Wikipedia:Reference desk/Archives/Science/2007 November 14

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November 14

What is a Dye Front?

I'm working on a PCR and I need to divide the distance of the bands that I have by the Dye Front, but our teacher never explained what this looks like. Can someone give an explanation or a diagram? Thanks. M@$+@ Ju ~ ♠ 00:29, 14 November 2007 (UTC)

It is the front edge of the dye as it travels across the gel. this page has a good picture with notation. If you can't see the dye front, it may have left the gel - which means you can't do analysis on it. -- kainaw™ 03:32, 14 November 2007 (UTC)

Thanks very much! M@$+@ Ju ~ ♠ 03:58, 14 November 2007 (UTC)

labrador coat

Is it normal for a labrador puppy to have a thickest fur along its "back"? (My dog-related English speaking is not the best, I hope you understand it anyway). Thanks in advance. 217.129.241.186 00:30, 14 November 2007 (UTC)

My girlfriend worked a couple years in the kennels of a large guide dog school that uses labradors almost exclusively, so she’s something of an expert on labs. According to her, yes, it’s normal. She also says that a lab’s coat changes substantially during its first year (it becomes coarser, sometimes wavier, and is two layers), so what a puppy’s fur looks like is a lot different from what it will look like as an adult. MrRedact 16:41, 14 November 2007 (UTC)

Our Lab/Retriever has much coarser hair down her back than elsewhere - I think it's typical of the breed. I somehow got the idea that it was an adaptation for swimming since the soft fur is what ends up getting wet and the coarse fur stays pretty much above water...but I can't imagine why that's an advantage! I have a book about labs at home - I'll see what it says. SteveBaker 18:19, 14 November 2007 (UTC)

My girlfriend confirms this idea. The soft, downy, oily "undercoat" supposedly keeps the dog warm and dry while swimming. The course, hard, dense "guard coat" is what's mainly on their back. MrRedact 03:42, 16 November 2007 (UTC)

Chemtrail Crazies, why is the bandwagon so big?

In my opinion the whole chemtrail phenomenon is a load of bollox. From what I've seen from online research is that those who believe in chemtrails piece together unrelated elements onto a big illogical ball of *cough*. I don't know of anyone on MCAGCC 29 Palms running around with black lung desise and their hedaches are from working with the Marine Corps or PTSD. What I want to know is how people hear these illogical reffrences to contrails being poison and then they fall for it the second they hear about it? Is it that people in general are just that gullible or the bandwagon effect at it's best, because thats all I can think of. This may seem like a nonsensical rant but I have a friend who claims the government is out to get us all and everyone seems to believe him when he mentions chemtrails. —Preceding unsigned comment added by 71.102.37.149 (talk) 01:52, 14 November 2007 (UTC)

Perhaps the chemtrails page can help you. Delmlsfan 02:27, 14 November 2007 (UTC)

(ec) This comic may provide some insight. I agree that the chemtrails stuff is one of the dumbest conspiracy theories around (on par with the "we never landed on the moon" thing). I can't give you any kind of definite explanation, but I do have some ideas about this kind of behavior. I think the whole thing has to do with Occam's razor. This tells us that a good strategy for finding the best explanation for some observation is to pick the simplest explanation that fits the facts. While this usually works, it does leave the person using this strategy very exploitable (and the human mind is shaped by eons of lying and exploitation). For instance, if my best friend is sleeping with my wife, all he has to do to stop me from figuring it out, is make sure that all clues I might find have a simpler explanation than him sleeping with my wife. Humans seem to have evolved an ability to second guess Occam's razor (which may actually be what we call paranoia) in order to save ourselves from being exploited this way. Part of this happens when an explanation that is more complex involves someone benefiting from us using Occam's razor. Once I realize that there is an alternative hypothesis where my best friend wants me to accept the simplest explanation, that hypothesis gets a lot of attention, and I reject Occam's razor.

I think this is the mechanism that generates conspiracy theories. Al-Qaeda explains 9-11 without leaving anything open. The Apollo program is a perfect, flawless explanation for the moonlanding footage. All the simplest possible explanations work perfectly. Yet the suggestion that somebody wants us to believe the easiest explanation seems impossible to reject. We are so tempted by these theories, because if we weren't we'd be easy to take advantage of. And then there's the confirmation bias. Once the paranoia kicks in, subtlety seems to go out the window. All we're concerned with is finding confirmation, rather than verifying the hypothesis. I'm not sure how to explain that, but I think it has something to do with defense mechanisms lacking the subtlety of everyday mechanisms, since they're only activated situations that warrant defense. risk 02:52, 14 November 2007 (UTC)

Well, there there are a number of reasons why people believe weird things like "chemtrails":

• People don't like to believe that they are easily fooled. So, when they think that they've seen through a "trick" or "conspiracy" it makes them feel smart. Or, if they're being told that they're being tricked or fooled, they may prefer to accept a belief that makes them feel more clever than the people they believe are attempting to trick them. The problem is, they can fool themselves this way, and after that admitting that they have made a mistake by believing foolish claims is even worse than saying that they used to be tricked by someone quite clever.
• People like to feel that they are special. This is related to the previous item. Part of the reason why people believe some weird things is that it makes them feel like one of the "brave few", or some such thing, in that they have some special knowledge, power, purpose, or experience that most others do not have.
• People don't like things they don't understand. Things like vapor trails and epidemiology are difficult because they require an understanding of science, however "planes spread sick juice" is simple. This leads me to the next point.
• It's easy to make claims that are hard to refute, even when those claims are entirely false. Some people tend to accept any claim that is not easily disproved if they like it, and thus fall into the trap of believing things simply because they don't understand why it's probably wrong. For example, "you're an adulterer" is an easy claim to make, but can be impossible to refute even if 100% false.
• People prefer beliefs that reinforce their worldview. If they are the kind of people that want to believe that the government is evil, then "chemtrails" or "9/11 was an inside job" is an appealing idea to them. This appeal becomes more important to them than evidence for or against those ideas. You see this in debates where you show evidence against the conspiracy you're discussing, and rather than show evidence for their conspiracy, they start talking about other conspiracies as though they are evidence that their conspiracy is true.
• People like the idea that someone powerful controls things. Thinking that things occur due to intelligent intervention allows people to believe that things don't just happen randomly, but that there is someone who has control of things, and thus they might also be able to control things. Random is scary, thus it's comforting to think that someone is in charge because then you can feel that things happen for a reason, and perhaps you can understand that reason.
• We tend to see patterns, even in entirely random events. This is related to the previous item, but it also means that people may see all sorts of data, and assume that they're related. They often see the "hits" that fit the "pattern" they're looking for, while ignoring most or all of the misses. Even in entirely random data, patterns will appear if you have enough data. The problem is that some people assume that "there are no coincidences" or "it's too coincidental to be random", therefore believe that any patterns must have some cause.

