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September 25

Yellow jacket wasp, death of nest in winter

I understand that yellow jacket nests usually die in the winter.
How long does it have to be cold and what temperature is cold enough before I am reasonably sure the nest has died? I live in the Sierra Nevada foothills of California and am avoiding a certain valued trail because I am allergic. (Don't worry; I carry an EpiPen.) —Preceding unsigned comment added by Ahatch (talk • contribs) 01:12, 25 September 2010 (UTC)

Your friendly neighborhood Park Ranger or Forest Ranger would probably know or be happy to help you find out for your region and the wasps in question, even if the particular nest your are concerned about isn't in their exact area of operation. WikiDao ☯ (talk) 02:49, 25 September 2010 (UTC)

It's hard to find definite information, but the impression I get from looking around a bit is that yellowjackets can stay alive in their nests in temperatures down to freezing or even below, but they become pretty lethargic when the temperature drops into the 50's. Looie496 (talk) 04:37, 25 September 2010 (UTC)

My personal experience with yellowjackets is that they buzz around aggressively a lot, but rarely actually sting. In fact I don't think I've ever been stung by one, though as a little boy I was stung by hornets with similar coloring.

Not that I'd count on that if I were allergic, certainly. Ahatch, I'm sure you know that an EpiPen is not a substitute for immediate medical attention, which might not be available on the trail. --Trovatore (talk) 02:09, 26 September 2010 (UTC)

I'd generally take 'I have an epipen' as code for 'I have a truly serious allergy, but I am responsible and well-informed, so please do not lecture me on safety or worry too much about my decision-making abilities.' I've seen it used this way several times by people living with lifelong allergies when they were ordering in a restaurant, or asking a company a question about their factory, or even just trying to move a conversation on. 109.155.33.219 (talk) 18:16, 28 September 2010 (UTC)

Angular nodes and nodal planes

what is the difference between angular nodes and nodal planes?? are they the same?? the number of angular nodes in an orbital is equal to the azimuthal quantum number. and the number of nodal planes is also equal to azimuthal quantum number.. so, are they both same?? harish (talk) 03:06, 25 September 2010 (UTC)

I think that "angular node" and "nodal plane" are different nodes, though both are related to the principle AND azimuthal quantum number. If you look at File:HAtomOrbitals.png, you can see radial nodes and planar nodes. The radial nodes are apparent in the 2s, 3s, and 3p orbitals, while the planar nodes are apparent in the 2p, 3p, and 3d orbitals. I think that the term angular node refers to the spherically-shaped radial nodes which are concentric to the nucleus, while the nodal plane runs through the nucleus. My quantum chemistry knowledge in this area is about 12 years rusty at this point, however. --Jayron32 04:28, 25 September 2010 (UTC)

For an atom, an angular node and a nodal plane are the same thing. You usually say "angular node" if you want to distinguish them from "radial nodes". "Nodal plane" is more common when you're talking about bonding, so you often find it in introductory descriptions of atomic orbitals as well: a σ-bond has no nodal planes, a π-bond has one nodal plane and a δ-bond has two nodal planes. Physchim62 (talk) 08:37, 25 September 2010 (UTC)

Fire in Zero Gravity

Well the title is pretty self-explanatory, how would fire look, better yet behave in zeo-gravity, say, a space ship. 66.229.227.191 (talk) 12:19, 25 September 2010 (UTC)

Here you go http://www.youtube.com/watch?v=fuFftT6ZR4k ny156uk (talk) 12:23, 25 September 2010 (UTC)

That's a fairly long-winded video answer from a person in space who can't light a match due to safety rules. Here's a shorter video-answer http://www.youtube.com/watch?v=SZTl7oi05dQ - the cool concept here is that the flame forms a sphere since there's no gravity to cause the less-dense hot air to rise, but this results in smothering of the flame, because without convection no oxygen is brought in (e.g. from "below") to provide necessary reagents for continued combustion. -- Scray (talk) 14:14, 25 September 2010 (UTC)

(awesome video, by the way!) With the caution that since there isn't any convective transfer of heat away from the once-burning match, it will take some time to cool below its autoignition temperature. If a new supply of oxygen is introduced – either the hot object is moved to fresh air, or our astronaut stirs up the air by moving around the space ship or turning on a ventilation fan – the match will burst back into flame and burn until it again exhausts its local supply of oxygen. TenOfAllTrades(talk) 16:18, 25 September 2010 (UTC)

I want to increase the melting point of Butter.

I am on a vision to create a certain type of ghee (butter oil) which has a melting point approximately greater than 50 degrees Celsius (323 K) But natural ghee (butter oil) start melting normally at 30-32 degree celsius (room temperature). Can any one suggest me any chemical which can help me sort out the problem. Please specify the chemical name, its common name, chemical formula and its proportion to add in the natural ghee (butter oil) per kg. —Preceding unsigned comment added by Cma290193 (talk • contribs) 12:48, 25 September 2010 (UTC)

I am not sure where you live, but I would be rather uncomfortable in a 30-32C room for an extended period of time. Googlemeister (talk) 13:22, 27 September 2010 (UTC)

Hydrogen, along with a catalytic amount of Adams' catalyst: the exact quantities will need to be determined by experiment. Physchim62 (talk) 15:06, 25 September 2010 (UTC)

Does this sound like a homework question? WikiDao ☯ (talk) 17:16, 25 September 2010 (UTC)

You might not even need the hydrogen. The platinum catalyst alone may promote isomerization of the double bonds in the unsaturated fats, giving you trans fats that can have a higher melting point. Bromine might do the trick, too. I don't know if anyone has ever made the ghee-derived equivalent of brominated vegetable oil before. Maybe you could even patent the idea and make a lot of money by selling it to ADM. —Preceding unsigned comment added by 96.227.210.71 (talk) 16:32, 25 September 2010 (UTC)

But if you intend this for human consumption, don't add bromine, or form trans fat or branched fatty acids, as these all have health negatives. Perhaps you can add a gelling agent, but it would make this ghee hard to digest. Graeme Bartlett (talk) 21:53, 25 September 2010 (UTC)

Yea, butter is already >60% saturated fat so I'm not sure saturating the rest would make that much difference to the melting point. You'd need to make the fatty acids longer through elongation reactions to seriously raise the melting point, which you can't do with simple chemicals. What exactly are you wanting to use it for? Palm oils are naturally longer chained than butter (which is why they've replaced hydrogenated fats) so maybe use these instead. Smartse (talk) 22:02, 25 September 2010 (UTC)

Butterfat is already mostly saturated. If you turned it into completely saturated fat, I suppose the melting point would go up, but I don't know if it would go up that much. It would be (mildly) interesting to know, from a chemical perspective, but as Graeme says, don't feed the stuff to me. --Trovatore (talk) 22:01, 25 September 2010 (UTC)

_{Why didn't I get an edit conflict?! Smartse (talk) 22:03, 25 September 2010 (UTC)}

_{That's happened to me a few times recently too; don't know why. Looie496 (talk) 22:47, 25 September 2010 (UTC)}

The software has automatically resolved edit conflicts for several years now. It doesn't always work well, but it's often okay. I don't know how much it has changed over the years, but people have been commenting on no EC for probably 2 years at least on the RD Nil Einne (talk) 16:37, 26 September 2010 (UTC)

I don't think there is actually any chance of getting an edible fat with melting point 50 C. Nothing in current use gets within a mile of that. Looie496 (talk) 22:47, 25 September 2010 (UTC)

Please don't feed me an oil with a melting point above body temperature! Ariel. (talk) 06:06, 27 September 2010 (UTC)

What about a gelling agent like agar? It sets at room temperature, but undergoes hysteresis and only melts at around 80C. I'm not sure if the agar will be soluble in melted butter though. Maybe you need to add egg whites. John Riemann Soong (talk) 06:49, 27 September 2010 (UTC)

Sauces with cornflour or wheat flour

When making a sauce, is there any advantage to using cornflour rather than wheat flour? Does cornflour cook more quickly, or have any other advantage? Thanks Edit: Cornflour is apparantly referred to as Corn starch in the former colonies. 92.28.241.137 (talk) 14:43, 25 September 2010 (UTC)

Yes, you use corn flour to thicken the sauce. The normal procedure is to wet the corn flour with a small amount of water or milk and then add it to the sauce near the end of the cooking: heating the mixture will cause it to gel, giving a thicker sauce. Wheat flour is usually used at the start of cooking a sauce, to adsorb fatty falvour components and stop them being lost. The two are not interchangeable: using corn flour instead of wheat flour will give you a lumpy suace (always a risk when you use corn flour), while using wheat flour instead of corn flour will give a sauce which is too liquid. Physchim62 (talk) 15:00, 25 September 2010 (UTC)

This sums it up better Thickening Agents - Flour and Making a Roux--Aspro (talk) 15:25, 25 September 2010 (UTC)

(EC)Cornflour is much higher in starch than wheat flour, and doesn't contain gluten. The starch is the thickening agent, the same as is used in blancmange and custard powder. For a starch-thickened sauce or pudding, cornflour is generally what you want: you would have to add more wheat flour for the same effect, and that would come with more other components, like gluten. 109.155.33.219 (talk) 15:28, 25 September 2010 (UTC)

• Please disregard what the non-chefs are saying. Either corn or wheat flour will give you a lumpy sauce when used incorrectly; they must be fully hydrated in order to gelate the starch. The main advantage of corn flour over wheat is that it thickens more quickly, and does not render a sauce opaque when doing so. Both corn and wheat flours must be cooked, however, to remove the raw starch flavour. Wheat flour is not used to 'absorb fatty flavour components and stop them being lost;' it is used as a thickening agent via creation of a roux. The two are in fact largely interchangeable, and the notion that wheat flour will produce a sauce that is too liquid is, well, bizarre. It depends entirely on how much you use. Corn flour has the added advantage of not going 'gluey' as it cools. Essentially, you can use either one you like, it just depends on what you want your end result to be. → ROUX ₪ 17:17, 25 September 2010 (UTC)

Here's an idea - citing a source - On Food and Cooking says that corn flour is practically pure starch, whereas wheat flour is ~75% starch, meaning that corn starch is a more efficient thickener. Because adding a thickener to a sauce dilutes the flavour, corn starch may be used if the chef wants to make a sauce as intense as possible. During the manufacturing of corn starch it is milled wet though which can give it flavours that wheat flour doesn't have. On the other hand, the gluten in wheat makes the sauce opaque and matte which a chef may not want it to be, so they may wish to use corn flour if they want a clearer sauce. Starch is an immensely complex molecule, containing different amounts of amylose and amylopectin, depending on the source. Sauces created with them have different properties - wheat sauces gel at 52-85°C whereas corn starch sauces do at 62-80°C. Wheat sauces are more stable after prolonged cooking than corn sauces but cannot be as thick. In short - there is no distinct advantage in using corn starch - it depends on what you're making and wheat is normally fine in my experience most of the time (original research). (You can also use arrowroot starch, potato starch and tapioca starch depending on the dish.) Smartse (talk) 22:32, 25 September 2010 (UTC)

A major part of the thickening effect of a wheat-based roux comes from the gluten. With all respect, if you think that wheat-flour-based sauces can't be as thick as cornstarch-based sauces, you probably haven't made one. It's quite easy to make them so thick that they're impossible to stir. Looie496 (talk) 00:45, 26 September 2010 (UTC)

Seriously. If you are using the exact same amounts by weight of cornstarch and wheat flour, the cornstarch will provide a thicker end result, but if you used equal amount by weight of e.g. methylcellulose, you would end up with something almost solid. (This also depends on whether you are using a roux, and if so, whether you are using it blonde or dark; the latter has more flavour but less thickening power). In addition, I--ps, I'm a professional chef--have found not a whole lot of difference in flavour loss between corn and wheat; starches absorb and sequester flavours, period. That being said, cornstarch mutes brighter flavours less than what does, which is why one sees cornstarch so frequently used in dessert fillings. In terms of other thickeners, one would actually get better (less loss of flavour) results with thickeners such as xanthan gum, methylcellulose, carrageenan, or even agar (all depending on your intended temperature of course). The statement that wheat sauces cannot be as thick as corn sauces is blatantly and completely false and wrong. → ROUX ₪ 02:53, 26 September 2010 (UTC)

It's somewhat odd to me that cornstarch (called cornflour right of the Pond) is being compared with wheat flour. Surely the apples-to-apples comparison would be wheat flour versus cornmeal, or wheat starch (does anyone make that?) versus cornstarch. --Trovatore (talk) 03:00, 26 September 2010 (UTC)

No, it's a perfectly apt comparison. Think of it along the lines of, say, 'would I want to use red wine vinegar or balsamic vinegar in this dish?' Both wheat and corn flour are ground portions of part of the kernel. Corn meal is, conversely, the entire dried and then ground kernel, and is not used for thickening; it is used in breading, to provide a crispy layer, in polenta, and in baked preparations such as cornbreads. → ROUX ₪ 03:27, 26 September 2010 (UTC)

I think cornstarch has had something else done to it, no? I don't think it's just the ground grain; I think the starch has been carried off with water or something, and then dried. I don't know that for sure but that's what I always thought.

Put it another way: You can make bread out of flour, and you can't make it from cornstarch, therefore cornstarch is not flour, whereas cornmeal is. --Trovatore (talk) 03:36, 26 September 2010 (UTC)

Ummm... no. Like I said: both wheat and corn flours are made from part of the kernel. Corn meal is the entire kernel. Like wheat flour, cornflour/cornstarch is largely made of starch. Unlike wheat flour, it contains no gluten. One can indeed bake with cornstarch, you just need to adjust your recipes to allow for the lack of protein. Cornstarch in baking provides a significantly crispier product, though is not suitable for all applications, and usually cannot be used solely by itself. → ROUX ₪ 03:39, 26 September 2010 (UTC)

Ah, here, from our article:

The corn is steeped for 30 to 48 hours, which ferments it slightly. The germ is separated from the endosperm and those two components are ground separately (still soaked). Next the starch is removed from each by washing. It is separated from the gluten and other substances, mostly in hydrocyclones and centrifuges, and dried.

Clearly this is not how you make flour. Of course our British friends are perfectly at liberty to call it cornflour if it gives them pleasure, but it isn't flour. Whereas cornmeal is. --Trovatore (talk) 03:41, 26 September 2010 (UTC)

Dude... look, I'm going to say this in a really nice way, but you have no idea what you are talking about. See flour, to begin with. In technical terms, cornmeal is a flour, yes. But in practical applications in the kitchen, cornstarch is much closer to 'flour' than the meal is. I'm not really sure why you're arguing a linguistic variation. The British call potato chips 'crisps' and French fries 'chips.' Should we tell them they're wrong about that, too? → ROUX ₪ 03:47, 26 September 2010 (UTC)

I have seen flour. It says flour is made by grinding up cereal grains. Cornstarch is not; it's made by washing the starch away from the flour and then drying it. --Trovatore (talk) 03:50, 26 September 2010 (UTC)

Oh boy. *facepalm*. You... well, you can just go ahead and complain about the use of language as much as you like. After my weekend I'll be getting back to a professional kitchen where I use corn flour all the time, and corn meal all the time, for entirely different applications. You're welcome to believe what you wish, after all, why would an expert in the field know anything? Sheesh. → ROUX ₪ 03:57, 26 September 2010 (UTC)

As an aside, in response to the question above by Trovatore, wheaten cornflour does exist at least here in NZ Nil Einne (talk) 04:03, 26 September 2010 (UTC)

That link redirects to gluten, which seems misleading at best. Maybe someone wants to do something about that? I wouldn't know where to start, myself, unless just to retarget it to starch.

@Roux: I'll try to bring down the emotional level a notch here. I can believe that wheat flour and cornstarch might serve similar roles in sauces, which judging from your username is a special interest of yours. But I think you have to admit they really don't, in baking. You say you can bake with cornstarch but admit that it's not usually satisfactory by itself. Whereas corn meal bakes up into a very lovely, if somewhat crumbly, bread. In that sense, surely, corn meal is closer to wheat flour than cornstarch is. --Trovatore (talk) 04:15, 26 September 2010 (UTC)

Except that it's not. The reason why what flour is so useful in baking is the presence of gluten, which creates a protein-starch matrix in which the other ingredients, and especially air, are suspended. Cornmeal has no such action. Corn starch, on the other hand, does (partially) create such a matrix when used in baking. → ROUX ₪ 04:25, 26 September 2010 (UTC)

Please stop with the exasperated tone, OK? It isn't polite, and I made an effort to get back to civil discourse; I think you can too.

