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Reference Desk

October 6

What modern science explains work and the use of energy?

We used to call it 'Utilisation'--Light current 01:41, 6 October 2006 (UTC)

physics? --Robert Merkel 01:42, 6 October 2006 (UTC)

Modern physics?  freshofftheufoΓΛĿЌ  10:52, 6 October 2006 (UTC)

can it alter?

can genome alter gene expression without changing the dna sequence?

Sure. Gene expression can be changed by many factors, such as environmental reaction by regulators, splicing, gene silencing, XIST, RNAi... Whether the "genome" is in direct control is arguable, but oragnisms are able to use various methods to control expression without actually altering DNA.Tuckerekcut 11:55, 6 October 2006 (UTC)

See Methylation and Epigenetics.

Atlant 16:25, 9 October 2006 (UTC)

pH scale

why does the pH scale range from 0-14?

Actually, it does not. The pH value can be slightly below 0 or avove 14 in extreme cases. But to answer the question: In neutral water a small part of the H₂O molecules are split into positively charged H ions and negatively charged OH ions. In pure water there are as many H+ as OH- ions, as an H2O molecule splits into one of each. And it's only very few: Only one in 10 molecules (i.e., one 10,000,000th) splits. As the concentration of H+ ions is 10, we call this pH = 7. If you disolve a chemical which adds additional H+ ions without adding OH- atoms, the H+ concentration becomes much higher, and this is what makes the solution sour. Decreasing the pH by 10 means that you have 10 times more H+ ions, which make the stuff "10 times as sour". Also, the concentration of OH- (which gives rise to the charateristics of bases) goes down by a factor of 10. Due to the dissociation constant of water, the product of the concentrations of H+ and OH- stays the same, no matter what you have disolved in the water. For standard conditions, it is always approx. 10 moll. Hence, the pH value cannot go much below 0 , because then, there are more H+ ions than unsplit water molecules. Simon A. 07:48, 6 October 2006 (UTC)

Just to clarify and make a minor correction to an already excellent explanation, decreasing the pH by 1 (not 10) means that you have 10 times more H+ ions. —Brim 04:34, 14 October 2006 (UTC)

variegated plants

in variegated plants,every plant and every leaf has dissimilar variegation patterns.why is it so?

I think it's typically the result of two different color genes competing with each other. StuRat 11:43, 6 October 2006 (UTC)

are you going for the "cheat on my science homework" trifecta? Xcomradex 05:46, 6 October 2006 (UTC)

Calculate Radiation Dosage from X-Ray Machine

Hi, I've been searching the internet but i can't get the information i needed to calculate the Dosage Rate from an X-ray Machine. Examples such as If i am standing 15m away from the X-Ray machine for 15mins how much radiation dose i will recieved. Or if the X-Ray shielding is 15cm of Lead how much leakage radiation is present in the area...

Please help Thank You so much

Ivy61.194.96.93 06:06, 6 October 2006 (UTC)

I suspect it varies by machine, so you would need to look at info provided by the manufacturer (which is suspect, at best). A better method might be to use a Geiger counter to measure the radiation level yourself. StuRat 11:26, 6 October 2006 (UTC)

X-ray machines use beams, and that's where the main dose occurs. If you are a bystander then the dose rate diminishes as 1/distance-squared. So at several meters, you are probably at background levels (caused by everyday cosmic rays and radon from building materials). The scattered x-rays cannot penetrate lead shielding. If you work with x-rays, you carry a TLD badge, and have a maximum yearly dose. --Zeizmic 14:20, 6 October 2006 (UTC)

The answer is it depends on a lot of things. X-ray output, which is basically dose per time, is determined by setting the kvp (voltage) and mas (milliamp*seconds, or current). At a distance from the x-ray machine, the dose rate decreases by 1/distance-squared. Your exposure will depend of course if you are exposed by direct irradiation from the beam or if you only get scatter radiation. For patients getting x-rays, the doses received vary substantially from one type of study to another, from approximately 20 millirem for a chest X-ray to more than 600 mR for a pelvic X-ray. —Brim 04:47, 14 October 2006 (UTC)

Isaac Newton

How old did Isaac Newton think the earth was?

(spell check by  freshofftheufoΓΛĿЌ )

He probably didn't give it a lot of thought. He took the Bible quite literally (see Isaac Newton's religious views) and the idea of evolution was still a hundred years away. As far as most people of his day were concerned, the universe was in many respects quite static, so history on that scale was somewhat irrelevant.--Shantavira 12:19, 6 October 2006 (UTC)

Newton was very concerned with questions such as how the solar system was put into motion by God. And even by taking the Bible literally there are a wealth of different views one could take (see for example Newton and Leibniz's debates about the nature of God's laws, both which assume an intervening God but have very different interpretations of what intervention means in physical terms). I don't know the answer to this particular question. I used Google Books to search for "Newton" in Rudwick's recently published Bursting the Limits of Time, but nothing of note came up. Part of this may be because much of the scientific work on the age of the earth came from the field of geology, not physics or mechanics, and so wouldn't have necessarily interacted with Newton's own field of study. But that is a very speculative answer on my part; Newton had many, many scientific interests and I find it unlikely that he did not give this question some thought, though it did not come into full prominence until the end of the 18th century, as I understand it. --Fastfission 17:05, 6 October 2006 (UTC)

Help from a doc interpreting lab results (not advice)

I was in emerg last night and got a fairly thorough blood workup. The doctor said my kidneys, pancreas and liver were all great, and I'll be looking over the results with my GP when I can get in to see her next week. But I'm just curious about a couple (three actually) items that were outside the prescribed parameters.

1. My Amylase count is 26, with the norms according to the chart being 30-110 U/L.
2. My Basophil is 0.0, with a norm of 0.0-0.2 G/L.
3. My Urea is 2.5 with a norm of 2.5-8.0 mmol/L.

AFAICT, all the other results are very good; the ones that are better low are low, the ones that are better high are high.

Can anyone provide me with any analysis? Thanks in advance. Anchoress 10:25, 6 October 2006 (UTC)

There's nothing to analyze. There are no pathologies associated with low amylase or basophils that I know of. I'm not sure why they even have a lower value of normal. The urea may be low in very special diseases, which I suspect that you do not have (such as genetic diseases). Otherwise, there's nothing more to say. These are good results and should be ignored. InvictaHOG 10:36, 6 October 2006 (UTC)

Tee hee. Thanks for the response. May I ask another question? My sodium was 138, with a norm of 135-148 mmol/L, and I've always perceived my sodium intake to be on the high end. Are the two correlated, or not? Anchoress 10:47, 6 October 2006 (UTC)

I don't think it's as simple as "eat lots of sodium salt, and your blood sodium level goes up", no. People's bodies have varying abilities to remove sodium from the blood, meaning some can handle more salt than others. Also, consumption of potassium salts and calcium salts also interacts with sodium in the blood. StuRat 11:03, 6 October 2006 (UTC)

BTW to check my results I used this website, which seems pretty good. I don't know how accurate it is, but it's really easy to use. Anchoress 11:40, 6 October 2006 (UTC)

Your body's sodium concentration is tightly regulated. If you eat more salt, you will excrete more salt in your urine to keep the balance right. For basic information about this, see Sodium#Physiology and sodium ions. —Brim 04:51, 14 October 2006 (UTC)

preservation

i read in a site that there was a simple way to preserve fresh flowers along with their seeds ,for ever (the site claimed to do so ) .this is for a bio project that i was thinking of doing . but the only problem is that you had to pay to view the instructions . but i want to get them for free so could you explain how the project can be done . Or could u suggest any other topic .

thankMi2n15 11:47, 6 October 2006 (UTC)you

How about pressed flower craft and the links therefrom.--Shantavira 12:22, 6 October 2006 (UTC)

actually it sound rather kiddish for a ninth grader could u suggest something a bit more toughMi2n15 16:09, 6 October 2006 (UTC)

Flowers don't respond well to tough treatment. What was the website you are referring to? It seems rather odd that they should charge for this kind of information. It could be a scam. Nothing lasts forever by the way.--Shantavira 17:09, 6 October 2006 (UTC)

Here's a nice website. I'm sure it covers everything your scam website does. Your project could cover the different methodologies for different flowers and leaves. You can also freeze-dry flowers, but that takes expensive equipment. --Zeizmic 17:16, 6 October 2006 (UTC)

Pressed flower craft may sound childish, but as far as biologist friends have explained to me recently, it is still a standard technique used in biology -- only that they refer to it using the less childishly sounding term herbarium. A complete collection of pressed plants from a given region is of course most useful to study the kind of plants living there without having to leave the house, and actual pressed plants are more accurate that drawings or photographs. My friend told me that during her studies they were required to collect many types of grass and flowers, dry and press them and then neatly arrange them on paper labelled with correct taxonomy and other information. SO, you see, the challenge is not so much the quite simple procedure, but the selection and collecting of specimen, which should convey a scientific message. Simon A. 19:04, 6 October 2006 (UTC)

molarity

what happens to the molarity of 55.5M water if 58.8gms of nacl isadded to it?

The answer or the process with which to solve the problem should be found in your text book. Dismas| 13:46, 6 October 2006 (UTC)

The same question was asked twice on 4 October. Maybe it should go on the FAQ list :)  --Lambiam 16:00, 6 October 2006 (UTC)

55.5M of NaCl in water? is that possible?

To work it out you need the Volume (V) of water.

n(NaCl)₁=55.5*V N.B. V must be in dm

n(NaCl)₂=Mass/RMM

C=V/

Answer you're question? Englishnerd 18:33, 6 October 2006 (UTC)

Either the teacher who set this question is remarkably stupid, or it has been badly copied by a remarkable number of pupils. The question (translated) is: what is the molarity of a solution of 58.8g of sodium chloride in 55.5mol of water? The answer is only approximately 1M because the final volume of the solution is not known. The definition of molarity involves the volume of solution, and not of solvent. --G N Frykman 19:52, 6 October 2006 (UTC)

immune cell

why and how does the immune cell differentiate between self and non-self?is there any tissue in our body which is/can be non-self?if so,why?

please please help me with the above question.i tried to search for its answer butcould not get it. i have my exams starting in 2 days and i need the answer to this question. please help me out!!

See T cell and it's related articles. That should help you out. As well as going through your text books. Dismas| 13:52, 6 October 2006 (UTC)

It does not have to be tissue; it can be any foreign proteins. Have you heard of infectious diseases? What is the whole point of the immune system?  --Lambiam 20:20, 6 October 2006 (UTC)

Food is not "self", but isn't really "inside the body", in a biological sense, either. The same is true of embryos. Sperm and egg cells similarly only share some of the chromosomes of the parent. StuRat 18:27, 7 October 2006 (UTC)

Leo Szilard's Cancer Protocol

I would like to find out what kind of protocol Leo Szilard, one of the Manhattan Project's physicists, designed for himself when he was diagnosed with cancer. I'd also like to know what kind of cancer he suffered from. It is said that he designed his own protocol and was cured.

Thank you.Bregi 13:59, 6 October 2006 (UTC)

These sites (, ) indicate that Szilard had bladder cancer for which he rejected the standard therapy of the era and instead designed his own radiotherapy regimen. He received treatments in 1960 and 1962 and New York's Memorial Hospital, and his cancer was apparently in remission until his death (by a heart attack) in 1964.

I'm afraid I don't have information on the details of his therapy, nor the specific type of bladder cancer. TenOfAllTrades(talk) 16:01, 6 October 2006 (UTC)

Have you tried looking at some of the many biographies of Szilard? That's probably your best bet. --Fastfission 16:54, 6 October 2006 (UTC)

Triple Point of Water

"In physics, the triple point of a substance is the temperature and pressure at which three phases (gas, liquid, and solid) of that substance may coexist in thermodynamic equilibrium."

So can water exist simultaneously as a gas, liquid and a solid or is the triple point only that point at which water can go from one phase to the next with little/(no) effort? At the triple point can water actually be a gas, liquid and solid at the same time, thus truely coexisting? — Preceding unsigned comment added by Dan Small (talk • contribs)

• Yes, water can coexist simultaneously as a solid (ice), liquid, and gas (water vapor) at the temperature and pressure corresponding to water's triple point. See also the article on phase diagrams for more on this.
  I have never physically observed this phenomenon with water but it is relatively easy to observe carbon dioxide in all three states at its triple point using some dry ice. --Nebular110 15:24, 6 October 2006 (UTC)

Well, of course it's not the same water that's simultaneously in all three phases; I doubt that's what you meant, but just making sure. It's not just at the triple point that water exists in all three phases, either -- you can see that any time you see an icy road with puddles in it, and you know there's water vapor in the air above it. The way you know it's at the triple point is if you take the air away, and the vapor pressure from both the ice and the water is the same as the pressure of the ambient gas. Or something like that (it's a bit outside my field). --Trovatore 17:04, 6 October 2006 (UTC)

The important thing about the triple point is that all three phases will coexist indefinitely (or stably), regardless of their amounts. Without outside intervention, all the ice in the road will melt (or the water will freeze, depending on the temperature); while there will still be some water vapor, there will be a particular amount present and adding more would put the system out of equilbrium. (The new equilibrium might be significantly different; adding a lot of water vapor, even cold vapor, to an evacuated chamber with an ice cube in it might very well melt the ice.) At the triple point, the ice won't melt or sublimate, the water won't freeze or evaporate, and the vapor won't condense. (There may also be some sort of additional freedom in choosing the amount of water vapor or other gas present, but I have become confused as to whether the presence of other gasses changes the equilibrium between, say, water and water vapor. Anyone want to clarify that?) --Tardis 22:00, 6 October 2006 (UTC)

I have never actually seen a demo of a flask of boiling water with ice cubes floating in it, but that is the idea, right? Cool it to just above the (atmospheric pressure) freezing point, then connect a vacuum pump and pump it down to about 1/165 of an atmosphere. It should start boiling,(creating vapor phase) and freezing. If you keep the vacuum pump going, and it can exhaust the vapor fast enough, in the end much of it would have boiled away and ice would be left. Somewhere around 35000 meters above sea level should be a low enough air pressure to observe this, if I calculated right. Cool!Edison 03:32, 7 October 2006 (UTC)

And you won't "see a demo of a flask of boiling water with ice cubes floating in it" as a triple-point demo because such a world-in-a-flask wouldn't be stable. If the water were boiling, you would necessarily be away from the true triple-point. But yes, that's the basic idea: water ice (the solid) floating in water (the liquid) and above it all, steam (water vapor), all happily co-existing stably.

Atlant 16:34, 9 October 2006 (UTC)

ID this beach object

Here. Sorry this is only a blurry detail. The object in question is found on beaches in the eastern seaboard of the states. They are usually 4 inches long, and I believe they are some sort of eggsac. Any ideas? --Andrew c 17:54, 6 October 2006 (UTC)

Looks like the eggcase of a dogfish. (Google images for dogfish eggcase to check.)--Shantavira 18:17, 6 October 2006 (UTC)

That helped, its a ray or skate eggcase. Thanks! See Mermaid's purse.--Andrew c 18:28, 6 October 2006 (UTC)

Looks like a dogfish eggcase. Common all over the UK.

Word

Whats that word for people who think they have mental illnesses but they don't really? It is not hypochondriac, because that is considered "serious illness"; instead the word for mental illness. Thanksk, Iolakana•T 18:10, 6 October 2006 (UTC)

Is it mentally healthy to think you are mentally ill? If they didn't have a mental illness I would call them mentally healthy.--Shantavira 18:21, 6 October 2006 (UTC)

Stop this madness. 8-)

I believe Munchausen syndrome is what you're looking for ☢ Ҡi∊ff⌇↯ 03:44, 7 October 2006 (UTC)

Yes. That's it. Thanks, Iolakana•T 11:36, 7 October 2006 (UTC)

It might have been the word you wanted, but it has nothing to do with the defnition you offered. Munchausen syndrome is deliberately deceiving the doctor into diagnosing you with a disease you don't have, not convincing yourself that you have a disease you don't have. The latter is referred to as a delusion. alteripse 12:50, 7 October 2006 (UTC)

There may be some Munchausen syndrome patients who are also hypochondriacs, and are certain they are seriously ill, even though the doctors say they are fine. Then, in a bid to get the medical attention they think they need (to diagnose and treat their "disease"), they manufacture symptoms. StuRat 17:58, 7 October 2006 (UTC)

The question was in regards to mental illnesses only. If you were thought you had a mental disorder so fervently that you exhibited signs of it (Munchausen syndrome) and since mental disorders are, in effect, "all in your head" compared to other illnesses with external causes (viruses, bacteria, etc) you wouldn't be a hypochondriac and you wouldn't have Munchausen syndrome. You would be right. Ƶ§œš¹ 04:05, 8 October 2006 (UTC)

If it is a psychological illness when someone thinks to be ill although he or she is not, then if someone thinks to be mentaly ill the person is psycological ill! So if you think you are mentaly ill, you are. It seems somehow similar to the Liar paradox. 14 October 2006 (UTC)

ph

why is the pH of distilled water 6?