These reasons, among others, are why people tend to believe weird things for very poor reasons. You can take a look at most weird beliefs and see some combination of those factors at play. This is why we need to be skeptical of claims that are not supported by good science.

That being said, there really aren't that many people on the "chemtrail bandwagon", but the vocal few make it seem like it's a more popular belief than it really is. If you go to a place where people promote the idea, you'll see a disproportional percentage of the population that believe the idea. But start asking around randomly and you'll see how few people actually believe it. Hope that helps! -- HiEv 11:33, 14 November 2007 (UTC)

I would add:

• The truth is neither as interesting nor exciting as the fiction.
• People would love to find an 'easy way out' of whatever bothers them.

This is why things like water fuelled cars continue to be bandied about. It's interesting to hear that some guy with almost zero science training (they always have "almost zero science training") was able to figure this out when all of those smarty-pants scientists couldn't. People like to think that there is a quick fix for global warming just around the corner - and the only thing that's stopping it is 'big oil' suppressing the technology - that makes the whole problem "somebody elses fault".

It's really the same with this one: You're feeling tired and stressed out? Well no wonder! The government are spraying us with all of those tranquilizers! It's much easier to blame "them" than to start taking exercise and eating right. The truth, by comparison, is very boring. Water fuelled cars simply cannot work because of the first law of thermodynamics...jeez - what a boring answer! You scientists are just too dumb to figure out how to get around it like that guy in the garage did...Or: Contrails look different at different times because of weather conditions in the upper atmosphere - and besides, there are contrails all over the USA - how would the politicians doing this manage to avoid breathing them in themselves - and how would the enormous chemical industry needed to produce these chemicals manage to keep it so secret? All of those explanations are just tedious compared to a good old conspiracy theory.

SteveBaker 18:16, 14 November 2007 (UTC)

And I would add:

• People who believe there is something out there to get them live longer than those initially sceptical about any danger.

This said, it might not fill our lungs full of harmful chemicals but it might still cook us (or freeze us depending on the versions): "In 1999 the Intergovernmental Panel on Climate Change (IPCC) calculated that contrails from the world fleet of 12,000 civil airliners contribute as much to global warming as the CO2 their engines pour out as they burn jet fuel." from newscientist Oct 2002 and then "They may look benign, beautiful even, but by reflecting heat rising from the ground, contrails have a small but significant environmental impact." from Nature 2001. Keria 09:08, 15 November 2007 (UTC)

Er - isn't that the wrong way around? There was a story on TV about a guy who collected temperature readings across the whole of the USA on the few days after 9/11 when all air traffic in the USA was grounded. He found that temperatures were HIGHER in the absence of contrails because they are white and increased the earth's albedo - thereby reflecting more sunlight out into space. Certainly they'd also work to reflect heat back towards ground too - but that wasn't the finding. Temperatures were significantly cooler in the few days following 9/11. That's not to say that contrails are good for the environment - they are full of greenhouse gasses - so in the longer term, they are harmful. SteveBaker 13:50, 15 November 2007 (UTC)

Actually, as contradictory as it may seem, you're both kind of right. The fact is, contrails may either warm or cool the planet depending on various conditions including time of year, time of day, contrail optical depth, contrail coverage, and other things. Overall they currently appear to have a small net warming effect over time, but as air traffic increases so will the amount of warming they cause. See Contrail#Contrails and climate for starters and then "Contrails, Cirrus Trends, and Climate" for more detailed information. -- HiEv 15:26, 15 November 2007 (UTC)

Also, I disagree with the claim that "People who believe there is something out there to get them live longer than those initially sceptical about any danger." That is only the case for real threats, if you worry about nonexistent threats you will cause yourself stress and may waste energy or pass over opportunities in an attempt to avoid that "something dangerous" that doesn't exist. People should find a good balance in their skepticism, and rely on scientific consensus for complex issues they are unfamiliar with. Science may be wrong sometimes, but it's right far more often than uninformed opinion is, and science corrects itself over time. -- HiEv 22:03, 15 November 2007 (UTC)

Polystyrene cups

What are the effects from drinking hot beverages out of Polystyrene cups? Zain Ebrahim 09:13, 14 November 2007 (UTC)

Could you please explain what you mean by the question? Do you mean the effects on the person drinking from the cups or the environmental impact from the practice of using these cups?

In the first case, I would have thought there was no difference to the person drinking whether they were using a polystyrene cup or a ceramic one. Polystyrene is generally inert at the temperatures it would be subjected to by this use (if it melted due to the heat or reacted with the fluid then it would not be a suitable material for that use).

The environmental effect on the other hand is more serious, recycling of plastic cups is very limited at best and due to the fact that they are so inert, they sit in landfill sites for hundreds of years and biodegrade incredibly slowly (if at all). Producing plastic cups utilises precious hydrocarbons which could (arguably) be put to better uses than disposable cups and once they are landfilled or incinerated, the hydrocarbons are gone.

There are also several different types of polystyrene cups; the rigid plastic ones you commonly get by water coolers and the foamy (expanded polystyrene) ones hot drinks come in. I assume you mean the latter?:GaryReggae 12:47, 14 November 2007 (UTC)

On the other hand, polystyrene undergoes depolymerization pretty easily. (Note - we need a separate page on depolymerization). So it can be recycled into styrene monomer and reused. Options such as wax-covered paper cups are not nearly so recyclable. Delmlsfan 13:10, 14 November 2007 (UTC)

The critical thing with plastics is not whether they are "recyclable" - it's whether they are "recycled". It's no use having a substance that's easy to recycle only to find that people toss them into landfill anyway. That's the problem with plastic cups of all kinds - they are very rarely collected up and sent to the special recycling center that can turn them back into something useful. Paper cups are not recyclable - but at least when you toss them away, they behave much like a pile of leaves would - and decay down to normal soil nutrients in a matter of months.

