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::::<small>How about non-intensive purposes? --] (]) 17:39, 10 March 2014 (UTC)
::::<small>How about non-intensive purposes? --] (]) 17:39, 10 March 2014 (UTC)
:::::That was for the benefit of ], whom I won't name here. ] (]) 17:15, 11 March 2014 (UTC)</small>
:::::That was for the benefit of ], whom I won't name here. ] (]) 17:15, 11 March 2014 (UTC)</small>
:::::: <small> I'm not even watching this page, so I haven't even seen your invitation to outrage (which I would politely decline). -- ] </sup></font></span>]] 21:31, 11 March 2014 (UTC) </small>
:::::: <small> I'm not even watching this page, so I haven't even seen your invitation to outrage (which I would politely decline). -- ] </sup></font></span>]] 21:31, 11 March 2014 (UTC)
:::::::'']'', ]! You are the one who used the "all intensive purposes" phrase as a joke just this month, and my allusion to it was meant as an ''homage'', not an ''outrage''. ] (]) 03:38, 12 March 2014 (UTC)</small>
:] might also work. See also ], which specifically mentions rapid quenching. ] (]) 15:39, 10 March 2014 (UTC)
:] might also work. See also ], which specifically mentions rapid quenching. ] (]) 15:39, 10 March 2014 (UTC)
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Lungs, according to this The compressability of the air in whale's lungs help keep them neutrally buoyant at any depth. As they dive, their lungs compress, and thus have a smaller volume, which makes the whale more "dense" and thus maintains buoyancy at the lower depth, where the water is also more dense. In this way, the whale's lungs work akin to a swim bladder in fish, which is interesting because swim bladders are homologous to lungs in land animals. Regarding the Avocado; the modern farm-raised avocado survives because of human cultivation. It has been modified extensively from its wild ancestors. Like maize, it is unlikely that cultivated avocado would survive without humans to keep them going. Avocado have been cultivated for like 10,000 years, so there was time for humans to take over when the animals they coevolved with died out. --Jayron3203:34, 7 March 2014 (UTC)
Interesting. thank you, I came across this article Sink or Swim and it seemed really interesting but I couldn't figure out how to find the whole article and not just the abstract.
also how long must the avocado plant have survived without the animals that spread it's seeds being alive before human intervention?
It doesn't have to be any time at all. It's quite likely that the original seed-spreading animals which co-evolved with the wild avocado (as noted in the Misplaced Pages article avocado were still alive 10,000 years ago. That same Misplaced Pages article notes that there's evidence of human cultivation of Avocado 10,000 years ago. I'm just speculating, but it's clear that something like that happened... --Jayron3203:46, 7 March 2014 (UTC)
Regarding the whales: Jayron's answer is all bassackwards, because water is practically incompressible and does not become "more dense" as he said. The real answer is, whales control their depth with their fins, just like a submarine -- all that their lungs do is make their buoyancy approximately neutral so they don't sink (same thing as with a fish's swim bladder). 24.5.122.13 (talk) 07:39, 7 March 2014 (UTC)
Here's Jayron's comment, for your reference: "As they dive, their lungs compress, and thus have a smaller volume, which makes the whale more "dense" and thus maintains buoyancy at the lower depth, where the water is also more dense." (emphasis mine) And don't you DARE call me "dearie"!!! 24.5.122.13 (talk) 10:20, 7 March 2014 (UTC)
It's a burden being right all the time. In case you don't wish to click that, Dearie, "So, the density of ocean water increases and increases as you go to the bottom of the ocean. The deep ocean is layered with the densest water on bottom and the lightest water on top." --Jayron3210:47, 7 March 2014 (UTC)
Yeah right -- the increase in density from top to bottom is no more than 0.5% AT MOST, which is not nearly enough to matter, moron! 24.5.122.13 (talk) 11:25, 7 March 2014 (UTC)
IP 24.5: Don't insult other users, this is not Yahoo Answers.
On top of this, 0.5% doesn't look like much, but only the air inside the lungs is more compressible, so it could be enough. OTOH, since the blood and all the solid matter that make up the whale is slightly compressible, too, I can't say for sure. - ¡Ouch! ( / more pain) 11:42, 7 March 2014 (UTC)
This article also discusses the role of lungs in maintaining neutral buoyancy in various sea animals. It should be noted that calling me a "moron" doesn't make that article disappear. --Jayron3212:15, 7 March 2014 (UTC)
If that graph in the link is right, that's only 3 parts in a thousand density difference, mostly near the top of the ocean (which is also where the air would be compressed, but even much faster). From it looks like a bottlenose dolphin has a tidal volume of 10 liters (which is close to all of its lung capacity due to its adaptation) and from the article it weighs about 250 kg, so that is 1/25 of the animal's weight in buoyancy that is lost. So it would seem that the lungs very much overcompensate for the density increase of seawater, which is essentially negligible. Worse, the density change is in the "wrong direction", dragging the dolphin down when it is deep. As a rule, swim bladders change in volume quite slowly to mediate a long-term change in neutral buoyancy - but whales, diving all the way down and back in a short time, need to move much faster than they would sink as dead weight. Wnt (talk) 15:22, 7 March 2014 (UTC)
The link to "This Article" that Jayron gives above answers the OP's question perfectly, and makes amazing reading!! It seems that Sperm Whales at least, control their buoyancy by heating or cooling (using hot blood or cool seawater) their spermaceti organ to alter the volume of the spermaceti oil. That's smart engineering. Thanks Jayron. 122.108.177.30 (talk) — Preceding undated comment added 08:17, 8 March 2014 (UTC)
"The compressability of the air in whale's lungs help keep them neutrally buoyant at any depth" is not supported by the linked article. Any scuba diver would be puzzled by such a claim, because the instability of buoyancy underwater with depth due to the relative compressibility of gasses (primarily the air in one's lungs) makes buoyancy control tricky nearer the surface. Additional buoyancy control (energetic swimming, in the case of the whale) is needed precisely to combat this instability. The article indicates that to dive, the whale has to expend considerable energy to overcome the initial positive buoyancy until the air in the lungs has compressed sufficiently. The mechanism of oil density control is clearly to conserve energy during both the descent (with negative or not-so-positive buoyancy) and the ascent (with positive buoyancy), which may be a considerable distance (up to 3 km each way). Once deep enough, the contribution to buoyancy due to the air in the lungs will be essentially negligible, and buoyancy will be comparatively stable. So, the air in the lungs is far from a help: it is a hindrance to buoyancy control. —Quondum18:09, 8 March 2014 (UTC)
The reaction between concentrated HNO3 and some metals
Can you give me the balanaced chemical equation of rection between concentrated HNO3 and Fe, Co, Al, Cr which should produce the metals' oxides. But I don't know what the other products are. Is it NO or NO2 like the reaction with copper? --G.Kiruthikan (talk) 14:32, 7 March 2014 (UTC)
You would not make the oxides. You make the nitrates. In concentrated nitric acid, you make NO2, in dilute nitric acid, you make NO. For copper, the basic reactions are:
For any other metal that reacts with nitric acid, you'll get similar reactions, excepting you'll make whatever is that metals most stable oxidation state. For Iron, for example, I'd expect Fe(NO3)3. --Jayron3218:47, 7 March 2014 (UTC)
I am thinking about teaching meyself GR with the only the internet and maybe a few texts I can buy in an ebook format and no expert guidance. Is this a achivable goal? How much time should I set aside for it? And what resources (Ideally available online on a digital format) would you recomend for it?Diwakark86 (talk) 15:28, 7 March 2014 (UTC)
This depends heavily on your background. Are you familiar with linear algebra and calculus? If so, you should be able to teach yourself basic GR, albeit with difficulty. Check out Introduction to General Relativity by Lewis Ryder and Leonard Susskind's lecture series at Stanford University: . --Bowlhover (talk) 16:03, 7 March 2014 (UTC)
The answer to that question is going to depend a lot on where you're starting from, and where you're hoping to get to. MIT offers an open courseware version of their course in general relativity 8.962, which I expect would give a reasonable working knowledge of the topic. If you were to actually take the course, you'd be looking at three hours per week of lectures, times fifteen weeks, plus probably at least as much time spent on assignments and homework to try to apply what you had learnt—call it a hundred-plus hour commitment all told.