Now, on the substance, can you really make bread just from cornstarch? I have never seen it. Where would one encounter it? Secondarily, apparently cornmeal does have gluten (the cornstarch article specifically mentions separating the starch from the gluten) so why exactly would corn meal not make this matrix of which you speak? --Trovatore (talk) 04:29, 26 September 2010 (UTC)

I am exasperated because you keep harping on the same thing over and over and not listening to what you are being told. I do not know the exact science behind why cornmeal does not have that action, though I suspect it is that there is relatively very little gluten in corn and thus it is too weak to hold together. McGee, This, or Adria would probably be able to give you a definitive scientific answer to the question. And yes you can make bread-like-things just from cornstarch, they just don't rise as much, and run the risk of burning very quickly. → ROUX ₪ 04:34, 26 September 2010 (UTC)

OK, well my exasperation comes from the attitude you have taken even after you were proved wrong about the origin of cornstarch. --Trovatore (talk) 04:38, 26 September 2010 (UTC)

Except you did no such thing, so not sure where your exasperation comes from. In any case, after your particularly ill-advised and rude questioning of my credentials, without an apology, it seems abundantly clear that I am being sucked down a rabbit hole of endless IDHT. I am withdrawing from this discussion; you are welcome to believe what you wish. → ROUX ₪ 04:48, 26 September 2010 (UTC)

Fair-minded readers can judge for themselves. I do apologize for the remark about the credentials, which I self-reverted quickly. However I did indeed prove Roux wrong about the cornstarch. --Trovatore (talk) 08:05, 26 September 2010 (UTC)

No, you did not. As I stated, cornstarch is made from part of the kernel--the starch. The fact that I didn't go into the precise details of manufacture is supremely irrelevant. I wasn't going to respond, but I will not let lies about me stand uncontested. → ROUX ₪ 08:39, 26 September 2010 (UTC)

The record is right above us, Roux. I said I thought the cornstarch had had something else done to it, that it had been carried off with water and then dried. You said "no". It's true, there were other things you could have been saying "no" about, but you certainly didn't clarify. I found the article passage that described how cornstarch is made, which was exactly as I had said.

That was the point at which you told me "nicely" that I didn't know what I was talking about.

As I say, fair-minded readers can judge for themselves. --Trovatore (talk) 08:45, 26 September 2010 (UTC)

If you say so. → ROUX ₪ 09:00, 26 September 2010 (UTC)

Although I'm sure it wasn't fun for you two. I, for one, found this entire argument interesting. Both of you: Please don't be dissuaded from continuing to contribute. And maybe someone can tell me why potato starch makes much "gluier" pudding than corn starch. Ariel. (talk) 06:04, 27 September 2010 (UTC)

For what it's worth, I also found the information provided by Roux to be interesting. --Trovatore (talk) 06:09, 27 September 2010 (UTC)

As the OP, on reflection what matters most to me is which one is easist to get rid of the floury taste? Wheat flour or cornflour/starch? Thanks 92.29.116.227 (talk) 10:58, 27 September 2010 (UTC)

Cornflour. As stated above, mix it with a little water or other liquid suitable for cooking and you can add it quite near the end of cooking. Stir in a spoonful at a time because if added all at once it can go lumpy. Wheat flour needs to be cooked through for longer. Itsmejudith (talk) 15:01, 28 September 2010 (UTC)

Can you make water from Hydrogen & Oxygen?

Is it possible to take Hydrogen & Oxygen and turn them into water directly? E.g I have a tank of Hydrogen (gas or liquid) and a tank of Oxygen (gas or liquid) - is there a way to cause a reaction between them that will turn them to water (rather than a massive explosion!) Exxolon (talk) 16:06, 25 September 2010 (UTC)

All it takes is a spark to convert a mixture of H2 and O2 into H2O. Heat is generated. Whether or not you get a massive explosion or not will be determined by how much of the mixture you put a spark to. —Preceding unsigned comment added by 96.227.210.71 (talk) 16:10, 25 September 2010 (UTC)

You could do it with a hydrogen fuel cell. --Aspro (talk) 16:11, 25 September 2010 (UTC)

The name hydrogen actually means "water making" in Greek, and was named such because it was noted in the 18th century that burning hydrogen gas (with oxygen) produces water. --Mr.98 (talk) 16:17, 25 September 2010 (UTC)

Strictly speaking, the 'massive explosion' is the reaction that turns hydrogen and oxygen into water. As Aspro notes, hydrogen fuel cells separate the reagents and catalyze the formation of water, with the added bonus of extracting some usable electricity from the reaction. For a lower-tech solution, burn a mixture of oxygen and hydrogen under controlled-flow conditions. Oxyhydrogen flames are used in certain types of welding and glassblowing; one should be able to condense the water vapor from above the flame. TenOfAllTrades(talk) 16:37, 25 September 2010 (UTC)

Thanks for the answers. Schoolboy error, forgetting that the reaction already creates water vapour with the side effect of heat/explosion. I was looking for how to control the reaction, so if you were in space for instance with abundant supplies of both gases and wanted to safely create water for say terraforming purposes. Exxolon (talk) 16:40, 25 September 2010 (UTC)

The fuel cells of the Apollo Command/Service Module were designed to collect the water produced; the crew used this 'waste' from their fuel cells to supplement their onboard water supply. TenOfAllTrades(talk) 17:29, 25 September 2010 (UTC)

Video of the reaction WikiDao ☯ (talk) 17:24, 25 September 2010 (UTC)

Relativity

Why is Newtonian gravity incompatible with special relativity? I know it has to do with a simultaneous action, but does something acting simultaneously on something else lead to paradoxes in special relativity? 74.15.136.172 (talk) 18:46, 25 September 2010 (UTC)

Yes -- in special relativity, whenever something travels faster than the speed of light in one inertial reference frame, there are other inertial reference frames in which it goes backwards in time. Looie496 (talk) 19:14, 25 September 2010 (UTC)

As I've recently had a few opportunities to point out, that in itself is not a problem. You don't get paradoxes from coordinate-system-based backwards causality. You get them only from real backwards causality; that is, from causal loops.

To get a causal loop out of this effect, you have to do the trick twice. See tachyonic antitelephone. --Trovatore (talk) 22:08, 25 September 2010 (UTC)

Newtonian gravity is also incompatible with other aspects of modern physics, notably the Standard model. Acording to modern physics, all forces require a Force carrier, and gravity has none. If there is no carrier to transmit the force of gravity, then it isn't a force. Rather, it is a pseudoforce, see Fictitious_force#Gravity_as_a_fictitious_force. In other words, gravity is caused not by a force, but by perturbations in space-time caused by mass. This is the core of general relativity. There are hypothetical theories which include the Graviton in them. Many people will tell you that the graviton has not been disproven; rather that it just has zero evidence for it, unlike the other force carriers, for which there is evidence. --Jayron32 00:52, 26 September 2010 (UTC)

You can actually derive what Jayron32 says from considering problems with instantaneous action. We now don't focus on potential problems posed to causality, rather on conservation of momentum. Suppose we have two massive objects interacting with each other via some potential. If in one frame momentum is conserved, then that means that the change in mometum of one object during some time interval dt is balanced by an opposite change of the other object during exactly the same time interval.

In another frame, these momentum transfers that exactly balance each other transform into different momentum transfers and they happen at different times. This means that you cannot have conservation of momentum in all frames in general. The only way conservation of energy and momentum can be saved is if you only allow local interactions. I.e. if an object is to lose energy or momentum, it has to transfer it to something that is in direct contact with it. Interactions between objects can then happen via force fields which can carry energy and momentum. Count Iblis (talk) 01:32, 26 September 2010 (UTC)

Neat, thanks. 74.15.136.172 (talk) 02:41, 26 September 2010 (UTC)

Bleach and detergent

Would mixing bleach (Sodium hypochlorite) with a detergent for use for cleaning be a bad idea? 92.24.182.184 (talk) 19:29, 25 September 2010 (UTC)

I don't think so. Lots of laundry detergents include some bleach. Of course you wouldn't want to be cleaning anything that bleach itself would damage that way. Looie496 (talk) 19:34, 25 September 2010 (UTC)

I wouldn't recommend it if the detergent contains ammonium though! —Preceding unsigned comment added by 24.92.78.167 (talk) 01:44, 26 September 2010 (UTC)

A piece of soap and sodium hypochlorite would be no problem, but if the detergent is not a pure detergentand additionally contains ammonia or even worse hydrogenperoxide there is a good chance to produce some very unpleasant reactions. nitrogen trichloride or chlorine gas are only two possibilities.--Stone (talk) 07:26, 26 September 2010 (UTC)

Dehydrated water

Could appropriate proportions of liquid oxygen and liquid hydrogen make a greater volume of water? In other words, if you added together the volume of these liquid gases, then converted them to water, allowed it to cool to room temperature and pressure, would the volume of the resulting water be more or less than total volume the liquid gases they came from? Thanks 92.24.182.184 (talk) 19:37, 25 September 2010 (UTC)

This was asked back on 10th March 2010, and the answer was no. It's not possible to compress hydrogen enough, let alone the oxygen to go with it. CS Miller (talk) 19:49, 25 September 2010 (UTC)

September 26

dihydroxy dimethylol ethylene urea

whats dihydroxy dimethylol ethylene urea —Preceding unsigned comment added by Kj650 (talk • contribs) 01:57, 26 September 2010 (UTC)

Its a fabric treating agent commonly abbreviated DMDHEU, and the formal IUPAC name is 1,2-Dimethylol-4,5-dihydroxyethyleneurea We don't currently have an article on that, but if you paste that name into Google you will find structures of it. It is used to create so-called "wrinkle-free" fabrics. See Permanent press which has some linked references you could follow for additional information. --Jayron32 02:11, 26 September 2010 (UTC)

how is it made —Preceding unsigned comment added by Kj650 (talk • contribs) 02:49, 26 September 2010 (UTC)

[1] this said it is made from urea, formaldehyde, and glyoxal. And for me this looks all right, although you have to be careful not to get a polymer as a end product.--Stone (talk) 07:18, 26 September 2010 (UTC)

Ford Escape Securilock keys

Just got 2005 Escape today. Found out after getting home that one key works on the locks and ignition, and the other key works on the locks but not the ignition. Am going back to the dealer tomorrow, but since it's closed right now and this question of what's the matter is driving me crazy, is it normal for one key to have lock-only privileges and is there any way for the owner to fix this himself? Thanks. 76.27.175.80 (talk) 02:12, 26 September 2010 (UTC)

Normal keys have three components: the physical cut of the key to fit the physical lock, the "remote" circuitry (lock and unlock buttons), and the transponder chip that is queried by the on-board computer before starting is permitted. Does your faulty key not fit the lock, or does it just fail to start the vehicle? If the latter, then the transponder has not been correctly programmed. You might be interested in this method of programming, but it will not work in your case because you have only one correctly-programmed key, so you need to take the key back to the dealer to be programmed by their specialist equipment. Dbfirs 03:37, 26 September 2010 (UTC)

Shelf life *after opening* Baileys Irish Cream?

The article for Baileys Irish Cream states that According to the manufacturer, Baileys has a shelf life of 30 months. It should be stored between 5 and 25 degrees Celsius, or 41 to 77 degrees Fahrenheit. Presumably this is for an unopened bottle. How long is Baileys safe to drink after being first opened? And should it be refrigerated? Doing so would keep it cooler than the manufacturer's recommended temperature... The Masked Booby (talk) 06:53, 26 September 2010 (UTC)

From their website:

Baileys Irish cream is the only cream liqueur that guarantees its taste for two years from the day it was made, opened or unopened, stored in the fridge or not when stored away from direct sunlight at a temperature range of 0-25 degrees centigrade. One of the keys to achieving this two year shelf-life is in our patented process of blending of fresh Irish cream with the spirits and the whiskey without the use of preservatives. The alcohol acts as a natural preservative for the product. Under normal conditions of storage Baileys Irish cream has a shelf-life of 30 months. If you are concerned about a bottle of Baileys Irish cream please check the best consumed before date on the bottle - all bottles now carry a best before date. This number is located on the bottom left hand side of the back label. Example : Code 11 20XY would mean that we guarantee the product would taste perfect until November20XY (XY is the year two years from the date of manufacture).

Like most products of this kind, I suspect the shelf life calculation has nothing to do with safety and is rather a statement that the taste might change over time. As discussed in shelf life, the terms "best before" and "best by" are generally suggestions based on the expectation that the items' quality and desirability will degrade over time, but are not an expression that the item is unsafe. By contrast, "expiration dates" and "use by" dates are specifically meant to indicate that an item may become unsafe after a period of time (or in the case of medicines, that it lacks the expected potency). Dragons flight (talk) 08:02, 26 September 2010 (UTC)

All I know is that my parents had an opened (but tightly capped) bottle of Irish Cream sitting on a shelf for God knows how long; and when I opened it, the contents had turned to an unpourable gelatinous mass. Deor (talk) 12:48, 26 September 2010 (UTC)

@Dragons flight, I've read your posting twice through looking for the bit of it which addresses the original question, and I haven't found it. --ColinFine (talk) 20:09, 26 September 2010 (UTC)

I think DF was trying to say that Baileys Irish cream is probably safe after 30 months (definitely after 2 years) if stored properly even in an opened bottle. This partly addresses one of the questions the OP asked. Df also quotes the website, which makes it clear the manufacturer guarantees the taste of Baileys Irish cream will remain for 2 years, even in an opened bottle, if stored properly. My interpretation of that Baileys is also saying that the 30 months is for an opened bottle stored under proper conditions as well although I'm less certain of this. This again partially addresses one of the OPs questions. Finally from DF's quotation it's clear that refrigeration is okay, which again partially addresses one of the OP's questions (or more accurately corrects one of their misconceptions). It isn't clear whether refrigeration is better, although it's clear the manufacturer suggests it's better then allowing it to get above 25 degrees C, which may or may not be relevent to the OP.

Actually from writing this I'm struggling to see how you can read the posting twice thorough and not see the quite useful info DF provided in response to the OP's questions and comments. It's true DF's answer wasn't perfect, and there are still parts of the OPs questions unanswered, but I don't think they said it was. And this is the RD, part of the process is that often each person may provide some info which may lead to the complete answer. Although often we don't even get a complete answer if there can really be said to be such a thing (particular since 'safe' is a fairly iffy word and will almost definitely depend on the precise conditions anyway so we can't really answer how long it will be safe for although info on precisely how it changes, e.g. at different temperatures obviously would be useful).

Nil Einne (talk) 21:50, 26 September 2010 (UTC)

Radioactive isotope of iron

When iron is irradiated with neutrons an isotope of iron is formed. This isotope is radioactive with a half-life of 45 days. A steel piston ring of mass 16 g was irradiated with neutrons until its activity due to the formation of this isotope was 10 µCi. Ten days after the irradiation the ring was installed in an engine and after 80 days' continuous use the crankcase oil was found to have a total activity of $1.85\times 10^{3}$ disintegrations per second. Determine the average mass of iron worn off the ring per day assuming that all the metal removed from the ring accumulated in the oil and that 1 Ci i equivalent to $3.7\times 10^{10}$ disintegrations per second.

I get 8.57 µCi for the activity after the ten days (i.e. immediately before it was installed in the engine). I have no idea how to do the rest. --MrMahn (talk) 07:04, 26 September 2010 (UTC)

Trying not to do too much Helping With Homework:

Basically, I think you're making this harder than it is; you don't need the activity after ten days, just after ninety (ten before installation + eighty while in there), which conveniently works out to exactly two half-lives. From there, you can work out what fraction of that activity is observed from the oil; that must also be the fraction of the original 16g that's worn off, and working out the per-day rate becomes trivial. --81.153.109.200 (talk) 07:29, 26 September 2010 (UTC)

Following your approach, I get 0.004 grams per day. Is this correct?--MrMahn (talk) 10:47, 26 September 2010 (UTC)

It's what I get (actually, the first time I tried I got 4 ng/day because I forgot about the micro in the μCi, which is the sort of thing I've been whining at my new A-level students for all month so *ahem*), and it's a nice round number so it seems like it should be right, but I wouldn't like to guarantee it.--81.153.109.200 (talk) 19:42, 27 September 2010 (UTC)

Could ancient Egyptians see or not see the three "aligned" volcano peaks of Mars?

