Wikipedia:Reference desk/Archives/Science/2008 August 31

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August 31

Magnetic "field lines"

Reflecting my utter confusion on some parts of physics, what are magnetic field lines? The classic grade-school experiment with iron filings on a piece of paper with a magnet below shows field lines; the aurorae are produced by "recombination of field lines in the magnetopause"; and every diagram concerning the magnetic force has those dashed lines from N to S. So is the magnetic force expressed along physically real lines through space? Why isn't the magnetic force expressed on a uniform gradient, why does it have to go through certain "lines"? Which of Maxwell's equations result in a field line where the magnetic field is especially concentrated? And how do we predict that "here be a magnetic field line"? Is this a conceptual tool or a real phenomenon? Confusedly yours, Franamax (talk) 01:04, 31 August 2008 (UTC)

Magnetic field#Visualizing the magnetic field seems to deal with the 'field line' usage. We also have an article field line. I haven't read either, so I don't know if there're any good. Algebraist 01:08, 31 August 2008 (UTC)

Conceptual tool. Magnetic field lines are contour lines that give the direction of the magnetic field at any point in space. There are an infinite number of (hypothetical) field lines.--79.76.176.172 (talk) 02:11, 31 August 2008 (UTC)

The field lines indicate the direction a tiny compass needle would point if placed at that spot. It not the case that magnetic fields are present along certain lines, with points between the lines where the magnet would have no effect on a compass needle. As for iron filings, they tend to clump together and establish a pattern of lines or curves. If the magnet were left and the filings were removed and new filings shaken over the piece of cardboard, the clumpy curves woould be similar but in slightly different places. The closeness of the spacing of the "lines" is a helpful approximation the the flux density variation. Edison2 (talk) 06:23, 31 August 2008 (UTC)

Hmmm. Why do the filings conveniently clump together into lines? Clarityfiend (talk) 06:26, 31 August 2008 (UTC)

I guess that each small splinter attains a N / S-pole. As they are linear in shape, the N-pole of one then "sticks" to the S-pole of the next one, thus forming curves / field lines. --Cookatoo.ergo.ZooM (talk) 10:03, 31 August 2008 (UTC)

The ontological status of field lines can get a little complicated. I have read discussions on this very point by physicist/historian/philosophers. Sometimes they are treated as a mathematical construction, sometimes as a real physical entity. As far as I can tell, at least by conversations with plasma physicists, it's not totally straightforward. --98.217.8.46 (talk) 17:15, 31 August 2008 (UTC)

This is the SCIENCE desk - and science is all about experiments. Here is an easy experiment: Take your fridge magnet, a sheet of paper and some iron filings. Mark the location of the magnet under the sheet of paper, sprinkle your iron filings and trace along the lines that appear with a pencil. Now remove the magnet, shake all the iron filings off of the paper and do the exact same experiment again (making sure you replace the magnet in the exact same spot. If the field lines from the second experiment consistently line up with those from the first experiment no matter how many times you try - then you have good evidence that field "lines" exist because they are a reproducible phenomenon. If they don't line up - if the lines appear in different places each time you do it - then they are a side-effect of the way iron filing rotate to align with the direction of the field and clump together to make "lines". It's my belief that the lines are not real - magnetic fields are continuous functions just like any other field. But hey...go ahead and prove me wrong! SteveBaker (talk) 19:47, 31 August 2008 (UTC)

I get confused when I read in Nature a summary of a paper in Science about "a realignment of Earth's magnetic field lines...lead to luminous polar auroras". It does go on to say the "field snaps back into place". On reflection, I can however buy into the idea that the iron filings clump due to N-S attraction between the individually ferromagnetized particles, presumably the clumping mechanism is stochastic. I'm interested though in 98.217's comment - the geo(/space?)-physicists do tend to talk explicitly about "a" field line reconnecting. Franamax (talk) 22:58, 31 August 2008 (UTC)

Right, that's the issue, I believe. Usually they are regarded as SteveBaker describes but often they are described as being able to break, reconnect, etc., which implies something a little more concrete. I seem to recall the person in question mentioning magnetic reconnection as one of the issues, but honestly, it has been awhile and this sort of intimacy with physics has never been to my taste. --98.217.8.46 (talk) 05:17, 1 September 2008 (UTC)

Where could I buy lead ball bearings?

Preferably 20mm in diameter or so. ScienceApe (talk) 02:49, 31 August 2008 (UTC)

Musket balls?--79.76.176.172 (talk) 02:57, 31 August 2008 (UTC)

Nobody is going to make 'bearings' out of lead - the point of a bearing is to remain perfectly spherical under load - and lead would deform and be an utterly useless material - it's far too soft. However, you can buy spherical BB-gun pellets in lead. As '79 says, you could look for musket balls. Quite a few antique gun enthusiasts must need large diameter lead projectiles. However, I think a lot of them make their own by pouring liquid lead into suitable molds. You could do that too. SteveBaker (talk) 03:02, 31 August 2008 (UTC)

Are you looking for ball mill grinding media? United Nuclear sells grinding media made of lead and antimony which are 12.7 mm in diameter. I'm sure other retailers sell grinding media closer to 20 mm if you search on the internet. Coolotter88 (talk) 20:01, 31 August 2008 (UTC)

Asteroids and comets

What plans are in place to deal with the asteroids and comets currently on a direct collision course with Earth?--79.76.176.172 (talk) 02:55, 31 August 2008 (UTC)

Many asteroid deflection strategies have been proposed, but there are no concrete plans in place. In most cases, the choice of approach would have a lot to with the amount of preperation time available and the size of the threatening rock. Dragons flight (talk) 03:03, 31 August 2008 (UTC)

And composition. A solid lump of rock requires a different approach to a loose pile of rubble. --Tango (talk) 03:06, 31 August 2008 (UTC)

NASA have looked at a range of possibilities - but so far, none of them have been brought to the point where we could actually deploy them. Further testing is needed because there is a severe risk of simply breaking up an asteroid into smaller chunks - which would be just as dangerous and have a larger probability of splattering something important on impact. There are also concerns that errors in calculating the precise orbit of the body might result in us inadvertently turning a one in one ten chance of a problem into a certainty. The best chance we have to do this cleanly is to detect the problematic body many years before impact. The smallest nudge at that time will avoid a problem - but if you leave it until the body is merely months away, it's vastly harder. Right now, we can't detect mountain-sized bodies until they are weeks away. Before we do anything about deflection or destruction - we first need to put serious funding into detection - and that's really not happening. The short answer is that we currently have absolutely zero protection - and at present rate of progress, we probably won't have such protection for decades into the future. SteveBaker (talk) 03:09, 31 August 2008 (UTC)

Oh shit! Well wouldn't it be a good idea if both Russia and America and anyone else were to get together to form a plan to detect and divert these objects which would probably terminate most of the life on earth rather than have petty squabbles about whose got more missiles in the others back yard?--79.76.176.172 (talk) 03:18, 31 August 2008 (UTC)

Why? That is nothing more than opinion. This is a reference desk, not a place to try and get a debate going about how important it is to drop everything and try to fix a problem that will likely never happen while humans are still alive on our tiny little speck of a planet. -- kainaw™ 03:21, 31 August 2008 (UTC)

Likely never? 99942 Apophis —Preceding unsigned comment added by 79.76.176.172 (talk) 04:38, 31 August 2008 (UTC)

Actually it was a question (as indicated by the ? at the end) not opinion, but thats a remarkably cool attitude you have there! Just how sure are you that its probably not going to happen sometime soon?--79.76.176.172 (talk) 03:36, 31 August 2008 (UTC)

