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November 1

PETA video

In this video of trappers killing their fur-bearing animals, aren't the animals being either killed instantaneously or being knocked unconscious? It just seems to me much ado about nothing -- sort of like fooling people with statistics that they don't understand. Sure, it looks spooky to see these raccoons kicking a bit, but that happens after severing the carotids/trachea of a chicken, too? DRosenbach ^{(Talk | Contribs)} 01:30, 1 November 2010 (UTC)

Our article on the animal in the video is at Raccoon Dog. -- 119.31.126.67 (talk) 13:07, 1 November 2010 (UTC)

In a sense, the video is a purely objective demonstration. It's up to individuals to decide whether this activity is ethical or justifiable. In terms of scientific analysis, it is probable that the raccoon is capable of feeling pain; I think the consensus is that a quick blow to the head is among the less painful lethal techniques. See pain in animals for starters. As far as the movements - I can't tell from the videos whether we're seeing a reflex, rigor mortis, or conscious squirming - in my opinion, it is not possible to discern conclusively from these videos. Nimur (talk) 01:43, 1 November 2010 (UTC)

Just watched the first few seconds of the video. I saw one animal being struck five times over perhaps a five to ten second period. Obviously not "instantaneous." I certainly wouldn't enjoy it if i were the raccoon. HiLo48 (talk) 01:51, 1 November 2010 (UTC)

(edit conflict) (haven't watched the video btw)

PETA's position is:

"If anybody wonders 'what's this with all these reforms?', you can hear us clearly. Our goal is total animal liberation, and the day when everyone believes that animals are not ours to eat, not ours to wear, not ours to experiment [on], and not ours for entertainment or any other exploitive purpose."

according to co-founder Ingrid Newkirk.

How "well" they may be euthanized to harvest their fur does not change the fact that they are being raised in captivity and then killed solely to harvest their fur. Some consider that to be unethical, or feel a sense of empathy for the animals. Others do not. But the objection for some of those who do is not that they are being tortured to death (which presumably everyone would object to), but just that "we" are ill-using them for a clearly unnecessary and purely vanity-driven purpose. WikiDao ☯ (talk) 01:57, 1 November 2010 (UTC)

Just watched the video. I have no idea how anyone could not have a problem with that. What exactly is the point of your "question", DRosenbach? Could you please clarify exactly what it is you would like to know? Thank you. WikiDao ☯ (talk) 02:27, 1 November 2010 (UTC)

Why should he clarify his question? He states it very clearly. He wants to know if this video depicts cruelty on a still-conscious animal. I don't think there's a way to know, but personally it looks to me that the raccoon was completely 'out' after the first blow. If true, the video shows no more cruelty than a slaughterhouse, probably less cruelty than many types of fishing.

In any case, while they sometimes do good investigative work, their motives are not to educate, and I absolutely would not trust a video being distributed by PETA without third party verification. APL (talk) 03:30, 1 November 2010 (UTC)

Did you watch the entire video? If the animal was "out" after the first blow, how do you explain the squirming? Humans certainly don't move their limbs around frantically after being knocked out.

I think DRosenbach explained it in the question - personally I've seen a goat beheaded (also in China as it happens) - so it was definately dead - but it kept 'spasming' similar to what was seen in the video - we probably have an article on the phenonoma - but I don't know what it is called.Sf5xeplus (talk) 05:54, 1 November 2010 (UTC)

No. I'll admit that I only watched about half of it. Does something dramatically different happen in the second half? I don't have a reference handy, but I'm pretty sure that humans do sometimes twitch after crushing blows to the head. Hollywood doesn't portray it that way for reasons that should be obvious after watching the video. (Notable exception : "The Rock").

If you want to feel bad for those animals, feel bad that they grew up on a farm, probably in cages. Not because they died from a sudden blow to the head. APL (talk) 15:34, 1 November 2010 (UTC)

Also, in the middle of the video one person asks the cameraman, "are you recording?" He goes on to say, "make sure this video doesn't leak; that wouldn't be good for us." I highly suspect that, even in China, what these people are doing is illegal. --99.237.232.254 (talk) 05:44, 1 November 2010 (UTC)

Not necessarily. Farming animals is in many ways an unpleasant process. Anyone who's not a complete fool understands that it would be bad PR for the naive masses to be made to watch a heavily edited video of the most unpleasant aspects of your operation.

I imagine someone working in an entirely legal slaughterhouse for entirely delicious beef would have a similar reaction to a video camera. APL (talk) 15:34, 1 November 2010 (UTC)

DRosenbach, your error is attempting to apply logic to what is intended as a shock video. APL (talk) 03:33, 1 November 2010 (UTC)

• This question is asking for opinion ("seems to me it's much ado about nothing - is it?") and should be removed. (Note that my response above is the only one that even makes an attempt to link to an article or source that might be relevant, and even still does not answer the "question" because there is no way to answer the question "encyclopedically"). WikiDao ☯ (talk) 10:11, 1 November 2010 (UTC)

The question is clear and not opinion: "are the animals being either killed instantaneously or being knocked unconscious?" Yes or no? As illustration the OP refers to chickens. 92.24.189.164 (talk) 13:46, 1 November 2010 (UTC)

WikiDao -- please cool your jets. What constitutes animal cruelty itself is an opinion, so there's certainly many ways to spin my question. But my intent was not to create a windstorm of emotion (as perhaps you are suggesting I intended to do)...assuming one ascribes to a normative view of animal cruelty -- in that the killing of an animal is not inherently uncruel -- does this video depict cruelty at all, because it sure seems a lot more sensational than anything else. I didn't watch the entire video either (only the first 2/3) but it was quite boring and I just couldn't finish. The head/neck-banging of the first 2/3 doesn't seem cruel at all. DRosenbach ^{(Talk | Contribs)} 01:15, 2 November 2010 (UTC)

I'm fairly certain that the aim is to polarise opinion - ie those that are opposed will be appalled and some that were not opposed will become opposed, additionally, those that were blissfully ignorant may be appalled. It shouldn't come as a surprise that PETA characterise it as cruelty -since that's where they are coming from - so I doubt they post it for fun - but to attempt to bring what's happening into public view.

I won't comment on the cruelty or lack thereof, but will note that killing animals larger than birds is usually a two step process: first you stun them, then you kill them. Traditionally the stunning is done exactly as these Chinese guys are doing: you hit them on the head with something heavy. More modern techniques include the captive bolt pistol and electrocution. The killing is usually done be exsanguination, but these guys are doing it by inflicting massive head trauma. The style of blow they used in some cases, where they hold the animal upside down and whack it at the base of the skull, is often used in killing rabbits in one step. Having killed many things (in what I hope is a cruelty-minimizing way) I believe the animal has some brain function but nothing like its normal thoughts after a well-delivered first blow. --Sean 20:15, 1 November 2010 (UTC)

See rabbit punch. Googlemeister (talk) 13:16, 2 November 2010 (UTC)

In this case, as I noted above, there appeared to be five "first blows" right at the start of the video. Is this just evidence of incompetence? HiLo48 (talk) 20:53, 1 November 2010 (UTC)

I figured apathy; suggestive, though, of such action not being cruel as a rule. DRosenbach ^{(Talk | Contribs)} 01:59, 2 November 2010 (UTC)

I'm not sure if they have much choice - the first step, as noted above is to stun or knock out the animal - but because these animals are for fur, cutting the throat is not really an option (blood stains on fur, damage to the pelt etc) - so hitting it numerous times on the head seems a reasonable thing to do if selling pelts is something you do for a living. Probably less cruel than stunning it, then stripping the pelt and waiting for the animal to die of a massive stress related heart attack when it comes round and discovers it's got no skin anymore.. An unpleasent business alround - but I don't see that the killing of the animals was more cruel than any other obvious way of killing it. (Is there a better way?)

actually according to http://features.peta.org/ChineseFurFarms/ some are still alive when being skinned - as the video shows. It's a different video, and is about 100x worse than the first video posted - even the strong of stomach may not want to watch it.Sf5xeplus (talk) 08:00, 2 November 2010 (UTC)

I figure these guys just don't care, just like I don't care about a live oyster's opinion on sliding down my throat. I personally would care with these raccoon things, but Chinese slaughter operations are a rougher place, I suppose. --Sean 16:35, 2 November 2010 (UTC)

Also, exsanguination is important for meat quality, which is (perhaps!) not an issue here. --Sean 16:35, 2 November 2010 (UTC)

is HCl in 95% saturated salt solution still a strong acid?

I assume that a saturation limit exists for salt in water because at some point there aren't enough water molecules to separate the Na+ and Cl- ions, which are growing more acidic/basic for each other, respectively.

This makes me curious as to to acid-dissociation properties in highly saline water. Does the acidic species in solution change in highly salty water?

The pKa for HCl is given to be somewhere around -7, but hydronium is usually listed as -1.8 or something, but I assume the latter is for a dilute, distilled solution. I wonder if I can make a "more acidic hydronium species" by near-saturating the solution with neutral salts. So I have two questions:

1) Will Cl- be a stronger base in near-saturated salt solution 2) Will H3O+ be more acidic in near-saturated salt solution? Will Zundel cations and Eigen cations decompose in saturated salt solutions to form the more acidic "bare H3O+" species?

John Riemann Soong (talk) 02:09, 1 November 2010 (UTC)

Generally, the common ion effect is only a major issue in equilibrium situations. The dissociation of hydrogen chloride in water is highly extensive process. To put it bluntly, the chloride ion has such a terrible affinity for the hydrogen ion, I would doubt that you could get any discrete HCl molecules in a water solution regardless of how much you pump it full of chloride ions. --Jayron32 02:22, 1 November 2010 (UTC)

I still expect the HCl to dissolve more or less completely, but what I expect is for HCl's pKa to increase (to maybe -3) and for hydronium's pKa to decrease. Isn't hydronium pKa = HCl pKa in a solution of saturated 37% HCl? That's why as water evaporates, HCl gas evaporates from it as well right? So these are my hypotheses:

• As long as hydronium pKa > HCl pKa, you can dissolve more HCl in the water.
• If hydronium pKa < HCl pKa, then the protonated water will spontaneously reprotonate the chloride, forming HCl gas.
• I have noticed that concentrated HCl behaves a lot differently in reactions than dilute HCl, and not simply because the reaction rate increases, but because the acidic species seems to increase in strength.
• Dissolving NaCl (or perhaps some other neutral salt) in water decreases the pKa of hydronium because the hydronium has to compete with the salt for solvation stabilisation.
• At the same time the Cl- conjugate base is less-stabilised, and is so more basic.

I guess for clarity I should state that this is not an attempt to use the common ion effect but actually solvation effects. We could dissolve something else, like lithium fluoride. I notice that HCl is a weaker acid than say, perchloric acid. There are some expensive (spectroscopic, crazy test compounds) way to test this, but I wonder if there are cheaper, more elegant ways of playing with the acid strengths of what are normally considered "strong acids". Perchloric acid forms stable solid hydrates because I suspect that hydronium is never a stronger acid than perchloric acid is. However in saturated conditions I quite suspect that at some point Cl- becomes a stronger base than water. This is not simply because there is more Cl- around (we could dissolve sodium nitrate, say) -- it's because the basicity strength of Cl- actually changes. John Riemann Soong (talk) 02:44, 1 November 2010 (UTC)

I am unclear on what you are asking then; are you asking if you can create a solution which will have measurable quantities of discrete HCl molecules in a water-based solution? I suppose its possible, if you take enough water out of the solution through solvation effects with a highly soluble solute, you could do something like that. However, lithium fluoride wouldn't work as it would generate additional OH- which would throw everything off (the flouride ion is a weak base; since HF is a weak acid). --Jayron32 02:58, 1 November 2010 (UTC)

Is there such a thing as solvated HCl -- the solubility of which I suppose is very low -- before it turns into gas? What I'm trying to ask is firstly whether I can create a stronger HCl solution even though I am far from having 38% HCl say. Let's say I have 3.8% HCl and I saturate the rest of the solution with something like lithium bromide or something. Will I have the strength of 38% HCl (in terms of the pKa of the dominant acidic species in solution), just 10 times more dilute?

Because I note that 3.8% HCl (no salt) does not behave like 38% HCl that is ten times more diluted. Fischer esterification runs much more than 10 times more slowly with conc. HCl that has been 10X diluted. (Granted this is in the glacial carboxylic acid and not water, so we maybe talking about an RCOOH2+ species instead, but...) I believe 38% HCl will form carbocations (if the alkene is water-soluble -- take pyran maybe), but dilute HCl will not. I wonder if I can get the strength of concentrated HCl without needing concentrated HCl. The concentration will be much less of course, resulting in a slower reaction, but the strength will be comparable. John Riemann Soong (talk) 03:16, 1 November 2010 (UTC)

AH. But it has nothing to do with the HCl per se in these reactions, its the hydronium ion (acidity) which does the relevent work. In other words, its not the pKa, it is the pH which makes a difference here! HCl tends to be used in these cases because other strong acids have their own problems, for example H2SO4 tends to cause unwanted deydration problems (if there are any hydroxides present in the target molecules) while HNO3 can both nitrate molecules AND oxidize them. HCl has the advantage that a) it is a strong acid, so can produce very low pH's, and b) the Cl- ion is pretty much inert, and is unlikely to cause unwanted side reactions, which can occur with other strong acids. It's even better than HBr or HI, which, due to the softer nature of the Br- and I- ions, tend to be better nucleophiles, so they have their own problems with side reactions. HCl is primarily used where you need a very low pH (high hydronium/H+/acid/whatever concentration) and you don't want side reactions. --Jayron32 03:23, 1 November 2010 (UTC)

There is something more than a pH effect here I think. I read somewhere on another professor's page (confirming my suspicion) that the pH scale is really only effective down to pH=0. Lower than that, you can talk about a hydrogen ion concentration, but the H3O+ species involved becomes markedly different. At least that was what I perceived him to be saying. That is, between pKa 0 and 14, H3O+ has around the same strength (pKa = -1.8). At higher concentrations, the pKa of H3O+ seems to drop. However, no one has confirmed this for me -- in saturated HCl solution, does the pKa of molecular HCl equal the pKa of hydronium species? This would make sense to me, because if not, more molecular HCl would continue to dissociate.

My other suspicion is that there is no way to add enough HCl until solution has a pH of -7. That would be asking for a concentration of 10^7 M, which seems impossible. Thus it seems logically necessary that either the pKa of HCl must rise or the H3O+ species to drop in pKa for HCl fumes to start appearing. John Riemann Soong (talk) 03:38, 1 November 2010 (UTC)

Where did a pH of -7 come from - you dropped that in from nowhere? For HCl fumes see below about the solubility constant of HCl in water - it has practically nothing to do with pKa.Sf5xeplus (talk) 03:52, 1 November 2010 (UTC)

It is common knowledge? You can find it at hydrogen chloride. As long as HCl can spontaneously protonate H2O, HCl reformation would seem to be minimal. In order for HCl species to start appearing, H3O+ would need to reprotonate Cl-. John Riemann Soong (talk) 04:03, 1 November 2010 (UTC)

Please - note the difference between pKa and pH - conc. HCl does not have a pH of -7 , HCl has a pKa of -7 .

If the pKa of hydronium did not change to match the pKa of HCl more closely, then hydronium would have a pretty hard time protonating Cl- to form HCl gas. Thus in the "no pKa change" situation, HCl gas would start bubbling out of solution at absurdly high H+ concentrations. I assume that as long as HCl is more acidic than effective acidity of hydronium, free HCl will dissociate. Fumes start appearing when free HCl starts appearing in solution. (How much of conc. HCl is dissolved free HCl? If you lower the temperature or increase the pressure of HCl above, I don't suppose more HCl dissociates, merely dissolves?) John Riemann Soong (talk) 04:40, 1 November 2010 (UTC)

HCl gas would start bubbling out of solution at absurdly high H+ concentrations yes that's what happens

When HCl solutions are saturated the vapour pressure of HCl(g) above the solution is 1 atm (under standard conditions) you should be able to do the maths yourself (you've got pKa and the molar concentration of a conc. solution) - ask in another question if you get stuck.Sf5xeplus (talk) 04:54, 1 November 2010 (UTC)

I don't know the solubility of HCl(aq). What is the makeup of the HCl in 38% RT HCl -- 95% dissociated HCl, 5% free HCl? My question anyhow is that HCl gas would start bubbling out of solution way too late if H3O+ did not become more acidic. The pH of conc. HCl is low, but not that low. John Riemann Soong (talk) 05:04, 1 November 2010 (UTC)

conc HCl is 38% w/w, that's saturated - it doesn't really get more concentrated. Combine that with the pKa and the equilibriium reactions and you have enough information to work it out for yourself.Sf5xeplus (talk) 05:22, 1 November 2010 (UTC)

(edit conflict) I think you need to start again. There's problem at point 1 : dissolution of HCl has little to do with pKa - you can dissolve gases in liquids and them not dissociate .. in a polar solvent like water polar gases dissolve well eg NH3 and HCl. Ionisation of the dissolved gas happens, much more so in HCl - but isn't required for dissolution. ie in conc. HCl(aq) there are free HCl molecules.

The other but - if I've understood correctly is the suggestion of adding (saturated) NaCl to a HCl solution - this is a Buffer solution, and ignoring activity effects you can easily calculate the pH using the equations in the article.

As for Cl- increasing water acidity - this isn't going to happen - Cl- is a base (weak).

The meat of the question seems to be "does saturated NaCl" alter the proportion of different types of hydronium ions - in water "H3O+" doesn't really exist - all positive dipoles will be strongly solvated (H3O+ can exist in a compound as you know) - in water (H+).(H2O)(n) is a more "truthy" description where n is undefined, but greater than 1. see Hydronium#Solvation. 87.102.115.141 (talk) 03:10, 1 November 2010 (UTC)

I believe Cl- can increase water acidity not because Cl- is acting as a base but because water has to form shells to hydrate the Cl- (granted the effect is stronger when hydrating Na+). We can ignore the common ion effect altogether as that was not my intention. NaCl is simply a cheap salt in the laboratory.

But yes altering the strength of the H3O+ species is the meat of my question. As more salt is dissolved, H3O+ becomes destabilised. I suppose the Zundel and Eigen cations still exist, just more fleetingly -- and the extensive hydrogen bonding and "charge sharing" becomes more difficult. For ease of discussion I will simply talk about the "average H+ species" in water -- I am not talking about bare H3O+. But as more salt dissolves in water, I suppose the average H+ species approaches bare H3O+ that is increasingly less and less stabilised. (That is, lone pairs still solvate it, just not as well.)

My assumption with HCl was that HCl gas isn't very soluble in water if it doesn't dissociate -- after all, that is the situation with carbon dioxide! (CO2 has a fair amount of charge separation -- but does the lack of a dipole moment hurt solvation?) I suppose what I should say that is when HCl species exist in concentrated HCl soln (either as a fuming gas or solvated species), hydronium pKa = HCl pKa, yes? In dilute solution, the pKa difference is large, but as you add more and more HCl, the pKa gap closes. John Riemann Soong (talk) 03:27, 1 November 2010 (UTC)

HCl molecules are very soluble in water, just like NH3 and MeOH molecules.. Of course total lack of a dipole in CO2 affect solubility.

I can't answer the rest - your talking gibberish. Or so it seems.

The constants you want are the solubitity constant for HCl in water, and the dissociation constant for HCl. They're called constants for a reason - they're constant. For variations the concept of Activity (chemistry) is used to explain deviations. Sf5xeplus (talk) 03:37, 1 November 2010 (UTC)

In class we always talk about dilute solutions, and dilute solutions is all that we ever analysed. I am intensely curious about the dynamics of saturated solutions, since they are easily achievable in practice and they seem to result in effects that go beyond mere concentration increases.

I'm talking about the pKa gap between H3O+ (in all possible forms) and HCl. In dilute solution the difference is ~5, but in saturated HCl solution wouldn't this gap be zero?

AFAIK the dissociation constant for HCl is not actually "constant" -- there are very large concentration effects. It is constant only if the free energy change is constant. This is true in dilute conditions, but not in near-saturated conditions, yes? John Riemann Soong (talk) 03:48, 1 November 2010 (UTC)

No. pKa is a measure (-log) of the equilibrium constant which is constant - please read Activity (chemistry). It's the activity which is considered to change.

The reactions are:

HCl(g) <<<<>>>> HCl(aq) (solubility constant)

HCl(aq) <<<<>>>> H+(aq) + Cl-(aq) (acid dissociation constant)

The acid dissociation can aid the dissolution by reducing the amount of free HCl in solution.

The amount of HCl that you can get in solution depends on both these equlibriums.Sf5xeplus (talk) 04:01, 1 November 2010 (UTC)

I think you may be going wrong because you are considering Cl- ions in isolation - no such thing exists in a solution - there must be a Na+ ion for each Cl- ion when using NaCl - the counterpoint to your half of the argument is that Na+ will increase the basicity of the solution by stabilising OH- !! - does that make sense?Sf5xeplus (talk) 03:46, 1 November 2010 (UTC)

I am not considering anything in isolation. I didn't even want to talk about the common ion effect... John Riemann Soong (talk) 03:48, 1 November 2010 (UTC)

I don't really care about the identities of the specific counterions. All that matters is that it is a neutral salt, cannot form a buffer in dilute conditions, and that it requires lots of H3O+ molecules to solvate them. I am asking -- can I add lots of NaCl to a dilute HCl solution to decrease the pKa of the hydronium species? The pH will not change but will the solution become more acidic? John Riemann Soong (talk) 03:58, 1 November 2010 (UTC)

No. It's the opposite - the Cl- will suppress the ionisation of HCl (as per common ion effect and as per Le Chatelier's principle) - even though Cl- is a weak base. You can actually calculate the magnitude of the effect because HCl/NaCl is a buffer solution - albeit a weak effect. The answer is no. absolutely no. it will not work.