• 
• 
• 

• The three aligned volcano peaks of Mars, where they visible to the ancient Egyptians who build three aligned major pyramids, or was that in complete coincidence?? 24.78.166.69 (talk) 11:40, 26 September 2010 (UTC)

That is even less probable the the Orion alignment. Orion Correlation Theory--Aspro (talk) 12:13, 26 September 2010 (UTC)

It's coincidence - unless the ancient Egyptians had discovered the telescope or were visited by Martian space travellers ! Martian volcanoes are certainly not visible to the naked eye, and even early telescopes only showed large, high contrast surface features such as the polar caps and Syrtis Major. Look at Huygens' 17th century drawing of Mars in our article on history of Mars observation to see what I mean. Gandalf61 (talk) 12:22, 26 September 2010 (UTC)

Prior to visits by 20th-century space probes, the site of Olympus Mons had been named by 19th-century terrestrial astronomers (using telescopes, of course) as "Nix Olympicus" (i.e. "Snows of [Mount] Olympus"), implying that they had spotted the white clouds that sometimes form adjacent to that mountain, but pre-probe no-one is known to have glimpsed the three (smaller) aligned volcanoes of the Tharsis Bulge, and I suspect that (terrestrial) atmospheric distortions would make that impossible with anything but the very latest and largest current telescopes. 87.81.230.195 (talk) 15:26, 26 September 2010 (UTC)

If they were replicating the Martian pattern, surely the largest pyramid would be off to the side from the line of three, corresponding to the relationship of Olympus Mons to the Tharsis volcanoes. Looie496 (talk) 16:44, 26 September 2010 (UTC)

Timber recovered from an archaeological excavation

A piece of timber has been recovered from an archaeological excavation and it is required to find its approximate age by measuring the radioactivity of the carbon-14 contained therein. For this purpose it may be assumed that the proportion of carbon-14 in the natural carbon of living wood is everywhere and at all times the same and that it begins to decay at death. If the number of disintegrations observed from 5 g of carbon prepared from the specimen is 21 per minute, how old is the specimen? (The proportion of carbon-14 to natural carbon in living wood is 1.25 in $10^{12}$ and the half-value period of carbon-14 is 5600 years. The mass number of natural carbon is 12.)

The mass of carbon-14 in the 5g of timber before it died was $5*{\frac {1.25}{10^{12}}}=6.25*10^{-12}g$
This equates to ${\frac {6.25*10^{-12}}{12}}=5.21*10^{-13}mol$
so $N_{0}=5.21*10^{-13}*6.02*10^{23}=3.14*10^{11}$
so $A_{0}=N_{0}\lambda =3.14*10^{11}*{\frac {\ln 2}{5600*60*24*365.2425}}=73.79$ disintegrations per second.
${\frac {A}{A_{0}}}=e^{-\lambda t}$
so ${\frac {21}{73.79}}=e^{-{\frac {\ln 2}{5600*60*24*365.2425}}t}$
solving this for t gives me a value which is clearly not correct.--MrMahn (talk) 11:59, 26 September 2010 (UTC)

First, whoever gave that question should be reprimanded for suggesting that "natural carbon" has a mass number of 12, or for using "natural carbon" to mean ¹²C. Secondly, you should use 14 (the molar mass of ¹⁴C) in the denominator of your second equation. And finally, if you get 73.79 (-~15% due to the error with 12/14 above), then 21/73 of the original material remain, or about 30%. In other words, a bit less than two half-times have elapsed, and the sample is ~10000 years old. --Stephan Schulz (talk) 12:16, 26 September 2010 (UTC)

Dendrochronology is far more accurate than carbon dating when intact timber is found.--92.251.191.21 (talk) —Preceding undated comment added 16:06, 26 September 2010 (UTC).

Yes, under ideal conditions. But dendrochronology is useless if only small pieces of wood are recovered (you need enough contiguous rings to match the known record), and less reliable in areas without good tree-ring records. TenOfAllTrades(talk) 17:02, 26 September 2010 (UTC)

Distance that aliens could detect earth with our level of technology

Given that Aliens exist with the same level of technology as ourselves, from what distance could they detect our solar system, (by Radial or Transit methods). And more specifically, it is likely that Jupiter, and then Saturn would be detected, at what distance could they detect Earth? —Preceding unsigned comment added by Csmiller (talk • contribs) 16:03, 26 September 2010 (UTC)

Not directly answering your question, but you may find this interesting. Interestingly it's Neptune that would be the easiest to detect, because of its influence on the dust in the Kuiper Belt. Also, our current level of technology doesn't allow for us to detect planets the size of those in our system, even Jupiter, at interstellar distances. Rojomoke (talk) 16:18, 26 September 2010 (UTC)

Aye, I saw that going past on my /. RSS newsticker. It prompted me to ask; I've been meaning to do so for a while. CS Miller (talk) 16:30, 26 September 2010 (UTC)

As our extrasolar planet article explains, current technology does in fact allow detection of planets much smaller than Jupiter. Capabilities have improved a lot over the past few years. Looie496 (talk) 19:47, 26 September 2010 (UTC)

Wouldn't any alien civilization have an easier time detecting all the radio frequency radiation that we're emitting than actually detecting the planets themselves? I thought that was the point of SETI (except in reverse; we're trying to detect aliens' radio signals). If they could pick up a couple episodes of Bill Nye the Science Guy they'd know far more about our solar system than they ever could by studying it at interstellar distances. Buddy431 (talk) 23:34, 26 September 2010 (UTC)

The Fermi paradox article has:

"Using our own experience as an example, we could set the date of radio-visibility for Earth as December 12, 1901, when Guglielmo Marconi sent radio signals from Cornwall, England, to Newfoundland, Canada. Visibility is now ending, or at least becoming orders of magnitude more difficult, as analog TV is being phased out. And so, if our experience is typical, a civilization remains radio-visible for approximately a hundred years. So a civilization may have been very visible from 1325 to 1483, but we were just not listening at that time. This is essentially the solution, "Everyone is listening, no one is sending."

WikiDao ☯ (talk) 23:45, 26 September 2010 (UTC)

Did anyone but the wanna be tyrannical business mogul Marconi claim to have heard that Morse code "S" consisting of three dots? How likely is it that he lied or was deceived by static in the earphone and his knowledge and expectation of what was to be sent? There was no proper protocol, which would have consisted of some trusted person handing the sender a previously unknown message to be sent. Edison (talk) 03:00, 27 September 2010 (UTC)

Guglielmo Marconi#Transatlantic transmissions has some discussion. It appears while there is some doubt about his earlier experiment, his later experiment is more well accepted. So the date is at most out by a few months Nil Einne (talk) 13:20, 27 September 2010 (UTC)

Re-asking Csmiller's question in terms of Buddy431's comment, how close would an alien civilization have to be to us in order to detect our radio emissions if their SETI equipment had the same sensitivity as ours? I recall reading that our strongest military radars might generate signals that would be just barely detectable at the nearest star systems. I'll try to find a reference, as I think that such information should be in the article. -- ToE^T 15:11, 27 September 2010 (UTC)

OK, here's a start. From David Brin's 2006 anti active SETI essay, SHOUTING AT THE COSMOS ...Or How SETI has Taken a Worrisome Turn Into Dangerous Territory:

... in a paper written by Dr. Shostak ..., even military radars and television signals appear to dissipate below interstellar noise levels within just a few light years.

-- ToE^T 15:54, 27 September 2010 (UTC)

http://www.space.com/searchforlife/seti_shostak_aliens_031023.html There are enough such radars that, at any given time, they cover a percent of the sky or so. The signal from the most powerful of these could be found at 50 light-years distance in a few minutes time with a receiving antenna 1,000 feet in diameter. Indeed, these military radars are the only signals routinely transmitted from Earth that are intense enough to be detectable at interstellar distances with setups equivalent to our own SETI experiments. Hcobb (talk) 16:07, 27 September 2010 (UTC)

is this star fruit? what is it?

Mystery tree

—Preceding unsigned comment added by Hemanetwork (talk • contribs) 16:04, 26 September 2010 (UTC)

Mostly definitely not starfruit, the fruit don't look at all like it (they don't even look like stars). Could be rambutan or lychee but the picture is fairly blurry Nil Einne (talk) 16:28, 26 September 2010 (UTC)

It's an arbutus, sometimes known as a strawberry tree. The fruits are edible once they reach the orange stage, by the way, although not very tasty. Looie496 (talk) 16:32, 26 September 2010 (UTC)

Looks like Arbutus to me. Can be wrong though, too blurry. Oops Looie's comment didn't show up until I've submitted mine. Sorry Looie.--Dr Dima (talk) 16:33, 26 September 2010 (UTC)

If you look up carambola, you will see the real star fruit. When the fruit is sliced across its width, the pieces look like star fish. Myles325a (talk) 02:10, 29 September 2010 (UTC)

motion of rocket.

A rocket is in outer space far from any planet when the engine is turned on.In the first second of firing the rocket eject 1/120 of its mass with relative speed of 2400 meters per second.(1).Calculate the rockets initial acceleration. (2). Suppose 3/4 of the initial mass,M of the rocket is fuel so that the final mass is M/4 and that the fuel is completely consumed at a constant rate in a total time of 90sec. (i)If the rocket starts from rest in our coordinate system,find its speed at the end of 90sec. (ii)what is the velocity of the last portion of ejected fuel relative to our reference system. —Preceding unsigned comment added by 41.218.236.95 (talk) 16:08, 26 September 2010 (UTC)

Please do your own homework.

Welcome to the Wikipedia Reference Desk. Your question appears to be a homework question. I apologize if this is a misinterpretation, but it is our aim here not to do people's homework for them, but to merely aid them in doing it themselves. Letting someone else do your homework does not help you learn nearly as much as doing it yourself. Please attempt to solve the problem or answer the question yourself first. If you need help with a specific part of your homework, feel free to tell us where you are stuck and ask for help. If you need help grasping the concept of a problem, by all means let us know. DMacks (talk) 16:33, 26 September 2010 (UTC)

While I assume that this is a homework question, I can't imagine anyone posting one here right away unless they tried to solve it many times already.--92.251.191.21 (talk) 17:19, 26 September 2010 (UTC)

What DMacks means is, 'Please show us what you've tried so far, or how far along you've gotten'. It's Sunday night, the homework's due in the morning, what has he tried and where is he stuck? We'll help — but we want to know if it's a problem with understanding the concepts, difficulty interpreting a formula, or just a calculation error. TenOfAllTrades(talk) 17:35, 26 September 2010 (UTC)

Speaking in the general sense, I suspect you'll be wrong. In fact, I can't recall if there was ever any evidence '"physics magazine" guy' attempted his homework questions so we may have a whole lot of examples right there. Nil Einne (talk) 19:35, 26 September 2010 (UTC)

Perhaps the OP would care to read our article Tsiolkovsky rocket equation. -- ToE^T 14:21, 27 September 2010 (UTC)

Gold is the most electronegative of all the transition metals -- why isn't it a valuable organic catalyst like Pt or Pd or Rh or Os is?

Is it that it's too electronegative that it can't form metastable catalytic compounds like Pt can? John Riemann Soong (talk) 16:31, 26 September 2010 (UTC)

This type of catalysis is called "surface catalysis" or "Heterogeneous catalysis". It could be that while the electronegativity of the gold is favorable, the properties of the surface of the gold differ from other metals used. Also, consider the electron configuration of the elements in question, which will effect how they form coordinate bonds. Platinum, Palladium, and Nickel (Raney nickel) are all very common catalyst for these types of reactions, and look at the fact that the ALL have the same valence electron configuration, which means they probably tend to form the same bonds at the same angles and all of that. Consider that gold is in a group with copper and silver, NEITHER of which is terribly useful for this sort of catalysis. I am sure that electronegativity is a less important property here than coordination chemistry, which is dependant on the electronic environment around the atom. --Jayron32 05:06, 27 September 2010 (UTC)

Apparently, there are a number of recent papers on the use of gold as a catalyst [2]. The consensus seems to be that gold was not used simply because there was no research on it; organic chemists had long considered gold too inert and expensive. Someguy1221 (talk) 05:13, 27 September 2010 (UTC)

Reactions on surfaces deals with catalysis of this type; following blue links will give you some background on specific classes of surface reactions. The cost issue for gold hasn't been a concern for like 50 years, see the work of Vladimir Haensel on ultra-fine depositions of platinum on alumina surfaces (less than one part per thousand platinum); specifically used to keep cost down. There's no reason gold could not have been used in this manner. --Jayron32 05:24, 27 September 2010 (UTC)

Yellow copper compound

I react cuprous chloride (I'll tell you how I made it later) with sodium carbonate to get a yellow precipitate, a colorless solution, and fizzing. What is that yellow solid?

The cuprous chloride is made by reacting acidified cupric chloride with ascorbic acid.

The yellow solid dissolves in ammonia to make a yellow solution. It reacts with ascorbic acid to make cuprous chloride again. It reacts with hydrochloric acid to make some fizzing (excess sodium carbonate?) and a green cupric solution. It is not oxidized by sodium hypochlorite or hydrogen peroxide.

Thanks. --Chemicalinterest (talk) 20:09, 26 September 2010 (UTC)

You should try something called recrystallization, although you have to be careful (not to lose your product). Sometimes white powders for example have some discolouration cuz they have impurities. (Unless you do it already?) Although I guess if it really colours the ammonia solution yellow, it must be naturally yellow. John Riemann Soong (talk) 22:18, 26 September 2010 (UTC)

Cuprous chloride is colorless and insoluble. The yellow powder is insoluble as well. Recrystallation would not seem to work well. Also, why does it turn back to CuCl when reacted with ascorbic acid? --Chemicalinterest (talk) 11:11, 27 September 2010 (UTC)

Well you can dissolve it in ammonia or HCl and neutralise it with the other. But you don't need to do that. Ascorbic acid can be a pro-oxidant as well as an antioxidant under certain circumstances. I guess your results exclude metallic copper. Hmm. What about copper(I) oxide? It can be yellow if your particles are small enough and ascorbic acid reactions tend to produce colloidal nanoparticles. John Riemann Soong (talk) 15:24, 27 September 2010 (UTC)

Copper(I) oxide in ammonia is colourless, but I wonder if your precipitate is in fact, two different products or just one. You could also set up an electrochemical cell with a diagnostic half-cell (say metallic copper) and measure the voltage -- it won't be standard state but you could see in which way a redox would flow. John Riemann Soong (talk) 15:25, 27 September 2010 (UTC)

is CuCl soluble in neutral salty water?

After all, it's the Cl- and not the H+ that makes it soluble right?

Also why couldn't aqua regia also be made with NaCl added? The Cl- helps complex the oxidised gold. John Riemann Soong (talk) 22:26, 26 September 2010 (UTC)

Both questions can be quickly answered by considering the solubility of sodium chloride in water, and comparing it to the solubility of hydrogen chloride in water. Physchim62 (talk) 00:53, 27 September 2010 (UTC)

Sodium chloride is much less reactive. Does it react with manganese dioxide to produce chlorine? --Chemicalinterest (talk) 11:09, 27 September 2010 (UTC)

Vehicle damage from hitting a pedestrian?

I've been trying to find some kind of data or estimate regarding the average dollar amount for damages to vehicles in pedestrian accidents, but can't find anything. Can anyone give me any info on this or point me where I might be able to find this type of information?

What I'm ultimately trying to figure out is if $200 is a lot of damage for a vehicle after hitting a six year old child, or how fast a vehicle might have been travelling to have caused $200 damage in such an "accident"? Also, can the dollar amount written on the police incident report be considered an accurate assessment of such damage, or do they tend to be way off (would I be better off trying to get 25 y/o court documents for this info, or can I be reasonably sure the on-scene report I have is fairly accurate)?

(Is this a science question?)