See opinion and fact. Any question beginning with "Well wouldn't it be a good idea if..." is asking for opinion, not fact. This is not a discussion forum. There are thousands of discussion forums on the Internet. Use one of them if you feel such a desire to discuss opinions. -- kainaw™ 03:40, 31 August 2008 (UTC)

He did follow up with a legitimate question regarding the probability of an impact event during which humans inhabit the Earth. ScienceApe (talk) 04:38, 31 August 2008 (UTC)

What is your source for that statement that we can't detect mountain-sized objects until they are weeks away? My understanding was that our detection programs were pretty good. --Tango (talk) 03:46, 31 August 2008 (UTC)

We detect and follow a great many objects that are only tens or hundreds of meters in size [1]. Most known objects are followed many years in advance. Yes there are unknown asteroids, and yes some could be very large, but the idea that we only see mountains right before they show up is simply not true. Dragons flight (talk) 05:16, 31 August 2008 (UTC)

I think there is a big difference between detecting a NEO for the first time and tracking it once it has been detected - tracking is much easier than detection. If you look at this NASA list of recent and upcoming close approaches, you can see that some of the objects have been tracked over several years. But if you drill down to the (rather cool) Java interactive orbital simulation for each object, you can see that most of them (especially in the sub-1km diameter range) were very close to the Earth when then were first detected. 1998 UP1, for example, has been tracked for 10 years, but it makes a close approach once a year (because its orbital period is almost exactly 1 year) and when it was discovered in October 1998 it was a few days past that year's close approach. NEO tracking programs seem to concentrate on detecting objects that repeatedly cross the Earth's orbit and make close approaches every few years, so that we can track them and get an accurate enough fix on their orbits to determine whether they will be a danger in, say, 50 or 100 year's time. Gandalf61 (talk) 13:32, 31 August 2008 (UTC)

That was, as you say, detected 10 years ago. Our detection programs have come on a long way since then - I would hope we would have spotted it sooner had it made the same close approach now. Also, I wouldn't consider sub-1km to be mountain sized. --Tango (talk) 14:22, 31 August 2008 (UTC)

I don't know - a cubic kilometer of rock would look a lot like a mountain if you put it in your back yard! But let's consult (say) an encyclopedia: Mountain#Definitions says that in the US, a mountain has to be more than 610m tall and in the UK, over 914m. Something that's 1000m tall qualifies as a mountain. SteveBaker (talk) 16:09, 31 August 2008 (UTC)

Yeah, I looked at those definitions and decided 1km was a good cutoff, so sub-1km wouldn't be mountain sized. Remember, these aren't going to be nice regular shapes, so the 1km presumably refers to the longest axis, the other will probably be significantly smaller. --Tango (talk) 19:30, 31 August 2008 (UTC)

The object that caused the Tunguska event and the object that created Meteor Crater in Arizona were both about 50 m in diameter - tiddlers, but large enough to cause explosions in the 1-10 megatons range. NASA's minimum size threshold for counting an object as a potentially hazardous asteroid is 150 m diameter - see "What Is A Potentially Hazardous Asteroid (PHA)?" at this FAQ. An impact event from a sub-1 km object can still cause massive damage. Gandalf61 (talk) 17:49, 31 August 2008 (UTC)

Sure, they'll hurt, but they're not end-of-world type events. Deaths would probably be comparable to other fairly frequent natural disasters. --Tango (talk) 19:30, 31 August 2008 (UTC)

Well, the 50 meter object that caused the Tanguska event flattened 800 square miles of forest - certainly not an end-of-the-world event...for that you need something like a 1km rock. But translate Tanguska into 800 square miles of a major city - and you have perhaps a million people dead. That would make it the second or maybe third biggest natural disaster ever (after floods in China in 1931 and again in 1887). Of course the probability of such a thing is low simply because cities don't cover much area compared to the surface of the entire planet - so the probability of a direct city impact is small. But as I said before, the size of the disaster is potentially so huge that even with the relative rareity of the event - we really should be more concerned than we are. SteveBaker (talk) 15:57, 1 September 2008 (UTC)

Here is some data for the not-so-worried:

• Tunguska_event#Similar_events shows that megaton-range events happened in 1908 and 1930 and many multi-kiloton (bigger-than-Hiroshima) sized events have happened in the last 50 years or so.
• 50m rocks hit us about every thousand years and can level 800 square miles of land (such as in the Tunguska event in 1908) - an explosion with minimum 5 megatons.
• 1km rocks hit us about every half million years.
• 5km rocks hit us about every ten million years and produce a 100km crater and perhaps 50 megatons of explosive power - the debris would blot out the sun and to terrible things to our crops...billions of people could die of starvation within a year.
• The dinosaurs were likely wiped out by a 10km rock - some of humanity might survive it - but probably 99% of humans would die.

So - there is a 1 in 1000 chance per year of a random 800 square mile chunk of the planet getting wiped out with the force of a very large nuclear weapon - from a rock that's WAY smaller than we're able to detect even at the very last minute. Every decade or so we get hit with rocks that could kill a million people in the very unlikely event they might hit a city. Previous replies suggest that a 1km rock may or may not be detectable soon enough to do something - but it could take out an enormous amount of people and/or cause massive tsunamis.

Once every half million years for a really big rock may sound like a pretty remote chance - but the consequences would be extreme.

The problem with this kind of thing is to balance the probability of it happening versus the scale of the consequences. We spend an immense amount of money to protect ourselves from very probably events (car crashes, house fires, medical mishaps) that are very likely - but which don't affect many people at a time. We have a blind-spot to very infrequent/unlikely events that would take out half the planet. That's an odd thing. It really doesn't matter (on the grand scheme of things) how many people get killed in car crashes - but if a mountain of rock were to wipe out almost all of humanity - then that's something we need to pay attention to.

If there is a one in 500,000 chance of a meteor killing (say) 5 billion people each year (that's only considering the really big rocks) - that's an average of 10 out of every 100,000 people per year. OK - now let's examine: List of causes of death by rate. 20 people per 100,000 get killed in car crashes worldwide (it's more likely in places like the USA - but less likely in (say) India) - so you are twice as likely to die in a car crash than by the consequences of a 10km meteor. The probability of dying in a killer meteor collision is comparable to the chances of dying from one of the more common cancers or a random act of violence (eg a crime, a mass murderer or a domestic dispute). So, from an individual person's perspective - we should be spending at least as much on looking for and deflecting 1km meteors as we do on trying to eliminate street violence. Death by meteor is quite a bit more probable than death by Altzheimer's disease. You are maybe twice as likely to die from a meteor than from your house burning down.

From a purely statistical perspective, we should spend more on meteor protection than on (say) airbags in cars, Altzheimer's research or smoke detectors because no matter how much you spend, you'll never eliminate those things - where there is every chance that would could provide 100% protection against 1km+ meteor strikes. As a species, we should place more 'weight' on a potential species-obliterating-event than on more probable events that (while killing the same number of people on average) are no risk whatever to the survival of our species. You can go one further by saying that we'd also be protecting most other species on earth from obliteration too.

That's only considering the very infrequent planet killers - I guarantee that the first time a once-a-decade sub-50m rock hits a major city, delivering a few hundred Hiroshima-sized bombs worth of damage and perhaps killing a million people, we'll suddenly become VERY focussed on those smaller rocks.