However, that presupposes that you are prepared to take a graduate-level course, and that you already have a reasonably firm grasp of the prerequisite material. From the syllabus,
The course catalog lists Differential Equations (18.03), Linear Algebra (18.06), and Electromagnetism II (8.07) as prerequisites. Students should also be familiar with Lagrangians and action principles, Green's functions, and numerical analysis (some homework assignments require the numerical solution of systems of differential equations).
There's some pretty heavy mathematical lifting involved in GR. (Note that the prerequisite courses specified each have their own list of prerequisites as well.) There's a lot of foundational knowledge that you would be expected to have to build on. You haven't specified what level of knowledge and experience you're coming in with, so it's hard to say how long it would take you to get up to speed.
The other side of the question is what you are hoping to do with it. General relativity is something that physicists can study and work with (and argue over) for entire careers; there's a very, very long road between knowing something about GR and knowing most of GR. TenOfAllTrades(talk) 16:12, 7 March 2014 (UTC)
Good free of charge comprehensive lectures. This is a good text, but it won't work for you if you don't have the rght attitude toward studying. 't Hooft already gves a hint of that in the introduction when he writes: "I see no reason to shield students against the phenomenon of changes of convention and notation. Such transitions are necessary whenever one switches from one field of research to another. They better get used to it.". The advantage of this text of just 72 pages over most other texts is that while you only need the same minimal knowledge to read other the introductory GR texts, if you complete these lecture notes, you will be able to do more advanced calculations, e.g. compute the amount of gravitational radiation emitted by a rotating object from first principles. Other lecture notes may also lead to the same end result but they typically comprise of hundreds of pages. Count Iblis (talk) 17:55, 7 March 2014 (UTC)
The PDF Count Iblis linked to looks good, but if you find it to be too condensed, you may need to buy a textbook to self-study. Unfortunately, the book I would recommend for that purpose doesn't appear to be available in a digital format.
I started off trying to self-study GR from Schutz, but I didn't get very far in that book because I found myself feeling like I wasn't really understanding the differential geometry being used. So I gave up on Schutz, and started over by self-studying MTW. Self-studying MTW worked much better, since MTW gives very thorough explanations of the needed differential geometry concepts. However, MTW's thoroughness made studying it take quite a while; it's huge. I'm not certain, but I'm under the impression that Wald is the most widely-used graduate-level GR textbook. I own a copy of Wald, and use it as a reference, but I think it would be similar to Schutz in that its coverage of differential geometry would be too dense if you haven't already had some exposure to the subject. I also have a copy of Hartle that I reference occasionally, and of the four books I own that give a broad coverage of the basics of GR, Hartle looks like it's easily the one that's the most accessible at an introductory level. It also has the plus of being considerably newer than any of the other three books. Hartle unfortunately didn't exist yet when I was self-studying GR, or I think I would have chosen that as my first book on the subject. In short, I would recommend Hartle as the book to initially learn the basics of GR from, and then follow that with Wald if you're feeling like you want a more rigorous understanding after finishing Hartle. Hartle's book is "Gravity: An Introduction to Einstein's General Relativity", and Wald's book is "General Relativity". Red Act (talk) 05:59, 8 March 2014 (UTC)
I have a pack of Gnocchi that the packet says will cook in 2 minutes but for 500g it needs 5L of water. Simply south......disorganising disorganisation for just 7 years19:44, 7 March 2014 (UTC)
I'm inclined to believe the packet. To cook gnocchi you need a large pan of boiling water, and you need plenty of space around the gnocchi so (a) the water doesn't cool down too much when you put them in and (b) they don't stick together. If you don't have a pan big enough, just cook them 10 or so at a time. They sink when you first put them in, and when they are done they float to the surface. --TammyMoet (talk) 19:53, 7 March 2014 (UTC)
I don't get the concept of cooking them 10 at a time. For the gnocchi I'm familiar with, it would take an hour to cook a pound that way, and they'd be ruined by the time you finished. If you don't have a pot that is quite large enough, I would say try it anyway, and very gently stir them once or twice to keep them from clumping together too much. Looie496 (talk) 20:08, 7 March 2014 (UTC)
Most of the time cooking pasta you ad little salt and oil to the water. The oil, especially, helps keep the pasta from sticking, it being necessary to lightly stir the gnochhi with a slatted spoon in the oil at the surface to distribute the oil on their surfaces. Salt adds flavor, and salt will raise the boiling temperature of the water (although I'd expect no one wants to put five moles of salt in their pasta water). Does the recipe not say to add oil to the water? μηδείς (talk) 22:22, 7 March 2014 (UTC)
The boiling point elevation provided by the addition of any amount of salt suitable for cooking is negligible — there will be significantly more variation in boiling point due to day-to-day changes in atmospheric pressure. From a culinary perspective, adding oil to the cooking water is strongly discouraged. Coating the pasta with oil creates a barrier that prevents the pasta from absorbing any sauce; worse still, it encourages any sauce on the outside of the cooked pasta to just slide off. TenOfAllTrades(talk) 23:28, 7 March 2014 (UTC)
Yes, that's what I said, who wants to add five moles of salt to 5L of water? (You do add about .1/mol/liter for hard boiled eggs--it makes peeling them a snap, although the yolks will green if you overcook them.) As for the oil in the pasta water, it's been in every bible in every restaurant I have ever worked in, and on every container of pasta I can remember having bothered to read the instructions on.
