Wikipedia:Reference desk archive/Science/2006 July 25

From Wikipedia, the free encyclopedia

Humanities Science Mathematics Computing/IT Language Miscellaneous Archives
The page you are currently viewing is an archive page. Whilst you can leave answers for any questions shown below, please ask new questions at one of the pages linked to above. This will insure that your question is answered more quickly.

< July 24 Science desk archive July 26 >


Contents

[edit] Name that syndrome

I was trying to remember the name of a syndrome I read about a few years ago. I remember some of the typical symptoms: late birth (2-3 weeks past due), slightly shorter than normal legs, overly sensitive abdomen (touching the abdomen causes discomfort), and very bad nearsightedness. Does that ring a bell with anyone? --Kainaw (talk) 00:25, 25 July 2006 (UTC)

Not really. Couldn't hit anything on OMIM - do you think that it's genetic? InvictaHOG 10:26, 25 July 2006 (UTC)
That is what I was trying to find out. I remembered the syndrome (the "can't touch the chest and belly" part is what stuck in my head). I just couldn't remember if it was genetic or not. --Kainaw (talk) 12:31, 25 July 2006 (UTC)

[edit] Hurricane to Typhoon

Anyone know the term or name of a tropical cyclone that goes across its basin and regenerates into another storm in a second basin. (e.g. cross International Date Line and becomes a typhoon from the remants of a hurricane) (if you post storm name prefer an example from situation i just told you). Hello32020 02:02, 25 July 2006 (UTC)

Hello, hello, you seem to be mixing several things up, which makes it difficult to understand what you mean. The international dateline runs through one single basin, the Pacific Ocean. Or is this about there being two names for the same phenomenon? DirkvdM 06:58, 25 July 2006 (UTC)
I believe the question is: "Assuming we have 'Typhoons' over the Pacific Ocean and 'Hurricanes' over the Atlantic Ocean, what is the official term for a hurricane that crosses over into the Pacific or a Typhoon that crosses over into the Atlantic?" Hurricanes do hop across Central American into the Pacific. They normally keep their name, such as Hurricane Rita. They do not become Typhoon Rita. Also, once named, they stay named even if they go back and forth between a storm and hurricane. That is why you will see maps that show something like "H Rita...TS Rita...H Rita..." to show it changing between hurricanse and tropical storm. As for crossing the International Date Line, has a named hurricane every gone that far? Once they cross the equator, the winds try to force the storms upward and then eastward, so it would be difficult to keep chugging all the way across the Pacific Ocean. --Kainaw (talk) 16:31, 25 July 2006 (UTC)
The north eastern and north western Pacific are considered to be two separate basins in the case of typhoons/hurricanes. -- Koffieyahoo 07:57, 26 July 2006 (UTC)
  • In reply to the original question, no, there's no particular term for a hurricane that forms in the East Pacific or the Central Pacific Ocean (where the name for a tropical cyclone is "hurricane") into the Western Pacific (where the name is "typhoon"). If Hurricane Tito crossed the IDL, it would be called Typhoon Tito, but its name doesn't change, nor it gets a particular designation. (And yes, hurricanes have done that in the past. This is not unheard of: Super Typhoon Paka and Super Typhoon Oliwa have done so. There are a few times cyclone names change, but they are listed on our Tropical cyclone article, though. Titoxd(?!?) 06:51, 26 July 2006 (UTC)

[edit] Question about atoms and electrons

My question is what is the power source that keeps electrons in orbit around the nucleus? It's been a long time since college physics for me, and I can't recall if I ever heard a good explanation of this, other than it's quarks and quantum mechanics and stuff.

Yesterday I loaded a pallet with a ton of bricks onto my trailer, it'll be a few days before I can unload it. So in the meantime I got to thinking... all the atoms in my trailer under the pallet are resisting the weight of the bricks, and gravity is pulling the bricks down. Conceivably if I never unloaded the bricks, the atoms in the trailer would go on supporting the bricks until the end of time. The electrons will keep orbiting, the atoms will not ever collapse under the weight of the bricks above them. So what powers that repulsive force that keeps the electrons in their orbits?