Thanks a lot. I was referring to the effects on the person drinking from the cups. And yes, I meant the expanded polystyrene ones. Zain Ebrahim 13:38, 14 November 2007 (UTC)

The polystyrene is pretty inert - it's not going to harm you - the only thing that might be a problem is if the manufacturers use some kind of mold-release agent to make it easier to get the cups out of the injection molding machine. But I seriously doubt they'd use anything problematic. SteveBaker 16:57, 14 November 2007 (UTC)

chemicel contents of ferro titanium

i would like to know the chemical contents of ferro titanium.if the compound has silica 3.64%,iron (fe2o3) 35.25%,titanium(tio2) 48%,mangansese 2.55%,tungsten(w)6.09%,molybdenum 2%,carbon 0.79%,alumina 1.93% and its bulk density is 2.476% what is this material called. —Preceding unsigned comment added by Sammy 203 (talk • contribs) 10:03, 14 November 2007 (UTC)

Help on the Antlion

Please help?

I'd like to know how to go about answering the below mentioned challenge copy 1 vs copy 2 presented to 3-12 year olds

Copy 1.I also challenge you to find a sticky substance in an antlions hole. The antlion is the larvae. The struggles of the ant to get out of the hole cause the dry sand to slide down trapping the ant. The antlion flicks sand up from below with it's pincers until the ant is within reach and it can grab the ant. Anything sticky would cause the sand granules to stick together making the antlions hole useless.

Copy 2. The Antlion Antlions think ants are so delicious, they spend their whole lives building sneaky traps in dry sunny soil for ants to fall into. They even live in these traps - and can dig one in just 15 minutes! They then prepare a gooey, sticky substance called Larvae, and wait for some unlucky ant to fall in! When the gooey Larvae traps the ants in the hole the antlion get very happy and say "yummy, a fine breakfast is served!"

Any help in this regard would be much appreciated

Confused!÷ —Preceding unsigned comment added by 196.36.13.113 (talk) 13:51, 14 November 2007 (UTC)

I can't make heads or tails of this. The whole thing is in non-standard English and makes little sense. Where did it come from? There is nothing sticky in the hole, especially not the larva (larvae is plural) which is the ant lion itself. They don't spend their whole lives catching ants; they only do that as larvae. See Antlion. --Milkbreath 14:55, 14 November 2007 (UTC)

Plasma rockets

If the rocket shoots out plasma instead of fire, will it go faster? 64.236.121.129 18:04, 14 November 2007 (UTC)

Thrust is not dependent on "fire" versus "plasma", but rather the mass and velocity of the expelled material. — Lomn 18:45, 14 November 2007 (UTC)

Plasma would come out faster I think since it's hotter and it's trying to escape to an area of lower pressure. 64.236.121.129 19:59, 14 November 2007 (UTC)

Fire is plasma, you will find many ions in a flame. Graeme Bartlett 20:12, 14 November 2007 (UTC)

I seem to recall a physics teacher I had say that fire was NOT plasma. He could be wrong, but I trust him over a random internet guy. But confirmation on this would be appreciated. 64.236.121.129 15:06, 15 November 2007 (UTC)

Neither criteria you mention (heat, pressure) is meaningful. Heat does not affect mass or velocity, and high-to-low pressure is a function of all rockets. A more useful consideration is the combustion characteristics of your fuels: what provides the most thrust per fuel mass? What byproducts are acceptably non-toxic? What fuels are feasible to store and handle? These are the sort of concerns rocket engineers have. — Lomn 20:38, 14 November 2007 (UTC)

You don't know that heat creates high pressure? You don't know that? The hotter the medium, the greater the pressure. The greater the pressure, the faster the medium will move between the area of high pressure and low pressure. Btw, you contradicted yourself. You said pressure is not meaningful, then you said pressure is a function of all rockets, which means that pressure is certainly meaningful. You are contradicting yourself. 64.236.121.129 15:06, 15 November 2007 (UTC)

I was unclear. I intended to make it clear that "pressure", while essential to the operation of rocketry, has no relevance to a comparison of "fire" versus "plasma", as it is not dependent on those terms. Consequently, it's not meaningful to your original question.

It should also be noted that, in any event, peak thrust isn't terribly relevant to rocketry once you can actually lift off. Rather, it's far better to sustain acceleration for as long as possible, due to acceleration's second-order relationship with position. — Lomn 19:10, 15 November 2007 (UTC)

Just a guess: plasma is an electrically neutral collection of charged particles. You would have to separate the charges and accelerate them out of the rocket. IT seems that since the energy of the escaping particle depends on the variable electrical field and not the fixed chemical energy of combustion, the velocity could be faster. You would have to alternate charges being expelled. —Preceding unsigned comment added by DHeyward (talk • contribs) 06:15, 15 November 2007 (UTC)

Plasma rocket engines are in the works. I can't explain all of the physics behind it, but I saw the someone talking about it on tv so I think that qualifies me to answer your question. From what I understand this particular engine can't generate the thrust needed to get into orbit, but once it is in space its the most fuel efficient way to travel. So I think it can go faster over the long run, with a lower acceleration over a much longer time frame. Man It's So Loud In Here 16:59, 15 November 2007 (UTC)

Gold Detecting

Would gold show up on a metal detector? What kinds of metals show up? —Preceding unsigned comment added by 209.203.103.2 (talk) 18:24, 14 November 2007 (UTC)

Yes. See prospecting and metal detector.--Shantavira|^{feed me} 18:31, 14 November 2007 (UTC)

Our article about eddy currents may interest you.

Atlant 13:29, 15 November 2007 (UTC)

Is it possible for gold to come grow back (I know its not like a tree) but be created again from the place it was taken. If the same elements that created it the first time could create it again, or once it is taken and the place picked dry gold remains gone from that place forever?

Gold is an element, so it can't be created on Earth in useful amounts. Only stars can create gold in large amounts. So once the gold in the Earth is used up, there will never be any more. However, it is possible that there is lots more of it buried deeper inside the Earth, and this could slowly rise to the surface mixed with molten rock (magma), and be deposited on the surface by volcanoes. So, the gold that you collect could be replaced over many thousands or millions of years, but not likely in your lifetime. --Heron (talk) 18:19, 17 November 2007 (UTC)

I had never heard of stars creating gold before, that is very interesting. Just curious, how does that work, where does the gold go?