Some recipes do call for very large amounts of added salt per volume of water, which can change the boiling temp by a small amount that does have some noticeable effect on cooking times. Also, the concentration of salt in the water is (roughly) hypertonic, leading to salt absorption by the pasta, which is often desired. As to oil, that's mostly personal taste. You are right about that tending to reduce absorption of sauce, but some people prefer pasta covered in sauce, as opposed to pasta saturated with sauce. This is also a matter of amount, surely a few cc of oil will prevent sticking without having much effect on permeability (my source on all this is memory of On_Food_and_Cooking; I have no idea what pages :) The main point relevant to the OP's question is that large volumes of water are often desirable, as the addition of pasta to boiling water then causes less temperature drop, as TammyMoet has already explained. SemanticMantis (talk) 00:22, 8 March 2014 (UTC)
Pasta needs to absorb a lot of water, that's why you need to boil it in a big pan of water. If you use less water than specified then the boiling time increases, if you add too little then it won't get boiled properly (if you add less water than the cooked pasta will have to absorb). Count Iblis (talk) 00:07, 8 March 2014 (UTC)
That's true, but the most important thing is noted by TammyMoet above. You need lots of water so the individual pasta pieces (whatever pasta you are cooking) have room to spread out, cook evenly, and avoid sticking. You need space between all the noodles/dumplings/strands/whatever so that it cooks properly. This site recommends 4-6 quarts of water per pound of dry pasta. --Jayron3201:54, 8 March 2014 (UTC)
Engineers in industry
Other than in engineering consulting, contracting/construction, and infrastructure maintenance and management, where do engineers work? Clover345 (talk) 23:27, 7 March 2014 (UTC)
Any technology-based company, in any industry, is likely to employ engineers. There are many different kinds of engineer.--Srleffler (talk) 16:15, 11 March 2014 (UTC)
Chemical engineering is a major employment field worldwide, as a result of the world's burgeoning energy, petrochemical and pharmaceutical markets. A decent chemical engineer will ALWAYS have work. Biomedical engineers can work in hospitals maintaining infrastructure and medical devices, or they can be hired by medical device manufacturers (although the rate at which income of medical device manufacturers is taxed under ObamaCare seems to assure these jobs will be outsourced from the United States in the future, and no sane startup in the medical device field will incorporate in the United States when Eire and the rest of the EU constitute comparative tax havens for that industry). loupgarous (talk) 23:59, 11 March 2014 (UTC)
As SemanticMantis mentioned above, government also employs many engineers. State (US) governments are one of the leading employers of civil engineers, since design and maintenance of infrastructure such as roads and highways, sewers, drainage structures, dams are chiefly state responsibilities. The US government also employs a wide range of engineers in regulatory agencies (the Nuclear Regulatory Commission hires nuclear engineers, the Federal Communications Commission employs electrical and electronic engineers, The Environmental Protection Agency doubtless has its share of various engineering disciplines, etc.).
But the Federal Government actually does work that is not regulatory in nature, and engineers work in these roles, too. The Department of Energy hires a wide variety of engineers to maintain its various nuclear-related installations. The US Army Corps of Engineers hires hydrologists and other civil engineers, and the US Department of Defense's other agencies hire just about every imaginable engineering specialty, because modern war isn't just about weapons (Eglin Air Force Base, among other things, hires a goodly number of engineers to design and test bombs; and the Natick Soldier Research, Development and Engineering Center hires engineers in various specializations to design and test just about anything a soldier might wear, use or aim), it's about combat and civil engineering in various areas of operations. loupgarous (talk) 23:47, 11 March 2014 (UTC)
Since there are no answers yet, you might be able to do so with different types of glass than soda-lime glass which is mostly silicon dioxide. Sulfur forms a glass when quenched from a molten state, but it reverts to crystalline form over night if kept at room temperature. The fact sulfur glass is ductile at room temperatre and rather quickly recrystalizes would make it unsuitable at room temperature. I suspect doing the same experiment at a much lower temperature might prevent the reversion to crystal long enough for the formation of PRD's to occur. It would be a very interesting experiment. Hopefully some materials scientist will comment. μηδείς (talk) 20:06, 8 March 2014 (UTC)
Yes, it should. Obsidian still has about the same SiO2 content as normal soda-lime glass, ~75%. So it is basically normal glass for all intensive purposes. When I questioned my bro-in-law on this yesterday, he said basically any quickly-quenched enough non-ductile glass in the broad sense will work. What matters is the compressive mechanics mentioned in the article.μηδείς (talk) 21:13, 9 March 2014 (UTC)
I'm not even watching this page, so I haven't even seen your invitation to outrage (which I would politely decline). -- Jack of Oz21:31, 11 March 2014 (UTC)
DARPA has been at work trying to make explosives by trapping energy in polymer chains of carbon monoxide. The technology for doing so is described in "Pressure-Induced Polymerization of Carbon Monoxide: Disproportionation and Synthesis of an Energetic Lactonic Polymer" by a team of researchers at Lawrence Livermore National Laboratory (for those who don't know, this is one of the United States' two nuclear weapon design labs).
What you get when you throw CO into a diamond anvil cell and/or a large volume press, then turn the pressure way up is a solid polymer that "is metastable at ambient conditions, spontaneously liberating CO2 gases exothermically". In layman's terminology, it blows up. This may actually be the most extreme application of trapping significant amounts of energy in a molecular structure to produce an explosive without recourse to redox or nuclear reactions - which is what the Prince_Rupert's_Drop does. loupgarous (talk) 01:20, 12 March 2014 (UTC)
Name of the juncture between the leg and the pelvis
Hi guys. I'd like to know if there's a particular name for the part of the body where the leg and the pelvis connect, analogous to the armpit where the shoulder and the arm connect. Me searching Misplaced Pages has come up empty, and I'm inclined to believe that the closest of an answer I can get is the perineum, but I don't know it it's correct. Any other ideas? :) --Sky Harbor13:28, 8 March 2014 (UTC)
As Baseball Bugs already told you, you're probably talking about the Hip Joint. Perhaps less likely, you're thinking about the groin? — Preceding unsigned comment added by Krikkert7 (talk • contribs) 16:54, 8 March 2014 (UTC)
"Groin (n) - The crease or hollow at the junction of the inner part of each thigh with the trunk."
Specifically, "Mw" is Weight Averaged Molecular Weight, in contrast "Mn" would be Number Average Molecular Weight, see also Molar mass distribution. The difference between the two reflects the polydispersity of the molecule, something you could read about in our article on polydispersity were it not muddled by IUPAC revisionism. Also, when it's written as "MW" or "FW" it's usually intended as a general abbreviation for "Molecular Weight", "Molar Mass", and/or "Formula Weight". (+)H3N-Protein\Chemist-CO2(-)15:03, 8 March 2014 (UTC)
Mining, rails and wheels made of steel and/or iron.
The rails on a railway and the wheels of a train-wagon are obviously made of top-quality steel, so that it can withstand the pressure, the speed and the weight and not be worn down so easily.
My questions are; would mining-wagons (in the past especially) be made of steel as well or would it be made of iron? Perhaps the wagon itself would be made of iron and the wheels made of steel?
If the wheels had actually been made of iron, would they be quickly worn down and rendered useless on the steel rails? Obvisously, there are less forces involved on a mining-rail than on a modern train-rail. But still, mining-wagons loaded full with stone and frequently going back and forth from the surface to the innermost depths of the mine could possibly be very taxing on iron wheels against steel rails, no?
The first rails were made of wood. The 'trains' were actually wagons pulled by horses. In the XVIII century, the wood was substituted by iron, both on the wheels as on the rails.
There are actually several different standards for railway tires per ASTM A551, based on whether it's a passenger train, freight train, switching locomotive, or rapid transit train. But all of them are basically low-alloy, medium/high carbon steel. The composition spec for passenger trains would correspond to AISI 1050. Switching/rapid transit would use AISI 1080. Both are basically 98+% iron, so it's not a particularly expensive alloy. The strength is a result of the heat treatment. Stopping/starting and wheel slip seem to be more relevant for wear. Mr.Z-man20:09, 8 March 2014 (UTC)
You seem to know your way around train-wheels. Impressive, and your links were educational ones - I did read through them. But mining-wagons is what I am looking at really, not trains, and if you have some knowledge about that or some sources/links to share I would be more than happy for it.
Krikkert7 (talk) 00:01, 9 March 2014 (UTC)
A lot of rail technology was originally developed for mines, so there's a lot of overlap in the history. Prior to around 1850 when the Bessemer process was developed, steel was rather expensive. As OsmanRF34 said, early railways used wood. Cast iron started to appear around 1790, but was brittle and uneven. Wrought iron rails were invented in 1820 by John Birkinshaw. So the material used would likely depend on the time:
Pre-1700 would have almost certainly been wood for both the rails and wheels.