SteveBaker (talk) 19:13, 31 August 2008 (UTC)

You need to take into account cost:benefit ratios. You can almost completely protect a family with one smoke detector for a couple of quid. The cost per family of protecting against small asteroids is probably far far greater (I don't have any figures). Remember, even if we detect them, the cost of actually doing anything about it is probably going to be prohibitive if it's "only" going to save a million people. Using Deep_Impact_(space_mission) as a benchmark (a deflection mission seems roughly similar in parameters), we're talking about $330 million, probably more due to the need to do it quickly. $330 per person sounds pretty reasonable at first glance, but when you consider what else that $330 could be spent on (smoke detectors for 100 families, say), it may not be the best use of limited funds (and funds are always limited). --Tango (talk) 19:30, 31 August 2008 (UTC)

You have the math totally wrong. You can only spread the cost of $330 million over a million people once you know which million people will be affected. Before you know which million you're going to have to save, you get to spread the cost over the entire planet. If $330 million were all it would take to protect six billion people from a one in a thousand chance of death-by-meteor per year, it would be a total bargin! You'd have to put $3 smoke detectors into a lot more than 110 million homes to save a million lives. Remember - death from house fires is 5 per 100,000 people per year. To save a million people over maybe the ten year life of your smoke detectors in a year you'd have to put them 1,000,000x100,000/(5x10) homes...that's two BILLION homes...which would cost six billion dollars - not $330 million...and (furthermore) they'd have to be 100% effective in preventing death from fires - which they obviously are not.

If you are thinking about an after-detection calculation - then look at it like this: We spent considerably more than $330 per person on fixing up New Orleans AFTER Katrina - forget the deaths - the cost of reconstruction alone would more than pay for the mission to deflect a small rock. If a big rock was to hit New York and you asked the million people within the strike zone to pay $330 each to save their homes - I'm pretty sure they (or their insurance companies) would be more than happy to pay up! $330 million is NOTHING compared to the cost of a million lives. The government could justify it in terms of lost taxation revenue alone!

Linked earlier in this discussion, The Sentry Risk Table is an interesting read. It's fascinating how many serious impact events have better odds than a lottery ticket.

For instance, you'd need to buy 3,398 powerball tickets before your odds of hitting the jackpot were higher than the odds of an impact by 99942 Apophis.APL (talk) 19:27, 31 August 2008 (UTC)

So asking people to pay $3,398 each for meteor insurance should be a no-brainer since dying is a much worse event than winning a lottery is a good event. SteveBaker (talk) 20:09, 31 August 2008 (UTC)

Yes, but not playing the lottery ought to be a no-brainer, yet people still do it. --Tango (talk) 22:36, 31 August 2008 (UTC)

Steve, I've got you covered, where should I send my PayPal account information? Special this month only, $3,000 even if you act now! I'll insure you against winning Powerball too. However I won't cover you for the much more liekly chance of getting hit by lightning or contracting the flesh-eating virus (which amazingly I'm not able to find a wikilink for). Franamax (talk) 22:44, 31 August 2008 (UTC)

The lottery is a tax on the statistically-challenged. Sadly, I can't afford meteor insurance because I'm spending all my money on other forms of insurance! SteveBaker (talk) 03:34, 1 September 2008 (UTC)

Oh - and the chance of being struck by lighting in any given year is about one in 300,000 - so that's 0.3 deaths per 100,000 - about 30 times less likely than dying from a planet-killing meteor strike.Necrotizing fasciitis is about half as likely to hit you as lightning...so about 60 times less likely than dying from a meteor strike. Hence it would cost you barely 5% more to throw in insurance for those other two conditions along with your meteor insurance. You see what I mean about people's failure to understand statistics? SteveBaker (talk) 04:27, 1 September 2008 (UTC)

Necrotizing fasciitis. --Tango (talk) 00:33, 1 September 2008 (UTC)

Yeah, that's the one. Why did I use "virus" in my search? I tells ya, we should ask Google to take over our search box! Franamax (talk) 01:52, 1 September 2008 (UTC)

Hey, at least it's not lupus. --mboverload@ 01:54, 1 September 2008 (UTC)

Poisonous things that taste good

I want to compile a list of notoriously carcinogenic/poisonous chemicals that also have a palatable flavor/scent. For example Lead(II) acetate, cyanide (I've heard it smells like bitter almonds), etc.. I would be eternally thankful if you could help me on my way, thank you. Kenjibeast (talk) 06:20, 31 August 2008 (UTC)

How about fat, alcohol (I personally don't like the taste but a lot of people seem to like it), sodium chloride, sucrose ... Nil Einne (talk) 06:57, 31 August 2008 (UTC)

What about water? 93.132.155.98 (talk) 10:14, 31 August 2008 (UTC)

Some like the smokey note which is definitely carcinogenic. --Ayacop (talk) 07:47, 31 August 2008 (UTC)

Fugu, anyone? --antilived^{T | C | G} 07:51, 31 August 2008 (UTC)

I thought about that but in that case I think it's questionable whether they really like the taste or simple the effect of the nicotine they're inhaling. I don't think the same thing can be said for alcoholic beverages because altho some people just want to get drunk, many people claim to like the taste too Nil Einne (talk) 10:59, 1 September 2008 (UTC)

Most kinds of ant poison taste good because it contains sugar to attract the ants. But most kinds also contain strychnine. (Refer to "strychnine" in Wikipedia.) Because of the sugar content, ant poison should be strictly kept away from children. Dogs like sugar too. The safest kind of ant poison comes in a little sealed can that has small holes for the ants to enter. Andme2 (talk) 15:32, 31 August 2008 (UTC)

The ability to smell hydrogen cyanide is genetic, though I assume non-detection is a side-effect of some more useful trait:) Phosgene smells nice. Lots of molecules are made of various sugars (as a class of compounds, not the specific "table sugar" and other sweeteners usually seen in foods. Some saccharaides are wickedly toxic, but don't know how they smell. Even some simple acetals smell nice but have toxic effects (first-hand experience here). DMacks (talk) 19:58, 31 August 2008 (UTC)

I'll nominate ethylene oxide which apparently has a "faintly sweet" odour which I've thankfully never detected - they have honkin' big signs around the EO facilities in refineries and gas plants. And of course, there's benzene, which gave the name to the whole class of aromatic compounds, because it smells sweet while it kills you. Franamax (talk) 22:29, 31 August 2008 (UTC)

Anecdote: I remember driving in for my safety training to a really quite large Texas refinery (Texaco Port Neches) and smelling the kinda pleasant smells wafting in from the hot Texas breeze (I'm Canadian, we don't roll our windows up on hot days). I also remember, after my safety training, sitting in the smoking area smelling those pleasant odours wafting about, and sucking on my cigarette so that its nice familiar toxic compounds could keep me safe. :( Franamax (talk) 00:01, 1 September 2008 (UTC)

Ethylene glycol - found in antifreeze - slightly sweet smell - especially if heated. Very sweet and pleasant-tasting too. Many children and pets have died from drinking small amounts of the stuff, being fooled by the pretty colors it comes in and the super-sweet taste. The merest taste of the stuff is enough to require hospitalisation for a child. Ethylene glycol poisoning has a good deal to say about this nasty stuff. SteveBaker (talk) 03:29, 1 September 2008 (UTC)

Death caps ScienceApe (talk) 21:33, 1 September 2008 (UTC)

A Latin proverb: Dosis facit venemon. "It is the dose that makes the poison." - Lambajan 16:02, 7 September 2008 (UTC)

Breakdown via anti-hydrogen

Could several anti-hydrogen atoms be used to take one proton, one by one, from a neculeus of a normal atom, stepping it through alot of different elements? Or would the normal atom usually decay into two seperate atoms if hit by a antiproton etc? —Preceding unsigned comment added by 58.108.249.161 (talk) 10:09, 31 August 2008 (UTC)

The energy released by a proton-antiproton annihilation event is on the order of 2 billion electronvolts (2 GeV). The binding energy of an atomic nucleus is – for most nuclei – somewhere around 8 million electronvolts (8 MeV) per nucleon (proton and neutron in the nucleus). See our article on Binding energy#Nuclear binding energy curve for specific numbers there. The energy available from the annihilation is more than a hundred times the energy required to blow an extra proton or neutron out of the nucleus.