• Simple answer. It isn't. If the pH is low, you may have some Carbon dioxide in the water, which has formed carbonic acid.

It's true that distilled water has a pH which is a good deal below 7. I don't remember the value but I don't thin it is 6 -- maybe 6.7 or so. The reason, as already stated is that some carbon dioxide from the air will always dissolve and form carbonic acid. Simon A. 19:15, 6 October 2006 (UTC)

pH also varies with temperature. Boiling, pure, water has a pH significantly below 7.0 despite it still being neutral. --G N Frykman 19:44, 6 October 2006 (UTC)

PH SCALE

Misplaced Pages seems to be getting a lot of ph scale questions recently. Ok heres my question: if 14 on the PH scale of extreamly acidic then how come at school when we use universal indicator paper on something like sulphuric acid and it definately says that it is ph 14, when i stick my finger in it i dont fell a thing???--84.66.253.156 19:15, 6 October 2006 (UTC)

• Well, a couple points. First, the lower the pH value, the more acidic the substance is. Second, the stuff they have at your school is most likely diluted to some great degree (probably because students like to stick their fingers in it). While acids in real life are not at all like the horrific stuff they call acid in the movies, pure strong acids, like fuming sulfuric acid, are very unpleasant to be around, and would probably cause terrible burns quite quickly if they touched your skin. I've never tested it personally, but I've accidentally caught whiffs of the fumes and seen the stuff melt my gloves, and I can imagine what it would do. Maybe not a great answer, but it's all I can offer. – ClockworkSoul 19:33, 6 October 2006 (UTC)

• 14 is alkaline! Sulphuric acid definitely not have a pH of 14! see sulphuric acid. you should not be putting your hand in acid, but it would be dilute, and thus if you wash your hand in reasonable time, then no damage will occur. Englishnerd 19:30, 6 October 2006 (UTC)

sorry i ment ph 0--84.66.253.156 19:37, 6 October 2006 (UTC)

• The pH if the dilute acid I use in the lab is about 1, and the pure stuff is 0. You would feel something if you put your finger into pH 0 acid, but it still wouldn't be nearly as dramatic as what you would see in the movies (just like just about anything else you see in movies). – ClockworkSoul 19:45, 6 October 2006 (UTC)

The pH of 1.0M HCl is 0.0, and it's pretty dilute stuff still. To have a pH of 1.0 you are talking about 0.1M HCl, which is even more watery. The acid in the stomach is much more concentrated than this, for example, and you might think that the pH will just go down and down, but it doesn't - it reaches a minimum of about -0.5 for 5M HCl and then starts to rise again, purely due to the fact that there isn't enough water to ionise the HCl properly. Not that I would recommend it, but HCl of most concentrations won't hurt - unless you get it in a cut, and then you will hit the roof. The situation with sulphuric acid - a dehydrating agent when concentrated - and nitric acid - an oxidising agent - is completely different. Do not allow these acids to come into contact with your skin. --G N Frykman 20:07, 6 October 2006 (UTC)

Also, the indicator strips are only designed to be sensitive and reliable within a certain range of values. Beyond that range, you may get other colors or otherwise-invalid results because extreme pH conditions might damage the color indicator chemical. DMacks 20:49, 6 October 2006 (UTC)

This is depressing. Students really do this? Why am I surprised? My first dealing with HCl was forgetting that it was HCl, and thinking it was water. I dried something off with one of those brown-paper-bag type paper towels, and the acid went right through. Oww! I had blisters all over my fingers on both hands for a week or two. If you really want to see something cool, stick your finger in fluoroantimonic acid! By that I mean, make that the last thing you ever ever ever ever do. — X (SUPERDESK|Help me improve)01:34, 7 October 2006 (UTC)

There is still a great deal of confusion around. The fact that fluoroantimonic acid is a very strong acid does not mean that it is corrosive to humans. It just means that it provides a lot of protons. --G N Frykman 08:24, 7 October 2006 (UTC)

But are you ruling out its human-corrosive properties? Just because it is a very strong acid does not mean it wouldn't prove harmful? — X (SUPERDESK|Help me improve)

Absolutely not! But HF is a weak acid, but corrosive, and HCl is a strong acid, and less corrosive. You can't make generalisations. --G N Frykman 20:02, 7 October 2006 (UTC)

OIL

What is the chemical equation/formula/whatever im talkin about for oil. Like water is H20 and oygen os 02--84.66.253.156 19:31, 6 October 2006 (UTC)

What kind of oil ? (list) Hyenaste  19:35, 6 October 2006 (UTC)

Petroleum, if that's what you mean, is a mixture of hydrocarbons. That page should help you on your way. – ClockworkSoul 19:36, 6 October 2006 (UTC)

• OIl is a mixture of substances and thus doesn't have one single formula.see hydrocarbon for some of them! Englishnerd 19:41, 6 October 2006 (UTC)

Terms like "salt" or "acid" refer to a chemical property of chemical compounds. In contrast, "oil" in a general sense is used for chemically completely unrelated substances. What they have in common is not a chemical but a physical property: oils are liquids that don't mix well with water.  --Lambiam 19:50, 6 October 2006 (UTC)

Teleportation

Recently, stories of teleportation have made headlines. Apparently though, scientists are just teleporting the "quantum state" of atoms or photons. This isn't the same as teleporting matter, right? Delta 19:45, 6 October 2006 (UTC)

That is correct; quantum teleportation does not transport energy or matter, nor does it allow communication of information at superluminal speed. See our article Quantum teleportation.  --Lambiam 19:53, 6 October 2006 (UTC)

In science fiction the transporter gimmick would sometimes be described as scanning and destroying the original and sending the information to the remote end, where a duplicate was synthesized from matter already there. Thus information was transmitted, not matter. Other writers had the person turned into energy, the energy transmitted, and reassembled into matter at the other end. A 100 kg person would be a lot of energy to transmit: 9*10^18 Joules, or 2500 megatons of TNT. A large nuclear reactor would take many thousands of years to generate that much power. Of course there is no fundamental reason why the remote end could not create a copy of the original without destroying the original if the information transmission idea is used, if a sufficiently broad info channel were devised. It would just be a problem if they both showed up at the same place.Edison 03:16, 7 October 2006 (UTC)

I have an anatomical question about the Spinal discs.

Friday, 10-6-06; Portland, OR; 12:57pm West Coast Pacific Time

Original entry in: http://en.wikipedia.org/User_talk:Dematt#I_did_further_research_on_Spinal_Disc_Herniation

From: MyPresentCPUisTooSlow, new registered user since 9/06

I have an anatomical question about the Spinal discs: there is another anatomical part known as the "bursa". As I understand it, the bursa acts as a cushion, and its primary purpose is to reduce accumulating friction of repetitive joint movement. The structure of the bursa consists of a glycol-protein and synovial fluid for plyability; Is this structure the same for the Spinal discs? If not, then what does the disc's physical structure consist of?

--MyPresentCPUisTooSlow 20:38, 6 October 2006 (UTC)MyPresentCPUisTooSlow

A bursa is a sac, and there are two types in the body. One is the omental bursa, a (potential) space in the abdomen. The other type of bursa does indeed act as a cusion, primarily between bones and the ligaments that slide over those bones. These bursae are filled with synovial fluid just like many joints, and glycoproteins are most likely present in that fluid, as well as on the membranes of cells in the area. Bursitis is a disease associated with this second type of bursa. In my books and experience, there are no vertebral bursae in humans. However I was able to uncover some information here which suggests that dogs and horses do have bursae associated with their spinal columns. Spinal discs are not bursae, as they cusion the interface of bone and bone. These discs are composed of two main parts. The anulus fibrosis, the outer part, is made of concentric sheets of fibrous cartilage, and is mostly collagen. The inner part is called the nucleus pulposis, and is mostly (almost 90%) water. This inner part is more aptly described as cartilagous than fibrous. It's elasticity contributes to the flexibility and resilience of the discs. The cells in the vertebral discs are mostly chondrocytes.Tuckerekcut 22:15, 6 October 2006 (UTC)

Whistling effect?

What is the effect that produces the whistling sound when wind blows through flagpoles or a ship's wires?

It's the same as the sad, lonely sound of the wind whistling over empty beer bottles. --Zeizmic 21:46, 6 October 2006 (UTC)

No its not!. They're called Aeolian tones caused by aeroelastic effects. See Aeolian harp--Light current 22:11, 6 October 2006 (UTC)

See whistle. I don't know if there's a name for the effect, but a thin obstruction will cause a turbulent vortex just behind it, and at the right frequency the vibrating air makes a whistling sound.--Shantavira 08:20, 7 October 2006 (UTC)

If anybody konws anything, add it to wolf-whistling — X (SUPERDESK|Help me improve)09:14, 7 October 2006 (UTC)

Stepping-up voltage.

I know exactly how it's done with AC. What about DC? how do you step-up 12V DC to about a hundred volts or more AC or DC. i've seen a transformer device they sell in stores for plugging regular north american electronics (110-120V AC) into car lighter 12V outlets. im basically asking how this works? a detailed explanation or a link to some possible circuit digriams would be wonderful.

Try switched mode power supply or DC-DC converter first--Light current 23:34, 6 October 2006 (UTC)

For DC to AC, an inverter is used. -- AJR | Talk 23:43, 6 October 2006 (UTC)

Basically they electronically or mechanically switch the dc current on an off rapidly. This pulsating dc can be stepped up with a transformer to whatever voltage is needed, then changed to dc at that voltage via rectification. Wave shaping and smoothing are refinements. There are other tricks. In the late 19th century and 20th century, motor-generators were commonly used. You could run the motor on ac or dc and the generator coupled to it could produce dc or ac or 3 phase ac. A few utilities actually generated 1000 v DC, transmitted it a considerable distance to a substation, charged up a battery of many cells in series, and had a switch to disconnect the batteries from the 1000 volt line and discharge them at 120 volts dc at the remote substation, to back up the generators there.Edison 00:54, 7 October 2006 (UTC)

I have actually used that kind of motor-generators in the 21th century. :-) My university has a bunch of them in the cellar to create AC voltage of arbitrary frequency and amplitude. You go to the outlet panel, which may be on another floor, and tune in the parameters you want. Then one of those large motors (about the size of a small car) starts revving up and soon you get the signal that your voltage is ready. :-) When investing in new equipment, they go for more modern versions, though. But they sure are fun to see. (But the hall where they sit is an awfully noisy place to work in.) —Bromskloss 13:24, 7 October 2006 (UTC)

October 7

Raising a baby bird in isolation

Suppose if I were to raise a baby bird from the egg to adulthood in complete isolation, with me as the only other living creature he had contact with. How would his behaviour differ from that of the rest of his kind? Would he ever learn to fly? Would he copy my mannerisms? Would he know that he was a bird or would he assume that he was the same species as me?

It would think that you were its mother and follow you around. Some chap hand reared some ducks or geese or something, and when he drove in his car, they followed him by taking to to the air!--Light current 01:02, 7 October 2006 (UTC)

To get a Budgerigar (parakeet) which will talk, it is thought best to choose a young male and raise it away from others of its kind, so that it will bond with the humans. Parakeets raised with parakeets are thought less likely to do much talking. This is lore and not empirical science. But does the bird think it is a human, or that we are big parakeets, or that it will grow up to be human, or we will someday change to be birds, or is he a victim of the Stockholm syndrome? Who can say. His behavior would probably be different from a parakeet raised in a cage full of parakeets or in the wild. If you raised him from the egg (i.e. hatched with an incubator) you would need to feed him tasty little worms or whatever the birds diet normally is. Baby whooping cranes are kept from seeing their human caretakers, and fed with puppet-gloves resembling the adult birds. Some baby birds imprint on the first creature they see and will learn to follow a human around.Edison 01:05, 7 October 2006 (UTC)

Some of this surely depends on the specific species. It's a pity that birds typically don't react to offers like "a penny for your thoughts", so that we can only guess what the bird knows and assumes. So we don't know whether Konrad Lorenz's imprinted geese thought Lorenz was a big goose, or assumed they themselves were little Lorenzes.  --Lambiam 01:13, 7 October 2006 (UTC)

I doubt if non-human animals ever ask the question "What am I ?". That level of self-awareness would lead to religions and complex burial rituals, which we don't observe in any animals other than humans. StuRat 17:41, 7 October 2006 (UTC)

Elephants have complex burial rituals (and, according to this article, also rape and kill rhinos)

When an elephant dies, its family members engage in intense mourning and burial rituals, conducting weeklong vigils over the body, carefully covering it with earth and brush, revisiting the bones for years afterward, caressing the bones with their trunks, often taking turns rubbing their trunks along the teeth of a skull’s lower jaw, the way living elephants do in greeting.

--JianLi 22:32, 14 October 2006 (UTC)

taking control of Opportunity and ROver

If one had the cash, how would you go about stealing control of the two Mars rovers from Earth?

How much do you suppose the radio equipment would cost?

During the Apollo program, Popular Electronics started to publish a series of articles on how an electronics hobbyist could build a receiver to receive the transmissions from the Apollo astronauts on the moon directly, rather than listening to the TV coverage of the moon landing. They stopped after about the first article in the series, because they said they had calculated that it would cost far more than a house was worth. Now consider that Mars is around 400 times as far away, and you would need not only a receiver but a transmitter, and it gets really pricy, even allowing for advances in electronics since 1969. Microwave links from studio to transmitter have been hijacked (it once happened to WGN in Chicago) and communications satellites have been hijacked. The most likeley scenario would be a foreign power (such as the U.K. China or Russia) with its own deep space network, with all the programs used by the Rover and all the communication profiles obtained from someone in the program, and for some reason not worried about pissing the U.S off. Then perhaps they could tell the Rover to take a long walk on a short cliff or some such. It would be hard to do it and not be detected.Edison 02:44, 7 October 2006 (UTC)

You forgot the mention the most important thing: motivation. Why spend so much time and effort just to throw a rover down a crater? There's hardly any reason to hijack a Mars rover. ☢ Ҡi∊ff⌇↯ 03:11, 7 October 2006 (UTC)

id do it if i had the cash....

interesting!

Which is why you don't have the cash. People with cash tend to be better users of cash, and very frequently, use it to get more. — X (SUPERDESK|Help me improve)08:59, 7 October 2006 (UTC)

Really Mac Davis? How about the United States? They're rich, but they use the money to murder innocent people in Iraq. --Bowlhover 14:49, 8 October 2006 (UTC)

The people who are spending that money didn't earn it. —Tamfang 06:34, 11 October 2006 (UTC)

This reminds me of a story from the Vietnam war. I have been told that during the war, people at my university (in Sweden) intercepted the television transmissions from Vietnam to USA and so they were able to see all the material uncut. Quite cool, i think. —Bromskloss 13:33, 7 October 2006 (UTC)

Crash it? Why crash it? I fail to see the point. The question was about controlling it, obviously for the same reasons it was sent there in the first place, to explore. Of course, others could then pick up the results sent back, like those Swedes did. And people with money tend to use it to make more money for themselves, which could be endangered by others getting the info too. Which is why owners of money often don't do what is best for mankind (only for themselves) and are therefore not necessarily 'better users of cash'. Also, MacDavis assumes that people with cash earned by wise use of it, which is quite often not the case (most wealth is inherited). DirkvdM 08:25, 8 October 2006 (UTC)

can we all just agree that macdavis is a fool and call this question 'answered'?

