Wikipedia:Reference desk/Science

Welcome to the science section
of the Wikipedia reference desk.

skip to bottom

Select a section:

• Computing
• Entertainment
• Humanities
• Language
• Mathematics
• Science
• Miscellaneous
• Archives

Want a faster answer?

Main page: Help searching Wikipedia

   

How can I get my question answered?

• Select the section of the desk that best fits the general topic of your question (see the navigation column to the right).
• Post your question to only one section, providing a short header that gives the topic of your question.
• Type '~~~~' (that is, four tilde characters) at the end – this signs and dates your contribution so we know who wrote what and when.
• Don't post personal contact information – it will be removed. Any answers will be provided here.
• Please be as specific as possible, and include all relevant context – the usefulness of answers may depend on the context.
• Note:
  • We don't answer (and may remove) questions that require medical diagnosis or legal advice.
  • We don't answer requests for opinions, predictions or debate.
  • We don't do your homework for you, though we'll help you past the stuck point.
  • We don't conduct original research or provide a free source of ideas, but we'll help you find information you need.

Ready? Ask a new question!

How do I answer a question?

Main page: Wikipedia:Reference desk/Guidelines

• The best answers address the question directly, and back up facts with wikilinks and links to sources. Do not edit others' comments and do not give any medical or legal advice.

See also:

• Teahouse
• Help desk
• Village pump
• Help manual

September 12

dead cockroaches

I live in the cochella valley in California. We have many cockroaches (they are called palm beetles, but a cockroach by any name smells the same). I have noted what seems to me a very peculiar chracteristic: We find many dead ones in our garages and sidewalks and around the periphery of buildings. They are always on their back. I have not been able to see one in the throws od death so I'm not sure how or why they get on their backs. Does any one know or have a theory. Please, serious answers only. Thanks, wsc —Preceding unsigned comment added by 98.149.228.69 (talk) 00:09, 12 September 2009 (UTC)

It looks like no-one really knows... And, by the way, "palm beetle" is not the right name for a cockroach. Cockroaches are not beetles, they are more closely related to praying mantises and termites than to beetles. --Dr Dima (talk) 00:35, 12 September 2009 (UTC)

According to our article a palmetto bug is another name for an American cockroach -- that's probably the source of the confusion. Looie496 (talk) 01:19, 12 September 2009 (UTC)

Not being "right" does not mean it isn't in widespread usage. King Cnut had a better chance of turning back the tides than one has of changing an "incorrect usage" of a term like this. Consider the confused state of a word like berry, for example. Its so bad that MOST of the most commonly eaten fruits called "berries" are not really "berries" (botanically speaking) and yet no one is changing their name. SO we are probably stuck with names like "palm beetle" and "palmetto bug" even though cockroaches are neither beetles or true bugs. --Jayron32 04:10, 12 September 2009 (UTC)

Likewise with the woodlouse (a crustacean). Also, in England it seems quite common for people to refer to a single woodlouse as 'a woodlice'. --Kurt Shaped Box (talk) 07:19, 12 September 2009 (UTC)

... surely not educated people in England? Dbfirs 16:07, 12 September 2009 (UTC)

Yeah, srsly. It's very common, in my experience. It's a bit like the 'roll one dice' thing. --Kurt Shaped Box (talk) 21:00, 12 September 2009 (UTC)

From chance dialectal researches, I would have thought that everyone in England referred to them as cheeselips or cheeselouses or sow bugs or slaters or any of several other local names. Those curiously attractive little critters must have more common names than almost any other beastie. Deor (talk) 22:10, 12 September 2009 (UTC)

The only other name I've ever personally heard anyone say is 'pillbug'. Now, I'd only refer to the ones that roll up into a ball as 'pillbugs' - but if this one person is anything to go by, my way is not universal. The fact that we have so many different names for these little grey skittery things, to me suggests a close historical relationship between us and them... --Kurt Shaped Box (talk) 22:23, 12 September 2009 (UTC)

Two more local names: "piggies" (no idea why), and "thus lice" (th unvoiced - presumably originally Thor's lice because they look like giant lice). Even Maths text books have started using "one dice"! Dbfirs 22:32, 12 September 2009 (UTC)

I call them waterbugs. Palmetto bug is understood. Sagittarian Milky Way (talk) 13:34, 14 September 2009 (UTC)

Perhaps being on their back (maybe after an encounter with another bug, or falling from a wall) is the cause of death, because they find they are too weak to right themselves.--Shantavira|^{feed me} 07:54, 12 September 2009 (UTC)

They can right themselves, with difficulty. It might take 1-2 minutes. I've seen one die. It's so weak it couldn't possibly right itself. Maybe they all die that way, but that still wouldn't explain why it'd get upside down in the first place. Or maybe that one was sick, it defecated a black fluid (yuck!) They like basements. Sagittarian Milky Way (talk) 13:34, 14 September 2009 (UTC)

Respiration

I want to know the exact role of oxygen in respiration, otherthan oxidation of hydrogen? —Preceding unsigned comment added by Anurocks0605 (talk • contribs) 00:30, 12 September 2009 (UTC)

Cellular respiration is a very good article with ample information. Intelligentsium 00:54, 12 September 2009 (UTC)

Environmental impact assessment

My wife and I are thinking of having kids, but we think it would be prudent to have an environmental impact assessment done first. Whom should we consult? 99.225.250.31 (talk) 03:54, 12 September 2009 (UTC)

Environmental impact of what? Having a child?!? --Jayron32 04:04, 12 September 2009 (UTC)

Not the process of having one, but the existence of one. 99.225.250.31 (talk) 04:12, 12 September 2009 (UTC)

I would imagine that would be extremely hard to do, bordering on nearly impossible. There are an absurd amount of factors, namely how you raise your child (to be the type of person who drives a Hummer or a bicycle, for example), how long they live, and what they do with their life. You could look up average impacts for people living in your area, although I'd suggest trying to raise the child to simply be what you and your wife consider to be best. You can also only have the one child, thereby reducing the population of the world (once you die); even better, you two can adopt! ~ Amory (user • talk • contribs) 04:21, 12 September 2009 (UTC)

Interesting point. Adoption would seem to be essentially impact-neutral, as the child already exists and adoption in general isn't driven by supply & demand theory. You may be increasing the average costs & impact of that child by bringing it into a wealthier situation, but compared to creating one from scratch you're orders of magnitude ahead!

Think globally. Adopt locally?213.146.164.142 (talk) 07:38, 12 September 2009 (UTC)

As all man made detrimental effects on the environment are made by humans it would be logical not only not to have children yourself but also to discourage everyone else of having children. I know this is highly cynical but that's not my fault. I think the sheer question as such is deeply flawed but in a way where the flaw can't be easily pointed out. And I think modern society needs to think about this type of questions. As of whom you should consult, this depends on what kind of answer you want. 95.112.165.86 (talk) 08:39, 12 September 2009 (UTC)

And following that concept to its logical extreme ... Mitch Ames (talk) 12:46, 12 September 2009 (UTC)

The problem with this is that your culture, which allows women freedom and reproductive choice, will be replaced by one that does not and turns women into breeding machines. If you take this "atruistic" approach, the problem will be even worse long term.80.0.102.60 (talk) 12:50, 12 September 2009 (UTC)

I have a hunch the OP's question vaguely ties to this one from the same IP some weeks ago: [1] There's no question that there have been way too many unwanted children brought into the world. But that is presumably not the likelihood with the questioner. As noted by others above, humans in general have an impact on the environment - as does all life. It's a current human conceit that we somehow have a huge impact on the environment. I recall when Mt. St. Helens erupted, it was said that the amount of particle matter in that one relatively small eruption was more than all the fallout that all the bombs in the world could produce, or some such. Don't concern yourself with "environmental impact". Decide whether you want a child, and why; and determine whether you can afford it financially, i.e. to keep it from falling into the trap suggested by the question from some weeks ago. Those should be your main concerns. Don't worry about overpopulation. Mother Nature has a way of taking care of that over time. Baseball Bugs ^{What's up, Doc?} carrots 16:47, 12 September 2009 (UTC)

Well yes, there have been "natural" events that have caused more destruction than humans on the ecology of the planet. That doesn't mean that humans causing massive ecological destruction is inconsequential. The environmental impact of humans does have a very real effect on the quality of life of humans. For example over-population puts a strain on the resources available per person.

That's not to say that the OP shouldn't have a child. As other people have said, it's extremely hard to gauge the likely impact of an individual. Some people have positive net effects on the environment, and it seems like someone raised by the OP is likely to be more environmentally conscious than average. Rckrone (talk) 17:18, 12 September 2009 (UTC)

That would be the best approach to take. Succumbing to fears about impacting the environment is self-defeating. Every living thing impacts the environment. Raising children to contribute positively would seem to be the optimal choice. Baseball Bugs ^{What's up, Doc?} carrots 17:28, 12 September 2009 (UTC)

A study has been done on this.[2] One new person could result in "up to 10,000 tonnes of CO2." --S.dedalus (talk) 20:55, 12 September 2009 (UTC)

Every human being has a huge impact on the environment. So the logical outcome of an environmental assessment would be that we should all kill ourselves at once, leaving just enough people to shut down the nuclear plants. Unt of course, ve vould need schientists to schtudy zee impact! Rather than worry about the environmental impact of your child, why not worry first about minimizing your own environmental impact? Then participate in the efforts of human society to reduce our burden on the Earth as a whole? After that, you can reproduce to your approximate population replacement value (2.1 children or so, though I've never seen a .1 baby yet) and you can raise your children to the values of conservation and respect for the natural world that you've already incorporated into your own core value system. Franamax (talk) 03:44, 13 September 2009 (UTC)

Let me know if you decide not to have kids. That will live space in the world for me to have one more of my own... Dauto (talk) 07:09, 13 September 2009 (UTC)

You are currently limiting the number of kids you have to leave room for others? Thanks for that! Please feel free to apply for your Darwin award! SteveBaker (talk) 18:01, 13 September 2009 (UTC)

One approach would be to take the List of countries by carbon dioxide emissions per capita and look up the country you live in (let's suppose that you live in the USA - so 20,000 kg per year) - and the life expectancy in List of countries by life expectancy - (for the USA, that's 76 years for a boy, 81 for a girl) and multiply the to together: 1500 tonnes for a boy, 1600 tonnes for a girl. Of course this assumes that the present rate of CO2 generation is constant for the life of the child (unlikely) and that all of the causes of CO2 emission is proportional to the size of the population (fairly likely on the scale of the US population). But this is an easy calculation - and likely to be as accurate as it is possible to be without the use of a functioning (hopefully, wind-powered) time-machine.