To be fair, the actual efficiency of transfer of annihilation energy to the nucleus is actually nowhere near 100% efficient. The first publicly available study I found was this one (warning, 7.0 MB PDF). They found that 120 MeV (on average) is transferred to a carbon nucleus, and about 450 MeV is transferred to a uranium nucleus. (That pretty much covers the gamut of atomic weights.) In any event, those energies are quite sufficient to drive fission events, so 'stepping' through elements one by one isn't likely to occur. TenOfAllTrades(talk) 14:59, 31 August 2008 (UTC)

Also, the probability of exactly one anti-hydrogen actually hitting your one atom is essentially zero. Even if this worked - you'd have to fire a lot of anti-hydrogen at a lot of your chosen material. Then you'll have no control of how many anti-hydrogens hit each atom in your material. So even if you could somehow evade the problems that TenOfAllTrades brings up - you'd still be doomed. SteveBaker (talk) 15:14, 31 August 2008 (UTC)

Electron capture could be interesting, though I don't see how to force it on atoms not prone to it (using myons?). But this way you would have excess neutrons very soon. 93.132.155.98 (talk) 17:06, 31 August 2008 (UTC)

(You meant muons, right?) --Anon, 17:36 UTC, August 31.

Right! 93.132.155.98 (talk) 17:41, 31 August 2008 (UTC)

DNA inbreedinng

Do we have an article that explains why inbreeding/incest etc. causes DNA defects and why its eveolutionarily beneficial for genes too not 'mate' with genes that are similair to themselves?--58.108.249.161 (talk) 10:41, 31 August 2008 (UTC)

Have you looked at inbreeding? SpinningSpark 11:05, 31 August 2008 (UTC)

when to plant nectarines from saved pits

I've been eating a bunch of nectarines and peaches lately and I've saved all the pits so I can plant them (mostly nectarines, but a few peaches too). I'd just like to know when would be a good time to plant them and any tips on growing the trees. In case you're wondering, I live in Northeast Kansas.

Also, I just noticed that some of the pits are getting tiny little spots of mold and I'd like to know how to safely store the pits until they can be planted. should I discard the pits that have mold?

One more thing. We have lots of little wild plums around here (I cannot identify the specific species since I'm not a botanist :P), but I know that plums are in the same genus as peaches and nectarines (prunus) and I'd like to know if they would accidentally cross-polinate. If so, would this negatively affect the quality of the fruit?

Thanks ahead of time for your help! 63.245.152.68 (talk) 11:48, 31 August 2008 (UTC)

For growing you will have to crack the pit open as the actual seed is inside, but after that there are not really any special preparations needed, just put the seed straight into some ordinary soil and keep it damp. It will take a long time to germinate though. Also try planting several seeds to increase the chances as in nature it is very rare for all offspring to survive. Remember that if you are growing them to eat, fruit grown from a seed almost never tastes the same as the fruit the seed came from. This is because the fruit you buy in the shops is bred asexually (basically clones the plant) and may have been crossed thousands of times to get it just right, but when you grow a seed it has had its genes all mixed up in independent assortment so you could get just about anything, though most of the time they just taste really bitter. Then again you could get a better fruit than the original, it's a lottery. JessicaThunderbolt 14:47, 31 August 2008 (UTC)

I've found that too. If you have a friend with a good tree - get the pit from that, then you'll have a vastly better chance - also, you'll know that that variety of tree will grow in your local climate. SteveBaker (talk) 15:11, 31 August 2008 (UTC)

'twould seem to me that when the fruit is ripe and falls to the ground would be about right? Saintrain (talk) 23:33, 31 August 2008 (UTC)

I did notice that if you crack the pit open there's a little seed in there that actually resembles an almond (which makes sense as almonds are also in the genus prunus), but it never occurred to me to plant that. I guess it makes a lot more sense that way, though. I'm aware that the fruit probably won't meet my expectations, but I have about 15 pits so I'm bound to get some good fruit someday. About how long does it take for the seeds to germinate? and after they do, how long does it take for them to grow big enough to make fruit?

I wonder if you can eat the almond-like seeds or if they have some sort of poison in them. I'm sure not gonna try, but I am curious.63.245.152.68 (talk) 11:50, 1 September 2008 (UTC)

The peach trees I have seen grown from seed have fine tasting fruit, but the fruit is a little smaller.Polypipe Wrangler (talk) 03:36, 2 September 2008 (UTC)

got about twenty fruit after 7 years, (tree about 2 m tall) but that was with a drought and slow growing conditions.Polypipe Wrangler (talk) 03:39, 2 September 2008 (UTC)

lipid movement in a liposome..

I would like to know a few methods using which one could track the movement of a lipid in a liposome. In the sense, suppose I want to keep observing a lipid molecule for say, 5 minutes, then how do I do that? —Preceding unsigned comment added by Psruthi16 (talk • contribs) 14:29, 31 August 2008 (UTC)

An admitted wild guess here (which I'm not supposed to do), but our article on fluorescent proteins indicates that they can be palmitoylated to mGFP. Palmitoyl is a fatty acid so possibly the GFP-palmitoyl complex could be incorporated into a lipid molecule? However, getting that complex through the liposome membrane would be a different story. Other than that, I got nothin'. Franamax (talk) 22:21, 31 August 2008 (UTC)

Mozzy bites

What the best thing to rub on Mosquito bites? Does spit really help? --217.227.97.121 (talk) 14:56, 31 August 2008 (UTC)

See Treatment of mosquito bites. JessicaThunderbolt 15:02, 31 August 2008 (UTC)

I'm surprised it doesn't mention witch hazel, which works for me every time. Use two applications five minutes apart.--Shantavira|^{feed me} 15:25, 31 August 2008 (UTC)

Wikipedia - the encyclopedia you can edit! SteveBaker (talk) 16:04, 31 August 2008 (UTC)

But not WP:Original research Nil Einne (talk) 10:56, 1 September 2008 (UTC)

Unknown insect

Found a insect that was thought to be an armored snail, it has slimy feet of a snail, but the head of a catapiller, and the shell of a pill bug(rolly polly bug). Cannot find any information on this insect?216.236.163.183 (talk) 15:23, 31 August 2008 (UTC)

It seems unlikely to be an insect. Adult insects all have six legs and a three-part segmented body (head, thorax, abdomen). SteveBaker (talk) 16:00, 31 August 2008 (UTC)

This sounds like a joke question, but I'll assume good faith. You should provide the location and a photograph of the creature to help people here make an indentification. Jdrewitt (talk) 16:05, 31 August 2008 (UTC)

It could be a cherry slug or pear slug. (Why is there no article on this topic?)Graeme Bartlett (talk) 21:35, 31 August 2008 (UTC)