At some point (~1730-1750) they started putting cast iron plates over the wooden rails, then cast iron wheels, then fully cast iron rails.
The brittleness of cast iron means they would have switched to wrought iron rather quickly around 1820. Cast iron rails were probably used mostly in mines; they were almost unusably brittle for steam engines.
By 1900 they were almost certainly using steel, which worked even better than wrought iron and was rapidly becoming cheaper.
For mines, where comfort and speed weren't really a concern, cast iron may have stuck around a bit longer for the wheels because it was cheaper. In trains that used a wheel/tire design, they often used cast iron wheels with wrought iron tires; though most of the pictures that I can find of old mine carts look like 1-piece designs for the wheels. But by 1900 or so, steel was cheap enough that its benefits (higher strength, less brittle) probably outweighed the cost vs cast iron. Note that neither cast iron or wrought iron are pure iron. Pure iron is as soft as brass and is expensive to make. Cast iron has a high carbon content (>2%) and is usually brittle. Wrought iron reduced the carbon content, and was similar to steel except for slag inclusions. For further reading: Wagonway, Mine railway, History of rail transport. Mr.Z-man02:12, 9 March 2014 (UTC)
Another thing to consider is that if something is going to wear down, it's better to be able to just have regular maintenance schedule of changing wheels on the wagons rather than have to close the mine for a complete rail change. I operate a marine railway, where the underwater rails are extremely expensive to replace. The most important source of damage on any fairly low speed rail system is corrugations on the rail surface. (They form in a similar manner to corrugations on a gravel road). This is at it's worst when wheel diameter and the wagon speed are constant. We can't grind our undersea rails flat from time to time, the way the suburban rail operators do to prevent this, so if we could find a source of wheels that wore out rather than damage the rails, we'd jump at it! Tom duF (talk) — Preceding undated comment added 07:32, 9 March 2014 (UTC)
Thanks a lot for all the answers. I didn't expect this much response. Tom DuF, You repair boats then? I'm sure you know of what you speak, but I would have thought that if wheels were made of iron and rails were made of steel, which is obviously an upgrade from iron and stronger, then wheels would be worn out first. I'm sure you can see the way of my thinking. A ship can also weigh a lot, depending on its size as well as other things, so the rails will probably have to endure a lot. But as I said, in your line of work you probably know a thing or two about how weight, pressure and frequent use can effect the metal over time. It's something to think about. Thanks again.
Krikkert7 (talk) 16:02, 9 March 2014 (UTC)
Could matter fusion itself generate the additional gravitational attraction that we call Dark Matter?
Hi All,
Imagine that every instance of atomic matter fusion generates an attractive force to all other instances of atomic matter fusion. In this case, a star containing so many instances of fusion per second would be attracted to all the surrounding stars. Because each star nearby contains so many instances of fusion.
Has nuclear fusion research advanced to the point where this possibility can be ruled out? Or does this fusion-causes-gravitation remain a possibility? Just curious...
(This is a thought in response to dinosaurs-done-in-by-dark-matter that talks about the Sun traveling up and down through the galactic plane on the order of every 15 million years or so...)
What makes dark matter noticeable, I gather, is that its distribution differs from that of visible matter such as stars. —Tamfang (talk) 00:07, 9 March 2014 (UTC)
Agreed. We know how much gravitational attraction comes from the Sun, and if it was more than expected from the Sun's mass, we would have noticed that. The same is true of other stars. The hidden gravitational attraction seems to mostly come from the space between the stars. StuRat (talk) 17:48, 9 March 2014 (UTC)
If the Sun's gravity exceeded what we expect of its mass, we'd overestimate its mass. How would we know it's wrong? —Tamfang (talk) 07:41, 10 March 2014 (UTC)
Ah, the equivalence principle answers my above question: the Sun's movement about the Solar System's center of mass gives us the ratio of its inertial mass to that of Jupiter; this ought to be equal to the ratio between their gravitational masses, but wouldn't be if there were another way to generate Solar gravity. —Tamfang (talk) 07:47, 10 March 2014 (UTC)
The OP might not be wrong, if the fusion is generating sterile neutrinos. Though I don't really know where those come from, if they come from anything ... maybe supernovas? but I'm getting the feeling some other mechanisms (boson decay, inflatons??, oscillations?) have more to do with it? Wnt (talk) 13:54, 10 March 2014 (UTC)
That's not quite what the OP said, but it also won't work. Starting from primordial hydrogen + a little bit of helium you'd need stellar fusion to have processed 90% of the initial mass of the galaxy into sterile neutrinos. We'd have noticed if fusion converted 90% of the mass-energy of the inputs into an undetectable sterile neutrino. --Amble (talk) 14:26, 10 March 2014 (UTC)
March 9
Likely Error in Microphyte Page
The microphyte/microalgae page had an illustration of Spirulina, a cynobacteria. Microalgae are algae, which are eukaryotic while cynobacteria are prokaryotic. The caption for spirulina also included dubious unsourced information about its health benefits. Aslo the algae page listed cynobacteria as both an "included group" and an "excluded group". These errors have all been corrected, but please let me know if I was mistaken. Greg Comlish (talk) 04:32, 9 March 2014 (UTC)
Note the second paragraph of algae, which begins "There is no clear consensus definition of algae." Many sources do include cyanobacteria in "algae," and these claims are sourced in the article. This is in old problem, and the best we can do on WP is acknowledge some of the issues of nomenclature. Still, it doesn't make sense to have a disputed member as an example, when there are plenty of unequivocal mycrophyta that could be pictured - So your edit to microphyte does seem to be an improvement.
I'm not feeling WP:BOLD at the moment, but expect your edit to algae to be reverted once enough people catch wind of it. The truth of the matter is, cyanobacteria are included as algae in some sources, and excluded in others. The list format did make it a bit confusing though. Perhaps the ideal compromise is to have cyanobacteria listed in both "included" and "excluded" sections, with both instances having a footnote that says "some sources include cyanobacteria as an algae, while others do not." -- but the place for this kind of discussion is Talk:Algae, where there is already a whole thread about "prokaryotic algae".
There's a reason why systematics and cladistics are used when biologists want to be careful about describing relationships and group memberships. "Algae" doesn't even have a taxonomic rank, it's just a "group", and a highly polyphyletic one at that. So -- I wouldn't lose too much sleep over trying to nail down a strict scientific definition of this known-to-be-problematic grouping. This is all basically covered in the first three paragraphs of algae, before you made any changes. SemanticMantis (talk) 05:41, 9 March 2014 (UTC)
sinuses and eyes
Recently when I was having an eye test the optician said casually, 'Of course you have sinus problems.' As a result I now wonder whether problems with sinuses affect eyes and/or eyesight. If so, how please? And if not, how did she know? Thank you in advance. — Preceding unsigned comment added by 78.127.60.178 (talk) 08:12, 9 March 2014 (UTC)
It need not have been anything to do with your eyes at all; people with sinus problems have a distinct nasally quality to their voice. It could be that your hair dresser would make the same remark. That said, there are obviously connections between eyes / nose / sinuses (see, for example, photic sneeze reflex) and irritated sinuses can lead to weepy or red eyes. I try not to go to my optometrist deep in hay fever season as I know I'll get weird results. Matt Deres (talk) 13:21, 9 March 2014 (UTC)
If a person's nose/sinuses are plugged up, their tear ducts may no longer drain properly, resulting in watery eyes, and they may also be suffering from a general allergic reaction or cold, either of which can cause red, itchy, watery eyes. StuRat (talk) 17:43, 9 March 2014 (UTC)
Thank you for your responses. They both adopt a commonsense approach but I must admit I was hoping for something more scientific. For instance, years ago, women taking the contraceptive pill experienced difficulties using contact lenses. It transpired that pregnant woman (which to their bodies, women taking the pill appear to be) produce a film over the eyes. This phenomenon was previously unknown. I wondered if there might be a more direct connection between the eyes and sinuses than normally supposed. — Preceding unsigned comment added by 78.127.60.178 (talk) 10:12, 11 March 2014 (UTC)
Hey, I asked a question here on the reference-desk yesterday regarding metals and railways and I got such good response that I was thinking I should ask another question related to metal. Something I have been thinking about for a while.
