legs | |||
2. Dinosaurs the walk/move on fours legs. | |||
It seems to me untrained mind that all the herbivore dinosaurs walk on four legs while all the carnivore dinosaurs walk on two legs. | |||
This to me seems really really odd, if you are a carnivore then you need all the speed in the world to catch your prey. Therefore you must run faster by using all four of your legs, running on two legs is really stupid. | |||
No carnivores today would run on two legs because your prey would run away faster than you can chase them. | |||
I approach this question and I came up with 3 ideas. I want everyone to criticize me ideas and suggest new ones. | |||
Three Basic Ideas. | |||
1. Carnivore dinosaurs run on two legs because they have a long thick tail. Because they evolve into having long thick tails, they are unable to run on four legs therefore they must run on two legs to balance their tails. | |||
2. Carnivore dinosaurs are blind, therefore they run on four legs. As they are blind they must hunt with their nose (sense of smell) therefore their front legs must be short as they move around with their noses to the ground. | |||
3. Carnivore dinosaurs only hunt in shallow streams, as they must move in shallow streams, the fastest way to move around is on two legs rather than on four legs. So they hide underwater and slowly move closer to their prey and pop up in the last minute to run on two legs towards their prey. This makes a lot of sense to me as I practice running on four legs on a shallow stream and it is very difficult. | |||
] (]) 08:39, 13 June 2009 (UTC) | |||
:First, I doubt that your hypothesis is right. Many birds (cladistically two-legged dinos) are herbivores. And why would you assume that a 4-legged animal is necessarily faster than a 2-legged on? Humans are excellent long-distance runners (well, trained humans ;-), ]es can run at over 70km/h. Take a look at some ] occasionally. Not all carnivores run their pry down in a sprint - there are endurance hunters, scavengers, and lurkers as well. And of course, to catch prey it is enough to be faster than the slowest prey - in fact, if anything the prey would have an incentive to evolve for speed ("The fox is running for its next meal, but the hare..."). --] (]) 09:19, 13 June 2009 (UTC) | |||
Running on two legs does not make sense because it actually increases the amount of air friction as the dinosaur chases it's prey. If it had run on four legs, it will minimize the air friction and have a streamline aerodynamic form and get a better grip on the ground. ] (]) 11:23, 13 June 2009 (UTC) | |||
::Both aerodynamics and traction are only a small part of the equation. In fact, among primarily walking/running animals, I'm hard-pressed to think of a two-legged slow mover - all the slow animals seem to have 4 legs. Walking on two legs requires permanent balancing, and therefore a more active metabolism. --] (]) 12:04, 13 June 2009 (UTC) | |||
:<small>Two monks (the biped kind) were walking through a jungle when a fierce carnivourous dinosaur jumped out at them. One of the monks calmly changed his sandals for a pair of Nike trainers that he happened to have. His companion said "Brother, what is the use of running shoes? Surely you realize that you cannot run faster than the fierce carnivourous dinosaur!" The first monk replied "I know that. I just have to run faster than you." ] (]) 11:28, 13 June 2009 (UTC)</small> | |||
::<small>Still laughing...still laughing...still laughing. ] (]) 15:19, 13 June 2009 (UTC)</small> | |||
:Air resistance is pretty negligable at the 10 to 20mph these guys might maybe have been able to reach - so that's irrelevent. There are super-fast 2 legged animals (ostriches, certainly) and super-fast 4-legged ones (Cheetah for example). There are also 2 legged animals with massive endurance (humans possibly have the longest walking endurance of any land animal) and 4 legged ones that are almost as good (horses, for example). I don't think speed enters into the equation here - and as others have pointed out, you can be a carnivore and only eat things that are already dead! | |||
: I suspect the reason for two-legged gait being better is that your head can be up higher while still having a stong neck, massive jaws and teeth. Getting your head up higher allows you to see further and pick up scent from the air better - that's great if you're hunting live animals, or if you're hoping to find that Stegosaurus that died of old age earlier today. But if you are the brutally-killing kind of carnivore then you need to get up on top of your prey to sink teeth in and use your weight to push it to the ground - and for that, it helps to have your principle weapons and body weight held as high up as possible. If you look at the way quadruped canivores like lions and tigers work in modern times - they jump on top of their prey and sink their teeth into the back of the neck. They can do that with four legs because their prey animals are pretty small - and at those small sizes, jumping is a definite possibility. Something weighing a couple of hundred pounds can jump fairly high - but a 7 ton T-rex isn't remotely going to be able do that! It's an odd fact that almost all animals from the flea to the elephant can only jump about a foot into the air from a standing start. Getting a foot higher is useful if you're a lion taking down a gazelle - but if you're a 30' tall carnivore trying to take down one of those gigantic herbivores and you can only jump 1 foot - then it's pretty much useless. Hence if you need all the height you can get, a two-legged gait makes a lot of sense. | |||
: Someone should also explain about bird-hipped dinosaurs versus the lizard-hipped kind. I forget the details - but I bet that matters. | |||
: ] (]) 18:04, 13 June 2009 (UTC) | |||
::As for the two different types of dinosaurs, see ] (bird-hipped) and ] (lizard-hipped). To generalise, ornithischian dinosaurs were usually four-legged and herbivorous, while saurischians included the ]s (long-necked four-legged dinosaurs, usually herbivorous, some omnivorous) and the ]s (two-legged, carnivorous or omnivorous). The late-Cretaceous ]id (therapod) dinosaurs included the ones that developed the most "advanced" brains, and are rather similar to today's birds. ~<font color="blue">]]]</font><sup>(]]])</sup> 22:26, 13 June 2009 (UTC) | |||
The way I see it is they evolved to be two legged to sharpen their hunting technique. What is the key thing dinos do in the movies? They jump really high, and pin their prey beneath them. Four leggers, on the other hand rarely hunt this way. In fact the mor efficient hunters tend to hide in the bushes and make extremely long range jumps, rather than the high jumps used by dinos. Could you imagine anything that walks on four legs making this kind of jump?]rew ] ] 09:19, 14 June 2009 (UTC) | |||
:The OP is incorrect to claim that "''if you are a carnivore then you need all the speed in the world to catch your prey.''" because for success a predator needs other characteristics that may be incompatible with having maximum speed. Some useful abilities for a predator are maneuvrability, having size and colouration that are appropriate for lying in ambush or stalking close to a prey, finely tuned senses of sight and smell, a cooperative pack strategy, a combination of muscles + teeth + claws sufficient to triumph against the prey and the sense not to take on losing battles. Mating between predators happens only after some delicate negotiation. ] (]) 12:03, 14 June 2009 (UTC) | |||
==How hot is boiling water?== | |||
I was watching QI last night when Hugh Fearnley-Whittingstall mentioned that water on a "rolling-boil" was much hotter than water that was simmering. I have never really understood the difference between boiling and simmering, because in both cases the water is turning into vapour and therefore presumably reaching 100C, and I would not have expected that it would go over 100C (at least not by very much). Now I am wondering whether, on a rolling boil, whether so much heat is being put into the bottom of the pan that the water actually is getting much hotter (as HFW states) than 100C, before it gets a chance to vapourise. I read ] but it does not seem to give a definite answer. Can anyway help clarify what actually happens please? ] (]) 09:21, 13 June 2009 (UTC) | |||
::::<small>Were you not, in fact, watching ]? ] (]) 11:53, 13 June 2009 (UTC)</small> | |||
:::::Yes, actually you're right, I was! I watched both last night and I guess I merged the two together. This is what happens when you waste your life watching panel shows! :) ] (]) 12:03, 13 June 2009 (UTC) | |||
:Pressure at the bottom of an open saucepan of water is higher than atmospheric due to the weight of water above. This raises the boiling temperature slightly. With heat applied from below there is continual vaporisation of water at the base from which bubbles of vapour rise and are replaced by new water. This process absorbs considerable heat energy due to the latent heat of vapourisation that water requires. Superheated steam could be generated only by such a huge inflow of heat that vapour is generated faster than can be replaced by liquid. ] (]) 11:14, 13 June 2009 (UTC) | |||
::Thanks. Based upon my scuba experience, I believe that, very roughly, 10m over water exerts the same pressure as 1 atmosphere. Asssuming that the water in the pan is maybe 10cm, that would seem to indicate only a 1% rise in pressure at the very botton of the pan. In comparison, accoring to ] raising the pressure to 2 atmospheres would lead to a boiling point of 122C, so I am guessing that the depth of water will have an incredibly small impact on the potential water temperature. Is that correct? I had a quick read of ], but I'm not sure I really understand. It seems, as you say, that a lot of energy is required to actually vapourise the water (5 times more than is required to raise it from 0 to 100C?), but how does that actually affect the temperature of the water (and of the vapour that is formed) and how does that transfer to the food?<nowiki> | |||
</nowiki> I am assuming, probably incorrectly, that the food absorbs heat primarily from the water, and that the water itself is still around 100C. Is the vapour much hotter, and does that heat also transfer to the food. Thank again for your help. ] (]) 11:30, 13 June 2009 (UTC) | |||
::: When you keep heating water, from say 25<sup>0</sup>C, the temperature also rises uniformly, approximately given by the equation, <br />Heat = Constant * (Change in Temperature).<br /> This goes on till you reach the boiling point of water, say at atmospheric pressure, at 100<sup>0</sup>. When you further heat water, the temperature does NOT rise. It remains at 100, the heat is absorbed to convert the water into steam. When all the water is converted to steam, only then does the temperature again rise. This extra heat supplied to raise the temperature from 100 onwards is called Latent Heat of Vaporization. I just thought i would explain this, I'm not sure about the other parts of the question. I presume the entire water would be at a constant 100<sup>0</sup>C. ] (]) 12:34, 13 June 2009 (UTC) | |||
::::(ec) No it is '''credible''' not incredible that the depth of water has a small impact on the boiling temperature. Absorbing the latent heat of vaporisation does not raise the water temperature, it just changes the water's state from liquid to vapour. As long as the vapour bubbles disconnect from the heat source (base) as fast as they are formed they are not hotter than the boiling temperature. Since the thermal capacity of liquid water is higher than the expanded vapour you are correct to assume the food absorbs heat primarily from the liquid (it's all called water). ] (]) 12:41, 13 June 2009 (UTC) | |||
:::The variations in air pressure due to weather (pressure, humidity, etc), and your current altitude, probably affect the boiling temperature of water much more than the 10 cm or water pressure. Also, impurities in the water (such as trace quantities of salts and carbonates) also probably affect the boiling temperature much more than the 10 cm of water pressure. You can easily probe the water with a thermometer to find out what temperature it is when various levels of boiling activity become prominent. I know that my water is not receiving heat uniformly, because I can see nucleation sites forming preferentially tracking the shape of my electric stove's heater coil (even if I slosh the water around or move the pan) - so even this heat conduction effect seems to be more important than the static water pressure. <nowiki> | |||
</nowiki>In truth, the thermodynamics of a "simple pot of water" are very complicated - a huge number of competing phenomena, including water convection, cohesion, heat conduction, heat radiation, phase change and latent heat of vaporization, bubble-formation and fluid interaction, etc. All of these require elaborate statistics and calculus (]) to solve "exactly" (if such a thing can be solved exactly). The true temperature of the water when boiling is approximately 100 degrees Celsius, but ''at best'' this is a macroscopic average over the entire pot of water. ] (]) 15:30, 13 June 2009 (UTC) | |||
:Incidentally, that's a "roiling boil" (i.e., boiling sufficiently to roil the water,) not a "rolling bowl." -] (]) 15:00, 13 June 2009 (UTC) | |||
::Actually I think that both are correct , not sure if usage varies by location. In the video that I linked at the bottom of this section, HFW does seem to be saying "rolling" (not sure if you can view the video), so maybe "rolling" is more prevalent in the UK. ] (]) 11:06, 14 June 2009 (UTC) | |||
:::Although the first time I mentioned it in my opening question you are right that I did say "bowl"! :) Luckily I used the correct spelling later in the question, so hopefully I don't look like a complete dunce! :) ] (]) 11:09, 14 June 2009 (UTC) | |||
:As most writers above seem to agree, a rolling boil is within a gnat's whisker of 100 °C. WP says that ] starts somewhere between 82 and 94 °C. So on average HFW appears to be right. --] (]) 17:19, 13 June 2009 (UTC) | |||
: At normal pressures - the water can't get above roughly 100 degC without turning to steam - so the energy supplied by the stove top can't increase the temperature any further without first boiling all of the water away. I suppose any steam bubbles sticking to the bottom of the pan could get a little hotter than 100 degC before they floated up to the surface - but not by much because the surface tension of the water will tend to keep at least a thin layer of water between the pan and the bubble. | |||
: But I do know that in a water-cooled car engine, if there is no detergent in the water, bubbles of steam will form in some of the narrower passageways through the engine block and the temperature of the metal around them can spike quite high. That's why it's undesirable to fill your radiator with pure water without either "water-wetting-agents" or antifreeze. That's because the bubbles get trapped inside those narrow tubes and can't easily rise to the surface as they would in a pan of water on the stove. | |||
: What I suspect is being implied in the original post here is not that the water is literally hotter when it's boiling - but that things in the pan get cooked faster by 100 degC water that's boiling than 99.999 degC water that's just a fraction short of boiling. That is certainly a true statement - but it's about heat energy - not temperature. The reason is that when a steam bubble hits whatever is being cooked - which is still at less than 100 degC (presumably) - then the steam will rapidly condense back into water. When it does that - the steam gives up it's "latent heat of condensation" and a LOT of energy is transferred to your food as steam at 100.00001 C condenses into water at 99.99999 C. Transferring energy into the food cooks it quickly - even though the water keeps the temperature at a solid 100 degrees. | |||
: People who get almost-boiling water spilled on themselves don't suffer too much injury - but it doesn't take much steam at almost the exact same temperature to cause severe burns. | |||
: ] (]) 17:41, 13 June 2009 (UTC) | |||
:::Whoa! It doesn't take much boiling water either. Where I live, "they" now advise people that water heaters should be set no higher than 50°C, on the grounds that 60°C is hot enough to be a significant safety risk to a person who doesn't react fast enough. I'm willing to take that risk, but that's not the point: an equivalent mass of steam may be worse than 100°C water, but the water can be bad enough. --Anon, 20:40 UTC, June 13, 2009. | |||
::As Heron pointed out, not all the water in a simmering pot is boiling - this is connected to what Nimur discusses further up. So the overall temperature of the water is cooler than in a pot at a rolling boil - where just about all the water is boiling. This isn't a matter of 0.00001°C, as discussed in the article Heron linked to. ] (]) 19:03, 13 June 2009 (UTC) | |||
Thanks for all of the above. I'm tempted to go and buy a thermometer now and check the temperature at different stages of boiling (still confused, because I always consider "simmering" in terms of "bring to the boil, then simmer", suggesting that the water is boiling - but I guess there are different stages of simmering too). BTW the original comments from HFW can be found (for the next 7 days and, I think, only for people on a UK IP address). ] (]) 10:56, 14 June 2009 (UTC) | |||
== Suicide Question == | |||
Hello,Im not seeking medical advice, just a curiosity, whats the best method of commiting suicide if you are locked in a room whit absolutely no tools (only your body)? (Not my case , if im writing this I have electricity and I can finish myself of this way. | |||
DST | |||
:It's good that you don't seek medical advice because Misplaced Pages won't give it. The best method is not to entertain a morbid curiosity. ] (]) 11:20, 13 June 2009 (UTC) | |||
Its a scientific question, no morbid curiosity i stated it before. <small><span class="autosigned">—Preceding ] comment added by ] (] • ]) 11:26, 13 June 2009 (UTC)</span></small><!-- Template:Unsigned --> <!--Autosigned by SineBot--> | |||
:There are plenty of ways to kill yourself under those circumstances. I'm not sure what you mean by "best". The most efficient? The least painless? Both are hard to gauge. I'm going to assume that simply dying of starvation and dehydration wouldn't be an option, for whatever reason -- so that implies that there's a kind of a time limit in which you need to get this done. In any case, under those circumstances, it's definitely going to get really ugly, and it's going to take some serious, serious will to die. I'm pretty sure most of us couldn't do it, because it's just too goddamn hard. | |||
:But there are options. If you have clothes, you could hang yourself or try to choke yourself with them -- but perhaps you're naked, what with the "absolutely no tools" parameter in place, and unfortunately, that's about as easy as it gets. You could chew through the arteries in your arms and bleed to death. You could bash your head against the wall or against a sharp corner if there's some sturdy furniture around. You could try to throw yourself down and land on your head so you break your neck -- again, probably easier if you had some furniture around, so you could jump off it. You could probably break your own neck with your hands. You could crush your own larynx and choke to death. You could simply punch yourself over and over again until you do some real damage. | |||
:I mean, as long as your body still obeys your commands, there are things you can do to damage yourself very badly. But none of these methods are easy, and all of this would be extremely difficult to do, not only because of the physical challenges involved but because this kind of stuff really goes against the grain: the instinct for self-preservation is going to make the kind of extended effort this kind of thing requires very, very difficult. That's why people who commit suicide generally do it in a way that's either fairly peaceful or fairly quick -- if all you need to do is jerk your finger or jump once, that's relatively easy. Repeatedly smashing your fist into your own body as hard as you can in the hopes of rupturing some internal organs or cracking a rib so it'll puncture a lung -- for example -- is a different story. | |||
:But even if you were to attempt something like this, it's hard to ''guarantee'' success; if you hesitate at the wrong moment, or don't have the willpower to go through with it, or just make a mistake, you could just incapacitate yourself instead of dying, and take too long to die. It's not a problem if no one is coming to stop you, of course, but if that was the case, you could just stop eating and drinking and let dehydration take care of it. | |||
:So what's the best method? I don't know. Personally, I wouldn't recommend any of them, because I'm not that kind of crazy, but rest assured that if you're locked away in that cell and 24 hours from now the alien invaders are going to march in and drag you to the Brain Probe to find the secrets of Earth's defense network from the deepest recesses of your mind, there are things you can try and, if you have the willpower and a basic understanding of what parts of your body are vital, and you're a little lucky, you can do it. Probably. -- ] (]) 12:11, 13 June 2009 (UTC) | |||
:::We have an article called ], which details the successful and unsuccessful suicide methods of several prisoners locked in a room with no meaningful tools. Many of them attempted to strangle or hang themselves with their own clothing. Many managed to fashion a knife or sharp object. Many have undetermined or unreported method of suicide. ] (]) 15:18, 13 June 2009 (UTC) | |||
::::Just wait for a week or so and you will die from ]. You can speed this up by vigorous exercise, though you won't be in the mood for dancing for very long.--]|] 16:29, 13 June 2009 (UTC) | |||
:::::If you'd like to volunteer for a ] you could try to verify the urban myth whether you can obstruct your airways with your ]. Commonly referred to as "swallowing one's tongue". There are retching reflexes that should prevent that, but there's suspicion that running out of air might possibly interfere with that function. Another unreliable method would be to try to create a blockage in the ] and hope for that to disrupt the major cartoid arteries. ] (]) 21:07, 13 June 2009 (UTC) | |||
:Hold your breath. Pinching your nose may help. In the meanwhile, if you change your mind, stop the procedure and start breathing again. --] (]) 22:51, 14 June 2009 (UTC) | |||
== Cancer rates in mammal species including humans == | |||
Are the rates across different species similar, or do they differ? Do humans have the greatest rates of cancer? ] (]) 11:16, 13 June 2009 (UTC) | |||
:See the section on whale cancer above. They seem to differ, and differ significantly. --] (]) 11:23, 13 June 2009 (UTC) | |||
::I was hoping for more information than just for whales and cows. ] (]) 12:25, 14 June 2009 (UTC) | |||
::It was 1/3 for humans in Ireland a few years ago. Not deaths, just 'adults that will have cancer at some time in their life'. No link sorry. ~ ].].] 12:12, 13 June 2009 (UTC) | |||
:I'm afraid I couldn't find any reliable figures even for cats and dogs where you'd have thought the statistics would be best and you can be sold insurance and treatment. ] (]) 12:34, 14 June 2009 (UTC) | |||
== Air hunger / winded when stuck in lungs == | |||
Some times when I get struck in the lungs, such as being punched in the lungs, I get winded/air hunger. I understand that this only happens when there is too much carbon dioxide. How does getting punched trigger too much co2? Is it because the lung is contracted so the pressure increases and body thinks it detects a high level of carbon dioxide? Does anyone know typically at what level above normal atmosphere air hunger typical triggers at?--] (]) 11:45, 13 June 2009 (UTC) | |||
:The wikipedia article on air hunger defines it as the sensation or urge to breathe, and says that it is usually from a build up of carbon dioxide, but that doesn't sound like what you are describing. Us humans have three mechanisms that trigger breathing. One is based on stretch receptors that sense how often we expand our chest. This is the mechanism that most people must fight against to hold their breath, and is often neglected in citation of a second mechanism in which breathing frequency is controlled by the amount of carbon dioxide in the blood. This mechanism is important for long periods of breath holding, and unconscious people (such as in pearl divers and ICU patients) and controls our overall breathing rate more than it does each individual breath. It also keeps us breathing when we sleep. The third, and by far the weakest mechanism is based on the amount of oxygen in the blood. This so-called "anoxic drive" is really only important in that it is something to be avoided in patients who get oxygen therapy for long periods of time and at high concentrations. The air hunger that you describe sounds like the first one, and likely has nothing to do with carbon dioxide. When one is struck in the stomach or chest, the muscle that controls most of our breathing, called the diaphragm, can be suddenly stretched in a way that causes it to spasm or be temporarily paralyzed. This is often called "losing one's wind" or "having the wind knocked out of oneself", and is similar in cause if not duration to a hiccup. When this happens, we must use our far less effective chest wall muscles to exchange air for the short duration of the spasm, and the inability breath deep to stretch those stretch receptors, in addition to being just plain scary, leads to the distinctly uncomfortable "air hunger" that I believe you are describing. ] (]) 14:05, 13 June 2009 (UTC) | |||
::Misplaced Pages really does have an article on everything, including ]. Maybe we should redirect/rename that article to something more scientific. It is a common name for a mild (or severe) injury to the ], the muscle responsible for inflating and deflating the thoracic cavity (and the lungs, by proxy). When injured, this muscle may temporarily spasm or experience paralysis. Naturally, the severity of this injury ranges from mild to life-threatening. We can not give medical advice or diagnose your injuries, so if you are worried about repeated trauma, you should consult your medical doctor. ] (]) 15:22, 13 June 2009 (UTC) | |||