See stellar nucleosynthesis and Nucleosynthesis#Explosive_nucleosynthesis. The big bang left us with a lot of hydrogen, some helium, and very little else. Essentially all the heavier elements are created either by nuclear fusion (for the lighter ones) or supernova explosions (for the heavier ones, including gold). These explosions conveniently distribute the elements throughout the universe. That's why only younger stars and star systems contain significant amounts of heavier elements - see Metallicity (keep in mind that for astronomers all elements but hydrogen and helium are "metals"). --Stephan Schulz (talk) 16:39, 19 November 2007 (UTC)

Dried Banana Chips

Do dried banana chips still contain high level of potassium similar to fresh bananas?84.66.175.242 19:23, 14 November 2007 (UTC)

Speaking out of pure speculation, I would expect the majority of the potassium to go with the water (i.e, out of the bananas) during the drying process, being that potassium ions, K⁺, dissolve very well in water. shoy (^words _words) 19:59, 14 November 2007 (UTC)

When banana is dried evaporation is used. Only water and volatile substances leave it. Potassium is not volatile at the low temperatures used, so it stays in the banana. But be aware some dried banana has sugar and oil added, so it may not be so healthy as you think. Graeme Bartlett 20:05, 14 November 2007 (UTC)

Why don't they make bullets out of steel instead of lead/tungstun?

What advantages does lead have over steel bullets? 64.236.121.129 20:01, 14 November 2007 (UTC)

Off the top of my head, bullets are swaged when fired. This means softer metal is better. If the bullets were as hard as the barrel, I imagine the barrels wouldn't last very long. Friday (talk) 20:03, 14 November 2007 (UTC)

Yea but, if they were made of steel, you could shoot into water with them. I saw on Myth Busters, they fired bullets into water to see if water was "bullet proof", and the bullets fired from high powered rifles had a tendency to shatter when they hit the water. If they were made out of steel, they wouldn't shatter. 64.236.121.129 20:08, 14 November 2007 (UTC)

Tungsten is not soft, however like lead it is dense, so it will carry more kinetic energy for a given velocity and size. This means it will travel further through air before slowing down. Graeme Bartlett 20:11, 14 November 2007 (UTC)

Some bullets are meant to expand on impact, some are not. However it's possible when hitting something like water than even a full metal jacket bullet might come apart. I imagine this would happen more with smaller ones than bigger ones, but I'm just speculating. Bullets are designed for traveling through air rather than water. You might want something less bullet-like if you're intending to shoot through water. Friday (talk) 20:13, 14 November 2007 (UTC)

Yea, full metal jackets were used, and they shattered on the water. I think steel bullets would have greater armor penetration than lead. The tungsten sounds promising, but I read on the tungsten page that steel with small amounts of tungsten greatly increases its strength. So I think tungsten/steel bullets would be best. Yea bullets are designed at shooting through the air, but if you are trying to kill someone under water, it would be best if your gun's bullets can penetrate that water. 64.236.121.129 20:19, 14 November 2007 (UTC)

Even if the bullet stays together, I can't imagine you'd get much penetration. Water is dense. It's probably not as bad as shooting into sand, but it's not going to be easy to get through it. Friday (talk) 20:24, 14 November 2007 (UTC)

Yea, water is dense, but if the bullet can stay together, it means that at higher velocities, you will indeed get greater penetration. This contrasts with the fact that at higher velocities, a lead bullet will simply be more likely to shatter, which ironically means, a handgun has more penetration into water than a machine gun. 64.236.121.129 20:29, 14 November 2007 (UTC)

Even the handgun bullet doesn't penetrate very well through water. Are you imagining some military application? I can't think of why you'd want your gun to be able to shoot someone underwater. Wait til they come up, and shoot them then. Or, if they're in a submarine, they have torpedoes for that. Friday (talk) 20:33, 14 November 2007 (UTC)

I didn't say handgun bullets penetrate very well through water did I? I said handguns ironically penetrate through water better than high powered rifles because the bullet doesn't shatter. You are arguing strawmen, please don't do that, it's annoying. Yes, I am imagining a military application. I'm talking about guns and bullets, DUH! What application would we be using this for? Lol. You shoot at someone in the water to KILL them! DUH!!! A gun that can shoot at targets in the water AND the air is superior to a gun that is limited to only targets in the air. You can't figure that out? Lol. 64.236.121.129 21:41, 14 November 2007 (UTC)

Please remain civil and do not snap at people trying to answer your questions. Using terms like "duh" and "lol" are not helpful, nor are ad hominem attacks. This is a discussion, not a pure Q&A, so deviations from your original question, which mentioned NOTHING about water, are no more "strawmen" than your sidetracking to the topic of shooting into water is. Thank you.

Not exactly bullets, but they use steel shot in shotguns for waterfowl. The lead shot was poisoning the wetlands. The shot has a sleeve around it to keep it from wrecking the barrel. It doesn't hit as hard or go as far, but who wants lead in their duck dinner? --Milkbreath 20:24, 14 November 2007 (UTC)

Wait that makes no sense dude. Steel should hit harder than lead. 64.236.121.129 20:29, 14 November 2007 (UTC)

No, lead is denser. Steel is harder but when you're looking at retained velocity of the shot, density helps. Friday (talk) 20:31, 14 November 2007 (UTC)

No, mass helps. Newton's 2nd law. Hmm, I do agree that lead would retain velocity better than steel. But I think a steel/tungsten alloy would be best, as is indicated in the tungsten article. 64.236.121.129 21:41, 14 November 2007 (UTC)

For a bullet of a given size, density is effectively mass. A lead bullet masses more than a steel bullet because lead is denser than steel. — Lomn 22:07, 14 November 2007 (UTC)

You are stating information I am already aware of. Please do not state information I am already aware of. State information that I am not aware of. 64.236.121.129 15:07, 15 November 2007 (UTC)

Please remain civil and do not snap at people trying to answer your questions. Thank you.

Supposing steel is superior to lead for firing into water -- why do you want to fire into water? That's a really really really specific consideration with no practical relevance that I can see. Even if you want to shoot a guy who's underwater, doesn't he have to surface? Waiting to shoot him then (with a standard bullet) not only solves the problem of bullet composition but also energy dissipation, aiming despite refraction, and a host of other things. Ultimately, the answer to this "why don't we change..." is the same as several others -- it's a solution in search of a problem.