Cherry slug larva

Cherry/Pear slugs (they are both Caliroa cerasi) aren't slugs at all - they are Sawfly larvae from the Tenthredinidae family - we don't have articles about any of that family. The photo at right comes from Wikicommons - but it doesn't seem to be used anywhere in Wikipedia. It looks like the sawflies are a taxonomic mess - a bunch of more or less unrelated species jammed together because they share the same lifestyle - not because they are genetically related. In these cases, the names of the animals may change - but the references I can find in agricultural web sites may well be using some older name. It kinda fits the OP's description - except for the feet. SteveBaker (talk) 03:18, 1 September 2008 (UTC)

Maybe he thought that it has a snail's foot due to its slime secretion?--Lenticel ^(talk) 00:46, 2 September 2008 (UTC)

Magnetic cows

There is a story that's been all over the news media over the last few days about researchers looking at Google Maps and finding that cows (and other herd animals like deer) have a preference for aligning themselves North/South. I'm trying to find out whether they mean that the cows all face with their noses to the north - or whether 50% of them are facing north and 50% south. I've been thinking that a possible reason for doing this (None of these reports seem to be suggesting reasons) is that it might be a way for the cows to arrange for the herd to get good all-round vision for predators. They have eyes out on the sides of their heads to improve their field of view - but they must have a blind-spot behind their thick, juicy, tender rear ends. If the cows pointed in utterly random directions, they'd have pretty good 360 coverage - but if they all pointed North - that would mean that they deliberately evolved a blind spot! However, if 50% faced north and 50% south that would guarantee no blind-spots and they could be using the earth's magnetic field to dramatically reduce the probability of a blind-spot. Has anyone heard a theory for this? SteveBaker (talk) 15:55, 31 August 2008 (UTC)

Am I the only one who has an image of a cow suspended on a piece of string slowly rotating to point north? Seriously, the first thing that crosses my mind is that they are putting the sun to their backs to avoid the glare. Is there any information on cows in Australia or South America? If they face South rather than North that would indicate that it is not magnetic field related. SpinningSpark 16:22, 31 August 2008 (UTC)

Here is the study. It's not clear in the abstract, but I believe they were unable to determine from satellite images which way round cows were standing. The deer tend to be head-north though. To Spinningspark: they tested the magnetic hypothesis by looking at areas where magnetic north is significantly different from true north. It turned out magnetic north wins. Algebraist 16:34, 31 August 2008 (UTC)

...and, according to this summary in The Economist, the researchers averaged out the effects of sun and wind direction. Gandalf61 (talk) 17:13, 31 August 2008 (UTC)

(ec) This report from the BBC says that the deer (all observed in Czech Rebublic) were 2:1 in favour of North over South and as Algebraist said, the satellite images of cattle could not resolve head from rear. It does say though, that cattle in Africa and S America are more NE/SW than N/S and speculate that this is because the field is weaker in these locations. SpinningSpark 17:16, 31 August 2008 (UTC)

This sounds to me like what comes out of the back end of the cow. Cows point the way the boss cow is looking, because there might be something interesting there, and point the other way because they are a hierarchy and standing tranversely is inviting a fight. They orient to maximize warmth on cool days and into the breeze on hot days to keep the zillions of flies away from their eyes. However, if anyone has a copy of the full study, please email me, I'd love to read the whole thing. Franamax (talk) 22:05, 31 August 2008 (UTC)

I drove past a herd of Texas longhorn on the way home an hour or so ago. They were definitely all facing the same way. Now I've checked on Google Maps - I'm 100% sure they were facing nore or less exactly South. So on one entirely not-statistically-valid sample, South wins. Of course that might be because all but one of them are facing the same way as the 'boss cow' - but that doesn't help answer the question: Why does the boss cow face predominantly along the North/South axis?

Anyway - I'm bored with that one...I have a new theory. How do we feel about this one?

At the map resolution at which these photos must have been taken in order to see cows at all, we must be talking about aerial photography done from a plane. Commercially-available satellite imagery is too fuzzy to pick out anything as small as a car - let alone a cow. To get pixels that resolve as a cow - but without telling you which is head and which is tail (as the researchers claim), you must be looking at image pixels that are perhaps a quarter of a meter across. Any higher resolution and the head end would be obvious. That would give you a "cow" that's perhaps 8 fuzzy off-white pixels. If the resolution were a half meter then a cow would be only be about two or three pixels. So what these guys are undoubtedly analysing is the direction based on perhaps just a handful of pixels.

But suppose the aircraft doing the photography were flying east-west and taking a photograph on an oblique angle in order to cover a wide swath of land without having to fly backwards and forwards too many times. When Google stretch that photo to make it look like it was taken looking straight down, then a fuzzy ROUND splotch would turn into a fuzzy elliptical splotch that would be stretched along the north-south axis. So if the original resolution was not quite high enough to resolve the direction the cows were pointing then Google's image processing could easily make it look like they all face the same way...at right angles to the flight path of the aircraft. So...can anyone think why an aerial photography plane would always tend to fly East/West when doing it's photography run rather than North/South? Maybe some kind of air traffic control rules for the altitude they fly at? I know that aircraft flying in certain conditions are separated out at different altitudes depending on the direction they are flying...perhaps at the best altitude for photography, you have to be flying East or West?

SteveBaker (talk) 02:40, 1 September 2008 (UTC)

I only have one air chart (Helsinki), the Malmi and Vantaa approaches and holding zones are variously oriented. But wouldn't aerial surveys be flying in the uncontrolled zone anyway? On this chart, below 1000 feet near the airports and below 1500 feet everywhere else is fly-as-you-like. How high would a survey plane be flying? Franamax (talk) 09:43, 1 September 2008 (UTC)

Thats the same thing i thought. I haven't seen the details of the study, at first you get the impression that its very professionally done, then later you get the impression that it is rather unprofessionally done. Also it should be pretty simple to test this in practice. Get some strong electromagents and put theem around a small field and see if you can get the cow to allign itself.

155.144.40.31 (talk) 05:36, 1 September 2008 (UTC)

Or pick a cow up, move it a few thousand km east/west, put it down again and see if it turns slightly. What would happen if you put the magnet on the cow? Would it spin in circles? :) Franamax (talk) 09:32, 1 September 2008 (UTC)

We just did it to freak you humans out. Joke's over, so moooove along. Sincerely, Elsie. [unsigned]

Well, that way they're not blinded by the sun neither in the morning or the evening. – b_jonas 23:05, 6 September 2008 (UTC)

Path integral formulation

Anyone here who thinks to understand that article? It all looks like technobabble to me. The formula below the heading Time-slicing definition looks as if it's integrating over just one path, not over all possible paths. 93.132.155.98 (talk) 16:13, 31 August 2008 (UTC)

Well, it's about quantum mechanics, what kind of babble did you expect? :) And it's about an idea developed by Richard Feynman, who had an extra several brains packed in his skull. Quantum theory is one of those areas where it becomes very difficult to meet the Wikipedia standard of "anyone should be able to read and understand the article". That can be done, but you'd need a box at the top saying "read these six hundred other articles first". Franamax (talk) 21:51, 31 August 2008 (UTC)

You are right in general, this makes it so difficult to recognize technobabble. In this special case, line integral and path integral seem to be mixed up without warning. 93.132.132.172 (talk) 00:12, 1 September 2008 (UTC)

The path integral is vastly easier to understand than that article makes it look; it's a very simple idea. There's a nice explanation on pages 7–9 of Chapter I of QFT in a Nutshell. We need an introduction like that in the article. If someone will draw the pictures, I'll write the text.