However, that calculation also assumes that you raise your child in an "average" way. Alternatively, you could drum into your child the need to be super-careful about not producing unnecessary carbon dioxide - perhaps encourage him/her to become a vocal advocate to CO2 reductions - for bedtime reading, read the speeches of all of the great orators. Later, support his/her candidacy for government - lead a political action committee to raise campaign funds - push his/her rise to power as the next leader of your country - resulting in a radical shift in public CO2 policies 30 years from now. This could cause massive future decrease in emissions across the entire country as a direct result of your child being born. Carried out successfully, even a 1% savings in CO2 emissions in the US would result in a massively negative carbon footprint direct resulting from your actions.

...yeah...good luck with that!

But seen in that light - it's really impossible to predict the carbon footprint of your kid.

SteveBaker (talk) 18:01, 13 September 2009 (UTC)

the organic chemistry of carbon dioxide fixation (i.e. mechanism of RuBisCO)

Yet another carbonyl question. Does the RuBisCo enzyme use the idea of nucleophilic attack on the central carbon of carbon dioxide? I tried looking at some articles but they use really elaborate physical chemistry, wavefunctions and ... no electron arrow mechanisms. Yes, I realise electron arrow mechanisms are sort of simplified but can I please see one? (Mechanisms for simpler evolutionary predecessors to RuBisCO are also welcome). John Riemann Soong (talk) 07:04, 12 September 2009 (UTC)

It depends on which part of the mechanism you are looking for, the enzyme action or the overall reaction between the CO2 and the ribulose biphosphate. Probably the RuBisCO operates on the "Lock and Key" model; that is there are binding sites for both the CO2 and the ribulose biphosphate which are brought together to form the 3-carbon sugars which enter the Krebs cycle. Our article on RuBisCO does not detail where on the molecule those binding cites are, but given that the molecular weight of RuBisCO is about 540,000, such detail is most likely out of the scope of a Wikipedia article. The exact way the electrons are "pushed" to bring about the 3-carbon sugars is also not detailed in our article, but the six-carbon intermediate is apparently 3-keto-2-carboxyarabinitol 1,5-bisphosphate, which means that if you can work out the structre of THAT; you can work out the electron pushing diagram since you have two relatively simple reactants (the ribulose biphosphate and the CO2) and a relatively simple product. --Jayron32 12:01, 12 September 2009 (UTC)

Is this it [3] ? (full scheme)

Could someone from a free country please check the link? I could get in really big trouble if some jester set up a link to something that is illegal to view even by accident in our country. Tanks. 95.112.165.86 (talk) 14:00, 12 September 2009 (UTC)

That URL is safe. I's exactly what the URL describes: a faculty member at some school posting material for a lecture for his chemistry class. No Rick Roll or other nonsense:)DMacks (talk) 17:15, 12 September 2009 (UTC)

Thank you. Regretfully I and my countrymen will need such kind of support from free living people for unforeseeable times.95.112.165.86 (talk) 17:55, 12 September 2009 (UTC)

You need to be familiar with "electrophilic attack on enolates" eg [4] http://www.google.co.uk/search?hl=en&q=enolates+reaction&btnG=Search&meta=

There's a useful acetone/'acetone enol form' electron density map here http://www.chem.ucalgary.ca/courses/350/Carey/Ch18/ch18-1.html which shows why enols can react with electrophiles at carbon

This [5] is a far better visualisation of the critical step, showing the role of Mg2+, and the mechanism too. (Don't even ask me how they worked that out - I haven't got a clue - probably isotope labling experiments or something).

(Note that the enol based attack isn't as simple as usual since there is a OH next to the keto - making the intermediate structure approximately a 1,2 dihydroxy alkene... see that technically the reaction forms a bond between two carbonyl carbon atoms!!)

83.100.250.79 (talk) 12:15, 12 September 2009 (UTC)

Yeah I just started studying enol/enolate reacitons. And I am interested enzyme stuff besides the protein folding/induced fit stuff (which is fascinating but no too complex). I am interested in how the enzyme binds CO2, how the enzyme activates CO2 -- (why would CO2 make a ligand to Mg++? And is that a nucleophilic attack on the carbon dioxide carbon?) I find the sudden disappearance of two protons very interesting -- does the enzyme's basic amino acids somehow transport that away (without needing strong base in solution), because obviously that seems to stabilise the enolate intermediate long enough for CO2 to come in. What do the phosphates do in this step? John Riemann Soong (talk) 16:46, 12 September 2009 (UTC)

How did Eskimo or Inuit tribes defend themselves against polar bears before they had guns?

Since modern explorers use powerful guns for bear defence,what was their defence? 80.0.102.60 (talk) 12:43, 12 September 2009 (UTC)

No doubt the same as all peoples defended themselves against large predators before guns: with great difficulty. Plus fire, clubs, spears, organization, cunning, etc. -Sean 13:12, 12 September 2009 (UTC)

A google scholar search pointed me to Hunters of the Northern Ice, (unfortunately unavailable online) - an authoritative book on the cultural history of the Inuit hunters. More recently, discussions about conservation of bear and other wildlife seem to have a strong component of academic debate about just how embedded into Inuit culture these bear hunts really are/were. Especially now that the hunts are done with firearms, there is academic debate about whether modern bear hunts really preserve a cultural legacy. Polar Bear as a Resource cites the earlier book (and some other papers and books, but unfortunately these citations are hard to track down, and written in Quebecois). Nonetheless, the claim is that Inuit have been hunting nanuk for millenia. Nimur (talk) 13:46, 12 September 2009 (UTC)

Warding off predators only requires being able to do enough damage to counteract your food value. A person carrying a harpoon can't "win" a fight with a polar bear, but can give the polar bear a very serious wound. I believe the main threat from bears is in places where they rarely encounter humans -- when the two species mix, they learn to avoid each other. Looie496 (talk) 16:21, 12 September 2009 (UTC)

A vaguely similar idea occurs in signs in national parks advising what to do if encountering mountains lions, namely to fight back. Predators don't expect their prey to turn the tables on them, and unless they are really hungry, they will likely be warded off by a sufficiently painful defense put up by their potential prey. Baseball Bugs ^{What's up, Doc?} carrots 17:02, 12 September 2009 (UTC)

You can see this very clearly on a number of YouTube videos of bears vs. other animals. Grizzly bears, pound for pound, tooth for tooth, should be able to take just about anything in the forest, but there are lots of videos of them being basically run off by angry wildcats or wolves who are vastly smaller than they are and comparatively under-powered, but present enough of a trouble that the bear decides it would rather go elsewhere. There is one compelling one I saw awhile back of a very small wildcat that provided just enough threat that the bear decided to go eat some berries rather than potentially lose an eye. There's a lot to be said for not every fight having to be "to the death". --98.217.14.211 (talk) 18:03, 12 September 2009 (UTC)

Sounds similar to a video I once saw of a wolverine treeing a black bear. Not a grizzly, but still an impressive sight. Baseball Bugs ^{What's up, Doc?} carrots 20:12, 12 September 2009 (UTC)

Housecats have been known to do the same. Algebraist 20:17, 12 September 2009 (UTC)

And mice can scare the dickens out of people. Size is not everything. The peskiness factor figures into it. Baseball Bugs ^{What's up, Doc?} carrots 20:22, 12 September 2009 (UTC)

Compare the size of a human to that of a pitbull. Still, if a pitbull approached you snarling, with teeth bared, you'd likely instinctively run. --Kurt Shaped Box (talk) 22:56, 12 September 2009 (UTC)

Are you kidding? I would avoid a snarling chihuahua, never mind a pitbull. Basically, any critter armed with anything sharp (teeth, claws, stingers, etc.) is potentially dangerous. That brings up another point about the mountain lion. They say do not run. For one thing, the animal can probably outrun you easily. For another, it signals fear. If you stand your ground, you've got a better chance. No guarantee of success, but a better chance. Baseball Bugs ^{What's up, Doc?} carrots 23:02, 12 September 2009 (UTC)

It's a fair point - but it sounds like one of those things that's easier said than done. Standing your ground against a wild beast apparently intent on attacking you takes bollocks - and bollocks tend to shrink in the face of adversity, as the adrenaline and millions of years-worth of hard-wired instinct kick in and tell you to run for your life. Heck, some people run away when they see a spider on the wall. --Kurt Shaped Box (talk) 23:08, 12 September 2009 (UTC)

Awhile back, my wife moved to California from New England, and saw all of those "fight back against the wild cats! wave your hands in the air, and put your children on your head!" signs in the wilderness areas, and thought they must be a joke to fool people from out of the area into walking around waving their hands in the air, their children on their heads, for a good laugh from the locals. --98.217.14.211 (talk) 00:23, 13 September 2009 (UTC)

It's strangely a redlink, but the Life/Dinner Principle (originally discussed by Richard Dawkins, I think) notes that the prey has a much stronger incentive to go to the mat in a fight with the predator. --Sean 19:53, 12 September 2009 (UTC)

In many cases, a wounded predator is a predator that will starve to death. When you see (for example) lions hunting wildebeest on TV, there's a very good reason that they nearly always target the young, the old or the sick/injured. Whilst a lion probably could down take a healthy adult wildebeest, there's a very real chance that the wildebeest would inflict some nasty kicks on the way down. If one of those connected with a leg, then you've got one lion that won't be chasing after anything ever again... --Kurt Shaped Box (talk) 22:48, 12 September 2009 (UTC)

I watched a nature show once where a lioness took a kick to the jaw. She lived for weeks, but was doomed. :( --Sean 13:22, 13 September 2009 (UTC)

As it says at Polar bear#Indigenous people they used dogs to harry the bear while using spears or arrows. That of course is while hunting, but even when not hunting the dogs would give the alarm and then be let loose to go after the bear. There is the possibility that some Inuit might have used seal meat with sharpened bones inside to help kill bears. The idea being that the bear swallows the meat and the bones then puncture the stomach slowing it down so the hunters could catch up. Enter CambridgeBayWeather, waits for audience applause, not a sausage 18:59, 12 September 2009 (UTC)

They hunted them with dogs, knives, spears etc. Bear hunting gives lots of info on how to go about it. You can find more about the Inuit and their hunting at these pages: Inuit diet, Reindeer hunting in Greenland, Greenland Dog. Fences&Windows 23:18, 12 September 2009 (UTC)

1. They would know how to avoid attracting bear in the first place. Bears do not naturally want to interact with humans - so if there is no open trash pile full of goodies - they are much less likely to bother us.
2. These people live out in that environment their entire lives - they'd know where not to go and what not to do - they might simply never need to get involved with polar bears.
3. In some cases, I'm sure they didn't succeed - and occasionally, they'd suffer an attack. But so long as the number of incidents doesn't get too high, the consequences on the human population might not be so severe.