The pKa can vary - according to the solvent eg different pKas in different solvent... and adding NaCL changes the solvent.. but the effect is to make it less acid. If you add enough Cl- you can start to get HCl₂- which doesn't help.Sf5xeplus (talk) 04:14, 1 November 2010 (UTC)

(undent). Look, John, consider what you get when you dissolve HCl in water at any concentration. There are only a few possible species:

• Discrete HCl molecules
• The acid species (whether you consider this H+, hydronium, extra-solvated hydronium, etc.)
• The chloride ion
• The hydroxide ion (ignore this, its concentration is far too low to be useful)
• Water molecules

Forget the pKa stuff for a moment. What you need to know is which of these species are actually involved, either as reactants or as catalysts, in the chemical reaction you are trying to do. Once you know that, worry about how to tweak the relative concentration of those things. The entire pKa thing you seem to be on seems to be a completely unrelated tangent, and its steering you away from your potential solution to your problem. pKa may end up relevent later, but lets put first things first: What are you trying to do, and what species from the HCl solution participate in what you are trying to do? --Jayron32 03:56, 1 November 2010 (UTC)

I need a reagent with a more potent Hammett acidity function, essentially. I need a stronger acidic species in terms of the acidity of the H+ species in water, and not merely H+ concentration (pH). Suppose the only starting acid I have is HCl, and other weak organic acids, if need be. If I am trying to form carbocations (or hell protonate an aromatic compound that has EDGs) it would seem not only to be pH-dependent, but dependent on the maximum acidity of the H3O+ species in water. In dilute conditions this is -1.8, yes? But in concentrated conditions this might be lower.

I suppose my main interest is decreasing the pKa of H3O+ in water below -1.8. This is what my question resolves around. I believe this is quite reasonable. The harder thing to do I suppose is measure this pKa decrease.

I suppose there is literature on this topic, but I don't know how this phenomenon would be searched for. John Riemann Soong (talk) 04:11, 1 November 2010 (UTC)

If all you have is HCl, you are unlikely to make any significant changes to the Hammet acidity function with anything you can do in this way. The effects you note may actually happen, but will probably only make smallish changes to the aciditiy of HCl. What you need, if you want a stronger acid is a, um, stronger acid, like a superacid. If Conc. HCl isn't strong enough, there's really not much you can do to conc. HCl to "supe it up" enough for your purposes. --Jayron32 04:16, 1 November 2010 (UTC)

No Conc. HCl is good enough. Actually what I want to do is increase the potency of the H3O+ species in dilute HCl solution to that resembling the situation with conc. HCl, that is, to simulate the H+ species in conc. HCl. The concentration will be less, of course. I don't believe it's just a change in activity -- the change in free energy changes too, changing K. John Riemann Soong (talk) 04:23, 1 November 2010 (UTC)

(ec)You can't get the hammett acidity function significantly lower in water because if you try water acts as a base - if you add a very strong acid to water it just protonates the water (water acting as a base) and the acidity is limited by the actiity of the 'hydronium ion' - possibly you can get it a little more acidic using salts - but in general if you want to get greater protonating power you need to use a less basic solvent.

however If you really want to increase the acidity of an aqueous solution so that it has greater protonating power you need to destabilise the oxonium ion - this is best done with a salt of a strong lewis acid, and very weak lewis base - eg LiBF4 , (but please bear in mind that the pKa does not change, only the activities change) - this is how pKa is defined - thus you want to increase the activity of H+ since pKa is by mathematical definition fixed. (NaCl will not do it)Sf5xeplus (talk) 04:25, 1 November 2010 (UTC)

Won't a concentrated salt (say non-chloride) solution interfere a lot with water's stabilising basicity? It seems to me the effect is rather large as a significant stabilisation of the oxonium ion seems to come from intermolecular delocalisation of charge. AFAIK pKa is based on free energy change per mol, which tends to be constant in most situations but not always. John Riemann Soong (talk) 04:34, 1 November 2010 (UTC)

It depends on the anion an cation of the salt - specifically their acidities and basicities.Sf5xeplus (talk) 04:49, 1 November 2010 (UTC)

Question - is it clear how adding LiBF4 to water will decrease its basicity ? Sf5xeplus (talk) 04:28, 1 November 2010 (UTC)

Well Li+ is a weak Lewis acid (in the sense of vinegar weak). The BF4- anion is a weaker base/anion than Cl-, but I don't see how Li+ destabilises H3O+ any more than additional H+ ions might. John Riemann Soong (talk) 04:44, 1 November 2010 (UTC)

You said you didn't want to add additional H+, but make do with a weak HCl solution .. :) Therefor I think you've got it.Sf5xeplus (talk) 04:47, 1 November 2010 (UTC)

I understand BF4- is a weaker anion, and Na+ isn't as strong of a Lewis acid, but why wouldn't NaCl (or sodium nitrate, sodium perchlorate, etc.) achieve somewhat of the same effect? Wouldn't Na+ destabilise oxonium cations too? With conc. HCl, is the oxonium ion at its maximum destabilisation? Any further destabilisation would simply result in reprotonation of Cl-? John Riemann Soong (talk) 05:07, 1 November 2010 (UTC)

LiBF4 is overall much more of a lewis acid that NaCl right?Sf5xeplus (talk) 05:31, 1 November 2010 (UTC)

Distinguishing H3O+ activity from H3O+ acid strength

I am not really convinced that these are the same. Activity is effective concentration, perhaps in this context effective pH. There are things that dilute H3O+ would not protonate but concentrated HCl would....to me, it's not simply because there's more H3O+ to go around such that the protonated reagent is favoured in the equilibrium. A kinetic barrier appears to be crossed that seems to be related to the free energy of the H3O+ species? If we take protonating a carbonyl in the Fischer esterification, there is a large surge in reaction rate that does not appear to be solely due to the increased activity of H+. (We could take methanol and formic acid say, and watch how much methyl formate we get at a reaction run at 34C.)

AFAIK an equilibrium constant is the ratio of all the relevant forward rate constants over the reverse rate constants. Isn't it possible that due to changes in solvation structure or the type of H3O+ species in solution that you get H3O+ species with different "eases" of protonation, i.e. different rate constants for protonating "tough to protonate" reagents and getting reprotonated? Activity AFAIK is effective concentration, perhaps affected by the other solutes "stealing solvent", but would not explain a different hydrogen bonding / solvation structures adopted by H3O+ species. That is, the H3O+ species in conc. HCl is different from the H3O+ in dilute HCl solution, and isn't merely the same species at a higher activity. John Riemann Soong (talk) 06:02, 1 November 2010 (UTC)

For all that you need Activity coefficient which is the ratio of effective concentration to 'mass' concentration (ie activity:concentration)

Changes in the Activity coefficient with concentration (ie a non linear relationship between activity and concentration) are usually taken to mean that the average chemical enviroment has changed.Sf5xeplus (talk) 06:13, 1 November 2010 (UTC)

There's a table of activity coefficients of HCl(aq) here google books Corrosion of metals: physicochemical principles and current problems By Helmut Kaesche Sf5xeplus (talk) 06:30, 1 November 2010 (UTC)

According to google books:Outlines of Theoretical Chemistry By Frederick H. Getman p.452 the high measured activity coefficient of conc. HCl might be due to HCl molecules.Sf5xeplus (talk) 06:32, 1 November 2010 (UTC)

Hmm. Would there be an observable difference between hydronium pKa dropping 1 pKa unit versus the activity coefficient increasing tenfold? (Thanks so much for your effort in finding sources btw. Wikipedia chemistry articles usually do not have any concentration-dependent data...perhaps we should update them.) John Riemann Soong (talk) 07:38, 1 November 2010 (UTC)

I only have ever taken two classes that mentioned real solutions, and they always tried to avoid the concentrated solution case. Why does the activity coefficient fall into a minimum for both univalent salts and HCl? This is not the same as the free energy minimum is it? Does the activity coefficient minimum occur at the same concentration as the azeotropic concentration? John Riemann Soong (talk) 07:49, 1 November 2010 (UTC)

1. possibly in some cases (more likely for low values of Ka)- because activity is not necessarily linear with the change in equilibrium constant , whereas it is linear with change in activity coefficient (for constant concentration)

2. read activity coefficient - the coefficient usually drops to 1 as concentration tends to 0 - because 1 represents the ideal solution case, and this is best got from very low concentrations - it's in the article.

2b and c No,no. Sf5xeplus (talk) 08:04, 1 November 2010 (UTC)

The activity coefficient minimum for HCl soln is near 20% ....that's very far from zero if "saturated" is at 38%. It doesn't seem like a coincidence to me that it's near the eutectic and azeotropic compositions. John Riemann Soong (talk) 08:11, 1 November 2010 (UTC)

Oops, my bad, I'm doing the conversions wrong. (Is ionic strength == N?) There is an activity coefficient minimum < 0.78 between an ionic strength of 0.1 and 1.0, whatever that means. John Riemann Soong (talk) 08:14, 1 November 2010 (UTC)

1.0M HCl ~ 3.2% w/w Sf5xeplus (talk) 08:26, 1 November 2010 (UTC)

Hmm upon examining the data at Hydrochloric acid, it seems to me that H3O+ Cl- is optimally solvated at around 20% or near the azeotropic concentration (interestingly this is near the eutectic point as well). Does the falling activity coefficient with increasing concentration (up to around 20% w/w HCl) this actually mean the average strength of the H3O+ species decreases with concentration until the azeotropic concentration is reached?

Is this when the derivative of free energy of solvation with respect to concentration is lowest? This seems highly peculiar to me -- I would assume that maximum decrease in the free energy of solvation would be near a concentration of zero. None of this was ever mentioned in my chemistry classes. And it is also so very relevant! Why did they omit it? John Riemann Soong (talk) 08:04, 1 November 2010 (UTC)

Is this wrong now? Can you slow down a bit, cos this is starting to read like random noise. Please double check the above because it looks nearly completely wrong.Sf5xeplus (talk) 08:19, 1 November 2010 (UTC)

The relationship between free energy and activity is given at activity coefficient ie

G=G₀+RTln(a_cc) where a_c is activity coefficient at concentration, and c is concentration

differentiating with respect to concentration gives:

dG/dc=RT/c + ( RT/a_c x d(a_c)/dc )

I don't think that will have a minima.Sf5xeplus (talk) 08:37, 1 November 2010 (UTC)

clarify the original question a long time ago - if another species starts to appear at high molality eg lets say H4O²⁺ then that has a separate pKa, (because it's a different acid) the pKa of H3O⁺ or whatever doesn't change.

1. If the pKa (or activities) look odd at high conc. then this could mean that a new compound is being former at high conc.

2. But in stuff like water it gets complex due to the dynamic nature of the liquid - it may be right to take a fuzzy approach since actually cations are hard to categorise or temporal - it's easier to just say that the average 'proton' energy increases, and map that onto the activity figure

3. And finally - this means that some experimental activity figures may not be theoretically correct - this is likely for the high activity coefficients in HCl that are found when HCl is very concentrated ie when they go to 4 or 8. High figures like this suggest option 1. 87.102.115.141 (talk) 09:47, 1 November 2010 (UTC)

I note from the physical properties of concentrated HCl that the viscosity increases drastically after some threshold. But nonlinear viscosity behaviour with concentration appears to be consistent with perhaps saturated NaCl solution [1]. (This is not to even include the interesting nonlinear behaviours for viscosity, activities and K_w to be gotten at high temperatures.) Is K_w necessarily ~10^-14 at 20C in concentrated salt solution -- that is, is neutral pH for a saturated salt solution at RT necessarily 7? John Riemann Soong (talk) 19:47, 1 November 2010 (UTC)

K_water is really for pure water at standard conditions, so changes could be factored in using the changes in activitys, or activity coefficients (which are related to the changes in the free energy of the components)

Really you should call it K_{ionisation of water in saturated salt}, and yes it will be a bit different.Sf5xeplus (talk) 05:08, 2 November 2010 (UTC)

As far as I can tell the physical properties of conc. HCl are fairly smooth with concentration. except vaporpressure - which is due to the HCl solution being saturated above 38% at 1 atm.Sf5xeplus (talk) 05:11, 2 November 2010 (UTC)

By the way - in terms of chemical kinetics, the effects of ionic strength on reaction rate are described by the primary salt effect and secondary salt effect see google books Chemical kinetics and reaction dynamics Santosh K. Upadhyay pp.190-2 and 192-3 (or search - there are many examples on google).

Note that the primary salt effect depends on all the reaction materials not just the H+ : so is complex

These aren't really applicable when the reaction species changes. The secondary salt effect does cause increasing ionisation (of weak acids) as salt concentration increases .. due to increasing electrolytic strenght (dielectric strength of the solvent also increases)

For the same reason increasing salt strength could stabilise different H+(aq) ions - but the key term here is stabilise - for that reason I wouldn't expect greater protonating power to result. Sf5xeplus (talk) 07:22, 2 November 2010 (UTC)

But it occurs to me that whatever H+ protonates will be stabilised as well! ... thus, in concentrated salt solution would I see a greater favourability for SN2 reactions, or for anomeric reactions, or for acyl reactions, especially under neutral conditions? If I put methanol and acetone in concentrated salt solution for example would there be a lower barrier towards forming methyl formate (and vice versa -- a lower barrier to hydrolysis under neutral conditions)? The book says that primary salt effect doesn't appear to affect neutral reagents too much, but they seem to be talking about inorganic chemistry -- what about steps in organic chemistry that require separation of charge or where permanent dipoles already exist? So if I wanted to attack an alkyl chloride for example, in addition to the whole trick of adding potassium iodide, would adding more salt in general also help? John Riemann Soong (talk) 09:16, 2 November 2010 (UTC)

Adding salt increases the dielectric constant - assuming that is the only effect then anything with charge, or a dipole should be stabilised - both reactants, products and intermediates. How that affects the rate of a particular reaction with depend on what exists at the rate limiting step primarily - eg for anionic nucleophilic attack on an (neutral) alkyl halide the intermediate and the anionic reactant will both be stabilised - this makes the nucleophile less nucleophilic, but the intermediate will be a little more stable.

The best examples are probably when a neutral substance fissions into charged species eg SN1 nucleophilic substitution, or ionisation of a weak (non charged) acid eg acetic acid - both of these are helped by increasing dielectric constant.Sf5xeplus (talk) 09:44, 2 November 2010 (UTC)

Something like the reaction of an alcohol ROH with an acyl chloride RCOCl would also probably be speeded up, since the intermediate is a zwitterion.Sf5xeplus (talk) 09:53, 2 November 2010 (UTC)

I meant the value of the Dielectric constant when I was saying dielectric strength, not to be confused with this type of Dielectric strength.Sf5xeplus (talk) 09:59, 2 November 2010 (UTC)

Birefringence, redux

I suppose I should make my question clearer. I'm trying to write a lab report, and the article isn't at all helping identify which directions birefringence can be seen. In a uniaxial crystal, there is only two orientations (out of 6) in which birefringence can be seen, yes? (I had to guess from the hexagonal crystal structure of calcite -- the language isn't clear at all!) I couldn't figure out from the article

....if I laid the crystal shown in the images on its side and looked at the words, neither of the 4 faces would show birefringence, yes? John Riemann Soong (talk) 05:29, 1 November 2010 (UTC)

this image?

You mean this image? with 4 opposed faces. As far as I can tell there are 3 faces of one type and 1 (hexagonal) face of another.

If you pick one of the three faces, and look 'down' into it (offset from the perpendicular) you should see that as you rotate around the perpendicular the trigonal groups (CO₃^2- carbonate) go from looking flat, to side on, to flat etc - this seems to be anisotropy and I would therefor expect double refraction based on what the Birefringence article says.

The hexagonal face doesn't have such a strong effect (though there is some minor change every 120degrees) - I wouldn't expect birefringence as much. (or at all)

This isn't my subject - if that doesn't sound right I'd wait for an expert opinion.Sf5xeplus (talk) 09:22, 1 November 2010 (UTC)

KNO3 + KI

What happens when potassium nitrate and potassium iodide are heated? Is iodine produced? --Chemicalinterest (talk) 12:45, 1 November 2010 (UTC)

According to [2], the iodide is oxidized to the iodate. shoy (reactions) 13:16, 1 November 2010 (UTC)

Solar cells: Difference between dark current and diode current

Hello, I have noticed that some texts refer to diode current and dark current in PV cells interchangeably. Could someone kindly explain the difference, if there is one?

The most common rendition I have seen is:

Diode current = dark current . (exp(eV/kT) - 1)

However I have also seen basically the same equation to define dark current:

Dark current = Jo . (exp(eV/kT) - 1) where Jo is an unidentified constant.

Assuming they are *not* the same thing, what is the physical nature of how they differ? To my understanding both terms describe a forward current that flows the p-n diode under the influence of an externally applied voltage.

Many thanks. —Preceding unsigned comment added by 146.23.212.21 (talk) 13:51, 1 November 2010 (UTC)

You are looking at two different cases of "loose terminology" describing the ideal diode equation. A photoelectric cell is a photodiode, and ideally behaves according to this equation that relates current and voltage. The term "dark current" is being used to refer to the current that would flow even if no light is shining on the cell. In actuality, that is a bit loose - what this really refers to is the saturation current and is a semiconductor physics parameter. In reality, diodes are very complicated: see our article on diode modelling for an introduction to some of the mathematical idealizations of them. In any case - the parameter J₀ probably refers to the effective current density for a particular device, and depends on diffusion parameters of the semiconductor - i.e., its geometry, its chemical makeup (doping), and so on. Here is an extremely technical overview of the semiconductor physics that are relevant to this process in a P-N junction: Basic Device Behavior. (While this overview is horribly complicated, the underlying processes in a PN junction actually are complicated - so there's no sense sugar-coating it). You can accept the derivations at face-value, or you can work with idealized, empirical models of current/voltage relationships and light-intensity/power-generation measurements. Nimur (talk) 17:26, 1 November 2010 (UTC)

Thanks Nimur, glad that the problem is the complexity of the subject and not my stupidity :) (this time). Yes for my purposes it is sufficient to understand the dark current as being that which flows in the diffusion direction in a darkened cell, and balances out the drift current. As a (forward) external voltage is applied, the electric field in the space-charge region is reduced, allowing diffusion to increase, yet the drift current remains unaffected since there's still just as many electron-hole pairs being created, hence the overall diode current increases as described by the first equation given above. —Preceding unsigned comment added by 146.23.212.21 (talk) 08:21, 2 November 2010 (UTC)

knife

what kinda knife do the usa army use today? —Preceding unsigned comment added by Kj650 (talk • contribs) 22:01, 1 November 2010 (UTC)

The United States Army issues the M9 bayonet. Some services and special operation groups may use other equipment, including the Aircrew Survival Egress Knife, the United States Marine Corps' standard OKC-3S bayonet, or older M7 or M6. Here is the official page for the Bayonet at the US Army website. See also, Bayonets, knives, bayonet-knife models for a more thorough list, including historical issues. KA-BAR, while popular amongst service members for historic reasons, is not standard issue, although in some cases it may be officially issued to active duty Army units. Nimur (talk) 22:32, 1 November 2010 (UTC)

Reading M9 bayonet, I see that "some production runs of the M9 have a fuller and some do not". Blood groove redirects to Fuller (weapon), but that article currently makes no mention of that common term despite it being the title of two of its four references. Should Fuller (weapon) contain some explanation of "blood groove". -- 124.157.218.101 (talk) 01:23, 2 November 2010 (UTC)

I don't think so. Our Fuller article explains the function quite well. If anything, the referring pages should be changed to fuller. "Blood groove" is based on a misconception-- that the groove somehow increases blade performance by letting blood escape through the groove. This is false. If anyone wants to include this terminology, it should be clear that it is a misnomer.SemanticMantis (talk) 16:36, 2 November 2010 (UTC)

recycling code

what plastic recycling code do vacuum cleaners have —Preceding unsigned comment added by Kj650 (talk • contribs) 22:37, 1 November 2010 (UTC)

You asked this already, but I guess you got no answer. Ariel. (talk) 00:01, 2 November 2010 (UTC)

Usually, recyclable plastics will have a code blazoned on to them. If the vacuum cleaner doesn't specify, it's useless for us to speculate. Various brands and models use different manufacturing processes. Do you have a specific model in mind? Nimur (talk) 00:15, 2 November 2010 (UTC)

(Edit Conflict) I doubt that there can be a simple answer to this since: (a) different makes and models will surely use different plastics; (b) the same model will almost certainly use different plastics for different components; and (c) any model will certainly include significant non-plastic components (for example, metals in the motor). If particular plastic components are recyclable, they may carry an applicable symbol (probably on their inside surface). Recycling a vacuum cleaner in order to salvage and reuse component materials could probably only be done by a professional outfit specialising in such work, since some components will likely contain substances requiring special handling or disposal - some junked electrically powered equipment is exported to third-world countries where such work is profitable.

You might find the list of articles at Index of recycling topics useful. 87.81.230.195 (talk) 00:24, 2 November 2010 (UTC)

November 2

Technocracy

What country or countries today would be considered most like a technocracy? The article mentions China and Russia in passing, but I find that frankly ridiculous. 59.46.38.107 (talk) 00:54, 2 November 2010 (UTC)

This was my question. I forgot to sign in. The Masked Booby (talk) 00:56, 2 November 2010 (UTC)

Our article references this source for the Russia/China claim: The Technocratic Trend and Its Implication in China from Observa. I would hardly call that a notable or widely-read, well-respected expert publication in the domain(s) of technology, politics, or social commentary; so take the citation with a grain of salt. I think there are no current "technocracy governments", though there are elements of technocracy in many states and non-state actors (particularly, certain corporations and business structures). Nimur (talk) 00:59, 2 November 2010 (UTC)

I agree with the summation. Now would you care to hazard a guess at which may be considered more technocratic than the norm? The Masked Booby (talk) 01:04, 2 November 2010 (UTC)

To be fair I think this may be more a question for the Humanities reference desk. --jjron (talk) 01:58, 2 November 2010 (UTC)

It might be more useful to compare, more generally, the way that expert decisions are made in different states. For example, in the United States, when you have a complicated scientific question that has to do with policy — say, concerns about global warming, or whether the US national labs can guarantee the reliability of its nuclear stockpile without testing, or whether GMO crops should be regulated differently than non-GMO crops — there are bodies that policymakers can consult for guidance (like the National Academy of Science, or the JASON group), and there are agencies that often have some regulatory role over those areas (e.g. EPA or DOE or FDA in the examples given). But in practice the question of regulatory authority and of which brand of technical expertise to go to often devolves into Congressional debates, since they control the purse strings and can pass the laws. So we get a particularly adversarial way of making technical decisions — instead of "what do the scientists say," it becomes, "what does my scientist say vs. what your scientist says." It would be hard to argue for this reason that there is much "rule by experts" in the United States — on anything even slightly controversial, experts become proxies for other political decisions.