== What is the nature of the big bang? == | |||
There is a theory that for the Big Bang to make sense in a ''uni''verse, it would have to be equal parts ''implosion'' (sorry, define that as equal parts shrinking internally), both internal and external elasticity, accounting for all angles of everything. Supposedly that would be more difficult to prove/disprove than the bang itself. Is that a preposturous thing to consider? ~ ].].] 18:21, 13 June 2009 (UTC) | |||
:No, not preposterous, but too vague. ] (]) 19:36, 13 June 2009 (UTC) | |||
::For every action there is an equal and opposite reaction, for all matter there is, possibly, an anti-matter. If the bang/fusion were so all-encompassing, it could be very precise. That would give it a definite center. ''That'' could make it a skin or a layer. Perhaps there is a light which has been receding? ~ ].].] 21:08, 13 June 2009 (UTC) | |||
:::You still don't get it do you? Just making a long string of fanciful scientific sounding words does not a meaningful statement make. Just answer me that following question: How is the law of action and reaction and the existence of antimatter related to your vague idea of a expanding shell arounding a shrinking center. Be specific and use logic. ] (]) 21:23, 13 June 2009 (UTC) | |||
RTG, your recent questions at this refdesk resemble Chomsky's "]", in that the string of word ''can'' be interpreted to have some metaphorical meaning in some technical sense, but are in plain-speak nonsensical. I would echo the advice you have been previously given that you will be better off spending your time reading some basic high-school physics text, instead of wasting it on idle and pseudo-scientific speculation. You can find a list of useful physics textbooks . If you don't wish to borrow or buy one of those books, you can read some of the free texts or even browse wikipedia - although personally I would recommend against such a slapdash approach. Hope this helps. ] (]) 21:29, 13 June 2009 (UTC) | |||
::I am suggesting that there would need to be something ''in'' that center. We have anti-everything else in theory and practice so where is the anti-light? ~ ].].] 21:38, 13 June 2009 (UTC) | |||
:::I still can't tell exactly what you're talking about in regards to a centre. I also cannot tell why you're saying there has to be something there, nor what that has to do with light. That seems to all be nonsense. As for "anti-light", you may be confused as to what an ] is. An antiparticle has the opposite electric to its non-antiparticle companion. Photons have no electric charge, so they have no anti. -- ] <small>(])</small> 21:48, 13 June 2009 (UTC) | |||
::::I concur that RTG isn't clear on antiparticles, but your definition doesn't hold, either. ]s have been known for 50 years and have no charge (just like their standard counterparts). We don't expect "anti-light" because light isn't composed of ]s, of which antiparticles are a subset. — ] 23:43, 13 June 2009 (UTC) | |||
:::::Yeah, that's true enough. Antineutrons aren't elementary though; the antiquarks composing the antineutrons do have electric (and color) charge, which ''is'' flipped. -- ] <small>(])</small> 23:53, 13 June 2009 (UTC) | |||
::::: (after ec) Surely you meant ]s (and their collections) and not ]s ! An electron is not a hadron but has an anti-particle (the ]); ditto for other ] and ]. <s>You are right though that ]s such as ]s do not have an anti-particle in the ].</s> ] (]) 00:01, 14 June 2009 (UTC) <small>(struck out misleading statement.] (]) 06:36, 14 June 2009 (UTC))</small> | |||
:::::That's not right either, in two accounts. First, some elementary fermions are neutral - we call them neutrinos - and they may turn out to be their anti-particles or not. We don't know that yet. Second, some gauge bosons have anti-particles which are distinc from themselves. The anti W+ is the W-, for instance. Even some chargeless bosons may not be their antiparticles such as some of the gluons. The particle-antiparticle thing is a symmetry of nature and some particles simply are their own "reflection" through that symmetry. A good analogy is given by looking at gloves and socks on a mirror. The righthand glove turns into the lefthand glove on a mirror and vice-versa. The rightfoot sock and leftfoot sock are identical. Socks are their own antiparticles. Gloves are not. ] (]) 01:19, 14 June 2009 (UTC) | |||
: Fun fact : RTG first wrote "insulting" before he changed it to "preposterous". | |||
: RTG you're just mentioning a bunch of concepts and stringing them into sentences with no meaning and then asking us for debate. | |||
: Do you have any '''reference''' questions for the reference desk? ] (]) 21:45, 13 June 2009 (UTC) | |||
:: ] provides a good overview. Its not really within the remit of a ] to consider the merits or otherwise of theories. We just provide references to such theories. If one is lacking, then there is little we can do to assist you. Is there are specific subject or reference you are interested in? ]<font color="black">e</font>] | |||
::I don't ''think'' RTG is trolling, floating ideas to prod debate, or asking bad-faith questions. I think he has merely never studied or read a book about the subject and has many incorrect impressions, is all. RTG, I recommend '']'', by Stephen Hawking — the book, not the documentary. If you can stick with it then I recommend taking some related courses at your local community college. ] (]) 05:06, 14 June 2009 (UTC) | |||
:::APL and Pocketrocket are right. I thought some of you were being awfully rude but this is not a study group or a discussion center. I am just saying stuff like "What if that lines is curved?" I have read some Stephen Hawking, Tempshill, and it is very good but to go to college with that sort of thing is a matter of mathematics not just idle curiosity. I am just making personal amusement here, please forget about it. ~ ].].] 13:02, 14 June 2009 (UTC) | |||
== Running a Race == | |||
Is it a better idea to run the day before a 5k race or is it a better idea to rest the day before a 5k race?--] (]) 19:44, 13 June 2009 (UTC) | |||
:A 5 kilometer race is not an extremely strenuous run, but the answer depends entirely on how you have been training. An optimal training regimen will vary based on a lot of things, like your age, weight, and diet (not to mention your health and medical conditions - consult a doctor, etc). Even if you are training for strenuous run conditioning, it's often best to run no more than every other day. This gives your muscles time to recuperate and generally gives better performance (endurance and sprint capability). ] may help give some ideas about run conditioning training. ] (]) 21:26, 13 June 2009 (UTC) | |||
::The article ] describes the theory behind timing one's training exercise to maximise fitness "on the big day". It also cautions that there is no one right period for the effects described. Therefore an answer to the OPs question should not be given by Misplaced Pages. The supercompensation theory may be useful only if the phases described have been actually observed and timed in an individual, ideally by a skilled ]. ] (]) 21:33, 13 June 2009 (UTC) | |||
:::I think the standard answer is that the day before a race, it's best to run just enough to keep yourself loose. It matters less for a 5K than for longer distances, but it will still help. ] (]) 02:16, 14 June 2009 (UTC) | |||
== about death == | |||
Can we will be able to overcome over death.can we find out its answer .Here i m not talking about death of universe with change in entropy . <span style="font-size: smaller;" class="autosigned">—Preceding ] comment added by ] (]) 21:53, 13 June 2009 (UTC)</span><!-- Template:UnsignedIP --> <!--Autosigned by SineBot--> | |||
:Have you read ]? As far as I know when we die we are no more, just like before we were born. Other people believe all sorts of things like that one has an immortal spirit. Even if the universe was eternal I see no way a person could be immortal and have a meaningful existence. Either they could accumulate more and more experiences without any bound or they would stay their original limited selves and forever in effect keep repeating the same old things and not develop. If they develop without bound they would not be the original person. I suppose it would be reassuring though not to have death looming as an immediate anxiety. ] (]) 23:35, 13 June 2009 (UTC) | |||
:Personally I'm a bit sad about the fact that one day ''I'' must die, but the thought that everybody must die as well, greatly cheers me up. Up to now, natural death is the safer way we have to get rid of the worst people around. --] (]) 23:43, 13 June 2009 (UTC) | |||
:Much more serious (but possibly exceeding the horizon of the science desk) is the question: "Will we be able to overcome birth?" Other people, as implied by ] above, speculate idly that there may be life after birth, yet evidence from any prenatal curly position is not conclusive. --] (]) 23:59, 13 June 2009 (UTC) | |||
::Now that, Cookatoo, if I may be allowed the intimacy of your first name, is funny! ] (]) 00:04, 14 June 2009 (UTC) | |||
::: I wonder if, by "overcome" the OP is referring to preventing or indefinitely postponing death, rather than surviving it in some form? If so, the work of the ] may be of some interest to you. The reason we die - assuming disease or misfortune doesn't get us first - is due to the cellular and physiological effects of ]. If you can over-come aging, then you can overcome death (theoretically, in reality you would also have to overcome ] or else that would get you eventually). ] provides some strategies towards this goal. | |||
::: The good thing about death is that it provides the ultimate ''I told you so'' moment of vindication, for either those who do, or do not, believe in an ]. The bad thing is that there is no-one of the other persuasion around to gloat over. ]<font color="black">e</font>] 00:32, 14 June 2009 (UTC) | |||
:] has been forecasting that we will all be able to transfer our minds into computers by 2050, and our intelligences will live on, immortal. ] (]) 04:34, 14 June 2009 (UTC) | |||
::The theory behind that goes something along the lines of plugging in the minute electrical pulses along our spines and transferring it into a computer. In reality this would prove to be extremely dangerous, and may not even produce results. | |||
::How does one "plug" into a spine? Seems to me (I'm no expert, not by a long shot) that this would be very delicate and dangerous. One false move and the spine would be damaged, thus paralyzing, or even killing the subject. | |||
::It seems like it may be futile because those electrical pulses probably don't contain our "soul". More accurately, they don't hold our memories, our self awareness, or anything that could be identify it as an individual. Even if you could get them into a computer, whats to say it'll actually do anything? | |||
::Which presents another problem. Taking the electric pulses would kill the body. So if it doesn't work you've got a dead guy, and possibly a fried computer. Ultimate "oh shit" moment, no?]rew ] ] 04:50, 14 June 2009 (UTC) | |||
:::Attaching electrodes to spines of living people and sending electrical pulses along them has already been done, so is not necesarrily deadly, and would seem conceptually reversible (The only example i know of though was a programm using the technique to install experimental orgasm controllers in women, which had some success.). Measuring an electrical pulse could be done without erasing it, so that would seem soluble to. Which then leaves the questions of "soul", which of course have no scientific answer anyway.]] 06:59, 14 June 2009 (UTC) | |||
::::No, sending the pulses isn't deadly, but if you take them all out, and leave nothing (which I'm assuming you would have to do to create "existance" on the computer) wouldn't the body die? And I was using "soul" in a non-religious, non-scientific way. I meant the essence of who you are. If you kill the body but don't capture the "soul" it was all for nothing.]rew ] ] 09:27, 14 June 2009 (UTC) | |||
:::::Drew, have you ever had an ] recording? If so, did you leave your irreplaceable essence in the ECG machine ? ] (]) 11:33, 14 June 2009 (UTC) | |||
:::::Drew, impulses in the spine are "taken away" quite often, in certain cases of ] (an ]) and all cases of ], which has a death rate of 5-6 per million . --] (]) 17:16, 15 June 2009 (UTC) | |||
::::::The synaptic gap is a complex electrochemical signaling pathway, but it can be modeled as a high-impedance voltage source. You can connect many electrical loads in parallel to a single voltage source without any trouble - that is an operating principle of an ECG or EEG. (In other words, when the electrical pulse "goes in to the cardiogram machine", it also "goes in to the heart muscle" in parallel, with negligible loss of power. There is no need to worry that the neural electric signals will get "sucked into the machine" forever. Take a look at ]. A more realistic problem, as has been pointed out, is that we don't really know what signal we are looking at when we probe a nerve, and we can say with pretty good certainty that the electric pulses on the spinal nerve are not "the soul" (they are probably not even related to any cognitive process at all). The spine is primarily used to relay control messages and sensory input between the brain and the rest of the body. ] (]) 14:29, 14 June 2009 (UTC) | |||
:::Sticking one's personality into a computer seems like a bit of egotism to me. Unless you killed the original person there would then be two people starting off with the same memories. ] (]) 11:43, 14 June 2009 (UTC) | |||
::::Sounds like a great way of improving the methodology of psychology research. --] (]) 17:16, 15 June 2009 (UTC) | |||
:: 2050 is a LONG time away in computer technology. If you look back 40 years and see where computers were in 1970 and use that to extrapolate to 2050 - I have no problem believing we could have computers of reasonable size and cost that would have the power to run a neural network simulation of an entire human brain. This issue came up in the Ref desk a few years ago - and I calculated that if Moore's law continues than a suitable computer could be purchased for a million dollars (present value) by about 2035 - it would have the capacity to simulate the brain - but perhaps not in "realtime" (so the simulated human would think rather slowly). By 2040, everyone could afford one - and by 2050, an affordable machine would be cheap and faster than a real human brain. So the computer technology side of things is a done deal...it'll happen so long as Moore's law continues (which, admittedly, can't be forever). Since we know the real brain has the computational power to fit that much computer in that volume of space - I have little doubt that we could do it in the space of (say) a 10' x 10' x 10' cube...which is plenty small enough. So people who have a million dollars put away (which is a surprisingly large number of people) could be "retiring" into a computer in 25 years. The problem of thinking slowly is not so great - but once the brain is inside the computer - the underlying computer hardware can be upgraded over the years until their thought rates catch up (and ultimately exceed) that of living, biological people. | |||
:: The trickier question is how and when do we put your brain into the computer? Some kind of non-invasive brain-scanning machine that could somehow figure out all of the interconnections and such would be idea. If it could do the job in a matter of hours, while we sleep perhaps, then you could make a 'backup copy' of your brain every night - and when you die - you'll only have lost the memories formed in the last day...which are probably best forgotten anyway. However, I suspect that people might want their brain scans to be taken while they are in the prime of their mental acuity - and that starts a complicated moral/ethical matter of when to stop recording...since any memories made after that point would be lost. | |||
:: But that assumes that this 'brain recording' process is non-invasive and fast (and cheap!). If it's non-invasive but slow (or ruinously expensive), you might have to go get your brain scanned once a year or once a decade. If it's not non-invasive (like maybe you have to slice the brain into thin slices in order to get the data) then clearly you can't do this until you're already dead. Now the moral/ethical part gets even tougher...would people choose to commit suicide at a young age when their brain is functioning at it's peak in order that their electronic "afterlife" would be more productive? I don't know - but I don't think it particularly complicates things. | |||
:: The business of the lack of a "soul" is something I completely discount. This is a scientific matter - not religious claptrap. Everything that makes our brains tick is due to the configuration of the neurons - and that can be completely simulated given enough computing horsepower. | |||
:: Another issue relates to "quality of life" for these electronic people. Can we interface cameras, microphones, taste and touch sensors into these electronic gizmo's? Would robotic bodies be an appropriate thing to attempt? Would we instead build a virtual world for these virtual people to inhabit? I could certainly imagine the latter...something like "The Matrix" - an elaborate multiplayer computer game in which the inhabitants are driven by people who are now inhabiting these computers. | |||
:: For the electronic brain - there would be no reasonable difference between the living person and the electronic version - their thought patterns can be identical - they will feel that they are still alive, they'll have all of their memories - and the means to form new ones - their dearest friends and relatives would recognize them by the things they say - the way they think. The electronic person would be able to hold down a job - which would be necessary in order to pay for electricity, software backups and replacement computer parts. | |||
:: Some very exciting things become possible - you could choose to run your brain at varying clock rates. If you're bored - you can "fast-forward" to the next interesting thing. You could pause your brain for years, decades, centuries and "time travel" to the future. You could send an empty computer on a slow rocket to the nearest star - and when it gets there, transmit your brain pattern to it. You'd be able to travel around the universe at the speed of light...but in zero time as far as you are concerned. One moment you're here on earth...then ZZAPP! and you're in orbit around Alpha Centaurii. Of course, when you come back with your new memories and holiday snaps - 8 years have gone by here on earth - but your (dead) friends and relatives can fast-forward through that if they miss you - and for you, it seems like no time has passed. | |||
:: Being able to make copies of yourself is an interesting and difficult thing. If the computers involved are merely simulating a human brain using mathematical models of biological neurons - then there would probably be no way for your two copies to be merged back together again...so you couldn't (for example) have a copy go on vacation while the original stays home - then merge them back together again and have memories of both things...that (I think) makes it less interesting to make copies...but it's obviously possible - and more ethical/moral dilemmas are bound to happen as a consequence. | |||
:: There is also the possibility of running your electronic brain faster than realtime. This would be one way to make a living - being able to think at (say) ten times the speed of a living human would give you some significant advantages in the job market. Electronic people with more money would be able to upgrade their computers more frequently - and have faster models than poorer people. Rich people would be able to hold down better jobs...not much changes there, I guess. | |||
:: In the long term - there might be trillions of electronic people - and only billions of biological people. It might be that we come to think of these brief biological years as a kind of childhood...but the need to look after these trillions of computers - provide power, spare parts. upgrades...that would soon come to dominate the "work" of mankind. But with robotic maintenance workers - maybe even that isn't a problem. | |||
:: For people who come to tire of life in this electronic form - suicide is a simple matter. But the ability to "fast forward" your life would probably mean that these people don't choose to kill themselves - but merely slow down their brains more and more to travel futher and further into the future - in the hope that something better comes along. In this form, "fast-forwarding" people would consume virtually zero resources - their minds could be archived for years on "backup" memory (like the hard-drive on your PC) - and only reloaded once in a while as requested before they slept. Much of mankind might be in backup memory form for most of the time - waking up only once a century to see what's new. | |||
:: A lot depends on the technology of the brain scanning machine. That's really the only technological hurdle...we have brain scanners that work at larger scales - I could imagine them getting more and more precise - until they could resolve individual neural connections. There is active research in these areas. I wouldn't be surprised to see this happen by 2050...and the closer we get to it - and the more people who realise that the long-sought goal of immortality is within our grasp - the more that research will be pushed. | |||
:: I think this can happen - and within the lifetimes of many of the people reading this page. Sadly - the math says that I probably won't live long enough to make use of it...darn! But I think there is every possibility that if you are (say) 30 years old or younger today - then you could wind up living as long as you want...but not in your biological body. | |||
:: ] (]) 14:46, 14 June 2009 (UTC) | |||
:::<small>Nice to meet you, Mr. Kurzweil; it's an honor to work with you here on the refdesk. Wish you hadn't been pseudonymous for all this time. ] (]) 16:43, 14 June 2009 (UTC) </small> | |||
::::Ouch! I'm pretty sure that accusing someone of being Ray Kurzweil falls under the WP:NPA rules! :-( 17:58, 14 June 2009 (UTC) | |||
Don't kid yourself. Memory banks might extend the life of your computer not your soul. ~ ].].] 20:15, 14 June 2009 (UTC) | |||
::Well Steve, I'm optimistic for the future that you envision, because it seems like progress to me; but I really wonder if Moore's Law is actually even relevant on the technology roadmap to making this happen. I see more important obstacles than hardware capacity standing between our present society and a computerized, brain-in-robot-body utopia. | |||
::Without doubt, computers are rapidly accelerating (even the last few years of thermal nightmares, clock-rate growth-pains, and economic downturn have not been able to slow the pace by much). Disk storage is so huge it's laughable (at the lab on Friday, they just threw out several sets of 300 GB disks because they're "outdated" and not cost effective!) And with a sizable server room, we can stuff petaflops and zetabytes and gigabytes of bandwidth. | |||
::But what about software? Every day I work with brilliant physicists who still don't know the meaning of "pthread" - so when we provide them a rack of 400 cpus, they use them one-at-a-time (not always, but more often than we'd like). We're at a crossroads of computer interfacing technology - it's becoming harder and harder to stay at the cozy abstraction layer we have been in for a decade or more, because harnessing these new computer technologies means getting down and dirty with the hardware model. <small> you say, but what's ] again?</small> And we're solving "conventional" programming challenges - number crunching type problems. Faster number-crunching machines do not immediately solve all problems - even problems that are already formulated as number-crunching problems! | |||
::You're sort of skipping the step where a crew of bio-/genetico-/computer-/software-/electronics-engineers take the primitive state of understanding of human neurology, and translate it into an engineering schematic for the hardware and software of the computer of 2050. To do this, we need several key accomplishments - first, we need to really ''really'' understand the biology behind the brain. How much do we have to replicate and simulate? Individual cells? Neural blocks? Neural connectivity schemes? Or maybe just a "low-pass filtered" version of some kind of psychoneural model. For all we know, we might need to simulate every neuron's intricate internal cellular chemistry, down to the femto-mole concentrations of neurotransmitters - or worse, we might need to simulate the genetic code and protein folding arrangement. We don't even ''know'' what we need to simulate, because the best efforts of a hundred years of psychology and neuroscience still haven't answered the basic questions about ''what exactly a thought is made of.'' | |||
::Once we have the elaborate biology of brain function worked out, we then have the arduous task of generalizing it (so that it applies equally well to all human brains, not just a few test cases). The ] has shown us that this is non-trivial. (And, they only have some 4 billion "bits" worth of information! The whole human genome for one individual fits uncompressed on a DVD-R!) I can't really comprehend how much "state" you need to save if you want to recreate the ] that is a 45-year old human - there are hundreds of thousands of words, millions of sentences, who knows how to count how many images, sounds, sensory perceptions - all stored in the brain. What if there is a different packing format for every individual? You might have to start with a physics/chemistry simulator of the basic genetic code, and "press play" to see how the neuro-chemistry unfolds, given those sets of genes; and then you have to generate an custom-built interpreter for that individual's mind. | |||