The first bit, sure. :) The second bit, no. Neither question has been properly answered (just that it would be 'very expensive'). DirkvdM 08:27, 9 October 2006 (UTC)

Human eye resolution

What is the resolution of the human eye? 10000 X 10000.. or more than that?--Light current 01:56, 7 October 2006 (UTC)

According to Rod cell, the eye has about 100 million rods, so... yes! But the resolution within the fovea is better. Melchoir 02:18, 7 October 2006 (UTC)

Number of "pixels" is not the same as resolution. Let's agree that if you can just distinguish detail of 1 mm at a distance of 1 m, the resolution is 1/1000, so low means good. I saw some data that the diameter of cones in the fovea is about 2 micron, while the focal length of human eye is about 17 mm. That gives a limit of 1/8500, less if the cones are not tightly packed. Our article Eye, in the section "Acuity", presents some data that suggest 1/1380 (((8.7 mm)/12) / 1 m), but, taking a turn I can't follow, settles for 1/1075 (0.93 mm / 1 m). For practical use 1/1000 seems reasonable; in any case 1/10000 is not possible.  --Lambiam 02:22, 7 October 2006 (UTC)

This page cites (Ackerman, Eugene, Biophysical Science, Prentice-Hall, 1962) as reporting that the data show that the resolution limit for "most people" is 1/2000, while the most acute vision under optimum circumstances is 1/5000.  --Lambiam 02:55, 7 October 2006 (UTC)

Fovea?--Light current 02:56, 7 October 2006 (UTC)

The light has to pass through the cornea, an imperfect optical device which does most of the diopters of convergance, then through the aqueous humor, then through the lens, which adjusts focus and is an imperfect optical device, then through the vitreous humor, which may have crud floating in it, then hit the cones to activate the detection. Resolution is lost at each step. A hawk or eagle has 5 to 10 times better acuity than a human. The high resolution is only in the very central part of vision, but we're usually not aware of it because a visual scene is analyzed in a series of fixations with quick saccadic jumps between them. We can achieve as good as 20/10 vision with corrective lenses,better than the "normal" 20/20, resolving a detail of about 1 minute of visual arc.Edison 03:00, 7 October 2006 (UTC)

Also, see http://www.clarkvision.com/imagedetail/eye-resolution.html (it has some interesting info). The typical human eye can distinguish between a pair of lines 0.6 arc-minutes apart. 0.6 arc-minutes is about the size of an object 1.7 mm large, seen from 10 metres away. --Bowlhover 03:05, 7 October 2006 (UTC)

Which corresponds to 1/5730 radians. That corresponds to being able to discern the individual pixels on a 1000-pixel high screen from a distance of 5.7 times the screen height. Apparently neither of my eyes is typical, because there is no way I can do that.  --Lambiam 06:14, 7 October 2006 (UTC)

Not really. The webpage I gave was trying to say that: if you draw two parallel lines, each 1000 pixels long, on your television screen, and you separate the two lines by 1 pixel, than you can distinguish between the two lines at a distance of 5.7 times the screen height. Seeing the individual pixels requires significantly more resolution, since you need to see more than 1 dot per pixel to say that the pixel is not an infinitely-small dot. --Bowlhover 04:28, 8 October 2006 (UTC)

I don't believe it has the same resolution once your brain has processed the image. StuRat 17:07, 7 October 2006 (UTC)

How do you mean?--Light current 18:01, 7 October 2006 (UTC)

No doubt there are many aberrations coming from the rods and cones, and your brain needs to average them out so you don't see "random pixels". Thus, it might take signals from 100 rods/cones and produce a single output signal. StuRat 21:52, 8 October 2006 (UTC)

So what the resolution of your brain then? 8-)--Light current 22:47, 8 October 2006 (UTC)

I can't tell, since mine is out of focus. StuRat 03:30, 9 October 2006 (UTC)

I thought so. 8-)--Light current 03:35, 9 October 2006 (UTC)

A confounding factor to all of this is that your eyes' resolution varies depending upon which part of the retina is doing the imaging, but your brain hides a lot of this from you as your eyes slew around, taking in various parts of the overall scene. That is to say, wherever you look, you're seeing with the high-resolution part of your retina.

At one point, when computer power used to be limited, people were actually discussingtaking advantage of this effect for flight simulators. The idea was that the computers that synthesized the images the "pilots" were seeing were rather limited in how much high-resolution imagery they produced, so the engineers were going to couple the computers with eye trackers that watched where the pilot-under-test was looking. Only at the pilot's point of regard would a high-resolution image be generated; the rest of the scenery would be generated using a quick-and-dirty, much lower resolution method. I don't know if this was ever actually implemented; nowadays, computers can crank out acres of high-res imagery without the use of such whiz-bangs.

Atlant 16:47, 9 October 2006 (UTC)

Eating Disorders

Do people in third world countries suffer from eating disorders such as anorexia ?--Jobame80054 04:19, 7 October 2006 (UTC) .... I have been asking this question, of healthcare professionals, nutritionist & epidemiologist, for five years. Nobody could answer this question (they didn't have a clue)nor could they refer me to journal/research articles that addressed this subject.

It may not directly answer your question, but Anorexia nervosa certainly has a section on 'social and environmental factors'. Did you look there before you asked? --ColinFine 08:25, 7 October 2006 (UTC)

I think in countries where you are not sure you have enough food to live, you would never contract this psychological disorder. No body could ever answer the question before they never checked? The demigod of Google Scholar can help too.. — X (SUPERDESK|Help me improve)09:04, 7 October 2006 (UTC)

I would probably say that the answer is no. Anorexia nervosa is a psychiatric illness, meaning it is regarded as a health problem; not what someone has when they are completely starved. Iolakana•T 11:35, 7 October 2006 (UTC)

I don't think you understood the question. Yes, someone could develop anorexia during times when food is plentiful. However, the condition would likely go undiagnosed in such a place, as being underweight is widespread due to many causes there and many diseases also cause a lack of appetite. StuRat 17:01, 7 October 2006 (UTC)

Being underweight is not widespread in third world countries. True, the worst famines hit them harder, but if I may make a wild guess, I'd say that some 99% of people in third world countries get enough to eat to prevent them from getting as skinny as anorexics. Stop watching too much CNN and go out there and see what the world is really like. :) DirkvdM 08:47, 8 October 2006 (UTC)

You're dead wrong; it's about 34% of children according to this site: . StuRat 21:38, 8 October 2006 (UTC)

Hmmm, I wonder what causes the huge discrepancy between that figure and my personal experience. First of all, it's about preschool children, although I don't know why they should be affected so much more. Also, there is the question of what one calls 'underweight' or 'falling behind the accepted weight standards'. I've been to many third world countries (including 11 in Africa, the worst hit continent in most respects) and I haven't seen many people that looked anorexic (which is what the question was about). Many may have been ill fed by western standards, but that is not the same. DirkvdM 08:38, 9 October 2006 (UTC)

Actually, being so skinny is probably more common in the US (and other western countries to a lesser extent), where there are many women who think that being skin and bones makes them look pretty. Hmmm, did I just answer the original question? DirkvdM 08:50, 8 October 2006 (UTC)

Someone once told me that many historians think that certain medieval saints show symptoms of anorexia nervosa. They had psychological symptoms in common: for one, the saints believed they were getting "closer to God" by starving themselves, and similarly, some contemporary anorexics have a belief that by not eating they become "pure". This would seem to suggest that it's not only the skinny models in Western fashion magazines that make people anorexic, so it probably does occur in the third world, sometimes. --Grace 05:33, 9 October 2006 (UTC)

james harry keighly McCollum

James McCollum was a Canadian engineer, born, I believe, in Toronto. He is famous for his invention of the sleeve-valve in the early 1900s. This device was used in automobile and aircraft engines. The sleeve-valve was concurrently invented by Scottish engineer, Peter Burt and by agreement, applications of the device were known as Burt-McCollum sleeve-valves.

Strangely, I cannot find a single biographical detail on James McCollum - not even birth/death dates. Any help would be much appreciated.

Jerry Wells, Trentham, Australia.58.84.88.186

Looks like we're found wanting here! Ah but sleeve valve is here where it says :

The sleeve valve principle, was invented in 1903 by an American, Charles Yale Knight. --Light current 07:11, 7 October 2006 (UTC)

Where did you get the info you already have on him ? That would probably be the best place to start your research. Do they list their sources ? Perhaps he goes by a slightly different name. StuRat 16:53, 7 October 2006 (UTC)

LIke Charles Yale Knight for instance? 8-)--Light current 16:58, 7 October 2006 (UTC)

  McCollum filed quite a number of PATENTS in his time; that's where I got his full name from. Jerry W.9 Oct.

human proteins

someone had asked a question on 5th october about human proteins being synthesised in plant cells.... can u explain it to me with an example?

Usually you want to produce human proteins for use as therapeutic drugs: insulin, growth hormone, etc. This is done by introducing the DNA encoding the gene for the protein into a cell, and letting the cell produce proteins from the DNA by its usual mechanism. Human proteins have been produced in bacteria, in mammalian cell cluture, in plant cell culture, and in transgenic plants. Each technique has advantages and disadvantages. - Nunh-huh 11:51, 7 October 2006 (UTC)

Here is an article that you may find helpful: Genetically modified organism

Gary 17:36, 7 October 2006 (UTC)

Acid to dissolve hard rock/stones

Hello,

I wish to know, if there are any acids(or mix of acids )available, which can dissolve or decimate a part of rock or a part of any hard stone within a short time, may be some hours ? Appreciate some informatation and help !

Regards Anton

What kind of rock? I'm sure throwing some fluoroantimonic acid, hydrofluoric acid, or hydrochloric acid would fix your problem. No, not at me, at the rock!!! — X (SUPERDESK|Help me improve)10:14, 7 October 2006 (UTC)

Whether it could dissolve rock would depend on the composition. Acid could easily dissolve limestone, no so easily dissolve basalt. As far as decimating a rock, why would you want to reduce it by a tenth? Just stop what dissolution process when it is only 10% along. alteripse 12:46, 7 October 2006 (UTC)

While the original meaning of decimate was to reduce by 1/10th, the modern meaning is to wipe out completely. StuRat 16:45, 7 October 2006 (UTC)

Ah but its not correct is it? Its Word meaning creep! (Not you). To wipe out completely is still to annihilate. Or maybe youre thinking of macerate? Catachresis--Light current 16:55, 7 October 2006 (UTC)

Ah! Another romantic who believes that because a word means one thing it cannot mean something else, and because one word means something another word can't do so. Too bad. --ColinFine 20:03, 7 October 2006 (UTC)

Agree with first part, disagree with second. The reason I agree that because a word means one thing it cannot mean something else is simply avoidance of confusion and clarity of meaning rather than obfuscation. Cleary we need to differentiate between:

• Reduce to one tenth and
• reduce by one tenth

for instance. 8-|--Light current 22:58, 8 October 2006 (UTC)

"I refuse to tithe to the church, because it would decimate my finances (and because the priest can damn well pay for his hookers with his own money)." StuRat 03:27, 9 October 2006 (UTC)

I do believe that the above sentence is grammatically correct and self consistent. 8-))--Light current 03:31, 9 October 2006 (UTC)

Holding it

What factors go into how long you can hold one's urine? If you reach your urinary bladder's capacity, does it just come out? — X (SUPERDESK|Help me improve)10:14, 7 October 2006 (UTC)

The bladder has three ways out, the urethra, and the two ureters. The urethra has a sphincter to keep urine in when you want it in, but the ureters do not. If you are able to hold in your urine for so long that your bladder fills completely, which would be painful and very uncomfortable in itself, the first pathological event to occur would be reflux of the urine into the ureters and eventually into the kidneys. This reflux would alter the delicate concentration gradients in the kidney and would damage (eventually permanently) the organ's ability to filter blood. This may also cause infection of the kidney if bacteria was present in the proximal urethra or bladder. Reflux from an overfull bladder occurs most often in children with psychological pathologies that prevevent them from voluntarily voiding their urine. Since the bladder is relatively thick and muscular, it usually will not fail just from being overfilled. However, even in a relatively mild trauma, such as a low speed automobile crash, a full bladder can rupture, leading to a surgical emergency: another reason to "go" before you go.Tuckerekcut 14:35, 7 October 2006 (UTC)

I've had the urine back up into my kidneys. The way I can tell is that, after urinating, just a few minutes later I have to urinate again. That second time was urine which had backed up into the kidneys and then drained back down to the bladder. My advice, don't drink a Big Gulp during a long car trip ! StuRat 16:31, 7 October 2006 (UTC)

This was easily the most painful answer I've ever seen on the reference desk. Just reading it made my kidneys hurt :S Oskar 18:35, 7 October 2006 (UTC)

Yeah but did it make your eyes (or anything else) water? 8-)--Light current 22:53, 8 October 2006 (UTC)

Sphincter? Do you mean prostate in men. What is sphincter in woman? Do they not have more trouble holding it?--Light current 16:41, 7 October 2006 (UTC)

He means sphincter: specifically, the urethral sphincter. (A sphincter is any circular muscle (or group of muscles) that contracts to regulate the flow of material through an opening). TenOfAllTrades(talk) 18:14, 7 October 2006 (UTC)

Yes.. I did actually looked it up after posting that, and found the page you quote. Couldnt resist a quick few edits while I was there! 8-)--Light current 22:52, 8 October 2006 (UTC)

To add to the above answer, the bladder also ruptures in utero when boys have outflow tract obtructions as in posterior urethral valves. Because urine continues to be produced but cannot escape, the bladder ruptures and the urine fills the body cavities. InvictaHOG 20:24, 7 October 2006 (UTC)

"... how long you can hold one's urine"? Whose urine do you wish to hold? (yuk) DirkvdM 08:56, 8 October 2006 (UTC)

I was about to say that when I reread what I had written. — X (SUPERDESK|Help me improve)

Its sterile! (when fresh) 8-)--Light current 22:51, 8 October 2006 (UTC)

Such a long discussion, and nobody has mentioned yet Tycho Brahe and his unusual and painful death. Simon A. 21:20, 12 October 2006 (UTC)

I have a friend who held it for at least 24 hours (or he claimed to do so). Why didn't he need surgery for a ruptured bladder(why didn't his bladder rupture in the first place?)? Does he have an oversized bladder? Ilikefood 21:31, 12 October 2006 (UTC)

Bruhathkayosaurus vs. Amphicoelias

Someone asked a question about the largest dinosaurs. I looked it up on Misplaced Pages, and the Bruhathkayosaurus article gave a ridicoulously over exaggarated estimate of 220 tons for weight. The same went for Amphicoelias, which was given 170 tons. According to some sites, the theoretical limit for the weight of a land animal is 140 tons. If this is true, than the above estimates couldn't be possible. Which would be larger?

Bruhathkayosaurus cites http://www.gavinrymill.com/dinosaurs/largest-dinosaur-ever.html, which says "Based on the estimated mass Bruhathkayosaurus may have weighed 175-220 tons" and http://www.miketaylor.org.uk/dino/faq/s-size/records/ which says of 8. Bruhathkayaosaurus matleyi "44.1 meters, 175-220 tons". The real truth is, as http://www.miketaylor.org.uk/dino/faq/s-size/diff/index.html notes, the process for arriving at these numbers isn't very reliable. -- Finlay McWalter | Talk 11:25, 7 October 2006 (UTC)

Finlay McWalter is more or less correct. However, both Bruahthkayosaurus and Amphicoelias are known for very little evidence. It's easily possible that the above estimates are incorrect. According to http://dml.cmnh.org/2004Sep/msg00086.html, the weight of Bruhathkayosaurus has been reduced considerably from 175-220 tons to 157 tons. While still pretty heavy, 157 tons might be light enough for a land animal to support. As for Amphicoelias, it was probably lighter, at about 120-130 tons at the maximum. To summarise, Amphicoelias was probably much longer, and Bruhathkayosaurus much heavier. Hope this helps. -- Roger Davidson

Hard question on evolution

If all the non-plant creatures that can move around are automagically erased (by say a very powerful ET being). Can a pine tree (eventually) evolve into a kangaroo?

It could happen eventually, but since the two are very different it would take a very long time and there's no guarantee that it would happen. - Dammit 11:00, 7 October 2006 (UTC)

• I don't think it would be possible, although they are both Eukaryote, one is an Animalia, the other a Plantae. And because Kangaroos already exsise, the rtee wouldn't evolve in to it, the teory says that it would evolve into something new, but I'm almost certain it would only ever be another Plantae Englishnerd 12:05, 7 October 2006 (UTC)

In theory, the kangaroo niche being up for grabs, convergent evolution might result in a species descending from pine trees taking up that niche. They should be a bit careful hopping around or the pine cones will come off too early. To be more precise, the whole ecosystem will be gone thanks to our ET friend, so actually there is no niche left. But a similar ecosystem could return. On a shorter term, many plant species (for example Whitebark Pine) crucially depend on (motile) animals for reproduction, and these animal-dependent species would die out long before any significant effects of natural evolution could kick in, and so would other plants depending on such moribund species. On the time scale we need, continental drift is important, and Australia might not remain a recognizable entity (see Austro-Eurafrasia).  --Lambiam 12:54, 7 October 2006 (UTC)

It is quite likely that the idea of an animal, i.e. a living being that can move around, is picked up again by evolution. However, just look how many different kinds of locomation there are: Vertebrates walking on four legs, walking on two legs, flying with two wings, swimming with various fins, snakes, then even more invertebrates, with many more legs, things which move completely differently such as starfish, even stranger stuff in the depths of the ocean etc etc. So, evolution would certainly produce moving beings again, and these would fill out all the elements and perfectionate locomotion in water, on the ground, in the air, on hard and soft ground, in soft earth, and so on. But these animals, being capable of the same feats of locomotion as today's animals, might do so by completely different means. After all, we see that there are many different ways to move, and hopping on two legs, using a muscular tail as additional leg (kangoroo) is only one of many possibilities. On the other hand, there are tasks for which there are only a few sensible devices capable of it, most importantly seeing: There seem to be only few possible designs of eyes, as witnessed by the fact that evolution reinvented them several times independently, and hence, would probably come up with them again. Simon A. 15:43, 7 October 2006 (UTC)

Note that plants are capable of movement, just at a very slow rate, like flowers which track the sun. There are also some rapid movements, like exploding seed pods. StuRat 16:21, 7 October 2006 (UTC)

Other examples of moving plants include Venus fly traps and bladderworts. None are as motile as kangaroos, though. Many plants have sperm that can swim, but that's about all I can think of offhand.