We might compare this to, say, France. When the French government wants to make a technical decision, it picks a few experts it trusts, asks them what to do, and does it. It doesn't open it up to public discussion most of the time, and it doesn't usually enter into the arena of party politics. (There are exceptions, I am sure.) This is one of the reasons that the French did not have anything like the American experience when it came to picking a nuclear waste repository, for example. It's experts said, "bury it here, this way," and that was that. In the United States, after some 50 years of trying to come up with such a plan, we find it endlessly scuttled by local and national politics, which deploy the experts in whatever way suits them best.

I don't know the situation in China or Russia but my inclination is to think the Chinese use experts more like France and less like the United States. None of these countries are really "technocracies" in the standard sense, but they have pretty different roles for experts in the public domain. There is a lot of work in the field of Science and technology studies that is concerned with looking at this question. --Mr.98 (talk) 02:03, 2 November 2010 (UTC)

For what it's worth both China and France are often described in the media as having decisions made by "Technocrats", as does the EU, and formely communist russia (I think that description is less commonly used for modern russia). Please use google to verify rather than asking me.

Nevertheless none of these are true "technocracies" - decisions are still heavily informed by political matters (eg france) - perhaps China is the best example of a near technocracy. I think that the perception is mostly due to bias - all modern goverments use technical experts to make decisions. (Do 'anglo-saxon' counties tend to be more heavily influence by NIMBY concerns? maybe so [3]) Sf5xeplus (talk) 06:03, 2 November 2010 (UTC)

I don't think it's really a NIMBY issue so much as it is an expectations of public participation issue. Everybody's NIMBY if you ask them if they want something big and toxic in their backyard. The trick about France and China is they don't ask them and people on the whole don't expect to be asked. In the US (and to a lesser extent in the UK), the form of deliberative government that has grown up there really sits on the idea that you always ask people what to do, which leads to the kinds of political and regulatory environments we are talking about. Germany is something of a separate case, if I recall. This table in a book that compares the US, UK, and German (and I also think Japanese and French) approaches to regulating biotechnology describes sort of the kind of analysis I am talking about. There are very different political "styles" in the countries we are talking about in respect to how they make expert decisions, and that leads to a lot of the difference in results that we see between them. I agree that none of them are "technocracies" in the strict definition, which I don't think has ever really existed. But some ways of using expert opinion are more "technocratic" than others. --Mr.98 (talk) 13:26, 2 November 2010 (UTC)

Some countries like to give themselves the appearance of being a technocracy; Romania's Elena Ceauşescu liked to pretend that she was a world renowned chemist, despite leaving school with good grades in needlework followed by a brief job in a textile factory lab. Alansplodge (talk) 10:15, 2 November 2010 (UTC)

Which country has the highest number of Nobel prizes per capita? Which country has made the most life-changing inventions and discoveries? Its the UK, of course. 92.29.115.229 (talk) 12:24, 2 November 2010 (UTC)

Of your one factual statement and one opinion with a ton of unstated and unsourced assumptions, the former is not even true. According to data on the relevant WP pages (here and here), UK nobels-per-capita looks like 1/530K vs Switzerland at 1/300K and Sweden 1/335K. Those are just two of the only four I bothered to check (US is 1/952K and Germany 1/802K), so there may be others as well. Remember verifiability is a core wikipedia policy. DMacks (talk) 12:40, 2 November 2010 (UTC)

I don't see a technocracy valuing a Nobel prize in literature or peace though, so you might want to consider that into your equation. Googlemeister (talk) 13:12, 2 November 2010 (UTC)

I don't see Nobel Prizes having anything to do with technocracy. They have largely to do with where research is fostered, and it is totally unwarranted to assume that they would be more fostered in a technocracy than not. --Mr.98 (talk) 13:29, 2 November 2010 (UTC)

Sorry should have typed England rather than the UK. 92.28.243.168 (talk) 15:38, 2 November 2010 (UTC)

I don't see how that helps much... According to Demography of England the population is 49,138,831 in 2001 or according to Demography of the United Kingdom England's population 50,762,900 from a 2006 estimate. DMacks didn't give the number of Nobel prize winners for the UK and I'm lazy to work it out for myself but as the population of the UK is 58,789,194 in 2001 or 60,587,300 from the 2006 estimate we can guess the number of winners they estimated is probably 111 or 114 or perhaps 115 to be generous. So even if we assume all these winners are from England and we take the later figure yet use the 2001 population we still only end up with ~1/427k which is still less then Switzerland and Sweden. May be you're going to limit yourself to those living in certain areas in England now but can you at least ensure you have better then 1/300K this time? (We haven't of course established that is the highest nor does it make sense to start limiting to arbitary areas in one place but not the others but anyway...). Edit: Actually looking more closely at DMacks answer the UK number of winners is source to an article and is indeed 115 so lucky that I used that. Nil Einne (talk) 03:23, 3 November 2010 (UTC)

Third in the world is not bad and I expect that if only the science-related Nobel prizes are included then it would be higher. Not forgetting all the famous English scientists. The Industrial Revolution was born in England, and was a kind of technocracy. 92.29.117.88 (talk) 11:15, 3 November 2010 (UTC)

Not bad? You first claimed the UK was the best when this was proven to be wrong you then changed this to England, you now simply say it is 'not bad'. As for your second claim, Switzerland (with 20) is at 1/389k if we remove economics, literature and peace prize winners, Sweden (with 14) at 1/671k and England (with 84) at 1/617k so it seems that England may beat Sweden but they still get their arse whipped by Switzerland. (I used a population of 51809700 a mid 2009 estimate for England [4] since Switzerland and Sweden are 2009 and 2010 estimates respectively.) Further we haven't established that all 84 really belong to England nor have established they aren't any higher that haven't been considered. Nil Einne (talk) 08:40, 4 November 2010 (UTC)

Ignoring all the ad hominum stuff, the roll of famous scientists and being the birth-place of the industrial revolution overrules the lesser consideration of only being 2nd or 3rd place in the Nobel prize league. So the UK, Britain, or England is the most technocratic country. 92.29.115.158 (talk) 10:54, 4 November 2010 (UTC)

It used to be widely understood that an English gentleman doesn't stoop to vulgar boasting. O tempora o mores! Alansplodge (talk) 23:12, 4 November 2010 (UTC)

No boasting intended, just answering the question asked, with the supporting reasons. 92.15.28.27 (talk) 14:50, 6 November 2010 (UTC)

Clothes drying under clothes pegs

When I hang my clothes out to dry on a clothes line why is that the fabric underneath the pegs gets dry just as quickly as the rest of the cloth? Wouldn't it seem logical that that small patch covered by the peg would remain damp? (I can guess at the type of answer I would give here, but am interested to hear what others think). --jjron (talk) 03:24, 2 November 2010 (UTC)

No, because it's such a small amount. HalfShadow 03:26, 2 November 2010 (UTC)

Gravity helps. If you hang a long-sleeved shirt out to dry, the top will be dry far sooner than the bottom of the arms and waist. The Masked Booby (talk) 03:27, 2 November 2010 (UTC)

As the cloth near the pin dries, the water under the pin diffuses into the dry area. Ariel. (talk) 07:31, 2 November 2010 (UTC)

And, at least in my experience, in many cases the assumption is wrong. The part under the pegs does dry slower that equivalent areas not under them. But the effect is small, and the overall amount of water is so small that usually nobody cares. --Stephan Schulz (talk) 07:37, 2 November 2010 (UTC)

laminated wood

whats laminated wood

example

http://www.youtube.com/watch?v=pvZXqSn-mIs&feature=mfu_in_order&playnext=1&videos=H6X28Y6mdrU —Preceding unsigned comment added by Kj650 (talk • contribs) 05:03, 2 November 2010 (UTC)

Laminated wood is pieces of wood glued together to make a bigger single piece. When the pieces are very thin and flat we call this Plywood.

In the video the pieces (look closely at the end grain of the wood in the video) are about 1" thick - you should be able to see that 3 pieces - the grain of the wood doesn't match so there are 2 joins.

A very thing flat piece of wood on top of something else is also a wood laminate and is called a veneer

Usually the pieces of wood are joined longways, when they are joined longways, and shortways it's called Glued laminated timber Sf5xeplus (talk) 05:22, 2 November 2010 (UTC)

train deaths

The following discussion is closed. Please do not modify it. Subsequent comments should be made on the appropriate discussion page. No further edits should be made to this discussion.

---

does anybody think this

http://www.dreamindemon.com/2010/02/22/three-teen-girls-unable-to-outrun-train-struck-and-killed/

was likely a suicide like this

http://www.dreamindemon.com/2010/02/27/police-two-teen-girls-hit-by-train-were-part-of-suicide-pact/

and the guy was lying so he didnt get committed —Preceding unsigned comment added by Kj650 (talk • contribs) 05:34, 2 November 2010 (UTC)

Please see the disclaimer at the top of the page The reference desk does not answer requests for opinions. Sorry.Sf5xeplus (talk) 05:40, 2 November 2010 (UTC)

The discussion above is closed. Please do not modify it. Subsequent comments should be made on the appropriate discussion page. No further edits should be made to this discussion.

Faster than Light

Lets assume i hold a lamp, and i travell in perfect vaccum at the the speed of ½c, will not the light from the lamp move faster then c? Daily motion of the Heavens was to hard to understand? But the moon goes around the earth, the earth goes around the sun, and the sun goes around the milky way, doesn't a light from the moon get a push, or is c independant to the course of the satellites of the universe? —Preceding unsigned comment added by 92.254.188.129 (talk) 12:36, 2 November 2010 (UTC)

The light will move away from the lamp at the speed of light, and this is what you (travelling with the lamp) will observe. An outside observer will also see the light moving away from you at the speed of light. This is one of the fundamental postulates of Einstein's Special relativity. The Michelson–Morley experiment is a famous early (failed) experiment roughly along the lines of the concept you are suggesting. --jjron (talk) 13:56, 2 November 2010 (UTC)

Basically the answer is that everyone will measure the speed of light (in a vacuum) as being c, no matter how fast they or the light emitter is traveling. It's extremely counterintuitive but has been verified by experiment pretty thoroughly. It is, as Jjron notes, the foundation of Special Relativity — SR is basically an exploration and elaboration of the implications from this fact. --Mr.98 (talk) 14:41, 2 November 2010 (UTC)

Would the light be red-shifted or blue-shifted to the .5c speed observer? Googlemeister (talk) 16:26, 2 November 2010 (UTC)

Neither, but it would be red-shifted to someone "stationary" behind him and blue-shifted to someone "stationary" in front. --Sean 16:40, 2 November 2010 (UTC)

92.254.188.129, If light were a classical wave in the sense of being a vibration in an elastic medium, then the answer to your question would be 'no'. The light would always have a fixed speed relative to that medium, and if a light source were moving in that medium in the direction of propagation of the light, the speed of light relative to the source would actually be c-v, where v is the speed of the source relative to the medium. In order for an observer to observe light at a speed equal to c+v, they would have to either move into the light beam or else move with a light source which is moving backwards relative to the direction of propagation.

However, in recent times, the official belief is that light propagates in empty space and that it defies the normal rules of vector addition of velocities. Einstein postulated words to the extent that light will always be measured to have the speed c irrespective of the motion of the source or the receiver. This postulate is the cornerstone of the special theory of relativity. And so, based on either 20th century physics, or 19th century physics, the answer to your question is 'no'. You cannot push a light beam faster by pushing the source. Such a vector addition phenomenon is something which applies to particle projectiles and not to waves. David Tombe (talk) 22:44, 2 November 2010 (UTC)

Is the odd fact of both observers seeing the light go at the same speed explained by time going at different speeds for each of them?

Well the second is defined in terms of the speed of light (or rather, frequency of radiation from the caesium 133 atom), so time must be the same for both observers in their own rest-frame, but each observes time as going slower in the other's reference frame. Dbfirs 17:31, 3 November 2010 (UTC)

The anon asks about 'the odd fact of both observers seeing the light go at the same speed'. This 'odd fact', which is widely acknowledged to be counter-intuitive because it defies classical Galilean addition of velocities, is a postulate which is the cornerstone of a theory. But I have never seen any attempt to explain this 'odd fact' in its own right. At any rate, one should never get any of this confused with the issue of units of measurement. The theory is independent of units of measurement. David Tombe (talk) 17:27, 4 November 2010 (UTC)

I've corrected my indent error to make clear that I was replying to the (unsigned) supplementary question. The way that we define a unit of measurement determines what we mean by that measurement, and thus whether it "goes at different speeds". Only in General relativity is "time" (as measured by this definition) different for observers in different gravitational fields. I can't get my brain around any alternative way to define time. Perhaps there isn't a logical alternative. Dbfirs 23:02, 4 November 2010 (UTC)

Well I'm afraid that we'll have to disagree on that. The system of units decides the numerical value of a speed, but it doesn't determine the speed itself as a physical concept. David Tombe (talk) 10:21, 5 November 2010 (UTC)

Yes, obviously the system of units is irrelevant, but the way we define a measurement determines what we mean by it. Time is not easy to define in an abstract way. Dbfirs 07:45, 6 November 2010 (UTC)

If you as an observer move faster than light, you will experience something similar to the sound barrier but visually. Everything ahead of you will be visible but nothing behind you is. ~AH1^(TCU) 18:40, 7 November 2010 (UTC)

Cheaper to turn off Compact fluorescent lamps briefly?

With old fashioned incandescant lightbulbs the consensus view was that it was cheaper to leave them on rather than turn them off for a few minutes, as the stress of being turned on or off wore them out more quickly. What is the best strategy regarding energy-saving lightbulbs in a domestic situation? Thanks. 92.29.115.229 (talk) 12:45, 2 November 2010 (UTC)

It depends on the CFL. Some ballasts are more gentle, some less. But in general, CFLs are designed with a limit on the number of expected switches. That said, mine now seem to come with warranties of 10 or even 12 years, so the much greater financial risk seems to be losing the warranty slip. The design limit is large enough that manual (as opposed to, say, movement-triggered) switching is unlikely to be a problem. --Stephan Schulz (talk) 12:55, 2 November 2010 (UTC)

In the UK they are often given away, or are available for a few pence each. 92.29.115.229 (talk) 13:06, 2 November 2010 (UTC)

It's an interesting scenario. Given that CFLs typically use 20-30% the energy of an incandescent bulb for the same light output and are considerably more expensive to buy, it would seem to make a lot more sense to turn off the incandescent to save power and money as they're costing lots to run but are cheap to replace. Older CFLs had a warm up period where they started a bit dull and gradually brightened to full intensity, and as far as I know they still do, so that makes turning them on and off inefficient in terms of having a consistent light output. In Australia incandescent bulbs are being phased out and I was reading recently of people complaining that their new CFLs were having short lifespans, shorter they were claiming than their old incandescents (I believe it was generally the cheaper brands and seemed to be worse in certain locations). The reason suggested was that power fluctuations were causing high wear on the CFLs leading to the short lifespan. If correct, this would suggest they are quite susceptible to wear and tear and the answer to your question would be to leave them on. --jjron (talk) 13:27, 2 November 2010 (UTC)

List_of_MythBusters_episodes#2006_season, Episode 69. shoy (reactions) 15:43, 2 November 2010 (UTC)

Better link: MythBusters (2006 season)#Lights On/Off. --Anonymous, 07:27 UTC, November 3, 2010.

I think this myth started in the days when fluorescent lamps were very expensive and electricity was very cheap. (Yes, I can remember them.) The claim had a better chance of being true then, but it was probably just a marketing lie even in the "old days". From a psychological viewpoint, the flickering and reduced light output for the first second or two after switchon might be a valid reason for leaving the light on rather than turning it off for a few minutes, but warm-up time is shorter if the lamp is still warm from recent use. Dbfirs 08:25, 3 November 2010 (UTC)

If you are leaving a room for fifteen minutes or longer, it makes sense to turn off a fluorescent light. For a shorter time away, leave the light on. If you pay time of day rates, at peak rates the time may be five minutes. These times take into account the cost of replacing the lamp if it burns out soon due to frequent turning on and off. From a pure energy cost basis, they could be switched off if you will be away only a few seconds. This is per US Department of Energy. I have to pay for light bulbs, unlike some above who somehow get them "free." As Robert Heinlein pointed out "There ain't no such thing as a free lunch." The manufacturers do not produce them free, so it is likely your tax dollars paying for them. If it is in an overhead fixture, there is also the risk and inconvenience of getting a ladder and changing them, or paying a janitor to change them in a commercial building. Compact fluorescent bulbs have a drastically reduced life if they are turned on and off frequently. The stated lifetimes on a package of GE fluorescents assume they will last several years if they are burned for several hours per day. General electric says that compact fluorescents "work best if they are left on for over 15 minutes each time they are turned on" and that they "take up to 3 minutes to warm-up. Frequently switching them on and off will shorten the life of the product." Edison (talk) 14:18, 3 November 2010 (UTC)

That sounds excellent advice, though the timing will depend on the cost of replacing the fitting. The UK "free" and "10p in supermarkets" compact fluorescent bulbs are subsidised by the electricity companies who have to show that they have encouraged energy conservation. Dbfirs 17:14, 3 November 2010 (UTC)

I was just in a US store, and regular GE CFLs sell for several dollars apiece. A government might subsidize the cost to encourage a shift away from incandescents, but once incandescents are banned, it would be odd for them to go on subsidizing the CFLs, in contrast to other useful items which went unsubsidized. One might want to stock up on them while they are still free/cheap, but do they have some limited shelf life before capacitors, etc, go bad? Likewise, one might stock up on very cheap incandescent bulbs before their manufacture is phased out. I think the latter can be stored indefinitely and still work fine. Edison (talk) 21:06, 3 November 2010 (UTC)

I would stock up on too many. LED lights are getting cheaper and brighter all time although they do still suffer heat problems particularly in enclosed fixtures and don't always have the longevity that's sometimes claimed. Nil Einne (talk) 20:02, 4 November 2010 (UTC)

I've already stocked up on cheap incandescent and CFL bulbs, but am wondering if I have been foolish because I've just installed my first LED sytem. With current outputs, I find both LED and CFL light less pleasant than the old incandescent lamps. I assume Nil Einne meant "wouldn't" above. Dbfirs 23:11, 4 November 2010 (UTC)

If man evolved from monkey, why are there still monkeys?

It might seem like a trivial question. We also evolved from bacteria, but they are still here. However, if the evolution was ape > primitive man (like the Austrolopitecus) > us, why did the middle species disappeared? Theoretically, the cave men should be better adapted than the original apes, shouldn't they then be here among us? Quest09 (talk) —Preceding undated comment added 13:10, 2 November 2010 (UTC).

Simply because of the competition for the living space. Man and chimps separated, and used a different territory (men like the savanna better, chimps likes the forest better), and therefore they never eliminated each other. Well, that is until very recently, where we started to trim the tropical forest for our own use, which is killing the few thousands of chimps remaining.

However the intermediates (that you call cave men) either used the same type as territory as Man (savanna) or the same type as apes (tropical forest) and therefore had a hard time to compete against either. They could have won the competition, of course, and eliminated us, but it just happen that they didn't, we and apes were better adapted to survive in our own type of territory, it seems. --Lgriot (talk) 13:37, 2 November 2010 (UTC)

Sometimes, monkeys have attacked humans on their own territory. (http://news.bbc.co.uk/2/hi/1107970.stm)

(Incidentally, monkeys are not chimpanzees.) -- Wavelength (talk) 20:02, 2 November 2010 (UTC)

This is a classic question for which the internet has many nice succinct answers: [5]. Short story: chimps actually do occupy a different niche than man, and practically all of the middle species that occupied the same niche have disappeared. (Consider all of the extinct species in Genus Homo.) --Mr.98 (talk) 13:41, 2 November 2010 (UTC)

e/c No. Organisms evolve to become better adapted to their current environment, but that does not mean they are 'better' than the organism they evolved from. Have a read also of Common descent, Evidence of common descent, and Human evolution as starting points. And for proof of concept, using a thought experiment, try living in the jungle with some chimpanzees/gorillas/orang-utans, etc to determine which species is better adapted to that environment. --jjron (talk) 13:44, 2 November 2010 (UTC)

Remember the same argument could be made for bacteria. Why do single celled organisms still live if multicelled ones are better adapted? The simple answer as above answer have stated is better adapted doesn't mean better in every way. Organisms can co-exist if they fill different niches. Humans may be better adapted to live in some environments and conditions but in different ones other organisms are better adapted. (Given all our tech we can now comfortably live in many environments partly by changing our environment to suit us but it took us a while to get here.) If you're talking about such extreme comparisons as bacteria vs humans, humans can't live in another humans mouth or stomach, many bacteria can. Speciation is somewhat relevant here and to some extent so is Species problem. Nil Einne (talk) 13:59, 2 November 2010 (UTC)

The most fundamental explanation, it seems to me, is that humans did not evolve from modern monkeys. Humans and monkeys both evolved from the same common ancestor, which is now extinct. The same goes for bacteria. Humans did not evolve from modern bacteria—rather, modern bacteria and humans are both descendants of a now-extinct common ancestor. —Bkell (talk) 14:08, 2 November 2010 (UTC)

Mankind did not evolve from any modern-day apes. Both chimps and humans share a common, now-extinct, ancestor. Probably Nakalipithecus or something very similar to it.