::Now mainstreaming this so that every person can afford this technology is the next challenge. Imagine the issues surrounding reliability and stability. When you have (as SteveBaker predicted) a trillion individuals, what sort of bit-error-rate is acceptable? What mean-time-between-failure is acceptable for a project with a million-year lifespan? What tradeoffs in reliability are acceptable if it means that we can mass-produce this technology and allow more people to store their brains (albeit with more risks?) Thus ensues a complex moral/ethical debate. | |||
::I don't know if we have 25 or 50 years before the technology is available. I think it's so difficult to guess because we only have half of the technology (the computer-side) in a form which we can quantize and measure. The biology, neurology, and psychology is so far from mature, that it could be centuries - or never - before it's ready. We don't even know. For all our best guesses, we might have already surpassed the human cognitive ability with a mainstream computer - but without the software to emulate human behavior, we can't run a comparative benchmark suite. Most of the time, when I evaluate a nifty new image recognition program or semantic natural language processor, it doesn't require a hardware upgrade - but new abilities are granted to my ] ]. | |||
::Anyway, we'll see what the future holds. ] (]) 03:47, 15 June 2009 (UTC) | |||
:::'''But what about software?''' | |||
:::'''You're sort of skipping the step where a crew of bio-/genetico-/computer-/software-/electronics-engineers take the primitive state of understanding of human neurology, and translate it into an engineering schematic for the hardware and software of the computer of 2050.''' | |||
::::Well, the 2035 estimate assumes that present neural network simulation software would be employed to completely brute-force simulate the brain by replicating the actions of every single neuron. Biologists understand what an individual neuron does - you apply these stimulii - some time later, it fires or not and some signals head outwards...there is some recovery curve or other. Sure there will be questions of blood flow and such like - but our brains seem pretty resiliant to changes in those kinds of parameters. There would presumably need to be careful measurement of the performance of various kinds of neuron - but it's not that tough. Doubtless, advances in understanding the brain at the middle-levels (higher than "neuron" but lower than "the frontal lobe does this and the temporal lobe does that") would result in massive simplifications in software and reductions in hardware - but the brute-force approach ought to work - and it's easy to crunch the math to predict when we might get there. | |||
:::'''I can't really comprehend how much "state" you need to save if you want to recreate the ] that is a 45-year old human - there are hundreds of thousands of words, millions of sentences, who knows how to count how many images, sounds, sensory perceptions - all stored in the brain.''' | |||
::::Well, we know how many neurons there are - and how many connections each one has to it's neighbours. That tells you how much storage space you need for the network - and it's do-able with another 25 years of Moore's law expansion for a $1,000,000 hardware outlay. The rate at which neurons fire gives you a way to measure the amount of CPU time you need - it's huge - but it's very parallelisable...this allows us to use a lot of simple CPU's to provide the horsepower we need. It's do-able. | |||
:::'''What if there is a different packing format for every individual?''' | |||
::::The naive plan that I propose would entail simulating all of the connections between that individuals' neurons. That's all of the memories (although perhaps not the short-term memory) - all of the learned algorithms - the lot. We number all of the neurons - and for each one make a list of all the other neurons it connects to - the lengths of those connections and whether they are excitatory or inhibitory. This connection pattern is obviously unique to that individual - and will change day by day and hour by hour as memories are formed. We'd need to understand how new connections are formed. | |||
::: '''You might have to start with a physics/chemistry simulator of the basic genetic code, and "press play" to see how the neuro-chemistry unfolds, given those sets of genes; and then you have to generate an custom-built interpreter for that individual's mind.''' | |||
::::No - that's truly impossible...if it can't be done at the level of neurons - it's certainly impractical to look to yet lower levels. | |||
::: '''Imagine the issues surrounding reliability and stability. When you have (as SteveBaker predicted) a trillion individuals, what sort of bit-error-rate is acceptable?''' | |||
::::Real neurons are incredibly unreliable - they die of old age - diseases kill them. The brain has enough redundancy and plasticity to survive that. Our software simulation will have that same property. So small errors in these gargantuan computers would be survivable...perhaps even necessary to an accurate simulation! We need to occasionally make mistakes or we won't be human. However, wholesale failure of an entire computer could be serious - like a car wreck. Fortunately, we can make backup copies. You could have the exact state of your software brain backed up (onto "hard disk" - or whatever we have in 2050) on a regular basis. A "car wreck" scale of computer failure would result in you losing a few days of memories - but not much worse. | |||
:::'''Thus ensues a complex moral/ethical debate.''' | |||
::::I don't doubt the moral/ethical issues...they are exceedingly complex. However, we'll have a decade between the technology first seeming "real" before the first people will be using it - and to start with, it's going to take immense computing resources (perhaps a warehousefull) for "early adopters" - so only the very rich (or perhaps very accomplished/valuable) individuals will be able to have it. It'll be another decade after that before the average person would be able to afford it. That's plenty of time for the ethical issues to be worked out. | |||
::: ] (]) 04:29, 15 June 2009 (UTC) | |||
::::: I wonder how quickly the brains will have to be imaged and at what resolutions to extract the data with enough fidelity. ] (]) 06:31, 15 June 2009 (UTC) | |||
::::::That's a serious concern. I used to think that brains were like computers in that they had software and hardware - and (as with a computer) if you turn it off, the sofware just vanishes and everything the machine was doing at that instant was lost. However, brains are a bit more complicated. It seems that only short-term memory is represented as electrical signals zipping around some kind of closed-loop pathway - but everything that is more than a few minutes old is retained by physically rewiring the neurons. That being the case (and perhaps the jury is still out on this one), we'd only have to replicate the connectivity of the neurons to have the brain be able to 'reboot' successfully with only short-term memory loss. I don't know enough brain biology to be certain of that - but I believe it to be true. ] (]) 13:34, 15 June 2009 (UTC) | |||
:: ''Well, we know how many neurons there are - and how many connections each one has to it's neighbours. That tells you how much storage space you need for the network'' | |||
:: What about the key issue of ] (both ] and ])? Brains physically change. The brain you had this morning is not the same brain, in terms of the number of neurons and the connections each one has, that you have now. Neurons are born and die, they grow and shrink, they fire and wire. Its very likely it is those very changes that encodes the part of ''you'' - your memories, what you sensed, learned, forgot and how you felt - that was formed today. | |||
:: So even if we could scan a brain and somehow make sense of what all the neurons in the present synaptic configuration meant at that given moment, its likely that would only provide us with a snapshot in time, analogous to the information a screen-shot gives you about a movie. To understand the movie you need to watch frame after frame after frame, in the correct order. Likewise you might only be able to understand how the plasticity of the brain encodes the information present by doing scan after scan after scan and comparing the changes. But even if you scanned your brain every day from birth until the day of your death, would you still be able to understand its plasticity well enough to predict how it would wire in a completely novel situation? Say, for example, if you found yourself face to face with a great white shark while going for a dip in the sea, how could you possibly predict how your brain would wire in response to that. What frame of reference would you use? Going back to the movie analogy, consider a good ]. You can watch every single frame, and - up to that final scene - still not fully predict how it will end and be totally amazed when something unexpected is revealed. | |||
:: I predict we will be able to artificially model human brains one day, but never be able to recreate the unpredictable wonder that is human consciousness. Predictable movies are boring movies, so I'll enjoy every second of the original on the big screen and pass on the straight-to-DVD, cash-in sequel, thanks. ]<font color="black">e</font>] 06:17, 15 June 2009 (UTC) | |||
::: To be clear : You're proposing a paranormal aspect to human consciousness? ] (]) 06:31, 15 June 2009 (UTC) | |||
:::: No, I'm not. I'm suggesting a unpredictable aspect to human consciousness. ]<font color="black">e</font>] 07:10, 15 June 2009 (UTC) | |||
::::: But surely accurately modeling the brain would entail modeling even the unpredictable aspects? It's not as if our brains suddenly break the laws of physics every time we have an unexpected thought? ] (]) 17:53, 15 June 2009 (UTC) | |||
:::: '''What about the key issue of ] (both ] and ])? Brains physically change. The brain you had this morning is not the same brain, in terms of the number of neurons and the connections each one has, that you have now.''' | |||
:::::Our software simulation would have to allow dynamic reconnection of simulated neurons - but that's not a hard thing to do. Bear in mind that we already have software that simulates neural networks - they can easily accomodate on-the-fly rewiring...creation and deletion of neurons. I don't think this is an obstacle. Remember - I'm not talking about building some custom computer chip which mimics the wiring of your brain. I'm talking about using a general purpose computer so simulate those connections using tables of data. Naively: You'd have a big array of neuron data - with one entry for each neuron. Each neuron gets a number and inside its data structure would be a long list of the numbers of all of the other neurons it connects to (the synapses). When the neuron 'fires' you'd loop through the list of connections and apply an excitatory or inhibitory signal to each of the synapses - changing the data structure for the neurons you just changed the state of. Over and over again...very fast. Adding new connections to our software brain is a simple matter of changing the list of synapses that this neuron connects to. We would (of course) need to understand what causes new connections to form - at the neural level. That may take some biology that we don't understand yet - but we have 40 years to figure it out and when you consider the state of our understanding of the brain back in 1970, I think we have time. | |||
::::'''Say, for example, if you found yourself face to face with a great white shark while going for a dip in the sea, how could you possibly predict how your brain would wire in response to that.''' | |||
:::::Well, I presume that each neuron is mindlessly following a set of rules that some piece of biochemistry makes it follow. Perhaps the concentration of chemicals along a frequently used pathway results in a stimulus for neurons to grow their dendrites in that direction - resulting in shorter connections where the information flow is densest. I'm no biologist - so I don't know whether that's what happens - but the answer is one of chemistry and cell growth - not some complicated question about sharks and swimming. The neurons are just simple switching machines...not unlike the 'gates' in an electronic circuit - except for this rewiring business. | |||
:::: '''I predict we will be able to artificially model human brains one day, but never be able to recreate the unpredictable wonder that is human consciousness.''' | |||
:::::Unpredictability comes from complexity - as well as from randomness. Computer software can already be so complex as to seem unpredictable by any reasonable measure. Our "brain computer" would be similar in size and complexity to the entire Internet. Chaos theory can easily ensure that degree of seeming randomness because the processes we'd be simulating would suffer from 'sensitive dependence on initial conditions'. I'm sure that if we could do this at all, the person involved would be 100% convinced that they were still "alive". The extent to which we could make things seem "normal" for them is a tricky question...the immediate lack of the normal senses of sight, sound, touch, smell, taste, proprioception, etc would be a big problem. The simulated brain would need to learn how to connect to it's new senses...cameras, microphones, etc. We could perhaps plan for this in advance by planting electronic devices into the living brain which people would learn to use before death - and which could continue to function in precisely the same way in the simulated brain. We know that blind people can be given "sight" by connecting electronics directly to nerves in the retina - and even to other parts of the body. | |||
::::: 13:34, 15 June 2009 (UTC) | |||
I think the system identification problem is ''far'' tougher than the "system simulation" problem discussed above. I am curious to know what technology can possibly be used to "scan the brain" at a sufficient spatial, temporal and functional resolution. Is there one available today that simply needs to be "grown", or do we need to come up with something(s) qualitatively new ? ] (]) 07:38, 15 June 2009 (UTC) | |||
:I guess you could freeze the brain and take thin slices. If everything necessary to reproducing the brain survived such a process I don't suppose it would be too difficult to automate scanning the slices and generating an electronic replica. It sounds about possible with todays technology. Doing it without killing a person sounds a lot more difficult but it might be possible with nanomachines going around in the blood and reporting back to scanners around the head. There's also the possibility of replacing bits of the brain gradually with prosthesis so one day without a visible transition a person is all imlemented in silicon. ] (]) 11:56, 15 June 2009 (UTC) | |||
::I agree that the 'scanning' problem is a tough one. It's the hardest because (in a sense) the other part of the problem is already solved. We know we'll be able to build computers big enough - and we know that simulating something as fundamentally simple as a neuron can be done. We know that small errors in that simulation aren't critical because we know that the brain still functions after considerable damage, under changes in chemical environment and so forth. Scanning is hard because we haven't even started to look at that technology. | |||
::We have brain scanners that can look at large-scale structures - perhaps (I don't know) a really precise PET scanner or CT scanner could image such small structures given 40 years of technology advances. There is certainly plenty of research into ever more precise brain imaging...it's not unreasonable to assume that we could do that. Nanotechnology (meaning nanotechnology robots and computers) would certainly make the destructive imaging of brain very do-able - but I'm doubtful that this technology will come to fruition. | |||
::The idea of replacing the brain a bit at a time is an intriguing one. We know that you could chop out a sizeable chunk (say 1%) of someone's brain and that they'd still be "themselves" - able to think, function, etc. If we replaced that 1% with some computer circuitry representing a neural simulation of about the same number of neurons - and did so in such a way that the living brain could make use of it just as if it were biological neurons - then perhaps brain plasticity would result in that 1% being used for thinking and memory storage in the future. Do this 1% at a time and after 100 such operations - the person is living entirely inside the computer. My concern is that the rate at which this might happen could be too slow. If it took the person a year for their brain to adapt to the new circuitry (which seems reasonable) - it might take 100 years to replace the brain at 1% per year. You'd have to do it in small steps or else there might be massive memory loss at each stage. | |||
:: ] (]) 13:45, 15 June 2009 (UTC) | |||
::: For our purpose we need to be able to measure not only the structure of the neuronal network but also ] that is thought to encode memory, and perhaps other neuronal and synaptic characteristics. None of the technologies listed above are likely to be ever able to do this - the reason being a fundamental mismatch, not just technological barriers that can be resolved by throwing enough money at the problem. For instance the spatial resolution of a MR scanner is not only at (at least) 9-orders of magnitude worse than what would be required to visualize a neuron - the contrast mechanism (T1/T2 relaxation times in anatomical scans, or the ] in ]) are essentially bulk tissue phenomenon and hence will never be scalable down to a neuron resolution. The contrast mechanism in CT scans (X-ray attenuation coefficient) is even more limited, while PET measure the degree of absorption of the injected radionuclide, which again is a bulk effect. Finally, slicing and freeze drying a brain may preserve the structural properties of the tissue, but many of the functional properties are destroyed. | |||
::: In short, I think a fundamentally new enabling technology in order to identify and record the brain state. Personally I think most computer scientists underestimate the difficulty of this "]s" problem. I have no doubt that it will be eventually solved by but I'll be (pleasantly) shocked if it happens in 30-50 year time-frame, even in a laboratory setting. ] (]) 19:10, 15 June 2009 (UTC) | |||
= June 14 = | |||
== Betalgeuse + supernova == | |||
According to ], it is quite likely that the star Betelgeuse would go supernova within the next hundred years (if I infer properly from the numbers provided). According to the article, the star's rotation is not near the Earth, so there is no chance of damage to the ]. Two questions: | |||
# Would such an explosion cause problems for telecommunications and other electronic devices | |||
# If Earth ''were'' along Betelgeuse's axis, what would happen to the solar system and life on Earth? ] (]) 01:23, 14 June 2009 (UTC) | |||
I don't think it will cause any problems for electronic devices: after all, it's more than 500 light-years away, and besides, the Earth's ionosphere will probably block most of the radiation that ''does'' reach the Earth. Just my opinion though, I'm not a professional astrophysicist. | |||
] (]) 03:05, 14 June 2009 (UTC) | |||
:Re 2, according to ], a GRB pointing at Earth from a kiloparsec away could cause a mass extinction. Betelgeuse is a mere 200 parsecs away; I don't know how much additional damage this would cause. ] 03:15, 14 June 2009 (UTC) | |||
::I'm guessing a kiloparsec is 1000 parsecs? If so, and this one is only 200 parsecs, then it would probably be worse than the 1kiloparsec mass extinction prediction.]rew ] ] 09:59, 14 June 2009 (UTC) | |||
::: Couldn't it have already gone supernova, and we just will not detect that it did for a many years? ] (]) 13:24, 15 June 2009 (UTC) | |||
::::Correct. Since Betalgeuse is approxamately 650 light years away, we wouldnt know it exploded until ~650 years after that happened. ] (]) 19:51, 15 June 2009 (UTC) | |||
== Artificial breeding to save endangered species == | |||
Suppose you have a species that's on the brink of extinction. To save the species, all surviving members are gathered and artificially bred to boost the population. There's a problem, though — there's only 1 male among the surviving individuals. Is there an optimal pattern of breeding, if the goal is to increase the genetic diversity of the offspring? <span style="font-size: smaller;" class="autosigned">—Preceding ] comment added by ] (]) 01:41, 14 June 2009 (UTC)</span><!-- Template:UnsignedIP --> <!--Autosigned by SineBot--> | |||
:Put em in a cage, and let the dude get gangbanged. Jokes aside, the optimal breeding pattern is to put the male in a cage with as many females as he seems happy around. Add one female per day (or even per week) and observe the males attitude. When he starts to be aprehensive about the schedule time to add a female, stop adding them.]rew ] ] 03:57, 14 June 2009 (UTC) | |||
::If there is just one male left - then the breed is already gone. The lack of genetic diversity in subsequent generations would doom them. ] (]) 04:11, 14 June 2009 (UTC) | |||
:::{{fact}}. ] (]) 04:26, 14 June 2009 (UTC) | |||
::::I think there are many dog/cat breeds that came from one breeding pair, so i also think that having only one male dooming the species needs a source. The only certain limit to diversity would be in the Y chromosome, no?]] 06:51, 14 June 2009 (UTC) | |||
:: You probably want to think that one through a little more, Steve. You are incorrect, and there are plenty of practical examples to demonstrate that. One is ]. These mice are for all intents and purposes ] - there is negligible genetic diversity among the entire strain - and yet are far from "doomed", indeed they continue to survive quite happily when bred together for over 200 generations. Note these mice are purposely '']'', but if you were trying to repopulate a species, you would purposely '']'' to maintain as much genetic diversity as possible. You would probably want to have enough fertile females that are genetically diverse to ensure you avoided creating too much of an artificial ]. From this harem mating with your single male, agnate half-brother/half-sister pairings would have only a 12.5% ], no big deal. You would then ] the offspring from the subsequent generations and set up crosses to minimize homozygosity. With careful management, the genetic diversity of your new population will correlate with the genetic diversity of your starting population, irrespective that all but one were the same sex. | |||
:: Thus if certain other conditions are met, then a single male could be perfectly sufficient to repopulate a species. But even if you only had one male and one female, with a little bit of luck you could still propagate the species (albeit the repopulated species will be a not quite the same as it was before, for example BALB/c mice are noticeably different from a mouse you might catch living in your house, but they are all still mice). ]<font color="black">e</font>] 08:18, 14 June 2009 (UTC) | |||
And who are we to play god? Barring predators, (which I'm assuming you wouldn't be dumb enough to include predators in your cage) I think the animals themselves would best be able to choose a proper mate. They know better than we do what traits they "like", i.e. traits that are benificial to survival. If you put a male lab in the same cage with a healthy female and a crippled female, he would mate with the healthy female first, and most often. Again, I say just put em all in a big cage and let em have an orgy.]rew ] ] 09:33, 14 June 2009 (UTC) | |||
:Ummm... you're slightly missing the point here, Drew. It isn't really about how to mate the one remaining male but how to manage the subsequent matings between half-sib offspring. Rockpocket's answer is best. What is being described is the reverse of what mouse researchers use to generate ] mouse strains by using genetic markers to select the "best" pairings (i.e. between half-sibs, cousins, second-cousins, etc. that have the least amount of genetic information in common), and thus to increase the genetic diversity of the resulting population as much as possible. --- ] (]) 10:35, 14 June 2009 (UTC) | |||
::And I say let them choose. Diversity will happen over time, they don't have to be diverse right from the start. | |||
:::"let em have an orgy" is not how artificial breeding is done. ] (]) 11:24, 14 June 2009 (UTC) | |||
:::Mate selection works statistically and on an evolutionary time-scale. With only one male left to choose for himself, there is no way to be certain he would mate with all the females to ensure genetic diversity, nor that he would choose the most "fit" for survival or reproductive success. If he did this 51% of the time, this would be enough for natural selection to work, but you cannot apply a statistical outcome to an isolated case. If he is asexual or monogamous or gay, you have just doomed the species for a philosophical stand! In fact for monogamous species, leaving them to an orgy would be the worst idea.]] 12:51, 14 June 2009 (UTC) | |||
::It probably is a good idea to let the predators amongst them once their numbers are a bit up. Otherwise natural selection would start choosing them for a cage environment. ] (]) 11:51, 14 June 2009 (UTC) | |||
:::But as evolutionary changes take many many generations, this would seem a very far off and unlikely problem compared to preserving genetic divirsity, without which disease is likely to kill them all far more quickly.]] 12:57, 14 June 2009 (UTC) | |||
== Critical velocities for Lockheed Electra 10-E? == | |||