The formula

$\int \limits _{x_{1}=x_{a}}^{x_{1}=x_{b}}\ldots \int \limits _{x_{n}=x_{a}}^{x_{n}=x_{b}}\ \exp \left({\frac {\rm {i}}{\hbar }}\int \limits _{t_{a}}^{t_{b}}{\mathcal {L}}(x(t),v(t),t)\,\mathrm {d} t\right)\,\mathrm {d} x_{1}\cdots \mathrm {d} x_{n}$

in the "time-slicing definition" section is integrating over all paths. A particular tuple of values $(x_{1},\ldots ,x_{n})$ represents a path in which the particle is at position $x_{i}$ at time $t_{i}$, where $t_{1},\ldots ,t_{n}$ are times between $t_{a}$ and $t_{b}$. I don't know how they're choosing the n times or interpolating the position at intermediate times, but it doesn't matter because they're taking the $n\rightarrow \infty$ limit (compare the definition of the Riemann integral).

There isn't anything specifically quantum mechanical about the path integral. It works with any linear wave equation. Schrödinger's equation is linear, as are Maxwell's equations in vacuum. Maybe the article should introduce the path integral using water waves instead of quantum mechanics. -- BenRG (talk) 01:43, 1 September 2008 (UTC)

Leaving the physics aside, I note that the integration variables $(x_{1},\ldots ,x_{n})$ are not part of the integrand. It is all but clear what the $\,x(t)$ has to do with the $\,x_{i}$. If the $\,x(t)$ denoted one ot the $\,x_{i}$ it would be gone after integrating with it and of no use for the others. 93.132.132.172 (talk) 19:02, 1 September 2008 (UTC)

blood

what is the non-living part of blood? —Preceding unsigned comment added by 124.195.198.213 (talk) 16:39, 31 August 2008 (UTC)

Blood plasma. And I'm not sure if red blood cells are considered 'living' as they don't contain DNA. 93.132.155.98 (talk) 16:47, 31 August 2008 (UTC)

RBCs are certainly usually considered living. They have an active metabolism, and die in about 90 days. The definition of living doesn't usually include any criterion that DNA is present. Such a definition would classify some viruses as living and some as non-living on the basis of chemical constitutents rather than activity. - Nunh-huh 16:36, 1 September 2008 (UTC)

I was to say that it didn't contain DNA (as usual in other human cells, and no RNA either, nor any other substance or information) to guide reproduction. (As a thought experiment, I consider candle flames alive and worker bees as dead. I don't really believe in that, but I can't pinpoint what would be wrong with that.) 93.132.132.172 (talk) 20:52, 1 September 2008 (UTC)

Perhaps it would be best to keep such definitions of "living" very quiet...they're probably not helpful here, or if, say, you were to get a job as a coroner. Other than that, no harm no foul. - Nunh-huh 03:02, 2 September 2008 (UTC)

The main objective of wikipedia is to give information to people, but what would that be to a people that doesn't also think? Making people think (for themselves, if ever possible) is a goal that I pursue and hope not to be in conflict with wikepedia goals. 93.132.180.102 (talk) 21:47, 2 September 2008 (UTC)

There are productive ways to think, and non-productive. VItalistic speculation is one of the latter. As are categorizations that are made up rather than essential.- Nunh-huh 00:00, 6 September 2008 (UTC)

Life in the most polluted environments?

Which land weeds or sea creatures are able to survive in the most polluted of environments?--Sonjaaa (talk) 19:13, 31 August 2008 (UTC)

Pollution kills off lichens and bryophytes leaving algae. I can't help you with the toughest flowering plant. However there are different plants that can tolerate differing kinds of pollution. Some can tolerate high copper, others high phosphate, and yet others high acid. Is your pollution smoke, fluoride, acid rain, contaminated water or what? Graeme Bartlett (talk) 21:42, 31 August 2008 (UTC)

Does radiation count as pollution by what you're asking about? Becuase, if so, I would say Chernobyl would be a good place to start, because some stuff does grow there, I think, and the article should have information on the aftereffects. I can't imagine that any other kind of pollution would be as toxic as what happened there, though I could just be basing on what I've heard about it.209.244.30.221 (talk) 14:24, 1 September 2008 (UTC)

Forget the plants at Chernobyl. If you want real radiation resistance, you need Conan the Bacterium: Deinococcus radiodurans. In addition to tolerating huge amounts of ionizing radiation (surviving hundreds of times a dose lethal to humans), this bacterium tolerates dehydration, cold, acids, and vacuum. Genetically engineered versions of D. radiodurans have been developed for bioremediation of toluene and mercury contamination in radioactive waste.

As Graeme notes, however, the answer comes down to what you define as 'pollution'. In the deep ocean, hydrothermal vents spew superheated water laden with hydrogen sulfide—a deadly toxin to most creatures. Whole ecosystems are based on bateria with a taste for this usually-toxic gas. TenOfAllTrades(talk) 17:45, 1 September 2008 (UTC)

Physics Degree

I just met this grad student studying Physics and was wondering what exactly people with advanced degrees in Physics do, job-wise, after they graduate. Do they mostly become scientists? Professors? Or what? 128.239.177.28 (talk) 20:23, 31 August 2008 (UTC)Curious

Apart from your suggestions, I know planetarium operator, semiconductor factory developer, microwave nonlinear materials developer, geophysicist working for mining or oil companies, science teacher. Graeme Bartlett (talk) 21:47, 31 August 2008 (UTC)

From what I've heard, lots of graduates go into computing. —Cyclonenim (talk · contribs · email) 22:29, 31 August 2008 (UTC)

There's actually quite a lot of them on Wall Street as well. Mathematical abilities + major smarts = ideal candidate for a lot of big business. --98.217.8.46 (talk) 22:40, 31 August 2008 (UTC)

The American Institute of Physics keeps track of this sort of thing. Just skimming over a report from a year ago (report here), 43% of people with MSc in Physics end up in the Private Sector, 21% end up at a university, 13% end up working for the government, 12% teach in high school, 8% go into the military, 3% do something else. The report omits this sort of discussion for PhDs but indicates that most of them aim for employment at universities, but only about 25% end up with jobs relating to directly to physics. Most end up doing engineering jobs of some sort. (p. 16 of the report)--98.217.8.46 (talk) 22:52, 31 August 2008 (UTC)

Red jelly growing in fridge

I have something unpleasant growing in my fridge. It is the colour and consistency of raspberry jam. It does not grow in the fridge compartment itself, but inside the small bore synthetic rubber tube that drains the condenstion from the fridge. Every few months the drain becomes blocked and the bottom shelf of the fridge gets wet which is how I know it is time to clean it out again. I have flushed the drain tube countless times, often with neat disinfectant but this alien substance always grows back after a few months. But strangely, it never seems to go anywhere outside the dark inside of the pipe. What is it? Is it dangerous? As it is only ever in the pipe and I don't seem able to kill it, I am wondering if it is a chemical reaction of the synthetic rubber rather than something biological. SpinningSpark 20:37, 31 August 2008 (UTC)

Have you tried freezing it with a fire extinguisher and dropping it into the Arctic? --98.217.8.46 (talk) 23:00, 31 August 2008 (UTC)

I am told Steve McQueen is no longer available for that kind of work. SpinningSpark 23:20, 31 August 2008 (UTC)

Maybe, but I know for a fact that Kurt Russell died on just such a selfless mission. Franamax (talk) 01:41, 1 September 2008 (UTC)

This sounds to me like a slime mould (breaking the rules by guessing, again!). The rubber tube would provide a semi-porous substrate where the organisms could hide from your cleaning attempts. Also I think slime molds can form a biofilm which is resistant to disinfectants, although our articles seem to contradict me on this. The solution seems to be to buy yourself a new tube, or perhaps soak it in an acid or alkali solution for several days? I doubt it is a chemical reaction with the tube since presumably the tube would be gradually consumed in the reaction - unless the sulphur is acting as a catalyst, which I don't think would be the case. (On the subject of slime moulds, check out Dictyo for a really fascinating example of unicellular organisms turning into an animal when necessary - very Wikipedish!) Franamax (talk) 23:26, 31 August 2008 (UTC)