If one is thinking about taking up Blacksmithing, Goldsmithing or even Gem-cutting as a profession, what education would be needed?
Chemistry and metallurgy seem obvious, but what else, and where would be a natural place to start?
By the way, for any Wiki-modders out there who might read this, There doesn't seem to be an own reference page for questions related to 'Education'. If there is, then I must have missed it. Perhaps there should be? So science seemed the most natural place to ask this question.
Metallurgy is the general topic for metals, but that deals more with smelting, etc., whereas a blacksmith or goldsmith shapes existing metals, for the most part. Lapidary is the topic of dealing with gems. However, smithing and gem-cutting don't require advanced degrees, but rather you would look for an apprenticeship where you could learn from a master.
However, beware that much of this work is now either done in third-world nations paying minimal wages, or by machine. So, there are only a few jobs left in those fields that pay well. For example, you could own a jewelry shop that repairs wedding rings and such. (It would probably be cheaper for them to just buy a new ring, or send the current one overseas to repair, but the sentimental value prevents them from doing either of those.) StuRat (talk) 17:35, 9 March 2014 (UTC)
In the UK there are university courses in silver and gold smithing, but the normal route to black, white, tin, silver and gold smithing is via an apprenticeship. No formal qualifications may be needed, just an aptitude. --TammyMoet (talk) 19:23, 9 March 2014 (UTC)
Things that used to be industrial necessities are now done mainly as "artisan" crafts for fairly limited markets like decorations and people trying to do authentic restoration of historical objects. Modern steel plants and machine shops are about as far from blacksmithing as you can get. There are professional societies dedicated to keeping the old trades alive like the Artists Blacksmiths’ Association of North America and Society of North American Goldsmiths. Their websites will probably have links to educational options. Colleges with studio art programs will probably offer lapidary and basic metalworking classes. Some also offer glassblowing, probably fewer offer blacksmithing. Probably the only modern metallurgy class that will be particularly useful for a blacksmith would be a class on steel microstructures and phase transformations. The strength of steel is generally determined less by the alloying elements and more by the heat treatment. For working with gems, classes in geology would be more relevant - learning how to identify minerals, what causes color/shape. Mr.Z-man19:33, 9 March 2014 (UTC)
Blacksmithing is more of an informal trade. I remember in high school, the only future career listed that didn't require a high school diploma was blacksmith.--Aurictalk19:42, 9 March 2014 (UTC)
I know that these professions, at least blacksmithing, isn't the same as it used to be. In a way, I think it's a shame. But thanks for your answers. They were helpful.
Krikkert7 (talk) 22:31, 9 March 2014 (UTC)
See sources #26 and #27 in the MSG link in the title. One study showed it doesn't cause obesity in Chinese subjects, while another study shows that it does cause obesity in a similar group of Chinese subjects. So, if we assume both studies to be factually correct, does anybody know why there would be a difference in the conclusions ?
Also, has a study been done on the effect of MSG on Europeans or Americans ? My two thoughts are that they may react differently, due to genetic differences (with Orientals having been exposed to it longer and adapted better to it) or perhaps differences in diets. StuRat (talk) 18:16, 9 March 2014 (UTC)
What mechanism is offered? MSG is the salt of glutamic acid, certainly not a huge source or calrories, nor known to be medically active. Yes, it makes plain foods less plain. But so does salt and pepper. The two cuisines that use it most, Eastern and Italian (from Parmesan cheese and tomato sauce) do't seem particularly fat. I'd look instead at the influence of affluenza. μηδείς (talk) 21:07, 9 March 2014 (UTC)
Not sure about those studies, but previously I'd heard it stimulates the appetite, hence people being hungry again an hour after eating Chinese food. StuRat (talk) 21:16, 9 March 2014 (UTC)
Yes, you'll want to look at umami. But the notion is like saying that salt causes obesity. It simply makes less palatable foods more palatable, in this case signalling to the brain the presence (whether it exists or not) of proteins. μηδείς (talk) 21:53, 9 March 2014 (UTC)
At least for me, salt limits how much of an item I can eat. I get dry mouth and my lips start to crack. Drinking lots of water helps, but that fills me up a lot sooner. And knowing my blood pressure will spike as a result and I will feel veins throbbing in my head also makes me stop. StuRat (talk) 20:39, 11 March 2014 (UTC)
The study that did find a link looked at BMI vs MSG intake at a single point in time. The study that did not find a link looked at change in BMI over a 5 year period (as well as the baseline BMI). The study that did find a link surveyed 752 people from rural areas age 40-59. The other study looked at 1282 people ages 20+ from a mix of rural and urban areas, but only from one province. The second study also points out a potential issue with the first one: "A major criticism of the present study was that the total free glutamate (specified as glutamic acid) intake of the non-users compared with of the users of MSG was the same, possibly due to the fairly homogenous dietary patterns among the predominantly rural community, or it may have resulted from inaccuracy in the assessment of MSG intake."