Hello everyone, I'd like to know the stall speed and Vmc (minimum control speed, the lowest airspeed at which the pilot can maintain lateral control in case of engine failure) for the ] with a 3,600 lb. overload, as was the case with ]'s plane on takeoff from ], New Guinea. I'm writing a song about Amelia, and I need those numbers to see if one of the lines is realistic or not (I've already been forced to take some liberties with the facts, and I don't want to do that any more than I have to). How I came up with 3,600 lbs of overload: ~7,100 lbs. airframe/engines/equipment + 6,600 lbs. (1,100 gal. * 6 lbs/gal) fuel + ~130 lbs. pilot (tall, thin woman) + ~170 lbs. navigator + ~100 lbs. or so of navigational equipment = ~14,100 lbs. gross weight; 14,100 - 10,500 max. takeoff weight = 3,600 lbs. overload. What I really want to know is, given these numbers, would it be possible to fly below Vmc without stalling out (not that anyone would choose to)? Also, I would really appreciate it if you could also calculate the speed that a Lockheed Electra 10-E with a 3,600 lb. overload would achieve after a takeoff run of 3,000 feet on a rough gravel runway at full power (1,100 hp combined power for both engines); would it be greater than Vmc, or less than Vmc? Thanks a lot! | |||
Oh, and by the way, does Vmc change significantly with the load? I'm not a professional pilot, but I know that stall speed certainly increases with the load, does Vmc do the same? | |||
] (]) 02:57, 14 June 2009 (UTC) | |||
:Judging by the time that Amelia would have realized that she had overflown Howland, it is quite conceivable that most of the fuel would have been burnt off. Some of the Itasca personnel were quite sure that her radio messages coming in loud and clear put her in the vicinity of the island. If the next hour involved a "crawl" back over navigation tracks, conceivably, Amelia would have reduced speed to above stalling speed: 65 kts/120 km/h (clean). If she let down flaps, stalling speed would be reduced slightly by approximately 5 kts. She would not have put down the gear. As to actual Vmc of the Lockheed 10 Electra, it is comparable to the PA-30 Twin Comanche, where the number is 90 mph and it's the left engine that's critical. Observers on Lae saw the Electra stagger into the air with its overloaded condition, so that the Vmc was probably adjusted to consider airframe configuration, accessories, air density and loading which all make a difference. FWiW ] (]) 04:07, 14 June 2009 (UTC). | |||
::I would be quite surprised if it were possible to figure this out. Finding data like this on a fairly obscure antique is going to be tough - but much, much worse - Earhart had heavily modified her plane - so the odds are very good that the details of it's performance weren't caefully measured even at the time. Since the plane itself was evidently lost in whatever befell Earhart - we'll probably never know. ] (]) 04:09, 14 June 2009 (UTC) | |||
Bzuk -- thanks for the info about Vmc, it was very helpful of you. As for the stall speed, I was actually asking for the stall speed ''on takeoff'' with all that extra weight, would it still be so much lower than Vmc or would the overload bring it closer to Vmc? (BTW, you can forget that I ever asked about the airspeed after the 3,000 foot takeoff run, I can now calculate it with the data that I have.) Clear skies to you, and best regards! | |||
] (]) 05:20, 14 June 2009 (UTC) | |||
I've done the calculations just this morning and came up with the following (''very'' approximate) numbers: | |||
--Stall speed (clean, overloaded): Depending on whether 65 kts. is the stall speed at empty weight or maximum takeoff weight, stall speed at 14,100 lbs. total weight will be either 72-74 kts. (if 65 kts. at maximum takeoff weight) or around 90 kts. (if 65 kts. at empty weight). | |||
--Vmc was probably slightly higher than 90 kts. due to the hot weather conditions (between 90-95 kts). | |||
--The actual velocity at the moment of takeoff is only a ballpark figure because I was only able to get a very rough estimate of rolling resistance, but the number I got was somewhere around 90 kts (FWIW). In other words, AE was ''literally'' threading the needle in terms of the plane's performance envelope: one wrong move on her part could easily have led either to a departure stall, or to an uncontrolled descent to the ocean's surface, or to a loss of lateral control. Just the fact that she even made it off that short, rough runway with such a big overload proves what a good pilot she was by that time. | |||
Well anyway, thank you very much for the info. Clear skies to you, and best regards! | |||
] (]) 00:56, 15 June 2009 (UTC) | |||
== Weed seeds and compost == | |||
Where I live, a yard waste service carries away all the grass clippings and tree cuttings and food waste that I care to throw into our yard waste bin, and it's all mixed together with the neighbors' yard waste and at some 'central' location is turned into ], at which point I believe it's sold to local nurseries and garden supply stores. Surely my yard waste contains thousands of seeds of ]s, and I'm sure the inferior yard waste of my unscrupulous neighbors is teeming with seeds of some of those noxious weeds that are impossible to get rid of once you've got them. My question: Is there some process (natural or otherwise) that occurs in composting that wrecks the seeds? Or am I dooming myself to additional hours of backbreaking labor every weekend by using compost? ] (]) 04:49, 14 June 2009 (UTC) | |||
:Depends on the method used to make the compost. If they burn it and use the ashes, the seeds are toast (pardon the pun). If, on the other hand, they mulch, decay, or use any other method of composting, the seeds would likely survive. Especially through mulching. | |||
:This is also a problem when you mow your yard. If you simply mow over the weeds, you spread the seeds, and infect more of your yard with weeds. | |||
:My theory (I haven't tried it yet) would be to comb over every inch of your yard, plucking as many weeds as possible. Let it grow for awhile. This makes the weeds much easier to find as they grow a lot taller than grass. Pick more weeds. Now mow, and repeat the process. Combine with any form of weedicides (pardon the term) that you want. If you use compost, burn it and spread the ashes instead of just spreading the live compost. This will kill everything in the compost, but the nutrients are still there.]rew ] ] 04:58, 14 June 2009 (UTC) | |||
:If you care about runoff (You probably should) skip the herbicide step. Be careful about using ashes in your garden. It is true that ashes contain a large part of the original nutrients, but indiscriminate use of ashes can drastically influence the soil's PH which might end up hurting more than helping. ] (]) 05:27, 14 June 2009 (UTC) | |||
:Commercially produced compost heats the original materials to such a point that renders seeds useless. It's a bit early on a Sunday morning - I can't find the relevant reference yet...maybe someone can help out here? --] (]) 07:56, 14 June 2009 (UTC) | |||
::That depends on who is doing the composting, and where. For example, in hawaii we our local companies compost using the decaying method (letting the compost sit forever until it stinks. Well, thats what it seems like anyway, it's probably a lot more scientific). Some also simply mulch it and resell it. Even traditionally heated compost has been known to have still active seeds (granted, not nearly the numbers of other methods).]rew ] ] 09:00, 14 June 2009 (UTC) | |||
:Decomposition bacteria can work at temperatures over 60 degrees that will kill most seeds, and they produce the heat as they consume the material. ] (]) 09:20, 14 June 2009 (UTC) | |||
::]I don't have a source on hand, but yes, if the compost is properly aerated over a period of time the thermophyllic bacteria can raise the temperatures to 65 C, which kills all but very large seeds, as well as many fungal spores and harmful bacteria (such as salmonella, which can be in animal manures). | |||
::As far as the ''process'' involved, the normal aerobic soil bacteria raise the heat in the pile to a certain temperature as a byproduct of their metabolism (just like you get hot when exercising), after which the thermophyllic (heat-loving) bacteria are able to function. The thermopyllic bacteria then take over, raising the temperature much higher and essentially ] the pile. The ] standards for certified compost in the US require the pile to be kept hot (131-170 F) for at least 15 days, turning every 3 days to ensure adequate oxygen (anaerobic bacteria do not produce as much heat). --] | <sup>]</sup> 09:46, 14 June 2009 (UTC) | |||
:::Great answers - thank you all. (I fixed the NOP link above.) ] (]) 16:37, 14 June 2009 (UTC) | |||
== Volume of all the water on earth == | |||
This is really bothering me. When I Googled the question "What is the volume of all the water on Earth, I see a lot of different references. The vast majority seem to state that the volume of all the water on Earth is described as being about 1.3 billion kilometers. Now when I visualize 1.3 billion kilometers, I visualize a cube measuring 1.2 billion kilometers wide, 1.3 billion kilometers in width, and 1.3 billion kilometers high. If I am correct, the Earth itself is no where near 1.3 billion kilometers wide, and since our sun is something like 93 million miles from the Earth, this cube of 1.3 billion kilometers would exceed the distance by 11 or 12 times. What am I missing here? | |||
Thank you for all your help, | |||
Jim Lyle <span style="font-size: smaller;" class="autosigned">—Preceding ] comment added by ] (]) 04:55, 14 June 2009 (UTC)</span><!-- Template:UnsignedIP --> <!--Autosigned by SineBot--> | |||
:That is not what 1.3 billion cubic kilometres means. It means 1.3 billion lots of one cubic kilometre, where one cubic kilometre is a cube 1 kilometre to each side. Thus the amount of water on earth is equivalent to a cube about 1090km to each side. ] 05:00, 14 June 2009 (UTC) | |||
::Where <math>1090 \approx \sqrt{1.3 \times 10^9}</math>. —<strong>]</strong>] 05:09, 14 June 2009 (UTC) | |||
:for comparison, the volume of the earth is about 1080 billion cubic kilometers. ] (]) 05:16, 14 June 2009 (UTC) | |||
:::(EC)I think your numbers are rigt, but your explanation is basically affirming what he says. If you want to visualise it as "one giant cube" take the cube root of 1.3 bill which is roughly 1091. So each side of your cube would be around 1091Km's. Make it alittle simpler to understand?]rew ] ] 05:18, 14 June 2009 (UTC) | |||
::::I would be surprised to see any reference, let alone "a lot of different references", that quantify a volume in kilometers because that is nonsense. ] (]) 11:15, 14 June 2009 (UTC) | |||
:::::When I Googled "What is the volume of all the water on Earth" (without quotes) all of the results seem to give the answer in cubic metres (except the first one, which gives the area). Interestingly, the fifth result is exactly the same post on Yahoo answers and Googling with quotes give only that question on Yahoo. ] (]) 11:32, 14 June 2009 (UTC) | |||
:I know the answer is already posted, but this kind of question is perfect for the new search engine ]. http://www05.wolframalpha.com/input/?i=volume+of+all+the+water. --] (]) 13:28, 14 June 2009 (UTC) | |||
::Exactly what I thought but WolframAlphaing "all water", "earth water", etc etc gave me no answer, seems to be picky about exactly how you phrase your question. ] (]) 11:25, 15 June 2009 (UTC) | |||
== Is an unicellular organism a tautology? == | |||
This question has always popped up in my mind whenever someone speaks about unicellular organisms. Since it is only made up of one cell, what differs such an organism from a single cell? If there is no difference, why do we have two names for one thing in the same expression, i.e. why do we use this obvious tautology? // ] (]) 06:30, 14 June 2009 (UTC) | |||
:The distinction is more between unicellular and multicellular organisms (like, say, humans). A multicellular organism is made up of lots of cells, which aren't organisms in their own right, hence there is no tautology. ]<small>(])</small> 08:01, 14 June 2009 (UTC) | |||
:: Further to that, some cells from multicellular organisms can "live" as single cells - ], for example - but these are not considered an organism (at least not by most people). This is quite an important distinction that can be made using the apparent tautology ]<font color="black">e</font>] 08:55, 14 June 2009 (UTC) | |||
:::<small>Wow, cool article. Weird. ] (]) 16:35, 14 June 2009 (UTC)</small> | |||
::::Yea, some organisms have billions of cells, some have millions, some have hundreds, and some have 1 cell. ] (]) 11:19, 15 June 2009 (UTC) | |||
== bioplastics == | |||
what are the properties or components or chemicals are used for obtaining good quality of starch from maize corn? | |||
After seperation of starch from corn which are other material or chemicals are added to create biopolymer? | |||
What are the processes or method for making bioplastic from maize corn? <small><span class="autosigned">—Preceding ] comment added by ] (] • ]) 07:27, 14 June 2009 (UTC)</span></small><!-- Template:Unsigned --> <!--Autosigned by SineBot--> | |||
:Have you seen ] and ]? ] seems to be an important element of some corn-based bioplastic. , from ], is available in Portuguese; . | |||
== Metric expansion of space == | |||
Can someone explain what metric expansion of space ''entails'' in the following situation? Say you have a crystal lattice in which atoms are regularly spaced. Since the crystal lattice is embedded in space, does an expansion of space cause the inter-atom distance to increase? If a large crystal is shaped such that a light pulse emitted from a source embedded in the crystal will later come back to the source, will expansion of space manifest as an increase in the time it takes a light pulse to come back to the same point? <span style="font-size: smaller;" class="autosigned">—Preceding ] comment added by ] (]) 12:09, 14 June 2009 (UTC)</span><!-- Template:UnsignedIP --> <!--Autosigned by SineBot--> | |||
:No. The expansion isn't a force pushing things apart, it's just leftover inertia from the inflationary epoch. The article "metric expansion of space" should be renamed to something more accurate like "expansion of the universe". The cosmological constant (if there really is one) is an exception; you can think of it as a slight modification to the self-gravitation of the object. The force is smaller than in a universe without the cosmological constant by a fractional amount roughly equal to the density of the crystal divided by 10<sup>-29</sup> g/cm<sup>3</sup>. This is well outside the bounds of detectability, of course. (I don't know if we can even detect the self-gravitation, much less a decrease of one part in 10<sup>29</sup>.) -- ] (]) 13:12, 14 June 2009 (UTC) | |||
:(EC) May I assume you are talking about ]? If that's the case, the answer is no, that expansion does not entail the expansion of objects like a crystal latice within space. ] (]) 13:15, 14 June 2009 (UTC) | |||
:Space is stretching - but over small distances, the speed of that expansion is negligable. The forces between the atoms in the crystal can easily keep the lattice together. It's only over vast distances when the force of gravity is so gentle that things on the scale of galaxies can be moved further apart. ] (]) 13:48, 14 June 2009 (UTC) | |||
:The reason your lattice stays together is because of strong electron bonds. Those are strong enough the offset the very small counter-force of the expansion of space. On massive, massive scales, things like galaxies will be ''moved'' by the expansion of space, but not pulled apart. Common example is an ant on a balloon—the ant doesn't rip apart, because the forces that hold the ant together are much stronger than the forces causing the surface of the balloon to stretch. If you had a lot of ants on the surface of a very big balloon (a problematic endeavor) and you inflated it, each ant would perceive the other ants moving away from them, but no ants would be pulled apart. --] (]) 13:53, 14 June 2009 (UTC) | |||
::No, the Hubble expansion is not a force. It doesn't have the right units to be a force—it's a velocity per unit distance, not an acceleration. It is not pushing the lattice apart, not even by a tiny amount. The expansion rate is changing, and those changes are due to forces which do also act on the lattice, namely self-gravitation and cosmological repulsion. Of those, self-gravitation dominates overwhelmingly in ordinary circumstances—it's roughly 10<sup>29</sup> times larger for a substance with the density of water. So the net effect of the forces implicated in universal expansion is to ''decrease'' the interatomic distance of a crystal by a very small amount. -- ] (]) 14:18, 14 June 2009 (UTC) | |||
:::I'm not using force here in a technical sense. I'm just trying to conjure up an image for them of the relative ability of things to affect the position of things. One sees a galaxy zooming away from us—it's not actually zooming in the sense of being pushed, but it is easier to make sense of as an analogy to a pushing force. --] (]) 14:23, 14 June 2009 (UTC) | |||
::::I'm pretty sure the OP understood that an outward force/push/pull on the crystal would just cause a change in the equilibrium lattice spacing, not a gradual expansion. Nonetheless there is no such effect. An ant on a stretching rubber sheet would find its legs being forced apart, but nothing analogous happens as the universe expands. -- ] (]) 14:40, 14 June 2009 (UTC) | |||
== Is it possible to deliberately lose weight without feeling hungry? == | |||
Or is hunger a necessary part of dieting, for it to be effective? ] (]) 12:27, 14 June 2009 (UTC) | |||
::Eating high volume and fibrous food can fill you up enough to not feel hungry, while easily having low enough calories to cause weight loss. Alternately, a normal varied diet can be eaten and weight still loss if doing enough excercise. Imo, people don't fail at sensible healthy diets because they are hungry, but becasue they crave certain comfort foods or are used to over-eating. They may intepret that as hunger, but it isn't really.]] 12:35, 14 June 2009 (UTC) | |||
:::Unless you live nearby, no amount of dieting will ever make you feel Hungary. You may starve if you try to hard though.]rew ] ] 02:43, 15 June 2009 (UTC) | |||
::::That is why he said hungry, not hungary. Incidentally if this is for yourself your local GP will happily dole out diet advice, and that might be a good idea if you live in a country with free healthcare. ] (]) 10:06, 15 June 2009 (UTC) | |||
:::::No, it originally said hungary. Check the history.]rew ] ] 11:03, 15 June 2009 (UTC) | |||
::::::It isn't usually possible to lose weight without feeling hungry except by getting some sort of disease, but it's possible to lose weight without depriving yourself of food, by exercising in the right way. If you can work up to running five miles a day, or go on a long backpacking trip, you will probably lose weight even if you eat as much as you want to. ] (]) 16:08, 15 June 2009 (UTC) | |||
== How amount of UV in sunlight differs between time of day, season, and various places in north or south Britain == | |||
I'm looking for some figures for how the amount of damaging UV varies along the above dimensions please. As well as being affected by latitude, the amount might be affected by the amount of cloud cover, although I have heard that cloud cover makes little difference. ] (]) 12:52, 14 June 2009 (UTC) | |||
:There are really three things to take into account: | |||
:* The amount of sunlight intercepted by the earth per square meter of the surface is proportional to the sine of the latitude - so there is less sunlight at more northerly latitudes. | |||
:* At more northerly latitudes, the light has to pass through more air - so more of it gets scattered. You can calculate that using the ]. | |||
:* As you say: The amount of cloud and humidity in the atmosphere also has an effect (although not so large as the others) - and differing weather patterns between the northern and southern parts of Britain might therefore make a difference. | |||
: ] (]) 13:43, 14 June 2009 (UTC) | |||
== Thermodynamics chemistry == | |||
Van't Hoff reaction isotherm and van't Hoff equation are different ? | |||
If it is how can I deduce van't Hoff equation from van't Hoff reaction isotherm?] (]) 15:05, 14 June 2009 (UTC) | |||
:Unfortunately, we don't seem to have an article on the ], but Googling it turns up several sites (,, , (page 269 in the last)) From these I surmise that the van 't Hoff reaction isotherm refers to the equation giving the free energy change for a reaction system which is not in equilibrium: <math> \Delta G = -RT \, ln \, K_{eq} + RT \, ln \, Q </math>, where Q has the same form as the equilibrium constant but uses the current, non-equilibrium ] (concentrations). If you define the first term on the right hand side as <math>\Delta G^o</math>, and use the relation <math> \Delta G^o = \Delta H^o - T\Delta S^o </math>, you can get the last equation on the ] page. If you then take the derivative with respect to T (or 1/T), you obtain the first (or second) equation on that page. -- ] (]) 19:26, 14 June 2009 (UTC) | |||
== Household science-themed activities for 18-26 year olds == | |||
Hi guys, this week I need to run a Science themed night for my Rover crew (probably about a dozen or fewer 18-26 year olds) and I'm pretty stuck for ideas. What kind of stuff can I do cheaply and not-too-destructively, that will demonstrate interesting or surprising science ideas? "Wow" factor is a definite plus, and preferably it should be something that they themselves can participate in rather than a long sequence of demonstrations. ] <small>(] | ])</small> 15:51, 14 June 2009 (UTC) | |||
:The guy who made the Periodic Table Table writes (or wrote) a column for Popular Science about spectacular experiments you shouldn't do because they're probably too dangerous. As a public service, I will point you to anyway. ] (]) 16:33, 14 June 2009 (UTC) | |||
: I'm collecting those sorts of ideas - so far, I have three good ones that meet your criteria. They all require only things you'd find around the house - all three seem impossible at first sight - all three work very well - none of them need cost you a penny - none are destructive: | |||
:* Measuring the thickness of a human hair using a laserpointer and a tape measure. | |||
:* Measuring the speed of light using chocolate chips and a microwave oven. | |||
:* Calculating PI with a box of toothpicks. | |||
: Details are on my personal Wiki: http://www.sjbaker.org/index.php?title=Measuring_hard_things_with_easy_experiments - there are links to the places where I found them - understanding WHY these experiments work is the interesting part. | |||
: ] (]) 18:19, 14 June 2009 (UTC) | |||
:I always thought it was pretty cool to invert a bowl of slaked cornflour (that's cornstarch in the US, and if it's slaked it's mixed with water to form a smooth paste - a bit more runny than glue) over someone's head. If you do it fast enough it sets. You can also make sure it sets by banging the bowl on the table first. I think it's something to do with it being a colloidal solution. It should appeal to the child in every young adult - well you could always get them to bet on the outcome! --] (]) 18:54, 14 June 2009 (UTC) | |||
::Yeah - that's cool. Check out ] for more cool/weird fluids and see ] for more about cornstarch & water. ] (]) 19:46, 14 June 2009 (UTC) | |||
:::: You from peas or ]s (the fruit, not ] or the ] - though come to think of it - if you could find an ] willing to donate a cheek swab, you could do a cool comparison between the DNA of the fruit and the person to demonstrate the ubiquity of DNA as the basis for life). ]<font color="black">e</font>] 21:05, 14 June 2009 (UTC) | |||
::::::The article you link from says that you need a lot of material to extract a visible amount of DNA from using this technique - so a cheek-swab isn't going to cut it. It's certainly cool that you can extract DNA using such simple methods though. The end of the experiment seems like a bit of an anticlimax...so you've got this white stringy stuff...now what? It seems like you should be able to create an evil clone army with it or something! ] (]) 14:41, 15 June 2009 (UTC) | |||
::::: Lacking the "science factor", but high in the "wow factor", get an old microwave and put stuff in it - CDs, lightbulbs, tinfoil, candles. '''Please note that this could be very dangerous''', I don't know, I just know it looks cool, and when I've done it, the microwave hasn't exploded. ] (]) 11:15, 15 June 2009 (UTC) | |||
:::::: Grapes cut '''nearly''' in half and splayed out flat with just a thin piece of skin connecting the pieces, produce an impressive result when microwaved. If you're going to microwave a CD - don't use a recordable one - it needs to be a prerecorded disk to get the most impressive results. But PLEASE make sure everyone wears eye protection - and don't be surprised if it wrecks your microwave oven. ] (]) 14:41, 15 June 2009 (UTC) | |||
== Falling from a motorcycle == | |||
If I fall from a motorcycle, does it really matter at what speed I am? Provided I don't hit a tree or other similar obstacle, my speed is parallel to the floor, so not that relevant, right?--] ] 17:33, 14 June 2009 (UTC) | |||
:I know ''nothing'' about this subject, but friction would increase with speed. It would be the difference between scraping a layer or two of skin and scraping off a considerable amount of muscle, wouldn't it? Plus, the more momentum you have the more likely you are to start rolling uncontrollably at high sped, risking sudden impacts and thus broken bones, etc. ] (]) 17:50, 14 June 2009 (UTC) | |||
: What do you mean "fall from a motorcycle"? Are we just talking about letting go of the handlebars and somehow just tumbling off the bike? I am not a biker, but I think that sort of accident is rare. ] (]) 18:12, 14 June 2009 (UTC) | |||