SteveBaker (talk) 17:37, 13 September 2009 (UTC)

I disagree with part of Steve's first point. Polar bears are very unlike your aaaaverage bear; my understanding is that they consider people perfectly reasonable prey. Part of it, I'm sure, is lack of options; the high arctic is not a place where you turn up your nose at a meal even at the best of times. There is little or no plant life there - virtually anything a polar bear wants to consume is going to kick up some kind of fuss. I don't know where I picked this factoid up, but I've heard that polar bears and cougars are the only animals native to North America that consider humans fair game, though cougars would rarely be bold enough to attack full-grown humans or people in groups. Other animals may be dangerous, may even be more dangerous in terms of possibility of being attacked/killed, but these are the two that will attack humans as a prey animal. Matt Deres (talk) 04:17, 14 September 2009 (UTC)

Not counting the mosquito, that is. Looie496 (talk) 05:39, 14 September 2009 (UTC)

Or Hannibal Lecter. Googlemeister (talk) 14:11, 14 September 2009 (UTC)

biosynthesis of phosphoric acid (charge balance on DNA part deux, OMG)

One thing that has come to amaze me is the sheer ubiquity of phosphate ions in the cell but everyone skips over where their conjugate H+'s go. Obviously I can't take in all these phosphate ions without some sort of counterion, but to avoid killing myself with acidity I need some sort of base as well. I guess animals can avoid this problem by not synthesising phosphoric acid and instead taking inert phosphates in solution in food (with some sort of metal cation counterion -- sodium maybe?) but this implies the plants have already dealt with the acidity.

I know a lot of foods are in fact, kind of acidic -- fruits, milk and so on, but I thought that was due to weak organic acids, not because of the synthesis of semistrong phosphoric acid, and I guess plants would relegate the whole phosphorus-fixing thing to the roots, which then delegate that to symbiotic bacteria or fungus, but now they need to deal with the acidity. Where do all the H+'s go? Are they absorbed by organic bases and then replaced with counterions? I'm basically wondering because it seems to me you must have a base-synthesis reaction coupled with DNA synthesis (and an ATP synthesis), because the more phosphates you produce, the more H+'s you produce, predictably.

And on yeah, charge balance on DNA. Now that I think about it, how is the electrostatic repulsion between phosphate groups not stronger than the hydrogen bonding between DNA strands? John Riemann Soong (talk) 17:05, 12 September 2009 (UTC)

?? The actual solids and liquids you ingest into your body are in rough electric balance, they only get charge-separated during metabolic processes - but the "other" charge always goes somewhere. Most body fluids seem to be mildly basic. For DNA charge balance, have you comsidered water solvation? Hydrogen bonding is important in the final structure of DNA. Solvation mediates the entire structure, and of course, in living systems nucleosomes do a lot of the organizing. I think that if you found DNA structural studies in aqueous vs. non-aqueous media, you would see a difference. Once again though, I got nuthin' for sources. Franamax (talk) 07:39, 13 September 2009 (UTC)

I mean naturally, but for the foods to be in electric balance, there must be some acid-base compensation going on ... maybe before the food was made (i.e. maybe it's at the level of phosphorus-fixing bacteria). John Riemann Soong (talk) 14:22, 13 September 2009 (UTC)

Astrophysics

In reading Numerical Methods for Astrophysics: An Introductio by Peter Bodeheimer, et.al., I ran across the term "mean particle separation". I am seeking a definition and perhaps some references to derivation of

n=l^1/3

AWBest (talk) 19:22, 12 September 2009 (UTC)

You forgot to tell us what is 'l' in that equation. Even without that info I'm willing to guess that equation is the very answer to your question above, that is it is the definition of "mean particle separation". Dauto (talk) 20:25, 12 September 2009 (UTC)

If 'n' is a "separation" - then it's unit is length. So 'l' would have to have units of volume. If 'n' is an average separation between particles - then 'l' would be something like the average volume occupied by a single particle. In a few articles I skimmed after a Google search on "mean particle separation astrophysics", the equation n=r^1/3 appears fairly often. SteveBaker (talk) 17:29, 13 September 2009 (UTC)

I would expect n to be a number density (e.g. 1 particle / cm³) and l to be a mean separation (e.g. 1 cm). Are you sure it's not n=l^-1/3 (with a minus sign in the exponent)? -- Coneslayer (talk) 17:14, 14 September 2009 (UTC)

September 13

Why are prisoners asked to cough during a body cavity search?

This may seem like a silly question at first but I'm being serious. Why are prisoners asked to cough when being strip searched? Specifically, what does the coughing accomplish? I couldn't find this information in the Body cavity search article. I tried googling it and discovered that doctors use the "drop and cough test" to check for hernias or tumors by observing the reflex action that the coughing triggers. But why would prison guards ask prisoners to do this? Are they also checking for hernias or does coughing cause a reflex action that causes any contraband to be dislodged from the rectum? -- œ^™ 00:48, 13 September 2009 (UTC)

Checking for Inguinal hernia. Baseball Bugs ^{What's up, Doc?} carrots 00:54, 13 September 2009 (UTC)

That's coughing during a medical. I can't see prison guards performing that kind of medical test during a strip search. --Tango (talk) 01:44, 13 September 2009 (UTC)

Coughing causes the anal muscles to relax, thereby aiding the insertion of a finger. Hence sometimes the release of flatus on coughing. —Preceding unsigned comment added by 79.75.1.246 (talk) 01:59, 13 September 2009 (UTC)

Perhaps it helps guards find things being smuggled in one's anus. Makes them more visible or susceptible to popping out. DMacks (talk) 03:40, 13 September 2009 (UTC)

This is the most likely explanation of why they're asked to 'bend over, spread their cheeks and cough', during a strip search upon admission intro in prison, however I have yet to find a reliable source that definitively verifies this. -- œ^™ 05:45, 13 September 2009 (UTC)

I recently watched a TV show where the guards were strip searching women. Rather than perform a cavity search they had them squat down and cough. It wasn't explicitly mentioned, but my interpretation was that doing that would expel (or at least shift, so that it became obvious) anything that was concealed in the vagina or anus - without having to do a cavity search. Blu-Ray Betamax (talk) 09:22, 13 September 2009 (UTC)

It would be interesting in an encyclopedic sense to note how and why this would work anatomically. Like maybe a section in the Body cavity search article explaining how coughing causes the pelvic diaphragm to move in such a manner that it dislodges anything inside body cavities. But once again, there's no sources explaining this anywhere and it all amounts to original research. -- œ^™ 18:51, 13 September 2009 (UTC)

Why does the OP think asking to cough is a part of the body cavity search? If this is from own experience, could it be that the searching officer just wanted to establish that they were being understood? Cuddlyable3 (talk) 23:17, 13 September 2009 (UTC)

No idea where OP got the idea, but it's used in "behind the bars"-type documentaries on prison life, and there are court cases that establish how it is (or is not) part of a valid search of a person. DMacks (talk) 00:13, 14 September 2009 (UTC)

Heh. No not from personal experience. Like DMacks said, I've seen it in documentaries and in almost every prison movie I ever saw, and have always been curious as to why. I guess there still ARE some things that you can't discover using the internet. BTW, what's "OP" stand for? -- œ^™ 00:36, 15 September 2009 (UTC)

OP seems to stand for "original poster." A lot of people get stumped by that. I did too. Bus stop (talk) 00:51, 15 September 2009 (UTC)

Phenomenon?

Our house (in northeastern US) has a wooden utility pole diagonally across the street which services us and three other houses. It is only a distribution pole for electricity, telephone and cable for the four houses and doesn't have a transformer or anything else unusual except for a metal junction box. The phenomenon that I notice each year is that a nearby (ten feet away from the pole) deciduous tree begins to lose leaf color and proceeds to drop its leaves about six weeks ahead of schedule. Does the utility pole have an aura of sorts which is screwing around with the tree's expected seasonal leaf cycle? hydnjo (talk) 01:36, 13 September 2009 (UTC)

Unlikely. Where are you getting this "schedule" from? There are lots of factors that determine when a given tree loses its leaves. Are they other trees of the same species nearby that lose their leaves at a different time? If not, it is probably just a type of tree that loses its leaves earlier than other types of tree in your area. --Tango (talk) 01:46, 13 September 2009 (UTC)

The "schedule" is from observing all of the other trees in the neighborhood. The tree is a maple with lots of others nearby which still have green leaves (for a few more weeks anyway) but this particular tree has already lost color and most of its leaves. There are no trees around here that drop their leaves at the end of August - only this one! The reason for asking the question is that this has been "bothering" me for a few years now. BTW, the phenomenon seems to be most intense at the elevation of the top of the utility pole and less so above and below that elevation. hydnjo (talk) 02:09, 13 September 2009 (UTC)

This sounds like some sort of tree disease rather than "aura" (by the way, you might be interested in Tesla's work). Of what species is the tree? Many diseases cause premature loss of leaves, often from the top down. Intelligentsium 02:28, 13 September 2009 (UTC)

You may have missed it - the OP said it was a maple (admittedly, that is a genus, not a species, I don't know if the OP has the expertise necessary to identify the particular species of maple). --Tango (talk) 02:40, 13 September 2009 (UTC)

(after e/c, mostly what Intel said just above) To test the proposed phenomenon, you would either have to cut down the utility pole and watch future year activity, or locate similarly equipped utility poles in your area and observe the surrounding flora. The metal box sounds like a pretty standard distribution box. I'd be looking first for other sources of stress on the particular tree. How well does the ground around it accomodate its root system? For me, that's the single largest source of "early-turning" stress on trees. Also, what do the dropped leaves look like? Do they have evidence of fungus or insect parasite damage? There are lots of reasons that one particular tree will suffer more stress than others, Mithra knows that I suffered much watching some of the trees I planted myself fail to thrive while others did fine. You could always sneak over at night and pump a bit of Miracle-Gro into the root system - in spring / very early summer... Franamax (talk) 02:37, 13 September 2009 (UTC)