My red jelly has never done anything like that. But by the way, I once saw a documentary about Dictyo or a similar creature which was attacked by an amoeba-like predator which could infiltrate and take over the Dictyo body while it was on the move. You don't know the name of that creature do you? SpinningSpark 00:13, 1 September 2008 (UTC)

Well, Dictyo is an amoeba, so I'd like to see which bigger, tougher amoeba comes along to rough it up. You'd need to create a nutrient-deprived environment to see your mould rise up and fly away in any case, quit paying so much attention to keeping the stuff in your fridge cold. As far as takeovers go, I'm minded of the Wollbachia bacteria, which most unbelievably is a redlink. This is a virtuoso - it invades neurons and gonads, alters reproductive sex-ratios, forces bugs to climb up plants where they can be eaten, the whole nine yards. Please tell me we're not missing an article on Wollbachia!! Franamax (talk) 01:41, 1 September 2008 (UTC)

Yeah - we're missing that one - but you could try Wolbachia instead! :-P SteveBaker (talk) 02:03, 1 September 2008 (UTC)

As I understood it, the predator was another species of Dictyo which did not form moving "slugs" of its own. It hitched a ride on another moving Dictyo until it got somewhere good, then killed it from the inside and used the victims body to produce its own spores. There was a fascinating sequence of a Dictyo colony happily crawling along then suddenly stopping dead in its tracks and starting to grow spores from the invader. SpinningSpark 08:29, 1 September 2008 (UTC)

What type of disinfectant are you using? Perhaps a bleach solution would work well. Flush the tube with a solution made from 1 part household bleach and 9 parts water. (Using neat bleach is much more likely to damage surfaces, and probably wouldn't be any more effective.) For full effectiveness, plug the bottom of the tube and let the solution stand for at least ten minutes. Afterwards, rinse the tube out with clean water (residual bleach may harm the material). For bonus points, flush the line with 70% ethanol (or 70% isopropyl alcohol/rubbing alcohol, if it's easier to obtain) and let air dry. Since it's possible – indeed, likely – that spores or bacterial colonies remain elsewhere on the lower shelves and trays of your refrigerator, you might also want to start the process by wiping down all the exposed surfaces with a 1 in 100 bleach dilution. Don't forget to wear gloves and work in a well-ventilated area, and remember that the bleach solutions may damage or discolour both your clothing and other stuff in the kitchen. TenOfAllTrades(talk) 17:58, 1 September 2008 (UTC)

Why do we find some animals attractive?

Why do humans(at least some humans) think that animals like big cats, wolves, birds, and even certain reptiles, as well as some invertebrates such as insects, are beautiful? Because some of these creatures might be dangerous, standing around gazing at, say, a tiger could be quite an evolutionary disadvantage. 68.123.238.140 (talk) 21:51, 31 August 2008 (UTC)

Just to be sure, are you really asking: "Why do humans(at least some humans) think that animals like big cats, wolves, birds, and even certain reptiles, as well as some invertebrates such as insects, are beautiful?" --hydnjo talk 22:37, 31 August 2008 (UTC)

Are you refering to sexual attraction or "awwww they're soooo cute" beautiful? --mboverload@ 22:39, 31 August 2008 (UTC)

Not quite either of those, actually, but closer to the "cute" interpretation-- why people like to look at these animals, that's what I was getting at. 68.123.238.140 (talk) 23:02, 1 September 2008 (UTC)

The last time a similar question came up here, someone suggested that our concept of 'cuteness' is an inbuilt safety mechanism to prevent us from eating our own offspring. --Kurt Shaped Box (talk) 00:11, 2 September 2008 (UTC)

Bilateral symmetry, anthropomorphic features (like the big eyes of a seal pup or panda bear), flowing "elegant" features would be some of the factors. Also, many sexual adaptations such as the "eyes" on a peacock's tail feathers and the brilliant colouration of male birds would weigh in. Of course, the concept of beauty is like your gas mileage - it varies. I personally find a preying mantis quite beautiful, but others might freak out. Then there's spiders - both beautiful and repellent. Franamax (talk) 23:34, 31 August 2008 (UTC)

The article on furries may be of interest to you. JessicaThunderbolt 12:28, 1 September 2008 (UTC)

At the risk of sounding unscientific, anything that looks beautiful to you follows the Golden ratio at some level or the other. Look at its relation to beauty on goldennumber.net. Sandman30s (talk) 14:58, 1 September 2008 (UTC)

Yeah also could it be said to be a sort of sexual feeling towards said animals esp when you pet them?? —Preceding unsigned comment added by LCMk2 (talk • contribs) 21:16, 1 September 2008 (UTC)

Are you confusing petting and heavy petting? --Kurt Shaped Box (talk) 00:14, 2 September 2008 (UTC)

LOL the only other place I've seen "heavy petting" used was in Ann Landers columns! :) (Well, that and other times - but I generally had my eyes closed or was way too close to actually see it.) Franamax (talk) 00:18, 2 September 2008 (UTC)

There used to be a sign at my local swimming pool that had 'no heavy petting' listed amongst the obvious 'no smoking/no running/no food in the pool/no diving in the shallow end/no bombing/no balls or novelty inflatables' instructions. --Kurt Shaped Box (talk) 00:31, 2 September 2008 (UTC)

Basically, dogs that are kept as pets evolve and are bred to look cute for humans, because that's how the dogs can make people give them free food and that's how pet shops can get the most money from selling you dogs even though it's likely that the buyer would have the same gain by just taking any stray dog from the street (if you pay for vaccination). – b_jonas 23:00, 6 September 2008 (UTC)

Human lungs

Can human lungs grow in response to intense use, like human muscles can? I mean, can they function better because one does a lot of physical exercise? Divers can learn to hold their breath for minutes, what happens to their lungs? Can the VO2 max of adult lungs increase? I realize that the question isn't worded accurately, but I hope I'm clear enough to get an answer. —Preceding unsigned comment added by 24.7.54.224 (talk) 22:20, 31 August 2008 (UTC)

Yes, humans can train themselves to more efficiently take oxygen out of the air. I think Lance Armstrong has some kind of deformity that causes him to get more oxygen, but I could be wrong. --mboverload@ 22:41, 31 August 2008 (UTC)

People who live very high in the mountains develop lungs that are a bit larger than normal. Andme2 (talk) 23:07, 31 August 2008 (UTC)

Also, people that dwell in high elevations produce more red blood cells in order to transport more oxygen. I realize this borders on irrelevant.CalamusFortis 23:45, 31 August 2008 (UTC)

Actually, I think the cell-count adaptation is the primary response. It's awfully hard to increase lung volume, what with the ribs and all. Franamax (talk) 01:28, 1 September 2008 (UTC)

In addition, bigger lungs won't help, if the alveolar surface area is not increased. Oxygenation is primarily a problem of gas-exchange across membranes (and the carrying capacity of blood that has already been mentioned), not ventilation (movement of gas in and out of the alveoli). Scray (talk) 03:20, 1 September 2008 (UTC)

Maybe we can't "improve" the lungs but we can do improve the diaphragm to improve the lung's performance.--Lenticel ^(talk) 00:54, 2 September 2008 (UTC)

Sweet smell from blown up capacitors?