:The problem is this: When you're on the motorbike - your body has a certain amount of kinetic energy, which is proportional to the SQUARE of your speed. If you drive twice as fast you have four times the amount of energy. At 100mph you have 100 times more kinetic energy than at 10mph. When you fall off - bounce around a bit - then stop, that energy has to be dissipated somehow. How does it dissipate? Well, friction turns some of it to heat - the rest is consumed in ripping, smashing, tearing and otherwise breaking you and whatever you're still attached to. Certainly, the more slowly that energy is dissipated, the better. Hitting a tree will dissipate all of it in a tiny fraction of a second...sliding smoothely along the road will dissipate it much more slowly. However, what we can say is that it's not good! As for rolling - the frictional force of your body against the road is pretty much the same, no matter your speed - which means it'll take longer to come to a stop if you're going faster. But your speed is higher - so the rotational torque is higher too. Hence, you'll certainly be more inclined to roll. The faster you roll, the more centrifugal force is going to throw your limbs outwards - which means they'll be more inclined to get broken. | |||
:It's safe to say that the faster you're going when you fall off - the worse the consequences...and because (in the end) it's all about dissipating energy - it's probably going to be four times worse at twice the speed. | |||
: ] (]) 18:46, 14 June 2009 (UTC) | |||
: I think I may be the first biker to comment on this, and its not a very scientific answer. Whatever speed you fall off at, it will hurt. If you're not wearing appropriate safety gear (and I mean leathers or kevlar) your speed parrellel to the floor is what I'd be most worried about. Denim will not protect mate, you can fall over wearing jeans and tear a whole in them. The wavey hand science above is all correct though. Dont it into your head that spead doesn't matter, I can testify to the fact that it doest notm and that falling off ALWAYS hurts. If you want to learn to ride fast safely, there are a whole host of advanced rider courses.] (]) 19:47, 14 June 2009 (UTC) | |||
: If you see racing motorcyclists fall, you do indeed see them slide along the ground (a very considerable way); remarkably often they are only slightly bruised. So it's possible, but it's a difficult thing to achieve. In their favour, the professionals have: a) very long runoffs, so plenty of room to scrape down to zero without hitting a telephone pole b) really good suits and other safety gear c) they often ''put'' the bike down; better to be doing a slide along the ground than pinwheeling around after a collision; d) they ''know'' how to fall (because they've all done it a lot); they know how to get onto their back (where the spine protector will eat the damage) and to avoid rolling (which, as Steve says, will break limbs). And of course they almost always come off at corners, when the speed is relatively low and they're already virtually on the ground anyway. If it was only a ''bit'' safer you could get a pretty good new sport out of it: fire bikers out of a gun and watch them slide along the tarmac - they get points for style and for tricks. ] (]) 20:17, 14 June 2009 (UTC) | |||
::Speaking as someone who ''has'' fallen off a motorbike I can confirm that; | |||
::# it does definitely hurt | |||
::# there is an awful lot of damage (lost skin and flesh) even at low speed if you are stupid enough not to wear any safety equipment (tee-shirt and sandals don't count) | |||
::# (in the context of this post) I am stupid | |||
::# it probably does get worse to ''v''<sup>2</sup> but I'm not going to experiment | |||
::] 21:33, 14 June 2009 (UTC) | |||
:Of course your speed matters. It's sort of appalling that this has not been beaten in to your head, as a motorcycle driver. Because a motorcycle driver is categorically the least safe driver (both by his/her own actions, and because of some unforgiving physics), it is ''extremely important that you understand how dangerous speeding is''. | |||
:First, '''if you speed, you are more likely to be involved in a crash.''' | |||
:Here is a well-researched report regarding the relative risk of fatal crash as a function of the speed you are driving: ''''. "In a 60 km/h speed limit area, the risk of involvement in a casualty crash doubles with each 5 km/h increase in travelling speed above 60 km/h." (In units you may be more familiar with - at 45 mph, '''.''' | |||
:Second, '''if you are involved in a crash, your speed will be the primary predictive factor in the severity of injuries and death that you will sustain''' yourself and inflict on other drivers. As a motorcyclist, your statistics are unfortunately weighted towards inflicting death and injury on yourself, rather than other vehicles. As a motorcyclist, you will be than an automobile driver. Speeding on a motorcycle is correlated with fatal accidents 1.5x as much as it is for automobiles. If you are a driver of a "" (typically, one which you ride leaning forward, with a faster top speed and acceleration than a Touring or Cruiser bike), you are in the category of "most statistically likely to die" of any motor vehicle operator, passenger, or bystander. | |||
:When you crash, your speed will be the primary parameter of the impact. (This is more important than incidence angle for many reasons). There is the simple matter of kinetic energy to dissipate - which increases as velocity squared. As mentioned above, if you drive twice as fast, you will have four times as much energy. | |||
:If you intend to crash your motorcycle '''at 75 miles per hour''', a human body is , because the hard are negligible (to engineering approximation). The fact that you impact the ground parallel or perpendicular is pretty irrelevant, because the collision is ], which means that your body will deform on impact to dissipate the energy (so it doesn't really help if you slide or bounce). Because you are not in an automobile, you will not have an airbag, safety belt, ], or a soft-plastic-dashboard-with-rounded-corners-on-all-the-edges. This means that , so when you hit the pavement, it will not be at an optimal angle. You will not , so you will be in an uncontrolled position and orientation. If you survive impact at interstate speeds, you will be a statistical outlier. ] (]) 02:49, 15 June 2009 (UTC) | |||
::Okay, first, it's not uncommon for motorcycles to crash by hitting a slick spot and sliding, without hitting anything. If you are completely covered in leather and helmet, and the terrain is completely flat, and you don't try to stop yourself with your hands, and you don't get tangled up with the motorcycle, you are likely to slide without major damage even at high speed. But if you hit even a small obstacle or start tumbling, lots of nasty things can happen. ] (]) 15:54, 15 June 2009 (UTC) | |||
== Curvature of Space == | |||
Space is curved. Does the curve extend to form a circle? If so, does the curve exist in all directions to form a sphere? If that also is so, what is outside the sphere? Can it be said there is no outside? Where does the third dimension, in the everyday sense of the word, fit into this? – GlowWorm. | |||
:It is difficult to answer the question because "space" by definition is a void without form. That means no curves, no lines, nothing. The other stuff is just floating about in that space. If God loves us, or we love him enough, maybe some of it ''does'' form that complete loop. I hope so. Apparently a black hole could curve light in such a way that you can see its other side (as though you were hovering over England but could see bits of Australia and Antartica around the edges!) Nobody can say if the universe has an outside because, not only can we not see it's outer edges, we cannot even see that which is in our view (see ]). Dimensions as we know them are classed as three to help us with mathematical equations (up-down, left-right, in-out) but in ''reality'' all objects with mass ''are curved'', without linear form. No up-down, left-right, only across and in that across, only in one direction. You will not be able to calculate the volume of an area if you think in one dimension but that is the only dimension you will ever have. ~ ].].] 21:49, 14 June 2009 (UTC) | |||
::RTG: Please stop answering questions you have no clue about. Nearly every sentence of what you wrote is wrong: Space is curved - so it has curves (duh!) - you can trace them by following the paths of lightbeams. Space does what space does without the help of god or gods - there is no shred of evidence for gods of any kind - and all of the physics of space-time works perfectly well without divine intervention. Black holes can only theoretically curve light into a closed loop (see ]) it's not possible in practice because "photon spheres" are unstable - otherwise black holes only bend light like any other gravitational source - nothing remarkable going on there. The universe cannot have an "outside" because that too would (by definition) be a part of the universe. The word "universe" pretty much means "everything" (as you'd know if you took the time to read the very first sentence of our article ]). "Dimensions as we know them are classed as three to help us with mathematical equations" is a meaningless statement. Mathematics can comfortably cope with any number of dimensions - we routinely use four (for space-time) and string theorists go with dozens of dimensions. No - the reason we talk about space as having three dimensions because we can uniquely identify every point in space with three numbers - those don't have to be up-down, left-right, in-out - they could be azimuth, elevation and range...or any of an infinite number of other coordinate systems - however, all of them need exactly three numbers ("dimensions") - hence, "three dimensional". You say that "all objects with mass ''are curved''" - that's nonsense - a proton, for example, has mass - but has zero size - it can't be "curved". Space around objects that have mass is curved. I have no clue what you are babbling about measuring the "volume of an area"...by definition, an area is a measure of a surface - a two dimensional entity - volume relates to three dimensions. Please - don't answer questions unless you are clear on what you are saying in response. ] (]) 03:40, 15 June 2009 (UTC) | |||
:::The proton does too have a size. I agree with everything else you said (specially the point about RTG not answering questions about things he doesn't understand). ] (]) 07:02, 15 June 2009 (UTC) | |||
::::Sure ''Steve''. "Space" is not the definition of a void, and matter can be described as having as many dimensions as you like so long as it is not the one I mention. See ] for the best Einstein theory about how a black hole ''might'' curve "light", GloWorm, and don't kid yourself that Steve knows what shape a proton is, or that we ''know'' if a proton "...has mass - but has zero size ..." (that doesn't actually make sense but you can definitely calculate the theory using mathematics). There is no experiment to show an object (or a space) to have ''zero'' size. It is possible to ''calculate'' zero through ''maths'' but, like Steve says, it is also possible to calculate infinite dimensions through math. Math is ''not'' reality. Infinite ''dimensions'' and time ''travel'' are as feasable as extending your life by transferring you brain onto a ] (it's a double negative, it still is not ''your'' brain) all you can hope is that some part of it keeps on going and that, my friend, is 1 to the power of higher. Like I said, we cannot observe most of the universe that is within our viewing range so the best theories on the outside or the shape of it are all sci-fi. ~ ].].] 08:45, 15 June 2009 (UTC) | |||
:::::And while you're at it, RTG, please don't change the order of the posts, as you just did by moving Steve's and Dauto's comments away from under your comment and to the bottom of this topic, which I have corrected along with this response. Steve's comment was a direct response to your response, and it's far easier for people to follow the discussion when it's organized as a dialogue, instead of placing the newest posts at the bottom. By preserving that order, we can separate the threads of this discussion and make it easier for new readers to follow things, which becomes increasingly important as the discussion gets more in-depth and diverse. Your edit summary said, ''"reverting the order of the posts to their original state"'', but that's not what you did -- you ''changed'' the order of the posts. -- ] (]) 08:49, 15 June 2009 (UTC) | |||
:::::::OK Captain Disdain, and how about you check the order of the posts before "Steve" posted and fix them up right for me? no? Didn't think so. ~ ].].] 08:54, 15 June 2009 (UTC) | |||
::::::::Steve posted in an entirely correct manner. He separated the discussion you are having from the other (related) discussion below, which makes this whole thing more readable. Had he posted at the bottom of this topic, it would've made for a more confusing conversation. There's nothing to fix. -- ] (]) 09:07, 15 June 2009 (UTC) | |||
::OK. In a 3-dimensional coordinate system three numbers are needed to define the position of a point in space in relation to the point of origin. However, to define the position of an '''''object''''' in space a fourth number is needed – time. For instance, an airplane may be at a certain azimuth, elevation and range in relation to a point of origin. However, it is also necessary to state the time at which it is there. The same would apply to any other coordinate system. The position of a point in space can be defined by the quantity of numbers required by the coordinate system (number of dimensions). But to define the position of an '''object''' the time at which it is there must also be stated. An object can move. A point in space cannot move. – GlowWorm. | |||
::To state my last point differently, a moving object moves from point to point in space. When we state its position at a particular time, we are really stating the point in space at which it is situated. - GlowWorm. | |||
:::There is a really great picture on ] for thinking about a "point in space" called "Diagram 1". Time is great for co-ordination but it is merely the name we give to tapping our feet in the rhythm and counting, no ''more'' real than that action. It is possible that your continuous loop will bring the universe back to the same place one day but plotting a point in yesterday, and expecting it to be there, that is "Gods and indistinguishable from Gods" only. When you find a place that is a day of the week, you will surely be able to return to it. ~ ].].] 11:48, 15 June 2009 (UTC) | |||
::::The idea that the universe could loop around and repeat itself exactly is utterly discredited. The idea was that '''if''' the universe ended in a "]" (the opposite of a "]") then the "next" universe would start with another big bang from the singularity created by the end of the this one (see ]). Since the properties of this true singularity would (hypothetically) have precisely the same starting state as the previous one (so the theory proposed), all subsequent events would unfold identically - and all of history would repeat endlessly. However, the "Big Crunch" is now firmly disproved - and in any case quantum randomness would ensure that the universe would not repeat exactly the same way anyhow. Your idea that time is just something we dreamed up is patent nonsense. There are plenty of things that depend on time that were doing their thing long before we came along. Time is required in order for there to be a change in entropy - and everything really depends on that. RTG: Please stop posting your own random daydreams and try to stick to actual science - you aren't helping our questioners with this stream-of-consciousness babble. Your last five or six answers here on the science desk have all been horribly wrong in really fundamental ways. ] (]) 13:08, 15 June 2009 (UTC) | |||
:::::Space is without substance by its very definition. All things things within space, you say, are under some curving effects, they are not space. Time has no more substance than space. Space = go read a dictionary. Time, refer us to the substance of time, Steve. (I am not the only person posting here that space and time have no substance) Can I not ask questions around here because I am not good enough, a babbler, full of BS, streaming conciousness (what are you on>?), am I stringing random words about colours and teapots, come on Steve what insult have you for me this time or is it Dauto in for the intermission? ~ ].].] 14:27, 15 June 2009 (UTC) | |||
::::::It is not really appropriate for you to completely redefine the concept of "spacetime" while answering a question on the reference desk. If you have a problem with the great physicists of our age, I recommend you take it up with them, and when you've made them see the light, and they write papers about it, then you could reference those papers here and prove to the world that you were right all along. ] (]) 16:37, 15 June 2009 (UTC) | |||
::::::What? When did I insult you RTG? listen, Steve may have been unecessarily harsh but he is right that the ref. desk is not a soap box ffor you to express you uninformed opinion about things you don't really understand. Remember earlier when you complained about being constantly bombarded by inconsistent titbits of misinformation? Well, now you're being part of the bombardment. Don't expect the folks here at the ref. desk to take that lightly. ] (]) 18:23, 15 June 2009 (UTC) | |||
:::::::Your first comment to me, Dauto, was to "...say something that normal people can understand." You say Steve acted unessecarily yet he was "right". You say that after insisting that ''I'' make contradictory and insensible statements. Do you see what I am telling you? You both say that my disagreements with you on fundamental principles are unnacceptable and yet, right here on this post, you are contradicted all over (see next post down, for instance). As Ben says, I am really not suitable to answer very many questions about anything here but why should I be slapped in the face and not slap back? You are not stronger than me, friend. If this post can't be finally enough for you, you are on your own. You certainly haven't won me over, wether it is important to you or not. I am not following you. This is likely to be the last post I ever direct at you. I will not be sad if you win a prize. I will not be happy if you cannot add teaching into your method of instruction but, please God, I will never know. ~ ].].] 19:45, 15 June 2009 (UTC) | |||
::::::::When did I isult you? I don't think I did. When did I slap you in the face? I don't think I did. All I did was to point out that your posts are hard to understand and that you don't know enough to understand many of those things you like talking about and that you shouldn't answer questions about subjects you don't understand. None of that is offensive. Heck, I even took the time to right a very careful response to one of your post to help you see why you are falling short. ] (]) 20:32, 15 June 2009 (UTC) | |||
:::::<small>Big Crunch scenarios aren't ruled out—it depends on the nature of the dark energy, and there are fairly natural models where the energy density eventually goes negative, after which the universe recollapses (see ). And there are other cyclic models that don't involve a recollapse, like Penrose's wacky . But RTG, I have to agree with the others who've said that you shouldn't be answering cosmology questions here. -- ] (]) 19:23, 15 June 2009 (UTC)</small> | |||
: Does the curve extend to form a circle? Nobody knows. The hypothesis is called "Multiply connected Universe", a term taken from ] (see ]). Think of it like this: A ring is a one dimensional structure, where every straight path leads back to the origin. A sphere is a two dimensional structure, where every straight path leads back to the origin. The universe could be a three dimensional structure, where every straight path leads back to the origin. That's hard visualize as a geometry, but very easy to do with vectors and ]. It has interesting physical effects. For example gravity between two objects would act from multiple sides, first from the front side, then, when the force has travelled around the universe, from the back side. It could expain the accelerated expansion of the universe and disprove the ] theory, but that is not widely believed. http://cat.inist.fr/?aModele=afficheN&cpsidt=18523179 | |||
:::That paper () is obviously wrong and shouldn't have passed peer review. They compare an infinite universe that's empty except for one supercluster (inhomogeneous, average density zero) to a compact universe containing the same supercluster (homogeneous, average density nonzero) and find a difference in the gravitational field. If they'd given their infinite universe the same matter distribution as their compact universe then the difference would have disappeared (aside from anisotropies). They conclude that their effect can't explain the dark energy anyway, but in fact the effect doesn't even exist. -- ] (]) 19:23, 15 June 2009 (UTC) | |||
:* Space is not curved, though ] is. (You have to have a mathematical model that demonstrates it, according to our article). In classical ] the question can't come up, because space and time are regarded as imponderables which merely set the stage for motion. Einstein's model, which made space and time a single concept, associated curvature with the force of gravity. This had nothing to do with spheres and circles; there is no relationship between ] and geometry. --] (]) 01:46, 15 June 2009 (UTC) | |||
:::"...there is no relationship between ] and geometry" - not sure I follow that. Seems to me that many of the topics covered in ] and ] are very geometrical. I would say that a large part of general relativity is an application of ]. ] (]) 05:34, 15 June 2009 (UTC) | |||
::::Isn't some of this ], or ]? Some things are theorized, are they not? Other things are considered to be known beyond a shadow of a doubt. For instance, the existence of ] in the universe has I think recently come under question. I don't know if curvature or the absence of curvature as a quality of space is really known with assuredness. ] (]) 18:36, 15 June 2009 (UTC) | |||
:::::Yes, somethings are considered hypothesis while others are considered to be known beyond a shadow of a doubt, as you said. General Relativity falls on that second cathegory. ] (]) 18:47, 15 June 2009 (UTC) | |||
::::::Bus stop, while researchers are still active in trying to extend and complete the theory of ] and integrate it it with Quantum Mechanics, the central bulk is really beyond dispute; its predictions have been experimentally confirmed numerous times over the last ~90 years. See ], which discusses several experiments that have measured the curvature of space-time (or, the bending of light) in presence of gravitational bodies. ] (]) 19:33, 15 June 2009 (UTC) | |||
:::::::Another point: dark matter is alive and well. Read ] for some of the more recent (strong) evidence. ] (]) 20:04, 15 June 2009 (UTC) | |||
::::::::I should have said ]. I casually glanced at this article, in the April 2009 issue of . ] (]) 20:13, 15 June 2009 (UTC) | |||
:With regard to what is "outside the universe", drawings are sometimes used to depict the various theories about the shape of the universe. (Some of these drawings are shown in the Wikepedia article "]".) All these drawings raise the question of what is outside the shape depicted. The drawings themselves have white space around them. The white space is misleading. It does not represent space outside the universe. The complete depiction of the universe stops at the outer edge of the actual drawing. – GlowWorm. | |||
= June 15 = | |||
== natural refraction of sound? == | |||
I read that that sound refraction often happens in the morning over bodies of water, where the water and lower air are still cold, and the higher air is warmer. The claim was made that this allowed people to hear further than they normally would and amplified the sound. There are then claims that peoeple have had normal conversations from incredible distances, like 400 meters. Can the curved refraction actually focus the sound to create amplification at certain points? Or are these stories just made up? I would have thought that the refracted sound would not travel any further than normal sound during the day when all the air was heated - so how could people be talking in normal voices 400m away? Also does anyone know of any other situations in sound refraction occurs naturally or situations where sound is amplified (ie. focused so that the amplitude is above what would expect) naturally?--] (]) 01:07, 15 June 2009 (UTC) | |||
:] ~ ].].] 01:21, 15 June 2009 (UTC) | |||
::No - that's not correct. Whispering galleries work by reflection, not refraction. ] (]) 03:07, 15 June 2009 (UTC) | |||
:Certainly sound refracts through air of different densities (and therefore temperatures). In uniform air, the energy of the sound wave expands outwards in a sphere (think ripples on a pond - but in 3D) - as the sound waves move outwards, the radius of the sphere grows and the energy is spread out over an ever increasing area. As the distance from the source doubles - the area quadruples - so the sound becomes four times quieter. One mechanism by which a particular temperature profile over water could increase the volume of the sound would be if the sound were refracted from layers above the water - and bounced back off of the water surface - such that the sound waves would expand outwards in a cylinder. That would mean that doubling the distance would only halve the volume of the sound - so it would travel MUCH further and still be heard. This is somewhat like a ']' or ']' or ] works for radio/light. By constraining the way that the waves can spread out, the energy can travel further. ] (]) 03:51, 15 June 2009 (UTC) | |||
: In principle, sound waves can experience ] at the air/water or the cold-air/hot air interface and reach places where they might not have reached otherwise. The reflected wave can also add to the directly receive sound and (possibly) amplify the received signal - however there will be considerable phase difference (delay) between the direct and reflected waves, which means that we will hear an "echo" rather than an amplified sound. We will need to plug in the exact temperature profile (and the consequent changes in the ]), to determine if this "in principle phenomenon" is actually observed in practical settings. ] (]) 04:05, 15 June 2009 (UTC) | |||