Also, it's possible that your tree is just a natural variant, and possibly a successful one. How well does it thrive, and what is it's output of seed? End-of-season activity for a tree is a balance between storing that last bit of sugar down into the root system and the risk of losing valuable organic compounds in an early frost. Maybe this particular tree is just an outlier exploring a particular evolutionary strategy. You will need to enlist your children to check on how well it does for the next hundred years or so. Franamax (talk) 02:50, 13 September 2009 (UTC)

Oh, thanks Franamax! A bit of context: I'm sitting on my deck with my wife enjoying the afternoon sun and have noticed this happening for several years now. My wife who thinks that I know everything asked me "why does this happen to that tree every year?" So, I take another sip and tell her that I'll get back to her on that one and change the subject. The proximity of the pole and the tree piqued my curiosity an so I probably made an unwarranted connection that might support my infallibility (with support from y'all). Oh well - maybe a tinfoil shield... awh screw it! hydnjo (talk) 02:56, 13 September 2009 (UTC)

Be very careful. I have reliable evidence that certain tinfoil manufacturers are in fact front companies for the NSA. In fact I'll tell you who they are: Al&cg%, RusQvW59* and Chni7&dfR43. I hope that information is of help. Also, it's often useful to punch holes in the tinfoil to allow breathing, although the CIA controls most of the pokey-instrument makers. Sigh. Franamax (talk) 03:10, 13 September 2009 (UTC)

OK - I'll walk (drive) around the neighborhood to see if my "pole/tree" connection is unique. Stay tuned :( hydnjo (talk) 03:09, 13 September 2009 (UTC)

Actually, I was suggesting first to look for unique conditions associated with the particular tree (other than utility poles). That would involve walking over to inspect the particular environment of that one unique living thing, and the dropped leaves which may give clues to its' own circumstances. But you can look for wider correlations first if you want! Another thing to check is whether your tree has bugs in the bark or excessive cracking of the bark that might expose it to excessive stress. Franamax (talk) 03:19, 13 September 2009 (UTC)

And apropos of recent off-desk discussions, this is an area where I couldn't pull out any great source to help, but I do feel that my own speculations and personal experience are helpful contributions worthy of inclusion here. Franamax (talk) 03:19, 13 September 2009 (UTC)

I remember seeing a while ago that there was some evidence the branches of trees very close to high power lines grow slightly faster and have more leaves, but that's the exact opposite of what the OP is talking about if anything. The lines near your house would have undetectable effects. Dmcq (talk) 07:40, 13 September 2009 (UTC)

A random wild guess: the magnetic field generated by the powerline affects pollinators and seed dispersers. John Riemann Soong (talk) 14:41, 13 September 2009 (UTC)

So this tree has this condition - and there happens to be a power pole nearby - but correlation does not imply causation. There could be something in the soil beneath the roots of the tree that causes this - a greater or lesser degree of soil nutrients perhaps. Or perhaps it's in a more exposed position than the other trees. Maybe the tree has some kind of infection. Perhaps utility pole is a wooden one that's coated with some kind of wood preservative that leaches into the soil in wetter weather towards the end of summer? Perhaps the tree is a lot older (or a lot younger) than the others in the area? Maybe it simply has some different genetic makeup than the others? You can come up with dozens and dozens of possible reasons - but until you do some actual experiments - you really can't come to any really solid conclusions. What you CERTAINLY can't do is to start assuming that some pseudo-scientific clap-trap about auras has anything to do with it. Occam's razor says that this is the least likely explanation - so it should be the last one to consider after you've ruled out every other cause. It's up there with "Maybe God doesn't love this tree as much as the others?" SteveBaker (talk) 17:17, 13 September 2009 (UTC)

Clearly, this is a medical question requiring diagnosis and treatment. As you should know, with requests for medical advice you are barking up the wrong tree on this RD. URGENTLY suggest to the prematurely denuded maple in question to see a tree surgeon ASAP! I believe there is one just 100 metres down the road form the power pole. --Cookatoo.ergo.ZooM (talk) 20:11, 13 September 2009 (UTC)

Forests Vrs. Deserts

Why is it that some regions are deserts while others are tropical rain forests? I understand that rain shadow is a consideration, but I am guessing there is a lot more to ecological development than just mountain placement.Nkot (talk) 02:52, 13 September 2009 (UTC)

I think that ecological is an afterthought to precipitation. I would imagine in a hand-wavey sort of way that something in atmospheric circulation would be important in regulating some deserts (e.g., the Sahara), while others (e.g., Atacama) would be a rain shadow. Arctic deserts might be because of the relationship between temperature and precipitation (harder to get much precip in very cold places). But hopefully someone who knows more than me responds. Awickert (talk) 02:58, 13 September 2009 (UTC)

The most important factor is atmospheric circulation, particularly the Hadley cell mechanism, which produces rising air near the equator and falling air in the subtropics. It causes the air over the tropics to be mainly moist, producing wet environments, and the air over the subtropics to be dry, producing mainly deserts and semideserts. Looie496 (talk) 03:10, 13 September 2009 (UTC)

The great deserts of the world typically have a large land mass between them and the potential moisture toward the equator. The Sahara and the Gobi are obvious examples. In the USA, you can practically draw a straight line north, tangent to the west edge of the Gulf of Mexico, as a separator between the moist and the dry areas of the USA. Baseball Bugs ^{What's up, Doc?} carrots 03:18, 13 September 2009 (UTC)

And yet none of what I've seen yet here seems to explain the vast expanse of the boreal forest, which occurs on large continental land masses. Unfortunately I have no good explanation for that either. :( Franamax (talk) 03:27, 13 September 2009 (UTC)

Franamax, Looie expained it above. It is due to atmospheric planetary circulation. The southward moving airmass from the polar cell joins the northward moving airmass from the mid-latitude cell around 60 degrees and the general upwards motion caused by that leads to generous rain fall. Dauto (talk) 06:55, 13 September 2009 (UTC)

See also desertification. --Sean 13:54, 13 September 2009 (UTC)

Well ecology can affect climate too, what with transpiration, Rnet and whatnot. Forests retain topsoil... water doesn't evaporate as quickly, and in a controlled manner (through transpiration, controlled by stomata). Destroy the forest, erosion destroys the topsoil, and suddenly the thing does become a desert even though the area was once very rainy. John Riemann Soong (talk) 14:37, 13 September 2009 (UTC)

Becauae there's land, the ideal Hadley cell is distorted so there's no desert on the east sides of continents. What J. R. Soong said is already happening in cities in Indonesia or Malaysia or something. The city is getting dry heat waves (which were almost unheard of 20 years ago). The rainforest's existance itself produces it's own existance. Sagittarian Milky Way (talk) 16:00, 13 September 2009 (UTC)

Why is Somalia the only place on the equator with desert (!)? And why does the Peru Current penetrate so far? It brings bone-chilling water more equatorward than any other place in the world. Sagittarian Milky Way (talk) 16:00, 13 September 2009 (UTC)

The Humboldt Current (what you call the Peru Current) brings cold water up from the depths of the ocean near Antarctica, playing an important role in the global climate system. A displacement of this current, which occurs when trade winds weaken and warm water starts blowing westward toward South America thereby cutting off the upwelling of cold water, causes the devastating El Niño. Also, the Atacama Desert extends approximately to the equator due to the effects of this current, the Desert of Somalia occupies some of Kenya at the equator, and depending on your definition, the Andes mountains and highlands of Africa could count as desert as well. Also, there are some studies that suggest global warming could result in the Amazon Rainforest turning into desert (which is on the Equator), thereby turning the American Midwest into desert as well. Much of this connection also has to do with Atmospheric wind patterns. Wind blowing off the Sahara Desert produces the Saharan Air Layer. ~AH1^(TCU) 20:20, 13 September 2009 (UTC)

• You're right. (Wikipedia's Koppen map makes my book's look like a crude drawing). The high altitude thing is pretty much a given and the low precipitation in alpine climates are also characteristic of tundra, some ocean and icecap, but it's more useful to have those seperate terms.

• Yes, I know El Niño's bad. Even though there's one now, [www.wunderground.com/tropical] shows unswimmable SSTs at latitudes usually considered immune to coldness (near sea level anyway). South America sticking out further toward the poles than any other eastern boundary current bordering landmass probably helps. Sagittarian Milky Way (talk) 18:39, 16 September 2009 (UTC)

Virtual Work (again!)

This is basically a follow up to my original question here. I just had my exam on the said topic, and I really have solved sums involving indeterminate systems using the principle of Virtual Work, albeit not really understanding the concept behind it. For example, consider this book, our textbook for the course, which has a few worked out examples on the topic. Figure 10.8 shows a system with two pin joints, ie, which is indeterminate. However, it is solved, along with a few other such systems... I need somebody to tell me if I've grossly misunderstood something, or if Virtual Work really is that powerful... Rkr1991 ^{(Wanna chat?)} 07:29, 13 September 2009 (UTC)

You could find all the forces just by treating each rigid piece separately, requiring that the net force and net torque on each piece is zero, but that's sort of a pain. I'm not sure if this is the source of the confusion, but the angles involved here are fixed, so the joints don't add a degree of freedom. In general if a method for solving the mechanics of a system is fully derived from Newtonian mechanics then it's impossible for it to tell you anything more than Newtonian mechanics does. Rckrone (talk) 17:03, 13 September 2009 (UTC)

The pin joint gives two reaction forces. Two pin joints give four. With only three equations (in 2D), how do you solve that usong Newton's Laws ??Rkr1991 ^{(Wanna chat?)} 07:30, 14 September 2009 (UTC)

There are a bunch of ways to formulate the equations so I don't know specifically which ones you're referring to, but here's how I would do it with forces.