Except that everything made by humans eventually decays and falls apart. It might take a very long time, but some time before "the end of time" the trailer and the bricks would disintegrate. Your question relates to the period before that happens. I don't know the answer. Sorry. JackofOz 02:45, 25 July 2006 (UTC)
Hopefully a physicist will respond with a more nuanced answer... but pending that, my understanding is that the electrons aren't really in orbit around the nucleus and therefore don't have to radiate energy like an accelerating body. They just sit there... but since they're waveforms as much as particles, they sit in orbitals rather than at single defined points. --Allen 02:56, 25 July 2006 (UTC)
At the quantum level I think it boils down to the weak force and strong force. Gravity doesn't even exist at the quantum level. Emmett5 03:04, 25 July 2006 (UTC)
Sorry, try again next time. The answer has nothing to do with the strong or weak nuclear forces. Allen's answer is mostly correct, except that electrons do radiate energy — but only when they're in an excited state. Because of quantum mechanics and the uncertainty principle, the electron has a spatial distribution even in the lowest possible state. It can't possibly "fall into" the nucleus because that would restrict its position to an exact value, and therefore its momentum would become totally undefined and it would shoot right back out. —Keenan Pepper 03:15, 25 July 2006 (UTC)
Playing around with this applet might help you get some intuitive grasp of it. If you try to confine the particle's position to a narrow spike, it explodes outward and after a short time you have no idea where it is. —Keenan Pepper 03:20, 25 July 2006 (UTC)
[Note: posted after an edit conflict with the terser Keenan Pepper. Sorry for the duplication, but hopefully the longer explanations help someone.]
It doesn't take energy to resist a force; it takes energy to, well, give something more energy. So it takes energy to lift your pallet (giving it more gravitational potential energy), or to throw your pallet (giving it (more) kinetic energy), or to heat it (giving it more thermal energy, which boils down to electric potential energy and kinetic energy of particles within it). You're not doing any of those things, so no energy is required. Put another way: if all those atoms were "doing something" or exerting themselves in some way, where would their efforts go? Certainly if they were releasing energy somehow, it would have to go somewhere, and nothing's happening.
Put yet another way: consider the alternative. Suppose that the pallet, as you intuitively suspect, is in danger of having its "power" to hold the bricks fail. What then? Presumably the bricks fall, but the only place for them to fall is through the material of the pallet (or the ground, or...). Because atoms are basically rigid (because of the Pauli exclusion principle and the Heisenberg uncertainty principle, which when applied to highly compressed atoms requires them to have a lot of energy), they would have to overlap to accomplish this, and this would require more energy to arrange (i.e. to fight all the electrical repulsion between like charges). So the answer is that the bricks cannot fall because they do not have enough energy, not that they manage to stay up because they have some to spare. (With enough energy, the bricks could in fact merge with the pallet. But this amount of energy corresponds to vaporizing both objects and squishing them together, or (more extremely) the creation of degenerate matter or so.)
I think this confusion arises so commonly (although often in other contexts) because, due to what could be called a design flaw in animal muscles, we must exert energy to maintain our body in a non-neutral position, even if we are not applying that energy to anything else (think about holding your foot off the floor forever while seated). This is because there is some slippage in muscle cells under load (even the load of our own weight), and they must continually reassert themselves to maintain their position. So intuitively, we think of energy as force multiplied by time — how hard we strain times how long we do it. But all the energy that we expend as we tire holding our leg up just goes into heating the muscle as the cells slip and regain their position repeatedly. Mechanically — that is, treating our body as a black box — the energy is force times distance instead, and has no dependence on how long we (or the pallet) must hold things up.
On what is really an unrelated note, it is noteworthy how quantum mechanics explains how an "orbiting electron" avoids radiating as accelerating charges normally do (e.g., in a radio tower, where electrons rushing up and down generate radio waves). Quantum mechanically, the electrons are not in fact moving, but are simply in the vicinity of the nucleus, never going anywhere (and having no classical motion around it either). They still get to have angular momentum (as do normal rotating objects), but because they are not localized they can "rotate" in this sense without accelerating (remember that rotating objects classically undergo centripetal acceleration).
Finally, (to Emmitt5) neither the weak nor strong nuclear forces are involved in this situation; all human experience outside of nuclear reactors or so is the gravitational and electromagnetic interactions (the other two forces) entirely. And gravity exists everywhere; typically on such small scales it is negligible, but it controls the larger organization. Perhaps what you are thinking about is the current theoretical problems unifying gravitation and quantum theory. Hope this helps. --Tardis 03:40, 25 July 2006 (UTC)
Bravo Tardis - you hit the nail on the head. It is often confusing that muscles must use energy continuously to exert a stationary force, but that is due to the molecular dynamics within the muscle cells; applying a stationary force does not consume energy over time - it is only force along a distance that does work. --Bmk 05:56, 25 July 2006 (UTC)