However, even if Nakalipithecus was still around, it wouldn't be a logical paradox. It's not as if every single one of them magically turned into either a chimp or a human. Populations probably got separated from the main group and began adapting to their new surroundings. Eventually they adapted so much that they were no longer the same species as the group they got separated from. If, hypothetically speaking, some of them had found some sort of isolated monkey-paradise, it's would not have been impossible that they would have remained mostly unchanged over all this time while other members of their species adapted and evolved. It's too bad that didn't happen, I'll bet biologists would love to get a blood sample from one. APL (talk) 14:34, 2 November 2010 (UTC)

Apart from the actual substance of this question, humans are generally not considered to have evolved from Monkeys, but rather Apes (in fact, humans are considered a Great ape). The trouble is, apes are more closely related to Old World monkeys than Old World monkeys are to New World monkeys, making a good illustration of the inconsistencies in the traditional way in which we classify life. Buddy431 (talk) 15:10, 2 November 2010 (UTC)

If we are the progeny of our grandparents, why do we have cousins? The answer is blindingly obvious: we are not the progeny of our cousins; we both evolved from common ancestors; and our existence does not invalidate the existence of our cousins. They share many traits with us, but have many different traits than us. As we pursue more distant ancestral relations, we see fewer common traits; and if we keep investigating farther up the ancestral tree, we gradually and eventually reach an ancestor who is quite unlike ourselves. If we count all the offspring of a very distant ancestor, we will clearly see a very broad group of individuals. Nimur (talk) 16:16, 2 November 2010 (UTC)

Are you replying to me, Nimur, or to the original question? You're answer doesn't make much sense as a reply to my earlier remark. Buddy431 (talk) 18:53, 2 November 2010 (UTC)

(I was responding to the OP. Sorry for indent-confusion; I hope I have fixed it. Nimur (talk) 19:19, 2 November 2010 (UTC)

As explained |here. CS Miller (talk) 16:47, 2 November 2010 (UTC)

I don't understand why any answer has involved information or theory or any other knowledge -- the question itself contains a logical absurdity and so needs nothing but logic to answer it. (The OP needs to ask a question that makes sense to get an answer that isn't just logic-based.) Look: "if the evolution was ape > primitive man (like the Austrolopitecus) > us, why did the middle species disappeared? Theoretically, the cave men should be better adapted than the original apes, shouldn't they then be here among us?" But the evolution was also "something else" then "ape" (or whatever); and it was "something else earlier" then "something else" then "ape"; and so on. The question asks why "the middle species disappeared," but objectively there is no "middle species," which is entirely an invention of the words used by the OP, and literally doesn't exist otherwise. The question implies that every single ancestor of every single species should still exist, EXCEPT the first. The obvious answer to this is: look around -- the premise of your question is clearly untrue. As for "why?", then you're asking "Why does ANYTHING go extinct?" I'm sure the OP can look up "extinction" and quickly come up with better comprehensive answers than we will provide here. But "why didn't the middle species survive" is literally a senseless question, apart from the general question of "Why doesn't EVERYTHING survive, except the first ancestor?" 63.17.94.75 (talk) 04:21, 4 November 2010 (UTC)

The answer to this question is that evolution works by divergence. Some organism X_O exists in locations A and B. Over large quantities of time X_O adapts to location A in one way and to location B in another way, producing separate species X_A and X_B. X_O will only continue to exists if there's some location C where no adaptation is necessary. This happens more frequently in the oceans (e.g. the continued existence of more primitive sharks or things like coelacanths) because ocean regionally tend to show less long-term variability than land regions. Our primitive intermediary ancestors no longer exist because either (a) they diverged as a group until they became us, or (b) they diverged as a separate group in different directions (e.g. neanderthal man) were either reabsorbed into our group or died out as the environments they were adapted to disappeared.

The idea is only confusing when you think of the human race as a necessary outcome. When you think of it more like a river, which can split and lead off into different directions (where some forks dry up completely and only one fork leads to where we are) it's a bit clearer. --Ludwigs2 05:00, 4 November 2010 (UTC)

Plant respiration

Photosynthesis requires intake of Carbon dioxide and the plants release oxygen in the process. However, do plants breathe oxygen like animals? --117.204.87.227 (talk) 16:18, 2 November 2010 (UTC)

Yes. They use carbon dioxide with water to make glucose. At night, plants burn this glucose by taking in oxygen. However, plants give off more oxygen than they take because to grow they need to join glucose together to make cellulose, so not all of the glucose is burned up. --The High Fin Sperm Whale 16:25, 2 November 2010 (UTC)

Plants certainly take in oxygen for respiration, but "breathe" isn't really the word to use to describe it. --86.130.152.0 (talk) 16:57, 2 November 2010 (UTC)

Yeah, the term breathing usually refers to respiration via lungs, which plants of course don't have. Something I just learned that surprised me is that plants respire not only through their leaves, but also through their roots; see soil gas. Our root article does mention "breathing pores" in reference to aerating roots, so apparently the word "breathing" is at least occasionally used when discussing plant respiration. Red Act (talk) 19:02, 2 November 2010 (UTC)

Cooler than that, is this paper which discusses how Equisetum telmateia aerates its roots by taking air in through its leaves, allowing it to grow in waterlogged soil, which is about as close to breathing as a plant will get. The paper predicts that in the extinct Calamites from the Carboniferous, up to 70 litres of air could have been transported to its roots per minute! SmartSE (talk) 20:38, 2 November 2010 (UTC)

Just to clear up a common misunderstanding. Many people believe plants photosynthesise during the day and respire only at night. However plants undergo cellular respiration all the time, both day and night, just like animals. --jjron (talk) 14:07, 3 November 2010 (UTC)

Where are all the universes ?

I have read the Many-worlds interpretation article, but there is something I can't understand, no doubt due to my limited knowledge of physics. If there are many universes beyond our own, where are they ? Do they exist in the same sense that our universe exists, i.e. physically ? Wouldn't so many universes need a humungous amount of spacetime to contain them ? I guess I would intuitively think that Mother Nature would use her resources more sparingly. Regards, 62.241.87.223 (talk) 17:04, 2 November 2010 (UTC)

"Beyond our own universe" means just that i.e. not having a location anywhere in this universe, and posessing each its own spacetime. On the presumption that there are infinitely many of them, encompassing every option of every alternative, there is someone very much like you wondering the same thing. The many-worlds theory is not proven but here are ideas in fiction about it. Cuddlyable3 (talk) 18:30, 2 November 2010 (UTC)

These scientist will eventually figure out that the "universes" that they see in the formulas are just representations of other galaxies that have been completely separated by the emptiness of space. —Preceding unsigned comment added by 165.212.189.187 (talk) 18:26, 2 November 2010 (UTC)

This is certainly not what the MWI is about, at all. --Mr.98 (talk) 18:28, 2 November 2010 (UTC)

Agree. 165.212.189.187's interpretation is completely incorrect and is unsupported by any reliable scientific literature. Here is one of the foundational papers of many-worlds interpretation, Quantum Mechanics and Reality (1970). The field has absolutely no connection to extragalactic astronomy. Nimur (talk) 18:53, 2 November 2010 (UTC)

Sure and thats precisely how all the multiverse perpetuators want to keep it. Except extragalactic astronomy is part of our universe, helps us form theories about multiverse, and its relationship to the mulitverse is inseperable. —Preceding unsigned comment added by 165.212.189.187 (talk) 20:22, 2 November 2010 (UTC)

No, I think you are just fundamentally confused on this. MWI is completely incompatible with the idea that the other universes are just galaxies separated by long distances, sorry. --Mr.98 (talk) 00:05, 3 November 2010 (UTC)

See Multiverse for some discussion of this. Short answer: nobody is really sure. They might just be somewhere parallel to us in 3D space (what you mean by "physically" existing, I think), or they might be in some sort of weird quantum space, or something like that. In general this is one of those quantum things that once you've heard it ten times, you say, "oh yes, multiple universes, sure sure," but when you really try to make sense of what it would mean intuitively (e.g. not just with some equations), it becomes pretty clear that it falls outside of everyday human concepts and makes very little sense. That's a limitation of our brains, not to the concept. (I don't know whether the concept makes sense or not — I'm no physicist. But there are lots of quantum things that similarly make very little intuitive sense, yet appear pretty clearly true.)

There is no reason to think that Mother Nature would be conservative with quantum things. It's not a good metaphor to use in this situation, if it ever is good. --Mr.98 (talk) 18:28, 2 November 2010 (UTC)

Other universes would obviously be outside this one, potentially with different rules. Unless someone developes a inter-universe traveling device, we'll probably never know. scientifically speaking, the other universes would probably have to physically exist though some could be figments of imagination too, and would be incorporeal. 70.241.22.82 (talk) 18:51, 2 November 2010 (UTC)

A critical issue here is that "universe-splitting" is not an observable phenomenon in the formal definition of the many-worlds approach. So, philosophical pandering aside, "where are the other universes" is, by definition, an invalid question. There is no observable parameter for them - not an x-position, not a y-position, not a different time, place, or space, where the "other" universe is. "Other universe" represents an effort to use different plain natural language because "collapse" sounds catastrophic. All this boils down to is that the English language is a terrible medium for expressing quantum physics ideas. What we really mean by "many world interpretation" is

$|\mathbf {\psi }$$|\phi \rangle$, where $|\mathbf {\psi }$ refers to the system, and $|\phi \rangle$ refers to the apparatus used to observe it [6].

... and that $\psi$ is a superposition of states. All this nonsense about "interpretation" is little more than philosophical rumination about whether random systems can be causal; and whether causal systems are truly random. If more philosophers would agree on the definition of "random" then there would be no debate about "interpretation." Nimur (talk) 19:10, 2 November 2010 (UTC)

Not sure I agree with you there. Traditional Copenhagen quantum mechanics was incomplete in a pretty definite way: it included a special physical law that applied only to measurement devices, but didn't say what a measurement device was. Therefore, it couldn't predict the behavior of a system that might contain a measurement device. But it was impossible to settle the problem experimentally, because you would have to do something like a double-slit experiment with measuring devices. It's a practical impossibility to do that experiment with anything larger than a small molecule, and Copenhagen adherents can always claim, reasonably enough, that no small molecule is a measurement device. Nevertheless, there was a mathematical hole in the theory, even if it couldn't be tested, and that was the origin of the interpretation problem, I think. It's less clear that there's still an interpretation problem with the modern understanding of measurement, but many people think that the connection between amplitudes and probabilities still needs an explanation (though personally I don't).

(Also, don't you mean 〈φ|ψ〉 where |ψ〉 is the system and 〈φ| the measurement?) -- BenRG (talk) 22:59, 3 November 2010 (UTC)

You also have to define what "universe" means; this is no trivial task as throughout history, what constitutes the universe, even in purely scientific terms, keeps changing. Remember that before Edwin Hubble, it was widely assumed, even within the astronomical world, that the Milky Way Galaxy was the entire universe. Consider how small the Milky Way is in comparison to the observable universe, and it becomes really clear what a revolutionary thing this was. If you define the universe as "the sum-total of all creation", then multiple universes makes no sense. What you end up doing instead is reclassifying the thing we call "the universe" as a different entity, and pushing the limits of what the universe is "outwards", much as what Hubble did. --Jayron32 21:02, 2 November 2010 (UTC)

Does matter outside of the border of the matter resulting from our big bang count as another universe, or is everything that you can get to by three-dimensional travel part of the same universe? —Preceding unsigned comment added by 205.193.96.10 (talk) 20:57, 3 November 2010 (UTC)

As Jayron said, it's a matter of definition. Other galaxies were once called "island universes" (a term introduced by Kant in 1755, according to the Galaxy article). I assume that the current "multiverse" fad will either blow over or become accepted fact, and in the latter case people will start using "universe" for what they're now calling the "multiverse". That "multiverse" is different from both the "worlds" of the many-worlds interpretation and from areas beyond the big bang cosmos. All of those might exist or not, independently. -- BenRG (talk) 02:15, 4 November 2010 (UTC)

Well, thank you for the discussion, everyone. I'm definitely out of my depth here, but this is food for thought nevertheless. Have a nice day, 62.241.87.223 (talk) 21:23, 4 November 2010 (UTC)

Origin of a "love bite"

I cannot find any information on why animals and humans do this affectionate bite. Is it a way of communicating "Look, I could bite you hard, but instead I'm tenderly biting you?" AdbMonkey (talk) 17:16, 2 November 2010 (UTC)

For humans (no idea about animals): because it feels good? Can also indicate (playful or not) dominance, which many people enjoy from one side or the other. → ROUX ₪ 17:17, 2 November 2010 (UTC)

The OP is specifically asking for (presumably expert or at least reliable) information, not just personal speculation... --Mr.98 (talk) 18:18, 2 November 2010 (UTC)

Male cats bite when mating, probably to immobilise and calm the female, and to balance the male. Cuddlyable3 (talk) 18:22, 2 November 2010 (UTC)

All kinds of animals do play bites. Looie496 (talk) 18:37, 2 November 2010 (UTC)

Please add any verifiable information you can find about this to our Love-bite article. DMacks (talk) 18:46, 2 November 2010 (UTC)

Cuddlyable, that was sort of what made me ask this question. My male cat does that to me sometimes when I pet him, and that got me thinking. Anyway, I know it exists among other animals too, but I could not find any info when I searched for it. The results only comes back with vampire literature, from what I've seen. AdbMonkey (talk) 20:13, 2 November 2010 (UTC)

The hickey, or love bite, is just a variation of kiss. The Wikipedia article has a brief section at Kiss#Biology_and_evolution which discusess some of the anthropological research into the purposes of kisses. It's pretty weak, but if you do some off-wiki research into the kiss as a psychological, social, or anthropological phenomenon, you could apply most of what you find to something like the love bite. --Jayron32 20:54, 2 November 2010 (UTC)

See picture no. 5 here. As for the domestic cat, the male (lion) gently bites the back of the female's neck. This is to make the female passive. It is using the natural hard wired instinct of the kitten (and when, adult the cat) to go limp when picked up by the mother by the scruff of the neck to be carried to safety. Other sources[7],[8] (the 2nd source gushes about cat sex). Cuddlyable3 (talk) 19:05, 3 November 2010 (UTC)

Ok, so maybe its just with cats, lions and domesticated animals like dogs, who will gently mouth you when you play with them. Thanks for the info. AdbMonkey (talk) 18:26, 4 November 2010 (UTC)

what chemical gets released when you miss someone?

I know there must be some sort of biochemical that is released in a "flood" if I think the right thought or of the right person (that is no longer around) or hear the right song, the kind that pulls your heartstrings so. I suppose it might be "the nostalgia hormone" (or neurotransmitter) -- at least because there seems to be a strong physiological response. I know oxytocin and vasopressin seems to be involved in pair bonding, but is it these related hormones that get released or is it something else?

Are there any antagonists you can take to suppress this feeling? John Riemann Soong (talk) 18:56, 2 November 2010 (UTC)

C₂H₅OH will take it right away. -Atmoz (talk) 20:48, 2 November 2010 (UTC)

In my experience that's not a very useful antagonist and in fact often exacerbates it and upregulates all emotions (see short term effects of ethanol). John Riemann Soong (talk) 20:50, 2 November 2010 (UTC)

You're meant to take it with company, not while editing Wikipedia. Physchim62 (talk) 22:05, 2 November 2010 (UTC)

I was making a serious scientific inquiry! But...I never drink by myself, seeing how as I am below 21 this usually means I have to rely on others to furnish drinkable EtOH for me. John Riemann Soong (talk) 22:41, 2 November 2010 (UTC)

There are a number of other hormones that are involved in love, in addition to the two you've already mentioned: dopamine, phenylethylamine, adrenaline, and endorphin. I'm getting this from hubpages.com/hub/Hormones-and-love , which I apparently can't link to without triggering a spam trap filter. There's also a more technical article about the chemistry of love here. And at least some of those chemicals (e.g. dopamine) are addictive, so I suspect that missing someone you love might be at least partially due to withdrawal. Red Act (talk) 22:51, 2 November 2010 (UTC)

Yes, but withdrawal is a chronic condition. How would I identify the chemical that gives you that "shiver down your spine" when you have a flood of memories? John Riemann Soong (talk) 23:15, 2 November 2010 (UTC)

Missed one: prolactin, which is tied to dopamine. Red Act (talk) 23:18, 2 November 2010 (UTC)

Chemical basis for love might help point in some right directions, too. Red Act (talk) 23:30, 2 November 2010 (UTC)

The top expert on "separation distress" is Jaak Panksepp, and his book Affective Neuroscience reviews what is known about the system very thoroughly. According to his review, the main agents that increase separation distress are CRF and some types of glutamate receptor agonists. There are a number of agents that strongly reduce separation distress. The ones that have the strongest effects are opiates such as morphine and heroin; oxytocin and prolactin also have potent distress-reducing effects. Looie496 (talk) 17:57, 3 November 2010 (UTC)

crabs

do crabs make sounds, analagous to our speech? how big do they get, and can they regenerate limbs? If so, how long does the latter take? 70.241.22.82 (talk) 19:00, 2 November 2010 (UTC)

Did you try reading crab? (assuming you mean the oceangoing variety, and not the pubichairgoing variety). The section titled "Behaviour" discusses communication methods. Many crabs may regenerate limbs, see Florida stone crab for one famous example, likely most crabs can do this. As far as how big they can get, well, there are hundreds of different species of crabs, but the largest in terms of size and weight is the Japanese spider crab, which can reach up to 12 feet in size from claw tip to claw tip, and can weight up to 40 pounds. --Jayron32 20:50, 2 November 2010 (UTC)

Your crab article must be different to mine, I found it useless! SmartSE (talk) 21:07, 2 November 2010 (UTC)

(edit conflict)Crabs can make sounds, but they are stridulations, rather than vocalisations. The abstract of this paper describes them in Trizopagurus and this does in Hemigrapsus oregonensis in more detail and there are many more examples in the literature. How big they get will depend on the species, but these guys can get up to 3.8 metres! Fiddler crabs can regenerate limbs e.g. but I can't find anything about how long, but it will certainly take at least one moult and maybe more for it to return to its full length. SmartSE (talk) 21:07, 2 November 2010 (UTC)

Ok, thanks! :) 70.241.22.82 (talk) 22:09, 3 November 2010 (UTC)

Microarray cost

How much does a typical microarray experiment cost, supposing you wanted to assess differences in gene expression between two/three/four samples? Are there cheaper versions which assses fewer genes (e.g. genes known or suspected to be involved in muscle growth, maintenance, differentiation etc)? --129.215.47.59 (talk) 20:46, 2 November 2010 (UTC)

• I don't have enough personal experience on the subject to answer the question, but Affymetrix is one of the leading microarray producers. You may get an answer by contacting them (website): [9] Thegreenj 02:52, 4 November 2010 (UTC)

Cartoon physics law break

Remember the classic cartoon where a character walks off the edge and "hangs" in the air before he falls down. My teacher wants me to answer what physics law does this cartoon breaks. Please help! Any clues or hints appreciated!!! --Tyw7  (☎ Contact me! • Contributions)   Changing the world one edit at a time! 20:47, 2 November 2010 (UTC)

When you step off the edge of a cliff yourself, what causes you to fall? Comet Tuttle (talk) 20:48, 2 November 2010 (UTC)

You should learn, and go back to your teacher with, some of the stuff outlined at General Relativity and blow their mind... --Jayron32 20:56, 2 November 2010 (UTC)

This is the actual cartoon: http://img213.imageshack.us/img213/2044/cartoonfall.png --Tyw7  (☎ Contact me! • Contributions)   Changing the world one edit at a time! 21:03, 2 November 2010 (UTC)

As a hint which might help, the law was figured out by Isaac Newton. (Albert Einstein later figured out something that was more accurate.) Red Act (talk) 21:56, 2 November 2010 (UTC)

The cartoon character has weight W which is a force acting on him continuously. When he walks off the cliff he hangs there for a short time. In physics we say his acceleration is zero. Then he suddenly starts falling downwards. In physics we say his acceleration is a and it is non-zero. So for a short time the cartoon character's acceleration is zero, even though the resultant force on him is greater than zero. Which of Newton's Laws of Motion does this violate? Dolphin (t) 21:58, 2 November 2010 (UTC)

What I've noticed in such cartoons is that the character does not begin to fall until he REALIZES that nothing is under his feet. Edison (talk) 22:04, 2 November 2010 (UTC)

Wow, there are actually two different "laws" that Newton came up with, that could to be said to be violated by that cartoon. The "law" I was thinking of wasn't one of the laws of motion. I'm not actually sure which law is the answer the teacher is looking for. I think the answer I was thinking of would be more likely if Tyw7 is younger, and the answer you’re thinking of would be more likely if Tyw7 is older. I don't know what the cutoff age would be. Red Act (talk) 22:22, 2 November 2010 (UTC)

The cartoon character is usually used to teach the laws of motion, and the character breaks two of them. So, the question is: "which ones and WHY?" Physchim62 (talk) 23:02, 2 November 2010 (UTC)

Jeez, I'm just not seeing it. The character violates one of NLM in a very straight-forward way. If it violates another of NLM, it's in a less obvious way. The other law of Newton's that I was thinking of wasn't one of NLM.

However, there is also at least a third valid answer, although I highly doubt it's the one the teacher's looking for. Namely, there's a law by Euler that's closely related to one of the two of Newton's being discussed. I guess this is another one of those cases where the "correct" answer is whatever you've covered in class recently. Red Act (talk) 01:06, 3 November 2010 (UTC)

Try doing a vectorial analysis of the supposed trajectory, and you should see two separate NLM breaches (I can't be more clear because of our homework rules) Physchim62 (talk) 01:28, 3 November 2010 (UTC)

Ah, OK, I see it now. So there are least four physics laws that would be correct answers, assuming the answers haven't been restricted to NLM. Red Act (talk) 02:02, 3 November 2010 (UTC)

It could also be the case that the character is standing on a high-pressure column of air, that had formed and hadn't dissipated yet due to a violation of the Second law of thermodynamics. Or that the air pressure under the character's feet is higher than expected, due to a violation of Boyle's law, or the ideal gas law. Or maybe a temporary violation of Coulomb's law is causing the force due to little charges built up on the character and the earth to be large enough to hold the character away from the earth. I'm sure I could come up with more, especially if I move on to physical laws that don't happen to have the word "law" in their name. Red Act (talk) 08:51, 5 November 2010 (UTC)

Look, there are two laws being violated. break it down into two steps:

1. the character is moving forward at a steady forward pace, he takes what looks like 2 or 3 steps past the edge, stops, then falls straight down. how does he stop when he's moving forward and has nothing to push against to stop himself? what law is that?
2. Again, the character is walking along on the ground without flying off into space on each step (think about how astronauts bounce on the moon). What force is it that holds him on the ground as he walks? When he walks off the edge of the cliff what happens to that force that was holding him to the ground, since the ground is no longer there to be held to?