In general, it seems like the main reason they choose China is convenience. Chinese people cook with MSG at home, so it's easier to measure how much they're actually eating. Westerners get most of their MSG in processed and restaurant foods. Mr.Z-man00:08, 10 March 2014 (UTC)
Acceleration of human evolution during Holocene
This paper claims that human evolution accelerated during the last 40,000 years. Unfortunately the paper is too technical for me. I was hoping someone could briefly summarize exactly how the researchers reach this conclusion ie how it is even possible to measure the rate of evolution. 65.92.5.74 (talk) 21:07, 9 March 2014 (UTC)
Well, if they can get DNA from fossils of various ages, they can determine how much of a change took place between each sample. StuRat (talk) 21:12, 9 March 2014 (UTC)
They measured the long-term rate of evolution by calculating the difference between human and chimpanzee DNA. They measured the rate of recent evolution by measuring the differences between the DNA of various modern human populations, assuming that all of them diverged from a relatively small unified African population around 40,000 years ago. I should note that the recent discovery of Neanderthal and Denisovan contributions to the DNA of some populations raises doubts about the validity of their analysis. (Their paper was published in 2007.) Looie496 (talk) 05:21, 10 March 2014 (UTC)
March 10
Early-diagnosis pancreatic cancer
After noting that early diagnosis is rare due to the lack of symptoms, the Pancreatic cancer article goes on to say that the 5-year survival rate for local disease is just 20%. The sourcing is solid, and . I'd previously assumed that the disease's low survival rate was due simply to the difficulty of catching it early, and that most people with an early-caught pancreatic cancer would survive, comparable to things like ovarian cancer (92.7% five-year survival when caught early, per the article) or melanoma ("the chance of cure is high" when caught early, per the article). Why is pancreatic cancer different? Nyttend (talk) 01:37, 10 March 2014 (UTC)
It looks like the catch is the "when caught early" part - that pancreatic cancer is seldom caught early. Much easier to catch melanoma early, one would think. ←Baseball Bugscarrots→ 02:45, 10 March 2014 (UTC)
But that's the thing: "local disease" definitely sounds like "caught early", but you still have a 4-in-5 chance of dying within five years if your pancreatic cancer is caught early. Ovarian is really hard to catch early ("It is disproportionately deadly because it lacks any clear early detection or screening test, meaning that most cases are not diagnosed until they have reached advanced stages"), but that doesn't keep it from having a high 5-year-survival rate when caught early. Nyttend (talk) 02:59, 10 March 2014 (UTC)
I don't think that's the meaning in the article, because separate statistics are given for "locally advanced", which has a 10-month average survival rate. Judging by cancer staging, the latter is stages 2-3, while the "local disease" is stage 1. Anything below stage 4 is "not spread to other organs yet", and presumably the death rate for stage 3 is substantially higher for pretty much any cancer than is the death rate for stage 1. Nyttend (talk) 03:10, 10 March 2014 (UTC)
It helps to keep in mind that cancer is not one disease. It's basically a symptom--unregulated cellular reproduction. There are some 200 human cell types, hence at least 200 different types of cancer. It's very similar to talking of broken bones. Broken fingers rarely kill, broken necks and spies and hips and skulls moreso. Well overa year and a hald ago I asked about lung cancer that had spread to the brain. Chances were someone with that stage inoperable lung cancer with two separate spots in the brain had well under a 6 month average survival rate--she's in remission today.
As for people with pancreatic cancer, my parents, in their seventies, know at least 6 who have been diagnosed, and only one now living, and on his last legs. None lived more than two years from diagnosis, which in almost every case was asymmetric back pain. Who gets back pain and thinks pancreatic cancer? The other symptom is type 2 diabetes, which many people expect from lifestyle and family history. Here's a good article from CNN on th topic that killed Patrick Swayze and Joan Crawford Steve Jobs and is the fourth most deadly form of cancer after lung, breast, and colon: See . μηδείς (talk) 03:55, 10 March 2014 (UTC)
Um, is this real? I see a lot of online ads for "simple trick solves , so the use of "trick" in the headline makes me suspicious that it's spam. It also doesn't really answer the question. Nyttend (talk) 13:05, 10 March 2014 (UTC)
Yes it's real, New Scientist is a well-respected (if populist) science journal in the UK, and I note their footnote that the print article was originally titled "Pancreatic cancer's weak spot found". --TammyMoet (talk) 13:28, 10 March 2014 (UTC)
It may have been respectable at one time, but it has terrible journalistic standards these days, at least in areas where I have some expertise (medicine isn't one). I'm sure this research is real, but the realistic possibility of its turning into a cure for pancreatic cancer is probably much lower than the reporter wants it to seem. -- BenRG (talk) 21:11, 10 March 2014 (UTC)
New Scientist has never been respectable - it has always been what Scientific American has degenerated into, and even in its salad days, SciAm was just a tony popular-audience magazine, not a scientific journal. That being said, what would impress me would be a published paper on "pancreatic cancer's weak spot" in a peer-reviewed medical journal (my publication list includes papers in several such journals). Science or Nature would do; the New England Journal of Medicine would not, as it panders to medical politics; it is NOT a serious medical journal. Of course, a peer-reviewed article in Cancer or any other specialist medical journal where the peer review is apt to be searching and informed by clinical experience would be best. loupgarous (talk) 23:01, 11 March 2014 (UTC)
Finding academic reviews of Murry Salby's published work
Hi, this climatologist has published dozens of peer-reviewed articles, and two textbooks. I'm hoping to find guidance on locating reviews of his work, as well as how to structure presenting the information. Doe sit make sense to list all his peer reviewed published work. How do we note which ones are most notable and should definitely be talked about? Etc. Any help appreciated. Sportfan5000 (talk) 11:16, 10 March 2014 (UTC)
"How to structure presenting of the information" -- do you mean you plan on improving/extending his WP article, or is this for some other project? There will be different best practices depending on where you are presenting your work. One way to get a feel for the notability of an academic paper is it's citation count (available via google scholar), and perhaps the impact factor of the journal where it was published. I would not recommend listing all his published work. Our article says he has published over 100 articles (which is about right for a productive scientist of his age), and I doubt they are listed in full anywhere, except perhaps on his own curriculum vitae. As for reviews of his work, that is tricky. If you just google his book names, you get tons of blog posts and user reviews, which are not WP:RS. I suspect that e.g. nature_(magazine) or science news or science_(magazine) may have published some reliable reviews of his books when came out, but you'd probably have to have good online access through a university to search their archives. As for the articles, those don't usually have "reviews" written about them by experts. That is done privately by the journal before the article is published. Once it is published, the reader trusts that the editorial board of the journal has verified that the work is basically correct, viable, and of interest to the community. Some articles have "responses" published by other authors in the same (or next) issue of the journal, which are usually critiques of methods or conclusions. Basically, do not trust normal web searches for this guy. He is pretty unique, in that he is an actual atmospheric scientist who denies human-caused climate change, and that colors everything that you will see on google. (As far as I can tell, he is still not a specialist on climate change per se, rather being focused on upper atmospheric wave propagation for most of his early career.)SemanticMantis (talk) 14:37, 10 March 2014 (UTC)
Thank you for your thoughtful reply. This is only to help improve the WP article, I have no interest in the entire subject area outside of the article.
Looking at impact factor, it seems tied more to the journal than to the articles it contains so it may make more sense to note which of Salby's articles have the highest citation count.
I have not seen a curriculum vitae for Salby, and it doesn't seem like he promotes himself or his work, but has been doing some speaking engagements linked to global warming more recently.