::I believe the refraction and long distance surface propagation of sound occurs when the air is generally ''cooler'' than the water resulting in a gradient of warm air near the surface. The cooler air is slightly more dense and thus conducts sound slightly faster, resulting in the wave tending to focus back towards the surface. This would result in the cylinder-like propogation described by SteveBaker above. This is also why this effect is often observed in the late evening as the air cools, but the water remains warm. -- ] (]) 04:29, 15 June 2009 (UTC) | |||
::: Hmmm, "cooler air is slightly more dense and thus conducts sound slightly faster" is not true. ] in air, increases with temperature (proportional to <math> \sqrt{T} </math>), so we need the colder air layer to be near the water surface in order for the sound to refract back down. ] (]) 04:54, 15 June 2009 (UTC) | |||
::: Abecedare is right, the sound speed increases with the temperature. Hot air at the bottom and cold air on top would have the opposite effect (which sometimes is actually observed in deserts). The sound ends up deflected upwards and it becomes almost impossible to hear anything more than just a few dozen meters away. It's the silence of the desert! <small><span class="autosigned">—Preceding ] comment added by ] (] • ]) 06:18, 15 June 2009 (UTC)</span></small><!-- Template:Unsigned --> <!--Autosigned by SineBot--> | |||
::::If you were in a desert at night, with no real wind, you could quite easily holler over a long distance. Bodies of water are often in a valley, sheilded from much noise outside a specific area. It is probably a little quieter a couple of hours ''before'' morning starts. I don't know if that helps. ~ ].].] 09:04, 15 June 2009 (UTC) | |||
:::::No - as Dauto points out deserts tend to be quiet because their temperature profile is the opposite of that over water. The air above the ground refracts the sound away from the ground...something that it also does to light...hence mirages. Plus, if it's a sandy desert, the ground will absorb sound rather than reflect it back up...if it's a rocky desert then the sound will likely be scattered by the rocks. The deserts I've visited in Arizona and New Mexico do indeed seem very quiet places. What makes water (particularly calm water) so effective at doing this is that it has a smooth, predominantly horizontal surface that reflects the sound back upwards. With the air diffracting the sound downwards and the water reflecting it back up - you produce this 'wave-guide' effect that prevents the sound from propagating in three dimensions - and by constraining it to two dimensions (well, kinda), allows it to propagate further. A very narrow canyon with smooth, near-vertical walls might maybe produce the same effect - but a gentler valley would not...particularly if it's predominantly lined with softer, sound-absorbing materials like grass and other vegetation. ] (]) 12:42, 15 June 2009 (UTC) | |||
== Should I turn on the lights at night when using my computer? == | |||
Does it depend on personal preference, or is one option preferable to the alternative? Thanks. ] (]) 03:03, 15 June 2009 (UTC) | |||
:I'm not aware of any conclusive studies. Opinion is widely divided amongst computer programmers and other long-term computer users. Personally, I like light - but it's gotta be arranged so it doesn't glare off of the screen. I don't think it matters. Avoiding eye-strain is certainly important - but the best thing you can do is to take at least a couple of 5 minute breaks every hour...focus on something far from the screen - take a walk - stretch - etc. ] (]) 04:00, 15 June 2009 (UTC) | |||
::Many scientific studies have produced conflicting results about the long-term impacts of ] on vision. It seems to be inconclusive. It is not even clear whether light or dark in the periphery of your computer monitor has any effect on eyestrain, let alone whether that induces any vision trouble. Take a look at ] - see the cited sources there, and note that there is not a consensus among scientists and medical doctors. ] (]) 04:07, 15 June 2009 (UTC) | |||
== supplier for polyvinyl alcohol & dextrin adhesive == | |||
Research shows me that the above adhesive ( polyvinyl alcohol & dextrin)is that which is used on postage stamps. I believe this may be the same adhesive used on self sealing envelopes. I am in need for a supplier for an ultra peelable adhesive similar to the postage stamp adhesive. | |||
I have exhausted my search options for that particular adhesive supplier. | |||
Thanks for the help. ] (]) 03:23, 15 June 2009 (UTC) | |||
== QUANTUM MECHANICS -AS POPULAR SCIENCE == | |||
INTERESTED TO KNOW MORE ABOUT QUANTUM MECHANICS WITHOUT MATHEMATICS . <span style="font-size: smaller;" class="autosigned">—Preceding ] comment added by ] (]) 04:18, 15 June 2009 (UTC)</span><!-- Template:UnsignedIP --> <!--Autosigned by SineBot--> | |||
:At the top of our main article, ], there is this message: | |||
::''For a generally accessible and less technical introduction to the topic, see ].'' | |||
:Have you read either of those articles? If they are too difficult, try versions. ] (]) 04:22, 15 June 2009 (UTC) | |||
:Why would you tie your hands behind your back like that? Quantum Mechanics is already hard enought even with mathematics.] (]) 06:23, 15 June 2009 (UTC) | |||
::I think it depends on the interest level of the student and his free time available for this. If he/she is not a serious student, then i don't think learning with all the mathematics is necessary, just the principle, as learning the mathematics itself would take considerable amount of time. Personally, I would recommend the Vignettes in Physics, Quantum Revolution by G.Venkataraman, a set of three books, which beautifully explain in qualitative terms the implications of Quantum Theory - Look for it in your local book store. I read it and thoroughly enjoyed it. ] (]) 07:02, 15 June 2009 (UTC) | |||
== Computer Keyboard == | |||
Why is the keys of a keyboard arranged in a particular fashion and not alphabetically??] (]) 04:29, 15 June 2009 (UTC) | |||
:From our article, ]: | |||
::The QWERTY keyboard layout was devised and created in the early 1870s by ], a ] editor and printer who lived in ]. ... His "Type Writer" had its printing point located beneath the paper carriage, and so was invisible to the operator. Consequently, the tendency of the typebars to clash and jam if struck in rapid succession was an especially serious problem, in that the mishap would only be discovered when the typist raised the carriage to inspect what had been typed. ... Sholes struggled for the next six years to perfect his invention, making many trial-and-error rearrangements of the original machine's alphabetical key arrangement in an effort to reduce the frequency of typebar clashes... Eventually he arrived at a four-row, upper case keyboard approaching the modern QWERTY standard. | |||
:You might also be interested in ] layout. ] (]) 04:37, 15 June 2009 (UTC) | |||
:(ec)They mimic the positions of typewriter keys - and those were originally laid out in an effort to improve typing speeds by limiting the distances your fingers have to move to hit the most frequent English word spellings. See ] for details. Someone here will probably tell you that the keyboard layout was actually designed to slow down typists - but that's an urban legend. Someone will also probably try to tell us that "]" layout is faster - but that's also untrue. ] (]) 04:44, 15 June 2009 (UTC) | |||
::Dvorak may or may not be faster (is it for me), but it sure is more comfortable. :-) -- ] (]) 07:54, 15 June 2009 (UTC) | |||
:::A lot of the early studies on Dvorak were either faked, rigged or just so poorly run as to be meaningless. Their results caused quite a few people to switch - and given the effort required to do that, those adopters continue to support it with great fervor - mostly because of the urban legend about QWERTY being specifically designed to slow typists down in order to avoid jamming the early typewriters - which turns out to be very far from the truth - or that it was designed so that typewriter salesmen could type the word "typewriter" using only the top row of keys without moving their fingers. However, more recent, carefully run studies show zero benefits of any kind for Dvorak. As a result, it's just a pain in the neck to have to support it. Users of it have to suffer the difficulties of being unable to use other people's keyboards efficiently - and having to switch back to QWERTY for things like PDA keyboards and the like. It's a nasty con trick perpetrated on the community - and it needs to die. ] (]) 12:29, 15 June 2009 (UTC) | |||
:Obligatory link. — ] 14:28, 15 June 2009 (UTC) | |||
::::Without questioning the fact that there are many urban legends surrounding QWERTY's origins and Dvorak's advantages, I'll disagree with you on your conclusion, Steve. I have typed with both keyboards for over a decade - QWERTY at work, Dvorak at home - and I'll testify that Dvorak is more comfortable & ergonomic. For me, that translates to a little faster, but that's not generalizable. But I (and my wife, who also is ambikeyboardous) don't suffer any of your supposed nasty effects of this "con". ] (]) 20:19, 15 June 2009 (UTC) | |||
:::::I don't understand how the Dvorak keyboard is more comfortable and ergonomic than the QWERTY keyboard. ] (]) 22:47, 15 June 2009 (UTC) | |||
== scientists own writings == | |||
How can i get important thesis of sientists in their own word with full mathematical details . <span style="font-size: smaller;" class="autosigned">—Preceding ] comment added by ] (]) 07:31, 15 June 2009 (UTC)</span><!-- Template:UnsignedIP --> <!--Autosigned by SineBot--> | |||
:By subscribing to a ]. ] 07:58, 15 June 2009 (UTC) | |||
::It depends. Many articles are online, both significant , but in particular newer ones, e.g. via ] or simply from the authors home page. "Full mathematical details" are usually in PhD theses, which can be online or available via a good scientific library, possibly via ]. --] (]) 11:22, 15 June 2009 (UTC) | |||
::If you live near a university (or are a student of one) they should have journal papers that you can have a look at (you probably won't be allowed to borrow them). Also, the university may have online access to journal papers that you can download. - ] (]) 12:41, 15 June 2009 (UTC) | |||
The original questioner asked for the ] specifically - did you mean the ]? These are published by the original university, and may be available for free through a research library. You may also be able to access them online (for free or for a charge, depending on may factors). Universities in the United States publish doctoral dissertations through a clearinghouse, ], which is the distributor for almost all archived dissertations. You can search through 125 billion digital documents, including dissertations, from ProQuest's (you may need to pay a fee or visit a library or research institution with a subscription). ProQuest republishes doctoral dissertations from all accredited universities in the United States, and has online archives of all dissertations since 1938 and a large percentage of all U.S. dissertations since the early 19th century. The original research institution and the author also usually retain the rights to republish their dissertations in other formats as well - so you may be able to find the thesis elsewhere. ] (]) 16:09, 15 June 2009 (UTC) | |||
<small>Note that this company is not merely another opportunistic Web 2.0 data aggregator - it is the official repository for dissertations by . ] (]) 16:15, 15 June 2009 (UTC) </small> | |||
== Number of Synapses in Newborns == | |||
I've searched - but was not able to find - the number of synapses in newborns (or number of avarage synapses per neuron). Adults (as well as newborns) have about 10<sup>11</sup> neurons with (in adults) about 10<sup>14</sup> synapses (1000 S./N.). For 3-year-olds I have found numbers of 15.000 S./N. and for newborns about 2500 S./N. (synaptic plasticity). Can this be confirmed (i.e. large number in the beginning, then even an increase, and finally settling to an "operational number" of about 1000 S./N.) <u>with references</u>? Curious ... --Grey Geezer 11:57, 15 June 2009 (UTC) <small><span class="autosigned">—Preceding ] comment added by ] (] • ]) </span></small><!-- Template:Unsigned --> <!--Autosigned by SineBot--> | |||
:The best source I can find regarding this is the "Synaptogenesis" chapter of the book ''Neural Plasticity'' by Peter Huttenlocher. You can at Google Books. ] (]) 15:34, 15 June 2009 (UTC) | |||
::Thanks for the reference. Numbers are different, however, the tendency seems to be the same. Will read. --Grey Geezer 16:14, 15 June 2009 (UTC) <small><span class="autosigned">—Preceding ] comment added by ] (] • ]) </span></small><!-- Template:Unsigned --> <!--Autosigned by SineBot--> | |||
== Weird Street Drug == | |||
My friend is trying to convince me that in the early '90's, there was this street drug that made you sexually orgasm almost instantly. He said that it was originally developed for astronauts whose stay in space is long term. Did/does such a drug ever exist/ed? --] (]) 13:23, 15 June 2009 (UTC) | |||
:Clomipramine. Have fun!] (]) 13:34, 15 June 2009 (UTC) | |||
::Unless you have a reference, don't make that claim. There is evidence that ] can cause yawning-induced orgasms, but this is only in a small number of depressed patients . It would be good if others can find more references for this, specifically with a larger sample and in a more reputable journal. On another note, clomipramine isn't a street-drug, and I haven't a clue what it has to do with astronauts. In the majority of cases, clomipramine (and other ]s/]s) actually causes ]. (EDIT: 1641GMT: Here are a couple of SD refs (but every pharmacology textbook will mention it): , sorry for lateness, I had to leave immediately so didn't have time to find refs at first). --] (]) 14:34, 15 June 2009 (UTC) | |||
:You are right to be skeptical. The astronaut claim is silly. You should present him with a sign like this: ] (]) 14:35, 15 June 2009 (UTC) | |||
omg, I just read about this ]. I wonder if this is what my friend was talking about. --] (]) 14:53, 15 June 2009 (UTC) | |||
:Our article ] seems to have better and more information than that link, for what it's worth. ] (]) 20:07, 15 June 2009 (UTC) | |||
== Sun's gravity on Mercury vs Pluto == | |||
When astronauts head into space the effect of Earth's gravity tails of pretty quickly I believe. Earth is over 12000km in diameter and is 5.9736 × 10<sup>24</sup> kg but just 400km above the surface gravity tails off about 10%. With this is mind I can't get my head around why Mercury, being so close to the Sun hasn't been pulled in when the Sun still has enough gravitational force to keep Pluto in orbit when it's so far away. If it's possible to keep the explanation simple I'd appreciate it, I know very little about physics :-) | |||
Thanks all --16:19, 15 June 2009 (UTC)] (]) | |||
:Basically the answer is that Mercury moves a lot faster than Pluto. It spins around the Sun so fast that the gravitational force from the Sun is just enough to counterbalance Mercury's tendency to go shooting off into space. ] (]) 16:38, 15 June 2009 (UTC) | |||
:(EC) Two points: | |||
::*First: Your understanding of how quickly earth's gravity tails off is inacurate. Gravity actually follows an inverse square law (That is, the strength of a body's gravitational pull is proportinal to the inverse of the square of the distace to that body). So at 400 km above the ground earth's gravity is still 88.5% as strong as at ground level. | |||
::*Second (and more important): Both Mercury and Pluto are in orbit around the sun. its true that the sun's tug on mercury is much stronger than on Pluto, but it is also true that Pluto is moving more slowly around the sun. In both situations the sun's gravitational tug is just right to provide the centripetal force necessary to keep the planets on a (approximately) circular orbit. ] might be a good read for you. ] (]) 16:49, 15 June 2009 (UTC) | |||
:::My understanding of the OP's phrase "gravity tails off about 10%" is that the gravity is reduced ''by'' 10%, not ''to'' 10%, so s/he is approximately correct. --] 17:07, 15 June 2009 (UTC) | |||
Thanks for quick replies all, seems obvious now you've explained it :-) That circular motion link was a bit much for me Dauto but I might read it again when I'm more awake, and thanks Sean, I did mean reduced by 10%. Could I ask for an expansion on the original question... I take it that when the <s>universe</s> solar system was forming the planets achieved a natural equilibrium? Matter closer to the Sun (accretion disc?) was orbiting faster, matter further away orbiting more slowly so that as the planets formed they naturally fell into the 'appropriate' orbit according to velocity, mass and distance from the Sun? (EDIT): What I mean is the planets didn't form and then fall into their current orbits, they actually formed apprximately where they are now? --] (]) 17:37, 15 June 2009 (UTC) | |||
::::Yes, that's correct. The planets were formed already in orbit around the (young) sun. They did not necessarily form exactly where they are now because at those early times there was a lot of debris floating around the solar system and interaction with all that debris is believed to have made the plats wander away from their original orbits. But once most of that debris was cleared away the planets orbits have remained pretty much stable ever since. ] (]) 18:43, 15 June 2009 (UTC) | |||
::::Tx again Dauto :-) --] (]) 22:06, 15 June 2009 (UTC) | |||
== Recoil Upward Motion - Firearms == | |||
Why does the barrel of a pistol or rifle rise - as opposed to jerking any which way, down, left, right, etc. when fired? I understand recoil, but not why a barrel moves upward when fired. ] (]) 16:50, 15 June 2009 (UTC) | |||
:I would imagine it's because the bullet, when it fires, pushes against the upper part of the weapon closet to your body. Therefore, it's not so much going up as it is pivoting around your hand. -- ] <sup>(] • ])</sup> 17:08, 15 June 2009 (UTC) | |||
== question about stability of ecamsule == | |||
For a while now I’ve been searching for information on the stability of sunscreens containing avobenzone when exposed to makeup containing titanium dioxide and iron oxides. I found one article online: see http://www.koboproductsinc.com/Downloads/NYSCC-Avobenzone.pdf | |||
However, I don’t know if the information found in that article applies to ecamsule. I’ve read, for example, that since the avobenzone in la roche posay’s anthelios xl is stabilized, it won’t degrade in the presence of mineral makeups, but I can’t find anything definitive on this subject. Since most women wear makeup and since it’s almost impossible to find makeup that doesn’t contain titanium dioxide and iron oxides, I wonder why more studies have not been done regarding this issue. My big question is, does wearing makeup degrade the ecamsule or the form of avobenzone used in mexoryl sunscreens?] (]) 17:41, 15 June 2009 (UTC) comment added by ] (] • ]) 17:36, 15 June 2009 (UTC)</span></small><!-- Template:Unsigned --> <!--Autosigned by SineBot--> | |||
== post-splenectomy immunication schedule == | |||
I know splenectomy patients (with no part of the spleen remaining) need vaccinations periodically for the rest of their lives, but what vaccinations and how often, please? (Later readers of responses hereto should note that they are general and not intended as personal advice, for which you should consult your physician (or osteopath).)—]<span class="Unicode">℠</span> 17:42, 15 June 2009 (UTC) | |||
:The vaccinations required after a ] are explained in ]. ] 18:12, 15 June 2009 (UTC) | |||
== How do I give a ferret an orgasm? == | |||
Please help (it's a male ferret) | |||
: I would let a female ferret handle that personally. ] (]) 18:11, 15 June 2009 (UTC) | |||
:: I don't want them to breed, I need to collect a ferret sperm sample for reasons best not discussed here. <span style="font-size: smaller;" class="autosigned">—Preceding ] comment added by ] (]) 18:34, 15 June 2009 (UTC)</span><!-- Template:UnsignedIP --> <!--Autosigned by SineBot--> | |||
:It's basically the same for all mammals. will give you some details, and shows an ] for harvesting rabbit ], which might be about the right size for a ferret (I'm not familiar with ferret cock, personally). --] 18:40, 15 June 2009 (UTC) | |||
== parasitic worms == | |||
Would it be genetically modified parasitic worms (mainly by limiting lifespan and reproduction) be useful as a weight loss aid, or would they not steal enough nutrients to have an effect if there are only a few worms? ] (]) 20:00, 15 June 2009 (UTC) | |||
:I believe similar Q's were asked here previously, and the answer was that it's a bad idea because they steal vitamins and minerals, not just calories. So, you would risk malnutrition with such a "treatment". ] (]) 20:15, 15 June 2009 (UTC) | |||
::Your body's ] in trying to get rid of the intruder might be another point worth mentioning. Such results are highly individual, unpredictable and if they result in an ] can be almost impossible to reverse once primed. ] (]) 20:48, 15 June 2009 (UTC) | |||
::Yep, Stu - have a look at ]. This is the question I asked on a similar subject last year. The OP might find this useful... --] (]) 21:22, 15 June 2009 (UTC) | |||
== Smoked cylinder == | |||
I just watched the movie ], set during the 1930's, in which a doctor berated his research assistant for failing to record a medical experiment on a "]". What is it, how was it used, and what info did it record ? ] (]) 20:12, 15 June 2009 (UTC) | |||
:googling gave several results (including a couple that are more relevant to the ferret Q above:-) This looks like one of the more relevant ones The device seems to work similarly to an old ]. I'm not sure it would be worth a page, but there should be some mention in a paragraph on history of medicine somewhere. (volunteers step forward, please)] (]) 20:31, 15 June 2009 (UTC) | |||
== immovable object and irresistable force - revisited == | |||
A while back there was some discussion about the immovable object/irresistable force paradigm. The original poster wondered if such an event were to occur, wouldn't they just cancel each other out. Anyway, while I was in my Aikido class I had a thought: what if we think differently? In other words, in pondering this question, we think in terms of either the irresistable force being stopped by the immovable object or the immovable object diffusing the irresistable force. What about the idea of redirecting? In other words, what if the imovable object turned on it's axis and redirected the irresistable force? We tend to think of moving as back and forth or sideways; therefore, simply rotating on it's axis is not really "moving" in the classical sense. Also, we tend to think of "resisting" as stopping all movement rather than redirecting it. I am suggesting that if this paradigm could exist then the idea of rotation/redirection would maintain the purity of both immovable and irresistable. What do others think? <span style="font-size: smaller;" class="autosigned">—Preceding ] comment added by ] (]) 21:48, 15 June 2009 (UTC)</span><!-- Template:UnsignedIP --> <!--Autosigned by SineBot--> | |||
:As stated at ], this is meant to be an exercise in logic and/or in semantics. Your proposal doesn't resolve the paradox. ] (]) 21:58, 15 June 2009 (UTC) | |||
:The paradox isn't a real one since no object is immovable. (Interestingly, all forces are irresistible, though.) In the real world, an object can often redirect a force and a force can often redirect an object. ] (]) 22:19, 15 June 2009 (UTC) | |||
::This reminds me I once felt I had a solution to the paradox. I'm sure it needs tightening up, and it may (almost inevitably) be flawed, but here it is: | |||
::Imagine object, something like a ], moving through space. A ray doesn't have mass, but this object may - the point is it can exert a force and some may insist that this requires mass. Imagine it is moving through space at some speed - the amount is irrelevant, but for the purpose of concreteness, assume 1 m/s. When the head of the ray hits a small object, it just pushes it aside. When it encounters a larger object, it "piles up" behind the object, until the accumulated force moves the object. For any movable object, the ray encounters the object and the head of the ray is stopped for a time, until it amasses enough force to move the object. We can assume that the length of time is proportional to the resistive force. Note that while the head of the ray stops for a finite period of time when it encounters an object, the weighed average of the mass continues to move at 1 m/s, as almost all (in the mathematical sense) of the ray is still moving. (I realize I just calculated a weighed average over an infinite length, at that may get me in trouble.) | |||
::So we have defined an object that is irresistible. When it encounters a normal object, a finite portion of the object comes to rest for a finite period of time, but the overall object does not stop, and eventually moves the object. | |||
::So now what happens when the irresistible force meets an immovable object? The head of the ray is stopped, and begins piling up. But while the object never moves, the ray (arguably) never stops. | |||
::I don't fully expect anyone to decide this paradox has now been convincingly resolved, but it's my stab at it - in my mind, I've defined an irresistible object, and immovable object, and described what happens when they meet. The result doesn't cause one to re-assess the label of immovable, because the object doesn't move. Nor does it cause one to re-assess the label of irresistible, as it has moved every other object it encounters, and even after encountering this object, it is still moving. --<font style="font-family:Monotype Corsiva; font-size:15px;">]]</font> 22:45, 15 June 2009 (UTC) |
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December 25
Mass of oscillating neutrino
From the conservation of energy and momentum it follows that a particle that is not subject to external forces must have constancy of mass.