Yes, thank you Tardis, you understood the question I was trying to ask very well, better than I did clearly! You've given me some more terms to look up, that'll keep me busy for a while.

All of the atoms on the trailer have a random component. There is a statistical probablility the one atom supporting the most weight will gather enough energy to 'come loose', or gain enough energy to overcome the activation energy of seperating itself from the bonds holding it in place and become a 'free agent' so to speak. At that time the downward force on it will tend to cause it to have a higher chance of moving downward than upward. When that happens the load will drop down a fraction of an atomic diameter. The same thing can happen to other atoms which are not supporting the most weight, but the effect will be less pronounced. If you wait long enough, the trailer will unload itself, so just go have a beer. You will have an opportunity for lots of beers.

[edit] Unit conversions (title added)

can anyone tell me what 9 kg of lpg equates to in m3, what does 1m3 of natural gas equate to in kg and is it possible to co-relate the two, thanks``` Hatch

What's the temperature and pressure? —Keenan Pepper 03:24, 25 July 2006 (UTC)
hmm, seems you've added a pressure comment since i clicked edit... anyway, hatch, try ideal gas law. you need a few parameters you haven't given. Xcomradex 03:28, 25 July 2006 (UTC)
Nitpick: Keenan's comment was added after the last time you downloaded this page. When you clicked 'edit' determines whether there was an edit conflict. DirkvdM 06:57, 25 July 2006 (UTC)

thanks sorry about ending up on someone else's item

[edit] Where did the hemp go on my farm?

I live in Canada, but my family owns a some land in southern Italy that my granparents used to farm. We have went there a few times, and my dad told stories of his childhood. He has told me several times that our land had lots of marijuana on it. He remembers using it for rope, he also remembers others in the around using it to get high. He has told me when he was a kid he remembered many farms and even just land on the roadside was teaming with marijuana, now the land is devoid of it. No one in the area can remember anyone actually spraying our land (it was left unkept for years), and this has happened to the whole state anyways (public land, huge sections of unmaintained forests, personal land ect). So if no one knows of someone actually physically removing this plant, then how else could it have been done? Some kind of chemical I assume? Anyone have an explanation? In a place like southern italy that still has massive amounts of unused bush land, isn't removing this plant from an entire province a serious undertaking?

Hanez --216.211.78.176 04:01, 25 July 2006 (UTC)

PS I placed this question in the Science category because I assume this was done with a chemical...

Good one. Loads of hemp was grown in Europe for centuries. It was used for all sorts of purposes, most notably the ropes that were used on the boats that explored the world, so it was extremely important. And it's a weed and weeds are indeed hard to get rid of. So, indeed, it must have survived in the wild. One thing I can think of is that it is a light-loving plant (what's that called in English?), so it grows in open fields, is therefore very visible and may have been over-harvested by smokers (you have to harvest it before it pollinates). But the cannabis variety used for ropes is not the best for marijuana. Marijuana is the name for the drug, not the plant. The highest concentrations of THC are found in the flowers, but for rope you need long fibres, meaning long internodes, so you get fewer flowers. And those few flowers contain less THC, so it's not very potent as a drug. So that makes the over-harvesting unlikely.
But there's another possible answer: maybe this variety was bred so specifically for fibre, resulting in so few flowers that it took human intervention to pollinate. Bummer. :)
By the way, here's a story I read once. The writer of this story was in a bar in Bavaria in the very conservative south of Germany in the 70's or thereabouts. At one table there were a bunch of hippies, at another table a bunch of elderly locals. The locals were talking about those hippies, about 'kids these days', that sort of thing, and at one point one says "I bet they smoke marijuana too", upon which another asks "What is marijuana anyway?". So the writer turns around and says "It's hemp." "What do you mean it's hemp, we used to smoke that when we were kids." "Yes, and didn't you feel anything?" "Yes of course, that's what we smoked it for." "Well, that's marijuana." A nice example of preconception based on misinformation.
So the rope-hemp isn't quite as potent. But that doesn't mean you won't feel anything if you smoke it. It's just a much milder high. I've heard it said that illegality has led to weed that is way too strong (more compact and thus easier to transport), as a result of which people have forgotten what a nice high is like. Especially Dutch weed is now so potent that some say it should be classified as a hard drug. And indeed I only buy the cheapest stuff and smoke very small quantities of it. I wish there were milder varieties. Another good reason to end the illegality. DirkvdM 07:18, 25 July 2006 (UTC)