(ec) I see Friday has raised the same question above. — Lomn 20:34, 14 November 2007 (UTC)

You can't figure out that a gun that can shoot at targets in both the water and the air is better than a gun that can shoot at targets only in the air? You can't figure that out? 64.236.121.129 21:41, 14 November 2007 (UTC)

Please remain civil and do not snap at people trying to answer your questions. Thank you.

Again, it's a solution in search of a problem. BTW the people here are trying to be helpful and answer your questions. There's no need to get testy. It's less obvious that a shooting-through-water gun is useful than a shooting-through-air gun. You still need to be able to see your target and aim at it, for example. Water makes this harder. Friday (talk) 21:45, 14 November 2007 (UTC)

No, I already stated the problem, shooting into the water. I didn't ask you to debate if shooting into the water is a serious problem or not, or if you can't see your enemy in the water, or if your enemy can breath underwater or not. I didn't ask any of that. I originally asked why we don't use steel bullets, and now I'm wondering why we don't use steel/tungsten alloy bullets. I'm not interested in your speculation regarding shooting people in the water. Please stay on topic. Thanks in advance. 64.236.121.129 15:12, 15 November 2007 (UTC)

Please remain civil and do not snap at people trying to answer your questions. Thank you.

BTW, the article sucks but there are Spearguns meant to shoot through water. But, it's quite different than a bullet. Friday (talk) 20:35, 14 November 2007 (UTC)

Yea but a speargun isn't that good at killing targets in the air! Versatility is always better than a gun with limitations. 64.236.121.129 21:41, 14 November 2007 (UTC)

Shooting through walls, for example, is arguably even more useful than shooting through water, depending on the application (in some applications, excessive penetration is specifically not wanted.) Mass of the projectile (as well as hardness) generally help penetration- but it means less ammo that an individual is able to carry. Also note that copper-jacketed lead bullets are cheap to produce. Do you want ammo that penetrates more, if it's significantly more expensive? Like most practical questions, it's about making trade-offs. Friday (talk) 21:52, 14 November 2007 (UTC)

(ec) And so by your argument everyone should be driving SUV's, or even better, tanks around, just in case it needs to go off road into the mud or cross trenches, even though all you do is dropping the kids to and from school and grocery runs? Can you think of actual military or civilian needs to be able to shoot guns in water? Why sacrifice capabilities for its usual purpose for some obscure, not commonly used purpose? --antilived^{T | C | G} 21:56, 14 November 2007 (UTC)

That's a poor analogy because you are comparing military to civilian use. I'm comparing military use with military use. A civilian doesn't need to cross trenches, or drive off road. Military units do. It's a silly analogy.

I can think of many reasons to shoot into water, but we aren't debating the usefulness of that. We are talking about why guns don't shoot steel/tungsten alloy bullets. Sacrifice what capabilities? Be specific. What capabilities will be sacrificed if we use steel/tungsten bullets? 64.236.121.129 15:19, 15 November 2007 (UTC)

Y'know, thinking this through, I realized that at no point has the OP submitted evidence that steel bullets would be preferable for shooting into water. With no evidence of my own, I would surmise that steel's hardness (relative to lead) would in fact make catastrophic fracturing even more likely than that of lead bullets, since shattering is a characteristic of hard things. Anyway, I think it's quite clear that Friday and I aren't idiots. If a gun/bullet system existed that fired at submerged targets just as well as at normal ones, with no meaningful disadvantages, it would be... nice? But let's face it -- there are disadvantages. Given that the last time soldiers were forced to fire rifles at submerged targets as a best-case option was... let's see... never, I'm quite confident in my opinion that this is a dead-end. Defending against frogmen is a possibility, but the concussive force of a small depth charge (that is, a hand grenade) works just as well and is already widely deployed. Our opinions are most certainly not the result of failing to imagine that a magic gun would be cool. — Lomn 22:04, 14 November 2007 (UTC)

True, I didn't submit evidence that steel bullets or even better, steel/tungsten bullets are good at shooting into water. So you can take that as my question. Would they? You obviously don't know, so you can abstain from answering that question. Also, questioning the reasoning behind shooting into the water is irrelevant. We aren't talking about whether it's important or not. I think it is, you don't. Who cares? That's not what we are talking about. That's not even a science question, it would be a military tactics question. So you are addressing points that don't even have to do with science. 64.236.121.129 15:24, 15 November 2007 (UTC)

Well, force comes from mass times acceleration (F=ma), and steel has about 70% the density of lead,[1] so for two bullets that are identical except the lead is replaced with steel, the steel bullet will pack about 70% the punch of the lead bullet (though the fact that it weighs less will cause it to have a bit more acceleration.) This is why depleted uranium, which is extremely dense, is used in some military ammunition. -- HiEv 04:47, 15 November 2007 (UTC)

You also might be interested in supercavitation. In the article it talks about a navy project to use supercavitaing bullets to destroy under water mines. The article also links at least two guns specifically designed to be used underwater. -- dcole 14:06, 15 November 2007 (UTC)

You have the right idea in theory, but there are several reasons why a 100% steel bullet is not a good idea. First, remember that the barrel of your weapon is likely steel as well, so the rifling grooves are not going to "bite" into the bullet as well as they would a lead or copper-jacketed one, since the grooves and the projectile are of about equal hardness. The bullet will be spun up somewhat, but not as much as is usually desirable. Along similar lines, the bullet will also wear on the grooves alot more, thus reducing their ability to bite. This is the reason you use a bronze brush when cleaning a weapon, and not a steel one... the steel brush will erode the inside of the barrel.