Thanks in advance for any ideas. bcatt (talk) 22:35, 26 September 2010 (UTC)

I don't know about 25 years ago, but nowadays you'll be lucky if $200 will pay for a windshield replacement. A smashed headlight might be similarly expensive. If the airbags deploy (I'm not sure how likely this is.) you could be looking at a good deal more than $200 to replace them. APL (talk) 00:23, 27 September 2010 (UTC)

Yeah i was going to say the same. My dad hit a dog a few years ago doing about 50km/h and it did $1200 damage to a petty crappy old car and it was just the headlight, bumper and a bit of panel damage. As for the rest, it would depend on a lot of factors and I think it would border on "legal advice". Vespine (talk) 00:31, 27 September 2010 (UTC)

Agree with Vespine in that there are just too many factors to consider in this question. I don't think an "average dollar amount for damages to vehicles in pedestrian accidents" is a meaningful average. The amount will range from zero to the assessed value of the vehicle (i.e., write off), and those of us who are drivers will know that the assessed value of vehicles in itself ranges over several orders of magnitude. I don't think the OP is looking for legal advice, as I don't think any court would take an "average damage" into consideration: I interpreted this as a request for input into some sort of economic debate. Physchim62 (talk) 00:49, 27 September 2010 (UTC)

Just re-painting the front bumper – not replacing, just painting – can cost a couple of hundred dollars and up. (This post in a BMW owners forum noted a cost of $800 for a BMW-certified collision center to respray a front bumper in 2009.) This discussion among Ford owners notes specifies three hundred to almost a thousand dollars to repaint the hood of a Ford Explorer, in 2002. In other words, just modest paint damage can cost a few hundred dollars to repair; prices go up if there is damage across more than one surface panel. Replacing any one of a damaged bumper, grille, or headlamp assembly can again run into the low hundreds these days (thousands, if it is a specialty imported vehicle). It's even possible that $200 is given as a sort of nominal 'minimal damage' amount — it's virtually impossible to get out of a body shop without spending at least that much, even for very minor dents and scrapes. Overall, the dollar cost of repairs is a very sloppy measure of how much 'damage' was done in an accident, and it has an even less direct relationship with vehicle speed or the other parameters of the accident itself. TenOfAllTrades(talk) 02:28, 27 September 2010 (UTC)

I don't know if it is the same in the USA, but a few years ago my wife scraped a car door and we were quoted £800 for it to be repainted. The car was fairly old so we decided jsut to paint it ourselves. The guy then said "I didn't realise that it's non insurance, I'll do it for £200". There is a huge markup on insurance work in the UK. -- Q Chris (talk) 12:06, 27 September 2010 (UTC)

Yep. Similar story in Australia. Want a cheap job? Tell the panel beater it a non-insurance job and that you will be paying cash. HiLo48 (talk) 12:40, 27 September 2010 (UTC)

Thanks to everyone who responded. It's true I'm not looking for legal advice, though it's not part of an economic debate either. I have this on-site incident report from when I was hit by a car in a crosswalk about 25 years ago; it states the vehicle damage as $200, and it just got me curious what exactly that means. I also have no memory of actually being hit - just stepping into the crosswalk then lying on the ground in shock - so I was also curious if I might be able to use that amount to guess at what speed the driver may have been going...part of sort of a self-therapy type thing, I guess (probably better to get the court records if I want to delve into it anyway). I think TenOfAllTrades is probably right about $200 being a "minimal damage" amount. Anyway, thanks again to all. 24.69.99.45 (talk) 19:59, 27 September 2010 (UTC)

According to [3] prices have doubled between August 1985 and August 2010. (Assuming that you are using US dollars) CS Miller (talk) 10:37, 28 September 2010 (UTC)

September 27

Psychologically why is destroying things so much fun?

A group from out work did volunteer ground clearance in a park. Everyone wanted to chop down trees, even though it was much harder work than litter picking or leaf raking. I have read that demolition work has one of the highest levels of job satisfaction and I can believe it - it looks fun! A lot of people also engage in mindless vandalism. Why is destroying things so much fun? Is there any evolutionary advantage to this? It seems to me that most people would build a building out of necessity but knock one down for fun!. -- Q Chris (talk) 12:10, 27 September 2010 (UTC)

I would add a qualifier to the question. While Q Chris's experience may have involved equal numbers of males and females (can you tell us?), my view as a high school teacher is that his observations would far more accurately describe boys than girls. But overall it's a great question. HiLo48 (talk) 12:18, 27 September 2010 (UTC)

There were about equal numbers, and it appeared that (subjectively) the men and women both enjoyed the chopping down trees, but most of the women would do it for a bit until they were tired and then do some of the less physically demanding tasks. I (and most of the other men) continued chopping down trees until we were covered in sweat and had blisters on our hands - it really was that fun! -- Q Chris (talk) 12:38, 27 September 2010 (UTC)

It acts as a testing of self against nature in order to affirm one's own potency. Insecure youths appear to need to practice pointless destruction more, one such example could be the current UK Prime Minister when he belonged to the Bullingdon Club. --Aspro (talk) 12:39, 27 September 2010 (UTC)

There certainly was an element of competition, especially among the younger men. A couple of young marketing managers went after all the "bigger" trees, and raced to cut them down and drag them to the pile. The older blokes still got a lot of enjoyment out of it even though we were not competing for speed or size of tree. I think that there is some other element, as cooperatively demolishing buildings also seems fun. -- Q Chris (talk) 12:47, 27 September 2010 (UTC)

This is to be expected don't you think. We are a social animal, that cooperate with each other and competitively in a troupe. It appears to be hard-wired into us. Monkey's hunting in a group need to cooperate in order to outsmart their quarry but the chip which actually makes the kill has first pickings (the brain is rich in omega 3 and so is highly prized). It must have been like that for our distant ancestors also. Tearing things down, may have also been necessary to make space, to create more of the environment we needed to exist in. Just saying we evolved on the open savannah may be an over simplification. Our ancestors probably need a mixed and varied bushland which needed to be kept in check. The Australian aborigines are now thought to have slashed and burnt the land into a more hospitable habituate. Talking of which. 'Fire' is another phenomena of nature that fascinates small, and not so small boys. We are today, a product of yesterdays survival techniques. It appears to my mind quite likely, that the more satisfying the activity, the more essential to it was to our ancestors long-term survival as a specie. --Aspro (talk) 13:22, 27 September 2010 (UTC)

I think the Aborigines screwed up. Have you seen 90% of Australia? Googlemeister (talk) 15:37, 27 September 2010 (UTC)

Climate of Australia cites a paper I haven't read that may support that notion to some extent, but surely saying "the Aborigines screwed up the climate of Australia" is hyperbole to the point of easily being taken by some as a bit offensive, don't you think? WikiDao ☯ (talk) 15:51, 27 September 2010 (UTC)

Only if the people of which you speak insist on being offended. Seriously the vast majority of Australia more then 100 miles from the coast is below par in terms of it's ability to support human life. Googlemeister (talk) 15:59, 27 September 2010 (UTC)

Yes. The Aborigines didn't cause that. I'm sure you were joking, and there is actually something to it apparently, but any comments about race or culture are "sensitive" and may easily cause offense in a context such as this is all I'm saying. WikiDao ☯ (talk) 16:05, 27 September 2010 (UTC)

According to the analysis presented in, for example, Tim Flannery's The Future Eaters, the Aborigines did cause that, insomuch as by killing off most of the continent's megafauna during the period ca. 60,000-30,000(?) years BP, they disrupted the ecology so seriously that soils continent-wide were permanently impoverished (the linked article does not well represent the book's arguments, and minimises corroboratory studies that I have encountered elsewhere). Of course, there was no way that those very distant ancestors of present-day Aborigines could possibly know that that was what they were doing, so no blame could sanely be attached to modern individuals for these prehistoric events. 87.81.230.195 (talk) 21:41, 27 September 2010 (UTC)

I just want to point out that I don't think hunting has much to do with it. Lots of species have males who compete aggressively as forms of sexual selection, whether they hunt or not. See Alpha (ethology). However it is worth pointing out that specific expressions of alpha drive are almost certainly highly conditioned by cultural expectations, and not all males of any species strive to be alpha, especially when it does not confer exclusive reproductive success (as it does not with humans). --Mr.98 (talk) 16:28, 27 September 2010 (UTC)

I mention potency (to be taken in its widest sense) in my first post. Hunting was just giving a further example which does not include chopping down trees. Also, I'm restricting comments to primates in general not unrelated critters. The OP's question is about phenomena that clearly appears to cut across cultures, so with respect, I think this is just tangential.--Aspro (talk) 17:01, 27 September 2010 (UTC)

Destroying things, as such, is not necessarily fun; if your job is to destroy big buildings it may well be satisfying, but if your job is operating a trash compactor, satisfaction is hard to attain, even though you destroy a far greater number of things per week. I see no need to embark on a great fantasy of evolutionary psychology to explain this. Surely it's fun to affect things, for the sense of empowerment, regardless of whether you are destroying, creating, or just altering them. Chopping down a tree is a rare opportunity to have a big effect on a big object. Destroying a building feels significant, viscerally. (The greatest changes I routinely make to the world are microscopic and affect only bytes on hard drives.) One advantage of destruction over creation is that you don't have to think too hard or be too careful to get it right; there is nothing delicate in the process that you mustn't break, because breaking things is the whole objective. This is less true in the case of demolishing buildings, which must often be done with high precision; I imagine being told off for making an error that caused a demolition to be unsafe would reduce the job satisfaction. 81.131.61.27 (talk) 16:40, 27 September 2010 (UTC)

The question is "are there any evolutionary advantages to destructive behavior" right? And then a very specific example is given, in which it appears that men (mostly) are doing physically demanding labor in the proximity of women. As worded, the answer seems to me to be "yes, and there's a lot more going on in that example, and why all that is gets complicated." Evolutionary psychology gives an overview. WikiDao ☯ (talk) 17:33, 27 September 2010 (UTC)

I do not agree that destroying things is fun. To me trees are precious, I would hate to destroy any. Building something would be better. However chopping trees down has far more drama and variety than leaf-picking, and may be preferred for those reasons. 92.15.25.79 (talk) 18:43, 27 September 2010 (UTC)

In modern life, destroying things is usually prohibited. The fun comes from transgressing that rule. By the way, I dispute the claim that it's hard to obtain satisfaction as a trash compactor. I had a weekend job at a supermarket when I was a kid, and that was my favourite task. I never got tired of it. If you ever get the chance, I recommend crushing a pallet of expired yoghurt cartons. --Heron (talk) 19:21, 28 September 2010 (UTC)

Light from just after the Big Bang. Why is it reaching us now, since the matter from which earth was created also began with the Big Bang? Light travels much faster than matter.

Surely if light and matter were created simultaneously at the time of the Big Bang, such light would have passed us by immediately and be billions of light years ahead of us rather than behind? Or are we looking at that light "from behind" as it accelerates away from us into the future?

Many thanks indeed for any explanation.

—Preceding unsigned comment added by 222.123.128.194 (talk) 15:32, 27 September 2010 (UTC)

To prevent spamming, I removed your email address --KägeTorä - (影虎) (TALK) 15:34, 27 September 2010 (UTC)

I assume you are referring to cosmic background radiation? It's not quite "light from the Big Bang" so much as "weakened radiation from the Big Bang which has been bouncing around for quite a long time," if that makes sense. I'm not sure "from behind" or "ahead of us" are the right metaphors for thinking about an event which created space and time itself. It is not that the Big Bang exploded into a space (and then created us); it's more than the Big Bang was the creation of space. I think it makes more sense to think of it less as an explosion than as a big, hot, ball that expands and then cools down, and we're currently still inside the ball. --Mr.98 (talk) 15:57, 27 September 2010 (UTC)

As Mr.98 says, what we can detect in the cosmic microwave background radiation isn't light - it is microwave radiation that used to have a shorter wavelength but has been stretched as the universe has expanded. This radiation was emitted at an early stage in the development of the universe, at approximately 380,000 years after the Big Bang - we don't see any radiation from earlier than this because the universe was not transparent to radiation before this time. So this radiation has been travelling towards us for over 13 billion years. The reason it has taken so long to reach us is that it was emitted from a very long way away (exactly how far away gets complicated because space has expanded by over 1,000-fold while the radiation was travelling). Radiation that was emitted from nearby has already gone past us and we have missed it. Gandalf61 (talk) 16:16, 27 September 2010 (UTC)

I'd like to take a different stab at this. First, the OP is exactly right in pointing out the paradox -- the space that became "us" and the space that became "the CMB" were once right on top of each other, and on the surface it makes no sense that light-speed EM radiation (arguing the nuance of "light" based on wavelength is rather silly; it's fundamentally the same stuff) that was emitted relatively close by is only now reaching us billions of years later. "Radiation that has been bouncing around" isn't quite right; what is there for the radiation to reflect off? No, the answer is briefly mentioned in the posts above without really being linked: while matter doesn't move faster than light, space itself can expand faster than light. The early universe (prior to the formation of the CMB) underwent the inflationary epoch, and to this day the universe is subject to the metric expansion of space. This bit of physics (collectively known as inflation) explains how newly-visible parts of the universe (that is, the CMB) which should have no causal connection to us instead fit the cosmological principle. Everything was once very close together and causally connected but then expanded faster than light itself could propagate. — Lomn 17:45, 27 September 2010 (UTC)

I'm not sure the paradox is as strong as you're making out -- surely the key point here is that looking out into space is looking backwards in time and therefore the light we are seeing from 13.7ish bn years ago is also from 13.7 bn light years away (modulo the complexities of all that stuff about integrating a(t) along the line of sight that I've mercifully forgotten the details of). Inflation is required to explain why the temperature is so uniform in widely separated parts of the sky which should never have been causally connected with each other, but not the simple fact that we do see something there.--81.153.109.200 (talk) 19:46, 27 September 2010 (UTC)

I have to disagree with this. If you assumed flat space-time and all that, it would definitely be impossible to see any light from the big bang unless it was reflected off something. EM radiation doesn't just hang around. It travels in a line at the speed of light. Without accounting for metric expansion, any light from near the big bang would be at the edge of the universe and traveling outward, where we would never be able to observe it. To put it another way, in flat space-time, a photon and anything massive can't cross paths more than once unless the photon gets reflected. Rckrone (talk) 23:11, 27 September 2010 (UTC)

No, sorry, this doesn't make sense to me. Surely the directions the photons are heading in are isotropically distributed in all directions at the point of last scattering, so that some of them are heading in the right direction. It's not like they "know" they're at the "edge of the universe", the universe was filled with them at that point (and still is, just redshifted down to microwaves). Some of them were bound to be heading in the direction that we'd be able to pick them up. The whole universe is expanding, so I'm not sure what you mean by "outward". --81.153.109.200 (talk) 17:21, 28 September 2010 (UTC)

The Big Bang.

Maybe a more intuitive way to explain this (for myself as well as the OP) is with reference to a more visual approach. The graphic at right, for the point of simplification, shows the universe as a 2-D sheet. Big Bang at bottom, later (more current stage) at top. What's important is that in the very early period, space is very close together and light saturates it pretty homogeneously. As space itself accelerates faster than light in an initial inflationary period, the light itself is still imbedded in that space. So let's imagine a single photon, going from the bottom-left to the top-right. In the blobby phase, it is just starting out on the far bottom-left. In frame 2, it has just hit the edge of that red galaxy. In frame 3, it is just beyond the red galaxy. In frame 4, it hits the blue galaxy. So it would take it just about the time of traversing the universe to hit that blue galaxy, assuming that the amount of space has increased faster than the speed of light. Now I think the point of confusion here is seeing the initial Big Bang as an "outward" movement of photons (e.g. center to the edge) rather than a huge amount of energy/mass in a really exceptionally tiny amount of (very saturated) space. So you would have things like a photon on the lower-left edge facing to the upper right edge, not just an idealized "center" going outward. This is my admittedly qualitative and potentially wrong understanding, and what I was trying to convey in my first response (which is not as good as some of the others), and perhaps others can correct me on this or clarify it. --Mr.98 (talk) 21:53, 27 September 2010 (UTC)

Here's a diagram I just made that may or may not be helpful. Unlike the other time I made diagrams for a thread like this, this picture isn't numerically accurate, nor is it to scale. It's hard to draw the CMBR to scale for the same reason it's hard to draw the solar system to scale. What this shows is an Ω = 0 universe (the real universe has Ω ≈ 1) in which the early glowing plasma phase lasts for a much longer time (relative to the current age) than in the real universe. The nice thing about Ω = 0 is that spacetime is the flat spacetime of special relativity, and what I've plotted to the right is just an ordinary SR spacetime diagram in which light always travels along 45° lines, the SR redshift formula is valid, and so on. The CMBR that we see is the boundary of the plasma region; we can't see into the interior because the plasma is opaque. It's similar to looking at the Sun. The boundary is horizontal (spacelike) instead of vertical (timelike), but that doesn't make much difference. The surface temperatures are even similar: ~6000K for the Sun, ~3000K for the CMBR (but the CMBR is hugely redshifted). The temperature of the interior is much higher.

You can think of the shape of the last scattering surface as due to time dilation—particles near the edges of the diagram are moving faster, so they take longer to do anything, including cooling down. Likewise, you can think of the increasing density of the Hubble flow lines near the edge as due to length contraction. A nicer way to think of both of them, though, is in terms of Lorentz transformations; this whole universe is invariant under Lorentz transformations that leave the vertex at the bottom fixed, and everything else follows from that. You can use a Lorentz transformation to center the here-and-now horizontally, so it looks like we're at the center of the universe, but of course we're not; every location is the same as every other.

This universe doesn't have a horizon problem. Everything is in the causal future of a single point (the vertex at the bottom), even though the surface of last scattering is infinite in size! This diagram shows that you don't need anything to move faster than light to solve the horizon problem. It also shows the difficulty of talking about "faster-than-light expansion" in general relativity. I could plot this diagram in different coordinates where the expansion "looks" superluminal, but it's the same physics either way.