I've blown up various capacitors through various mishaps and I've noticed one thing: the electrolytic ones pop like pop corn and gives out a fairly sweet smell. Does anyone know what compound causes that smell? --antilived^{T | C | G} 23:12, 31 August 2008 (UTC)

Are they on a circuit board? If so, it could be vapourized phenolic resin, which smells sweet but is not a good thing to smell a lot of. Franamax (talk) 23:37, 31 August 2008 (UTC)

Yuck, that just led me through a series of stubby, badly written and unreferenced articles. C'mon science people, lets whip these things into shape! It's too much fun hanging out at the RefDesks... Franamax (talk) 23:42, 31 August 2008 (UTC)

No the smell is still there if you pop a capacitor by itself, and is characteristic of electrolytic ones, so I'm guessing something in the electrolyte? --antilived^{T | C | G} 00:23, 1 September 2008 (UTC)

Ethelyne Glycol is often used in the electrolyte, if I remember correctly. That would definitely give off a certain sweetish smell. Arakunem^Talk 00:27, 1 September 2008 (UTC)

I'm betting on Glycol too - that's the same stuff that's in antifreeze - it smells very sweet if your radiator hose splits and splashes coolant all over your engine. It's also pretty toxic...so you might want to try to avoid it where possible. SteveBaker (talk) 01:59, 1 September 2008 (UTC)

What is the designation/manufacturer/part number on the specific capacitor you blew up? Many things have a safety data sheet - maybe we can trace it that way. Franamax (talk) 01:25, 1 September 2008 (UTC)

Do you know the smell of Askarel (PCB)? I wouldn't call it sweet, but more like a dry-cleaning solvent. Old power correction capacitors and motor starting capacitors contained it. Considered hazardous.Edison2 (talk) 15:04, 1 September 2008 (UTC)

I doubt it's PCB, since the capacitors are quite new. I don't remember the manufacturer of the capacitor but it's just one of the generic 47µF ones lying around, and a few more of various capacities. I guess it's glycol, unless there's a better guess somewhere. --antilived^{T | C | G} 05:11, 2 September 2008 (UTC)

Hydrogen Peroxide and Bacteria

What is the precise chemical reaction that occurs between hydrogen peroxide and bacteria that makes it so effective for killing them?CalamusFortis 23:45, 31 August 2008 (UTC)

Hydrogen peroxide is a reactive oxygen species, which means it is willing to hand off an oxygen atom anywhere it has an excuse. Basically then, any oxidizing reaction will do. Franamax (talk) 23:46, 31 August 2008 (UTC)

That I understand, but what exactly is it oxidizing? The cell walls of the bacteria? Proteins?CalamusFortis 23:48, 31 August 2008 (UTC)

Initially, the cell walls. Oxidation ot the lipid membrane will affect the hydrophilic/hydrophobic balance that preserves the membrane structure and the cell will undergo lysis and spill out its contents. These will also be inactivated in the presence of such a strong oxidizing substance. Franamax (talk) 01:18, 1 September 2008 (UTC)

Not only the cell walls. The article on ROS states, 1. damage of DNA; 2. oxidations of polydesaturated fatty acids in lipids; 3. oxidations of amino acids in proteins; 4. Oxidatively inactivate specific enzymes by oxidation of co-factors. --Ayacop (talk) 10:15, 1 September 2008 (UTC)

Oh, OK. That was the specific answer I wanted.CalamusFortis 22:23, 1 September 2008 (UTC)

You may also want to know that hydrogen peroxide is used by white blood cells to kill bacteria in several ways. H₂O₂ is deposited near bacteria within the leukocyte's phagocytic vacuoles where it reacts with the myeloperoxidase-H₂O₂-halide system to form hyperchlorous acid and/or singlet oxygen; H₂O₂ also reacts with oxygen or with lactoferrin or bacterial iron to form a hydroxyl radical (¹OH), the end products having a direct toxic effect on the bacteria. - Nunh-huh 03:31, 2 September 2008 (UTC)

The Big Bang and Gravity

I know that this sounds like a dumb question, but could anyone tell me how planets, stars, etc. coalesced after the Big Bang? The universe is still expanding, and, in an explosion, matter does not coalesce; it keeps going outward. Hopefully there is a simple answer, and I thank you in advance for your patience. --Freiberg, Let's talk!, contribs 23:38, 31 August 2008 (UTC)

I think it helps if you don't think of the Big Bang as an explosion per se, just the start of our universe. After matter formed, areas where there was more of it simply pulled themselves together. Paragon¹²³²¹ 23:42, 31 August 2008 (UTC)

Hmm. OK, but wouldn´t that expansion of the universe itself cancel that out? Gravity, after all, is by far the weakest force. I could see individual atom forming through the strong and weak forces, but past that, it does not seem to make sense. --Freiberg, Let's talk!, contribs 23:53, 31 August 2008 (UTC)

Gravity is weak, but over short enough distances, it's stronger than expansion. The rate of expansion is, roughly speaking, given by Hubble's Constant, which is about 70km/s/Megaparsec, that is two objects a megaparsec apart will move apart at 70km/s. Our galaxy is only 30 kiloparsecs in diameter, so the recession is far less, it's not that difficult for gravity to accelerate objects towards each other fast enough to overcome that recession. --Tango (talk) 00:20, 1 September 2008 (UTC)

I think I get it now. So the inevitable variations in the initial Big Bang would be enough for various clumps of atoms to form. These clumps are now galaxies, with clumps within that becoming stars, etc. Alright! Thank you for your time.--Freiberg, Let's talk!, contribs 01:32, 1 September 2008 (UTC)

What's really interesting (and bothers me a lot) is that if the universe started out as a zero sized singularity - then it was in all possible ways perfectly symmetrical...as only an infinitely small dot can be. So how did these initial clumps come about? Any distribution of forces, energy, velocity, matter or anything else you could imagine being able to measure should also have been perfectly symmetrical and perfectly smooth. Why did any clumpiness of any kind ever come about if every particle is being pulled in all directions identically? I'm guessing that the answer is of a quantum-mechanical/statistical nature...but it still bothers me that we just naturally assume that there would be even the slightest variation in density that would ultimately lead to bigger and bigger clumps - then stars and galaxies - when the source of all of this stuff was a 100% PERFECTLY symmetrical event - by definition. SteveBaker (talk) 03:53, 1 September 2008 (UTC)

It's not an assumption; it's an observation. WMAP shows that the early universe had variations in density that exactly match the expectations based on quantum mechanical fluctuations in the first microsecond of the big bang. Dragons flight (talk) 04:47, 1 September 2008 (UTC)

Ah - that's good. That was the only thing I could think of that it might be. I was aware that WMAP had shown variation that was sufficient to explain subsequent star/galaxy formation - I wasn't aware that it matched a quantum-statistical model. Well, that's very comforting. Living in a universe where everything was exactly the same shade of beige in every direction would have been less interesting! SteveBaker (talk) 05:56, 1 September 2008 (UTC)

Our article on structure formation has a nice explanation of the end-of-end process. There are several stages. In outline:

1. Cosmic inflation provides an almost-homogenous distribution of matter/energy in the early universe, with small inhomogeneities due to inflated quantum fluctuations.
2. As the universe expands and cools it becomes dominated by matter - mostly dark matter - and gravitational attraction magnifies the inhomogeneities forming dark matter haloes.
3. Radiative cooling and magnetohydrodynamic effects then accelerated the concentration process for ordinary baryonic matter, which forms gas clouds and eventually stars and planets. Gandalf61 (talk) 09:04, 1 September 2008 (UTC)