Look up 'wild hemp' on Google. It has a very small native region in Asia. All of the rest of the wild hemp, called 'ditch weed' in the US, is a leftover from cultivation. The US spends millions to destroy wild hemp (which has almost no THC!). That may have happened in Italy as well, or the hemp might have just died out. Extensive fibre-hemp cultivation has now started up in Canada. --Zeizmic 12:15, 25 July 2006 (UTC)

[edit] animals

Can a Salamander hurt a dog? Do salamanders have any sort of 'venom' they could use as a defensive mechanism?Possibly a 'Dusky Salamander' species. It has blackish-brown (no spotting) coloring and is approximately 2.5 inches in length. We are living in a northern suburb of Minnesota. I have a 15# shitzu-poodle. Thank you, in advance, for your efforts in finding the answers to my questions.--68.187.149.254 05:13, 25 July 2006 (UTC)

Salamanders aren't poisonous. The only vaguely similar poisonous thing is a gila monster, but that doesn't sound similar enough. There aren't even any other poisonous lizards from anywhere in the world that could be an escaped pet (except komodo dragons, and they are a bit bigger). However, if the dog ate it, and the dog is now sick, there could be several reasons, including the possibility that the salander had just eaten poison. If the dog is sick, take it to a veterinarian right away. If it isn't sick, probably nothing to worry about. Notinasnaid 08:02, 25 July 2006 (UTC)

Im pretty sure i heard of a deadly poisonous lizard in the desert somewhere. Some travelers boiled one by mistake in their coffee and both died.

There are poisonous newts, and newts are salamanders. They are not venomous, as venom is injected poison; to be poisoned by a newt, one must eat it. See this link for some good references. I remember seeing a piece on a TV program about the story of the camper killed when a newt (probably a rough-skinned newt) crawled into his coffee pot and was boiled along with the beans; however, I couldn't find any reliable references from Google.
At any rate, if you think your dog has been playing with or has eaten a newt, get veterinary care right away. --Ginkgo100 talk · contribs · e@ 20:41, 26 July 2006 (UTC)

[edit] Chemical Composition of CEP 2563

Can You Give me the Chemical Structure Of the CEP 2563 as Tyrosine Kinase Inhibitor.

Looks like it the compound in the graphical abstract of this article:
"Prodrug esters of the indolocarbazole CEP-751 (KT-6587)" . doi:10.1016/S0960-894X(98)00328-X. 
DMacks 05:59, 25 July 2006 (UTC)

[edit] The Wolrd bank

I need the major criticism points about the World Bank and the developing countries debt, And the defense that was taken against those accusations. As well as, the proposals given to form policies to solve those issues.

ps: you can always guide me to useful websites or links in regard of this topic.

thanks

Salloya La Douce

Hi. Might i suggest you start with the World Bank article, specifically the section on criticsm and some of the references therein (e.g. [1] [2] [3])

[edit] Flexible PVC products

I would like to increase the tensile strength of soft and flexible PVC products. ( eg. like rubber band) The processing method is through extrusion.

How can I crease the tensile strength to the product. What should I added during processing of PVC

Expecting your reply at the earliest--220.225.124.50 06:00, 25 July 2006 (UTC) L . srinivasan

[edit] Intestinal Worms

How long can intestinal worms exist in a body? In this case there are no major symptoms besides occasional "stomach discomfort" that has lasted for nearly a year.