If I am right, this means that the mass of the neutrino cannot change during the neutrino oscillation, although its flavoring may. Is this written down somewhere? Thank you. Hevesli (talk) 19:24, 25 December 2024 (UTC)
- Any (flavored) neutrino that is really observed is a superposition of two or three mass eigenstates. This is actually the cause of neutrino oscillations. So, the answer to your question is complicated. Ruslik_Zero 19:40, 25 December 2024 (UTC)
- Important note: particle physicists today generally only ever use "mass" to mean "invariant mass" and never anything else: . Like the term says, invariant mass is well, invariant, it never changes ever, no matter what "external forces" may or may not be involved. Being proper particle-icans and following the standard practice in the field, then, the three neutrino masses are constant values. ..."Wait, three?" Yeah sure, turns out neutrinos come in three "flavors" but each flavor is a mixture of the three possible mass "states". As mentioned, due to Quantum Weirdness we aren't able to get these different states "alone by themselves" to measure each by itself, so we only know the differences of the squares of the masses. Yeah welcome to quantum mechanics.
- Richard Feynman: "Quantum mechanics describes nature as absurd from the point of view of common sense. And yet it fully agrees with experiment. So I hope you can accept nature as She is – absurd." --Slowking Man (talk) 06:06, 26 December 2024 (UTC)
- The equation uses invariant mass m0 which is constant if E and p are constant. The traveling neutrino has a varying mass mixture of different flavors with different masses. If a mixture of different masses changes, you would expect the resulting mass to change with it. But somehow this does not happen as the neutrino mass mixture changes. These mixture changes cannot be any changes. The changes must be such that the resulting mass of the traveling neutrino remains constant. My question is whether this is described somewhere. Hevesli (talk) 11:16, 26 December 2024 (UTC)
- I freely confess I'm uncertain exactly what's being "asked for" or "gotten at" here. Have you looked at the neutrino oscillation article? From it:
That is, the three neutrino states that interact with the charged leptons in weak interactions are each a different superposition of the three (propagating) neutrino states of definite mass. Neutrinos are emitted and absorbed in weak processes in flavor eigenstates but travel as mass eigenstates.
- What is it that we're "doing" with the energy–momentum relation here? For the neutrino, we don't have a single value of "mass" to plug in for , because we can't "see" the individual mass eigenstates, only some linear combination of them. What you want for describing neutrino interactions is quantum field theory, which is special relativity + QM. (Remember, relativity is a "classical" theory, which presumes everything always has single well-defined values of everything. Which isn't true in quantum-world.) --Slowking Man (talk) 18:41, 26 December 2024 (UTC)
- Not all potential evolutions of a linear combination of unequal values produce constant results. Constancy can only be guaranteed by a constraint on the evolutions. Does the fact that this constraint is satisfied in the case of neutrino oscillation follow from the mathematical formulation of the Standard Model, or does this formulation allow evolutions of the mass mixture for which the combination is not constant? If the unequal values are unknown, I have no idea of how such a constraint might be formulated. I think the OP is asking whether this constraint is described somewhere. --Lambiam 00:51, 27 December 2024 (UTC)
- I freely confess I'm uncertain exactly what's being "asked for" or "gotten at" here. Have you looked at the neutrino oscillation article? From it:
- The equation uses invariant mass m0 which is constant if E and p are constant. The traveling neutrino has a varying mass mixture of different flavors with different masses. If a mixture of different masses changes, you would expect the resulting mass to change with it. But somehow this does not happen as the neutrino mass mixture changes. These mixture changes cannot be any changes. The changes must be such that the resulting mass of the traveling neutrino remains constant. My question is whether this is described somewhere. Hevesli (talk) 11:16, 26 December 2024 (UTC)
December 27
Low-intensity exercise
If you exercise at a low intensity for an extended period of time, does the runner's high still occur if you do it for long enough? Or does it only occur above a certain threshold intensity of exercise? 2601:646:8082:BA0:CDFF:17F5:371:402F (talk) 20:13, 27 December 2024 (UTC)
- Hows about you try it and report back? :) ←Baseball Bugs carrots→ 21:31, 27 December 2024 (UTC)
- I wanted to try it just today, but I had to exchange the under-desk elliptical trainer I got for Christmas for a different model with more inclined treadles because with the one I got, my knees would hit the desk at the top of every cycle. Anyway, I was hoping someone else tried it first (preferably as part of a formal scientific study) so I would know if I could control whether I got a runner's high from exercise or not? 2601:646:8082:BA0:9052:E6AF:23C7:7CAF (talk) 03:09, 28 December 2024 (UTC)
Also, sorry for adding to my own question, but here's a related one: is it known whether the length of a person's dopamine receptor D4 (which is inversely correlated with its sensitivity) influences whether said person gets a runner's high from exercise (and especially from low-intensity exercise)? 2601:646:8082:BA0:9052:E6AF:23C7:7CAF (talk) 03:14, 28 December 2024 (UTC)
fastidious organism vs auxotroph
Hi,
What is the difference between an auxotroph and a fastidious organism? It seems to me the second one would have more requirements than the first one, but the limit between the two definitions is rather unclear to me.
Thank you 212.195.231.13 (talk) 23:17, 27 December 2024 (UTC)
- I'm not 100% sure, but it seems to me that an auxotroph is a specific type of a fastidious organism. 2601:646:8082:BA0:9052:E6AF:23C7:7CAF (talk) 03:02, 28 December 2024 (UTC)
- Symbiosis aside, it would seem that most auxotrophs would be fastidious organisms, but there could be many more fastidious organisms that aren't auxotrophs. Auxotrophs specifically can't produce organic compounds on their own. There are a LOT of organisms that rely on the availability of non-organic nutrients, such as specific elements/minerals. For instance, vertebrates require access to calcium. Calcium is an element; our inability to produce it does not make us auxotrophs.
- But perhaps symbiosis would allow an organism to be an auxotroph without being a fastidious organism? For instance, mammals tend to have bacteria in our guts that can digest nutrients that our bodies can't on their own. Perhaps some of those bacteria also assemble certain nutrients that our bodies can't? -- Avocado (talk) 14:27, 28 December 2024 (UTC)
December 28
Paper with wrong enantiomer in a figure
In the following reference:
- Quack, Martin; Seyfang, Georg; Wichmann, Gunther (2022). "Perspectives on parity violation in chiral molecules: theory, spectroscopic experiment and biomolecular homochirality". Chemical Science. 13 (36): 10598–10643. doi:10.1039/d2sc01323a. PMID 36320700.
it is stated in the caption of Fig. 8 that S–bromochlorofluoromethane is predicted to be lower in energy due to parity violation, but in the figure the wrong enantiomer is shown on this side. Which enantiomer is more stable, according to the original sources for this data? –LaundryPizza03 (dc̄) 08:18, 28 December 2024 (UTC)
Where can I find data on the circulation and citation rates of these journals?
Hello everyone, To write an article about a scientist, you need to know, where can I find data on circulation and citation rates of journals from this list? Vyacheslav84 (talk) 09:58, 28 December 2024 (UTC)
So-called “Hydrogen water”
I saw an ad promoting a device which presumable splits water into hydrogen and oxygen and infuses water with extra hydrogen, to a claimed surplus of perhaps 5 ppm, which doesn’t seem like much. I found a review article which looked at several dozen related studies that found benefits:https://pmc.ncbi.nlm.nih.gov/articles/PMC10816294/ .
I’ve noticed that carbon dioxide or chlorine (chloramine?) dissolved in water work their way out pretty easily, so I wonder if dissolved hydrogen could similarly exit hydrogen enriched water and be burped or farted out, rather than entering the blood stream and having health benefits. is it more than the latest snake oil? Edison (talk) 23:01, 28 December 2024 (UTC)
- Yes, the dissolved hydrogen will exit the water just as quickly (even faster, because of its low molecular mass and complete lack of polarity or capability for ionic dissociation), and even if it does enter the bloodstream, it will likewise get back out in short order before it can actually do anything (which, BTW, is why deep-sea divers use it in their breathing mixes -- because it gets out of the bloodstream so much faster and therefore doesn't build up and form bubbles like nitrogen does) -- so, I don't think it will do much! 2601:646:8082:BA0:209E:CE95:DB32:DD64 (talk) 01:50, 29 December 2024 (UTC)
- It's conceivable it might take out the chloramine, I guess. I don't think there's very much of it, but it tastes awful, which is why I add a tiny bit of vitamin C when I drink tap water. It seems to take very little. Of course it's hard to tell whether it's just being masked by the taste of the vitamin C. --Trovatore (talk) 02:12, 29 December 2024 (UTC)
- If you just want to split water into hydrogen and oxygen all you need is a battery and two bits of wire. You don't say where you saw this ad but if it was on a socia media site forget it. Shantavira| 11:47, 29 December 2024 (UTC)
- If this so-called hydrogen water was emitting hydrogen bubbles, would it be possible to set it afire? ←Baseball Bugs carrots→ 14:03, 1 January 2025 (UTC)
- We once had an article on this topic, but see Misplaced Pages:Articles for deletion/Hydrogen water. Graeme Bartlett (talk) 22:27, 1 January 2025 (UTC)
- I don't know if it is rubbish or not but a quick look on the web indicates to me it is notable enough for Misplaced Pages. I didn't see anything indicating it definitely did anything useful so such an article should definitely have caveats. I haven't seen any expression of a potential worry either so it isn't like we'd be saying bleach is a good medicine for covid. NadVolum (talk) 23:07, 1 January 2025 (UTC)
- International Journal of Molecular Sciences does not sound of exceptionally high quality. DMacks (talk) 01:05, 2 January 2025 (UTC)
December 29
Potential energy vs. kinetic energy. Why not also "potential velocity" vs. "kinetic velocity"? E.g. in the following case:
In a harmonic oscillator, reaching the highest point involves - both a minimal kinetic energy - along with a maximal potential energy, whereas reaching the lowest point involves - both a maximal kinetic energy - along with a minimal potential energy. Thus the mechanical energy becomes the sum of kinetic energy + potential energy, and is a conserved quantity.
So I wonder if it's reasonable to define also "potential velocity" vs. "kinetic velocity", and claim that in a harmonic oscillator, reaching the highest point involves - both a minimal "kinetic velocity" (i.e. involves what we usually call a rest) - along with a maximal "potential velocity", whereas reaching the lowest point involves - both a maximal "kinetic velocity" (i.e. involves what we usually call the actual velocity) - along with a minimal "potential velocity". Thus we can also define "mechanical velocity" as the sum of "kinetic velocity" + "potential velocity", and claim that the mechanical velocity is a conserved quantity - at least as far as a harmonic oscillator is concerned.
Reasonable?
Note that I could also ask an analogous question - as to the concept of "potential momentum", but this term is already used in the theory of hidden momentum for another meaning, so for the time being I'm focusing on velocity.
HOTmag (talk) 12:26, 29 December 2024 (UTC)
- 'kinetic velocity' is just 'velocity'. 'potential velocity' has no meaning. Andy Dingley (talk) 13:56, 29 December 2024 (UTC)
- Per my suggestion, the ratio between distance and time is not called "velocity" but rather "kinetic velocity".
- Further, per my suggestion, if you don't indicate whether the "velocity" you're talking about is a "kinetic velocity" or a "potential velocity" or a "mechanical velocity", the very concept of "velocity" alone has no meaning!
- On the other hand, "potential velocity" is defined as the difference between the "mechanical velocity" and the "kinetic velocity"! Just as, this is the case if we replace "velocity" by "energy". For more details, see the example above, about the harmonic oscillator. HOTmag (talk) 15:14, 29 December 2024 (UTC)
- You could define the potential velocity of a body at a particular height as the velocity it would hit the ground at if dropped from that height. But the sum of the potential and kinetic velocities would not be conserved; rather would be constant. catslash (talk) 18:54, 29 December 2024 (UTC)
- Thank you. HOTmag (talk) 20:07, 29 December 2024 (UTC)
- 'Potential velocity' has no meaning. You seem to be arguing that in a system where energy is conserved, but is transforming between kinetic and potential energy, (You might also want to compare this to conservation of momentum.) then you can express that instead through a new conservation law based on velocity. But this doesn't work. There's no relation between velocity and potential energy.
- In a harmonic oscillator, the potential energy is typically coming from some central restoring force with a relationship to position, nothing at all to do with velocity. Where some axiomatic external rule (such as Hooke's Law applying, because the system is a mass on a spring) happens to relate the position and velocity through a suitable relation, then the system will then (and only then) behave as a harmonic oscillator. But a different system (swap the spring for a dashpot) doesn't have this, thus won't oscillate. Andy Dingley (talk) 00:00, 30 December 2024 (UTC)
- Let me quote a sentence from my original post:
Thus we can also...claim that the mechanical velocity is a conserved quantity - at least as far as a harmonic oscillator is concerned.
- What's wrong in this quotation? HOTmag (talk) 07:52, 30 December 2024 (UTC)
- It is true, not only for harmonic oscillators, provided that you define vpot = − vkin. --Lambiam 09:07, 30 December 2024 (UTC)
- You have defined some arbitrary values for new 'velocities', where their only definition is that they then demonstrate some new conservation law. Which is really the conservation of energy, but you're refusing to use that term for some reason.
- As Catslash pointed out, the conserved quantity here is proportional to the square of velocity, so your conservation equation has to include that. It's simply wrong that any linear function of velocity would be conserved here. Not merely we can't prove that, but we can prove (the sum of the squares diverges from the sum) that it's actually contradicted. For any definition of 'another velocity' which is a linear function of velocity.
- Lambiam's definition isn't a conservation law, it's merely a mathematical identity. The sum of any value and its additive inverse is always zero. Andy Dingley (talk) 14:04, 30 December 2024 (UTC)
- It is a law of conservation of sanity. Lacking a definition of potential energy, other than by having been informed that kinetic energy + potential energy is a conserved quantity, there is not much better we can do. --Lambiam 11:20, 31 December 2024 (UTC)
- We have a perfectly viable definition of potential energy. For a pendulum it's based on the change in height of the pendulum bob against gravity. For some other oscillators it would involve the work done against a spring. Andy Dingley (talk) 16:33, 31 December 2024 (UTC)
- Oops, I mistyped. I meant to write:
- "Lacking a definition of potential velocity, other than by having been informed that kinetic velocity + potential velocity is a conserved quantity, there is not much better we can do."
- --Lambiam 23:32, 31 December 2024 (UTC)
- Oops, I mistyped. I meant to write:
- We have a perfectly viable definition of potential energy. For a pendulum it's based on the change in height of the pendulum bob against gravity. For some other oscillators it would involve the work done against a spring. Andy Dingley (talk) 16:33, 31 December 2024 (UTC)
- It is a law of conservation of sanity. Lacking a definition of potential energy, other than by having been informed that kinetic energy + potential energy is a conserved quantity, there is not much better we can do. --Lambiam 11:20, 31 December 2024 (UTC)
- Let me quote a sentence from my original post:
- You could define the potential velocity of a body at a particular height as the velocity it would hit the ground at if dropped from that height. But the sum of the potential and kinetic velocities would not be conserved; rather would be constant. catslash (talk) 18:54, 29 December 2024 (UTC)
December 30
Saltiness comparison
Is there some test one might easily perform in a home test kitchen to compare the saltiness (due to the concentration of Na cations) of two liquid preparations, without involving biological taste buds? --Lambiam 09:22, 30 December 2024 (UTC)
- Put two equally sized drops, one of each liquid, on a warm surface, wait for them to evaporate, and compare how much salt residue each leaves? Not very precise or measurable, but significant differences should be noticeable. {The poster formerly known as 87.81.230.195} 94.1.223.204 (talk) 10:21, 30 December 2024 (UTC)
- The principle is sound, but the residue from one drop won't be measurable using kitchen equipment -- better to put equal amounts of each liquid in two warm pans (use enough liquid to cover the bottom of each pan with a thin layer), wait for them to evaporate and then weigh the residue! Or, if you're not afraid of doing some algebra, you could also try an indirect method -- bring both liquids to a boil, measure the temperature of both, and then use the formula for boiling point elevation to calculate the saltiness of each! 2601:646:8082:BA0:BD1B:60D8:96CA:C5B0 (talk) 18:22, 30 December 2024 (UTC)
- Presumably the liquid preparations are not simple saline solutions, but contain other solutes - or else one could simply use a hydrometer. It is unlikely that Lambian is afraid of doing some algebra. catslash (talk) 18:57, 30 December 2024 (UTC)
Assuming the liquid preparations are water-based and don't contain alcohols and/or detergents one can measure their rates of dispersion. Simply add a drop of food dye to each liquid and then time how rapidly droplets of each liquid disperse in distilled water. Materials needed: food dye, eye dropper, distilled water, small clear containers and a timer.Modocc (talk) 21:09, 30 December 2024 (UTC)
- The colligative properties of a solution will indicate its molarity, but not identify the solute. Liquid preparations that might be found in a kitchen are likely to contain both salt and sugar. Electrical conductivity is a property that will be greatly affected by the salt but not the sugar (this does not help in distinguishing Na from K ions though). catslash (talk) 22:23, 30 December 2024 (UTC)
- That's what I'm thinking too -- use an ohmmeter to measure the electrical conductivity of the preparation, and compare to that of solutions with known NaCl concentration (using a calibration curve-type method). 73.162.165.162 (talk) 20:18, 31 December 2024 (UTC)
- Quantitative urine test-strips for sodium seem to be available. They're probably covering the concentration range of tens to hundreds millimolar. DMacks (talk) 00:58, 2 January 2025 (UTC)
- Thanks, test strips seem more practical in the kitchen setting than an ohmmeter (why not call it a "mhometer"?), for which I'd need to devise a way (or so I think) to keep the terminals apart at a steady distance. Test strips require a colour comparison, but I expect that a significant difference in salinity will result in a perceptible colour difference when one strip is placed across the other. Only experiment can tell whether this expectation will come true. Salinity is usually measured in g/L; for kitchen preparations a ballpark figure is 1 g/L. If I'm not mistaken this corresponds to (1 g/L) / (58.443 g/mol) ≈ 0.017 M = 17 mM. I also see offers for salinity test strips, 0–1000 ppm, for "Science Education". --Lambiam 11:40, 2 January 2025 (UTC)
- Test strips surely come with a printed color-chart. But if all you are trying to do is determine which is more salty, then that's even easier than quantifying each separately. Caveat for what you might find for sale: some "salinity" tests are based on the chloride not the sodium, so a complex matrix that has components other than NaCl could fool it. DMacks (talk) 18:44, 2 January 2025 (UTC)
- Thanks, test strips seem more practical in the kitchen setting than an ohmmeter (why not call it a "mhometer"?), for which I'd need to devise a way (or so I think) to keep the terminals apart at a steady distance. Test strips require a colour comparison, but I expect that a significant difference in salinity will result in a perceptible colour difference when one strip is placed across the other. Only experiment can tell whether this expectation will come true. Salinity is usually measured in g/L; for kitchen preparations a ballpark figure is 1 g/L. If I'm not mistaken this corresponds to (1 g/L) / (58.443 g/mol) ≈ 0.017 M = 17 mM. I also see offers for salinity test strips, 0–1000 ppm, for "Science Education". --Lambiam 11:40, 2 January 2025 (UTC)
The (uncommon?) terms "relativistic length", and "relativistic time".
1. In Misplaced Pages, the page relativistic length contraction is automatically redirected to our article length contraction, which actually doesn't mention the term "relativistic length" at all. I wonder if there is an accepted term for the concept of relativistic length.
2. A similar qusestion arises, at to the concept of relativistic time: The page relativistic time dilation, is automatically redirected to our article time dilation, which prefers the abbreviated term "time dilation" (59 times) to the term "relativistic time dilation" (8 times only), and nowhere mentions the term "relativistic time" alone (i.e. without the third word "dilation") - although it does mention the term "proper time" for the shortest time. Further, this article doesn't even mention the term "dilated time" either. It does mention, though, another term: coordinate time, but regardless of time dilation in Special relativity. To sum up, I wonder what's the accepted term used for the dilated time (mainly is Special relativity): Is it "coordinate time"? "Relativistic time"?
HOTmag (talk) 09:32, 30 December 2024 (UTC)
- Are you reading these things as "contraction of relativistic length" etc.? It is "relativistic contraction of length" and "relativistic dilation of time". --Wrongfilter (talk) 09:37, 30 December 2024 (UTC)
- When I wrote:
The page relativistic time dilation is automatically redirected to our article time dilation which...nowhere mentions the term "relativistic time" alone (i.e. without the third word "dilation")
, I had already guessed that the term "dilation of relativistic time" (i.e, with the word "dilation" preceding the words "relativistic time") existed nowhere (at least in Misplaced Pages), and that this redirected page actually meant "relativistic dilation of time". The same is true for the redirected page "relativistic length contraction": I had already gussed it didn't mean "contraction of relativistic length", because (as I had already written):the article length contraction...doesn't mention the term "relativistic length" at all
. - Anyway, I'm still waiting for an answer to my original question: Are there accepted terms for the concepts, of relativistic length - as opposed to proper length, and of relativistic time - as opposed to proper time? HOTmag (talk) 10:12, 30 December 2024 (UTC)
- A term that will be understood in the context of relativistic length contraction is relative length – that is, length relative to an observer. --Lambiam 10:55, 31 December 2024 (UTC)
- Thank you. The middle source uses the term "comparative length", rather than "relative length". I couldn't open the third source. HOTmag (talk) 08:04, 1 January 2025 (UTC)
- The text under the graph labelled Comparative length on page 20 of the middle source reads:
- Graph of the relative length of a stationary rod on earth, as observed from the reference frame of a traveling rod of 100cm proper length.
- A similar use of "relative length" can be seen on the preceding page. --Lambiam 10:23, 2 January 2025 (UTC)
- The text under the graph labelled Comparative length on page 20 of the middle source reads:
- Thank you. The middle source uses the term "comparative length", rather than "relative length". I couldn't open the third source. HOTmag (talk) 08:04, 1 January 2025 (UTC)
- A term that will be understood in the context of relativistic length contraction is relative length – that is, length relative to an observer. --Lambiam 10:55, 31 December 2024 (UTC)
- When I wrote:
What did Juan Maldacena say after "Geometry of" in this video?