Think about it. --Ludwigs2 01:39, 3 November 2010 (UTC)

If the planet that the cartoon character was standing on (along with the character himself) was moving up (relative to the character) at a speed of c minus 9.8, then could the character hover in mid air after one second of acceleration to avoid going faster than light? 205.193.96.10 (talk) 16:11, 3 November 2010 (UTC)

No, the relative velocity with respect to the planet would be less than c anyway: a lorentz contraction of length would be the apparent effect, not a period of stationarity. Nimur (talk) 17:20, 3 November 2010 (UTC)

Technically if you've been standing on a solid surface and then suddenly it's gone, you fall in very much the way that Wile E. Coyote does: lower parts first, with the upper parts remaining suspended for a little while. This is because only the soles of your feet are directly supported by the ground; higher parts of your body are supported by lower parts, and it takes a short time for the information that your feet are no longer supported to propagate upward. With the internal pressure supporting your body gone, you also get a little taller when you fall, but initially your body will overshoot that size and get even taller than that, before springing back—again, like Wile E. Coyote. All of these effects are too small/fast to be seen, unfortunately. -- BenRG (talk) 22:23, 3 November 2010 (UTC)

How about if you dropped the supporting floorboard out from under a spring or a slinky? I bet you could make a fun video from that, and make some physicists' heads hurt trying to balance mass flux against a continuously variable spring-constant. Nimur (talk) 00:19, 4 November 2010 (UTC)

Actually, if you managed to make the ground support disappear instantaneously (about the only way you could approximate this in the lab would be to have an iris-type mechanism that opened up a hole by pulling the support sideways in all directions at high speed), then the body would drop as a unit (gravity is simultaneously affecting all portions of the body equally); you'd only see a Wile E. Coyote drop if (a) Wile E. was tall enough so that the top of his head was experiencing a significantly smaller gravitational pull, or (b) the acceleration of the ground away from the feet was slow enough so that the body engages in a reflex effort to maintain position (basically a jump, where the legs kick down trying to push the body up away from the fall). --Ludwigs2 05:10, 4 November 2010 (UTC)

Not really. Within measurable limits, for earth-person type gravity, yes, you should not see any measurable "stretching" associated with the Wile E. Coyote-type fall. However, tidal effects do exist, even if they are below the limit of measurement for this specific scenario. With very large gravitation, you can get measurable effects of this type, see Spaghettification. The effect exists for all gravitational pulls, but is merely insigificant (but not nonexistant) for the scenario describes. --Jayron32 05:21, 4 November 2010 (UTC)

No, even without tidal forces or jumping, your head remains motionless for a nonzero time. Gravity acts on your whole body, but it's already doing that before the ground is removed. All that changes when the ground is removed is the contact force on your feet. The speed at which your neck can learn about the change is limited by the speed of light, and in practice it's the much slower speed of sound in your body. Until then, it has to continue to support your head against gravity just as though the ground was still there. (Also, another way to get rid of the ground "instantaneously" would be to pull it downwards with an initial acceleration larger than 9.8 m/s², although I guess that might run into difficulties with air turbulence.) Nimur, I don't think this will work with a Slinky because the governing speed will be the speed of sound in the metal/plastic that it's made of. I wonder if there is some way to make a visible demonstration of this with some combination of a carefully chosen spring and high-speed photography. Someone must have tried it. -- BenRG (talk) 08:29, 4 November 2010 (UTC)

Hmm surprised no one linked to Cartoon physics yet Nil Einne (talk) 12:07, 4 November 2010 (UTC)

Quail genome?

Is there a publicly-available database of the genome sequence for the quail (ideally Coturnix japonica)? ----Seans Potato Business 21:48, 2 November 2010 (UTC)

I was able to find this but it seems limited to Colinus virginianus at this point. The pubmed abstract (here) suggests that it will be "integrated with Japanese quail (Coturnix coturnix) data in future builds" so maybe there isn't such a thing as a publically-available Coturnix japonica genome yet. Good luck! --- Medical geneticist (talk) 23:19, 2 November 2010 (UTC)

Yeah, there doesn't seem to be anything available at the moment. I managed to find a sequence of interest as coding DNA only and I suppose that will have to do. :) ----Seans Potato Business 17:59, 4 November 2010 (UTC)

Why does high temperature cause distant sights to "blur", and can this be replicated at room temperature?

Greetings.

For years, I've been fascinated by what I've seen at a local pizza place. The pizza oven is about 25 feet behind the counter, and (when I stand in front of the counter) the area surrounding the oven —and everything in it— appears "blurry" and very distorted to me.

What exactly causes this visual phenomenon? Are light particles excited (or even ionized) by high temperatures?

Also, can a similar visual effect be achieved AT ROOM TEMPERATURE through any known means?

--Thank You! Pine (talk) 22:44, 2 November 2010 (UTC)

What you're seeing is a kind of mirage, caused by the hot air from the ovens. To explain it very quickly, the way that light travels through air depends on the temperature of the air: so when you have differences in air temperature over a short distance, you get strange effects.

A similar effect can be created at room temperature, but not easily. You need a large amount of gas that's different from air within your visual field, and that is usually a sign to get the **** out of the place. You can see it sometimes when natural gas is released at a gas well. Physchim62 (talk) 23:13, 2 November 2010 (UTC)

To elaborate the explanation above, the hot air has a different refraction index than the cold air. Because of that light rays will bend a little bit when they move in and out of the hot air area. that causes the image distortions that you observed. 76.123.74.93 (talk) 02:40, 3 November 2010 (UTC)

To attempt an answer to your "also" ... I can't think of any way to reproduce this in air all at room temperature, except by blowing a gas with a different refractive index in a way that produces turbulence in the mixing with air. (later) Sorry, I've just noticed that Physchim62 said that! The temperature effect in air can sometimes be seen on a small scale with domestic fires and radiators, and will be in evidence outside on Friday in some countries. Dbfirs 08:07, 3 November 2010 (UTC)

Is it correct to say that hot air has a different refraction index than the cold air entirely because of the different densities, or does the temperature itself have anything directly to do with it (other than changing the density)? -- 58.147.58.203 (talk) 08:20, 3 November 2010 (UTC)

Several websites claim that "Refractive index is proportional to the square roots of electrical permittivity and magnetic permeability. These factors may change with temperature, but not linearly, and therefore RI does not have a simple relationship with temperature." so I suspect that hot air at the same density (from greater pressure) will have a marginally different RI from cold air at the same density. This difference will be swamped by the difference in density at normal pressure. Dbfirs 08:35, 3 November 2010 (UTC)

I'm not sure if this counts as "room temperature" but if you light a candle you may be able to see the same phenomena just above the flame. 92.15.0.194 (talk) 14:37, 3 November 2010 (UTC)

Obviously that does not count as room temperature. Put your hand on the flame for a few seconds and you will agree with me. 67.78.137.62 (talk) 15:02, 3 November 2010 (UTC)

That depends upon how the OP defines room temperature. 92.24.178.95 (talk) 17:38, 3 November 2010 (UTC)

If you observe over a much larger distance (say, looking across a large valley), you can see thermal "shivering" effects that are due to minute temperature variations (a few degrees, say), but because the lengths are much longer, the refraction can be visible. And if you are into astronomy, you can see atmospheric twinkling - a type of scintillation - due to vertical thermal gradients and inhomogeneity in the atmosphere. Nimur (talk) 17:24, 3 November 2010 (UTC)

Relationship between octane rating & emission levels

Consider two identical cars, one using low octane gasoline, the other high octane. Same driving conditions. Does one car create less emissions than the other? Thanks, CBHA (talk) 22:56, 2 November 2010 (UTC)

Does not quite work like that. One could have a large megawatt, electrical generator, running on natural methane with a 14:1 compression ratio, producing a very clean CO2, water vapour, nitrogen exhaust. Or a high compression ratio, in WWII fighter aircraft, sports car, racing car, all with short stroke engines and the exhaust can be very, very dirty.--Aspro (talk) 23:28, 2 November 2010 (UTC)

Okay. But suppose the cars are conventional mass-produced cars (not racing cars, fighter aircraft, or stationary generators) running on the grades of gasoline that are generally available (say octane # 91 and octane # 87.) CBHA (talk) 00:46, 3 November 2010 (UTC)

Makes no difference. Either you need the octane or you don't. If you need it and you don't use it the car knocks. If you don't need it and you use it, it does nothing at all. Ariel. (talk) 00:55, 3 November 2010 (UTC)

I've seen suggested (but do not have a source offhand) that using fuel with an octane rating higher than recommended can result in incomplete combustion. In either case, using incorrect fuel cannot improve your engine's performance or its emissions, and may be detrimental to both. — Lomn 01:42, 3 November 2010 (UTC)

I've noticed that most filling stations near where I live (UK) supply only 95 (RON) (equivalent to 90–91 US AKI). I presume that all British cars are now built and tuned to this octane fuel rating. Some modern engines have sensors that detect knocking and adjust the timing. They are not designed to adjust to the octane rating, but might have that effect to a limited extent. There seems to be lots of opinion on the web about higher octane possibly providing more power or better fuel consumption, or possibly helping to burn out exhaust valve seats because of late burn. Is all of it just uninformed speculation? I'm inclined to agree with Aspro, Ariel & Lomn above. The manufacturers spend millions of pounds in developing and testing their engines, and in reducing emissions to meet regulations (and reduce road tax in the UK). Their recommendations are likely to be the optimum for that engine. Dbfirs 14:00, 3 November 2010 (UTC)

Lomn, see Tetraethyllead which is still sometimes added to increase the octane of gasoline (petrol) but also adds to lead pollution. Cuddlyable3 (talk) 14:05, 3 November 2010 (UTC)

Dbfirs - There are a select few specialist garages (http://www.petrolprices.com/about-fuel.html) selling the old 4 star leaded fuel (98 RON) for "classic cars" - at a price! Everybody else has to use the single unleaded 95 - or diesel, which I guess is >40% of cars here now - due to far better consumption rate - I get easy 50+ per gallon (2L Ford Mondao).  Ronhjones  ^(Talk) 23:11, 3 November 2010 (UTC)

Thanks, Ron. Fortunately, I don't need old 4-star (because I can't afford to run a classic car). I envy you your fuel consumption figure. Can you achieve that rate consistently over time (including short runs, manoeuvres etc.) or only on a long run? Dbfirs 08:56, 4 November 2010 (UTC)

From discussion in a vintage car club I gather that valve seats in older cars wear badly if run without leaded fuel. Separate additives for unleaded fuel are available. Cuddlyable3 (talk) 08:31, 4 November 2010 (UTC)

Which animals are truely monogamous?

I've read that in nature, true monogamy is very rare and that even in species that tend to pair up for life, 'affairs' and side-pairings are common. Could you tell me some of the few species that are 100% monogamous? I think that the Peach-faced Lovebird is one of them. --95.148.105.15 (talk) 23:50, 2 November 2010 (UTC)

Photocorynus spiniceps --Dr Dima (talk) 01:55, 3 November 2010 (UTC)

Are humans truly monogamous? "Affairs" and side-pairings are very common in human societies too. --99.237.232.254 (talk) 02:11, 3 November 2010 (UTC)

No one said they were. The Masked Booby (talk) 02:24, 3 November 2010 (UTC)

I was wondering if, by the OP's criteria, humans would be considered truly monogamous. --99.237.232.254 (talk) 06:00, 3 November 2010 (UTC)

I would say the answer is clearly no, in fact we're probably less monogamous then many of the common animal examples on average. However you do have a point it's not clear if the OP is aware of that. Nil Einne (talk) 06:04, 3 November 2010 (UTC)

Bald Eagles are monogamous, with the following caveats mentioned in their article: It is thought that Bald Eagles mate for life. However, if one member of a pair dies or disappears, the other will choose a new mate. A pair which has repeatedly failed in breeding attempts may split and look for new mates. Seems reasonable to me. The Masked Booby (talk) 02:24, 3 November 2010 (UTC)

I don't know if that would rule out 'affairs'. Very often animals which appear to mate for life are found to mate with other partners on the sly (this can sometimes be difficult to observe but the recent advances in genetic analysis making paternity or parentage testing easy have shared a lot of light in this area including with the animal we discussed above before TMB's comment), and this includes both sexes. However [10] found a high degree of fidelity in another species of eagle (by analysing DNA from feathers). On the other hand [11] claims recent research suggests that it may not be true but doesn't mention how so or what research nor even what it means by 'recent'. Prairie Vole are another common 'icon' of monogamy and studied for how they are adapted for it [12] but our article mentions they aren't always sexually faithful. Back to birds, [13] suggests low instances of extrapair copulation and extrapair parentage may be more common among isolated island populations where the genetic variation is low. Nil Einne (talk) 06:01, 3 November 2010 (UTC)

As far as I am aware, the European Herring Gull is mostly monogamous (a percentage of individuals aren't) - and often pairs up for life, though if one parter dies, the other will attempt to find another mate. Are there actually any non-human animals that will never pair up again if their chosen mate dies? I've never heard of any. Even Lovebirds will do this. It's a myth that if one dies, the other will die shortly after through loneliness/a broken heart (na, they just go find another partner when the breeding season comes round again). --Kurt Shaped Box (talk) 14:05, 3 November 2010 (UTC)

If you are looking for a species in which 100% of males mate with exactly zero or one female in their lifetimes (and vice-versa), such a thing simply does not exist. In species that display Pair_bonding there are always exceptions and 'affairs', such as the OP suggested. You may enjoy the book mentioned in our article called The Myth of Monogamy. Also a recent book covering human monogamy and evolution is getting some attention, it's called Sex_at_Dawn. Essentially, though pair-bonding and monogamy can be evolutionarily favorable for some species, it is unexpected to find any behaviour displayed by 100% of individuals. SemanticMantis (talk) 15:43, 3 November 2010 (UTC)

The best possibilities I would see to fulfill the monogamous qualifications would perhaps be insects that do not live long enough to mate more then once. Googlemeister (talk) 15:52, 3 November 2010 (UTC)

I was thinking of mayflies is response to the original question but, even then, it's hard to be certain. Many insect species will usually only mate once in their entire lifetime, but you can get occasional behaviour where a female will mate with more than one male: it is to be expected in evolutionary terms, as long as the resource cost isn't too high, as it effectively "hedges her bets" on the genetic quality of her offspring. Physchim62 (talk) 16:02, 3 November 2010 (UTC)

Yes, I was thinking along the same lines e.g. male ants mate zero or once so the males are monogamous (although queens of many species mate more than once)...so, semi-monogamous-ish. Sean.hoyland - talk 16:12, 3 November 2010 (UTC)

Good point Sean, I think most drones die after first copulation. Though males of obligate Semelparous species are likely to mate with zero or one females, the females of such species tend to have multiple mates. And of course, a queen being inseminated by multiple males (in the same day) after which the males all die is probably far from most notions of 'monogamy' ;) SemanticMantis (talk) 17:29, 3 November 2010 (UTC)

See Monogamous pairing in animals. -- Wavelength (talk) 22:46, 4 November 2010 (UTC)

Do people really eat spiders in their sleep?

(2) What's with the "on average people eat X number of spiders during sleep"? Do spiders climb into their mouth? Dont you die after eating raw spider? Thanks Money is tight (talk) 02:58, 8 November 2010 (UTC)

According to Snopes, no. --- cymru lass ^{(hit me up)}⁄_{(background check)} 03:40, 8 November 2010 (UTC)

Also, I don't think you die after eating raw spider. In fact, many people around the world eat insects as food. TomorrowTime (talk) 07:31, 8 November 2010 (UTC)

I recall a National Geographic program where they were in a South American jungle, where the spiders are quite large. Natives would capture them, roast them alive, and eat the meat from the legs, like you would with crab. The roasted arachnid meat was said to taste like shrimp. As far as dying, most house spiders are mostly harmless. If a seriously venomous spider such as a black widow or a brown recluse got into your mouth and managed to inject some venom, that could be trouble. But cats, for example, will attack common house spiders and eat them, with no apparent damage. ←Baseball Bugs ^{What's up, Doc?} carrots→ 08:54, 8 November 2010 (UTC)

This is entertainment..... ??!! Ghmyrtle (talk) 09:01, 8 November 2010 (UTC)

Theoretically, you'd be in greater danger from swallowing a fly, considering where they spend much of their short existence. And for the entertainment part of this, please rise and join us in singing, "There Was an Old Lady Who Swallowed a Fly". ←Baseball Bugs ^{What's up, Doc?} carrots→ 09:03, 8 November 2010 (UTC)

She did swallow a spider too[14] (with the aim of catching the fly) but an unpleasant side-affect was internal wriggling, wiggling and tiggling. Whether these are recognised medical conditions, I don't know. Alansplodge (talk) 13:18, 8 November 2010 (UTC).

Yes. It seems likely that the critter would quickly be smothered by various internal fluids, so it wouldn't get to do much wriggling and wiggling and tickling. ←Baseball Bugs ^{What's up, Doc?} carrots→ 13:23, 8 November 2010 (UTC)

The bovine and equine stages of the therapy seem a bit unlikely too. Should have a "citation needed" tag. Alansplodge (talk) 17:12, 8 November 2010 (UTC)

Having a local environment made up of hydrochloric acid, enzymes and the like would probably limit the wriggling and tiggling in favor of dying and dissolving fairly promptly. FT2 ^{(Talk | email)} 19:09, 8 November 2010 (UTC)

The Straight Dope handles the question here. APL (talk) 20:46, 8 November 2010 (UTC)

Cecil is using logic and reasoning, whereas Snopes (listed earlier) claims to have found the source of the urban legend. Between the two, it seems like the question has been solidly answered. ←Baseball Bugs ^{What's up, Doc?} carrots→ 20:51, 8 November 2010 (UTC)

Additional information about bees not directly related to the OPs question

If she would have swalloed a bee or wasp or any other related incect, she would have suffered sever stings, because the stinger would poke the stomach walls while in digestion. What do you guys think would happen if she swallowed a bee or wasp? As for spiders, I accidentaly ate one, i threw up. I guess some people's systems don't get along with spiders, doesn't mean they are unsafe to eat. I'm not saying go eat a spider, i'm saying. Definately don't eat a bee, or even a spruice beedle. People have consumed incects in the past, either for survival if they were lost or something, for sport, or even for dair. I don't think people eat incects in their sleep. It's not a good idea though, as the incects could have paracites and other diseases on them that could be harmful to the body. And incects such as bees like i said above, can really hurt your digestive system. 204.112.104.172 14:14, 11 November 2010 (UTC)

November 3

Time dilation? Time speeding?

The beginning of the section of {Time dilation and length contraction} under Special Relativity is confusing to me. Hope someone can help. It states:

See also: Twin paradox

Writing the Lorentz transformation and its inverse in terms of coordinate differences, where for instance one event has coordinates (x1,t1) and (x'1,t'1), another event has coordinates (x2,t2) and (x'2,t'2), and the differences are defined as Δx = x2 − x1, Δt = t2 − t1, Δx' = x'2 − x'1, Δt' = t'2 − t'1 , we get

△t’=γ(△t-(v△x/c^2)) △x’=γ(△x-v△t) and △t=γ(△t’+(v△x’/c^2)) △x=γ(△x’+v△t’)

Suppose we have a clock at rest in the unprimed system S. Two consecutive ticks of this clock are then characterized by Δx = 0. If we want to know the relation between the times between these ticks as measured in both systems, we can use the first equation and find: △t’=γ△t (for events satisfying Δx = 0). This shows that the time Δt' between the two ticks as seen in the 'moving' frame S' is larger than the time Δt between these ticks as measured in the rest frame of the clock. This phenomenon is called time dilation.

I am confused by the last two sentences. To explain △t’=γ△t in more detail, we can assume the unit time in S is Ut and in S' is Ut', then the time of the {two consecutive ticks event} measured in S is △t*Ut=(t2-t1)Ut, the t2-t1 can be 1; while measured in the S' is △t'*Ut'=(t'2-t'1)Ut', the t'2-t'1 may not be 1. Since they are for the same event, we have △t*Ut=△t'*Ut', then, put △t’=γ△t in it, we have Ut=γUt', that means the clock in S' is running quicker than the clock in S. This phenomenon should be called time speeding, isn't it?

When Einstein used x'=0 to derive t’=t/γ, so that △t’=△t/γ, we have time dilation; how can we call △t’=γ△t as time dilation too? Please help me to understand that paragraph. Thanks.

Regards, John HuangJh17710 (talk) 04:53, 3 November 2010 (UTC)

Relativity of simultaneity actually has some nice, non-mathematical, explanations of the problem. If there are any two events, seperated by some arbitrary distance, which are perceived in one reference frame to occur at the same time, there will exist other reference frames which perceive them not to be simultaneous, some in which one event occurs first, and some in which the other event occurs first. This perception is dependent not only on the location of the reference frames but on their relative motion to each other. In other words, for your problem, lets assume that you and I are moving relative to one another. If we both start our stop watches at what we perceive at the same time, there will exist three different classes of reference frames relative to us:

• Some will perceive our clocks to run at the same speed.
• Some will perceive your clock to run faster than mine
• Some will perceive my clock to run faster than yours

That's the key problem with Special Relativity, there is no reference frame which is "right". All are equally valid. By convention, we hold the reference frame of the designated observer to be "stationary" and measure time changes relative to that one; thus since everyone else is moving relative to THAT observer, everyone elses clock is running a little bit slower. But this convention holds regardless of who you choose as the observer. If two spaceships are moving away from each other at some fraction of c, but each is in communication with the other, each will perceive the other's clock to be slowed down. If they then, at some later time, change speeds to be stationary relative to each other, the perception of which clock slowed down will depend on which ship had to speed up or slow down to "match speeds". If the two ships performed identical, mirror image paths and speed changes, then the clocks will match when they reach the same relative motion. If one ship decelerated while the other maintained a constant speed, you will get different results. Special_relativity#Lack_of_an_absolute_reference_frame and Consequences of special relativity also discusses some of this. --Jayron32 05:34, 3 November 2010 (UTC)

The OP is makingn a crucial mistake. He states "Since they are for the same event, we have △t*Ut=△t'*Ut'". That's wrong. In fact both observers will be using similarly constructed clocks which will be using the same time unit, say a second: Ut=Ut'= 1 second.67.78.137.62 (talk) 15:22, 3 November 2010 (UTC)

Yeah, the phrase "time dilation" is potentially confusing, because that phrase by itself doesn't do a great job of helping you remember which observer will measure a greater amount of time between two events under which circumstances. Fortunately, there's another phrase that expresses the time dilation phenomenon that's more helpful in that regard, namely "moving clocks run slow". That phrase is particularly useful if you think of a "clock" as being a light pulse bouncing between two mirrors, as described at time dilation#Simple inference of time dilation due to relative velocity. In this case, the clock in question is stationary in the unprimed system, so it's moving from the perspective of the primed system. Therefore, the "seconds" as ticked out by the clock in question will appear to be longer than a "real" second, according to the primed observer. That's time dilation.