I haven't linked Ned Wright's cosmology tutorial in a while. It has a lot of diagrams similar to this one, illustrating changes of coordinates, the horizon problem, and inflation, among other things. -- BenRG (talk) 06:36, 28 September 2010 (UTC)

That's a nice graph and clarification, thanks. --Mr.98 (talk) 15:41, 28 September 2010 (UTC)

UK Fuel Sources

Are there any more up-to-date numbers on the UK sources of fuel than these from the 1990s?

• gas – 39.93% (0.05% in 1990)
• coal – 33.08% (67.22% in 1990)
• nuclear – 19.26% (18.97% in 1990)
• renewables – 3.55% (0% in 1990)
• hydroelectric – 1.10% (2.55% in 1990)
• imports – 1.96% (3.85% in 1990)
• oil – 1.12% (6.82% in 1990)

--CGPGrey (talk) 17:03, 27 September 2010 (UTC)

It used to be easy to go to the local library and look these things up in the many volumes of UK National Statistics. However, now that they tell you to find it online, it always seems to me that the information that I want they charge for. Still, that said here's a link to their site : [4]--Aspro (talk) 17:16, 27 September 2010 (UTC)

This seems to have key data, with this providing more links. - Jarry1250 ^{[Who? Discuss.]} 18:39, 27 September 2010 (UTC)

The information here is live. --Heron (talk) 19:11, 28 September 2010 (UTC)

That is amazing -Thanks. Wonder if we should link to it in the article?--Aspro (talk) 20:32, 28 September 2010 (UTC)

If you're using it as a source, then that would be a good idea. --Heron (talk) 18:04, 29 September 2010 (UTC)

Why do Paper Clips work better than Copper wire in an electrical stimulation experiment?

Preparing for a Physiology class later this week, I've put together a square-wave stimulator, some electrodes, and tested them by shocking myself on the forearm (slightly dampened with some salt water.) One thing I discovered after comparing electrodes borrowed from another college nearby, made with paper clips (aluminum?), with the ones I made (copper wire) is that the shock is more detectable and dramatic with the paper clip electrodes.

I have no idea why this is, but would love to have an explanation before some student asks me.

Any ideas? Wevets (talk) 18:18, 27 September 2010 (UTC)

The response of the nerves in the skin to electric shock depends on the path taken by the electricity. You might like to put a milliammeter in the circuit to determine whether the current is actually larger with copper, but is flowing more evenly through the skin, thus causing less pain. I've found that a small current is more detectable if the cut ends of a finely stranded wire are gently stroked over the skin. Your paper clip is probably having a similar effect by restricting the main current flow to particular concentrated points. I trust that you have limited the current in your circuit to less than 3 milliamps for safety reasons. Dbfirs 18:33, 27 September 2010 (UTC)

The dominant factor here should be skin resistance. The composition of the electrode shouldn't make any noticeable difference. However, as Dbfirs says, the shape of the electrodes (you are using two, right?) could easily make a difference, and physiological factors that affect your GSR could also matter, if they aren't controlled. Looie496 (talk) 20:06, 27 September 2010 (UTC)

The skin resistance should be the same between the two tests, so I would suggest that the copper wire isn't as clean as you think it is... The "paper-clip" electrodes are probably made out of coated mild steel, not aluminium (too expensive and too brittle), and any coating that prevents surface oxidation will promote the passage of electric current to your suffering skin! Physchim62 (talk) 00:59, 28 September 2010 (UTC)

Aha - so the thickness of the wire rather than its composition is the important factor here? The copper is thicker than the paper clips. Perhaps I should also try with some thinner copper wire.

Don't worry - I'm not about to shock myself into oblivion. I'm being very cautious, and the equipment has built-in safety limitations I won't be tinkering with. Wevets (talk) 01:01, 28 September 2010 (UTC)

synchronized reflected vacuum energy waves fluctuations as the origin of Gravity: a case study: the black hole: a suggested mechanism of how gravity interacts with light waves, electromagnetic waves

The reference desk is a place for asking for information, not for lengthy presentations of original ideas -- collapsing due to length. Looie496 (talk) 20:00, 27 September 2010 (UTC)
The following discussion has been closed. Please do not modify it.
Hello Wikipedia, I have recently found your name (Wikipedia) as a reference on a book. So, I am going to ask the following question: could it be that: Gravity is, in my opinion, originally generated from the medium i.e. the Vacuum and Vacuum energy, on masses. the vacuum energy 10^107 joules per cubic centimeter creates a force (a repulsive in nature, since energy of vacuum is different from energy of mass and mass surface) on the mass surface, similar to surface tension force. The body of the mass provides a surface where vacuum energy fluctuations (waves?)could reflects off. these reflections of the vacuum energy would then become "synchronized" when reflected off the mass surface into high and low energy waves sinusoidal mathematical functions (orbits) mixed with other geometrical representing motion mathematical functions pending on Vacuum and Vacuum energy medium surrounding the mass. The density of the mass would be a deciding factor of the frequency of the vacuum energy synchronized reflection, in such a way that shorter wave reflected will form from a denser body (black hole). When two masses are within the fields of each others synchronized reflected vacuum energy waves(gravitational forces filed), they "shadow" each other from the non reflected vacuum and vacuum energy waves fluctuations; therefore falling into a lesser, a weaker repulsive medium, resulting in the observed attraction of the two masses to each other.--e:Y,?:G 06:37, 15 September 2010 (UTC) —Preceding unsigned comment added by E:Y,?:G (talk • contribs) The Black Hole event horizon support's the above suggested mechanism for Vacuum energy synchronized wave reflection off mass's bodies, in a way that the mass of the black hole is so dense that the vacuum energy waves reflected have wave length that does not support to carry the light waves or the electromagnetic waves as a lesser density mass bodies do. Or the unreflectiveness of light off the Black Hole mass body, is may be because these vacuum energy synchronized wave reflection off the mass's bodies, must reflects off a body not of the dimensions of the Black Hole mass i.e. less than 5 solar masses. The form these vacuum energy waves reflected off the mass must meet a certain geometrical dimensions. gravitational lensing is another example supporting the above suggested mechanism in a way that the reflected vacuum energy waves off dense bodies are not synchronized in the same way the lesser denser mass bodies do. Another conclulsion form the above suggested mechanism for vacuum energy synchronized wave reflection off mass's boies, is it must be in a certien formate for it to "carry" light and electromagnatic waves. and could be that, Taking into considerations E = M C^2, different type of matters with respect of their density's, differently reflects, i.e. in a different patterns, the Vacuum energy fluctuations (Casimir effect). In my opinion, the synchronized reflections of vacuum energy fluctuations off of a mass constitute the gravitational forces for that mass. In compression to a lesser density mass such as the earth, the matter in the black hole within the event horizon (equation of state), (UC Berkeley, September 24, 2010, high pressure experiments reproduce mineral structure 1,800 miles deep in the earth: where seismic waves have different patterns when run through post-pervoskite's zone of Magnesium silicate perovskite (MgSiO3) above the earth core). In my opinion, The Matter of a lesser density such as the earth matter, would react differently than the matter of the Black Hole to Vacuum waves, vacuum fluctuations, vacuum energy, which (the vacuum energy fluctuation ) when reflected off of these two different matters (equation of state) creates different synchronized reflected vacuum energy waves i.e. different gravitational forces; Where synchronized reflected vacuum energy waves is a gravitational force for a set, a defined system that has a specific equation of state. Also, The matter of the Black Hole (within the event horizon) may not reflects electromagnetic waves, since light have two components vectors: electric and magnetic, as it (the light) does reflects off of a lesser denser mass's such as the earth; therefore no light reflects off of a black hole matter, as observed. (UC Berkeley, September 24, 2010, high pressure experiments reproduce mineral structure 1,800 miles deep in the earth: where seismic waves have different patterns when run through post-pervoskite's zone of Magnesium silicate perovskite (MgSiO3) above the earth core). Or/and, the vacuum, vacuum energy of the atmosphere of a black hole will not support to carry light waves (or, most electromagnitic waves within the "atomspher" of the mass of the black hole. and light speedThat constitute that If we defined the atmosphere of a black hole to be the space between it's event horizon and it's mass surface, and if the rules of equation of state where to apply within the event horizon of a black hole atmosphere's with consideration to light travel; then E = M C^2 as an equation of state, could not probably be applied or used within the atmosphere of a black hole. E = M C^2 is does not apply in the black hole as a Equation of state for the absence of most electromagnetic waves spectrum (Hawking radiation existence?).--e:Y,?:G 19:58, 25 September 2010 (UTC)--e:Y,?:G 19:58, 25 September 2010 (UTC) —Preceding unsigned comment added by E:Y,?:G (talk • contribs The reflection of the vacuum waves off a mass's body could work as "sonar" in way or light reflection in way to evaluate a mass density.--e:Y,?:G 08:44, 15 September 2010 (UTC) —Preceding unsigned comment added by E:Y,?:G (talk • contribs) --e:Y,?:G 21:55, 17 September 2010 (UTC) --e:Y,?:G 18:24, 27 September 2010 (UTC) —Preceding unsigned comment added by E:Y,?:G (talk • contribs) thank you --e:Y,?:G 18:27, 27 September 2010 (UTC)

We can't really help you with things like this, but your "shadow" suggestion would imply that gravity varies by the surface area of an object, rather than its mass. You will also need to do the math and calculate these waves and show that the math works perfectly before anyone will take an interest in this. Ariel. (talk) 23:26, 27 September 2010 (UTC)

Electro-conductive body paint?

I saw a mention about electro-conductive body paint in an episode of C.S.I. Miami. Does such a thing really exist? Isn't it a pretty stupid idea? What prevents the current from entering the wearer's body, potentially electrocuting him/her? JIP | Talk 18:36, 27 September 2010 (UTC)

I don't know if this paint really exists, but if it does it would have a low resistance, while the body (the skin) has a higher resistance, so most of the current flows in the paint and not in the body. Skin effect has some info on a different mechanism that probably does not occur here, but might. Ariel. (talk) 19:30, 27 September 2010 (UTC)

It really exists. Check here. APL (talk) 19:34, 27 September 2010 (UTC)

The principle might be better appreciated by viewing this video, which shows things at the extreme end of sensible.[5]. Its about 60 seconds in that you start to see it in action.--Aspro (talk) 20:46, 27 September 2010 (UTC)

My neighbours wonder why I walk around with a tin foil hat on my head. This is the best reason I can give (and please don't try this at home as it it frightens the folks across the yard). It further demonstrates electricity (and mind controlling rays) taking the easiest route to ground. [6] --Aspro (talk) 21:05, 27 September 2010 (UTC)

Paramecium, communication, electromagnetic signals

At our article on Paramecium there is a paragraph in dispute. It is alleged that an experiment has shown that Paramecium may be able to communicate with other Paramecium over short distances with the use of electromagnetic signals. The dispute is over whether this is an April Fools' Day joke. Bus stop (talk) 20:33, 27 September 2010 (UTC)

We are discussing it on the Paramecium Talk page. Bus stop (talk) 21:07, 27 September 2010 (UTC)

It doesn't have to be a an April Fools joke to be wrong. It sounds wrong to me, and unless you can find more research that confirmed/reproduced it I would either remove it, or at least disclaim it with words such as "appeared", "one experiment", "unconfirmed", etc. Plenty of published papers turn out to be wrong. Ariel. (talk) 22:28, 27 September 2010 (UTC)

That is tantamount to original research. This phenomena is sourced to PLoS ONE and Scientific American. Bus stop (talk) 22:45, 27 September 2010 (UTC)

PLoS ONE is a reputable journal. So is Scientific American where it comes to articles, although it is equivalent to a news magazine where it comes to brief reports. Looie496 (talk) 22:57, 27 September 2010 (UTC)

You're right, it is OR. That's simply my sense after looking through it. The gold standard for science is reproducibility, and this study has not been (as far as I know anyway). So when you take that, plus other factors (single author, small sample size, etc) this doesn't seem good enough to me. But I accept that that is not the wikipedia policy. Ariel. (talk) 23:07, 27 September 2010 (UTC)

I emailed the author and asked him. Ariel. (talk) 23:17, 27 September 2010 (UTC)

Thanks for the forthcoming reply and for emailing the author. Bus stop (talk) 00:50, 28 September 2010 (UTC)

He replied:

Dear Ariel

Thanks for your interest.
Here my answers.

1) It is not a fools joke.

2) For the time being I am the only one who does this type of experiments with Paramecia but by far not the only one who does this type of experiment.

3) Actually, you can see my paper also as a repetition of previous studies but with another organism.

4) I apologize for not contributing on your blog.

A remark after reading your discussion.
        Single author does not mean bad work.
        Experiment 1 was 14 times repeated.
                This is a big sample size.

Please, do not talk in such a sloppy way about other people's work.
It took about 700 working hours to do all experiments, read into the literature, permanently hand out my paper to my critical collegues checking for errors, making it waterproof, double-check the statistics and so on ...
Note, the field is old (1923) but only few people work on it. These people have to convince the Scientific community about the reality of so-called bio-photons.
Join in in a construcitve way.

Yours friendly
Daniel Fels

PS: Maybe you and your friends have a (long) glance at this recent review.

Attached was a pdf titled: "Electromagnetic cellular interactions" by "Michal Cifra, Jeremy Z. Fields, Ashkan Farhadi". doi:10.1016/j.pbiomolbio.2010.07.003 Ariel. (talk) 09:56, 29 September 2010 (UTC)

I believe that restores seriousness to the premise that Paramecium may be able to communicate by electromagnetic radiation over short distances, with one another. This does not mean they own their own personal BlackBerry, but rather that they have perfected long before man did, the ability to project oneself wirelessly. Bus stop (talk) 16:14, 29 September 2010 (UTC)

Burning alcohol without a flame

Do metal oxides catalyze the oxidation of isopropanol by sodium hypochlorite? --Chemicalinterest (talk) 23:18, 27 September 2010 (UTC)

Hey, that's one of the simpler questions you ask! ;) Probably, but I don't know of any studies that have proved it. Metal oxides are usually good catalysts for any sort of oxidation reaction – exactly how good depends on a lot of other factors, of course. Physchim62 (talk) 00:49, 28 September 2010 (UTC)

I think the appropriate catalyst would be a redox or Lewis acid catalyst that is soluble but doesn't complex water too much. That is, Fe(III) is out of the question. Does Cu(II) decompose bleach? John Riemann Soong (talk) 03:52, 28 September 2010 (UTC)

Umm, I've used it in the lab -- hypochlorite just did its simple work and converted it into acetone without a catalyst. Of course, we waited an hour or so. As I recall, there are two steps in the bleach oxidation: (CH3)2CH--OH + OCl- ----> (CH3)2CH--OCl + OH- ----> (CH3)2(C=O) + Cl- + H2O. If you could convert that into a cyclic, concerted reaction maybe it would be faster. Of course, the alcohol isn't completely oxidised here.

Once you have acetone of course, you can start to go along the haloform reaction until you get a carboxylic acid (acetic acid) and chloroform. Lewis acid metal ions might stabilise the acetate (a negative anion -- not susceptible to another deprotonation) allowing hypochlorite to react further to yield another chloroform molecule and carbonate.

Chloroform isn't quite thoroughly oxidised though. It has one C-H bond left. And C-Cl bonds aren't the strongest thing ever. Did you want it to be oxidised by chlorine or oxygen? Well the reaction doesn't have to stop here either. Chloroform has an acidic C-H bond cuz of those three electron-withdrawing chlorines, so it can form dichlorocarbene in strongly basic solutions (I don't know if bleach is strongly basic enough -- usually I think people use potassium hydroxide) which can participate in all sorts of radical and electrophilic/nucleophilic reactions. But in water it's likely to form formic acid (via an acyl chloride intermediate).