Now, that said, note that a common NATO bullet, the M995 Ball, uses a hard core (steel originally, tungsten now), surrounded by lead, and copper jacketed. This is the best of both worlds: soft outer parts for maximum effectiveness in the barrel with minimal erosion, followed by a very hard core which will penetrate body armor up to certain levels. Arakunem^Talk 15:25, 15 November 2007 (UTC)

What about steel/tungsten alloy bullets? 64.236.121.129 16:22, 15 November 2007 (UTC)

It's difficult for me to believe you're doing anything but trolling, when you ask questions and then apparently don't read the answers. As pointed out above, several times: all steel bullets would be hard on the barrel. Guns as commonly exist today wouldn't work well like that. You might want to do something other than forcing a bullet down an undersized rifled barrel if you want an all steel projectile. See swaging and rifling for relevant articles. And please, if you're honestly looking for answers, be a little more productive in how you interact with the people trying to provide you with useful information. Friday (talk) 16:26, 15 November 2007 (UTC)

What part of steel/TUNGSTEN ALLOY bullets was not clear? He addressed 100% steel bullets. I'm asking about steel/tungsten alloy bullets. 64.236.121.129 16:30, 15 November 2007 (UTC)

Steel is an alloy and frequently contains tungsten. So your question is not very meaningful. If you want to know why materials much harder than lead aren't good for bullets, we've told you. Do you have another question? Friday (talk) 16:34, 15 November 2007 (UTC)

Haha, you're mad. You are just fillibustering. Yes, I know steel is an alloy, but not all steel contains tungsten, and he was addressing 100% steel bullets, not steel alloyed with tungsten. My question is about steel/tungsten bullets. You're mad obviously, so why not just abstain from the discussion? You don't have to participate, or follow me around. It can be considered harrassment. 64.236.121.129 16:44, 15 November 2007 (UTC)

I will however answer, as I do see that I was not quite clear on something which (if someone didn't know this) would indicate that 64's followup was perfectly valid. Which is: a steel/tungsten alloy would be better than steel at the penetrating side of things, as tungsten is harder than normal steel, but the flipside would be that the projectile would be much harder on the barrel as a result, including getting less spin out of the rifling. This extra hardness is likely why the M995 ball now uses tungsten as the core over steel. You still need to jacket/coat it with a nice soft lead/copper coating though, so it doesnt rip your barrel up, and so it does get nice bite from the rifling. Arakunem^Talk 16:37, 15 November 2007 (UTC)

Ok what if you have a thin coating of copper or lead, surrounding steel/tungsten alloy? Wouldn't that solve the problem? 64.236.121.129 16:44, 15 November 2007 (UTC)

If it's thicker than the depth of the rifling grooves, then yes. This is essentially the M995 ball we're at now. I wish that article had a good cross-section.... *ponders adding one* :) Arakunem^Talk 16:47, 15 November 2007 (UTC)

Similar to current ammo that's already being used? Sure, I think that would work. Also, barrel wear concerns could be addressed by using a sabot- but this is probably only practical for larger-diameter rounds. Also, sabot ammo is complicated and presumably much more expensive to produce than standard ball ammo. Friday (talk) 16:49, 15 November 2007 (UTC)

Yep, the copper and lead basically act like the sabot, sans the discarding. They're just there to get the round out of the barrel. Soon as they hit the target though, the core goes through, leaving the copper/lead behind. So I guess it does eventually discard! :) —Preceding unsigned comment added by Arakunem (talk • contribs) 17:02, 15 November 2007 (UTC)

Mystery of the freezing water

A few years ago in a trip to Norway early one morning, my friends and I were about to get on the road with our car. The temperature was about 0 degrees celsius or maybe below, and we found that we'd left two glass bottles with some water in the car overnight. Picking up the (sealed) bottles for taking a sip, we saw the water freeze and turn into ice in just an instant. Can anyone please explain this? Gil_mo 21:25, 14 November 2007 (UTC)

Your water was supercooled. Picking it up jarred it and started nucleation. Friday (talk) 21:30, 14 November 2007 (UTC)

Prior to taking a sip, you may also have opened the bottle. This release of built-up pressure allowed the supercooled liquid to form some ordinary Ice-1 whereas, prior to being de-capped, the liquid hadn't yet cooled enough to form one of the more-exotic phases of water ice.

Levitating at the center of the world

There's a well in my backyard. It's lined with a material that makes it almost impervious to heat and pressure. (Pretty amazing stuff!) The well is so deep it actually runs straight through the center of the world and connects up both Antipodes. Yesterday my poor cat Mr. Cuddlypants accidently fell into the well. Am I safe to assume Mr. Cuddlypants is now levitating at the center of the world? Sappysap 22:04, 14 November 2007 (UTC)

Eventually, yes, due to atmospheric drag. Negate that and he'll cycle back and forth from endpoint to endpoint. — Lomn 22:14, 14 November 2007 (UTC)

Should I continue to throw food down the well for him? —Preceding unsigned comment added by Sappysap (talk • contribs) 22:43, 14 November 2007 (UTC)

If you throw food down and hit him, it will kill him. Of course, if there's any water levitating at the center of the well, your cat would have died when he hit it. If there isn't any water, what was the point of the well? — Daniel 22:45, 14 November 2007 (UTC)

What if there's water at the other end - i.e. the antipodal point is somewhere in the ocean? Man... --Kurt Shaped Box 22:53, 14 November 2007 (UTC)

The air at the center of the well (I’m assuming there’s just air in the well) is very dense. That means that the terminal velocity of food thrown down the well would be plenty slow enough to keep the food from killing Mr. Cuddlypants. But there’s no point in throwing food down the well, because he’s already dead from the compression. That’s assuming he didn’t get shredded from friction bouncing against the well liner here and there before the compression got to him. Or die of internal injuries due to all the bouncing around. One way or another, I’m afraid Mr. Cuddlypants is now frolicking with the Invisible Pink Unicorn (blessed be her holy hooves). MrRedact 00:03, 15 November 2007 (UTC)

It's true that there is no gravity at the center of the earth - so with air resistance, kitty will wind up there pretty soon (what with terminal velocity, etc) - but so will everything else that ever fell into the well. Rainwater, for example - so I'd expect there to be an nice section of the well that's full of water and leaves and all sorts of other crud. But maybe we can neglect that too - perhaps there is one of those cute little rustic roofs over each end of the well with a few thousand miles of rope coiled up and a bucket on the end. But I'm also wondering whether there actually would be air down there in the first place? I mean, think about this. With no gravity, any air that's not PRECISELY at the center of the well will be flung gently outwards by centrifugal force due to rotation of the earth. At some distance from the center, gravity and centrifugal force would cancel out - and we'd have normal air pressure from there on out. But I wonder if, in fact, there might be a fairly decent vacuum in the middle of the well? I've been working too long today - so I can't be bothered to figure it out - but I'm sure someone here will. SteveBaker 01:35, 15 November 2007 (UTC)