You really have to ask yourself how much like a kangaroo the descendant of a pine tree would have to be to be called a kangaroo. As a biologist, I would certainly classify the two as separate, even if the plant-descended one looked exactly like the original. See convergent evolution for more information of that concept. The pine tree-kangaroo would not be able to interbreed with the original kangaroo, if your alien were to bring them back.

It would probably be more likely for some other organism to take up the kangaroo niche, probably a descendant not of plants, but of some sort of microorganism. From the rules given in the first post, that is, nothing that can move gets to live, the phylum Apicomplexa might survive and spread out, perhaps eventually including organisms that can move and later end up evolving into a wide variety of organisms. Bacteria might also evolve into some kangaroo-like thing after many millions of years. Evolution isn't goal directed, it never had kangaroos as a goal in the first place, but it could certainly produce something similar to kangaroos again, if populations of organisms were exposed to the right circumstances. Gary 17:55, 7 October 2006 (UTC)

Jack Cohen has long distinguished between what he calls 'universals' and 'parochials' in Evolution (see Evolving the Alien for example). 'Universals' are structures or processes that have evolved more than once independently (for example wood, articulated limbs, flight, eyes, and intelligence), while 'parochials' are not known to have arisen more than once - knees, vertebrae, DNA. His suggestion is that in exobiological evolution one would expect to see universals arising again (though generally by different mechanisms) but not parochials.

So from this argument, one might well expect a large fast-moving herbivore to evolve, but it would be surprising if it moved by bounding, or if it was marsupial. --ColinFine 20:18, 7 October 2006 (UTC)

Note that if all non-plant life forms were erased, plant life forms would probably die fairly soon as well. The circle-of-life needs microorganisms to recycle the nutrients from dead plants back into the soil. And if these microorganisms are left around, I'll bet they would evolve locomotion before plants would. johnpseudo 01:38, 8 October 2006 (UTC)

Colin: Interesting stuff you point out by refering to this book on xenobilogy. Might be a good read. Gary: Seeds that swim with theit own propulsion: that sounds intriguing. Do you have an example at hand? You write it's common. Simon A. 10:02, 8 October 2006 (UTC)

A plant can't evolve into a mammal. Or could it in principle, given enough time, if we assume that the Sun and the Universe will never die and all other such ceteras remain paribus? DirkvdM 10:44, 8 October 2006 (UTC)

Sure a plant can evolve into an animal (and, given enough time, a mammal). After all, single-celled animals are believed to have evolved from single-celled plants. StuRat 21:29, 8 October 2006 (UTC)

I am not talking about seeds, such as the seeds that fall from a tree or other plant, I speak of the sperm which plants use in sexual reproduction. Some types of plants have flagellated sperm, including the Ginkgo and cycads. Others have ciliated sperm. Motile sperm seems to be a primitive characteristic in plants, left over from their aquatic beginnings. Gary 23:05, 8 October 2006 (UTC)

Are there obstacles to industrial-scale production of cultured animal tissues for food?

Some vegetarians avoid animal products in their diet on religious or philosophical grounds. It seems that at least to some of them their concerns or objections can be addressed by growing animal tissues in a lab environment (as opposed to getting the same tissues by raising and slaughtering animals). I wonder if industrial-scale culturing of animal tissues for food would become a reality in the next several decades. Can someone picture how this may happen, or are there difficult obstacles to making the idea work? --71.244.110.187 12:21, 7 October 2006 (UTC)

One of the big problems with tissue engineering is infection control; without all the multilayered immunological defense systems you get in a cow, a lump of cow muscle growing in a tank is susceptible to all kinds of infection. Maintaining sterility and controlling infection is expensive - that's worthwhile when you're growing someone a new organ (where they'll happily pay tens of thousands of dollars per pound), but it's going to make the cost of any meat you produce outlandishly expensive. You've also got consumer acceptance issues and a pretty small market - lots of vegitarians don't want to eat meat, lots of others want to eat healthy natural food (not some weird lump of tissue that's been floating in a tank of antibiotics in some factory somewhere), vegitarian meat substitutes are pretty good (or at least good enough for vegitarians to not pine for meat very much). I don't think you'll find that the religious objections to a given meat are going to go away with tissue engineered vatmeat - muslims and jews are as unkeen on anything made from pig as they are on pork, ham, and bacon, so your BeakerBacon isn't going to sell there. As to efficiency, with modern breeds and rearing methods, it'll be very hard to beat a cow as a means of producing meat. -- Finlay McWalter | Talk 12:36, 7 October 2006 (UTC)

I don't know what to make of this website, I can't really tell if it's more about science or art, but it seems relevant to your question (and appears to be affiliated with an educational establishment of some sort).Tuckerekcut 14:20, 7 October 2006 (UTC)

You made some good points. The issues that you raised point to an (admittedly freakish) idea: an artificial organism (or perhaps more accurately, assemblage of organs) optimized for meat production and nothing else. Such an organism, if one can call it that, would have no high-level neurological functions — only enough apparatuses to grow meat, sustain itself, and defend against microorganisms. That would bring "franken-food" to a whole new level of freakishness. --71.244.110.187 17:00, 7 October 2006 (UTC)

Setting aside how like what you describe a modern cow breed already is, you're quite right (but probably, really, hopefully, wrong). Margaret Atwood's novel Oryx and Crake (which I can't recommend highly enough - it's grimly hysterical) describes one such "animal", a genetically engineered chicken thing branded "chickie-nobs" which is mostly breast meat and a basic GI tract, with the minimum of brain, bone, beak, and other extraneous parts. This is certainly possible, and it's so much easier to do than tissue grown in abstract - but even then I've difficulty seeing the market for it. For poor people, who just need protein, grain and legume sources (e.g. soy) are always going to be much cheaper (and, if you're pushed, it's easier to genetically engineer a more productive soy plant than a more muscular cow). For richer people we've seen an ever increasing concentration on food quality, and an increasing concern about where food comes from and how it's made. This is reflected in a great increase in the sales of organic food, free-range chicken, barn eggs, and enhanced restrictions (at least in Europe, I don't know about other places) on the conditions for animal transportation, slaughter, and veal production. Such people want happy, healthy food, and aren't going to put GMO-sarcomal in the same basket as their organic eggs and free range chicken. I really can't think there's much of a middle market, people who want meat, can't afford real animal, and are willing to accept the flesh of some eyeless monstrosity. Even the fast food chains, masters off passing of mystery meat as wholesome goodness, are going to have problems marketing the tissues of such horrors, even to the most foolish of teenager. We will see ongoing enhancements of our food crops (plant and animal), but it'll be incremental and subtle, the way it has been for centuries - our current plant and animal foodstocks are so divorced (by generations of selective breeding) from their native cousins that the natives seem barely edible to us. -- Finlay McWalter | Talk 17:45, 7 October 2006 (UTC)

Margaret Atwood would appear to have taken that idea, at least, from 'Chicken Little' in The Space Merchants. --ColinFine 20:22, 7 October 2006 (UTC)

I would say, that in the long term, such engineered meat (and milk and eggs) could replace normal animal food. There is the potential for such food to be healthier and more efficiently use resources (since it doesn't have to do all the other things animals must do to survive, like move). However, this will likely take decades to perfect, so don't expect it to be cheap anytime soon. One side effect will be that the numbers of farm animals, like cows, will be greatly reduced. Some day you may have to go to a zoo to see one. StuRat 16:12, 7 October 2006 (UTC)

The Chicago Museum of Contemporary Art has an exhibition with a nose being grown in a jar of growth medium. Produce enough snouts and you could gring them up to make bologna.Edison 20:10, 7 October 2006 (UTC)

That type of art really gets up my nose. :-) StuRat 01:08, 11 October 2006 (UTC)

BTW, somewhat unrelated but in a microbiology course I once attended one of the lecturers mentions that someone had considered culturing some single-cell thing to produce enough protein to replace all the soybean in Europe (to feed cattle I believe). They even built the worlds largest fermenter (now unused). But they worked out out wouldn't work because of all the subsidies etc it was cheaper to grow the soybean. I couldn't remember the details but from a quick Google I found (and remembered) it was ICI . It's called "single cell protein" and they were going to use Fusarium fungus . Evidently it may also have partially been because the petroleum products they require cost most then they expected and the Soviet Union were also looking in to it . But I think this does all highlight one key issue. As long as subsidies remain it will be difficult for culture systems to compete (unless these are also subsidiesed which IMHO is unlikely until they start to suceeded). Even if the subsidies are removed, this will likely mean that third-world countries will be the primary agricultural areas and their lower wages etc may mean culture systems will still have difficulty competing. Plus people are likely to be reluctant to trust culture and the large companies that will probably be running them. Almost definitely, they will initially replace feedmeal and later used as ingredients for companies selling prepackaged complex food rather then something the ordinary consumer will be using until much later Nil Einne 14:32, 15 October 2006 (UTC)

proteins

why do proteins absorb at 280nm?do they absorb at 200nm?

Absorb what ? StuRat 15:52, 7 October 2006 (UTC)

UV light, I imagine. See (for example) DNA extraction. --jpgordon 16:25, 7 October 2006 (UTC)

Different proteins absorb light at different wavelengths. Have a look at spectroscopy and for a machine which uses infrared absorption have a look at pulse oximeter.Mmoneypenny 17:54, 7 October 2006 (UTC)

Fossils made from bone

Hi, I've been interested in buying a fossil for my girlfriend's birthday (a diprotodon tooth actually: possibly one of the silliest examples of megafauna ever)! I've had a look at C & J Fossils. On this page they mention that the tooth fossils that they sell are not replacement fossils, but the actual teeth themselves. Is this possible? The page at Fossil does not really seem to mention it, except for "Some fossils consist only of skeletal remains or teeth; other fossils contain traces of skin, feathers or even soft tissues. This is a form of diagenesis." This reads to me like actual teeth would not last over 65 million years, but be replaced by minerals. Thanks in advance... -postglock 15:07, 7 October 2006 (UTC)

It could last indefinitely in the right environment, like buried in a desert or encased in stone or amber. Of course, over that long of a time period, many desert areas will have changed climate dramatically, so encasing it might be the only way to protect it for so long. Note that such methods will favor small fossils, as a T-Rex femur is unlikely to be entirely encased, and one small hole will allow replacement to occur. StuRat 15:47, 7 October 2006 (UTC)

Hmmm, well, I suppose for the price they are selling them at, they weren't encased in stone or amber. Wouldn't the other option, the desert, not really seal the fossil from the elements too well? I guess trapped in an icy cave might be another option, but I'd imagine also unlikely for 65+ million years...? -postglock 16:38, 7 October 2006 (UTC)

Teeth get replaced by minerals. The owners of that website may be mistaken, as some teeth, such as those from sharks, become fossilized and retain a smooth, shiny luster, despite having their minerals replaced by others from their surroundings. Diprotodon died out only around 50,000 years ago, so its fossils may actually retain some organic material. I've dug up 2 million year old megafauna fossils in Newberry, Florida, and they contained collagen. They were encased in clay, and were very brittle. Gary 18:08, 7 October 2006 (UTC)

Cheers, thanks for the replies! -postglock 00:45, 8 October 2006 (UTC)

diatomic elements

Why exactly do certain elements exist as usually encountered in their basic states within the periodic table diatomically? Is this simply yet another unexplained and unpatterened thought, or is there a particular reason in the explanation of certain elements- for instance, it being known that all halogens exist in diatoms? If the former answer is positive, then is there some sort of notable chemical result which might occur when one attempts to separate a diatom- by heating, for instance? And if not, why? Sorry- this is really a lot of 'firsts' but a complete answer would be appreciated to subjection in blind rote learning beneath a principle one does not care or cannot explore. Luthinya 15:28, 7 October 2006 (UTC)

You might know that chemical bonds occur whenever the energy of the bound molecules is lower than its constituents (because then you would have to put in energy to seperate them again). As explained at least roughly in the article on the covalent bond, pairing electrons usually lowers the energy. So, if you give each outer electron ( i.e., each electron which is not stowed away in a closed electron shell) a partner to pair up with, it will form a bond with this partner, losing energy and hence staying stuck. And where might a suitable partner for each electron of an atom come from? From a second atom of the same kind, of course. Hence, when two atoms of a gaseous element meet, their outer electros will pair up, the energy of the system is reduced, and a diatomic molecule is formed. This is, of course, only as easy with gases, because in solids, an atom is always equally close to several other atoms. And noble gases have no outer electrons and hence do not form diatoms. Simon A. 16:05, 7 October 2006 (UTC)

The above sounds good, but I also think that idea of diatomic elements arises from bonding and antibonding of MO theory. See the wikipedia article on antibonding where it gives an example with hydrogen. It basically is saying that bonds are likely to form if there is no antibond to counteract the bond, and if there is none, then it is more energy favourable to form a bond rather than exist as seperate atoms. I don't know your chemical background, so this explanation might be harder to understand versus the above. You could search google and look up simple versions of bonding and antibonding diagrams where you might be able to find one or two where it would show you why for instance fluorine exists as a diatom while something like argon does not. Perhaps someone can explain this better than me, but I think the theory is right. 72.56.169.205 16:17, 7 October 2006 (UTC)

The second poster might be right that I oversimplified things a bit too much. One thing I should add for the very least, as you specifically were referring to the example of halogens: There, a single sigma bond is formed (IIRC), such that the two atoms now share one electron pair. As they had before a nearly closed filled p orbital (5 instead of 6 electrons), the two paired electrons now sort of close off both orbitals. But the usual problem with covalent bonds is that all explanations are very hand-waving and insatisfying unless one really goes down to advanced quantum mechanical calculations which then justify then justify tings like the LCAO approximation. Simon A. 10:13, 8 October 2006 (UTC)

Additive Volumes and Mols

Hi, I'm going to be doing a lab in the coming weeks in my chemistry class.
Basically I have a reaction and I aim to produce an amount of product based on it. This is not a problem, I can figure out the number of moles of the product I want since I know the concentration and volume desired. I can then use mole ratios based on the reaction coefficients to figure out how much I need of the reactants. There are 3 reactants producing what I want. If I want 250 mL of product, how does it work if I need to combine the 3 volumes? Using mole ratios and figuring number of moles of each reactant I can do, but then wouldn't that just be the ratio for using 250mL of each reactant and not say 80 mL I intend to use for each and adding them together to get a final volume? I asked my teacher, he said that it might not work if I do additive volumes but I'd have to see when I do it, and if so I'd have to change the lab design (I'm guessing he just wants me to see what happens and try to solve any problems myself.) I've also noticed that some problems in my textbook for example say that they neglect volume changes (I guess to make the calculations easier). Any Ideas?
72.56.169.205 16:02, 7 October 2006 (UTC)

You first need t tell us whether you are talking about gases, liquids, solutions, or solids. Simon A. 16:07, 7 October 2006 (UTC)

Well it'd be in solution, an acid and two other species. 72.56.169.205 16:14, 7 October 2006 (UTC)

If you are using aqueous solutions that are relatively dilute, it is usually a good approximation to add the volumes. You will usually run into problems when mixing solvents, since they might sort of dissolve each other and you would end up with LESS volume. If you really wanted a certain volume, you could certainly use more concentrated reactants to get the correct number of moles, then dilute :) --Bennybp 02:48, 8 October 2006 (UTC)

Antacids

Does anyone know of any common food-stuffs which function as Antacids? Englishnerd 16:46, 7 October 2006 (UTC)

Baking soda is perhaps the simplest. Your box of Arm & Hammer should have a Drug Facts label for an antacid. --Russoc4 16:48, 7 October 2006 (UTC)

Yes, baking soda is one of my favorite foods. — X (SUPERDESK|Help me improve)

The Common chemicals article may also be of interest.--Russoc4 16:56, 7 October 2006 (UTC)

Shrimp diagram request for comment

This is a rough draft of an anatomical diagram of a shrimp. I am looking for feedback on accuracy. I would like suggestions and criticism. What should I do to improve it, is there anything I should change, did I make any mistakes? I was planning on adding a little more detail such as hairlines along some of the limbs and tail, and perhaps add color/shading/detail. Of course, I would also add lables as well. So comments would be appreciated. Thanks for your consideration. Please leave comments at Image talk:Shrimp.svg.--Andrew c 17:32, 7 October 2006 (UTC)

Is it any particular species ? StuRat 21:11, 8 October 2006 (UTC)

No. I would like help in establishing distinguishing features in order to make the image more accurate. Right now it is a generic shrimp. My references are about 7-8 images and diagrams found on the commons, wiki images, and google. Because of this, I may have a Frankenstein of a shrimp, which is why I am asking for external review.--Andrew c 00:48, 10 October 2006 (UTC)

Homework question

I knew that would be eye-catching! It's a homework question that I am trying to mark - should I mark as correct pupils who have put helium in the s-block? By definition, it is, of course, but we can also see why it is often put at the top of the p-block in the periodic table. So is it in the s-block, or more realistically a quasi-p-block element? --G N Frykman 20:08, 7 October 2006 (UTC)

It says on p-block that "... minus helium (which is located in the s-block)". I would mark correct. Iolakana•T 20:37, 7 October 2006 (UTC)

I think you should mark them correct, but when you hand the tests back to the class, explain to them that helium is grouped with the inert gases, on the right side of the periodic table, even though its only electrons are in an s orbital. Gary 22:39, 7 October 2006 (UTC)

The question is: What did you teach them about this? And what answer were you (or the text book) expecting? 8-)--Light current 09:13, 8 October 2006 (UTC)

Masochism

Is there any kind of cure for it? One that works, I mean. --OGoncho 20:18, 7 October 2006 (UTC)

You could try aversion therapy. Vitriol 20:28, 7 October 2006 (UTC)

Due to the nature of the subject, aversion therapy sounds like it could add fuel to the fire. --OGoncho 08:26, 8 October 2006 (UTC)

It was a joke, dude. Vitriol 13:53, 8 October 2006 (UTC)

A psychiatrist? They eventually deter you from being interested in it. Iolakana•T 20:39, 7 October 2006 (UTC)

This is the type of thing that you should talk to an expert about, rather than asking people on a website. A psychiatrist would have to ask for more information, but I would bet that the most important part of treatment is making the person want to stop causing themself pain. Are you looking to cure yourself of something self-destructive, or are you concerned about someone close to yourself?