For rod B, call the magnitudes of the components of the force acting on the bottom end B_1x and B_1y and the magnitudes of the components acting on the top end B_2x and B_2y, and use the same labeling for rod A. Since the torque and net force on each rod are zero, A_2x/A_2y = B_2x/B_2y = tanθ. A_2x = B_2x by Newton's third law, and P = A_2y + B_2y. From these relations, B_2y = P/2, so B_2x = (P/2)tanθ. Since net force on B is zero, B_1x = B_2x = (P/2)tanθ. Rckrone (talk) 20:31, 14 September 2009 (UTC)

Beer traps

How to beer traps work? This web page suggests what I had assumed, which is that the slugs become intoxicated, so they drown, but I recently bought some new traps which came with a yeast sachet which you are supposed to mix water as bait. Obviously they are attracted by the yeasty smell but I wouldn't have expected them to be poisoned by the yeast, or to willingly and soberly drown in the solution.--Shantavira|^{feed me} 08:13, 13 September 2009 (UTC)

Maybe the yeast satchet contains glucose so when you combine it with water it's sufficiently fermented to intoxicate the slugs? Are you sure the slugs don't just get stuck in the traps? Nil Einne (talk) 11:35, 13 September 2009 (UTC)

They drown in any liquid! Water works fine as a slug trap, but you need some smell of decay (beer, yeast etc) to atract the slugs. I don't think they are intelligent enough to avoid drowning if the attraction of food is strong enough. Dbfirs 11:47, 13 September 2009 (UTC)

If too much of this kind of thing is done, it could result in artificial selection of those slugs that are smart enough to avoid drowning. Assuming there are any. Baseball Bugs ^{What's up, Doc?} carrots 11:52, 13 September 2009 (UTC)

Evolution is efficient but lazy. It's more likely to drive an aversion for beer than the development of intelligence (maybe this explains my mother in law?) Anyway, the mechanism of attraction this guy gives is questionable at best. First, he says it's the yeast smell that attracts the snails, though most commercial brews are filtered to remove any yeast that may offend the literal consumer with a clouded beer. Second he says that lagers don't work because they're fermented with sugar. I'm an avid brewer, and without going into detailed explanation, I'll just say "bullshit". Ales (as opposed to lagers), are more flavorful due to the esters (and various other chemicals) produced at higher fermentation temperatures (around 70F as opposed to 55F), and often (but not always) have more residual sugars as well. This is probably what attracts our little friends. – ClockworkSoul 12:58, 13 September 2009 (UTC)

"Smart enough" in a broad sense, i.e. inclined to avoid it for whatever reason, as per your explanation. Unintended artificial selection is a major consequential risk of trying to wipe out populations of critters that can evolve quickly, such as insects and microbes. Practically speaking, a few beer traps wouldn't have such impact - except maybe locally. Baseball Bugs ^{What's up, Doc?} carrots 13:07, 13 September 2009 (UTC)

I really doubt that the critters get "drunk" before they drown - they are air breathers - I'm pretty sure they just drown. SteveBaker (talk) 17:04, 13 September 2009 (UTC)

Literally Original Research: I once divided an aquarium in half, and in half I placed 12 slugs and a dish of beer. In the other half, I placed 12 slugs with a dish of the same volume of water. There was mostly dry area in each half, and no other food. Slugs were randomly assigned to conditions. The number of slugs per condition was recorded over time. In the beer half, as in the water half, slugs crawled into the liquid, stayed a while, and crawled out seemingly none the worse. The number of living slugs in each half decreased as time passed for several days. There was no apparent difference in the survival rates, with 1 or 2 alive in each half at the end of data collection. The lucky survivors were released.The important observation is that the beer dish did not fill up with slugs who died the first time they crawled into it. Edison (talk) 20:18, 13 September 2009 (UTC)

Was there any difference at all in their behaviour? Frequency of visits to the liquids, duration of visits etc. Martlet1215 (talk) 21:15, 13 September 2009 (UTC)

Or state of inebriation? Baseball Bugs ^{What's up, Doc?} carrots 07:25, 14 September 2009 (UTC)

Slugs are hermaphrodites - after a few beers EVERYONE starts to look gorgeous! SteveBaker (talk) 17:15, 14 September 2009 (UTC)

growth of a cell membrane

How exactly does a cell grow? Okay sure it metabolises, takes in nutrients, synthesises membrane proteins and whatnot and some enzymes are probably producing those fun phospholipids, but how do you add those units to the existing membrane without disrupting it? Do phospholipid molecules and proteins just migrate there and wait for a small "hole" to open up? (In a sort of weird cell bio equivalent of a vacancy defect?) Does an enzyme make a hole in a membrane and then some other helper enzyme insert the phospholipid/protein into the membrane?

Are their enzymes that make temporary holes (not permanent channels) that allow say, enzymes to pass through? How do you catalyse the formation of an extracellular matrix outside of the cytosol? John Riemann Soong (talk) 14:30, 13 September 2009 (UTC)

There are very complex mechanisms for cells to insert proteins/lipids into the membrane and to deliver components into the extracellular matrix. Mostly it occurs through fusion of vesicles containing lipids and proteins. Have a look at endocytosis and exocytosis. You could also read secretory pathway. Of course, the next question you'll want to ask is "how are vesicles formed?" For that, you'll want to read vesicle (Biology), endoplasmic reticulum, and Golgi apparatus. Ok, that should be a good start. --- Medical geneticist (talk) 17:26, 13 September 2009 (UTC)

Okay, I have some vague introductory conception of those from ap bio... well admittedly I guess proteins / phospholipids would be transported along vesicles or via the cytoskeleton. How does vesicle fusion occur? On the macroscopic scale, don't two bubbles normally repel each other? John Riemann Soong (talk) 17:35, 13 September 2009 (UTC)

See clathrin and dynamin for details on how vesicles are "pinched" off of a membrane. See SNARE (protein) for details on vesicle fusion. There are still details to be ironed out, but that's the basics of it. --- Medical geneticist (talk) 02:13, 15 September 2009 (UTC)

Is this correct?

Can you please check over this work. It took me a very long time to re-type everything again, but I know there are a lot of smart people on WP. The bullet which speaks about dissolving is about solubility in water. After seeing the facts stated below, what would the answer to this question be : 1. How does the range in properties of salts compare molecular compounds? Would somebody please put a talkback on my talk, when this has been answered. warrior4321 15:40, 13 September 2009 (UTC)

Steel

• solid
• gray/silver
• conductive
• does not dissolve
• no crystal structure
• metallic bond

Gel

• liquid
• blue
• not conductive
• dissolves
• conductive when solution
• no crystal strcture
• polar covalent bond

Copper

• solid
• red/copper
• conductive
• does not dissolve
• no crystal structure
• metallic bond

Wood

• solid
• brown
• not conductive
• does not dissolve
• no crystal structure
• polar covalent

Marble (calcium carbonate, not toy marble)

• solid
• brown
• gray/white
• not conductive
• does not dissolve
• has a crystal structure
• ionic bond

Sugar

• solid
• white
• not conductive
• dissolves
• crystal structure
• ionic bond

Salt (sodium chlroide NaCl) (not ionic salts)

• solid
• white
• not conductive
• dissolves
• crystal structure
• ionic bond

Copper (II) Sulfate

• solid
• blue
• not conductive
• dissolves
• conductive in a solution
• crystal structure
• polar covalent bond

Air (Nitrogen)

• gas
• transparent
• not conductive
• does not dissolve
• no crystal structure
• polar covalent bond

All correct except:

Steel has a crystal structure.

A gel is not a liquid or a solid - they're in between. Also a lot of intermolecular bonds in a gel. Also might not be conductive in solution - it depends on the gel.

Copper (same as steel) - has a crystal structure.

Wood - lots of colours including brown, ebony, beech etc , also has a composite (material) structure if that matters.

Marble - yes - but also polar covalent bond in carbonate.

Sugar sucrose - NOT ionic. bonds are covalent, plus intermolecular forces between the molecules - hydrogen bonding.

Salt - all ok except what does "not ionic salts mean?" - NaCl only?

Copper Sulphate - polar covalent bonds and ionic bonds.

Nitrogen - the covalent bond is non-polar. Dissolves a very small amount in water.

Also you missed conductivity in water for salt, sugar

As for your question - I suggest make a table of list of properties in two columns, with mostly covalent in one column, and mostly ionic in the other and compare. However it's already half done for you at Ionic compound77.86.47.174 (talk) 17:33, 13 September 2009 (UTC)

The properties you described for copper(II) sulfate are for the hydrated version. I'm not sure whether it's asking about that or about the anhydrous version. Also nitrogen dissolves a little. I don't know if that counts or not. Rckrone (talk) 17:28, 13 September 2009 (UTC)

Many crystals, especially ionic crystals, conduct electricity when they dissolve. That's actually because they're good charge carriers. (They're ions). They're just not very mobile in the solid state. If you melt salt, it becomes highly conductive. (The reason why solid metal can be conductive is because of this thing that gets formed called a valence band.)

Also, I think you're wrongly assuming that crystals have to be ionic. Polar substances form crystals (and in fact, so do heavy nonpolar substances). Look at all those OH groups on sugar, plus some hydrogen bond acceptors (the ethoxy group). As you can see, ethanol has a very low melting point, only because it forms a fragile crystal structure that can be broken easily at higher temperatures. John Riemann Soong (talk) 19:51, 14 September 2009 (UTC)

In addition, the majority of wood is made of lignin. Look at all that cross-linking! John Riemann Soong (talk) 04:42, 15 September 2009 (UTC)

Real time (or time based) public transport information on maps

Time Based maps of Public Transport has 2 links to time based public transport maps - that is it can tell you right now where many transport units, such as buses or trains, are actually or scheduled to be on a map.