The reason you're thinking of this problem as being a "time speeding" is essentially because you're thinking that the clock in the primed system that's measuring the time between the two events in question is running faster than it ought to, as considered from the perspective of the unprimed observer. The crucial flaw in that line of reasoning is that there is no such clock in the primed system.

You're making the mistake of thinking that there's a clock in the unprimed system that measures the time of events in the unprimed system, and a clock in the primed system that measures the time of events in the primed system. But the time of events can't be accurately measured that way. Because the speed of light is finite, trying to measure the time of all events with one clock would run into the problem of there having to be a delay between when an event occurs, and when news about the event reaches the clock, informing the clock to measure the current time. You might think you could just take the time delay into account, but that would involve needing to know the distance that the light traveled in between the event and the clock, which opens up a whole other can of worms. So what's done instead is that times of events are measured by a system of synchronized clocks, stationed at every location of interest. It is possible to synchronize a system of clocks, as long as all of the clocks in the system are stationary with respect to each other. However, to an observer that's moving with respect to those clocks, the clocks won't appear to be properly synchronized.

In the problem in question, the two events involved can indeed be measured by a single clock that's stationary in the unprimed system, because the two events occur at the same location as measured by the unprimed observer. However, the two events are not at the same location as measured by the primed observer, so the primed observer, who measures events with clocks that are stationary with respect to the primed observer, must measure the two events with two different clocks. The reason the unprimed observer thinks that the primed observer measured too much time in between the two events is not at all because the unprimed observer thinks that the primed observer's clocks are running too fast. Indeed, the unprimed observer will think that the primed observer's clocks are running too slow. Instead, the unprimed observer will consider the primed observer to have measured too much time between the two events because the primed observer's clocks aren't properly synchronized. Red Act (talk) 18:37, 3 November 2010 (UTC)

Heart muscles

• What property of the heart muscles are exploited in the heart transplant?
• In blood groups,why is it imposible for one individual to carry all 3 alleles?
• why is the oxygen dissociation curves of animals living at high altitudes located to the left of most of those of other animals?

— Preceding unsigned comment added by 196.0.7.4 (talk • contribs)

Hmm, these look suspiciously like homework questions. Try reading "Heart", particularly the "Functioning" section. Axl ¤ [Talk] 10:41, 3 November 2010 (UTC)

"ABO blood group system", section "Inheritance". Axl ¤ [Talk] 10:44, 3 November 2010 (UTC)

"Oxygen-haemoglobin dissociation curve", section "Factors that affect the standard dissociation curve", will point you in the right direction, although it does not contain the answer that you seek. Axl ¤ [Talk] 10:50, 3 November 2010 (UTC)

Well an individual could carry all 3 groups if they were triploid... 128.143.170.201 (talk) 19:26, 3 November 2010 (UTC)

...or is a Chimera (genetics). DMacks (talk) 01:23, 5 November 2010 (UTC)

The proportion of swine flu to all flues

Of those people having flu in late 2009 in the UK, what proportion of them would have had swine flu, diagnosed or not? 2009 flu pandemic. Thanks 92.24.178.95 (talk) 18:41, 3 November 2010 (UTC)

It's a bit vague ('late 2009') yet also specific (UK). Not sure of that exactly. If it's any help the WHO Centre on Influenza in Melbourne says 90% of flu viruses in Australia and NZ in 2010 were H1N1 2009. The WHO influenza page may hold the information somewhere, but I could only see data going back for this year - the map there for January 2010 for example indicates about 80-90% of flu cases in Western Europe were H1N1 2009, but it doesn't seem to refine down to countries. The European influenza section of the WHO site may contain some information, as may the WHO Global Atlas of Infectious diseases, but that seems to want a login. --jjron (talk) 02:33, 4 November 2010 (UTC)

limestone make-up and other soft stone

(Copied from the Earth Portal's talk page)

I don't know if this will reach anyone but am going to try anyway. I am an authenticator of North American Indian artifacts. I have been sent several items recently by a man that are no brainers to identify but have one really odd piece that I have not come accross before. It is a statuette of an Aztec or Central Amer. pre-columbian art. It appears to me to be Peperino Tuff. Whis is not from this hemisphere I don't believe. More likely Italy. My question is, could I be mistaking this for some sort of Limestone. Under high powered magnification it shows fine crystal like clusters covering the surface with isolated black pepper like crystal inclusions. It also appears to have a pinkish hue deep with-in the stone. It is porous with a conglomerate look to it. It also has a slight sodium taste to it when touching your tounge to it. Can anyone help itentify this stone type??? How long does it normally take to get a response for questions? Many thanks, Bob 11/03/10 —Preceding unsigned comment added by 74.197.184.126 (talk) 18:51, 3 November 2010 (UTC)

Your description sounds very similar to that in our Peperino article (which needs to be merged with our peperite article I see) and much less like a limestone, but note that that rock does contain fragments of limestone. Peperites are found all over the world however, Nigeria, Spain, Wales, France, Italy, California, Australia, Argentina, Canada, Chile, Japan, Antarctica, Kenya, South Africa, Scotland (just a quick selection from [15]), so it may not tell you much about provinance. Mikenorton (talk) 21:21, 3 November 2010 (UTC)

If you want more confirmation, maybe try contacting one of these geologists at your local university (I worked that out from checking where your IP locates). If you register an account here and take a photograph of the piece and upload it, then someone may be able to help further as well. SmartSE (talk) 11:52, 4 November 2010 (UTC)

if the moon and moon landings are real

why didn't they run around the moon to prove it is a sphere and not a disc like it looks? 85.181.145.78 (talk) 08:58, 3 November 2010 (UTC)

We can observe 59% of the moon's surface, thus it is not a disk Tidal_locking#Earth.27s_Moon. Also there have been plenty of satellites (inclusing the moon landers themselves) that orbited the moon, observing it completely. See e.g. SELENE. Furthermore, the moon is simply too large to run around, especially with a limited oxygen supply. 157.193.175.207 (talk) 09:28, 3 November 2010 (UTC)

To put it in context, the equatorial circumference of the moon is 10,921 kilometres (6,786 mi). Ghmyrtle (talk) 09:35, 3 November 2010 (UTC)

The Apollo rover had a top-speed of 18 miles per hour (29 km/h), and a range of 57 miles (92 km). IIRC, NASA didn't want the rovers to go out of walking-distance of the lander, incase they broke down. CS Miller (talk) 09:52, 3 November 2010 (UTC)

The following is imported from a duplicate question

It's rather a long way! They did fly round it - will that not suffice to convince you? (later) sorry edit conflict. The much better answer above wasn't there when I started to edit. Dbfirs 09:31, 3 November 2010 (UTC)

See Apollo 10. BTW that also confirmed that the Earth is (roughly) a sphere in case you doubt that too. Cuddlyable3 (talk) 13:38, 3 November 2010 (UTC)

Actually Apollo 8 of 1968 was the first mission in which humans circled the Moon and observed its far side; and, a decade previously, the Soviet Luna 3 mission of 1959 was the first probe to circle the Moon and send us photos of the far side. Comet Tuttle (talk) 17:17, 3 November 2010 (UTC)

Besides, the nature of lunar phases is sufficient to demonstrate that the moon is spherical. This has been understood for thousands of years. — Lomn 13:42, 3 November 2010 (UTC)

In other words, the moon doesn't look like a disc. Simple observation of the moon with the naked eye makes it abundantly clear that it is nearly spherical. Nimur (talk) 15:42, 3 November 2010 (UTC)

Trolling questions are best ignored. Looie496 (talk) 17:41, 3 November 2010 (UTC)

Observe this film animation of the Libration of the Moon and ask yourself whether a flat disk could do that. Cuddlyable3 (talk) 21:30, 3 November 2010 (UTC) I restored the question, see Talk page.Cuddlyable3 (talk) 21:30, 3 November 2010 (UTC)

Technically, that's not a film, it is a simulation generated from composite texture photographs by Clementine (spacecraft) (you can plainly see the orbit-track artifacts!) But the point stands. Careful long-term observation of the moon with the naked eye reveals exactly the same behavior. Moon enthusiasts regularly photograph this behavior. Nimur (talk) 21:43, 3 November 2010 (UTC)

Thank you Nimur for the correction. The animation is for a theoretical observer at the center of the Earth.Cuddlyable3 (talk) 08:03, 4 November 2010 (UTC)

Why does the moon get larger and and smaller in that animation? Does the apparent size from earth change that way over a month? Ariel. (talk) 22:28, 3 November 2010 (UTC)

Yes. As you can see in the infobox at Moon, the apparent angular size of Moon as observed from Earth fluctuates between about 29.3 to 34.1 arc-minutes - a visible difference of around 20% ! This is because its orbit, while "nearly" circular, actually has a perigee of 360,000 km and an apogee of 400,000 km - a pretty huge difference! Nimur (talk) 22:31, 3 November 2010 (UTC)

Why on earth would they run around the moon? That is very nearly the most useless thing they could do with their brief and incredibly expensive time on the moon. And it wouldn't have occurred to them that anyone would doubt that they were there. -FisherQueen (talk · contribs) 22:35, 3 November 2010 (UTC)

If they had "run around the moon", why would any of the moon-landing-deniers believe them?! I can't see why that would be "proof" of anything to anyone for whom their having orbited around the moon isn't "proof" of anything. Do you really think that would have "proven" to you that the moon is a sphere[oid], OP...? WikiDao ☯ (talk) 01:12, 4 November 2010 (UTC)

The OP's question caused some initial confusion because its premise "if the moon and moon landings are real" has nothing to do with the real question and instead provokes some to think this is about Moon landing conspiracy theories. The question itself is reasonable because (i) the full Moon looks disc-like because of its even illuimination, and (ii) until the late 1950s the Far side of the Moon was an unseen mystery. On October 7, 1959 the Soviet probe Luna 3 did indeed "run around the Moon" and took the first photographs of the lunar far side. Comet Tuttle already mentioned this. 08:20, 4 November 2010 (UTC)Cuddlyable3 (talk)

A flat-Earther would point out that a single circumnavigation will not prove that the Moon is a sphere. You've got to circumnavigate it longitudinally and latitudinally. That would be a lot of running. APL (talk) 14:30, 4 November 2010 (UTC)

And people have circled the earth and the flat-earth people don't believe them, so I don't see circling the moon as convincing to people dedicated to believing the moon landings were a conspiracy. Googlemeister (talk) 14:34, 4 November 2010 (UTC)

They have an explanation for longitudinal circumnavigation of a flat Earth, but if someone flew from South America to Australia via the south pole, then their theory would be in trouble. —Arctic Gnome (talk • contribs) 16:14, 4 November 2010 (UTC)

November 4

emissivity

physical meaning of emissivity —Preceding unsigned comment added by Quiet.mp (talk • contribs) 02:15, 4 November 2010 (UTC)

See Emissivity. -- kainaw™ 02:18, 4 November 2010 (UTC)

Chemistry

What substance melts at Negitive 97 degrees and boils at 76 degrees? —Preceding unsigned comment added by 67.182.212.131 (talk) 03:34, 4 November 2010 (UTC)

Seems like that might depend on whether you mean degrees Celsius, Fahrenheit, etc. DMacks (talk) 03:36, 4 November 2010 (UTC)

Regardless of which temperature scale you use, there are likely to be hundreds of substances which broadly meet these requirements. Given the millions and millions of possible substances in existance, it is quite impossible to identify a substance given only those two bits of info. --Jayron32 03:38, 4 November 2010 (UTC)

See acetyl bromide for a common substance with those specific melting/boiling points (within 1 degree). -- kainaw™ 03:43, 4 November 2010 (UTC)

Why isn't the acetyl bromide boiling point a sharp point? Is it because there are actually multiple species upon boiling, or that there are different microphases? John Riemann Soong (talk) 04:01, 4 November 2010 (UTC)

Probably because no one has bothered to measure the boiling point any more specifically. If you want to get an exact boiling point (where vapor pressure = 1 atm), you're going to need to control both the temperature and pressure pretty well. Anyway, my CRC handbook gives 76 C. Buddy431 (talk) 04:32, 4 November 2010 (UTC)

Just to explain in a bit more detail, while melting point is usually vital information for identifing a compound (melting point analysis is usually a standard analytical technique for identifying both identity and purity of a compound), boiling point usually is not, being that boiling point tends to be had to control for, as it will vary slightly due to a LOT of different factors. So, while someone could nail down a more exact boiling point (equipment and standard techniques do exist for this) they may not have, at least in the literature used as a reference for the Wikipedia article. --Jayron32 05:06, 4 November 2010 (UTC)

Is this slightly harder (than for say, water) because of the tendency of acyl chlorides to be impure? John Riemann Soong (talk) 06:34, 4 November 2010 (UTC)

Autoclave naming

Autoclave means self-locking device. But why did they get this name? It seem to me they got named after an insignificant feature compared to their general purpose. —Preceding unsigned comment added by Jib-boom (talk • contribs) 04:39, 4 November 2010 (UTC)

I guess that the self locking devices to prevent blow-out on the early pressurised autoclaves were unusual enough for it to be included in the name of the machine. Perhaps something like "Modern Autoclave Sterilising Machine. Like all new words 'autoclave' became the significant part of the name and possibly it became 'The Autoclave', with the purpose now well known. The English language is a strange and infinitely mutatable medium. There are many examples of names that have left their original meanings back in the mists of obscurity. ?Chauffeur,[16] for example. Caesar's Daddy (talk) 07:48, 4 November 2010 (UTC)

See google books: The London literary gazette and journal of belles lettres.. the name was invented by fr:Pierre-Alexandre Lemare, ironically a linguist.213.249.225.56 (talk) 11:52, 4 November 2010 (UTC)

His linguistic skills may have been a bit week as "auto" is Greek and "clavis" is Latin. Further, "self-lock" (using his Greek-Latin system) would be something more like "autoclaus", which my personal limited Latin knowledge tells me is close to meaning "self-contained". -- kainaw™ 12:18, 4 November 2010 (UTC)

Just like the French and German mix in the "YesYes" board game -- Sjschen (talk) 19:45, 4 November 2010 (UTC)

So if it sanitizes would it be a "saniticlaus?" Edison (talk) 18:31, 4 November 2010 (UTC)

There ain't no saniticlause! APL (talk) 13:04, 5 November 2010 (UTC)

Escape Trajectory

I understand an orbiting mass around a larger mass can be pulled into a escape trajectory by a passing mass. But what would be the simplest trajectory that would illustrate this interaction?

Just to clarify with an example: what would the trajectory of the Moon following its last orbit around the Earth look like if a planet size mass passed by and pulled the moon into an escape trajectory, avoiding a collision with both bodies? TheFutureAwaits (talk) 09:16, 4 November 2010 (UTC)

Even if we ignore the gravitation of the Sun, what you ask is a Three-body problem. They can be difficult. Cuddlyable3 (talk) 10:48, 4 November 2010 (UTC)

Sure but we know there are solutions that involve putting a mass into an escape trajectory...I'm just asking what the simplest case would be? It's really just the opposite of a capture trajectory which involves a moving mass passing near another mass at hyberbolic speeds when a 3rd body removes enough velocity through its own gravity to reduce the eccentricity <1. For seem reason I have a much harder time visualizing the reverse... TheFutureAwaits (talk) 11:34, 4 November 2010 (UTC)

Newtonian gravity is time symmetric. So, if you can visualise the geometry of a capture trajectory, just run the film backwards to visualise an escape trajectory. Gandalf61 (talk) 11:40, 4 November 2010 (UTC)

But the starting condition in this case has one body already "captured" by another. I think TFA is imagining eg. the moon being "captured" from the earth by a third body? So running that backwards gives you another "capture", not the case where all three bodies gravitationally escape each other. WikiDao ☯ (talk) 16:12, 4 November 2010 (UTC)

Tropical Laserbeam

If I were to take a green laster pointer and point it at the night sky will some of its light make it out of the atmosphere? What about if I use a red or blue laser pointer? Or a flashlight? TheFutureAwaits (talk) 12:38, 4 November 2010 (UTC)

Unless it is cloudy at least a few of the photons should be able to make it out into space, but unless it is a very powerful light, you would not really be able to differentiate those photons from other light "clutter". The atmosphere is pretty transparent to the visible portion of the EM spectrum. Heavy airborne pollution or dust would limit the amount escaping, but without anything to absorb the light or bend it back to earth, it will go into space. Googlemeister (talk) 13:15, 4 November 2010 (UTC)

Lasers are used to precisely measure the Earth-Moon distance, so clearly they can make it out of the atmosphere (and back); see Lunar Laser Ranging experiment. Sure these are not just your garden variety laser pointers though, but as Googlemeister says, undoubtedly some the photons from those would escape as well. The article linked above states that "...out of 10¹⁷ photons aimed at the reflector [on the moon], only one will be received back on Earth every few seconds, even under good conditions (they can be identified as originating from the laser because the laser is highly monochromatic)." --jjron (talk) 13:37, 4 November 2010 (UTC)

(ec)To avoid confusion, it should be noted that the reason so few photons return is not because so few make it out of the atmosphere, but because the the diameter of the laser beam will be very large by the time it hits the Moon (kilometers across). Most of the photons which reach the Moon strike the lunar surface instead of the retroreflector; similarly, most of the photons that do get reflected back end up spread over the Earth's surface rather than entering the (comparatively) small aperture of the receiving telescope. I wouldn't be surprised if the answer to the original poster's question is actually "most of the light makes it out of the atmosphere" — provided that it isn't cloudy. TenOfAllTrades(talk) 14:14, 4 November 2010 (UTC)

Here is a simple thought experiment: The laser pointer, or flashlight, or torch in your hand appears much brighter than Sirius. Light from Sirius easily makes it through the atmosphere, so light from your local device will make it up, too. In numbers, Sirius puts out about 10²⁸W. Your local light source puts out ~1W. Sirius is about 80228200000000000 times farther away that the flashlight (2.6 parsec vs. 1 m), so it appears 6.4e+33 times fainter than it would at one meter. So Sirius is ~60000 times fainter than you local light, and still is clearly visible through the atmosphere. --Stephan Schulz (talk) 14:03, 4 November 2010 (UTC)

Sirius is spreading light in all directions, while the laser sends all it's light down a narrow path, so I don't think your math works out that easily. Googlemeister (talk) 14:32, 4 November 2010 (UTC)

You are right, but the laser light is just as attenuated by 1/r² as Sirius. So yes, we lose a small constant factor because we do not see the backside of Sirius, but that's a minor effect. --Stephan Schulz (talk) 14:48, 4 November 2010 (UTC)

I am not sure that you mean attenuation because (a) that only happens in a medium, not in a vacuum and (b) it follows an exponential law. Are you saying that the intensity of a laser beam in a vacuum decreases as 1/r² ? I find that hard to understand. I can see there would be a some fall-off in intensity with distance due to a small amount of beam spreading, but I don't see how it could be anything near 1/r². Gandalf61 (talk) 15:52, 4 November 2010 (UTC)

Well, there's nothing out there focusing the beam, so the sides of the beam form straight lines, so the diameter of the beam is proportional to r, so the area of the beam is proportional to r², so the intensity of the beam is proportional to 1/r². Red Act (talk) 16:12, 4 November 2010 (UTC)

But the beam has already been focussed - it doesn't need continual refocussing. If the sides of the beam are almost parallel then your r is not the distance from the source - in effect, r is the distance from a "virtual" source, a long way behind the real source, where the sides of the beam would meet if projected backwards. Gandalf61 (talk) 16:48, 4 November 2010 (UTC)

That is true, but only important if r is of the same order of magnitude as (or smaller than) the distance back to the virtual source. On astronomical scales, the virtual source of the laser beam and the physical location of the laser aperture are in essentially the same place. TenOfAllTrades(talk) 18:04, 4 November 2010 (UTC)

A beam with a wavelength of 600nm and an original diameter of 2mm has a divergence of 0.0003 radians (even larger if the beam is partial spatial coherent).[17] Still assuming a 2mm aperture, that means that the "virtual" source is only about 6m behind the "real" source, which is completely negligible compared to the 100km thickness of the atmosphere. Over the 100km thickness of the atmosphere, the beam will widen to a diameter of about 30m, compared to which the original 2mm diameter is negligible. Red Act (talk) 18:10, 4 November 2010 (UTC)

I follow your argument, but something is askew in your calculations or model or assumptions, because a beam width that increased by a factor of 15,000 (30m/2mm) over 100km would increase 6 x 10⁷ times over 400,000 km, and then a 2mm aperture would give a beam width of 120km at the Moon's surface, whereas the actual beam width at the Moon's surface in the Lunar Laser Ranging experiment was only 6.5 km - see below. That's different by a factor of 20. Gandalf61 (talk) 11:54, 5 November 2010 (UTC)

In light of this discussion, here is another question: If I were sat atop the retroreflector used for the lunar range finding experiment, would I be able to see the beam with the naked eye? HappymulletukHappymulletuk (talk) 22:44, 4 November 2010 (UTC)

Well Lunar Laser Ranging experiment says "the reflected light is too weak to be seen with the human eye", but nothing about your question. However it also says "at the Moon's surface, the beam is...about 6.5 kilometers wide", and as stated above "out of 10¹⁷ photons...only one will be received back on Earth every few seconds". Now allowing for a pupil diameter of 8mm and assuming the 6.5km wide spread of the laser is circular, my back of the envelope calculation says that some 6,059 photons would enter your pupil 'every few seconds' (which is horribly imprecise). However, that many photons would most likely be detectable (technically you could 'see' one photon), but I doubt that it would be intense enough that you would determine its source to be that laser. (Willing to be corrected here...). --jjron (talk) 07:24, 5 November 2010 (UTC)

algae and plankton

Would destruction of all the algae and plankton on the Earth destroy human civilization as we know it, and if so how? --96.252.213.127 (talk) 14:04, 4 November 2010 (UTC)

I can't find a reliable source quickly, but it's usually said that the ocean's algae is responsible for some large percentage of Earth's oxygen. Numbers between 50% and 80% are often mentioned in this context. Even assuming it's only 50%, that kind of oxygen loss would probably be devastating. Especially if it happened suddenly. APL (talk) 14:22, 4 November 2010 (UTC)

Not to mention that the whole food web would be shot to pieces. --Stephan Schulz (talk) 14:25, 4 November 2010 (UTC)

Based on the previous two answers: Yes. -- Sjschen (talk) 19:43, 4 November 2010 (UTC)

I'm not so sure. Most of Earth's population gets its food from land-based food sources (i.e. Maize), so the collapse of the marine ecosystem wouldn't really matter so much. The oxygen's a bigger deal. This document shows what happens to people in low-oxygen environments. If algae do really contribute this significantly to oxygen levels, things could get bad. Humans are pretty inventive though, so I bet enough people would create oxygen collecting and breathing devices (we already have them for Mountain Climbing) to prevent the total extinction of the human species. Buddy431 (talk) 00:58, 5 November 2010 (UTC)

Wouldn't there also be a massive upshot in atmospheric CO2? That could be bad on its own. (Though, I suppose it would help the maize in the short term.) APL (talk) 13:03, 5 November 2010 (UTC)

Superinfections?