No, the density of the air in the center would be much greater than at the surface, not less. Just like with water in the ocean, the deeper you go, the greater the pressure, due to the weight of all the air or water above you. With air, the greater pressure (at thermal equilibrium – and remember that the sides of the well are perfectly insulating) corresponds to a greater density. The rate at which the density increases would decrease as you approach the center of the earth, due to the decreasing gravity, but the density itself would be monotonic increasing to the center. Both the rate of density increase and the centripetal force approach zero as you approach the center of the Earth, so I’m not sure off the top of my head if the peak air density would be precisely at the center or slightly above it, but whatever less density there would be at the precise center than at the peak would be very small. MrRedact 02:35, 15 November 2007 (UTC)

A few comments: (1) Except at the ends, the well is in fact full of liquid air. (2) That may be a good thing for your cat, considering that the Coriolis force will make him drag along the well wall as he falls (unless you live on the North or South Pole). He'll appreciate being slowed down. (3) Then again, maybe not: liquid air, being 20% oxygen, is a strong oxidant - explosive feline combustion could become an issue. --mglg_(talk) 03:53, 15 November 2007 (UTC)

There's no such thing as a centrifugal force, right?128.163.224.198 (talk) 23:19, 17 November 2007 (UTC)

With a name like "Mr. Cuddlypants", I suspect it isn't so much that he fell into the well, so much as he jumped. --Mdwyer 01:37, 15 November 2007 (UTC)

Perhaps he became suicidal when the court denied his petition to change his nmame to Mr. Bigglesworth.

Atlant 13:41, 15 November 2007 (UTC)

Thats a great question but considering the mass of the earth will be around any object placed at its center would it really float there in the midle (assuming no debris or water) or would it be attracted by one of the walls? Keria 08:41, 15 November 2007 (UTC)

No - actually there would be a teeny-tiny gravitational force pulling you into the exact center. It's only at the precise center of the earth that the gravity goes to zero - so away from the center there is a tiny amount of gravity. Imagine if you have your back to one side of the wall of the well which (let's say) is two meters in diameter. Behind you is almost a complete hemisphere of the earth - minus one meter. In front of you is a little more than a hemisphere of earth - plus one meter. So the gravitational forces of the two hemispheres ALMOST cancel out - but a one meter wide slice of the earth in front of you is pulling you gently forwards - away from the wall and towards the center of the well. In truth though, that would be an amazingly gentle force - I doubt you'd notice it. SteveBaker 13:41, 15 November 2007 (UTC)

He probably hasn't got there yet; the Earth is about 6000 km in radius. His average terminal velocity is going be pretty low, as the atmosphere would behave like a liquid; it could be lower than 20 m/s. As such, the fall may take him 3 or 4 days. Taking his overshoot into account and hence the harmonic oscillations, it could be up to a month before you could consider him to be stationary at the centre of the Earth. Laïka 14:21, 15 November 2007 (UTC)

Maybe it’s time to play with some actual numbers:

The barometric formula says that the density of the air in the well will equal the density of liquid air at a depth of only about 55km. So the air in the well is all liquid except for about the top 55km of gaseous air! That’s only a rough approximation though, mainly due to the ideal gas law becoming increasingly inaccurate as the density approaches that of liquid air.

I’ll assume Mr. Cuddlypants’ terminal velocity in air at the surface is roughly that of a skydiver in free fall, which is about 54 m/s. Given the equation for terminal velocity, and given that the density of liquid air is about 710 times greater than air at the surface, that means that Mr. Cuddlypants’ terminal velocity at about 55km down is already down to only about 2 m/s. It’s safe to say that Mr. Cuddlypants is nowhere near the center of the earth yet.

Assuming that the earth’s density is uniform (not a great assumption), the gravitational force inside the earth is proportional to the distance from the center of the earth. The radius of the earth is about 6371km. Combining that information with the equation for terminal velocity says that Mr. Cuddlypants' terminal velocity will be down to only 2 cm/s when he's still about 637 m from the center. Mr. Cuddlypants isn’t going to experience any oscillation around the center of the earth, or even overshoot the center of the earth. Rather, his position from the center of the earth will decrease exponentially with time. That is, his motion is overdamped.

Calculating the pressure of the air at the center of the earth would involve doing an integration that I’d have to think about. But the pressure is proportional to the density of the material above it. So given that the earth’s mean density is only about 6.3 times that of liquid air, and given that the pressure at the bottom of the earth’s mantle is about 1.4 Matm, we can estimate that the pressure of the air at the center of the earth is getting up close to 1 million atmospheres. So on the way down, Mr. Cuddlypants’ soft tissues will turn to pulp, his bones will be crushed, and his molecules will undergo all sorts of chemical reactions that wouldn’t normally occur if it weren’t for the extreme pressure. So it really doesn’t even make sense to talk about where Mr. Cuddlypants is, but only to talk about the statistical distribution of the locations of the atoms that used to be a part of Mr. Cuddlypants. Throwing cat food down the well is really a complete waste of cat food. MrRedact 21:14, 15 November 2007 (UTC)

Wonderful, simply wonderful! Oh well, then I guess a rescue mission is out of the question. RIP Cuddlypants. Thanks for a comprehensive answer! SteveBaker 04:47, 16 November 2007 (UTC)

Err, the problem is, if the well really is almost resistant to heat and pressure, the temperature and heat will not be much different from the surface. Thus, the liquid air may only be at the core. Oh, and since more than 70% of the surface of the world is overed with water, the ocean will probably start filling the center of the well, and global sea levels will plummet, but as the slightly increased heat in the well heats the water, you may have yourselves a geyser. Oh, and if the gravitational forces are strong enough or if the currents in the core or magma are strong enough, it may bend or even fracture the well. Oh "well". Hope this helps. Thanks. ~AH1^(TCU) 15:37, 17 November 2007 (UTC)

Err, the air in the well, which indeed is assumed to be at the same temperature throughout as at the surface, is liquid due to the pressure acting on it by the air above it. It’s not liquid due to heat – if you want to liquefy air by varying its temperature, you cool it down, not heat it up.