Mid-2000s his entire work lab was dismantled, with varying disputes why, but the net effect is likely all his work in process was disrupted, so I'm trying to focus on accurately portraying his work from early 1980s-2005/6. Sportfan5000 (talk) 22:49, 10 March 2014 (UTC)
He jumped between at least a few different universities at the level of Associate prof. or higher. I guarantee you he was promoting his work in his field to achieve that! As for impact factor, think of that as a way of assessing the general prestige of a journal. Consider a made-up example: if he has two articles, each with 50 citations, the one in "Nature" will be more notable than the one in "Journal of Atmos. Sci", since "Nature" has a higher impact factor. One of the reasons that it is hard to get into Nature is that it covers all areas of science, so any particular article is seen by the editorial board as not only the top of its field, but so important that even non-specialists should know about it. As for the CV, I suspect you might find an old one online if you search long enough. But, not all academics post them to the public (I don't). It might be a long shot, but you could try to just ask him for it. If you are polite and say you want to use it to improve his WP article, he might go for it. Note the CV itself will not be a WP:RS, but it can point you towards sources that are. I really think the best thing in this case would be to look for "response" articles or "book review" blurbs in the major science rags. Finding the existence of such things is usually free/open, check at WP:REX if you need help getting access to full text. SemanticMantis (talk) 15:23, 11 March 2014 (UTC)
Remembering things only in a sequence
I can only recall, say, the 6th digit of my phone number by going through the first five. It's the same with say, the letter before Q in the alphabet. Is there a name for this kind of memory to distinguish from others? --129.215.47.59 (talk) 13:22, 10 March 2014 (UTC)
Misplaced Pages lacks an article about the concept, but I find visual sequential memory to be a common term, defined as "the ability to remember a number of items, letters, numbers, or shapes in series". --Jayron3213:33, 10 March 2014 (UTC)
Sequence learning is about how we learn this way. Chunking (psychology) is used mostly with memory tasks -- how we group things together to remember them (in sequences, among other ways). The method of loci (an aspect of the art of memory) is an ancient technique for remembering things that involves a similar idea to chunking. I fear none of these will provide a great explanation for why you would be unable to remember things otherwise, though. --— Rhododendrites | 15:56, 10 March 2014 (UTC)
Our brains are wired for certain things. Learning a phone number could be important. Focusing on a specific digit does not seem so important. Of course, individual talents will vary, and practice and time can help. I can run through the calendar in my head and tell you how many days are in each month. But for many it may still be easier to use the old "30 days hath September" thing. ←Baseball Bugscarrots→ 17:13, 10 March 2014 (UTC)
Why do they even need that? Alternate long/short. Start again at Aug. Feb is not 30. I think that's fewer things to remember than 30 days hath september. Sagittarian Milky Way (talk) 23:57, 10 March 2014 (UTC)
What you've just described fits what's called the "knuckle method" of recalling the days in each month. But some folks remember poetry more readily than cold hard facts. ←Baseball Bugscarrots→ 00:51, 12 March 2014 (UTC)
I know spelling works that way for me. For example, if asked to name countries which start with a certain letter, I likely will do much better than if asked to name nations which end in a certain letter. StuRat (talk) 17:25, 10 March 2014 (UTC)
discoveries of nasa space station
respected auditor
i have heared that a space shuttle or spaceship have discovered strange voices from space but scientists have not discovered that from where the voices are coming so please tell me about what have scintists discovered from space
As i am eager to get my answer — Preceding unsigned comment added by 119.154.28.74 (talk) 14:57, 10 March 2014 (UTC)
Misplaced Pages's lengthy Scientific research on the International Space Station article lists many of the experiments done on the ISS; all very worthy, but not spectacular, academic science. Since the end of the Space Shuttle program in 2011 the only manned spaceflights have been Russian Soyuz flights to the ISS. If anything was going to discover strange space voices it would be SETI, which hasn't yet. -- Finlay McWalterჷTalk21:35, 10 March 2014 (UTC)
When you think about it, this is impossible. Soundwaves can't travel through the vacuum of space - so these can really only have been radio waves or other electromagnetic signals...but all of those things are more easily detected by earthly telescopes and radio-telescopes - or the Hubble and other unmanned satellites - than with any of the instruments on the ISS and various shuttle missions. So it's completely impossible for those missions to have picked up anything we're not already aware of. So, this didn't happen - and whoever told you that it did has either misunderstood or been mis-informed. SteveBaker (talk) 02:41, 11 March 2014 (UTC)
Well, if ET is watching us from a stealth spaceship in low Earth orbit passing closely by one of our own spaceships then I suppose it could happen that their signal is too weak to be picked up from the surface, or maybe they are only transmitting home in a direction away from Earth. I haven't heard such a theory but it might be something a conspiracy theorist could accuse authorities of hiding. PrimeHunter (talk) 03:00, 11 March 2014 (UTC)
You need to consider all of the forces, and I think they did. E.g., the first equation in the solution expresses that the torques/moments around the left end of the bar add to zero: Ra × 0 + (−20N) × 0.4m + Rb × 1.0m = 0. -- BenRG (talk) 21:32, 10 March 2014 (UTC)
What they're doing is treating the left part of the bar, from 0 to x, as an object, and computing the moments acting directly on it around an axis perpendicular to the page and located somewhere on the right edge of the sub-bar at x (the vertical position doesn't matter). The moments are the two vertical forces on the left and the bending moment M, which is the integrated effect of the horizontal (normal) forces across the interface with the other sub-bar. M represents the torque from the 8N force as transmitted through the other sub-bar, so also including the 8N torque directly would double-count it. By Newton's third law the bending moment acting on the other sub-bar is −M, which gives a simpler formula M = 8N · (1.0m − x). I'm not sure why they used the more complicated one. -- BenRG (talk) 22:38, 10 March 2014 (UTC)
So can this problem be solved without breaking down into sub bars? I.e. By just considering forces on both sides of the point, in 1 equation? So, also considering the reaction force at B in that equation? 194.66.246.216 (talk) 09:29, 11 March 2014 (UTC)
Is this equation correct? M=12X-20(X-0.4)-(8(1-x))? If not, how would you find the bending moments across the beam, taking into account all forces? — Preceding unsigned comment added by 194.66.246.216 (talk) 09:34, 11 March 2014 (UTC)
The right hand side of your equation simplifies to zero, so it's incorrect. Think of pulling a block by a rope over a level surface against friction at constant speed. You pull on the rope with a force of (say) 10N; the rope pulls on the block with a force of 10N. It would never be correct to add those and get 20N. If you consider the rope and block as a single object, the second 10N force would be ignored because it is an internal force. If you consider the rope and block as separate objects, the two 10N forces would both be included in the calculations, but not added because they act on different objects.
You need to split the bar to compute M because that's built into its definition. From the perspective of the bar as a whole, the bending moment is a neglected internal force. The internal forces can be neglected because they all add to zero, which is more or less why your equation simplifies to M=0. -- BenRG (talk) 19:14, 11 March 2014 (UTC)
March 11
Ftc #104 ( Group Q's 1-8 )
To what extent are there competing schools of thought within the field of Fire Prevention? (Education, Engineering, Enforcement)
To what extent do experts in the field of Fire Prevention disagree about the answers they give to important questions?
What other fields deal with Fire Prevention and activites (from a different standpoint, perhaps)?
To what extent are there conflicting views about Fire Preventi in light of these different standpoints? To what extent, if at all, is the field of Fire Prevention properly called a science?
To what extent can questions asked in the field of Fire Prevention be answered definitively? To what extent are questions in this field matters of (arguable) judgment?
To what extent is there public pressure on professionals in the field of Fire Prevention to compromise their professional practice in light of public prejudice or vested interest?
What does the history of Fire Prevention tell you about the status of knowledge in the field? How old is the field? How common is controversy over fundamental terms, theories, and orientation?