You can respond by clicking the "edit" link to the right, but I would really suggest you talk to a medical professional if you or someone you know is hurting themself intentionally.Gary 22:32, 7 October 2006 (UTC)

I have the condition, but I am not here looking for professional advice. I'd like to know of the options, but I'm unlikely to act any time soon (if at all) given the taboo-ness of the subject. If there is a cure of some kind, I will speak to an expert about it if I ever choose to do such a thing. Masochism as I mean it is sexual response to certain scenarios, while you seem to be talking about self-harm or algolagnia. --OGoncho 08:26, 8 October 2006 (UTC)

Is it a disease?  --Lambiam 06:10, 8 October 2006 (UTC)

No, but it is not normal, and therfore it is a taboo. If it can be removed, it would be regarded a cure by many, even if this is not a proper term. --OGoncho 08:26, 8 October 2006 (UTC)

Look, you sound really hung up over it. Will you be shot if it is discovered you like this kind of thing? Vitriol 13:53, 8 October 2006 (UTC)

As you seem to be sure that you are not talking about self-harm but about masochism I wonder why you are looking for a cure. Remember that many non-mainstream sexual practices have first been considered as psychiatric illnesses and then no longer. Having learned its lessons from the history of homosexuality, psychiatry seems to have now understood that an aberation (i.e. a non-mainstream behavior) should only be considered an illness in need of therapy, if it causes suffering. So, do you suffer? Are you unhappy? Maybe you have found or will find a partner who allows you to live out your sexuality in a way that satisfies you both. If you doubt that you can find such a partner, if you fear that your masochistic tendencies may lead you to allow dangerous bodily harm to occur to you, if you cannot enjoy your sexuality due to feelings of guilt, or anything else of this kind, then you have a lot of stuff you might want to discuss with a therapist. I am no psychologist, but I imagine that it would be far from clear that your masochism turns out to be the actual root of your problems. And surf a bit on the web to reassure yourself, that there are plenty of people with quite bizarre sexual preference who actually live out their fantasies and seem happy with it. (No, i don't recommend reading porn sites, rather discussion sites about sex. They exist but require quite clever googling to stay clear of the porn.) Simon A. 19:14, 8 October 2006 (UTC)

Im surprised no ones mention the joke about the sadist and the masochist yet!--Light current 23:08, 8 October 2006 (UTC)

I made a joke already. Was it not good enough for you? Vitriol 01:11, 9 October 2006 (UTC)

Yes I laughed. Didnt you hear me? 8-)--Light current 01:29, 9 October 2006 (UTC)

Recent news regarding the treatment of Fetal Alcohol Syndrome

I'm trying to find an article I read a while ago (maybe a couple of months) which outlined success in inhibiting or even reversing a lot of the negative effects of the brain damage associated with FAS with early, intensive theraputic treatment. The article described the therapy as cognitive and emotional, and stated that the findings were preliminary because the kids were still very young. Ring any bells? Anchoress 20:44, 7 October 2006 (UTC)

One MeltBanana 21:19, 7 October 2006 (UTC)

That's the one!! Thanks a bunch, MB. I was sure it was on a Cdn news site, but I was so sure it was CBC I didn't bother looking on Canada.com. Cheers! Anchoress 21:45, 7 October 2006 (UTC)

Disproof of the theory that information cannot move faster than speed of light

You just get a really long pole, going from one place to the other. Then you push or pull it to make morse code, and the other place obtains the info instantly, faster than light. --216.164.197.56 22:47, 7 October 2006 (UTC)

• Fraid not. If your pole was infinitely stiff (fnarr) then this would work, but it isn't - it'll be compressed and elongated as you push and pull it. In a short pole you won't notice, but in a pole long enough to meaningfully test its movement against light, you'll find the pole lengthenings and shortenings take a considerably longer time to propagate along the pole (at the speed of sound for whatever the pole is made of, I guess). -- Finlay McWalter | Finlay McWalter|Talk 22:53, 7 October 2006 (UTC)

• It won't work. When you push an object you compress its internal structure, so basically its atoms push the others creating a wave of compression that travels along it, at the speed of sound for that particular material. The information will move at this speed, which will be much, much smaller than the speed of light for any real-world material. So like Finlay said, it would require an infinitely dense material in order to achieve speed of light, and by then the pole would just collapse into a black hole before you could have anything to push :) ☢ Ҡi∊ff⌇↯ 07:42, 8 October 2006 (UTC)

• worse yet! you cannot push or pull the pole fast enough. its impossible to get anything with mass (such as a pole) to move at the speed of light. in order to do the moarse code, you would be pushing and pulling the pole WAY slower than the speed of light no matter how much force you applied. you would be much faster off substituting the pole for a pulse of light itself.

A better way to "prove" this was mentioned a few months ago, by shining a flashlight on the moon and swishing it around so fast that the resultant beam on the moon appeared to move faster than the speed of light. It doesn't prove anything, though, because as mentioned above, you can't move your hand anywhere near the speed of light, so it's impossible for you to manipulate the shape in any way that would actually produce a useful fast message on the moon (i.e. you may be able to draw a line very fast, but you wouldn't be able to write a binary sequence that could be interpreted as information). Much more relevant is the fact that the photons are moving at an entirely predictable c, so there is still almost a considerable wait (1.3 seconds) before your super-fast moving flashlight beam reaches the surface in the first place.  freshofftheufoΓΛĿЌ  03:41, 8 October 2006 (UTC)

The first answer is right, the second not, I afraid. Indeed, the long pole would allow for transmission faster than ,light if it were perfectly stiff. This example is the reason why one says that special relativity is where the idealization of the rigid body, abundant in classical physics, breaks down. It is also no wonder that it does not work. After all, forces such as the push are mediated within the pole due to the electromagnetic repulsion of the atoms (the same force that keeps the solid from being compressed arbitrarily). And changes in these force fields only travel with light speed.

Freshgavin, you miss a point in saying, a pulse of light were faster, If the pole were perfectly rigid, it would be sufficient to just push it slowly. The other end would start moving as slowly but immediatly, i.e. somebody at the other would notice without light speed delay when you start pushing, I also wonder why you brought up the flashlight to the moon. This example is usually used to illustrate that certain things still may travel faster than light if they neither contain mass nor transport information. If you swivel a flashlight, directed at the moon, quite leisurely, the spot on the moon (if the light were bright and collimated enough) would move quite fast from one pole of the moon to the other, possibly faster tha light. However, the movement of the refelction of the spot on the moon surface is not the movement of the light, and there is also no transport of information along the path of the spot, but only along the light beam. Hence, there is no problem. Simon A. 07:18, 8 October 2006 (UTC)

I put "prove" in quotations to show that I was being sarcastic. I guess you didn't notice. Sigh. Also, you seem to be confusing my comment with the one before it.  freshofftheufoΓΛĿЌ  09:25, 8 October 2006 (UTC)

No, I didn't notice, sorry. Simon A. 09:54, 8 October 2006 (UTC)

Quantum tunneling is the best proof I've seen that info can move at superluminal speeds. StuRat 20:58, 8 October 2006 (UTC)

Being pedantic, it is possible for this to work, but your pole has to be in a dense medium, where the speed of light within the medium is slower than the speed of compression of the material of the pole. It's not faster than c, but it's faster than the light. Kind of. GeeJo ⁄_(c) • 22:16, 8 October 2006 (UTC)

Can a hard drive go through an X-Ray scanner?

Can a computer's hard drive go through an airport scanner (say it was in your luggage) without information loss, or would it be damaged? - Rainwarrior 23:40, 7 October 2006 (UTC)

It'll be fine. Millions of laptops and iPods go through airport scanners every day. -- Finlay McWalter | Talk 23:44, 7 October 2006 (UTC)

It's strong magnets that are the problem, and there's not really that much radiation coming from an X-ray scanner in the first place. (Disputed).  freshofftheufoΓΛĿЌ  03:34, 8 October 2006 (UTC)

I don't know about that. X-rays are ionizing radiation. They could have an effect, but the casing of the HDD might protect the disks. ☢ Ҡi∊ff⌇↯ 06:24, 8 October 2006 (UTC)

Yes, but the levels you're being exposed to in an X-ray scanner I wouldn't exactly call "strongly magnetic".  freshofftheufoΓΛĿЌ  07:03, 8 October 2006 (UTC)

Finlay suspects that not the magnets are the problem (there are non in X-ray machines) but the ionizing capacity of X-rays. But Freshgavin is right, ionizig radiation is not so much a problem. First, X-rays will hardly penetrate the metal case of a harddisk. Second, you might be thinking of DRAM where ionizing radiation is an issue because it might make the capacitors temporarily leaky. But I am unsure whether a hard disk without metal casing might in fact get erased by X rays. Simon A. 07:22, 8 October 2006 (UTC)

I wasn't differentiating between ionization and the electromagnetic effects produced by it. My bad.  freshofftheufoΓΛĿЌ  09:22, 8 October 2006 (UTC)

I believe the new scanners use THz frequencies.--Light current 09:09, 8 October 2006 (UTC)

Thanks for the replies! I think I've got enough of an answer. - Rainwarrior 03:40, 9 October 2006 (UTC)

I (guardedly) disagree. While there's no question that the magnetic information on the disks will be safe, at a sufficient intensity of X-rays, the Flash ROMs in the disk will be partially or completely erased, and without that data, your disk drive is just a lump of metal. (The flash contains not only the computer code that makes the disk's microprocessor work, it also contains disk-geometry information that is unique to your particular disk drive and couldn't be replaced or recovered if lost.) I have no idea what intensity of X-rays would be required, but if places still have warning signs (as used to be present in the old Hong Kong airport) that say "This X-Ray machine will fog your photographic film; ask for hand inspection!", I'd avoid running my disk drives through them as well.

Atlant 17:01, 9 October 2006 (UTC)

October 8

The effects of a smoker and non-smoker in the cold

Does a smoker feel the effects of the cold sooner than a non-smoker?12.145.200.157 00:29, 8 October 2006 (UTC)Jerry McShane—

Define "feel the effects of the cold". Are you asking if a smoker feels cold sonner when walking into air conditioning? Are you askign if a smoker catches a cold sooner? Are you asking if a smoker gets frostbite sooner? As it is, your question is too general to provide a discrete answer. --Kainaw 00:56, 8 October 2006 (UTC)

If the non-smoker is wearing gloves and is busy keeping his body warm, while the smoker is waving his naked hand around in the air and busy taking puffs on his cigarette, then yes of course the smoker would feel the cold. This really has nothing to do with smoking though.  freshofftheufoΓΛĿЌ  03:29, 8 October 2006 (UTC)

If the circulation has been resricted by aretheroma, then yes probably.--Light current 09:02, 8 October 2006 (UTC)

I often wonder whether the heat from a cigarette itself keeps people warm (presumably the smoke inhaled is warmer than say the cold air). Having never tried the stuff I have no idea if what i've just written is just crazy-talk or actually accurate!! ny156uk 16:47, 8 October 2006 (UTC)

By far, the greatest effect is that smokers stand outside in the cold getting their nicotine fix, where smoking indoors is prohibited. I'm sure they suffer more from the cold, as a result. StuRat 20:49, 8 October 2006 (UTC)

I work with smokers and in the winter with all things being the same the smoker seems to be effected by the cold much easier than the non-smoker. This is made me wonder why the smoker needs the heat turned up so much higher than the non-smoker. One thing that is made eveident is the fact that the smoker will burn you out with heat. could this be do to the capularies being restricted with blood flow.

If the circulation has been restricted by aretheroma, then yes probably.--Light current 21:00, 9 October 2006 (UTC)

Cold and fat

Does a person with higher body fat percentage feel the effects of cold sooner than someone with a lower body fat percentage? (The above question reminded me to ask.) Hyenaste  00:51, 8 October 2006 (UTC)

No, just the opposite, fat is an excellent thermal insulator. That's why you won't see any thin Inuits. StuRat 03:35, 8 October 2006 (UTC)

Some fat and short people I've seen are quite afraid of cold. Some may not be mentally adapted to the cold. -- Toytoy 03:52, 8 October 2006 (UTC)

I agree that fat is a good insulator, but it can also have to do with the reason people are fat. If it's because of hypothyroidism, then they'll probably feel the cold because overweight and cold sensitivity are two common symptoms. Anchoress 04:13, 8 October 2006 (UTC)

Germs

I recently read that you should wash handkerchiefs in hot water because they will survive a cold water wash. a) is this true, and b) even if they did survive, would they survive direct sunlight for an average day (i.e., on a clothesline)? BenC7 04:47, 8 October 2006 (UTC)

Was that "germs" or "vampires" you were asking about? B00P 04:59, 8 October 2006 (UTC)

Not really, leaving them exposed to the Sun won't do a job as good as boiling the handkerchief in hot water (much like in pasteurization). The ideal is, of course, put the handkerchief in boiling water for a few minuts and letting it dry on the Sun later. It should be pretty much sterile as far as I can tell. ☢ Ҡi∊ff⌇↯ 07:21, 8 October 2006 (UTC)

How do you get your 'kerchief ON the sun? And wouldnt that plasmarise it?8-)--Light current 09:05, 8 October 2006 (UTC)

Bleach is also useful for disinfection. StuRat 20:42, 8 October 2006 (UTC)

Bleach tends to rot your clothes.--Light current 22:36, 8 October 2006 (UTC)

Bacteria are killed by UV light, so the efficacy of disinfection by sunlight would be dependent on the UV intensity of the sunlight eg. see . So if you live in a place where the UV intensity is high then this effect will be more significant. The problem with threating handkerchiefs in this way in that bacteria on the skin (and in the nose) are often pigmented, ie. they produce coloured compounds. These compounds serve to absorb certain frequencies of light and thus enable them to survive better in sunlight. We used to do an experiment at university where we took a petri dish and left it out in the air for a few minutes then put it in the incubator. The bacteria that grow up are mostly pigmented, the reason being that it is them that can survive longer exposure to the sun. Personally, I use high temperature washing for handkerchiefs - and bath towels for that matter. Azaroonus 07:28, 15 October 2006 (UTC)

Disease

Please tell me which disease shows the following symptoms: 1. Body pain 2. Unability to remember anything new 3. Unability to concentrate 4. Loss of Reading speed 5. Headache(sometimes)

P.S. These symptoms are of a 15 year old

There is no amount of warning I can give you that would justify a non-professional answer to this question. The symptoms you describe are VERY SERIOUS and if you or someone you know are suffering of these symptoms, go to a qualified doctor IMMEDIATELY.  freshofftheufoΓΛĿЌ  07:00, 8 October 2006 (UTC)

Sure, but that wasn't the question. Are you assuming the questioner is a moron? DirkvdM 11:00, 8 October 2006 (UTC)

Well, the symptons match for it (just kidding). - Dammit 11:04, 8 October 2006 (UTC)

Did I respond innapropriately to this? Should we answer this kind of question? I honestly can't think of a reason why this question should be asked in a place like this, or a reason why it should be answered. What am I missing?  freshofftheufoΓΛĿЌ  16:47, 8 October 2006 (UTC)

Like I said, you didn't answer the question. The purpose of the ref desk is to answer questions. Some will give bad answers and therefore anything said here shouldn't be taken at face value, but that is so obvious that it hardly worth mentioning. Imagine a bar with a warning sign that medical issues may not be discussed there. :) DirkvdM 08:48, 9 October 2006 (UTC)

You know I'll be the last person to say that medical questions shouldn't be answered on the science desk. I just can't see the sense in asking such a question, unless it's some sort of homework, in which case they should have mentioned that in the first place.  freshofftheufoΓΛĿЌ  09:14, 9 October 2006 (UTC)

The bad news: it is harder to imagine a vaguer and less specific list of symptoms. Every single symptom affects someone sometime. There are a thousand diseases and conditions that can cause these, ranging from depression or sleep deprivation to encephalitis or hypothyroidism. We are not going to be able to give you a diagnosis. alteripse 13:28, 8 October 2006 (UTC)

Sounds like has a crush on someone. ♥ ♥ ♥ Tell him to ask her out! Hyenaste  17:28, 8 October 2006 (UTC)

Well this could be medical homework and not sufferred by the questioner!--Light current 17:32, 8 October 2006 (UTC)

I once suffered a few of the symptoms (concentration, reading, memory) in the short term after going all day not eating or more importantly drinking anything. I had trouble putting sentences together until i had a good drink of water. Any change you're not getting enough water throughout the day? Benbread 17:55, 8 October 2006 (UTC)

Severe tiredness, coupled with irritability caused by the tiredness. Philc _TC 21:13, 8 October 2006 (UTC)

sensitivity to sound

True or false: If a person is hypersensitive to sound, he/she cannot be hyposensitive to sound?