Successful parasites can exist for the lifetime of the host. So can delusions of parasitism. alteripse 10:29, 25 July 2006 (UTC)
Just a note: Our GI clinic gets people every day complaining of intestinal worms. It is very rare that they have worms. They just have loose bowels. They normally explain it to the patient by saying, "Your intestines are lined with little fingers that grab and push the waste through. If it is too watery, they grab and pull on each other instead of grabbing and pulling on the waste. Because of the vast number of nerve endings in the area, this can cause extreme pain that radiates all the way up into the chest and arms. So, eat more ruffage." --Kainaw (talk) 16:41, 25 July 2006 (UTC)

It's almost impossible to prove that someone does NOT have intertinal worms because:

Lack of evidence is not evidence of lack

The only way to be absolutely sure is to examine every square millimetre of someone's intestine. Ohanian 22:54, 25 July 2006 (UTC)

After they are dead, of course? alteripse 10:19, 26 July 2006 (UTC)
But at the same time, if a doctor finds nothing wrong with you besides loose bowels, and loose bowels adequately explain your symptoms, why assume you have magical worms which evade detection but give no additional symptoms? Having said that, the anon should probably make an appointment with a doctor who can actually look at them and make a diagnosis and recommendations. Skittle 15:25, 26 July 2006 (UTC)
It should very much be possible to prove that someone does not have intestinal worms at least to reasonable standards by checking for tapeworm DNAin the stool via Polymerase Chain Reaction. Of course, you'd need a reasonably specific DNA sequence, but that should be doable. Given the sensitivity of PCR, if a negative result turns up several times on several different sequences, you can be pretty sure there are no worms. --OliverH 19:36, 29 July 2006 (UTC)

To answer the original question, I believe tapeworms can live indefinitely inside a person without killing them. StuRat 03:21, 27 July 2006 (UTC)

[edit] Formula info.

I would like to find a formula, if it exists, regarding the relationship between water's boiling point and pressure. For example I would like to find out, what is the temperature for witch the water stars to boil at 150 mbar.


Thank you and best regards, Alex

  • I think you have better luck if you tried finding a graph. - Mgm|(talk) 13:29, 25 July 2006 (UTC)
I agree - I've never seen any kind of formula, piecewise or otherwise. Here's a link to a phase diagram for water (which incidentally is what you should search for in google). This is just one of many - I just picked the first hit. Wait, hold the phone! It turns out that if you hold the mouse over the phase-change lines in the diagram, it shows a polynomial fit equation for the line! Have fun. --Bmk 14:48, 25 July 2006 (UTC)

[edit] Water and ice questions.

1. What is the state of water at 100°C?

2. Why does ice float on water?

3. Are there other substances whose solid state float on its liquid state?

Thanks in advance. --Siddhant 11:35, 25 July 2006 (UTC)

For #3, have there been experiments with diamonds and liquid carbon? --Kainaw (talk) 16:53, 25 July 2006 (UTC)
For #3, you don't need to get some complicated. Any material that expands when it cools will float on it's liquid state. There aren't many of them, but they do exist. Type metal for example expands, (although I haven't checked if the liquid state is more dense, perhaps it expand only during the solid state). 71.199.123.24 17:55, 25 July 2006 (UTC)
That #1 Does not have sufficent information to be answered. Sindweller 18:14, 25 July 2006 (UTC)

[edit] how to anliyze talc(3MgO4SiO2H2O)

what methods can we use to anlyze : - the brightness of talc - the quantity of Magnesium and Silica can we increase the brightness of talc? how if you know the way you can send an email to <removed email addess> or mobile on <removed cell phone number>. it is for my collage please

Why are you making a collage about analysing talc? I don't know that it'd be very interesting to look at. Perhaps you are putting talc onto your collage, in which case increasing the brightness (I suppose) might be useful. However, as brightness is a measure of the amount of light given off an object, talc has none at all. 89.138.69.138 08:43, 26 July 2006 (UTC)

[edit] Galaxy/Balck hole

I have heard on several occasions that galaxies are believed to orbit around supermassive black holes, and some other things, in which case I have several questions.