Many disciplines are not definitive in their pursuit of knowledge. What are the strengths and weaknesses in our field of Fire Prevention? — Preceding unsigned comment added by BrandenR411 (talk • contribs) 02:24, 11 March 2014 (UTC)
All engineers use maths a lot of the time. Engineers spend a lot of time writing things that don't require maths - often it is in order to persuade someone else, or a group of others, about something. The people who are the target audience are often not highly numerate or highly mathematical people. When engineers do use maths it is often fairly basic algebra or geometry. Occasionally it is trigonometry. Sometimes it is even basic calculus. Engineers are expected to be competent in high-level maths because many of the more complex ideas they need to be conversant in, use high-level maths as part of their explanation. Engineers are rarely criticized for a lack of skill in maths, but engineers are regularly criticized for a lack of skills in written English. Dolphin(t)12:02, 11 March 2014 (UTC)
But surely someone has to do the detailed design calculations. Are you saying that other than detailed design engineers, most engineers don't use maths? Clover345 (talk) 12:26, 11 March 2014 (UTC)
I agree that "someone has to do the detailed design calculations." But your question is not "Do all the detailed design calculations have to be done by a civil engineer?" Your question is "Do all civil engineers use maths in their everyday work?" Of course, many civil engineers do things other than detailed design calculations. Dolphin(t)22:46, 11 March 2014 (UTC)
Surely, Engineers need to know the higher level maths, but it isn't like they do all of those calculations by hand on paper with a slide rule. They need to know the maths so they understand what they are doing, but most calculations today are done by machines, like calculators and computers. It doesn't absolve engineers from knowing exactly what they are asking the computers to do and why they are asking them to do it, but engineers are not required to do things which technology could do for them. --Jayron3212:34, 11 March 2014 (UTC)
Yes they do. It's also very important that they get it right. Whether it's calculating the camber of a curved road or how thick a dam wall must be, there is always maths involved. Like Jayron32 said - you need not know every formula out of your head but you do need to understand where to plug the variables in. 196.214.78.114 (talk) 12:40, 11 March 2014 (UTC)
Another example of using high-level maths is preparing examples using pencil, paper, and general purpose computer software (calculator, spreadsheet, Mathcad, Mathematica, or the like to verify that newly-written or unfamiliar computer software is working correctly, and that the engineer understands what the software is doing. Jc3s5h (talk) 17:17, 11 March 2014 (UTC)
As mentioned by Dolphin, communication skills are also important, Failure due to miscommunication can happen (especially if there are design changes) as happened in Hyatt Regency walkway collapse. One should understand the mathematics well enough to be able to explain it plainly (and the related physics, as Feynman did). — To refocus on the specific question: while some civil engineers might not need to use maths "everyday" in the sense of actually doing calculations, they are likely to "use math" in the sense of reading and understanding it. ~:71.20.250.51 (talk) 23:13, 11 March 2014 (UTC)
Speaking as an uncivil engineer in every meaning of that phrase, I use maths every day. Mostly it is hidden inside clever scripts that I run in matlab, but then I get to write those scripts as well. Examples of maths I use very frequently : Fourier analysis, analysis of well formed experiments (Taguchi), analysis of poorly formed experiments (usual ones), 3 dimensional geometry, analysis of complex spring mass damper systems, and matrices up the wazoo. Mechanical engineers are generally less reliant on tables and codes than civil engineers, and hence more reliant on day to day maths, partly because we can afford to make prototypes and break them, and partly because the codes and tables do not cover the wide range of products we design. Having said that I haven't solved a partial differential in decades, and only once since leaving uni have I had to solve a double integral by hand. Of course with Mathcad and the like available on every desktop actually solving a calculus problem by hand is more of a rite of passage than a useful exercise. Greglocock (talk) 23:51, 11 March 2014 (UTC)
Detecting debris from flight MH 370 from satellite pictures
I find it rather strange that the plane hasn't been found yet, it seems to me that it shouldn't be very difficult to find the debris of the plane using detailed satellite pictures from before and after the (presumed) crash by processing that using the enormous computing power that is available today. Or am I missing something here? Would there always be a lot of data from the pictures that would fit the general characteristics of the debris that one is seeking that wouldn't have anything to do with the crash? Count Iblis (talk) 16:18, 11 March 2014 (UTC)
DigitalGlobe has made images available and are asking for a crowd or Human flesh search engine to help them analyse these and look for possible points of interest. I can't say for sure that they aren't primarily a PR stunt and the crowd sourcing doesn't help much, although the various reports such as do include quotes where it's implied it is difficult for their algorithms to differentiate wreckage from other stuff when using their data (i.e. including whatever limitations imposed by their satellite imaging capabilities).
China has also adjusted the operations of 10 of their satellites to assist in the search , although not surprising they haven't given any info I've seen on the the probability of their satellites finding something.
The US satellite capabilities would almost definitely be more than either of these and they must be using them to assist as well, but again, it's unlikely we would get that much info on the probabilities of their success.
It's worth remembering that even if the satellite imaging and processing power (remembering the ever increasing search area and the resolutions likely needed for success and this would need to be something they are able to spare in the midst of the ongoing Ukrainian crisis) is capable, you would need to have the existing algorithms available or be able to tweak whatever is available for that purpose in time.
There have already been false reports of plane debris, reported by human pilots flying over the sea. If humans can't easily tell the difference between plane debris and ordinary debris, a computer has no chance in hell. Remember that the Earth's surface is enormous compared to the size of an airplane, that garbage drifts into the ocean all the time, that airplanes and boats crisscross the surface constantly, and that most or all of the plane might be underwater (see Air France Flight 447, which took 2 years to find). ---Bowlhover (talk) 19:05, 11 March 2014 (UTC)
Regarding AF447, the searchers had retrieved definitive floating debris after only about 5 days. Yes, it took them 2 years to find where the fuselage had come to rest under more than 10,000 feet of water, but the floating debris was found after only a few days even though it was hundreds of miles from shore. Dragons flight (talk) 19:35, 11 March 2014 (UTC)
If the debris was in the water, it should be quite obvious, because much of it would float. It might be harder to find on land, as there's jungle in the area, and the plane could crash in the jungle with no obvious signs from above, as it would all be covered up by the jungle canopy. If nobody happened to be near the crash site, it could go hidden until somebody happens upon it.
The thing that seems odd to me is that they couldn't track it on radar to the crash site. Do they not have radar near where it disappeared ? Did it drop below the radar then fly many miles before crashing ? StuRat (talk) 20:31, 11 March 2014 (UTC)
Radar is little used in modern civilian aviation. It all works with transponders - instead of bouncing signals off the metal bodies of planes, air traffic control listens to active transmitters onboard aircraft. Radar degrades rapidly as function of distance, making it messy and unreliable, while transponders can transmit extra information such as speed, altitude, and identification. The transponder on MH370 stopped transmitting for an as yet unknown reason. A military radar happened to track the flight a bit longer, giving the latest best estimate of flight route. 88.112.50.121 (talk) 22:40, 11 March 2014 (UTC)
Indeed. Civilian (air traffic control) radar showed the aircraft dissappearing at a certain point. Military radar records showed that the plane turned at that point, descended to a low altitude, and continued flying another 500 km. So a catastrophic event didn't happen when it was lost to civilian radar. The transponder was turned off. Searching has been has been tailored to suit where it actually went (Malacca Straight), not just where it was when contact was lost (Gulf of Thailand). 121.215.154.87 (talk) 23:47, 11 March 2014 (UTC)
Organising colours
I have many reels of sewing thread I'd like to organise according to its colour. I have trays suited to this purpose enabling four rows and about 15 columns. What question should I ask myself about the colour of the thread to determine where it goes? I'm trying to use MS Paint's colour selector as a guide. I'm not sure whether that will help or hinder me. ----SeansPotato Business18:45, 11 March 2014 (UTC)
Each color in a computer graphics program such as MS Paint is distinguished by 3 values of the primaries Red, Green and Blue added together. It's not obvious how the implied 3-dimensional color space can help you plan a 2-dimensional (rows and columns) layout for coloured threads. Here is a possible arrangement where colors are in rainbow order vertically and decrease in saturation going from left to right. 84.209.89.214 (talk) 19:49, 11 March 2014 (UTC)
One problem with sorting real-world colors using RGB, is that this scheme is intended for computer displays, and can be counter-intuitive. For example: What do you get if you mix red and green? If you try (max red and green, no blue) what you get may surprize you. ~E:71.20.250.51 (talk) 20:30, 11 March 2014 (UTC)
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