Are there any other websites like that - and even websites which have animations about where a public transport unit has been in the past? 118.208.97.169 (talk) 16:23, 13 September 2009 (UTC)

Yes, there are loads but I don't think the urls are easily available. My flatmate is a bus driver and he tells me that National Express West Midlands has a control room where they can see the location of all their buses. He doesn't know the wesite address but it is likely to be accessible. www.livebus.org has something similar to what you want.--Shantavira|^{feed me} 16:43, 13 September 2009 (UTC)

If ferry boats count there are a number of real-time GPS-based maps of the Washington State Ferry vessels here. For example, this page shows the current locations of the two ferries on the Edmonds-Kingston run. Pfly (talk) 07:32, 14 September 2009 (UTC)

Thanks for that. I tried looking at livebus but I couldn't work out the interface. Also the Midlands one I did a google search and went to the web page but couldn't see anything. I'm mostly looking at animated ones where you can see it move so that counts out the last one as it's a static display. —Preceding unsigned comment added by 118.208.97.169 (talk) 16:03, 15 September 2009 (UTC)

I've found this link mashups directory. Go there and click on real time. I think those are most of em. But I would love to see more. 118.208.97.169 (talk) 17:36, 17 September 2009 (UTC)

Time freezing

One of Don Rosa's pseudo-scientific Donald Duck comics involves Gyro Gearloose's new invention, which freezes time everywhere outside a small sphere outside the point where the invention was activated, and on further request, reactivates time everywhere. The Beagle Boys steal the invention and use it to steal Scrooge McDuck's money. Now, for the sake of suspension of disbelief, let's ignore that it's just a faerytale and such an invention can never be invented in real life. The point of my question is, wouldn't such an invention also freeze the air steadily in place outside the sphere of activation? What happens if someone runs against air that refuses to so much as budge a molecule? Will it become an impenetrable wall, will the air molecules rip through the intruder's body, or what? JIP | Talk 18:32, 13 September 2009 (UTC)

As you say, it's a fairytale. We can't ignore that. It is impossible, so what happens will be whatever the person making it up says will happen. To say what would happen we would have to know how it was done, which we can't know because it can't be done. --Tango (talk) 18:43, 13 September 2009 (UTC)

Well that answer was entirely worthless. What I only wanted to know is, if there somehow is a mass of air that just won't move, not even a single molecule, can such a mass of air be penetrated at all? It's the same bloody thing every time I ask about a scientific detail about a fictional story. The first reply is always "it's fictional, so anything what-so-bloody-ever goes". JIP | Talk 18:50, 13 September 2009 (UTC)

It wasn't worthless at all, in fact it was right on the money. You're asking us to fill in the gaps in a fictional and impossible scenario posed by someone else's imagination, so it's not absolutely answerable by anyone except (possibly) its author. I could see at least a couple of scenarios, and there could be dozens more: (1) All the molecules in the universe could be frozen in place, and unmovable, in which case the answer obviously is no, nothing would budge, including the air molecules, in which case you would be stuck inside that "bubble" until you turned the machine off. (2) They might be frozen in place, but movable. For example, a frozen person (as per that Twilight Zone episode and similar fanciful scenarios) might still be able to be nudged aside. But those are large objects. As noted by an editor below, the writer would have to answer the question of what would happen at the molecular level. Even if you could push the air molecules aside, what would happen if you inhaled them? Would they regain their motion because they're in your "sphere"? Or would they remain motionless, and suffocate you? Baseball Bugs ^{What's up, Doc?} carrots 19:35, 13 September 2009 (UTC)

Like, say, Maxwell's demon ... fictional and impossible. Nobody could extrapolate any useful information from conjectures about that. 81.131.38.252 (talk) 19:49, 13 September 2009 (UTC)

There is a difference between a well-defined thought experiment and a work of fiction. Maxwell's demon explains precisely what happens, it just has one simple (but impossible) assumption - that you can have something that lets things through or not depending on their speed. --Tango (talk) 20:00, 13 September 2009 (UTC)

I would guess that the 'frozen time air' would cease movement as long as the machine was in operation, but a non 'time frozen agent' would be able to brush the air aside - like walking against the wind - however this would technically leave a vacuum behind them, and a region of highly compressed air in the region of the envolope of motion. Obviously if the 'frozen time' region can not be altered the machine is worthless..

This would mean that once time was restarted there would be loud bang, as the air pressure differences created by motion through the air re-organised to equalise pressure.

There would be other problems such as breathing - ie does time start again once the air is inside the body - if so where - can the oxgygen be allowed to diffuse into the lungs - technically this requires time to be in motion..77.86.47.174 (talk) 19:15, 13 September 2009 (UTC)

This is a much better answer, thanks. AFAIK, "time frozen" air means air that literally can't be moved, so it can't even be brushed aside. Is air dense enough so that if it literally can't move, not even a single molecule, it's impenetrable? I also understand the breathing problem. If air can't move, it can't enter someone's lungs either, so once the person leaves the sphere of the device's initial activation, he/she will eventually suffocate. JIP | Talk 19:23, 13 September 2009 (UTC)

How is that answer better? The answer is as fictional and nonsensical as the question. Movement means a change of position over time, you can't have movement if you don't have a passage of time, it makes no sense. --Tango (talk) 19:28, 13 September 2009 (UTC)

Tango is right. There can't be a mass of air (in the gaseous state) that won't move; that's not permitted by the laws of physics, so there's no sense in asking what the laws of physics say about that situation. All that 77.86.47.174 did was invent further fantasy on top of Don Rosa's. -- BenRG (talk) 19:36, 13 September 2009 (UTC)

The more "practical" scenario, the one seemingly posed by The Twilight Zone and by Gyro Gearloose and some recent film on the subject whose name escapes me, is for large objects to freeze while air continues to flow freely so that you don't suffocate. Another factor: The world would probably have to keep turning also. In either the book or film version of H.G. Wells' The Man Who Could Work Miracles, he wished the world to stop. It did, and then everything and everyone went flying off of it. At that point he asked for his last wish - to put everything back and take his power away. Baseball Bugs ^{What's up, Doc?} carrots 19:40, 13 September 2009 (UTC)

The physics paradox posed by this idea was addressed, at least in part, by a Star Trek episode in which certain humans were living at an "accelerated" pace, such that the humans around them appeared to be frozen but in fact were moving, only extremely slowly by their reckoning, and were unaware of those who were living at the accelerated pace because they moved too fast, by our reckoning, to register on the senses. That approach could have a much better chance of success than literally freezing everything in place. It also sounds likely to be impossible, but not necessarily absolutely impossible. Baseball Bugs ^{What's up, Doc?} carrots 19:49, 13 September 2009 (UTC)

I frequently dream about time-stopping devices. Besides the problem of breathing, there are also questions like: do electrons stop holding things together? (What are things like to touch?) Does gravity stop happening? Does light stop moving? And a particularly interesting one, I think, is: when time is restarted again, where has the information about the momentum of objects been stored, so that they can continue to move as they were moving before? Which is also a question that applies to ordinary life. Maybe it has an obvious answer that I don't know about. 81.131.38.252 (talk) 19:44, 13 September 2009 (UTC)

The basic problem with these scenarios is the same one that arises with backwards time travel: They just plain don't make sense, because they postulate unworkable paradoxes. "When you start with invalid assumptions, you're liable to get interesting results." An even more practical (well, not practical, but theoretically possible) approach would be not to literally stop time, but simply to render everyone unconscious (i.e. asleep) for some stretch of time. Baseball Bugs ^{What's up, Doc?} carrots 19:51, 13 September 2009 (UTC)

Yes, that would be much less interesting. 81.131.38.252 (talk) 19:57, 13 September 2009 (UTC)

The possible is often much less "interesting" than is the imaginary. It's a nice fantasy, to imagine backwards time travel or putting a stopwatch on time for everyone except yourself (Groundhog Day is another variant on these ideas). You can fantasize about forward time travel, but that's much less "interesting" since it's what we're doing anyway. But it's also much more interesting, if you want to actually do something, as opposed to fantasizing about something that's impossible. Baseball Bugs ^{What's up, Doc?} carrots 20:14, 13 September 2009 (UTC)

The premise may or may not be interesting, but how interesting the resultant story is is entirely in the hands of the author. A world where everyone has suddenly fallen asleep? You could make a great story out of that. Vimescarrot (talk) 20:16, 13 September 2009 (UTC)

As, for example, Nicholson Baker did in The Firmata. Also, who else here remembers that old Australian TV show The Magic Boomerang? 87.81.230.195 (talk) 20:25, 13 September 2009 (UTC)

That show was about stopping time, which is much less interesting than a bunch of people falling asleep, and so must be very dull indeed. Andy Warhol's Sleep is a superior work. 81.131.38.252 (talk) 20:49, 13 September 2009 (UTC)

The OP has received extensive answers. It would be appropriate for the OP who is supposed to be an admin here to reconsider the unpleasant tone of their 2nd post above. Cuddlyable3 (talk) 22:54, 13 September 2009 (UTC)

It truly is a meaningless question - the laws of physics are tightly intertwined - you can't yank one of them out, rewrite it and wedge it back in again without creating meaningless contradictions in the other laws. Hence the question is meaningless - as are ALL of the above answers that attempt to make sense of it. Our OP should realise that the questions he/she "likes" are in no way better answers than "The universe explodes" or "Everything turns bright pink - but otherwise behaves normally"...it's a meaningless question. Without meaning in the question, the "answers" have no meaning. You might as well make up any random fiction that makes you happy - really. So if it makes you happy for me to say "no, the sphere of time wouldn't be able to move" - then fine - take away that answer and enjoy the thought of it - but don't think for one moment that there is any rational scientific truth behind that statement. The amount and quality of meaning is PRECISELY the same as if I said "yes, the time frozen air molecules would just be wafted gently away" - or "The time-frozen atoms would be forced to undergo a fusion reaction with the moving molecules and the whole thing would blow up like a fission bomb" - or "14 green aardvarks would materialise from thin air and ask you nicely if you would please turn off that damned annoying time gizmo."...all of those are equally good answers if the laws of physics are all completely turned around compared to reality. So - yeah - it's a meaningless question. Sorry if that doesn't fit into your world-view. SteveBaker (talk) 23:21, 13 September 2009 (UTC)

What we're getting into here is some interesting meta-issues about the proper way to answer counterfactual questions. I learned a lot about the difficulties they raise from Douglas Hofstadter's book "Goedel, Escher, Bach" -- but unfortunately I don't think I could reduce it to a summary. The gist of the problem is that counterfactuals are senseless from a purely logical point of view, yet somehow we humans frequently manage to extract information from them. Looie496 (talk) 23:50, 13 September 2009 (UTC)

Indeed. The problem is with the degree and nature of the counter-factual. If I were to ask "If my car could go 1 mph faster than it really can - what would it's gas consumption be?" - then no really fundamental laws of physics are violated - and perhaps some sort of a reasonable stab at an answer could be found. But if I ask "What would the volume of a one meter sphere be if Pi was exactly 3 ?" - then absolutely no reasonable answer answer is possible. The universe would simply not function in such a situation - we don't know whether there would be "spheres" or the concept of "volume" at all - and if there was, what the equation for their volumes might be is impossible to fathom. The question we're given here (arguably) falls between those two extremes...but closer to the Pi=3 end of the scale IMHO. SteveBaker (talk) 01:40, 14 September 2009 (UTC)

This is well beyond the accuracy (or is it precision?) of Pi somehow being exactly 3. It's more on the order of "what would happen if a circle's diameter and circumference were identical?" That can only happen if the universe shrinks down to a singularity - which is what I was thinking might happen with gyro gearloose's instrument. All molecular motion ceases. The temperature is not "near" absolute zero it's exactly at absolute zero. And maybe, just maybe, everything collapses into a singularity. Then we start over again, with a big bang. Baseball Bugs ^{What's up, Doc?} carrots 02:01, 14 September 2009 (UTC)

Obviously the volume would be 4 cubic meters. Har har har harumph. (I did not miss the point, I'm making a meta-point about the way the human mind works.) Looie496 (talk) 02:22, 14 September 2009 (UTC)

So the universe might shrink down to a cube. That would be interesting. I knew this discussion seemed vaguely deja vu.[6] Baseball Bugs ^{What's up, Doc?} carrots 07:35, 14 September 2009 (UTC)

Okay, ignoring the context that's getting people het up, here's how I'd go about thinking about it. What would happen if you try to push something with the area of the molecules in a layer of air, that was firmly fixed in place?