  1. Will the whole galaxy fall intothe black hole eventually?
  2. Why are galaxies never depicted with jets emitted along the z-axis, where smaller black holes do when they have accumulated a Accretion disc, and it is well established that small black holes (by comparison) can emit ones that span our galaxies height?
  3. Do black holes last forever?
  4. If they do, will the universe not eventually end up as one huge black whole, or atleast a massive pool of black holes moving apart?
  5. Also, can stars exist outside galaxies?

Thank you Philc TECI 18:10, 25 July 2006 (UTC)

  1. Pretty much. Some rogue stars could escape, however.
  2. Don't know. Supermassive black hole notes that such black holes have many properties differing from stellar-sized versions, perhaps that's why?
  3. Current theory suggests "no". See Hawking radiation for small ones and heat death of the universe for the big ones.
  4. From the second link immediately above, theory suggests that the universe's matter will end up as all (or virtually all) black holes. Then it'll change.
  5. Yep. See Intergalactic Wanderer for examples.
— Lomn | Talk 18:24, 25 July 2006 (UTC)
Have you read our article on Supermassive Black Hole Sindweller 19:20, 25 July 2006 (UTC)
For question 2, such jets exist and are the most luminous known things in the universe. In most galaxies the central supermassive black hole is quiescent, having consumed all significant surrounding matter. But occasionally they get matter to feed on, flaring up as a quasar or a blazar. Weregerbil 20:15, 25 July 2006 (UTC)
Surely every time they feed, the additional matter means there garivitational strength increases and so more matter is placed within they're reach, so why don't they consume the whole galaxy relatively quickly? Philc TECI 20:48, 25 July 2006 (UTC)
The gravitational force of the black hole increases, yes — but not the gravitational force of the system. There's just as much mass in close proximity to the black hole after "feeding" as there was before. — Lomn | Talk 20:52, 25 July 2006 (UTC)
Yeh that is true. As a readjustment of the question in light of your point. Does the reorientation of the mass affect the gravity of the system at all. Philc TECI 22:13, 25 July 2006 (UTC)
From what I've read about quasars, as the center becomes more massive, it collapses tighter on itself. Add to this the reduction of mass around it, it spins faster - like a figure skater spinning faster when she pulls her arms in. That pushes the matter in the system outward, which slows down the spin - but also separates it from the deathly edge of the black hole. As it slows down, it creeps back toward the black hole and the whole cycle begins again. Also, on top of that balance, there is the theory that the black hole is losing mass all the time by radiating energy outward - isn't that Hawking's theory?? I don't know - I'm just a computer programmer. --Kainaw (talk) 16:11, 26 July 2006 (UTC)

I don't see any reason why an equilibrium can't be eventually reached where all stars are in stable orbits about a central black hole, just like planets orbiting a central star or moons orbiting a central planet. StuRat 03:09, 27 July 2006 (UTC)

[edit] Ointment Battle

If hydrocortisone and neosporin were to get into a fight, who would win? 199.201.168.100 19:18, 25 July 2006 (UTC)

List of JAG episodes. Melchoir 21:04, 25 July 2006 (UTC)
Huh? As for the fight, I suppose it would depend on whether allergens or bacteria were present. --Ginkgo100 talk · contribs · e@ 20:01, 27 July 2006 (UTC)

Neosporin, of course! But only if it were an endurance battle, since neosporin is petroleum based, and hydrocortisone is not. --Teh Janitor 03:52, 30 July 2006 (UTC)

[edit] Will the Universe tend towards a single point

I was reading up about the N-body_problem and found it quite interesting. I made a small program that would display the interaction between two bodies of equal mass with the intention of generalising it for many bodies. When I ran the program with one fixed body and one body effected by gravity everything worked as expected,I got an orbit that was an infinite loop. However when I allowed both bodies to be effected by each others gravity every starting condition that I tried caused the bodies to collide. They oscillated round a centre point in smaller and smaller elipsces.

I was under the impression that it was possible to set up a stable gravitational system. However these very limited results seem to say they opposite.

Either theres a bug in my program (quite likely) or its not possible to set up a stable two body gravitational system (and by extension a stable n body system).