Complete and orderly oxidation of hydrocarbons (and their alcohols) tend to be done by industrial-scale catalysts as opposed to done in the lab. John Riemann Soong (talk) 03:28, 28 September 2010 (UTC)

That is organic chemistry. I do inorganic chemistry! :) --Chemicalinterest (talk) 11:03, 28 September 2010 (UTC)

Here is my story. I mix bleach and rubbing alcohol. Nothing happens. I add CuO. It starts bubbling moderately rapidly. (I have yet to test whether the gas is CO₂) To a new solution of bleach and rubbing alcohol, I add Fe₂O₃. It starts bubbling a little more rapidly than CuO. To a new solution of rubbing alcohol, I add MnO₂. It is bubbling too. Is it the oxidation of alcohol to CO₂ and H₂O that makes the bubbling? --Chemicalinterest (talk) 11:01, 28 September 2010 (UTC)

Ahh, but isopropanol is an organic compound. You're sure you're not merely decomposing the hypochlorite? Also do you have any pH paper or way to evaluate how much the pH changes as you do this? The only obvious ways to evolve gas from isopropanol is you're dehydrating it (making isobutylene, a gas) or thru the haloform reaction to produce carbonate (which should take a while!). Do you have any glass apparatus through which you can capture the gas? John Riemann Soong (talk) 12:54, 28 September 2010 (UTC)

Intriguing if you're causing bleach to attack unactivated C-H bonds. The production of methanol via the orderly oxidation of methane is a major industrial problem, that if you solve, would earn you lots of money ;-). Your solution doesn't change colour? Hmm. Maybe somehow you're producing O2 + chloride. Also, bleach activated with some semi-fancy catalysts attacks unactivated C-H bonds, but doesn't completely oxidise the hydrocarbon. John Riemann Soong (talk) 13:02, 28 September 2010 (UTC)

I'm assuming it's not chlorine (otherwise you'd tell us, lol). Light a match and then snuff it until its glowing -- does it glow brighter near the evolved gas? (This would be really effective if you had some sort of glassware by which the gas could by channeled.) John Riemann Soong (talk) 13:27, 28 September 2010 (UTC)

I was thinking of this reaction: C₃H₇OH + 9 NaClO → 3 CO₂ + 4 H₂O + 9 NaCl Would that reaction be likely to occur? --Chemicalinterest (talk) 13:37, 28 September 2010 (UTC)

Just because you can balance the equation doesn't mean it occurs readily. ;-) Welcome to organic chemistry lol. Unlike bonds between say, metal ions (or other reducing agents) and inorganic compounds, C-C bonds and C-H bonds are strong -- on the order of 250-400 kJ/mol. For one -- isopropanol is a secondary alcohol. It's not likely to form a carboxylic acid (the precursor to CO2 being given off -- at least when there's no combustion involved) without the haloform reaction. I'm still intrigued where the gas came from though. Once you convert isopropanol to acetone, the carbons next to the C=O bond become "activated" and more susceptible to alpha-oxidation -- hence, haloform reaction. Have you tried the same thing with hydrogen peroxide?

Think about this first. What would the bleach attack? (Or maybe what would the catalyst help attack?) The weakest point, naturally. (In an environment full of strong bonds, the weakest bonds go first.) The C-H bond next to the oxygen is weakest (for various reasons you may or may not be interested in). So that would be oxidised first, and donated to Cl+ -- hence, OH- + HCl + acetone. The remaining C-C bonds and the C-H bonds are slightly actually stronger as a result of this (they are more polarised) -- the C-H bond becomes a little acidic. So the most obvious route would be haloform reaction, that takes advantage of the "activated" C-H bond. But do metal catalysts really catalyse the haloform reaction that fast? Wow. John Riemann Soong (talk) 18:18, 28 September 2010 (UTC)

That sounds unlike any mechanism I've seen published evidence for for the bleach oxidation of alcohols. To steal from someone up-thread, Just because you can draw a mechanism in which the bond you think is weakest breaks doesn't mean that's how the reaction happens. The most active/donatable electrons in isopropanol are lone-pair on oxygen, not a C-H covalent bond (otherwise reacting IPA with H+ would potentially oxidize it also rather than forming oxonium -> carbocation!). There's evidence for an alkyl hypochlorite intermediate, that then undergoes loss of your H as H+ in an E2-like reaction to give C=O. DMacks (talk) 20:58, 28 September 2010 (UTC)

I was simplifying it for him since he probably didn't need to know all that. Yes, AFAIK you get (CH3)2-CH-O- + HOCl, then alkoxide attacks the chloride side of hypochlorous acid, yielding (CH3)2-CH-OCl + OH-. (The alkyl hypochlorite is better able to stabilise the O-Cl bond than the hydrogen is.) The overall picture is that the C-H bond is weakest so that's the bond that gets "attacked" overall. AFAIK the rate-determining step is getting the deprotonated alcohol to attack the hypochlorous acid. A metal catalyst may turn it into a smoother, more concerted reaction. John Riemann Soong (talk) 21:06, 28 September 2010 (UTC)

Simplifing or omitting details that don't matter is good. Making statements that contradict basic science and known facts is very bad. It's simple to say the moon is made of cheese, but it's bullshit, and it's harmful to say it when you're trying to explain something about either cheeses or moons. You proposed the complete opposite of how the electrons move! DMacks (talk) 21:13, 28 September 2010 (UTC)

It's possible you're producing chloroform (which in turn reacts to produce all sorts of byproducts). Now I would expect it (unless you had an immensely selective catalyst) that little bubbles of gas (from like carbon monoxide + H2O, or carbon dioxide and hydrogen) would be produced though. Also, do you have a thermometer you could probe the reaction with? John Riemann Soong (talk) 18:29, 28 September 2010 (UTC)

Hydrogen peroxide would catalytically decompose with the metal oxide catalysts. I was thinking of oxidation by bleach in a similar way to burning. The bubbles were not insignificant, though. Enough to make some foam. Why does alcohol burn then and not produce chloroform or acetone or some other product? Oxygen is a weaker oxidizing agent than hypochlorite. The test tube does get quite warm, giving the title of this section. --Chemicalinterest (talk) 20:35, 28 September 2010 (UTC)

Bleach tends to oxidise by nucleophilic/electrophilic attack (depending on pH and the reductant and which side of the hypochlorite reacts first). That is, bleach tends to react via two-electron transfer.

During straight-up combustion, unreactive triplet oxygen more easily interconverts into reactive singlet oxygen -- which attacks via free radical mechanisms -- that is, one-electron transfer. Radicals abstract C-H bonds and C-C bonds like *that*. Bleach AFAIK isn't an oxidant via radicals. You can use hydrogen peroxide with metal catalysts btw -- I suppose you've tried -- but according to some papers I've read the H2O2 can survive long enough to induce significant reactions. John Riemann Soong (talk) 20:47, 28 September 2010 (UTC)

One more thing I did. I added household vinegar (5% acetic acid) to the reaction mixture and it did not significantly increase the reaction rate. See this for an argument whether that reaction made chlorine --Chemicalinterest (talk) 11:03, 29 September 2010 (UTC)

To all the mixtures? Fe(III) is a moderately strong Lewis acid but Cu(II) -- quite weaker (it's oxidising properties are stronger). John Riemann Soong (talk) 14:47, 29 September 2010 (UTC)

Cu(II)'s oxidizing ability (electrode potential +0.34) is weaker if Fe(III) is reduced to Fe (electrode potential +0.77). If Fe(III) is reduced to Fe then yes, Cu(II) is the stronger oxidant.

Oh well, this discussion does not seem to be producing a satisfactory explanation. I plan to test the gas to see whether it is CO₂. --Chemicalinterest (talk) 17:38, 29 September 2010 (UTC)

September 28

Through-glass photography

I would like to take photographs of my fish and assorted gastropods with my 7D 780 digital ELPH but find that the flash wipes out the object because of the glass and it's all way too dark without the flash. I tried taking a video and then taking pause shots from it, but they are not so clear. Any suggestions? DRosenbach ^{(Talk | Contribs)} 00:45, 28 September 2010 (UTC)

You could experiment with a polarization filter. To get rid of the reflection you need to look at the object from about 50° angle from the normal. It's explained in the Brewster's angle article. You could also try to put a polarization filter in front of the flash light to get even beter results. Count Iblis (talk) 01:06, 28 September 2010 (UTC)

(edit conflict) Sounds like a polarizer might help: Polarizing filter (photography). WikiDao ☯ (talk) 01:08, 28 September 2010 (UTC)

It seems to me much simpler to get some light pointing inside the aquarium and using a tripod, and no flash at all. The tripod allows you to shoot at slower shutter speeds, presumably the fish are not moving so fast that you cannot get shots that way. They might blur if they are moving faster than they usually do, but should be all right if they aren't. You will need to be careful not to just get reflections and glare from whatever light you point inside the aquarium, of course, and you may need to use faster "film speed" or whatever they call it in this digital age...

rc (talk) 01:49, 28 September 2010 (UTC)

If you need flash to take photos it'd be way too dark to use polarisers (-2-3 stops just by itself). Plus polarisers are not perfect and the extra flash power needed for the same exposure will offset any gains you get from a polariser. Get your lens right next to the glass surface to get rid of all reflections, then you can use flash all you want (unless it's prohibited). But yea, I second Ralphcook. Flash is no match to proper lighting inside the aquarium. --antilived^{T | C | G} 10:21, 28 September 2010 (UTC)

A remote flash will change the angle of the flash, so that it will be less visible to the camera. Covering it in thin white gauze will reduce the peak brightness and also reduce the reflection. Can't you use studio lights so that you don't need a flash? CS Miller (talk) 10:31, 28 September 2010 (UTC)

You can also sometimes avoid flash by opening up the aperture and increasing the ISO and slowing down the shutter. I dislike flash, so I typically push all three of these close to the limit. I get a lot of blurry or grainy pictures, but some of them come out looking nice, even in relatively low light. Paul (Stansifer) 14:03, 28 September 2010 (UTC)

Sorry to say, but if you ever thought of needing a flash it's not a job for a compact camera (at least, not right now). Built-in flash is out of question for fish photo - even if polarizers would work, the horizontal light will flood the scene in a most unpleasant way. The normal colours of the fish will be washed out in reflections from their scales, etc... Beef up your normal, top-mounted light. The amount of light recommended for intensive plant growth usually allows decent no-flash exposure times at low ISOs - assuming, of course, that the water is clear and the fish aren't too agile. East of Borschov 02:50, 29 September 2010 (UTC)

Earth's surface

After recalling something I heard years ago regarding a gyroscope so perfectly round that if it was scaled to the size of the earth, the tallest mountains and deepest ocean trench would measure only 2.4 m high (from here), I got to thinking about going the other way. That is, how rough/smooth would the earth be if it was scaled to the size of a tennis ball? Any ideas? Thanks, Mark 150.49.180.199 (talk) 01:11, 28 September 2010 (UTC)

Earth's radius: 6371 km

Mt. Everest: 8848 m

Tennis ball radius: 66 mm

"mini-Everest": ((66 mm) * (8848 m)) / (6371 km) = 92 microns

WikiDao ☯ (talk) 01:25, 28 September 2010 (UTC)

you'd have to include the mariana trench which is deeper (11km) then Everest is tall,so the total delta of earth surface is about 20000m, which makes the above about 200 microns, or 0.2mm. A similar anecdote I heard was that to scale, the earth is smoother then a billiard ball. Vespine (talk) 01:42, 28 September 2010 (UTC)

I just did a quick google and it looks like the billiard ball thing isn't quite true but it isn't far off. Vespine (talk) 01:44, 28 September 2010 (UTC)

Of course, if you want to consider how far the Earth is from being spherical rather than how rough its surface is, then you have to account for the variation between the equatorial and polar radius, which is about 0.35%. Your tennis ball with radius 66 mm would be nearly half a millimeter wider at the equator than through the poles. --Anonymous, 04:40 UTC, September 28, 2010.

OOB/Armaments question - NATO choppers and recent airstrikes into Pakistan

Read an interesting article today about NATO air assets based in Afghanistan flying into Pakistani airspace to return fire after receiving "direct small arms fire" from ground forces there. This left me with two questions, unfortunately neither of which were answered in the article - (1) What sort of helicopters are we talking about? (2) What is the risk of "direct small arms fire" to modern attack/assault gunships? I'm assuming they're firing AK-47s or other variants? The Masked Booby (talk) 01:23, 28 September 2010 (UTC)

Here's a list of military aircraft that have crashed in Afghanistan, which gives a general sense of what's being used over there (and how often different things get shot down, as opposed to just crashing; no comment on specific tactical vulnerabilities;). WikiDao ☯ (talk) 02:05, 28 September 2010 (UTC)

Articles I have read identified them as Apache helicopters - and while all the articles made a point of never identifying their national owners, one article pointed out that only the U.S. uses Apaches. [7] —Preceding unsigned comment added by 75.41.110.200 (talk) 13:03, 28 September 2010 (UTC)

On a side note, NATO later backpedaled and said that the helicopters hadn't actually entered Pakistani airspace, only their rockets had. :) --Sean 15:19, 28 September 2010 (UTC)

The AH-64 Apache article says it is designed to remain flyable after taking fire from one of these, which is well beyond small arms fire. --Sean 15:25, 28 September 2010 (UTC)

Cigarettes

Do cigarettes cause gynecomastia —Preceding unsigned comment added by Kj650 (talk • contribs) 02:00, 28 September 2010 (UTC)

It appears that it is commonly believed that smoking marijuana may be positively correlated with the development of gynecomastia ([8]). I found one small study that failed to find any correlation, though the sample size was tiny, so I wouldn't read to much into it ([9]). I have seen no evidence that smoking tobacco is correlated with gynecomastia. Buddy431 (talk) 03:12, 28 September 2010 (UTC)

How proteins really work

I've learned that a protein's function is tied to its specific shape, but looking at models of proteins, they just look like coils of twine. If I take several coils of twine and put them in a box and shake them up, they'd all just be a big mess of knots, with each piece of coiled twine being no more or less jumbled, regardless of how I bent it at the outset. So, how the heck do proteins function as a result of their shape? What am I missing?

Are there any dynamic models out there, showing protein interaction, as it happens? ☯  Zenwhat (talk) 02:22, 28 September 2010 (UTC)

Wow. What you are missing is the very complex way they are "knotted" up. That is, while, say, myoglobin is a very complex, knotty looking structure, all myoglobin looks like all other myoglobins, and they all work the same. Also remember that in any given sample of a protein, you have billions of billions of billions of molecules, so imagine taking your long bit of twine, knotting it up to a very specific set of instructions, and then doing it again several billion times, exactly the same way. THAT is how proteins work. It is complex, but that's not the same thing as random. Articles you want to read to give you an overview are Protein tertiary structure and Protein quaternary structure and follow the blue links from there. The basic principle is that the folding of the protein you describe is actually predetermined by the exact amino-acid order (the protein primary structure). Specific amino acids cause certain types of folds and kinks in the chain. For example, proline has a ring structure which forces a very specific kind of bend, while cysteine will form disulfide bridges with other cysteines, which causes very specific kinds of folds. There are also acid-base effects based on local pH, for example Histidine is very sensitive to small changes in pH near physicological pH, and so its effect on the overall shape will change depending on the pH. This is just a very basic overview, what you are looking at is the way in which chains of hundreds of units, selected from among 22 or so building blocks, can not only be organized, but also how they interact with each other and their environment.--Jayron32 03:13, 28 September 2010 (UTC)

I have to say, screw things like "exact amino acid order" in these explanations -- that doesn't help people understand protein structure. You can reverse the amino acid order sometimes and it won't make a difference (sometimes amino acids are essentially just filler, meant to separate structures, etc.). But substituting a hydrophobic amino acid in the middle of a hydrophilic chain can drastically change things of course. John Riemann Soong (talk) 03:20, 28 September 2010 (UTC)

The secret lies in organic chemistry. If you want to talk about enzymes, the other amino acids provide a skeleton against which the active site amino acids can do their work -- act as acid, base, nucleophilic catalysts in a concerted reaction in a smoother transition state. Some proteins are very water-soluble don't have a shape until induced that way by another protein (these proteins are really hard to crystallise). Also, don't forget the proteins we know about tend to be proteins we've crystallised -- so we have a bias already. The coils are arranged in a very specific way sometimes -- determining how they can open up become a receptor, or fit snugly inside another protein.

But they are not in fact rigid structures and this is often key to their structure. John Riemann Soong (talk) 03:20, 28 September 2010 (UTC)

Another thing with proteins is that it's like they have little "magnets" inside them, and the proteins will only stick together if the magnets match up exactly with the magnets on the receiving protein. The complicated shape, plus the positioning of the magnets means that proteins will only lock together with exactly the right target. So it's not like random coils of twine, it's carefully matched sets. Ariel. (talk) 03:26, 28 September 2010 (UTC)

We have an article, protein folding, that ought to be helpful here. Looie496 (talk) 03:28, 28 September 2010 (UTC)

You may want to check out the article on sickle cell anemia, or more specifically, the 3rd paragraph of the genetics section. It's written with too much scientific gobble-de-gook, but in essence, it's stating how a single point mutation that causes a single amino acid change can lead to such drastic results because of the so called "sticky patch" that it causes when two regions of hydrophobic amino acids are now able to be exposed to each other. DRosenbach ^{(Talk | Contribs)} 04:12, 28 September 2010 (UTC)

I think that the answer to your question is that proteins don't act like twine; they're too "slippery" to really "knot" in a macroscopic sense. For example, I've never heard of one end of a carbon chain getting shoved through the hole in a benzene ring and getting snagged in there - it just doesn't work like that. Effects like "quantum tunneling" and the Heisenberg uncertainty principle mean that with enough energy one thing can slip right past or right through another if it has to, though I don't think the covalent chains actually cross through one another with any appreciable frequency.