Oh, and since the volume of a 1m diameter well going through the earth is only 1.0x10⁷ m³, if it got filled with water it would cause the 3.6x10¹⁴ m² of the world that’s covered by water to lower by all of 28 nm. I would hardly call that a "plummet" of global sea levels, as it'd be vastly too small to measure.

If the well's antipodal point happened to be in the middle of an ocean, you could just increase the length of the well by only 0.001% to make the well stick up above the ocean's surface enough to prevent even the largest of waves from spilling into the well. It's a completely negligible increase in the extreme difficulty of building the well. MrRedact (talk) 17:40, 17 November 2007 (UTC)

Why do raw carrots taste like soap?

I've recently began eating raw carrots, peeled, they seem to leave a soapy aftertaste. I've tried fresh carrots from other store and they have the same soapy taste. Is this because of chemicals used by farmers, should I be worried? Or perhaps certain chemicals, fatty acids... gives the taste buds a similar sensation as when one smells a bar of soap? Thanks for any info! --Taktser 22:08, 14 November 2007 (UTC)

I don't get that taste, myself. This may be a stupid question but have you washed them? Friday (talk) 22:23, 14 November 2007 (UTC)

Well, if he/she peeled them him/herself, then washing isn't really a major issue. I don't taste anything soapy though I do think they have an odd texture and smell. It might be one of those things that some people are more sensitive to than others (i.e. like those people who really can't enjoy raw tomatos because they taste more acidic to them than to others). --24.147.86.187 23:02, 14 November 2007 (UTC)

I'm guessing the point of Friday's question was "did you wash them with soap? because then that's your problem, right there...". --Trovatore 01:54, 15 November 2007 (UTC)

I cannot answer your question, as raw carrots taste fine to me. But McDonalds fries taste, to me, distinctly of soap. Yughhh! I cannot eat them. I've never heard this from anyone else, so maybe things do taste different to different people.--Shantavira|^{feed me} 08:25, 15 November 2007 (UTC)

Are you thoroughly rinsing your peeler? 130.88.140.8 11:08, 15 November 2007 (UTC)

Yes, I washed them, then peeled them (washed the peeler as well), then washed them again (and my tap water tastes fine). It's only with raw carrots, if they're cooked/heated in any way they loose the "soapy" taste and become quite sweet. I guess it must be some sensitivity on my tongue then... --Taktser 13:11, 15 November 2007 (UTC)

I believe some people feel that cilantro tastes soapy, and it is in the same family as carrots, Apiaceae. Maybe there's a link there? -- JSBillings 17:55, 15 November 2007 (UTC)

Well, the vexed question remaining: Maybe your soap tastes of carrot? Is it orange, at least? Pallida Mors 22:18, 16 November 2007 (UTC)

Potassium/Rubidium-filled bullets?

How effective would bullets containing small pieces of metallic potassium or rubidium be against human targets? Would it be possible to seal small fragments of the pure alkali metal inside lead bullets which were designed to shatter upon penetration - with the end result being that the target/victim takes a round to the chest, then almost immediately begins to be incinerated from the inside out as the alkali metals react with his own bodily fluids...

I'm mainly thinking of the possible applications with regard to sniper rifles and near-certain one-shot kills. I'm aware that pure alkali metals are expensive. --Kurt Shaped Box 22:44, 14 November 2007 (UTC)

Sounds to me you'd get a similar result much more easily using a bullet containing an explosive charge, or one designed to explode on impact. Exxolon 23:34, 14 November 2007 (UTC)

As far as I know, the alkali metals have not been used in any significant way in warfare. What has been used is white phosphorus. On exposure to air it burns, brightly and with extreme heat. It can be used to generate screening smoke, and it is a potent incendiary agent (it can be used to start fires). More insidiously, it has also been used as an antipersonnel weapon. During both World Wars, white phosphorus shells, grenades, and rockets were used extensively. In more recent decades, the use of white phosphorus against personnel has been restricted by various chemical warfare treaties. (Incidentally, the same treaties would likely forbid the use of alkali metals in bullets intended for use against people.) TenOfAllTrades(talk) 01:10, 15 November 2007 (UTC)

Thanks for your answers guys. What I was really getting at, though was whether it would actually work from a purely technical standpoint - not so much the actual feasibility of using alkali metal rounds in standard warfare. I was thinking more along the lines of your archetypical Jackal-esque 'gentleman sniper' looking for a new, interesting, reputation-enhancing methods of carrying out a hit, rather than the soldier on the battlefield. --Kurt Shaped Box 01:52, 15 November 2007 (UTC)

Perhaps that's how Fatima Blush bought it? Between underwater bullets and alkali bullets, we all seem to be in a James Bond mood here.

Atlant 13:46, 15 November 2007 (UTC)

I recall that lead azide was at one point used in exploding bullets, although, it seems kind of unstable for that kind of application. As far as I know, exploding bullets are specifically banned by the Geneva Accords on Humane Weaponry (although we don't have a real article on that), although that wouldn't really matter your your gentleman sniper. -- dcole 14:17, 15 November 2007 (UTC)

Along the same lines, you might be interested in Georgi Markov, who was supposedly murdered by a ricin-filled pellet. (Delivered by an umbrella, though, not a gun.) -- 20:15, 16 November 2007 (UTC)

Sodium bicarb and ethanol turning black

What might react with baking soda to turn a solution of water and ethanol black? Solution probably also contains ethyl acetate, fusel oils and trace amounts of methanol. Lowerarchy 23:05, 14 November 2007 (UTC)

You don't seem to be getting anyone answering, so I'll take a wild ass guess at it. I seriously doubt the sodium bicarbonate, water or ethanol itself is turning black. However, sodium bicarbonate can act as a base (or an acid). Add to that "abnormal" effects on pH seen in mixtures of organic solvents and water, and it is possible you have a non-pH-neutral solution. There might be some acid/base catalyzed reactions occurring with trace contaminants in the solution. (The fusel oils, perhaps?) You only need a small amount of colored compound to give a very visible effect. That's my inexpert guess, anyway. It sounds like a bit of a witches brew. It can be hard for chemists to understand what is happening in simple reactions. When you have complex (and partially unspecified) mixtures, it becomes even more so. There are so many reactions and chains of reactions that can occur, it's hard to track them all down (especially if you're only seeing trace amounts of products - and you only need trace amounts to get strongly coloured solutions) . -- 20:09, 16 November 2007 (UTC)