• True, Hyper-, and Hypo- are opposite prefixes, so noone can be hyper, and hypo anything --Englishnerd 11:58, 8 October 2006 (UTC)

But could they be hypersensitive to some sounds and hyposensitive to others?

Yes! See deafness. Hyper sensistivity to some sounds can occur after hearing damage.--Light current 17:34, 8 October 2006 (UTC)

I can attest to that. As a child I had a case of Cholesteatoma in one ear, which damaged my middle ear bones. I had surgery several times to treat the condition, but only very little could be done to restore my hearing in that ear. However, some sounds in the highest range of human hearing still pass through. Unfortunately this also leaves me very sensitive to these frequencies, because the inner ear is usually understimulated. --Pekaje 20:25, 8 October 2006 (UTC)

cochlea

True or false: 70%-80% of the cochlea is devoted to low frequencies?

Upon what do you bass that assertion ? :-) StuRat 20:07, 8 October 2006 (UTC)

Sounds like you're causing treble again? 8-)--Light current 22:32, 8 October 2006 (UTC)

We make such comments with far too high of a frequency. :-) StuRat 03:20, 9 October 2006 (UTC)

I cant top that!--Light current 03:59, 9 October 2006 (UTC)

Spiralling back to the original question, I'd note that the cochlea operates by sorting sounds by wavelength, so by definition, the first octave's worth of sensor must occupy 50% of the length of the cochlea, the second octave's worth of sensors must occupy the next 25% of the length, and so on...

So if by "low frequencies" you mean the first two octaves of frequencies to which the cochlea is sensitive, then I'd say that must be just about right.

Atlant 17:08, 9 October 2006 (UTC)

Hey thats clever reasoning!! Like a string instrument: it takes half the string for the first octave , then a quarter for the next, etc 8-)--Light current 21:02, 9 October 2006 (UTC)

Electromagnetic radiation.

What radiation will be emitted from an electrical substation on a housing estate, and how can I shield my house?

I think we had this one not so long ago.--Light current 22:33, 8 October 2006 (UTC)

I shouldnt worry. The transformer is surrounded by a metal casing connected to earth and acts as a Faraday cage. I would worry about it blowing up though, especially if it is old! 8-)--Light current 02:00, 9 October 2006 (UTC).

There is more to it than the transformer. Unless the substation uses shielded underground cables and gas insulated buswork and switchgear, there is likely to be an electromagnetic field propagated (60 Hz in the US, 50 Hz most other places) from the power lines and buswork. See "Power Over People" by Louise B. Young, Paperback: 272 pages,Publisher: Oxford University Press, USA; Rev&Updtd edition (September 3, 1992) Language: English ISBN: 0195075781. It has a good if dated treatment of some issues regarding electromagnetic radiation. The distribution lines near homes also generate electromagnetic radiation. Also see "Health concerns" in the article Electric power transmission. Electric blankets, other appliances and wiring inside your home will doubtless produce a higher electromagnetic fiels than a substation a considerable distance away. Studies on health effects of powerline frequency electromagnetic radiation have shown mixed results. There does not appear to be a Misplaced Pages article on the possible harmful effects of power line radiation. Given the contentiousness of the issue, I wonder if there was one which got deleted. Edison 18:31, 9 October 2006 (UTC)

Sorry, you are ill informed. All switchgear busbars and UG cables (LV and HV) are surrounded by earthed metal sheaths right up to your dostribution panel in your house! Switch gear does not have to be GIS to be sheilded. THere is absolutely no EMF on the outside of switchgear abart from tiny pulses cuased by partial discharge activity.

Overhead lines are another matter altogether.--Light current 21:09, 9 October 2006 (UTC)

Euphoria caused by Victory?

Misplaced Pages need work on the victory and euphoria articles, which offer nothing beyond a tiny, basic definition and disambiguation options. My question is, as you might guess from the subject, 'does victory cause euphoria?' A lot of cultures seem to describe victory (as a noun, I guess) as being a distinct emotion resulting from winning/success. I've never experienced anything I would describe as euphoria from victory, but I've heard it described by others as such. I realize this might be a very relative question, but I'd really like more information on the brain chemistry involved; there's certainly an evolutionary pressure for individuals to desire success for reasons beyond whatever they're succeeding in. I wish there was a better victory page. :( --Demonesque 10:52, 8 October 2006 (UTC)

Endorphins? --jpgordon 05:02, 9 October 2006 (UTC)

Urrr, if you care that much about wining it might, i dunno. Philc _TC 17:30, 9 October 2006 (UTC)

Time Dialation Confirmation

I got into an argument yesterday about Time Dialation and if it is or is not necessarily proven. I've seen the experiments listed in the Time Dialation article we have, but I am not convinced that time is a physical dimension that can be effected by gravity and speed -- if it were, then "time travel" would be possible, which logic proves it isn't (unless "alternate universes" are created to deal with causality -- and that's just absurd).

Anyway, someone cited an experiment in which two atomic clocks were synced up, and one was taken on a high-speed plane and then they found out that they were out of sync afterwards. However, I never got a source for this. Could someone provide me with it, please?

Further, if time dialation is proven and concrete, how do those of us who define time as being a concept used to sequence events rather than a physical dimension justify that belief? --Demonesque 11:00, 8 October 2006 (UTC)

First of all, time dilation does not give rise to the classic time-travel paradoxes that disrupts causality. For that to happen you need to travel back in time (to reverse causality) so time can very much still be used, as you say, to sequence events. Infact, this is pretty much the definition of time (by the second law of thermodynamics). Not exactly, but pretty much anyway. Just because time goes at different speeds depending on gravity and velocity does not mean that it can suddenly travel backwards. Time dilation introduces ALOT of other paradoxes, but it does not introduce causality issues Oskar 12:07, 8 October 2006 (UTC)

As for experimental confirmation, see Hafele-Keating experiment, and related ones at Time dilation#Experimental confirmation Oskar 12:11, 8 October 2006 (UTC)

Yes, I know that Time Dialation doesn't introduce causality issues, but my question is -- if time can be affected by speed and gravity then it is a physical dimension which then, theoretically, enables backwards travel through time. Time Dialation (to me) means that it is a physical dimension. --Demonesque 13:35, 8 October 2006 (UTC)

Here's how I think about it.

• The effects of speed and gravity on time doesn't make it a dimension, which I would say is just mathematical model of reality (though perhaps a very natural one).
• If time is regarded a dimension, it's not obvious that you can travel in it. Atleast not the way you want to.

—Bromskloss 13:58, 8 October 2006 (UTC)

Look this is a very complicated matter, the exact nature of time, and it cannot be explained in a short answer on the reference desk. You are making some fundamental misunderstandings about time. It is not a dimension like x,y,z is a dimension, it is fundamentally different. We use it as a dimension in spacetime because then physics makes sense, but we never claim that it is an "equal" to the other three dimensions. And I still don't understand how you can make the logical jump from "in different reference-frames time can move in slightly different speeds" too "time can travel backwards!". It doesn't make any sense. Bring a concrete example of what you mean, and perhaps I can explain it too you. If you really are serious about learning about this stuff, buy A brief history of Time by Stephen Hawking. It explains all of these concepts in a simple straightforward way. Oskar 14:23, 8 October 2006 (UTC)

"...if time can be affected by speed and gravity then it is a physical dimension..." How did you reach this conclusion? Time is a dimension, just not a physical one. Clarityfiend 19:06, 8 October 2006 (UTC)

Well Oskar, thats strange! Einstein says in his book 'Relativity' that Minkowskis four dimensional space is real and 'time is robbed of its independence'. p57. To obtain this 4 dimensional space, merely requires the 4th dimension to be represented by i.ct, where i = sqrt(-1). THe only thing the i operator does IMO, is to place the new dimension orthogonal to the other 3.

Einstein also says:

We can regard Minkowski's 'world' in a formal manner as a four dimensional Euclidean space (with imaginary time cooordinate): the Loretz transformation then (merely) corresponds to a 'rotation'of the coordinate system in the four dimensional world

--Light current 02:15, 9 October 2006 (UTC)

So, its not time thats the fourth dimension, its the speed of light multiplied by time another direction altogether!!!

Speed x time = distance. Distance is not a dimension. JackofOz 02:30, 9 October 2006 (UTC)

Correct! ct is a distance in the 4 th dimension. THe direction of the fourth dimension is orthogonnl to the other 3.--Light current 02:46, 9 October 2006 (UTC)

It's time dilation, not "dialation". StuRat 20:04, 8 October 2006 (UTC)

Stretch it any way you want!--Light current 02:15, 9 October 2006 (UTC)

Yes, I suppose you could put that spin on "dialation". :-) StuRat 03:17, 9 October 2006 (UTC)

Only if you have a very old phone! 8-)--Light current 03:23, 9 October 2006 (UTC)

Does snoring affect the snorer's hearing?

How does snoring affect the snorer's hearing? I would assume there is some sort of detrimental affect. Does anyone know of any studies on this? Thanks

I don't see why you should assume any detrimental effect on hearing. Most snoring is fairly quiet anyway.--Shantavira 17:20, 8 October 2006 (UTC)

I don't know of any studies, but it seems to be a truism to me that the cilia inside your ear would be affected by any external stimuli, whether you're awake to notice it or not. Would the average person's soft snoring be of any concern? I doubt it. Would it potentially be detrimental over a number of years if your snoring was unusually loud? Yes. --Aaron 17:32, 8 October 2006 (UTC)

I wouldt say most snoring is quiet!. I woke my self up at least once with my own snoring!--Light current 17:38, 8 October 2006 (UTC)

What? What's that you say?Edison 18:51, 9 October 2006 (UTC)

bizarre

Science says protons are positively charged and tightly clustered in the nucleus, but like-charges would strongly repel in such close proximity. Why doesn’t the nucleus fly apart?

kylie

The strong (or weak - can't remember which, sorry) nuclear forces hold them together. —Daniel (‽) 13:57, 8 October 2006 (UTC)

It's the strong force Oskar 14:26, 8 October 2006 (UTC)

It's the quantum chemistry that does it, they don't orbit, they delocalize--71.249.23.233 14:55, 8 October 2006 (UTC)

Quantum chemistry talks about the electrons not the nucleons. Strong force is the right answer. Protons not only have positive electric charge, but also so-called colour charge which subjects them to the strong attractive effect of the stron force. See there for details. Simon A. 18:56, 8 October 2006 (UTC)

Since protons do not carry color charge, nuclear force is a slightly better answer. Melchoir 22:23, 8 October 2006 (UTC)

A slightly easier-to-understand explanation than is found in the article can be found here. (Use the arrows in the top-right of the screen to go backwards and forwards.) If you don't understand it the first time, don't worry. I had to read it a couple of times before I properly 'got' it, too. BenC7 05:16, 9 October 2006 (UTC)

difference between AC DC current

can anyone please tell me the difference between AC and DC current

See alternating current and direct current for explanations of those terms. TenOfAllTrades(talk) 14:57, 8 October 2006 (UTC)

Heart Rate

During a strenuous mountain race which I completed in 6 hours, I notice from my heart rate monitor that for the first three hours my heart rate averaged about 160 bpm which is consistent with my training experience, whilst for the second half the average was about 140 bpm which is substantially lower than expected. The terrain was equally difficult at all stages of the race. The question then, does heart rate decline as an endurance athlete grows progressively more tired - especially if he has passed the 'exhaustion limit' built up by training ? I personally 'hit the wall' at about 4 hours.--Dr snoobab 17:10, 8 October 2006 (UTC)

Was it possible you were suffering palpitations, or escaped beats?--Light current 17:45, 8 October 2006 (UTC)

Valid point about the palpitations - noting reference made in the article to overexertion, faintness, dizziness - all of which I experienced.--Dr snoobab 16:02, 9 October 2006 (UTC)

technology in manufacturing surgical instrument

I am interested in knowing the latest technology being employed in the manufacturing of surgical instruments. are there CNC machines available for making dies which could be then used for manufacturing of instruments on large scale?

A stamped or die-pressed surgical instrument would be of poor quality. That might make a reasonable starting point for machining a tool with sharp edges, such as a scalpel, however. StuRat 19:57, 8 October 2006 (UTC)

how to make this

in the following website there is a pic of a plant cell .I plan to make it for my bio project .i think i will use gypsum to make the structure of the organelles . is it a good idea . what should i do about the cytoplasm and valcuole (they are supposed to be transperant ,are'nt they).any suggestions or comments to make it betterMi2n15 18:10, 8 October 2006 (UTC)any idea how to construct the endoplasmic retticulum ,the golgi apparatus and the mitochondria.Mi2n15 18:14, 8 October 2006 (UTC)

Maybe you could use dense clear gelatin for the cytoplasm. I don't know if that would cause your gypsum organelles to fall apart though. For the vacuole, you could place an inflated balloon in there while the gelatin sets and then remove it once it has solidified. I remember when I did this project, I used plastic wrap for cytoplasm and a clear balloon for the vacuole. I totally wanted to use gelatin though. Hyenaste  18:19, 8 October 2006 (UTC)

i think gelatin would be messy , any idea how to carge the cell wall and other organelles out of gypsum, do you get coloured gypsum??Mi2n15 17:37, 9 October 2006 (UTC)

Popping pimples

What is the clear fluid that emerges when you squeeze a pimple for too long? And the semi-solid stuff that comes out when I pop a lump with a small black dot in the center? Scienceman123 talk 19:09, 8 October 2006 (UTC)

Have you read our article on pimple? Or did you seriously not expect us to have one? Of course, we have, because Misplaced Pages knows everything. Now, the kind of pimple with black dot is simple. The black dot is dirt that obstructs the exit of a sebaceous gland, such that the sebum fills up the gland, letting it swell. Over time, the sebum becomes hard and "semi-solid" as you call it. For the clear fluid I am unsure. Maybe it is sebum, maybe it is pus. Anybody else in the know? Simon A. 19:25, 8 October 2006 (UTC)

The white stuff is pus, which is a mixture of bacteria and white blood cells, which are fighting the bacteria. The clear stuff is sebum, mostly oil, produced by sebaceous glands and sent up via pores to the skin. The pimple develops in the pore and blocks the flow of oil to the skin. The exposed portion of the pus can dry to form a whitehead and that can then absorb dirt to become a blackhead. I've found that consumption of trans-fats thickens the sebum and further aggravates acne. If you limit your fat consumption to vegetable oils, they will stay liquid and flow out of the pores without causing acne. StuRat 19:20, 8 October 2006 (UTC)

Actually the black stuff is not dirt, it's oxidised sebum. And the clear stuff can be sebum, but in a pimple it's plasma (blood without the red corpuscles), drawn to the pimple by inflammatory agents. Anchoress 19:48, 8 October 2006 (UTC)

So are the things that hurt when you pick them and try to pull them out, and when you finally do, you see that it is actually something like consolidated oil, modified sebum? — X (SUPERDESK|Help me improve)15:13, 9 October 2006 (UTC)

I agree with Anchoress. The clear stuff in question is probably blood plasma, which is usually runny and less viscous than oil or sebum. - Cybergoth 16:01, 9 October 2006 (UTC)

ABOUT PHARMACY?!!!