Also bear in mind that molecules move really, really, really fast relative to one another. Of course, that's because it's actually a very small distance. But to consider the kind of witchcraft molecules are capable of, you can take a little oligonucleotide primer and put it in with an entire 3 billion base human genome, give it two minutes or so to "anneal", and there it is: stuck fast to the one exact complementary sequence in the entire freaking human genome. (Well, at least, that's the theory... generally some repetitions and tinkerings of the experiment are required to get this to work the way it's supposed to... see PCR) Now imagine that oligonucleotide flipping around in the breeze, jumping along this strand and that strand to and fro, gently tagging onto one nucleotide here and four nucleotides there and so forth until it gets hooked up to all 20 or so exactly matching so that it's so tightly bound that it hopefully doesn't pop back off the DNA again.

Between these two things, the point is that an ordinary protein gets the chance to flip around a bazillion different ways, until finally it happens to ball up in a shape so perfectly comfortable that it mostly stays that way. Wnt (talk) 06:56, 28 September 2010 (UTC)

At least related to the question is a statement of Levinthal's paradox: the number of possible conformational states for a protein (different ways to jumble up the 'coils of twine') means that sampling even a small fraction of the possible states would take longer than the age of the universe, so why do proteins fold at all (sometimes in fractions of a second)?

The response comes in two parts: Anfinsen's dogma, which says something about the likely stability and accessibility of properly-folded states; and the idea of a folding funnel, which suggests that the energy landscape in conformational space is funnel-like — meaning, very roughly speaking, that early steps towards the correct folded shape tend to favor a further collapse of the protein down to its final fully-folded state. TenOfAllTrades(talk) 16:21, 28 September 2010 (UTC)

My opinion is that this "paradox" is a bit overwrought — as you point out, it's based on the absurd idea that a whole protein receives no feedback from potential energy changes until it finds its final perfect form. In practice the protein secondary structure (alpha helix and beta-pleated sheet) is fairly predictable from the amino acid sequence and can be obtained by an exploration of the landscape at a fairly local level. Additionally, proteins tend to be composed of conserved protein domains which have evolved stable folds independently and don't mix very much. Of course, none of these things are absolute... Wnt (talk) 17:41, 28 September 2010 (UTC)

I'm pretty sure that even Levinthal didn't really believe his naive observation to be genuinely paradoxical. He simply used it as a jumping-off point to discuss why the protein folding process must be cooperative. (Think of it as a proof by contradiction — if we first assume that proteins fold by an unbiased random walk through conformational space, we quickly reach the conclusion that folding cannot happen within the age of the universe; therefore folding must be cooperative; QED.) TenOfAllTrades(talk) 21:13, 28 September 2010 (UTC)

Dichlorocarbenes and water

I've yet to use this reaction practically in real life...but, dichlorocarbene organic reactions can be performed in water? How is this possible? Don't you want an inert solvent that won't attack your carbene? John Riemann Soong (talk) 03:55, 28 September 2010 (UTC)

Thinking through your proposal, you are suggesting that oxygen attacks the vacant orbital of the carbene...which would give a carbanion? Not so stable--the carbene was originally formed when a similar carbanion spontaneously and easily did alpha-elimination (ejecting halide). Carbenes aren't really stable stable, you don't usually isolate a flask of them and then continue with another step, but make them in situ where they react promptly with something else (our article suggests they are formed in an organic layer so there are lots of the organic reactant but little of the water present). DMacks (talk) 05:22, 28 September 2010 (UTC)

Are carbenes soft Lewis acids/bases? Well yes, it would give a carbanion, but you can have a proton shift which effectively gives HCCl2-O-H (dichloromethanol) -- which readily becomes formyl chloride + HCl and then formic acid. John Riemann Soong (talk) 05:27, 28 September 2010 (UTC)

My point is that the immediate reaction that forms them is approximately the reverse, and is in an organic solvent (tends to exclude water--biphasic, just like the article states) that contains some other reactive component. DMacks (talk) 05:46, 28 September 2010 (UTC)

When people mix bleach and acetone for cleaning purposes....they say they form chloroform...but do they risk forming carbon monoxide in the process? John Riemann Soong (talk) 06:15, 28 September 2010 (UTC)

No, I am pretty sure the major problem in the mixture of bleach and acetone would be Phosgene, Diphosgene, and other analogs. Chlorine + carbonyl = nasty stuff. --Jayron32 06:20, 28 September 2010 (UTC)

On the other hand, the reaction of bleach (at normal "laundry" strength) and acetone is fairly slow compared to bleach oxidation of other materials. Acetone is a popular (co)solvent for bleach oxidation of some secondary alcohols (I think acetic acid is also added). DMacks (talk) 06:50, 28 September 2010 (UTC)

The reaction of bleach and acetone is an example of the haloform reaction. It forms chloroform and acetic acid, not carbon monoxide, nor phosgene. Physchim62 (talk) 12:53, 28 September 2010 (UTC)

That is the primary pathway yes. But I believe chloroform may go on to react in hypochlorite solutions to cause all sorts of mess! John Riemann Soong (talk) 18:27, 28 September 2010 (UTC)

Microfin

what is a microfin used in heat transfer applications —Preceding unsigned comment added by 115.111.61.66 (talk) 04:41, 28 September 2010 (UTC)

See Heat sink, which explains the use of fins in this regard. See also Fin (extended surface), which also deals with heat transfer properties of fins. Keep in mind that microfin just means "really small fin". --Jayron32 05:26, 28 September 2010 (UTC)

slow combustion

Are there any strategies being investigated to say, effectively burn something at -20C? Maybe by microwaving a dry ice bath full of organic material and some oxidant like perchloric acid? The idea is to track combustion pathways and maybe identify "weak points" in flammability. John Riemann Soong (talk) 05:33, 28 September 2010 (UTC)

Define combustion... After all, technically rust is a combustion product, just a really slow moving combustion. --Jayron32 05:38, 28 September 2010 (UTC)

Combustion tends to be autocatalytic, yes? But I don't want it to be too autocatalytic. John Riemann Soong (talk) 06:13, 28 September 2010 (UTC)

Combustion is autocatalytic over the flash point or Fire point temperature; if the rate of heat dissipation is great enough, due to low ambient temperature, then it won't sustain a burn because the local temperature stays too low to overcome the activation energy. This is a major problem when dealing with internal combustion engines in very low temperatures, in very low temperature the gasoline will not sustain combustion. It's even more pronounced with diesel, which is why diesel fuel is sold in winter and summer formulations. --Jayron32 06:26, 28 September 2010 (UTC)

Is it possible to engineer an experiment where the reaction is just slightly over the self-sufficiency rate? I'm thinking if black body equilibrium can be established at a lower temperature, but at say, 273K where the reaction is not so "crazy", then maybe combustion could be more easily studied. John Riemann Soong (talk) 07:14, 28 September 2010 (UTC)

• I'm not well versed in this chemistry, but I think that (as explained in combustion) a key detail is that triplet oxygen carries a spin angular momentum. This momentum needs to go somewhere (conservation of spin quantum number) when the reaction takes place. Since the fuel and/or product is usually some ordinary hydrogen or carbon containing compound, not a weird diradical like O2, that means that either the other reactant has to carry an opposite angular momentum (a free radical) to cancel it out, or else the oxygen needs to be energized up to singlet oxygen, whose spin is balanced out, before interacting. (As we just covered recently, the exact amount of angular momentum needed to do that comes from the photon, no matter what its frequency!) Either takes energy. This energy can come from a highly reactive fuel (pyrophoric) - Wikipedia gives triethylborane as an example of something that burns at -20 C. I don't know what temperatures are needed for various other compounds listed in pyrophoric. I also don't know how stable singlet oxygen is, which would be interesting, since as I understand you should be able to expose anything to the stuff, no matter how cold it is, and have slow oxidation with production of heat. Your call on whether that's cheating... Wnt (talk) 07:49, 28 September 2010 (UTC)

What about an alternate oxidant like perchloric acid? John Riemann Soong (talk) 13:13, 28 September 2010 (UTC)

Operators in QM

Why does :${\bigg (}\langle \phi |A{\bigg )}\;|\psi \rangle =\langle \phi |\;{\bigg (}A|\psi \rangle {\bigg )}$? Are we just forcing operators to have this property, or is this the result a more basic mathematical property? Why would we force operators to behave this way? Thanks. 74.15.136.172 (talk) 10:52, 28 September 2010 (UTC)

$|\psi \rangle$ is basically just a column vector, $\langle \phi |$ is a row vector, and A is a linear transformation, which can be thought of as a matrix. Then $\langle \phi |A|\psi \rangle$ is matrix multiplication in the usual sense, which is associative. Rckrone (talk) 12:38, 28 September 2010 (UTC)

The equation is actually the definition of $\langle \phi |A$. Looie496 (talk) 21:42, 28 September 2010 (UTC)

Crackle or hiss from radio

When I tune a radio so that it is not recieving any broadcast, where does the noise come from? Is it an echo of the big bang? Thanks 92.28.249.130 (talk) 13:15, 28 September 2010 (UTC)

Technically there's some component of the remnants of the Big Bang in white noise, but in practice, it's a non-factor which is dwarfed by solar or terrestrial (or even other cosmic noise) sources. Lightning and electrical equipment are prime sources of the noise heard on a consumer radio. — Lomn 13:50, 28 September 2010 (UTC)

Citation please? As a layman, I have to say this sounds doubtful. Comet Tuttle (talk) 18:36, 28 September 2010 (UTC)

As a former EE I share your doubts. East of Borschov 02:39, 29 September 2010 (UTC)

A realtime map of worldwide lightning strikes can be produced by analyzing the 'static' picked up by a handful of antennas scattered worldwide. IIR they settled on a 100KHz standard frequency which was low enough to contain lots of atmospheric static, yet high enough so that lightning signals at that frequency don't travel all the way around the earth. (The extra 'echo' would mess up their algorithm.) 128.95.172.173 (talk) 08:56, 29 September 2010 (UTC)

Any idea what the proportions are? Thanks 92.28.249.130 (talk) 14:22, 28 September 2010 (UTC)

Cosmic noise makes it sound like it is exceedingly small. --Mr.98 (talk) 15:39, 28 September 2010 (UTC)

Big Bang (book) by Simon Singh says that, if you were to observe static on a television screen then 1% of that would be background radiation from the horrendous space kablooie. Brammers (talk/c) 16:43, 28 September 2010 (UTC)

Wikipedia used to have an article on the horrendous space kablooie, but it now redirects to Calvin and Hobbes. -- BenRG (talk) 20:35, 28 September 2010 (UTC)

Particularly for an AM radio, we hear atmospheric lightning discharges, crackle due to electrical discharges from switching of power, and corona from high voltage transmission towers. In addition, we hear fish tank thermostats, and electric blankets and other electrical devices switching on and off. We also hear ham radio transmissions, defective doorbells, pizza ovens, medical diatheremy devices, relays in vintage pinball machines, and car ignition systems. Edison (talk) 04:59, 29 September 2010 (UTC)

On the FM band most of the noise would come from the transisters in the earliest stages of the receiver. There will always be some kind of noise floor. If your radio was not making this there is also thermal radio emissions from anything above absolute zero, including the earth, and sun. Graeme Bartlett (talk) 12:33, 29 September 2010 (UTC)

Why does the M16 have a higher muzzle velocity?

On the XM8 article it says that the XM8 uses polygonal rifling which would allow the rifle to have a higher muzzle velocity than the M4 or the M16. But it says that using a 20 inch barrel, it's muzzle velocity is only 916 m/s while the M16 rifle with a 20 inch barrel has a muzzle velocity of 948 m/s. Why does the M16 have a higher muzzle velocity, especially when the XM8 is supposed to have polygonal rifling. ScienceApe (talk) 14:32, 28 September 2010 (UTC)

I have to run quickly, but I will provide an answer based on what I know to be fact and my memory (which is often faulty). From memory, the XM8 is optimized to use a 24" barrel. So, optimal muzzle velocity is at 24". The fact... polygonal rifling is not designed to produce faster muzzle velocity in general. It is designed to reduce muzzle velocity loss when the barrel is shortened below optimal length. So, both riflings will produce similar muzzle velocities when barrels are the same length (on the same rifle). When you cut the barrel length in half, the standard rifling will take more of a hit on velocity than the polygonal rifling. The comparison you are looking at is using the optimal length M16 barrel and a 4" short XM8 barrel. You should expect a hit on muzzle velocity with a shortened barrel. -- kainaw™ 15:06, 28 September 2010 (UTC)

Conventional rifling on the left; polygonal rifling on the right.

It's a good point, though. All else being equal, polygonal rifling should give a higher muzzle velocity (except possibly in the case of lead bullets, see Lead bullets and polygonal rifling). The information at XM8 is poorly cited. WikiDao ☯ (talk) 17:51, 28 September 2010 (UTC)

The manufacturer says the M16 has a muzzle velocity of 948 m/s; the Federation of American Scientists says it's 853 m/s. Who are ya gonna believe...? ;) WikiDao ☯ (talk) 21:48, 28 September 2010 (UTC)

Wait, since when was the XM8 optimized for a 24" barrel? As far as I know, there isn't even a configuration for the XM8 that uses a 24" barrel. ScienceApe (talk) 23:06, 28 September 2010 (UTC)

Note kainaw's caveats. :) The XM8 comes in flavors of Sharpshooter/AR, Assault, and Compact (20, 12.5, and 9 inch barrels, respectively). WikiDao ☯ (talk) 23:39, 28 September 2010 (UTC)

And the articles now read: 916 m/s for 20" XM8, 853 m/s for the M16 but then there's the AR-15 article... WikiDao ☯ (talk) 23:43, 28 September 2010 (UTC)

Acceleration of rocket

what is the acceleration of a rocket —Preceding unsigned comment added by 41.221.209.5 (talk) 16:30, 28 September 2010 (UTC)

You'll need to be a little more specific. Do you want the minimum acceleration and velocity required for any rocket to escape Earth's gravity, or do you want information on a specific rocket or system like the Space Shuttle? Regards, --—Cyclonenim | Chat  16:46, 28 September 2010 (UTC)

Not all rockets escape Earth's gravity; see model rocket. Nyttend (talk) 17:21, 28 September 2010 (UTC)

Sorry that is correct, I just made the assumption the OP meant those which escape Earth's gravity. Not sure why. Regards, --—Cyclonenim | Chat  17:54, 28 September 2010 (UTC)

Also see skyrocket. We need to know what sort of rocket you mean.--Shantavira|^{feed me} 18:40, 28 September 2010 (UTC)

A rocket accelerates because of Newtons laws - for every action, there is an equal and opposite reaction. When exhaust is expelled out of the back of the rocket, in order to balance the motion the rocket must move in the other direction. See also Conservation of momentum. Ariel. (talk) 18:56, 28 September 2010 (UTC)

irrelevant pedantry
The following discussion has been closed. Please do not modify it.
Ariel, a minor point of pedantry. A rocket doesn't accelerate because of Newton's Laws. I suspect the earliest Chinese rockets powered by black powder were accelerating centuries before Newton was born. Rockets (and other bodies) accelerate in accordance with Newton's Laws, but they don't require Newton's Laws in order to change their velocity. Dolphin (t) 22:45, 28 September 2010 (UTC) Yah, that was pretty pedantic. I can understand "in accordance with", but what do you mean by "they don't require Newton's laws"? Of course they do - if they didn't have them, they couldn't move. And the laws existed before Newton was around of course - he just named them, he didn't create them. Ariel. (talk) 02:15, 29 September 2010 (UTC) I disagree. I think our Scientific law article makes it pretty clear that a law is merely a human summarization of how the underlying principles behave. I think it'd be more appropriate to say that rockets behave according to the principles that are embodied (and approximated) in Newton's laws. But at this point we've drifted far afield of the original question. Buddy431 (talk) 02:27, 29 September 2010 (UTC)

Acceleration is the force from the engine divided by the mass of the rocket. All else is byplay, vanity, and folly. Edison (talk) 04:52, 29 September 2010 (UTC)

Acceleration is the net force on the rocket, including the engine force, the force due to gravity, and air resistance (if in the atmosphere). It's most certainly not just a function of engine force and mass. Buddy431 (talk) 16:11, 29 September 2010 (UTC)

The questioner did not specify it was starting from a launchpad on Earth, as you assume. I could assume it was starting in space. Or someone could assume it was clamped down in a test stand, such that it does not move relative to the test stand. Edison (talk) 16:29, 29 September 2010 (UTC)

Does science yet have an explanation for how bees can fly?