I was watching this video Brian Greene and Juan Maldacena as they explore a wealth of developments connecting black holes, string theory etc, Juan Maldacena said something right after "Geometry of" Here is the spot: https://www.youtube.com/live/yNNXia9IrZs?si=G7S90UT4C8Bb-OnG&t=4484 What is that? HarryOrange (talk) 20:46, 30 December 2024 (UTC)
- Schwarzschild solution. --Wrongfilter (talk) 21:05, 30 December 2024 (UTC)
- Thank you, its the Juan Maldacena's accent which made me post here. HarryOrange (talk) 21:18, 30 December 2024 (UTC)
December 31
Brightest spot of a discharge tube
What causes the discharge tubes to have their brightest spots at different positions? Nucleus hydro elemon (talk) 13:12, 31 December 2024 (UTC)
- See also the pictures at Gas-filled tube #Gases in use. --CiaPan (talk) 13:26, 31 December 2024 (UTC)
January 1
Two unit questions
- Is there any metric unit whose ratio is not power of 10, and is divisible by 3? Is there any common use for things like "2⁄3 km", "5⁄12 kg", "3+1⁄6 m"?
- Is a one-tenth of nautical mile (185.2 m) used in English-speaking countries? Is there a name for it?
--40bus (talk) 10:41, 1 January 2025 (UTC)
- 1 not that I know of (engineer who has worked with SI for 50 years)
- 2 not that I know of (yacht's navigator for many years on and off)
- Greglocock (talk) 11:35, 1 January 2025 (UTC)
- In Finland, kaapelinmitta is 185.2 m. Is there an English equivalent? --40bus (talk) 18:11, 1 January 2025 (UTC)
- Good article. I was wrong Greglocock (talk) 22:26, 1 January 2025 (UTC)
- The answer can be found by looking up kaapelinmitta on Wiktionary. --Lambiam 00:14, 2 January 2025 (UTC)
What is more physiological (for a right-hander) left-hand drive or right-hand drive?
Has anyone determined whether it is better for a right-hander to have the left hand on the steering wheel and the right hand on the gear shift stick, or the other way round? Are there other tests of whether left-hand drive or right-hand drive is physiologically better (for a right-hander at least)? 178.51.7.23 (talk) 12:03, 1 January 2025 (UTC)
- Supplementary question: I've only driven right-hand-drive vehicles (being in the UK) where the light stalk is on the left of the steering column and the wiper & washer controls are (usually) on the right. On a l-h-drive vehicle, is this usually the same, or reversed? {The poster formerly known as 87.81.230.195} 94.6.84.253 (talk) 12:12, 2 January 2025 (UTC)
- Modern cars are designed for mass production in RH- and LH-drive versions with a minimum difference of parts. Steering columns with attached controls are therefore unchanged between versions. Philvoids (talk) 12:29, 2 January 2025 (UTC)
- In the UK nowadays, are cars still mostly manual transmission, or has automatic become the norm? ←Baseball Bugs carrots→ 12:38, 2 January 2025 (UTC)
- In the UK, sales of new automatics have just recently overtaken manuals - so probably still more manuals than automatics on the road. catslash (talk) 14:37, 2 January 2025 (UTC)
- This may be tied to the rise of EVs, since they have automatic transmissions by default. {The poster formerly known as 87.81.230.195} 94.6.84.253 (talk) 05:29, 3 January 2025 (UTC)
- In the UK, sales of new automatics have just recently overtaken manuals - so probably still more manuals than automatics on the road. catslash (talk) 14:37, 2 January 2025 (UTC)
- In Australia, we drive on the left, and the indicator and wiper stalks are the opposite way to the UK. Having moved back from the UK after 30 years, it took me a while to stop indicating with wipers. TrogWoolley (talk) 05:08, 3 January 2025 (UTC)
- This depends more on where the car came from I think. For European or American cars it tends to be in the UK direction. For Asian cars or I guess those odd Australian made cars which are out there, it tends to be in the other. See e.g. . The UK being a bigger market I think most manufacturers have come to follow the new UK norm for cars they intend to sell there although I suspect to some extent it's still true in the sense that I think most Asian car brands, at least assemble their cars in the EU or maybe the UK if they're destined for the UK (made a lot of sense pre-Brexit) . It sounds like the new UK norm is fairly recent perhaps arising in the 1980s-1990s after European manufacturers stopped bothering changing that part of the production for the reasons mentioned by Philvoids. As mentioned in one of the Reddit threads, the UK direction does make it difficult to adjust indicators while changing gear which seems a disadvantage which is fairly ironic considering the the UK has much more of a preference for manuals than many other RHD places with the other direction. Nil Einne (talk) 04:31, 6 January 2025 (UTC)
For further clarity, AFAICT, LHD vehicles generally have their indicators on the left and wipers on the right. As mentioned, assuming the gear stick is in the middle which AFAIK it is for most cars by now, this seems the better positioning especially on manual cars since you're much more likely to want to need to indicate while changing gear than you are going to want to adjust your wipers even in the rainy UK. The UK being LHT/RHD especially with their own manufactured cars tended to have the indicators on the right and wipers on the left in the more distant past so again the positions that made most sense.
While I don't have a source for this going by the history and comments, it sounds to me like what happened is European manufacturers who were primarily making LHD vehicles, with the UK and Ireland their main RHD markets but still small compared to the LHD market stopped bothering changing positions for RHD vehicles as a cost saving measure. So they began to put wipers on the right and indicators on the left even in their RHD vehicles no matter the disadvantage. I'm not so sure what the American manufacturers did or when and likewise the British but I think they were a fairly small part of the market by then and potentially even for them LHD was still a big part of their target market.
Meanwhile Asian manufacturers however still put their indicators on the right and wipers on the left in RHD vehicles, noting that Japan itself is LHT/RHD. I suspect Japanese manufacturers suspected, correctly, that it well worth the cost of making something else once they began to enter the LHD markets like the US, to help gain acceptance. And so they put the indicators on the left and wipers on the right for LHD vehicles even if they did the opposite in their own home market and continued forever more. Noting that the predominance of RHT/LHD means even for Japanese manufacturers it's generally likely to be their main target by now anyway.
Later I assume South Korea manufacturers and even later Chinese felt it worth any added cost to increase acceptance of their vehicles in LHT/RHD markets in Asia and Australia+NZ competing against Japanese vehicles which were like this. And this has largely continued even if it means they need to make two different versions of the steering column or whatever. It sounds like the European and American brands didn't bother but they were primarily luxury vehicles in such markets so it didn't matter so much.
This lead to an interesting case for the UK. For the Asian manufacturer, probably many of them were still making stuff which would allow them to keep putting the indicators on the right and wipers on the left for RHD vehicles as they were doing for other RHD markets mostly Asian. And even if they were assembling them in the EU, I suspect the added cost of needing to ship and keep the different components etc and any difference it made to the assembly line wasn't a big deal.
So some of did what they were doing for the Asian markets for vehicles destined for UK. If they weren't assembling in the EU, it made even more sense since this was likely what their existing RHD assembly line was doing. But overtime the UK basically adopted the opposite direction as the norm no matter the disadvantages to the extent consumers and vehicle enthusiast magazines etc were complaining about the "wrong" positions. So even Asian manufacturers ended up changing to the opposite for vehicles destined to the UK to keep them happy. So the arguably better position was abandoned even in cases where it wasn't much of a cost saving measure or might have been even adding costs.
- This depends more on where the car came from I think. For European or American cars it tends to be in the UK direction. For Asian cars or I guess those odd Australian made cars which are out there, it tends to be in the other. See e.g. . The UK being a bigger market I think most manufacturers have come to follow the new UK norm for cars they intend to sell there although I suspect to some extent it's still true in the sense that I think most Asian car brands, at least assemble their cars in the EU or maybe the UK if they're destined for the UK (made a lot of sense pre-Brexit) . It sounds like the new UK norm is fairly recent perhaps arising in the 1980s-1990s after European manufacturers stopped bothering changing that part of the production for the reasons mentioned by Philvoids. As mentioned in one of the Reddit threads, the UK direction does make it difficult to adjust indicators while changing gear which seems a disadvantage which is fairly ironic considering the the UK has much more of a preference for manuals than many other RHD places with the other direction. Nil Einne (talk) 04:31, 6 January 2025 (UTC)
- In the UK nowadays, are cars still mostly manual transmission, or has automatic become the norm? ←Baseball Bugs carrots→ 12:38, 2 January 2025 (UTC)
- I've driven different (automatic) left-hand-drive vehicles with the light stalk on each side, but left side has been more common. Perhaps because the right hand is more likely to be busy with the gear shift? (Even in the US, where automatic has been heavily dominant since before I learned to drive.) -- Avocado (talk) 17:32, 2 January 2025 (UTC)
- Modern cars are designed for mass production in RH- and LH-drive versions with a minimum difference of parts. Steering columns with attached controls are therefore unchanged between versions. Philvoids (talk) 12:29, 2 January 2025 (UTC)
- It's better for a right-hander to have both hands on the steering wheel regardless of where the gear lever is. See Rule 160. I suspect the same goes for a left-hander. Bazza 7 (talk) 14:39, 2 January 2025 (UTC)
- I suppose that the question is whether right-handers have an easier time operating the gear stick when changing gears in manual-transmission cars designed for left-hand traffic, with the steering wheel on the right (like in the UK) or right-hand traffic, with the steering wheel on the left (like in most of continental Europe). Obviously, drivers will use their hand at the side where the gear stick is, so if it is in the middle and the driver, behind the wheel, sits in the right front seat, they'll use their left hand, regardless of their handedness. But this may be more awkward for a rightie. Or not.
- --Lambiam 16:30, 2 January 2025 (UTC)
- In my personal experience (more than 10 years driving on each side of the road, in all four combinations of car handedness and road handedness) the question which hand to use for shifting gears is fairly insignificant. Switching from one type of car to the other is a bit awkward though. —Kusma (talk) 18:33, 2 January 2025 (UTC)
- My first car, a Hillman Minx, had the gearstick on the left and the handbreak on the right, which was a bit of a juggle in traffic. Alansplodge (talk) 19:13, 3 January 2025 (UTC)
- In my personal experience (more than 10 years driving on each side of the road, in all four combinations of car handedness and road handedness) the question which hand to use for shifting gears is fairly insignificant. Switching from one type of car to the other is a bit awkward though. —Kusma (talk) 18:33, 2 January 2025 (UTC)
Distinguishing a picture of a sunset from the picture of a sunrise?
Is there a way (if you don't know which way is west and which way is east in a particular location) to distinguish a picture of a sunset from the picture of a sunrise? 178.51.7.23 (talk) 12:08, 1 January 2025 (UTC)
- Generally, no, but there are a few tricks that sometimes work. In dry sunny weather, there's more dust in the air at sunset (due to thermals) than at sunrise, making the sky around the sun redder at sunset. But in moist weather, mist has the same effect at sunrise. If the picture is good enough to see sunspots, comparing the distribution of sunspots to the known distribution of that day (this is routinely monitored) tells you where the North Pole of the sun is. At sunset, the North Pole points somewhat to the right; at sunrise, to the left. If you see any cumulus or cumulonimbus clouds in the picture, it was a sunset, as such clouds form during the day and disappear around sunset, but absence of such clouds doesn't mean the picture was taken at sunrise. A very large cumulonimbus may survive the night. Cirrus aviaticus clouds are often very large, expanding into cirrostratus, in the evening, but are much smaller at dawn as there's more air traffic during the day than at night, making the upper troposphere more moist towards the end of the day. Cirrostratus also contributes to red sunsets and (to lesser extend, as there's only natural cirrostratus) red sunrises. Dew, rime, flowers and flocks of birds may also give an indication. And of course human activity: the beach is busier at sunset than at sunrise. PiusImpavidus (talk) 13:41, 1 January 2025 (UTC)
- Supposing the photograph has high enough resolution to show Sunspots it can be helpful to know that the pattern of spots at sunrise is reversed left-right at sunset. Philvoids (talk) 13:21, 3 January 2025 (UTC)
- At the equinox, the disk of the Sun with its pattern of sunspots appears to rotate clockwise from sunrise to sunset by 180 degrees minus twice your latitude (taking north positive). At my place, that's 75 degrees. Other times of the year it's less; at the start and end of polar day and polar night, there's no rotation. Sunset and sunrise merge then.
- And I forgot to mention: cirrostratus clouds will turn red just after sunset or just before sunrise. At the exact moment of sunrise or sunset, they appear pretty white. PiusImpavidus (talk) 17:06, 3 January 2025 (UTC)
- I differ: the same rotation is involved everywhere on Earth. If you stand on tiptoe at a N. or S. pole to take a picture of the Sun it is you who must pirouette 15 degrees per hour to keep facing the Sun. The Earth rotates you at this rate at all non-polar locations. If you stand within the arctic or antarctic circles, for parts of the year the 24-hour night or 24-hour daylight seem to prevent photographs of sunrise or sunset. However the terms "sunrise" and "sunset" can then be interpreted as times that are related to particular timezones which are generally assigned by longitude. In photographing the 24-hour Sun the equatorial rise and set times for your own longitude are significant elevation maxima worth mentioning even though the minimum elevation remains above the horizon. I maintain that the sunspot pattern observed from any location on Earth rotates 360 degrees per 24 hours and that "night", the darkness from sunset to sunrise, is when the Earth's bulk interrupts one's view of the rotation but not the rotation itself which is continuous.
- Taking the Earth as reference frame, the Sun rotates around the Earth's spin axis. The observer rotates around his own vertical axis. The better both axes are aligned, the smaller the wobble of the Sun. In the northern hemisphere, it rotates clockwise from about 6 till 18 by 180 degrees minus twice your latitude and counterclockwise at night, in the southern hemisphere it's the opposite. Try a planetarium program if you want to see it. Stellarium shows some sunspots, does things right and is free and open source. PiusImpavidus (talk) 10:27, 5 January 2025 (UTC)
- We deprecate the obselete Geocentric model and suggest Misplaced Pages references that are free and just one click away (no extra planetarium software needed). The axes of rotation of the Sun and Earth have never in millions of years aligned: the Ecliptic is the orbital plane of Earth around the Sun and Earth currently has an Axial tilt of about 23.44° without "wobbling" enough from this to concern us here. Philvoids (talk) 14:56, 5 January 2025 (UTC)
- This isn't my field but sunspots aside, if you know the location and date, I assume the appearance of other astronomical objects like the moon or rarely another star probably Venus, in the photograph should be enough to work out if it's a sunset or sunrise. That said, to some extent by taking into account other details gathered from elsewhere's I wonder if we're going beyond the question. I mean even if you don't personally know which is east or west at the time, if you can see other stuff and you know the location or the stuff you can see is distinctive enough it can be worked out, you can also work out if it's sunset or sunrise just by working out if it's east or west that way. Nil Einne (talk) 03:54, 6 January 2025 (UTC)
- In my experience (Southern England) they tend to be pinker at dawn and oranger(!) at dusk. {The poster formerly known as 87.81.230.195} 94.6.84.253 (talk) 03:23, 4 January 2025 (UTC)
- Pink clouds must result from blending of reddish clouds with the blue sky behind. There's actually more air between the observer and the clouds than behind the clouds, but for that nearby air the sun is below the horizon. PiusImpavidus (talk) 10:27, 5 January 2025 (UTC)
- The questioner asks for interpretation of a single picture. It is beside the point that more would be revealed by a picture sequence such as of changing cloud colours. Philvoids (talk) 12:41, 4 January 2025 (UTC)
- I differ: the same rotation is involved everywhere on Earth. If you stand on tiptoe at a N. or S. pole to take a picture of the Sun it is you who must pirouette 15 degrees per hour to keep facing the Sun. The Earth rotates you at this rate at all non-polar locations. If you stand within the arctic or antarctic circles, for parts of the year the 24-hour night or 24-hour daylight seem to prevent photographs of sunrise or sunset. However the terms "sunrise" and "sunset" can then be interpreted as times that are related to particular timezones which are generally assigned by longitude. In photographing the 24-hour Sun the equatorial rise and set times for your own longitude are significant elevation maxima worth mentioning even though the minimum elevation remains above the horizon. I maintain that the sunspot pattern observed from any location on Earth rotates 360 degrees per 24 hours and that "night", the darkness from sunset to sunrise, is when the Earth's bulk interrupts one's view of the rotation but not the rotation itself which is continuous.
- Supposing the photograph has high enough resolution to show Sunspots it can be helpful to know that the pattern of spots at sunrise is reversed left-right at sunset. Philvoids (talk) 13:21, 3 January 2025 (UTC)
- Recalling Leonard Maltin's comment about the Green Berets movie, which was filmed in the American state of Georgia: "Don't miss the closing scene, where the sun sets in the east!" ←Baseball Bugs carrots→ 22:37, 5 January 2025 (UTC)
- Which you can only tell if you know which way is east in the image. Maltin, or his writer, appears to have assumed that Vietnam has a seacoast only on the east, which is wrong. --142.112.149.206 (talk) 03:46, 6 January 2025 (UTC)
- Georgia has only an eastern seacoast. ←Baseball Bugs carrots→ 10:31, 6 January 2025 (UTC)
- Black seas matter! Philvoids (talk) 14:18, 6 January 2025 (UTC)
- So what. Bugs? The claim is about the setting, not the filming location. --142.112.149.206 (talk) 07:30, 7 January 2025 (UTC)
- But as it was filmed in (The US State of) Georgia, it must actually show a sunrise, regardless of what the story line says – how do you know that wasn't what Maltin actually meant? {The poster formerly known as 87.81.230.195} 94.6.84.253 (talk) 10:35, 7 January 2025 (UTC)
- Because things filmed for movies often are not actually what they are shown as being, so that wouldn't be interesting and Maltin's guide wouldn't waste space on it. If what they show it as — for example, in Krakatoa, East of Java — is wrong or impossible, that could be interesting. --142.112.149.206 (talk) 17:43, 8 January 2025 (UTC)
- I assume (not having seen the film) that, in the story line of The Green Berets , the closing scene takes place in the late afternoon, which means it shows a sunset. The plot section of our article on the film places the closing scene at or near Da Nang, which is on the east coast of Vietnam. This means that Maltin did not make an unwarranted assumption; he was just seeking an excuse to bash the film. --Lambiam 13:55, 7 January 2025 (UTC)
- I've seen The_Green_Berets and confirm that the closing scene with End title is an offshore sunset. Philvoids (talk) 20:12, 7 January 2025 (UTC)
- But as it was filmed in (The US State of) Georgia, it must actually show a sunrise, regardless of what the story line says – how do you know that wasn't what Maltin actually meant? {The poster formerly known as 87.81.230.195} 94.6.84.253 (talk) 10:35, 7 January 2025 (UTC)
- Georgia has only an eastern seacoast. ←Baseball Bugs carrots→ 10:31, 6 January 2025 (UTC)
- Which you can only tell if you know which way is east in the image. Maltin, or his writer, appears to have assumed that Vietnam has a seacoast only on the east, which is wrong. --142.112.149.206 (talk) 03:46, 6 January 2025 (UTC)
January 6
Does the energy belonging to an electromagnetic field, also belong (or is considered to belong) to the space carrying that field?
HOTmag (talk) 18:41, 6 January 2025 (UTC)
- It would be unusual to express the situation in such terms. Since the notion of energy "belonging to" some entity is not itself a physical concept – any practical approach to energy bookkeeping that satisfies the law of conservation of energy will do – this cannot be said to be wrong. It is, however, (IMO) not helpful. Does an apple belong to the space it occupies? Or does that space belong to the apple? --Lambiam 23:37, 6 January 2025 (UTC)
- First, I let you replace the notion of energy "belonging to" some entity, by the notion of energy "attributed to" some entity, or by the notion of energy "carried by" some entity, and the like. In other words, I'm only asking about the abstract relation (no matter what words we use to express it), between the energy and the space carrying the electromagnetic field, rather than about the specific term "belong to".
- Second, I'm only asking about what the common usage is, rather than about whether such a usage is wrong or helpful.
- The question is actually as follows: Since it's accepted to attribute energy to an electromagnetic field, is it also accepted to attribute energy to the space carrying that field?
- So, is your first sentence a negative answer, also to my question when put in the clearer way I've just put it? HOTmag (talk) 03:28, 7 January 2025 (UTC)
- The answer remains the same. It would be a highly unusual use of language to "attribute" electromagnetic energy to a volume of space, in quite the same way as it would be strange to "attribute" the mass of an apple to the space the apple occupies. But as long as an author can define what they mean by this (and that meaning is consistent with the laws of physics), it is not wrong. --Lambiam 13:21, 7 January 2025 (UTC)
- An electromagnetic field that we may (even tenuously) conceive to have the form of a massless photon has, like the aforementioned apple (a biological mass) its own unique history, that being a finite path in Spacetime. I reject apparent effort to give spacetime any kind of identity capable of owning, or even anticipating owning or remembering having owned anything at all. Concepts of owning, attributing or whatever synonymous wordplay one chooses all assume identification that can never be attached to the spacial location of an em field. The energy of the photon is fully accounted for, usually as heat at its destination, when it is absorbed and no lasting trace remains anywhere. I am less patient than Lambian in my reaction to this OP who under guise of interest in surveying "what is commonly accepted" returns in pursuit of debate by patronisingly "allowing" us to reword his question in abstract "words that don't matter" to make it purportedly clearer and worth responders' time. Philvoids (talk) 14:55, 7 January 2025 (UTC)
- Thank you Lambiam for your full answer. I always appreciate your replies, as well as your assuming good faith, always. HOTmag (talk) 15:08, 7 January 2025 (UTC)
- The answer remains the same. It would be a highly unusual use of language to "attribute" electromagnetic energy to a volume of space, in quite the same way as it would be strange to "attribute" the mass of an apple to the space the apple occupies. But as long as an author can define what they mean by this (and that meaning is consistent with the laws of physics), it is not wrong. --Lambiam 13:21, 7 January 2025 (UTC)
January 8
Australian for double-decked bridge?
On a topographic map (or on any other kind of map, like a track diagram), what symbol represents a railroad bridge which is directly above and collinear with another railroad which is either on a lower deck of the same bridge, or else is at grade (as in, for example, a narrow-gauge line on a coal trestle above a standard-gauge one)? 2601:646:8082:BA0:48AA:9AA4:373D:A091 (talk) 06:35, 8 January 2025 (UTC)
- Our List of multi-level bridges#Australia article only lists two multi-level bridges in Australia, neither of which seem to fit your criteria. Alansplodge (talk) 19:16, 8 January 2025 (UTC)