HI I'm attending the faculity of pharmacy in Syria,Middle East. And I just wanna know about the majors in pharmacy?!! thank you alot

Wouldn't your faculty be a better place to ask that question? -Obli (Talk) 22:37, 8 October 2006 (UTC)

Quercus × rosacea

How does one pronounce the x in Quercus × rosacea? --Auximines 20:40, 8 October 2006 (UTC)

Try the Language Ref Desk (and what letter are you talking about, anyway ?) StuRat 21:19, 8 October 2006 (UTC)

It's not an x but a ×, which leads me to believe it is pronounced as the word "cross". Hyenaste  21:43, 8 October 2006 (UTC)

According to it's simply an abbreviation indicating it's a hybrid, so I guess in your case it would be "Quercus hybridised with rosacea" -Obli (Talk) 22:34, 8 October 2006 (UTC)

I think in this case, × rosacea is a named hybrid in which case I believe it should be pronounced "Quercus hybrid rosacea". For unnamed hybrids, the form would be (e.g.) Sarracenia alata × minor and this could be pronounced "Sarracenia alata crossed with minor" or "Sarracenia alata hyridised with minor". I think I've also heard "Sarracenia alata by minor" used, and this to me seems the most elegant, although I can't find a source to verify it so you may not be understood using that form. Hope that helps! --YFB ¿ 22:44, 8 October 2006 (UTC)

It strikes me as the sort of information that is obvious on the academic and professional level and is just passed on by word of mouth because it's too insignificant to put in a book. -Obli (Talk) 23:13, 8 October 2006 (UTC)

The only reason I've encountered it is because I used to be very interested in carnivorous plants (still would be if I wasn't in Uni and had somewhere to put them), hence the Sarracenia example. It's the sort of thing I'd like to see included in hybrid name, if we can find some proper citations. --YFB ¿ 00:31, 9 October 2006 (UTC)

ACCELERATION of light

Is it safe to say that light does not accelerate, but always moves at c? If there was a chance it didn't, is it theoretically possible to measure such an acceleration? 81.93.102.3 20:52, 8 October 2006 (UTC)

To my knowledge, light does not accelerate. C is a constant, and therefore will not change at any time in a vacuum. However, if you change mediums, like going from water to air, you would have to use refraction indices and angles and plug into Snell's law to calculate the new velocity of light in the new medium. Hope I answered your question. --Nishkid64 21:02, 8 October 2006 (UTC)

A photon has 0 rest mass, so if it did accelerate, it would be instantaneous anyway, which is the same as no not having accelerated at all (i.e. always traveeling at c) i think. Philc _TC 21:10, 8 October 2006 (UTC)

First of all, acceleration doesn't necessarily mean "change in speed". An object moving in a circle is accelerating, but not changing speed, because only the direction of the velocity vector changes, not its magnitude. Second of all, light does not always move at c. Glass has an index of refraction of about 1.5, which means light moves at 2/3c through glass. So I guess you could say light "accelerates" at the surface of a piece of glass (and that's what causes refraction). Third of all, even in a perfect vacuum light doesn't move in straight lines, but geodesics of spacetime, which are affected by gravity according to general relativity. So I guess you could say light "accelerates" in a gravitational field too, which causes things like gravitational lensing. —Keenan Pepper 21:55, 8 October 2006 (UTC)

About the change of speed when moving from one medium to another. That is an acceleration, but only on average. As Philc said, I assume the change will be instantaneous. So even though, strictly speaking, there is an acceleration, that is a somewhat deceptive way of putting it. DirkvdM 08:55, 9 October 2006 (UTC)

It's not instantaneous for an index gradient. —Keenan Pepper 23:03, 9 October 2006 (UTC)

It's not really an acceleration either, because no one photon changes speeds. The photons always move at c, and in various materials they travel in a series of jumps (each at c) that average to a smaller speed. The patterns in the classical electric field or the quantum-mechanical photonic wave function may change speeds smoothly (on length scales large compared to the material components but small compared to the changes in refractive index), but there's no physical object that accelerates. This question doesn't really have a good answer because in order to speak properly about light such approximations as average values and smooth accelerations must often be abandoned. As far as general relativity goes, travelling along a geodesic is precisely the definition of not accelerating; locally, such paths are straight lines. --Tardis 16:39, 10 October 2006 (UTC)

What is the difference between a nuclear explosion and a nuclear reaction?

Does anyone know?

A nuclear explosion (see nuclear weapon) is just what happens when you have a really fast, uncontrolled nuclear reaction in a confined space. Nuclear reactions intended for electricity production or isotope production are controlled with things like graphite rods to slow down the reaction (see nuclear reactor). --Allen 23:40, 8 October 2006 (UTC)

Also see nuclear chain reaction... that's really what I'm talking about above; technically a nuclear reaction doesn't have to be exothermic or self-sustaining. --Allen 23:43, 8 October 2006 (UTC)

So, simply put, a nuclear explosion is a specific case of a nuclear reaction. DirkvdM 08:57, 9 October 2006 (UTC)

October 9

Car, chain

how do you pull a car with a chain and one person

Im not trying to block you, but Im sure that you can tackle this question on your own--Light current 01:33, 9 October 2006 (UTC)

This guy's trying to subtly point out the magicalness that is the block and tackle. Vitriol 01:44, 9 October 2006 (UTC)

"Magicalness"... that's interesting :). --liquidGhoul 02:01, 9 October 2006 (UTC)

Is the person who pulls the car the puller or the pulley ? StuRat 03:10, 9 October 2006 (UTC)

Ur pulling our legs!--Light current 03:11, 9 October 2006 (UTC)

If I'm pulling your legs may I be put on the rack, then drawn and quartered. :-) StuRat 00:59, 11 October 2006 (UTC)

You're making this way too complicated. Get a really big person. Clarityfiend 05:46, 9 October 2006 (UTC)

Or a really small car. DirkvdM 08:59, 9 October 2006 (UTC)

Kidding aside, what is the chain for? Or the tackle and stuff? Just push. I've done that (even slightly uphill once) and I'm not even particularly strong (except for my legs, I must admit). DirkvdM 09:03, 9 October 2006 (UTC)

You just have to remember to let the hand brake off. Richard B 21:28, 9 October 2006 (UTC)

The car must be in Neutral and the emergency brake released, with a licensed driver at the wheel (so the car does not get away from you and crash into something, or run over you if you are running alongside trying to push and steer). If it has power steering, the steering effort will be much greater than normal if the engine is off. Edison 14:26, 10 October 2006 (UTC)

Babirusa

I was wondering if you could help me find a source for a piece of information that could go in the article; I don't know if it goes here but their doesn't seem to be a help section for Misplaced Pages itself. On the talk page it has a section called 'The antidote?'. I don't know a good way to sum it up, so go and read it. The point is, the piece of information removed is true; I saw it on The Life of Mammals. The animals congegrate at a natural patch of a type of clay that neutralises poison in plants they eat. Although this is a fact, my Googling skills are poor so I don't know a reputable webpage I could cite. Any help? (P.S., the section on if they're kosher or not is bizarre and I don't know if it should be in.) Vitriol 01:21, 9 October 2006 (UTC)

The BBc's own website http://www.bbc.co.uk/nature/animals/features/274feature1.shtml is much more guarded on the reasons for them eating the clay so maybe it is uncitable as a fact. Curse that evil Attenborough. MeltBanana 01:48, 9 October 2006 (UTC)

Size of Human Epidermis Cell

Around how many micrometers in length is a human epidermis cell? Thanks. --Proficient 01:33, 9 October 2006 (UTC)

Which bit? Try here. Vitriol 01:42, 9 October 2006 (UTC)

I'm not sure actually. Whichever would come off if you scraped off a sample and put it under a microscope... --Proficient 05:02, 9 October 2006 (UTC)

I have another question: What color are the organelles of cells, specifically eukaryotic cells? (I know chloroplats are green, but what about ribosomes, mitochondria, and such?) I would assume that it might depend on the specific type of cell, but I want to make sure. When looking at them in microscopes, it would also depend on the dye, I believe. Whenever I see diagrams, they tend to be different from one another. So what color are they if they were able to be seen clearly without dye? This is a weird question, but thanks if you can answer it. --Proficient 05:08, 9 October 2006 (UTC)

why cant saltwater fish live in freshwater?

why cant saltwater fish live in freshwater? answer this in referance to teh cell function and stucture— Preceding unsigned comment added by 68.19.209.91 (talk • contribs)

Get up now, get on up, and do your own homework! Vitriol 01:59, 9 October 2006 (UTC)

I believe they would get bloated. --Proficient 05:15, 9 October 2006 (UTC)

When fat people swim in the sea, do they shrink? DirkvdM 09:06, 9 October 2006 (UTC) ps, if so, please don't tell them - the sea level is rising enough as it is. DirkvdM 09:08, 9 October 2006 (UTC)

If they do it for a couple of hours every day, and follow a sensible diet, they should look buff in a few months. Like a Diana Nyad.Edison 18:56, 9 October 2006 (UTC)

Mucopolysaccharidosis

mucopolysaccharidosis is a genetic disorder in which the person is lacking an enzyme normally found on the lysosomes. plants dont seem to suffer from the disorder. why dont plants have the disorder and what are the results of the disorder on the cell function?— Preceding unsigned comment added by 68.19.209.91 (talk • contribs)

As for plants, diseases rarely affect both people and plants. As for cells, see the first paragraph of Mucopolysaccharidosis where it says "People with a mucopolysaccharidosis either do not produce enough of one of the 11 enzymes required to break down these sugar chains into proteins and simpler molecules or they produce enzymes that do not work properly. Over time, these glycosaminoglycans collect in the cells, blood and connective tissues. The result is permanent, progressive cellular damage that affects the individual's appearance, physical abilities, organ and system functioning, and, in most cases, mental development." Dar-Ape 02:02, 9 October 2006 (UTC)

thanx

HOMEWORK QUESTION

the nucleus of a eukaryote is often referred to as the control centerof the cell. eukaryotes have a true membrane bound nucleus but prokaryotes just have a nuclear region. what is the advantage to having your dna isolated form the rest of ur cell?— Preceding unsigned comment added by 68.19.209.91 (talk • contribs)

See Vitriol's comment above. -Fsotrain 02:08, 9 October 2006 (UTC)

Did you read the top of this page? "Do your own homework. If you need help with a specific part or concept of your homework, feel free to ask, but please do not post entire homework questions and expect us to give you the answers." Please see Cell nucleus. Dar-Ape 02:10, 9 October 2006 (UTC)

Gene defect

Some people are born with a gene defective for a channel protein. The result is that a channel in the plasma membrane is larger than usual and seems to allow Na ions to enter and leave the cell freely. What are the short and long term health ramifications be and what dietary adjustments could we make to help treat such a person?— Preceding unsigned comment added by 68.19.209.91 (talk • contribs)

I was going to say: "Dietary adjustments are best recommended by medical professionals, not by anonymous users on Misplaced Pages. Please see a doctor instead." but I see from your question above that this probably a homework question. --Canley 02:44, 9 October 2006 (UTC)

There is no such defect that affects the primary Na-K channel in all the cells of the body. It likely would be lethal. A number of "channelopathies" are known, affecting specific symptoms. No dietary treatment would be likely to affect an Na channel defect with the sole exception that if the defect is primarily restricted to the tubules and collecting ducts of the kidneys, extra dietary salt would compensate to a significant degree. alteripse 12:51, 9 October 2006 (UTC)

bursting cells

how come an animal cell will burst if it lets to much water in but plant cell dont? — Preceding unsigned comment added by 68.19.209.91 (talk • contribs)

Cuz plant cells got cell walls of cellulose and animal cells ain't now stop asking homework questions and do your own research. It's probably in that bio book of yours. =O Hyenaste  02:54, 9 October 2006 (UTC)

nah.. i looked in my book for about an hour for all of these questions and never found anything. ive been looking on the net for at least 3 hours for an answer to any of these and havent found anything close to an answer. — Preceding unsigned comment added by 68.19.209.91 (talk • contribs)

Have you got the right book? Its the biology one you need! 8-)--Light current 03:10, 9 October 2006 (UTC)

yes...i hae the right book$$~& — Preceding unsigned comment added by 68.19.209.91 (talk • contribs)

Look here Plant_cell--Light current 03:19, 9 October 2006 (UTC)

If you are really having problems with your book, this website has some good narrated biology animations. Also, please sign your comments with ~~~~ Dar-Ape 03:20, 9 October 2006 (UTC)

What's in a plant cell that's not in an animal cell? --Bowlhover 05:52, 9 October 2006 (UTC)

Like Hyenaste said, cell walls of cellulose. And chloroplasts --GangofOne 09:46, 9 October 2006 (UTC)

Stop bitching at people who ask for help with homework, we dont do homework for people, we are happy to help with it though. Philc _TC 17:43, 9 October 2006 (UTC)

cell theory

why did it take 150 years after van leeuwenhoek found "animicules" to come up with a cell theory?

six homework questions in a row? do you have a deadline soon? Xcomradex 03:50, 9 October 2006 (UTC)

Why dont you learn how to use wikipedia by searching yourself? And please sign your comments!!--Light current 03:53, 9 October 2006 (UTC)

This seems less homeworky so I'll field it (as in, I don't think it's a homework question and you're just biting a newbie). If you didn't know that animals were made from cells you could argue that macroscopic animals are much like single-celled ones (as in, made from organs/organelles and things but do not scale down further). Vitriol 03:55, 9 October 2006 (UTC)

Grist for the alternative history mill: van leeuwenhoek noticed that the little animicules he scraped off his teeth were killed when he drank a hot beverage. If he (or say Edward Jenner) had developed the germ theory of disease from this observation, how would medical science have advanced? It seems like a lot of time was wasted between van Leewenhoek and Pasteur.Edison 19:02, 9 October 2006 (UTC)

About the Big Bang

I was reading about the Big Bang, Speed of light and escape velocity among other topics and I ended kind of puzzled. I tried reasoning all that I read and I was trying to reason the following 'postulates':

1. At some point in time everything in the universe was toghether in a single 'point'. 2. Nothing can move faster than the speed of light. 3. The escape velocity of a black hole is faster than the speed of light wich is why not even light can escape. 4. All matter and energy exploded at the event known as the 'big bang'.

Considering all of those postulates as true seams to lead to a big contradiction because if we consider points 1-3 then point 4 would be impossible because it would imply that everything in the universe at some point was moving (considerably) faster than the speed of light (to achieve the incredible speed i suppose would be need to escape from the gravitational pull from all of the mass in the universe combined).

How could that be?

I'm thinking it has something to do with one of my 'postulates' being wrong or missinterpreted. My limited knowlege in this field doesn't allow me to answer this question so I was wondering if anyone here could help me figure this puzzle out.