It's one of those common knowledge "facts" that people quote at you, that science says that bees should be unable to fly because their wings are far too small for the size/weight of their bodies and that no-one can come up with a convincing explanation as to how they manage to get airborne at all. Is that still true? If so, are there any promising theories? --95.148.108.177 (talk) 22:29, 28 September 2010 (UTC)

It isn't true to say science says that bees should be unable to fly because their wings are far too small for the size/weight of their bodies. It is equally untrue to say no-one can come up with a convincing explanation as to how they manage to get airborne at all.

It is easy to come up with a very simple model of flight, and then show that this simple model does not allow bees (or birds or bats or fish) to fly. But the fact that bees do engage in flight just shows that the very simple model of flight is inadequate.

Science makes observations of the natural world and sets out to explain these observations, and how all observations are part of an orderly universe. Science does not develop theories and then set out to determine which parts of the natural world conform to scientific theories and which parts don't. Dolphin (t) 22:38, 28 September 2010 (UTC)

@95.148.108.177: You are quoting folklore, not "fact". Have a look at our article: Bumblebee#Flight. --- Medical geneticist (talk) 22:45, 28 September 2010 (UTC)

@Dolphin51: Some "science" develops theories and sets out to conform discoveries to scientific theories. You should get what I mean. --Chemicalinterest (talk) 00:21, 29 September 2010 (UTC)

Are you willing to reveal which science you have in mind? If you reveal some details, others can comment on whether they agree. Dolphin (t) 01:36, 29 September 2010 (UTC)

I'm pretty sure from his history CI is referring to evolution. His claims have been discussed many times before, I see no need for a rehash Nil Einne (talk) 02:18, 29 September 2010 (UTC)

http://www.sciencedaily.com/releases/2006/01/060111082100.htm "We're no longer allowed to use this story about not understanding bee flight as an example of where science has failed, because it is just not true," Dickinson says. Hcobb (talk) 01:51, 29 September 2010 (UTC)

Footage of the behavior in question. WikiDao ☯ (talk) 02:29, 29 September 2010 (UTC)

Why are muscle cells multinucleated

Everywhere on the internet where someone asks this question they get the answer "Because embryonic muscle cells fuse", which doesn't really explain anything- what purpose does this fusion have? 149.169.249.172 (talk) 23:45, 28 September 2010 (UTC)

Because it works. Nature does not have purpose, other than "it works." If the cells were individual, normal cell sized, muscle fibers would be very short. Having long, undifferentiated fibers, without definitave cell membranes between them, works better for what muscles do, which is to contract along their length. If you want to make a rope, you want long fibers, not short little ones. --Jayron32 23:50, 28 September 2010 (UTC)

Multinucleate cells don't have multiple nuclei because it's useful, it's just a byproduct of cell fusion. Take two individual myotubes, each with one nucleus. They then fuse together, so that there are now two nuclei in the combined cell. It doesn't harm the cell to have two or more nuclei, so there is no evolutionary pressure to remove this feature. Regards, --—Cyclonenim | Chat  13:51, 29 September 2010 (UTC)

September 29

A system of two electrons

They are initially released at infinity (zero potential energy). One has a velocity of +v, and one has a velocity at -3v. I'm supposed to find out their minimum separation....

By conservation of momentum, I know that the total momentum of the system is always -2mv and that the overall internal energy of the system has to be 5mv^2 (0.5m(3v)^2 + 0.5mv^2).

At minimum separation, both particles are travelling in the same direction in the negative x-direction, with equal velocities (hence separation is not changing). If their overall momentum is -2mv and their kinetic energies are equal, then their overall kinetic energy must be mv^2, yes?

So this means 4mv^2 must be stored in electric potential. Since potential energy for each charge is kq^2/r, overall potential energy is 2kq^2/r. 4mv^2 = 2kq^2/r, so r = kq^2/2mv^2. However the program says this is the wrong answer. Help? John Riemann Soong (talk) 03:38, 29 September 2010 (UTC)

If I understand the question: Why would they be traveling in the same direction at minimum? Wouldn't they bounce off of each other? The overall momentum is a red herring - they only thing you care about is the relative velocity (which is 4v), the absolute velocity is meaningless. Ariel. (talk) 04:35, 29 September 2010 (UTC)

Well one is moving faster than the other initially so one would lose its forward kinetic energy more quickly than the other and starts going in the other direction. Minimum separation is achieved when their velocities are equal. Well, I fixed it anyhow. The key was that potential energy of the charge pair was kq^2/r, not 2kq^2/r. John Riemann Soong (talk) 04:59, 29 September 2010 (UTC)

I guess I didn't understand the question. Ariel. (talk) 06:53, 29 September 2010 (UTC)

Polyamidoamine epichlorohydrin

What's polyamidoamine epichlorohydrin? —Preceding unsigned comment added by Kj650 (talk • contribs) 06:11, 29 September 2010 (UTC)

here is a pdf about it (got it by typing the above into Google. You can do that yourself too!). It appears to be a polymer composed of three monomer units, those being adipic acid, epichlorohydrin, and diethylenetriamine. From the google search I did, it appears to be used a waterproofing additive to paper; to help paper retain its strength when wet. --Jayron32 06:20, 29 September 2010 (UTC)

how is it made —Preceding unsigned comment added by Kj650 (talk • contribs) 17:04, 29 September 2010 (UTC)

Two of the first page of google hits clearly identify themselves as articles or patents related to the manufacture of the chemical. DMacks (talk) 17:42, 29 September 2010 (UTC)

Physics: charges

Imagine that the sun carries a net excess positive charges while the earth carries a net negative charge. If the excess charge is proportional to the mass Q=KM(sun) and Q=-KM(earth), (a) what charges would be needed on the earth and on the sun in order to provide electrostatic attraction equal to the gravitational attraction (b)what is the value of the proportionality constant k(in coulombs/kg)? —Preceding unsigned comment added by 41.204.175.75 (talk) 07:17, 29 September 2010 (UTC)

This looks like a homework question. The Reference Desks will provide links to useful articles, but there is no benefit to you if we do your homework for you. Dolphin (t) 07:29, 29 September 2010 (UTC)

I'm not convinced science is Opie's forté. --Sean 16:03, 29 September 2010 (UTC)

Why the "standard" in "standard gravitational parameter"?

The standard gravitational parameter $\mu$ of a celestial body is the product of the gravitational constant $G$ and the mass $M$ of the body,

$\mu =GM.$

Why is it called "standard" as if there were many other gravitational parameters for the body in question? —Bromskloss (talk) 09:33, 29 September 2010 (UTC)

There is also the Gaussian gravitational constant for a celestial body, which is just a different way of expressing µ. The "standard" in the name, implies that it is the parameter that is expressed in the simplest manner with regards to the International System of Quantities. Physchim62 (talk) 14:02, 29 September 2010 (UTC)

Peas and potatoes without fertiliser?

As a survivalist I plan to grow potatoes indoors in pots. If I grew them with peas in the same pot, would nitrogen fertiliser be required, since peas fix nitrogen from the atmosphere? Also, could a potato be genetically engineered to fix its own nitrogen? —Preceding unsigned comment added by 80.1.88.10 (talk) 13:55, 29 September 2010 (UTC)

Technically, it's a symbiotic bacterium that's fixing nitrogen, see Legume#Fixation_of_nitrogen_in_the_soil. Crop rotation is the traditional way to reap the rewards of this nitrogen. I don't think synchronous growing would work as well for this pairing, but see Companion_plants for more information on you idea. Genetic engineering of potatoes to form their own symbiosis whith rhizobia seems unlikely, though perhaps not impossible. Composting will also be important for you as an agrarian survivalist. SemanticMantis (talk) 15:04, 29 September 2010 (UTC)

I don't think it would work if you grew them with peas as opposed to after peas. The nitrogen is fixed in the Root nodules. Farmers normally get the extra benefit from the roots by leaving them in the ground and ploughing for the next crop. Because the nitrogen fixation comes from mutualism by way of a nodule, genetically engineering the bacteria to favour potatoes and engineer the potatoes to form nodules might be possible one day. But beware and remember that old Chinese proverb: “She who cooks potatoes and peas in the same pot, is being unhygienic”.--Aspro (talk) 15:05, 29 September 2010 (UTC)

Nice Chinese proverb. Any idea what it might be getting at? I like to add some potatoes to my split-pea soup...SemanticMantis (talk) 15:08, 29 September 2010 (UTC)

I have no idea what it means but it leads nicely to the next thing that every survivalist should recycle as a good rich source of plant usable nitrogen. Urine#Agriculture--Aspro (talk) 15:19, 29 September 2010 (UTC)

Isn't it just a pun on pea/pee? Incidentally, urine can be used as a satisfactory source of nitrogen, though the smell may be disagreeable if you're using it indoors. Buddy431 (talk) 16:09, 29 September 2010 (UTC)

As SemanticMantis says Crop rotation is the traditional way and there is more info in our article Organic farming. Too much nitrogen can be bad though for some crops including potatoes and carrots. [10]. --Aspro (talk) 15:35, 29 September 2010 (UTC)

RE genetic engineering - yes it should (hopefully) be possible one day. The genes involved in the formation of the symbiosis appear to have been "borrowed" from the much older mycorrhizal symbiosis between plants and fungi, which potatoes already have. Here's the most recent free review I can find. (We don't seem to have any discussion of the genes involved in mycorrhizal symbioses at the moment.) Oh and if you're growing plants indoors, light is going to be much more of a worry than nitrogen, and running high power lights isn't very survivalist, as AFAIK the only thing you can grow profitably indoors is illegal. Smartse (talk) 16:30, 29 September 2010 (UTC)

That is not true if you have a room with many windows or a greenhouse. Googlemeister (talk) 18:08, 29 September 2010 (UTC)

Touchscreens and finger damage

Is there any evidence it's unhealthy to use a touchscreen since you're pressing hard on to a solid wall over and over? There's also the friction of repeatedly dragging your fingers across glass. If it's not damaging then why do keyboards have springs in the firstplace? TheFutureAwaits (talk) 14:33, 29 September 2010 (UTC)

Keyboard keys are a normally open switches. The spring brakes contact again once your finger leaves it. There is no evidence as far as I know. Don't press so hard. If you were a farm labourer you would know what 'hard' was.--Aspro (talk) 14:40, 29 September 2010 (UTC)

Aspro has it. The friction is surely no risk, unless you count toughened skin or calluses as unhealthy. Potentially, if you pressed hard all day with the same finger, you could conceivably develop Repetitive_strain_injury that finger, but this is a stretch. Additionally, the spring-loaded keys give tactile feedback to the user, which has worked out pretty well. SemanticMantis (talk) 14:58, 29 September 2010 (UTC)

Keyboards have springs because they're made of buttons, and that's how buttons work. Without the springs (Or some similar mechanism) there would be nothing to hold the key 'up' (and therefore 'off') when you weren't pressing on them.

Touchscreens are much more technologically complicated. APL (talk) 16:41, 29 September 2010 (UTC)

Ferric nitrate pictures

Why does iron(III) nitrate have two different pictures with two different colors? Both of them say that they picture the nonahydrate. --Chemicalinterest (talk) 14:48, 29 September 2010 (UTC)

One of the picture captions is wrong. A variety of sources ([11], [12]) identify the nonahydrate as being a pale violet color, as shown in File:Watchglass2.jpg. The preparation of anhydrous ferric nitrate is a finicky process, and the product isn't very stable. The synthesis was described by D.J. Lovejoy and A.J. Vosper in 1968. They report that the anhydrous form is a "yellow-brown involatile solid" – perhaps something that looks like File:Iron(III)-nitrate-nonahydrate-sample.jpg, but I wouldn't count on it for the article – which slowly decomposes in air to form ferric oxide.

This paper describes thermal decomposition of the nonahydrate in still air. It is possible to cook off water to get the dihydrate, but not the fully anhydrous form. (Further heating of the dihydrate causes a decomposition to ferric hydroxide.) TenOfAllTrades(talk) 16:11, 29 September 2010 (UTC)

It does look like there is some oxides or hydroxides in the picture. --Chemicalinterest (talk) 17:33, 29 September 2010 (UTC)

peppers and blood

What effects would eating hot peppers have on a human's blood pressure? Googlemeister (talk) 15:49, 29 September 2010 (UTC)

By hot peppers, you are referring to capsaicin. This is a very complicated issue. Some studies have shown that capsaicin inhibits transition from non-hypertension to hypertension. Other studies have shown that increased capsaicin has caused temporary but drastic increases in hypertension. There are many studies in mice and dogs. One that I found interesting was application of capsaicin in the nostril (technically, deep in the nostril to the sinus cavity) and how it heavily correlated with an increase in blood pressure. So, you can certainly find a study that backs whatever view you want to have on the topic, but the overall answer is that the relationship between capsaicin and hypertension is complicated. -- kainaw™ 15:56, 29 September 2010 (UTC)

After further research, I have found multiple studies in humans that indicate capsaicin interacts with hypertension medication as well - usually in a negative way. So, if a person is taking hypertension medication and consumes a large amount of capsaicin, there is a probability of lowered anti-hypertension effect from the medication. -- kainaw™ 17:13, 29 September 2010 (UTC)

Oxidation of pyrogallol

I notice that the article about pyrogallol mentions the fact that it readily absorbs oxygen. It does not however give a balanced equation of the reaction. Does anyone know what the equation looks like so we can add it to the article. Obviously the first bit is C6 H3 (OH)3 + O2 ---> but what would the products be? Maybe water and something else? At any rate it should be added to the article. Anyone? Jay-Sebastos (talk) 19:26, 29 September 2010 (UTC)

The ring is very nucleophilic. The oxidation will lead to a benzoquinone like motif -- a Michael acceptor. Note that pyrogallol is very nucleophilic enol -- (an aromatic enol, but still an enol) -- so another pyrogallol molecule will then attack this Michael acceptor. This aldol addition reaction rearranges to form purpurogallin. [13] John Riemann Soong (talk) 19:39, 29 September 2010 (UTC)

Yes. See also this scheme from Bull. Chem. Soc. Jpn. (2004) 77, 1201-1207.

Ben (talk) 20:08, 29 September 2010 (UTC)

Thanks a lot for the help. Yes this would make sense. We should probably add this to the article about pyrogallol as well. Jay-Sebastos (talk) 20:16, 29 September 2010 (UTC)

Oscar question

I bought two 1.5 inch oscars the other day and now my parasitic snails (which I enjoy in my tank) are gone -- I had counted about 30 of them, and I can find 2 now. How can the oscar eat the snails with their snails? There's no way 25 shells can fit in his guy and how is he going to digest the shells? DRosenbach ^{(Talk | Contribs)} 20:32, 29 September 2010 (UTC)

If they eat crayfish, as Oscar_(fish)#Feeding suggests, then I can't see they'd have much of a problem with snails. The first link on this google search says "For a start, Oscars eat snails in the wild, so periodically your captive Oscar may eat snails, knocking back the snail population." Which would seem to be your problem. Or rather, your ex-snails problem :( --Tagishsimon (talk) 21:20, 29 September 2010 (UTC)

Bra-kets

Does $\langle A|B\rangle \langle C|D\rangle =\langle A|\langle C|B\rangle |D\rangle$? 74.15.136.172 (talk) 22:59, 29 September 2010 (UTC)

No, you can consider the expression in the middle, |B><C| as an operator. It projects a ket on |C> and then rotates it in the direction of |B>. If the identity you propose were to hold, then this operator would be proportional to the identity operator, which is clearly false. Count Iblis (talk) 23:15, 29 September 2010 (UTC)

Alright, does this change if B = C? 74.15.136.172 (talk) 00:17, 30 September 2010 (UTC)

Smell Illusion

If I sniff a strong smell or odour, could it distort the subjective smell of other odours afterwards? I'm wondering if there could be an analogy with colour, as looking at one colour can in some circumstances distort the perception of other colours seen aftwards or adjacently. Thanks. 92.24.190.229 (talk) 23:13, 29 September 2010 (UTC)

Yes it can. I don't know that there are distinct parallels with colour theory, but aroma is the major component of what we think of as flavour. Adding or removing aromas from a dish changes its flavour significantly. E.g. Ferran Adria's 2003 dish involving pan-fried shrimp served with a sprog of rosemary for sniffing while eating. You could also look to the world of perfumes; professionals in the industry sniff coffee beans to 'reset' their noses. Inhaling strong aromas will distort how weaker aromas smell after, as well. → ROUX ₪ 23:20, 29 September 2010 (UTC)

Animal memory

Other than elephants, what animals are associated with having a good memory? —Preceding unsigned comment added by Procrastinatus (talk • contribs) 23:57, 29 September 2010 (UTC)