So, is it possible to set up a stable gravitational system? If so would anyone be able to explain how, ideally with a plot of the two bodies, every plot I've seen so far only show one body moving. Thanks for the help

Oh yes. In fact, if two bodies aren't on an immediate collision course, and they aren't moving fast enough to "escape" each other's gravity, they always enter a stable orbit -- in fact, a closed orbit. See Two-body problem. Melchoir 22:16, 25 July 2006 (UTC)
It sounds like your model system is 'leaking' kinetic energy through the accumulation of small rounding errors. There will be a limit to how far forward you can project in time before these errors become overwhelming. TenOfAllTrades(talk) 22:31, 25 July 2006 (UTC)
Without seeing the program you've written, I can't say for sure, but I'm almost certain you are experiencing round-off error. Basically, at every time step (I'm assuming you used a simple kind of discrete time step algorithm), the positions and speeds and accelerations of the two bodies are subject to small errors, which build up over time and result in macroscopically unphysical behavior. Melchoir is quite correct that two point particles cannot collide unless they are initially on the degenerate orbit of direct incidence - the zero angular momentum orbit, and otherwise must form either stable orbits or escape from each other to infinity. Of course, if they are particles with positive finite radius, they can, and do collide in real life. This is all classical gravitational physics...i don't really have the willpower to think about general relativity right now. (ps - tenofalltrades beat me to the answer, but i'm posting anyways) --Bmk 22:36, 25 July 2006 (UTC)
And taking look at nature, there are literally millions of binary star systems out there, where two stars orbit around each other in a stable configuration. And to assuage Bmk's fears, it works pretty much the same way in general relativity, with the small exception that ultra-massive objects (eg neutron stars, black holes) in a close orbit will radiate gravitational waves, which, if I remember my physics classes correctly, should cause the system to gradually lose energy and the bodies to spiral towards each other. However, this effect is very weak, and even two neutron stars orbiting each other will be able to maintain their configuration for a long time. — QuantumEleven 06:53, 26 July 2006 (UTC)

[edit] Eating raw mushrooms

Are any mushrooms safe to eat raw? Knowing that there are plenty which are outright poisonous, and a few which must be cooked for safety. I am wondering specifically about store-bought varieties which are commonly served raw.

See Talk:Edible_mushroom for additional links, resources, and discussion. ∴ here…♠ 22:23, 25 July 2006 (UTC)

What do you mean? You pretty much answered your own question with "I am wondering specifically about store-bought varieties which are commonly served raw." Wizrdwarts (T|C|E) 01:57, 26 July 2006 (UTC)
I didn't even know there were any mushrooms that were safe to eat, but only when cooked. Are there any like that besides the false morel? Button mushrooms are perfectly safe to eat raw. —Keenan Pepper 02:54, 26 July 2006 (UTC)
I doubt that any types of so-called 'edible' mushrooms would be sold at reputable stores if they weren't completely edible, via any conventional preparation method.--Anchoress 02:59, 26 July 2006 (UTC)
I've never heard of mushrooms that must be cooked for safety, but as Anchoress implied, I'm sure any store would warn you before selling you one. Again, I've purchased and eaten my fair share of mushrooms - there are hundreds of edible varieties, and I've never seen one that needed to be cooked for it to be safe. --Bmk 03:35, 26 July 2006 (UTC)
Don't know what they're called, but there's a mushroom that looks exactly the same as enokitake. The "false enokitake" can cause diarrhea if it isn't cooked properly. --Kjoonlee 08:03, 26 July 2006 (UTC)

I think slippery jacks (mock porcinis - aka boletas) are slightly poisonous raw, and slightly less so, perhaps fully edible - though they don't taste particularly good and i did feel a bit sick after eating one - when thoroughly cooked.

Also note that many 'shrooms are grown in manure, so cooking them is a good idea (to kill any little nasties living in the manure). StuRat 03:00, 27 July 2006 (UTC)

Awesome article Mushroom picking in Slavic culture says that Boletus edulis and Russula vesca could be eaten raw. I wouldn't recommend it though :)  Grue  08:12, 29 July 2006 (UTC)

Even True morels should be cooked, otherwise they can cause stomach problems(vomiting, nausea, diahrea, cramps) . If you have eaten them raw yourself without any problems go rite ahead, but don't serve them to anyone else raw. Especially with alcohol.----Aaron