First, what is that area? Well the number density of dry air is about 2.5*10²⁵ m^-3. Assuming a Van der Waals radius of about 1.6*10^-10m as air is mostly Nitrogen, consider a layer of air one VdW radius thick* and equal to the cross sectional area of a human. For an order of magnitude estimate, let's say 1m². Thus we get the number of molecules N = n * V ~ 2.5*10²⁵ * 1.6*10^-10 ~ 4*10¹⁵. The area of these, again using VdW radii, would be A ~ N * π r². This comes out to A ~ 3*10^-4 m².

A sensible next step is to compare this number to the area of a bed of nails. Most of the articles I find are woefully lacking in numbers, but maybe someone else knows this?

* This is a major simplification. Since skin bends, it seems reasonable to suggest that the relevant layer could be thicker. AlmostReadytoFly (talk) 09:57, 14 September 2009 (UTC)

There is nothing wrong with your internet. Do not attempt to adjust the picture. We are controlling packet protocol. If we wish to make the font larger, we will bring in the <big> tags. If we wish to make it smaller, we will tune it to a <small>whisper</small>. We will control the <hr>. We will control the scroll-bar. We can source the <image>, make it <blink>. We can change the link to a soft redirect or sharpen it to a hard link. For the next hour, sit quietly and we will control all that you see and hear. We repeat: there is nothing wrong with your internet. You are about to participate in a great adventure. You are about to experience the awe and mystery which reaches from the inner mind to... The Outer RefDesk. SteveBaker (talk) 17:11, 14 September 2009 (UTC)

I release the following tale under GFDL.

It was a dark and stormy night. Working alone in the physics laboratory of the University the Professor peered through the microscope at the tiny green crystal that had been brought back from the crashed UFO discovered on the Moon. How they had laughed at his theories, those professors who thought they knew all there was to know about the semiconductor crystals that make transistors work. But now he would show them all. Now he would show those know-it-alls who had the temerity to reject his original research from Wikididdlypedia. He had waited for this moment, waited for a day when the University would be empty, waited for a day when the giant megafusion project would be down for maintenance so that he could draw power unnoticed from its mighty banks of polychromatic condensifiers. Taking a deep breath, he moved his radar solenoid lever a notch forward. An almost imperceptible glow arose in the crystal. Yes yes! he gasped, this was the time dislocation that his calculations had predicted! Those fools. Those moribund simpletons. Of course they had analysed the crystal looking for any tiny dislocation in the crystal lattice, such as could be found in a silicon crystal to which has been added a tiny impurity that would make it a semiconductor. And what had they found? Why, nothing. Indeed the crystal had an unfamiliar lattice structure but nothing about it supported the idea that the unknown designers of the crashed UFO had used transistor technology. But what of his theory that the lattice of the alien crystal contained a time dislocation? What if he took this theory further to say that the crystal could be used to amplify its time dislocation? That was no less logical than saying a tiny transistor can control a huge machine, if enough power is provided. He advanced the solenoid lever another notch. The crystal began to sparkle with tiny lightning flashes inside. In fact the flashes began a millisecond before the lever reached its notch. This was the time dislocation in action, thrusting the crystal lattice into the future when the solenoid power would be increased. Impatiently he swung the lever to maximum. The ceiling lights in the laboratory dimmed as megagigawatts of power were directed into the time crystal. An outside observer would have heard a muffled implosion as air rushed in to the spherical vacuum that arose at the instant that the Professor, his apparatus and the laboratory ceased to exist. Everything in a sphere of pi squared yards radius from the crystal had departed from normal time. This was how the civilisation of Atlantis had vanished in ancient time. Among their inhabitants had been alchemists who in their search for the philosopher's stone had stumbled on the time crystal. The UFO that crashed on the Moon had carried the last refugees from Atlantis. The Professor lived. Inside the sphere nothing seemed changed, except that the wind and rain of the storm outside were suddenly silent. The surface of the sphere was a transparent, slightly cloudy, membrane that marked the boundary of the time dislocation that had spread from the time crystal. To the Professor sitting inside the sphere the outside world seemed frozen in time. Even the raindrops hung like beads in the air. Nothing moved, nothing changed and the Sun would not rise. THe spaces inside and outside the sphere were universes apart; in each the laws of physics were obeyed but there could be no communication between them. Hardly believing the magnitude of his triumph the Professor turned to the portable radio he had brought with him. Normally there should be a multitude of broadcasting stations to hear. He brought the volume to maximum and tuned across the waveband. There was nothing to hear but the hiss of the radio's own circuits. The Professor laughed as he thought of how his successful experiment would be his triumph over his sceptical peers and not least an article that Wikididdlypedia would not dare refuse. But wait, could there be an Internet

Vernor Vinge's novels "The Peace War" and "Marooned in Real Time" are written around the notion of a gadget that makes spherical fields for which time stops inside. That includes stuff like air molecules and in those stories the OP's question is resolved by the observation that inside the field, nothing moves. 70.90.174.101 (talk) 04:25, 15 September 2009 (UTC)

For a taste of a world where people take Donald Duck physics literally, here is a thread where people debate with great sincerity how God managed to put a time-freeze on the Sun that one time. --Sean 08:26, 15 September 2009 (UTC)

Mosquitoes

Hey there! Would like to know what role do mosquitoes play in the food web.If anyone could help me out.Thanks. --Lightfreak (talk) 19:55, 13 September 2009 (UTC)

Mosquitoes eat nectar, etc. and occasionally blood. They are eaten by the various things mentioned here. --Tango (talk) 20:03, 13 September 2009 (UTC)

Insects in general are an important part of the food chain. Baseball Bugs ^{What's up, Doc?} carrots 20:11, 13 September 2009 (UTC)

Mosquito larvae are a very important food source for some types of fish, especially trout. That's the only important role I know. Looie496 (talk) 23:52, 13 September 2009 (UTC)

A citation is needed for that. Mosquito larvae are predominantly found in stagnant or still water, trout require moving well oxygenated water. Trout eat various insects and their larvae found in cold-water environments. 86.4.181.14 (talk) 06:18, 14 September 2009 (UTC)

Mosquito larvae indeed are one of the most important links in the aquatic food chain. They consume microscopic algae (and generally all sorts of microscopic gunk present in the water) and are consumed by fish, aquatic invertebrates, and some wading birds. Adult mosquitoes are consumed by predatory insects (mostly by dragonflies AFAIK), spiders, birds, etc., but the larvae are indeed more abundant and more important in the food-chain. Adult mosquitoes are also important pollinators and important disease vectors. They also play a significant role in the biomagnification of pollutants and pesticides. --Dr Dima (talk) 01:29, 14 September 2009 (UTC)

Regarding the trout (freshwater salmonids): the young are insectivorous but the older, larger trout feed mostly on fish. I would suspect that young trout are far more likely to feed on midge larvae than on mosquito larvae, for the reasons 86.4.181.14 has noted. --Dr Dima (talk) 07:18, 14 September 2009 (UTC)

I've done a little search and it looks like young trout actually feed both on midge larvae directly and on the larger insects that feed on midge larvae, so that introduction of trout or increase in trout population does not necessarily reduce the midge larva abundance :) --Dr Dima (talk) 07:30, 14 September 2009 (UTC)

But this is their significance in forest and wild life.Actually, I was looking for domestic ones. Thanks still.--Lightfreak (talk) 18:45, 14 September 2009 (UTC)

To the best of my knowledge mosquitoes have never been successfully domesticated ;) . A "domestic mosquito" is a mosquito, any species belonging to family Culicidae such where adult females feed on blood. Not to be confused with midges (Chironomidae, Chaoboridae, etc.), as explained above. --Dr Dima (talk) 01:59, 15 September 2009 (UTC)

accuracy and precision

what is the difference between accuracy and precision? arent they both basically the same thing? —Preceding unsigned comment added by 174.6.144.211 (talk) 23:57, 13 September 2009 (UTC)

Nope. See Accuracy and precision. --Tagishsimon (talk) 23:59, 13 September 2009 (UTC)

If you have a robot and you tell it to drive 3 meters forwards and it ends up at 3.03 meters because (say) it's wheels are a bit bigger than they should be - then that's a problem of accuracy. If you repeat the experiment ten times and if it ALWAYS goes 3.03 meters - then that's amazingly good precision. If sometimes it goes 3.02 meters, sometimes 3.01 meters, sometimes 3.04 meters because the wheels sometimes slip on odd rocks and pebbles along the way - then that's not so good precision. Generally, issues of poor accuracy can be compensated for - in this case, we could program the computer to always drive 1% less distance than we ask it to - and it would then be pretty much spot on. But the lack of precision is hard to engineer out. SteveBaker (talk) 01:07, 14 September 2009 (UTC)

1% --Tagishsimon (talk) 01:10, 14 September 2009 (UTC)

1 percent, actually. And the question of "calibration" would seem to come into it also. Baseball Bugs ^{What's up, Doc?} carrots 01:11, 14 September 2009 (UTC)

Jeez - you guys are too quick off the mark! I couldn't fix it because of the edit conflicts! SteveBaker (talk) 01:15, 14 September 2009 (UTC)