How Many HIV Superinfections are there. I understand this is a second strain of the virus. and I also understand that the second stage of the virus may cause more rapid disease progression or carry resistance to medicines. How long is the life expectancy if someone is infected with a superinfection.

Questions are: How many Hiv Superinfections are there? How long is the life expectancy is someone is infected with a Superinfection? —Preceding unsigned comment added by 91.111.85.243 (talk) 16:16, 4 November 2010 (UTC)

According to HIV superinfection and the reference it cites, HIV superinfection is when an infected person becomes infected with a second strain of the virus, making the disease harder to treat. This seems to be different to what you understand of the term, at least from what you've written anyway. Because of this, there aren't a certain number of superinfections that could be counted. There are however, many Subtypes of HIV, but I think that it is impossible to say how many strains there are since it mutates so frequently. Life expectancy will vary depending on many factors, the HIV article has a section on prognosis and superinfection isn't going to make it any better. SmartSE (talk) 16:35, 4 November 2010 (UTC)

Acceleration at event horizon

In the wikipedia's article on gravity acceleration is written that on event horizon the gravity acceleration is infinite. But isn't infinite only at singularity? The event horizon is a few kilometres from singularity, so shouldn't be infinite. Francesco —Preceding unsigned comment added by 95.234.212.148 (talk) 16:52, 4 November 2010 (UTC)

Wikipedia does not have an article called gravity acceleration. There is an article on gravitational acceleration but this says nothing about any event horizon. Please could you state exactly which article you are talking about?--Shantavira|^{feed me} 18:06, 4 November 2010 (UTC)

Yeah, I thought maybe there was just a missing comma between "gravity" and "acceleration", meaning the article in question was Gravity. But that article also doesn't talk about acceleration near black holes. Neither do General relativity or Black hole, for that matter. At any rate, near black holes, the Newtonian gravity approximation completely breaks down, and you have to use general relativity. And in general relativity, gravity isn't even viewed as being an acceleration. Instead, objects travel in a straight line (a geodesic) along a curved spacetime. Red Act (talk) 19:23, 4 November 2010 (UTC)

Capillary DNA sequencers on eBay?

How much do sequencers cost? The department I've joined (as a PhD student) sends out samples to a company within another university for sequencing and it just makes me wonder why most large universities that carry out such research don't have their own internal sequencer for internal use. Wouldn't that work out cheaper than outsourcing, even with the cost of a technician to operate it? ----Seans Potato Business 18:03, 4 November 2010 (UTC)

Many financial decisions in research are very opaque to a graduate student. It is very possible, for example, that your research group or department has received funding grants with specific line item requirements - for example, $ X to be spent on outsourced technical work; $ X to be spent on capital equipment purchases. (If the funding comes from the government, this may be in support of a wide-reaching policy of using research to foster certain economic activity, or other totally opaque objectives from your point of view). Maybe the best resource to ask is your PI or Ph.D. advisor; depending on your research conditions, they may be willing (and even happy) to discuss research-funding details with the students. At my school, one detail was that money granted to individual professors was "taxed" (by the University!) at a different rate depending on its purpose: capital equipment investments were taxed differently than money granted for student labor, research expenses, and so forth - so the grant-writers, knowing this, played all kinds of mind-bending games to make sure they maximized the impact of their money. Nimur (talk) 18:13, 4 November 2010 (UTC)

(ec) I'm not sure what they cost, but remember that fully-operational sequencing services can't just spring out of nowhere. Someone has to write the grant application, find space, hire the staff, and supervise the facility. Unless there exist a few principal investigators who each do a lot of sequencing (and therefore see sequencing as big line items in their budgets) and who get along well enough with each other to write such a grant proposal, it's unlikely that it will happen at your university. It may also be that unless utilization of the sequencers remains high (50% of the maximum throughput? 80%?) and there are enough tasks to fully occupy a full-time technician (how many sequencers can one full-time tech operate?) then any theoretical per-sequence savings will be smothered in operating overhead costs, and then you've gone to a tremendous amount of time and effort to build a facility that's less cost-effective than the original outsourcing option.

As well, outsourcing 'future-proofs' your sequencing needs. If someone introduces a new technology then it's up to your contractors to figure out how to pay for it — you don't have to write a new grant. If the output from one service isn't up to your requirements, then you can change to another lab (or send piecework off to other labs in cases where specialized treatment or tools are required). TenOfAllTrades(talk) 18:35, 4 November 2010 (UTC)

Oh, right, I see. Well, I'll put £50 in the pot to buy Edinburgh Uni's own sequencer. :) I'll ask my supervisor what it's all about. ----Seans Potato Business 18:48, 4 November 2010 (UTC)

Keep in mind that the cost of the machine itself is a *very* small part of doing sequencing. There's disposables/reagents associated with each run. (You replace the acrylamide in the capillary after each run, and the capillary itself is only good for a limited number of runs.) Then there's the maintenance costs associated with the equipment (usually 5-10% of the list price of the equipment *per year*). Finally, there's the time cost for the the technician to run it, and personnel costs tend to be the most expensive part of any business. Given that there are a number of companies who have brought assembly-line efficiency with razor-thin profits to DNA sequencing, you'd have to be doing a lot of sequencing to make it cost effective: think enough work for several full time technicians. You say you are using "a company within another university" currently, which makes me guess that you're probably already getting the same near-at-cost price the other university gets. It's highly unlikely that your university would be able to do it cheaper by itself. Indeed - after evaluating the price, quality, and turn-around time, for us it's actually better for to go with a private, commercial provider for sequencing, rather than use either of the two on-campus sequencing services we have. -- 140.142.20.229 (talk) 21:59, 4 November 2010 (UTC)

Are we very tiny in the universe?

I don't mean this as a silly question, but I can't get over how tiny the earth is compared to the sun and how tiny the sun is compared to Arcturus. So, are we like the tiny people living in the locker of the movie Men in Black, where we don't even know how small we are compared to the universe around us? Are there other planets as big as Arcturus, and is it possible there are giant lifeforms and we are just a speck of dust compared to them? (If I sound insane, please let me know. Thanks.) AdbMonkey (talk) 18:31, 4 November 2010 (UTC)

I think I get what you're saying. You're asking whether we are to some ET lifeform as, say, small insects are to us? ----Seans Potato Business 18:42, 4 November 2010 (UTC)

I think the OP is referring to the film closing, which zooms out on our planet/solar-system/etc. to reveal that it's just the inner molecular structure of a giant alien. While it's tempting to look at solar-system models and compare them to bohr atom models, they are not the same. Different physical laws govern the behavior of our solar system (mostly, gravity), as opposed to the electromagnetic and nuclear effects that govern atomic behaviors. So, the very large structures in the universe are probably not just bigger versions of atoms. What we can see in the universe around us is large-scale structure of the cosmos - things like galaxies, and then at larger scales, clusters and filaments, and so on. We are not capable of "zooming out" to arbitrary limits - we are bound by our experimental capabilities. But we have some pretty good, albeit incomplete, ideas about the physics that governs the extremely large processes in our universe. It would be unlikely that any "macro-world" built out of the larger structures of our universe could exist and be compatible with what we do observe. Nimur (talk) 18:48, 4 November 2010 (UTC)

Well, thank you for answering, but I didn't think that the universe was a atom, or that our tiny planet was an atom, but I know what you're talking about from that ending scene. I was actually wondering if there could be gigantic life and if we would be super, super tiny compared to them. I was wondering if there were giant planets as big as Antares, because all I hear of are gas giant stars. So, to reframe my question, are planets capable of getting to be the size of Arcturus? Thanks for explaining that we're not likely a tiny component in a "macro-world." AdbMonkey (talk) 19:00, 4 November 2010 (UTC)

No, you couldn't get planets as big as a star, because once you get a collection of that much matter in that small a space, the pressures in the core are enough to get nuclear fusion going, which is what makes a star a star in the first place. (Hmm, actually, thinking about it I don't know whether you could theoretically in a very metal-rich environment have ridiculously big planets, but you'd have to artificially create the conditions or wait a very long time for enrichment of the ISM to get you to that point ...) --86.130.152.0 (talk) 19:37, 4 November 2010 (UTC)

So does that mean there is an upper limit of how big a matter based planet can become before undergoing "auto-fusion"? -- Sjschen (talk) 19:42, 4 November 2010 (UTC)

Would depend very much on the exact elemental composition, I would think. Some elements are much easier to fuse than others, and many need energy putting in for it to happen. But the (baryonic) matter in the universe is overwhelmingly hydrogen, so you do get stars. --86.130.152.0 (talk) 20:53, 4 November 2010 (UTC)

So if I were to construct a planet "brick-by-brick" with some kind of baryonic matter, say clay bricks, is there a way to calculate the critical mass (in the way they discovered the critical mass for U-based nuclear fusion) in which the pile would start crushing itself so much to start undergoing fusion? Or directly collapse into some kind of neutron star, black hole, or "weird"? -- Sjschen (talk) 05:38, 5 November 2010 (UTC)

The size of a biological creature is related to 3 things: Gravity, Heat, and Energy. A larger creature will retain heat better (good in the cold), but will also have a harder time getting rid of heat created by exercise. Gravity is obvious, but the strength of biological matter is unlikely to change much, so if gravity was lower you would have taller (since it's easier to support), but not heavier (what would be the point of over-muscling the creature, i.e. the strength of muscles are likely to be about the same). (So it's up to you if that counts as bigger.) And energy from various redox (oxygen burning) reactions is more of less the same, but a bigger creature will need more energy which could be hard. Of course what I write here could just be a failure of imagination, but I suspect that our size is likely to be typical (for internally supported creatures anyway - if you have water dwelling, or gas filled creatures things could be very different). Ariel. (talk) 20:01, 4 November 2010 (UTC)

So what's the maximum size a lifeform can get? Since there's an upper limit on planet size? And life can't exist in a star, right? And the gravity is why roaches on this planet aren't big, right? AdbMonkey (talk) 01:46, 5 November 2010 (UTC)

The answer is that we don't know. We're pretty sure that the maximum size for earth-like life is represented by animals like the blue whale and Apatosaurus, which are among the largest animals ever to have lived on earth. However, consider that Earth-based life does some pretty outrageous stuff, chemically speaking. We seem to have this sense that aliens on other planets will have a chemistry that resembles ours, a body plan that resembles earth-based animals, etc, etc. The truth is, it is much more likely that alien life will bear absolutely no resemblence to what is on earth. Considering the rather exotic and convoluted ways that life on Earth has come up with to solve Earth-type problems, there's no telling what sorts of exotic ways that life on other planets may arrive at. For example, the heat-dissipation problems and musculature issues that Ariel discusses still asumes a roughly Earth-like body plan and chemistry, if you untether your mind from those limitations, it becomes almost boundless the sorts of life that may exist. My favorite statement along these lines was made by Douglas Adams, who once postulated on a "hyper-intelligent shade of the color blue". While that is plainly farcical, it does demonstrate that life could really be just about anything. --Jayron32 04:38, 5 November 2010 (UTC)

Solaris describes this very nicely.--131.188.3.20 (talk) 11:52, 5 November 2010 (UTC)

I thought the biggest living thing was some fungus somewhere. Sequoiadendron giganteum trees could be bigger than blue whales. If you are floating rather than being affected by gravity, and are in a medium of the right temperature or are 'cold-blooded', then weight and heat might not matter to much. 92.15.10.141 (talk) 13:17, 5 November 2010 (UTC)

A better candidate for 'largest' organism on earth is Pando_(tree). Also probably oldest. All hail Pando! SemanticMantis (talk) 15:54, 5 November 2010 (UTC)

Another thing to think about, which Jaryon alludes to above. How are you defining life? Depending on your definition, the Great Read Spot might qualify (homeostasis, reproduction, growth etc). Along these lines, some sci-fi have speculated about things like 'living' nebulae. What Nimur and Ariel say above is generally correct though, if you're looking for carbon-based biology basically similar to life on earth, there are some pretty solid limits at large scales. SemanticMantis (talk) 14:41, 5 November 2010 (UTC)

Why car radiators are called so.?

I know because it radiates heat..... but i think the prime mode of removal of heat is convection not radiation in a car. —Preceding unsigned comment added by 59.95.101.211 (talk) 18:41, 4 November 2010 (UTC)

Many thermal loss processes are happening simultaneously to cool the engine. The radiator is radiating heat directly (as infrared emission); and it is also undergoing a (very complicated) conduction/convection process, wherein it conducts heat to nearby air, and then the air flows away, both laminarly and convectively (usually with the assistance of an air intake duct and/or a fan). This doesn't even begin to address the complex cooling mechanism of the fluid that is circulating inside the radiator - again, a mix of conduction, convection, and radiation, all rolled into one. If you needed to calculate very accurately, you could measure geometry and material properties to determine how many watts are attributable to each process.

Regarding the etymology: I'd rack it up to "loose use of terminology." Radiators existed (for various applications) long before thermodynamic theory developed and formalized specific definitions. Nimur (talk) 19:09, 4 November 2010 (UTC)

Entirely different forms of power

I've been watching the BBC series on the National Grid and it got me thinking. Is there any conceivable power delivery mechanism that's better than electricity? I don't mean like nuclear power or hydro or whatever where power is generated and turned into electricity (or wind), I mean the actual end thing. I.e. where we no longer have electrical powered devices we have 'x' powered devices. I don't want to get into whether it's economical or realistically going to replace electricity, purely thinking - is there research going on to look at different non-electricity based ways of powering devices. ny156uk (talk) 18:42, 4 November 2010 (UTC)

There is some interest in both extra-orbital and surface-to-surface microwave power transmission. -- Finlay McWalter ☻ Talk 18:46, 4 November 2010 (UTC)

(EC)Please provide some metrics of how "better" is defined. There are doubtless special cases where superior systems might be proposed. , or provide a test case, such as "Transmit 1 mw of power to a spaceship 1 million km from Earth for 1 month."Some sort of laser might get the power there better than a pair of copper wires. "Transmit 10000 watts of power from the gasoline engine of a car to the rear axle." A hydraulic and mechanical transmission might do a good job at a lower cost. or "Transmit 80,000 BTU of energy from a furnace to the living space of a house." A steam or hot water boiler might be cheaper and lower maintenance than a steam turbine and generator with electric radiators. "Transmit energy from a solar power satellite to the ground." Microwave might work, copper wires are doubtful. Getting 600 megawatts of power 100 miles from a power station to a city? A drive belt, or a rotating shaft would be expensive and have very high friction losses. A hydraulic or compressed air system would be subject to leaks and friction losses. A laser or microwave or hydraulic system would probably be more expensive than electric wires and transformers. Edison (talk) 18:53, 4 November 2010 (UTC)

Purely of historical interest, many factories were powered by a central power source (stream, or sometimes a waterwheel) and this power was transmitted to many users inside the factory mechanically, using belts and shafts (info). Even then the mechanical losses were severe, but I guess that (if electrical power just didn't work for some science-fictiony reason) we could all get power delivered to our homes by means of miles of rotating shafts. -- Finlay McWalter ☻ Talk 18:55, 4 November 2010 (UTC)

• I believe Finlay meant to say "steam, or sometimes a waterwheel". --Anon, 03:59 UTC, November 5, 2010.

(ec) Energy is never really "produced" - it's moved around, and it changes form. Pumped storage uses gravitational potential energy, in the form of mechanically conveying (pumping) water - moving energy from the (electric) pump into the water. Many large institutions use a steam plant, instead of delivering heating via electric distribution; and large pipes full of steam deliver hot gas for use in water-heaters, building heating, and other energy-needs - they move thermal energy around. Natural gas lighting delivers energy in the form of chemical (delivering gas by pipeline), instead of running copper wire to power an electric light bulbs. Compressed air systems exist, and are in wide use to deliver enormous quantities of energy to industrial equipment, dentist-drills, construction sites, and so on. All of these schemes convey energy from a point of production to a point of use. But ultimately, what do you want to use energy for? If you want to power electric devices (like transistors, computers, and mp3 players), you need electricity at some point (whether you convey the energy in the form of compressed air or an electromagnetic wave, transistors can't run on compressed air. You can think about on-site electric generation: but there are few options that make things easier than electric distribution. There might be a future in filling up your iPod with alcohol so that it can run a fuel cell and produce electricity internally. Barring truly revolutionary changes in the way we understand physics, I don't think there is much foreseeable future in replacing transistors with non-electronic equivalents. They are simply the best, smallest, most energy-efficient, easiest-to-manufacture, devices, and we have an entire technology infrastructure set up to use them for all kinds of neat applications. Nimur (talk) 18:59, 4 November 2010 (UTC)

London had a high-pressure water system for powering small sites from 1872 to 1977. The UK grid and local distribution network is over 92% efficient at getting electricity from power station to the customers. 62.56.53.12 (talk) 19:51, 4 November 2010 (UTC)

A hydraulic power station, note the water tank on top, for more info see the image description

An alternative is Hydraulic power network, systems of which were quite common in cities during the early electricity age - a good method of tranmitting torque, etc, but not for lighting.94.72.205.11 (talk) 19:57, 4 November 2010 (UTC)

In Ada, Vladimir Nabokov presents an alternative history in which electricity has been banned and telephones and certain other devices operate by means of hydraulics. He doesn't explain how airplanes and automobiles (which exist in the fictional world) function without electricity, though. Deor (talk) 00:37, 5 November 2010 (UTC)

You don't technically need electricity for airplanes or automobiles, do you? I don't know how you'd use hydraulics for them, though, but if good-old-fashioned internal combustion engines are still viable then I think you're OK. --Mr.98 (talk) 00:57, 5 November 2010 (UTC)

Compressed air could be used see this article. Strong laser light in fiber optic "wires" could be a possibility. I'm not sure if those are "better" though. Ariel. (talk) 20:06, 4 November 2010 (UTC)

Flavours and colours of quarks

I was wondering how many different quarks there are, which led me to three questions. First, can any flavour of quark be any colour (excluding anticolours)? This would allow six flavours times three colours times two for regular and anti for a total of 36 different types. However, I noticed in our article that quarks can change flavours and change colours. Can they also change from regular to anti, meaning that any quark can be any of the 36 types, or are regular and anti completely seperate? As an unrelated question, could I make a regular-matter proton using three anti-down quarks? It wolud have a charge of +1, but I assume that something would be wrong with it. Thank you. —Arctic Gnome (talk • contribs) 19:24, 4 November 2010 (UTC)

Quarks are in fact constantly changing colour -- every time gluons are exchanged (which mediate the strong force between the quarks, so ALL THE TIME), they're transmitting colour between the quarks. They can't change directly from "regular" to anti, though of course in pair production you get quarks and antiquarks created at the same time. And three anti-down quarks wouldn't be a proton, they'd be an anti-Delta-baryon (you may find list of baryons an entertaining article -- see also list of mesons). Note that you can't have three quarks all of the same flavour in a baryon of angular momentum 1/2 due to exclusion principle effects -- you have to be in the J=3/2 mode. HTH. --86.130.152.0 (talk) 19:35, 4 November 2010 (UTC)

supernova

How far away would a supernova be if it had an apparent magnitude on earth of -10? Googlemeister (talk) 19:52, 4 November 2010 (UTC)

That depends on the type of supernova. Type Ia supernovae are considered to be fairly uniform (with some caveats), with an absolute magnitude of -19.3. (That last article, incidentally, shows how to calculate distance given absolute and apparent magnitudes.) Type II supernovae are more varied, but all are dimmer than Type Ia. TenOfAllTrades(talk) 20:05, 4 November 2010 (UTC)

(edit conflict) That of course depends on the supernova. According to supernova, all type Ia supernovae have an absolute magnitude close to -19.3. Thus they would have to be about 724 parsecs away to have apparent magnitude -10. Type IIs are dimmer than that, though. Our articles don't seem to say much about typical magnitudes of type Ibs and Ics. Algebraist 20:06, 4 November 2010 (UTC)

nuclear war

Would a nuclear war kill all the algae and plankton on the Earth? --96.252.213.127 (talk) 20:51, 4 November 2010 (UTC)

No. To achieve that, you'd need many orders of magnitude more energy than the total kilotonnage of the world's nuclear stockpiles. --86.130.152.0 (talk) 20:58, 4 November 2010 (UTC)

Direct energy released matters very little for this question. What is more relevant are the radioactive and meteorological effects — nuclear fallout, nuclear winter. But it seems fantastically unlikely that even under the worse conditions it would kill off all algae and plankton — I'm not sure what level of blocked sunlight you'd have to get to do that, but it must be fantastically high, probably worse than anything humans could actively do in the short term. --Mr.98 (talk) 00:34, 5 November 2010 (UTC)

Forget about algae - a nuclear war would have a hard time even killing all the humans. Despite fears, we don't actually have enough nuclear weapons to kill everyone, and the earth is very very big. Ariel. (talk) 05:58, 5 November 2010 (UTC)

Furthermore, life persists in some of the most harsh places, even if we could exterminate all humans, or even all higher animals, extremophiles show that life would probably persist in some form or another. Though, as Ariel notes, despite alarmist views, even the sum total of nuclear weapons couldn't directly kill all humans. --Jayron32 06:27, 5 November 2010 (UTC)

We could make life pretty miserable for people, though. Radioactive climate change... it's not a good thing. I think we could probably say with confidence that it would kill human civilization "as we know it." It's not really an "alarmist view" to say that a full nuclear exchange (which fortunately today is a lot less probable than it was) would be devastating for the species on par with an asteroid impact. --Mr.98 (talk) 14:09, 5 November 2010 (UTC)

Radio waves

I read the article on crystal radio (radios powered entirely from radio waves, with no need for a power source) but it doesn't explain the process? How much electricity is there in radio waves? Could they power a light bulb for example? 82.44.55.25 (talk) 21:01, 4 November 2010 (UTC)

According to the article, the power received by crystal radio antennas is at most measured in microwatts (millionths of a watt). To get an understanding of how much power a microwatt is, that’s 100,000,000 times less power than a standard 100W incandescent light bulb uses, and about 30,000 times less power than is used for a rather dim LED. Red Act (talk) 22:20, 4 November 2010 (UTC)

And if you've ever used a crystal radio, you know that the volume is very low. Immediately following the discovery of radio waves, a lot of inventors put a lot of effort into inventing a quality amplifier for use in loudspeakers. Nimur (talk) 23:24, 4 November 2010 (UTC)

Electricity

We're currently studying electricity, and while I can use the equations (Ohm's law and all that) just fine, i'm having some trouble intuitively 'getting' how electricity really works. Although analogies like the Hydraulic analogy are useful, they can break down when looked at closely.