No this is not a homework and no i don't have a deadline. It's just a question i've been asking myself for a couple of months now.Nnfolz 04:57, 9 October 2006 (UTC)

While I'm sure someone else will answer this in more detail, the idea is that all the time, matter and space in the universe "inflated" from that point, rather than "exploded". BenC7 05:24, 9 October 2006 (UTC)

I also won't go into the full details, but I will point out that while special relativity says that no matter/energy/information can move locally faster than light (i.e. an observer very close by in space will never see anything going faster than light), space itself is neither energy nor matter nor information (not quite, at least), and so the space can expand at whatever speed it pleases. Confusing Manifestation 09:04, 9 October 2006 (UTC)

Another lame answer is that close to the Big Bang (in time), the laws of physics break down. Another way of saying "we haven't a clue". And of course I can't resist pointing to my alternative to the Big Bang theory. DirkvdM 09:18, 9 October 2006 (UTC)

The speed-of-light limit is with respect to a metric, i.e. a way of giving a meaning to distance and time in order to define what speed means. This metric comes from spacetime and it is spacetime itself that expands, and it is not limited to the speed of light. Simon A. 17:02, 9 October 2006 (UTC)

Human skin colour

Why is human skin the colour it is (ranging from a very pale pink to a dark brown shade)? I know the variations are caused by melanin levels, but I'm curious as to why we aren't blue or green or something. CameoAppearance 05:18, 9 October 2006 (UTC)

Great question. I don't know the answer, but looking at the box at the bottom of brown, I would say that human skin color is really all shades of brown (not so much pink, really). And brown is considered a "neutral" color, although I admit I don't really know what that means. Looking at nature, it seems that things that come in non-neutral colors tend to have good reason to be those colors -- leaves are green because the pigments for photosynthesis happen to absorb the other frequencies. Frogs and peacocks and butterflies come in crazy colors for defense, or sexual selection or stuff like that. But we humans, though we need some color for UV protection, it doesn't really matter what color it is. And things where color doesn't matter -- tree trunks, roots, worms, dog paws, most mushrooms -- seem to tend to be brownish. Could it have something to do with brown being (according to its article) a tertiary color in the "original sense"? It's what you get when you mix together all three primary colors, so maybe when you throw together various atoms and molecules, in the absence of evolutionary pressure on hue, you tend to get brown? --Allen 06:38, 9 October 2006 (UTC)

I don't have specific answer, but note ALL MAMMALS are in the range of browns to black, and maybe white hair, with only a few exceptions, like purple-assed baboon, and mandrill. The previous answer sounds good to me. --GangofOne 09:40, 9 October 2006 (UTC)

It seems that in mammals, skin colouring pigments such as melanin and evolved primarily to protect the skin from UV radiation, while for purposes of camouflage or mimicri, fur colour is varied. As fur is a common chararteristic of all (or most) mammals there was no evelotuionary pressure for varying skin colour -- it would pointless as one cannot see it underneath the fur, and so everything stayed with the UV protection compounds that worked out well. At least that's my guess. Simon A. 17:07, 9 October 2006 (UTC)

The "other one" is another form of melanin, orangy rather than brown. The two forms are pheomelanin (red to yellow) and eumelanin (dark brown to black).

Atlant 17:16, 9 October 2006 (UTC)

In order to be blue or green, wouldn't we have to have copper in our blood instead of iron? User:Zoe|(talk) 02:55, 10 October 2006 (UTC)

Yeah, I suppose. Well, my question's been answered. Thanks! CameoAppearance 16:25, 10 October 2006 (UTC)

Well, humans who don't have much (of either type) of melanin are pink as a result of our red blood, but that relatively-unsaturated color could be easily over-ridden by other pigments in the skin; note in particular the mandrill. Also, pigments aren't the only way to generate color. Some of the most-brightly-colored feathers and scales are often colored as a result of diffraction patterns. So if there were some evolutionary advantage to us being, say, bright blue, that's probably what we'd be.

Atlant 17:41, 10 October 2006 (UTC)

international awards in physics.

Nobel prize has been critized(particularly in science)for awarding people after their career has almost ended(as if a lifetime acheivement award) rather than award "to encourage young minds". IS THERE ANY UPCOMING AWARD CEREMONY THAT ASSURES PRIZE TO YOUNG MINDS(IN PHYSICS)?____202.71.153.76 05:22, 9 October 2006 (UTC)ANURAG

Please don't shout. DirkvdM 09:23, 9 October 2006 (UTC)

see List of prizes, medals, and awards --GangofOne 09:31, 9 October 2006 (UTC)

Did you try Ig Nobel Prize ? -- DLL 17:03, 9 October 2006 (UTC)

The IISEF is one of the highest honors. — X (SUPERDESK|Help me improve)02:41, 11 October 2006 (UTC)

prices of toluene

when looking up the prices of toluene in chemical market reporter, I see "Toluene, spot" and then a per pound price. What does the "spot" mean?

Probably Spot price. Clarityfiend 05:42, 9 October 2006 (UTC)

Oil absorption into skin

When you rub oil into your skin (such as for massage or to moisturize dry skin) it seems to be absorbed. This is probably a dumb question, but can the oil go into the bloodstream and eventually become part of your body fat? Or if not, what happens to it? The more I think about it, the more I doubt it would work that way, but I don't know why. --Grace 05:46, 9 October 2006 (UTC)

A lot of the ingredients listed in moisturiser will be broken down and either excreted by the body (eg methylparaben), or used in metabolism (things like glycerol and stearic acid). it is possible for compounds to be stored in the fat layers of your body, but they are usually slowly broken down and excreted. Xcomradex 06:15, 9 October 2006 (UTC)

I'm talking about actual oil, though, like olive oil, which is sometimes used for massage. Surely you aren't saying that people watching their weight should avoid even external contact with fat? :) --Grace 09:20, 9 October 2006 (UTC)

The major component in olive oil, oleic acid, does travel through the skin. so at least in theory some of it wil contribute to yur overall energy uptake. however this is dependant on how much of it makes it past the outer dead layers of skin (which won't metabolise it) into the bloodstream. i'd say thats probably not a lot. Xcomradex 09:51, 9 October 2006 (UTC)

chemical engg

oxygen demand for prod of recombinant protein

production of recombinant protein by a genetically engineered strain of e.coli is proportional to cell growth .ammmonia is used as nitrogen source for aerobic respiration of glucose.the recombinant protein has an overall fortmula C H 1.55 O 0.31 N 0.25. THE YIELD OF BIOMASS FROM GLUCOSE IS MEASURED AT 0.48g/g.the yield of recombination of protein from glucose is about 20% (percent) that for cells..

1.how much ammmonia is required?

2.what is the oxygen demand?

3.if the biomass yield remains at 0.48g/g ,how much different are the ammonia and oxygen requirements for wild type e.coli unable to synthesize recombinant protein.......

Please read the text at the top of this page. Do your own homework. Simon A. 12:03, 9 October 2006 (UTC)

Please tell us what you understand in the text and what needs a particular help from us. -- DLL 17:01, 9 October 2006 (UTC)

Skies of the distant past/future

Let's say that I want to know what the skies looked like 50 million years ago. Is there a star chart program that I can use for this? Of course it will need to take into account proper motion, because the stars move a lot over millions of years. --Bowlhover 06:29, 9 October 2006 (UTC)

There's a number of free astronomy programs that do this kind of stuff; I use Celestia although there are certainly other (and maybe better) programs. Keep in mind, though, that errors accumulate over time; it's possible to get an idea of how the sky looked like to ancient Romans (being only about 2000 years in the past), but I would not really trust any such program to show anything meaningful for a date several million years in the past. Ferkelparade π 06:35, 9 October 2006 (UTC)

effect of growth on oxygen demand

the chemical reaction for conversion of ethanol to acetic acid (C2H4O2) is

C2H6O + O2------> C2H4O2+H20

Acetic acid produced during growth of Acetobactor aceti, which has the composition C H 1.8 O 0.5 N 0.2; biomass yields from substrate is 0.14g/g. Product yield from substrate is 0.92g/g. Ammonia is used as nitrogen source. How does growth in this culture affect oxygen demand for acetic acid production???

I DON'T MEAN TO BE RUDE, BUT DON'T WRITE IN CAPITALS, PLEASE. Aaadddaaammm 08:41, 9 October 2006 (UTC)

Thanks for removing the caps, but please also sign your comments by adding four tildes. And do your own homework. Simon A. 12:02, 9 October 2006 (UTC)

It's perfectly fine to ask for homework help here. It is not, however, perfectly fine to dismiss a question with the rude "do your own homework". That sort of rudeness at the reference desk really should stop. If someone's sole contribution to an answer is "do your own homework", I would suggest either silence, or substituting "If you need help with a specific part or concept of your homework, feel free to ask, but please do not post entire homework questions and expect us to give you the answers."- Nunh-huh 12:10, 9 October 2006 (UTC)

I agree. Since this is the Science desk, we should have a proper calibrated "Scale of Rudeness", going from 1 to 5, with standardized rudeness templates. 'Very Rude' (5) will be reserved for those who copy their homework assignment directly, and don't sign. 'Slightly Rude' (1) is for those who don't use the search box first. --Zeizmic 13:18, 9 October 2006 (UTC)

i need help

hi im a student doing a national diplomea of allpied sciences and i have been looking for an atricle everywhere and just can find it its called 'a mind to crime' by Anne Moir and David Jessel. i would greatly apprectiate it if you could provide any revelant info.

thank you very much -demoness_althea66611:33, 9 October 2006 (UTC)

Anybody ever told you about Google Scholar. I just typed in "a mind to crime Anne Moir David Jessel", and it immediatly told me that this is not an article, but a book (Signet, 1995). See here: ISBN 071813768X Simon A. 11:54, 9 October 2006 (UTC)

http://www.amazon.com/Mind-Crime-Moir/dp/0451196295/sr=8-1/qid=1160394637/ref=pd_bbs_1/104-8179265-6067933?ie=UTF8&s=books. ISBN 0451196295. Click on the ISBN link to look for sources. Presumably you can ask your local library to obtain it through interlibrary loan. - Nunh-huh 11:52, 9 October 2006 (UTC)

Underground nuclear tests

From what I've read about today's test by North Korea, it was tested underground. So, basically, I'm wondering how they do this underground. Do they have a really big cave that it's done in or what? Do we have an article on it that I didn't see linked at the nuclear testing article? Dismas| 12:49, 9 October 2006 (UTC)

They said it was in a mine (now abandoned). The difficult thing would be to seal it before the explosion, so it doesn't leak. --Zeizmic 13:13, 9 October 2006 (UTC)

Of course now it's abondoned. But Kim Jong Il stuffed babies in around the bomb to see the effects. — X (SUPERDESK|Help me improve)

That's not so hard, just use a manhole cover... but don't aim it at the ISS! --Jmeden2000 14:37, 9 October 2006 (UTC)

I think in general they just drill a hole, lower it in, and plug the hole, but they could also use old mineshafts. I think most caves might not be in a suitable type of rock. Misplaced Pages could do with more information if anyone has it.--Shantavira 13:15, 9 October 2006 (UTC)

It can vary a lot depending on the purpose for the test. But usually you dig a big hole, drop a bomb into it, and cover the hole. You can use old mines or whatever as well. The most important factors are the type of rock you are detonating it in and taking care that even if the bomb goes over the maximum predicted yield it won't vent. Other issues are whether or not the seismic activity will affect nearby people and wildlife but usually that sort of thing is set to the wayside, especially with small bombs. I imagine they also take into account whether or not there is water running through the area (the rock inside the test area will become quite hot and radioactive). One could create an article on it though personally I find the subject pretty boring — the technical issues are predictable and fairly banal. --Fastfission 14:59, 9 October 2006 (UTC)

Decoupling may also be a factor. You don't necessarily want all the evolved energy going into seismic activity lest everyone else know exactly how big a bang you produced, so you may excavate a larger cavity than you would need merely to hold the nuke's phsyical volume.

Atlant 17:20, 9 October 2006 (UTC)

News reports in Korea have said that a horizontal mineshaft is thought to have been used instead of a vertical one. --Kjoonlee 18:50, 9 October 2006 (UTC)

It was done under a 360-metre high hill/mountain. --Kjoonlee 18:53, 9 October 2006 (UTC)

Thanks for the responses, everyone! Although, in the case of N. Korea, I would think that they would want as much of the energy as possible to go into seismic activity. It makes for better advertising for themselves if they intend to sell the technology to someone else. Thanks again, Dismas| 21:48, 9 October 2006 (UTC)

I agree. Most of the effect they'll get out of a nuke is rhetorical or political; there is little reason for them to want to make their tests look smaller than they are. --Fastfission 00:44, 10 October 2006 (UTC)

That brings into play a new skill: making the bomb appear bigger seismically than it actually is. Everything I've read in the past few years was about tricks to obscure the test. The near-surface location is good, packing with tons of old munitions would add to the effect. It's not hard to get an M4 explosion. Wouldn't it be funny if it wasn't nuclear at all? --Zeizmic 17:14, 10 October 2006 (UTC)

That's why the Americans (and, I think, the Russians) have various detectors to detect leaks of radioactive materials which would have been given off by the blast. . If the Americans still had their Velas, they could have found the site and nature of the blast precisely (the ones which found the Gamma ray bursts which America mistook for Soviet nuke tests on the dark side of the moon) by detecting the gamma rays and EM pulse from the blast. Laïka 17:15, 11 October 2006 (UTC)

Reduced salt area

Sometimes while going on a highway we see a sign saying "Reduced Salt Area". What does this mean?

In Korea, only old people drive on highways with reduced salt... --Jmeden2000 14:08, 9 October 2006 (UTC)

Maybe one of the scientists assigned to the project has access to Wiki...

In seriousness, a quick google returns that a 'reduced salt area' is one where salt used to deice roadways is reduced or eliminated due to conservation concerns. --Jmeden2000 14:32, 9 October 2006 (UTC)

Not just conservation concerns. Watershed areas are often marked this way to limit the amount of sodium that ends up in the human drinking water supplies.

Atlant 17:23, 9 October 2006 (UTC)

That may be true for some areas, but most road salt used in the US is actually calcium chloride, since its more effective than sodium chloride and much less harmful to the local ecology (but still not 100% safe). --Jmeden2000 18:48, 9 October 2006 (UTC)

Here in my part of New England, it's definitely good-ole sodium chloride, probably because it's cheaper. The usual "winter mix" is sand and NaCl. On the other hand, I use CaCl₂ when I spread "salt" at all, primarily because I care about my plants and my concrete.

Atlant 00:39, 10 October 2006 (UTC)

its CaCl₂ of course, which is why it is more effective mole for mole than NaCl. Xcomradex 01:40, 10 October 2006 (UTC)

Correction accepted -- thanks!

Atlant 17:44, 10 October 2006 (UTC)

Gotta be careful with practical measurement of "effectiveness" though: to get a mole of ions from NaCl, you'll need 29 g of it, whereas you'll need 37 g if you use CaCl₂. DMacks 17:58, 10 October 2006 (UTC)

true, but there are other reasons to be careful with "real-world" measurements too. dissolving NaCl in water gives neglible temperature change, however dissolving anhydrous CaCl₂ in water gives a whopping exothermic reaction (release of heat) as the Ca(H₂O)_n ions form. so in a simply weight for weight measure, i'd say calcium chloride still wins. Xcomradex 01:28, 11 October 2006 (UTC)

Refraction of light

Is the light sensible to changes of pressure? For example, the sound pressure, will affect in any way the direction of the light, even could be very little influence? —The preceding unsigned comment was added by 80.103.32.2 (talk • contribs) 30 September 2006.

According to List of indices of refraction, the answer is yes. --Allen 16:14, 9 October 2006 (UTC)

I agree. However, in most cases, the change due to temperature is larger, see e.g. twinkling. But I remember that in undergrad lab practice, we did an experiment, where one arm of a Fabry-Perot interfreometer is led though a glass cylinder. When the cylinder is being evacuated one can see the fringes move. A pretty complicated and imprecise way of building a barometer. Simon A. 17:16, 9 October 2006 (UTC)

narcotics

(1)is alcohol a narcotic. (2)is nicotine a narcotic. (3)is caffine a narcotic. i have spent 2 hours on the internet trying to figure this out and i cant. thank you kevin

No, no, and no. Narcotics are, by scientific definition, derived from opium. None of those are. Even under the slightly-looser US legal defition (which includes coca-derived drugs) they aren't included. -- Plutor  11:14, 10 October 2006 (UTC)

To be nitpicky, narcotics are not derived from opium, but work by binding to the opiate receptor. alteripse 23:05, 9 October 2006 (UTC)

I believe that that is actually the definition of opioids. From a cursory search and a quick read of our articles, it appears that narcotics are a subset of opioids. -- Plutor  11:14, 10 October 2006 (UTC)

In the early 20th century all known narcotics were derived from opium, but that definition is long obsolete. My point was that synthetic opioids are considered narcotics by doctors, pharmacologists, and US law enforcement people but many are not derived from opium in any direct way, but simply share the ability to bind and activate opioid receptors. The word narcotic is somewhat slippery. In a medical context opioids and narcotics are typically considered interchangeable terms. In a US law enforcement context, the term narcotic is sometimes used more widely for all controlled substances, a usage that makes doctors cringe. alteripse 15:27, 10 October 2006 (UTC)

They're all psychoactive drugs, though. From the article: "In the West, the most common by numbers of users are caffeine, alcohol, and nicotine, in that order." DirkvdM 08:22, 10 October 2006 (UTC)

Wood Integrity

What is the integrity of pine wood? I would like to know the exact formulas so that I can use them for a medival seige engine.-- Meteshjj _{We come from the land} 20:55, 9 October 2006 (UTC)

  http://en.wikipedia.org/Fluoroscopy

  http://en.wikipedia.org/X-ray_machine#Security

  http://en.wikipedia.org/X-rays#See_also