My question is: What is voltage? It's the amount of energy that each coulomb of energy has, yes, but how is that energy stored? it's not like each electron has a liitle pouch they can store energy in, and the energy can't be stored as kinetic energy of the electrons, because that is current! And how does the application of a voltage make a current flow?

Thanks for helping sort my confusion, --HarmoniousMembrane (talk) 21:35, 4 November 2010 (UTC)

You can get offtrack thinking of electricity as something belonging to electrons. Applying a voltage to a circuit and the current flowing through it is NOT well represented by a mental picture of little "electron men" running into one end of a tunnel with some amount of momentum and eventually emerging from the other, and a resistance is not well modelled by the little electron creatures climbing a hill. The hydraulic model is not bad if you visualize the pipe as always filled with fluid, whether there is a flow or not. Think of voltage as pressure: in general the more voltage applied to an ohmic circuit path, the more current will flow. A higher resistance is like a longer or skinnier fluid filed tube. The tube is always filled with fluid, so it starts flowing out the distant end as soon as the valve is opened or the pressure is applied. Picture the voltage source or battery or generator as a pump which receives back into its input fluid as fluid is pumped out the outlet, for current electricity. (Such a model breaks down if carried too far, but helps with many circuit problems). Do lots of problems and get so you find the right answer easily, and it will all become more intuitive. Edison (talk) 00:15, 5 November 2010 (UTC)

I guess that no one else has answered this, because they are flabbergasted that the educational system has collapsed to the point that no one understands anything any more; rather they just have to memorises stuff. What happened to education and the long-winded pons asinorum. Never mind, the Chines are ready to take over world trade and economic leadership. --Aspro (talk) 00:22, 5 November 2010 (UTC)

Voltage is pressure, not just in the hydraulic analogy but literally. Mobile electrons repel each other and, given the choice, will space themselves out evenly in a wire. If there's a local excess/deficit in one part of the wire, that part will have a negative/positive charge that will repel/attract electrons to restore the equilibrium. Liquid water behaves in the same way, though for more complicated reasons, which is why the hydraulic analogy works. Imagine a closed loop of pipe with a pump in one location and a water wheel in another. The water downstream from the pump and upstream from the waterwheel is under pressure and its density is slightly higher than the average, while the rest of the water is under tension (negative pressure) and its density is slightly lower. Replace the water with a sea of electrons and the pump and wheel with a battery and electric motor respectively, and the same thing happens. The part of the wire that's under pressure has a slight net negative charge and the other part a net positive charge, so there's a macroscopic EM field (outside the wire), and that's where the energy is stored. -- BenRG (talk) 02:56, 5 November 2010 (UTC)

(The following assumes you're a GCSE-ish level student, apologies if that is a faulty assumption.)

Take heart, OP. There are studies that show that people's ability on the electricity part of school Physics courses is completely uncorrelated with the rest of the subject, so if you're struggling with this one particular bit it doesn't mean you've suddenly got much worse! I know that personally speaking, all this stuff only really clicked for me when I got to university and did Maxwell's equations -- once I understood those (and Gauss's Law and so on) I was able to go back to the "simple" circuit stuff and it made a lot more sense to me, but I wouldn't advocate trying to learn lots of calculus just on the off chance your brain happens to work the same as mine.

I would suggest that you look at all the different analogies out there (hydraulic, the "electron men"/"buckets of charge" carrying certain amounts of energy ideas -- which latter does come with several important caveats!) whilst always bearing in mind that they are just analogies and none of them is going to give the complete picture -- different ones are helpful for understanding different situations (simplistic presentations of the hydraulic analogy, for example, have a hard time with series circuits because your pipes are suddenly changing length all the time when you add new components). One thing you may find helpful is to read up on drift velocity, which is often left of Physics at lower levels these days, but makes a strong connection between the overall flow of current and the behaviour of the individual electrons in the electric field across the wire, and might help you disentangle some of the things you're confused about. --86.130.152.0 (talk) 06:53, 5 November 2010 (UTC)

Entropy

Hi! I'm in a 1st year physics course and now we're looking at entropy. In my text it says "If the temperature changes in the process of the addition of heat to a system, the change in entropy can be calculated using advanced mathematics. This chapter deals primarily with changes in entropy in isothermal systems. For a discussion of how a change in entropy is calculated when the temperature changes, see the Supplemental Text on the next page" I looked on the next page(s) and.... no supplemental texts :( I think they got lost somehow when the book was edited. But how is entropy calculated when the temperature changes? I tried your Entropy article but as I'm only in first-year physics that was not very helpful :( —Preceding unsigned comment added by 24.92.78.167 (talk) 22:03, 4 November 2010 (UTC)

Taking the heat to be added slowly (and reversibly), so that the system remains all at one temperature throughout, $dS={\frac {dQ}{T}}$. So, you can integrate (let's say over time) $\Delta S=\int _{t_{0}}^{t_{1}}{\frac {{\dot {Q}}(t)}{T(t)}}dt$. The trick is that you have to know how the temperature changes; if you know the heat capacity C of the system, it becomes nicer to integrate over the added heat: $\Delta S=\int _{0}^{Q}{\frac {dq}{T(q)}}$, where $T(q)=\int _{0}^{q}{\frac {dq'}{C(T(q))}}$. That last equation is the tricky one: $T(q)$ is on both sides, so unless C is a constant you actually have to treat it as an autonomous differential equation ${\frac {dT}{dq}}={\frac {1}{C(T)}}$. Solve that with the "advanced mathematics", then you have $T(q)$, and you can do the S integral. If C is constant, then $T(q)=T_{0}+{\frac {q}{C}}$ and you can directly write $\Delta S=\int _{0}^{Q}{\frac {dq}{T_{0}+q/C}}=C\log \left(1+{\frac {Q}{CT_{0}}}\right)=C\log {\frac {T_{1}}{T_{0}}}$. If you then try to start from absolute zero ($T_{0}=0$) you get nonsense; as the third law of thermodynamics says, C can't be constant at absolute zero. --Tardis (talk) 00:32, 5 November 2010 (UTC)

It's a tricky question. As a chemist, I start by telling my students that, for an ideal gas, dS = C_V. That puts them into an adequate state of confusion, because they can't believe it's as simple as that. Of course it's not, not for a real system! But practical measurements of entropy on pure substances still rely on heat capacity measurements to very low temperatures, and on finding the various phase changes. Physchim62 (talk) 01:21, 5 November 2010 (UTC)

You must have left something out: one and only one side of your equation is a differential. For constant C I get ${\frac {dS}{dT}}={\frac {C}{T}}$, but that's not very much like $dS=C_{V}$. --Tardis (talk) 13:53, 5 November 2010 (UTC)

How to control this old oscilloscope

I have this old oscilloscope but it didn't come with a manual. I hope it might be a simple enough machine that someone with relevant experience might be able to tell me what I'd need to know to operate it. I'd like to be able to connect a circuit driven by rectified but fluctuating current from a dynamo and determine the voltages present. What's that "vert" socket, bottom left for? --90.209.7.130 (talk) 23:52, 4 November 2010 (UTC)

You lucky man..

The good news is that all Oscilloscopes operate the same. This might get you going.Oscilloscope--Aspro (talk) 00:01, 5 November 2010 (UTC)

That article doesn't say anything about the 'vert' socket... when plugged in and switched one, should the 'pull on' light come on or is that only under certain conditions? Why does the on/off switch have a 1 and a !0 instead of a 1 and a 0? --90.209.7.130 (talk) 00:25, 5 November 2010 (UTC)

The "Vert" connector is just where you connect the signal. The switch with 1 and 0 looks like a custom add-on. The light you speak of is just a power-on indicator. Good luck. (Did the scope come with probes?) PhGustaf (talk) 00:40, 5 November 2010 (UTC)

If you have $32 plus my substantial finder's fee that you may donate directly to the Wikipedia Foundation then you can have the handbook you lack. Cuddlyable3 (talk) 14:46, 5 November 2010 (UTC)

November 5

Lethal overdose of Caffeine - biological process involved?

Recently a young man in the UK accidentally killed himself by ingesting two spoonfuls of caffeine powder. I was wondering about the mechanism by which a caffeine overdose actually kills you, as the news report didn't mention really how he died. The caffeine article mentions extreme amounts of caffeine can cause ventricular fibrillation. Does this mean your heart just kinda starts beating all out of rhythm, screwing up your blood flow, and thereby leading to death via asphyxiation? The Masked Booby (talk) 00:37, 5 November 2010 (UTC)

As the article you linked to states, v-fib results in "cessation of effective blood circulation". Asphyxiation means the air supply is cut off. In this case, that is not true...the oxygenated blood is just mostly sitting there rather than flowing to cells. The cells are starved for oxygen and soon start dying (or at least some of the most important ones do), so it's a similar effect to having no air supply, but a different chain of events. DMacks (talk) 01:16, 5 November 2010 (UTC)

Here's the article about the death. When are the ACMD going to issue a report on caffeine then? "This should serve as a warning that caffeine is so freely available on the internet but so lethal if the wrong dosage is taken” reminds me of other things. SmartSE (talk) 01:28, 5 November 2010 (UTC)

Other caffeine overdoses can cause "rhabdomyolysis and acute renal failure" [18] but reading the abstracts on google scholar it has caused deaths in a wide variety of ways. SmartSE (talk) 01:35, 5 November 2010 (UTC)

Thanks everyone! The Masked Booby (talk) 04:53, 5 November 2010 (UTC)

mosquito

Hello,

pls i would like to cofirm if it is true that an average mosquito has 47 teeth?

Thanks —Preceding unsigned comment added by 62.173.41.242 (talk) 00:53, 5 November 2010 (UTC)

Mosquitos have mouthparts designed to pierce into skin, so they wouldn't have teeth in the normal sense. --Chemicalinterest (talk) 00:57, 5 November 2010 (UTC)

Mosquitoes are actually nectar feeders - see Mosquito#Feeding habits of adults. In female mosquitoes (only) they can also pierce the skin and suck blood - see Insect mouthparts#Piercing and Sucking Insects. They don't have teeth as such. This site gives some pretty nice 'close-ups' of their mouthparts. --jjron (talk) 07:14, 5 November 2010 (UTC)

Whatever became of the "super focused sound" guy and his invention?

I recall reading several years ago about an inventor, perhaps in California?, who invented a way to focus sound such that if two people were standing shoulder to shoulder only one would hear the music projected from a device in front of them. The effect was so profound as to be at first unbelievable. (You guys really didn't hear that too?!?) I also recall advertising companies being very interested it, as it was purported to allow them to play targeted audio ads without filling the ambient environment with background noise. One of the articles mentioned walking past posters in a subway with each poster talking "to you" as you passed, but people outside the "beam" hearing nothing. Does this jog anyone's memory? I'd love to know what the current status of that invention is... The Masked Booby (talk) 04:50, 5 November 2010 (UTC)

The guy you're talking about is Woody Norris; see Sound from ultrasound. Red Act (talk) 05:40, 5 November 2010 (UTC)

The guy you're thinking of perhaps also might be F. Joseph Pompei of Holosonics, who is the one who actually solved the distortion problems of earlier systems, and beat Woody Norris to the market by a couple of years. But Woody Norris appears to have gotten the most famous for it, so you're probably thinking of him.

This is consistent with my impression of inventions in general. Contrary to popular perception, if you look at any major invention, the invention process is typically a complicated mess in which there really isn't one person who is really the inventor of the thing, and the person who becomes famous for being "the" inventor of the thing is not at all necessarily the first person to have created that type of thing. See, e.g., Invention of the telephone, Invention of radio, Electrical telegraph or Incandescent light bulb#History of the light bulb. Red Act (talk) 06:41, 5 November 2010 (UTC)

I don't know about that specifically, but some museums have systems where a parabolic dish in the ceiling projects sound down so that only the person standing directly in front of a particular exhibit can hear it. The effect is a bit startling. APL (talk) 13:38, 5 November 2010 (UTC)

Sound Refreshment Station, of which six are located in the departure areas at Oslo Airport, Gardermoen, are sound "showers" that make refreshing sounds audible only to a person immediately under them. Cuddlyable3 (talk) 14:33, 5 November 2010 (UTC)

"The decision to axe the Ark will leave the Navy without the capability of launching fixed wing aircraft."

What about its sister ship, the HMS Illustrious? Did the BBC become so unreliable, or is there something I missed? By the way, why would the British Navy decommission all their fixed wing aircrafts? If Argentina invades the Falklands again, the plan is to use only helicopters against their air force? --131.188.3.20 (talk) 11:21, 5 November 2010 (UTC)

According to HMS Illustrious, "As part of Strategic Defence Review, Britain's Harrier fleet is to be retired. Therefore, Illustrious will no longer launch any fixed wing fighter aircraft.". The reference (BBC News) says that the Navy will be unable to launch planes from aircraft carriers until 2019. As I understand it, the plan is that a new fleet(?) of aircraft will be eventually be built to replace the Harriers, so as long as they don't start the second Falklands War for ten years, it should be okay. --Kateshortforbob _talk 11:47, 5 November 2010 (UTC)

(edit conflict)HMS Illustrious (R06)#2010 says (citing Janes) that the Harriers themselves will be retired. Military of the Falkland Islands#Royal Air Force notes that the Falklands are defended by four Typhoons; that doesn't sound like a lot, but it's proportionately much more than defend the UK. -- Finlay McWalter ☻ Talk 11:50, 5 November 2010 (UTC)

Or decommissioning doesn't mean outright scrapping? Like, in case of some extreme emergency other solutions could be found, like investing more resources to reactivate them or complete the new models sooner, or just lease some from other countries? --131.188.3.20 (talk) 11:57, 5 November 2010 (UTC)

I would guess they also have ground defences, no? Nil Einne (talk) 12:04, 5 November 2010 (UTC)

If they really wanted, they could probably buy the USS John F Kennedy which the US is finished with. Googlemeister (talk) 12:59, 5 November 2010 (UTC)

In the next few years, all they will need will be something to lauch drones (Unmanned aerial vehicles) from, and helicopters. 92.15.10.141 (talk) 13:34, 5 November 2010 (UTC)

Childhood

Why does childhood only last 18 years? jc iindyysgvxc (my contributions) 13:37, 5 November 2010 (UTC)

It doesn't. Maturity in humans doesn't end until the mid-20's. Then, after a period of stabilization, many humans go through a relapse into a second childhood. -- kainaw™ 14:16, 5 November 2010 (UTC)

Childhood is the age span ranging from birth to adolescence, typically between the ages 13 and 19. Biologically the development from child to adult is the process of Puberty whose onset is usually between 10-13, having dropped from an average 16.5 in England in 1840. A significantly Delayed puberty is regarded as an abnormality with an underlying cause that needs investigation and possibly correction by hormone treatment. Age 18 or a range of other ages are used in formal thresholds in laws that define Age of consent, Coming of age and in the age of reason rules for baptism in Western Christian churches. In many countries, there is an age of majority when childhood officially ends and a person legally becomes an adult. The age ranges anywhere from 13 to 21, with 18 just being the most common. Cuddlyable3 (talk) 14:25, 5 November 2010 (UTC)

This article discusses recent trends in extended child-like behaviour [19]. In short, the claim is the average twenty-something today doesn't really fit into classic 'child-adolescent-adult' classification schemes. SemanticMantis (talk) 14:53, 5 November 2010 (UTC)

Numerous US politicians have dismissed things they would prefer to forget as "youthful indiscretions." Several back as far as Bill Clinton said their use of drugs while in college was a "youthful indiscretion[20]." Unsuccessful Supreme Court nominee G. Harrold Carswell said his vow of "segregation forever" at age 27 was a "youthful indiscretion[21]." Bobby Kennedy serving as Counsel for Joseph McCarthy's redbaiting House committee at age 27 was dismissed later as a "youthful indiscretion[22]." George W. Bush said his drunk driving arrest at age 30 was a "youthful indiscretion". Grover Cleveland dismissed the fathering of a child out of wedlock when he was 37 as a youthful indiscretion [23], [24]. Vice President Dan Quayle, while a candidate said his vote against a Veteran's Administration cabinet position at age 41 was a "youthful indiscretion.[25]" Representative Henry Hyde said his five year affair with a married woman from age 41 to 45 was a "youthful indiscretion." Childhood among politicians thus may extend to 45. Edison (talk) 15:26, 5 November 2010 (UTC)

Chemistry

CH3-CH=CH-CH2-CH3+HBr -> ? —Preceding unsigned comment added by 121.245.138.117 (talk) 13:46, 5 November 2010 (UTC)

Hbr#Uses_of_HBr may be useful, we don't do you homework though. SmartSE (talk) 14:20, 5 November 2010 (UTC)

genetically modified foods

what are the most commmon genetic modifications to produce? 70.241.22.82 (talk) 13:56, 5 November 2010 (UTC)

According to this article: GMO corn (maize), GMO soy, rBGH milk, GMO canola (oil), and, interestingly, aspartame, which is produced these days using GMO bacteria. That sounds pretty plausible to me. --Mr.98 (talk) 14:04, 5 November 2010 (UTC)

If you were meaning what are the actual modifications that are made, the most common are resistance to glyphosate (a herbicide) and adding bt toxin (an insecticide). SmartSE (talk) 14:13, 5 November 2010 (UTC)

time constant for capacitor in both parallel and series

Suppose there is a resistor R1 after a battery, that then forks into a capacitor and a resistor R2 (that is they are both at the same potential difference). The circuit is then closed.

I am having a real hard time finding a succinct derivation of the time constant for this circuit. When t=0, most of the current (that is, E/R1) flows through the capacitor, but as time goes on, the current flows through R2 as the resistance of the capacitor becomes infinite.

How do I solve for the time constant? Neither google or the articles are helping me. John Riemann Soong (talk) 15:17, 5 November 2010 (UTC)

I don't get our explanation for charging a capacitor in parallel with a resistor. How does the time constant change in this case? John Riemann Soong (talk) 15:21, 5 November 2010 (UTC)

question

If an airoplane was crashing, why don't people wait til it's a few feet from the ground and then just jump the short distance? —Preceding unsigned comment added by 85.140.85.64 (talk) 15:30, 5 November 2010 (UTC)

No, because you'd still be traveling towards the ground at hundreds of miles per hour. (You cannot possibly jump hard enough to even come close to counteracting that.)

You're better off in your seat, buckled in. Let the plane absorb as much of the impact as it can. (Of course, if the plane is just plummeting straight down, that won't save you either.) APL (talk) 15:43, 5 November 2010 (UTC)

And even if you could jump with enough force to counteract most of the speed you are going down with, you are going to hurt yourself with you hit the ceiling. And then there is the horizontal portion of your vector, so you will hit the front of the plane at high speed. Jumping is not a great way to avoid getting hurt here. Googlemeister (talk) 15:51, 5 November 2010 (UTC)

An ejection seat is your answer. It might even save a troll who could not jump very high. Edison (talk) 15:58, 5 November 2010 (UTC)

I had assumed he meant jumping out of the plane. (Wait until the plane is a foot from the ground and then jump! A one foot fall never hurt anyone! Sorry. Doesn't work like that. ) APL (talk) 16:08, 5 November 2010 (UTC)

Springs question

In another discussion it was said that when a spring was compressed its mass increases by a tiny amount due to the stored energy. If this is true, why not have two springs, compress the first one, move the uncompressed one forward, compress that one, uncompress the other one and pull it to the compressed one and create a reaction-less drive? The force would be too tiny to be practical, but this is a thought experiment [Trevor Loughlin]80.1.88.13 (talk) 15:41, 5 November 2010 (UTC)

Because the energy that you're using to compress the springs ALSO has mass. (And the kinetic energy released when the spring decompresses!) APL (talk) 15:46, 5 November 2010 (UTC)

No energy enters or leaves the system, so it has a constant mass, and thus the ZMF is inertial. As expected.