Complicating matters is that 1 percent off would leave you at 3.03 - .0303 = 2.9997. Depending on the precision (or is it accuracy?) of your measuring tools and how much accuracy (or precision?) you're looking for. If you want 3.0300 - x = 3.0000, then x = .0300. Then the multiplier is more like .00990009... instead of .01. Baseball Bugs ^{What's up, Doc?} carrots 01:56, 14 September 2009 (UTC)

How exactly does this complicated effort to prove your mental superiority over the rest of us help the OP through the discussion of accuracy and precision? Meanwhile - may I suggest you consider reading significant figures and perhaps you would note my careful use of the phrase "pretty much spot on" rather than "exactly correct". K'thanks. SteveBaker (talk) 03:04, 14 September 2009 (UTC)

I've never been so insulted. But it's early yet. Baseball Bugs ^{What's up, Doc?} carrots 07:23, 14 September 2009 (UTC)

These same terms were used regularly when I went to rifle school. Accuracy is your ability to hit the bullseye. Precision is how close each shot is to the previous shot. If you put 10 shots right on the same spot, but it is not in the bullseye, you have high precision and bad accuracy. If you get all shots in the bullseye, but they are all over the place inside of it, you have high accuracy but bad precision. -- kainaw™ 03:14, 14 September 2009 (UTC)

This also gives another example of the point above SB was making. If you get 10 shots right on the same spot every time say 5 centimetres to the left of the bulls eyes, you just have to learn to aim for 5 centimetres to the right of the bulls eye. If your shots are all over the place, you can't easily improve that other then to practice more Nil Einne (talk) 11:39, 14 September 2009 (UTC)

What you're calling "precision" is more like "consistency". A pitcher learns the mechanics that will make the ball go where he wants it to go. But consistency isn't everything. I once heard a comment about a pitcher, I forget which one, that "he would have been a Hall of Famer if the strike zone were high and outside." Baseball Bugs ^{What's up, Doc?} carrots 15:53, 14 September 2009 (UTC)

Yes - precision is indeed more like consistency. So if this pitcher could have been pursuaded to aim low and inside - he'd be a household name and you wouldn't have forgotten the poor fellow already? SteveBaker (talk) 16:58, 14 September 2009 (UTC)

September 14

Identify string in my foot

during my weekly martial arts practice (white belt), I noticed that I feel some sort of string (probably a ligament) being tensed/stretched whenever I shift my weight and land on one of my feet. Could you identify that string? I think it's between the Calcaneus and the metatarsus. Why do multi-classing nerd/jock is so difficult in real life.--121.54.2.188 (talk) 01:35, 14 September 2009 (UTC)

We cannot give medical advice. Please see a doctor. Baseball Bugs ^{What's up, Doc?} carrots 01:48, 14 September 2009 (UTC)

I don't really see this as a medical question since no problem has been described -- the big "string" down there is the plantar fascia. If you mean something else, the picture in that article might help you. Looie496 (talk) 01:58, 14 September 2009 (UTC)

I wasn't soliciting any medical advice, rather, I was seeking anatomy advice. It seems that you'll discover new muscle groups every time you practice (and they also hurt afterward to remind you that they exist:)). Thanks Looie, though it seems to be thicker than I thought. Maybe it's one of those digital slips attached to it.--121.54.2.188 (talk) 02:23, 14 September 2009 (UTC)

Possibly the peroneus longus tendon. Axl ¤ [Talk] 09:37, 19 September 2009 (UTC)

Can you strain your tongue?

Is it possible to strain your tongue muscle the same way you can with other muscles? Are there any muscles that can't be strained/pulled? Spiderone 07:29, 14 September 2009 (UTC)

In principle, I don't see why not, but given it's only "attached" on one end I'll venture that it's very unlikely to happen by accident.--Leon (talk) 08:44, 14 September 2009 (UTC)

I don't know about you, Leon, but my arms and legs are all attached at only one end (I wouldn't enjoy looking like a pretzel), and I strain them quite often. --KageTora - (영호 (影虎)) (talk) 16:42, 15 September 2009 (UTC)

Absolutely. I've done it. --Pykk (talk) 09:36, 14 September 2009 (UTC)

Really? OK I won't ask how. Spiderone 12:43, 14 September 2009 (UTC)

Sounds like a job for the cunning linguists at WP:RD/L! I don't know if that's exactly the same kind of strain, but it certainly happens, and was even memorialized in an episode of Seinfeld, IIRC. Matt Deres (talk) 16:17, 14 September 2009 (UTC)

So, entendre aside, it's at least as plausible as dying from licking envelopes. ~ Amory (user • talk • contribs) 17:20, 14 September 2009 (UTC)

Licking envelopes can be harmful to ones health Googlemeister (talk) 18:09, 14 September 2009 (UTC)

"Are there any muscles that can't be strained/pulled?" - The brain is apparently a muscle, and I've never heard of anyone straining or pulling it, except metaphorically. No. --KageTora - (영호 (影虎)) (talk) 17:02, 15 September 2009 (UTC)

I'd like to pursue KageTora's comment, "my arms and legs are all attached at only one end, and I strain them quite often"

My intuitive reaction would be that at the time you strained a muscle in your arm/leg, both ends were probably quite firmly attached to something you were lifting, pressing against, or in some other manner immobile -- not just flapping around loosely like a tongue.

True? --DaHorsesMouth (talk) 23:23, 15 September 2009 (UTC)

Not exactly. I don't usually lift things with my legs, yet there have been times when I have pulled a muscle somewhere in them whilst running, for example. --KageTora - (영호 (影虎)) (talk) 23:43, 15 September 2009 (UTC)

DaHorsesMouth was generalizing and being evidently gave an oversimplified answer seeing how specific you are being. When both bones to which a muscle is attached (origin + insertion, such as the trapezius being attached to both the occipital bone of the cranium and the scapula) move farther apart in relation to each other at the same time that very muscle is being contracted (such as during a car crash, as in our trapezius example), the muscle will be strained. Because the genioglossus and hyoglossus and styloglossus, the three muscles that, when combined, compose the majority of the tongue by both mass and volume, are attached to only one bone (genial tubercles of the mandible, hyoid and styloid process, respectively) they effectively cannot contract against resistance to result in a strain. DRosenbach ^{(Talk | Contribs)} 02:05, 16 September 2009 (UTC)

Good fair bit of information, there, thanks. However, I feel I can point out that it is, however, possible to strain one's tongue when the tongue is contorted into an unnatural position, such as during an seizure. Sorry, I don't want to sound like I am being argumentative, but I think I may be misunderstood as such, so I'll just keep my eye on this thread and only add anything if I think I can (and with citations if possible). --KageTora - (영호 (影虎)) (talk) 09:03, 16 September 2009 (UTC)

If a strain is defined as both micro- and macrotearing of a muscle due to overstretching, I would say that tongues would not necessarily fall outside the realm of "strainable" muscle tissue insofar as one can probably find a situation/method in/by which to overstretch the tongue and produce said tearing. Forcible overstretching of the tongue is definitely a possibility, such as securing the tongue in a particular fashion to prevent the securing medium from tearing through the tongue upon pulling, and then pulling. In physiologic use of the tongue, pain sensation kicks in well before the maximum stretching is reached (just like pain sensation will kick in well before any muscle nears its maximum stretched length) but, as stated earlier, a rapid, perhaps passive (as in an injury, where the pull happens rather than being performed) pull on attached bones can tear a contracting muscle. When I stick my tongue out as far as I can (as I do now as I type), my tongue begins to hurt. I don't think it will tear if I keep pushing it out because I can't exceed its natural length without tugging on it with a second attachment. DRosenbach ^{(Talk | Contribs)} 13:04, 16 September 2009 (UTC)

Fields

Whether earth has got a negative or positive field around it? —Preceding unsigned comment added by 202.164.157.168 (talk) 16:04, 14 September 2009 (UTC)

What kind of field? One with daisies in it? Fences&Windows 17:05, 14 September 2009 (UTC)

The commonest cloud-to-ground lightning is believed to be initiated by a negative-to-positive respectively field. Various theories about how the field arises are described in Lightning.Cuddlyable3 (talk) 19:42, 14 September 2009 (UTC)

But that's cloud-to-ground lightening. Ground-to-cloud lightening is also possible. DRosenbach ^{(Talk | Contribs)} 00:09, 15 September 2009 (UTC)

In case he meant something else, the outer Van Allen radiation belt is composed of positive ions, meaning that the earth, at the outermost levels, has a positive electric field around it; this has nothing at all to do with lightning being that the Van Allen belts are about 20,000 kilometers out... --Jayron32 21:54, 14 September 2009 (UTC)

Someone with a subscription might be able to tell us something about the total net charge from this paper: Discussion on the Earth's net electric charge doi:10.1007/BF01054576. However, the paper (from 1988) says it's a difficult question to answer. AlmostReadytoFly (talk) 13:35, 15 September 2009 (UTC)

Is a 12 gauge sabot shotgun round traceable?

I was wondering because of the plastic brace. —Preceding unsigned comment added by HitmanNumber86 (talk • contribs) 16:22, 14 September 2009 (UTC)

The sabot drops away from the shot during flight before reaching the target. Presumably the used sabot pieces can be traced somewhere on the ground afterwards but the real trace of the sabot's use is the concentrated pattern of shot on the target. Cuddlyable3 (talk) 19:50, 14 September 2009 (UTC)

I think the question is can you trace the shells to an individual gun, like you would with, say, a bullet, not whether a sabot was used or not. I imagine if you can get parts of the sabot, you can trace that to an individual gun (grooves and all that), though I am just speculating. --98.217.14.211 (talk) 19:58, 14 September 2009 (UTC)

The braces on Sabot are made of plastic, not lead or copper. I don't think the pattern would be reproducible on a shotgun. —Preceding unsigned comment added by HitmanNumber86 (talk • contribs) 20:10, 14 September 2009 (UTC)

Most shotgun barrels are not rifled. 75.41.110.200 (talk) 03:20, 15 September 2009 (UTC)

Electric fences for cattle and horses: dangerous to humans?

Recently while walking in the english countryside I found the public footpath blocked by an electric fence wire, and had to wriggle commando-style underneath it. Just how dangerous are such electric fences to humans - they are designed to deter cows or horses, which are a lot bigger than us. And if you touched it, what would happen - would it be like a tazer perhaps? 78.146.163.118 (talk) 17:00, 14 September 2009 (UTC)

It's a quick shock, and it will catch you off guard. I touched one nailed to the other side of a wooden fence. I assume it charges a capacitor, it took a second for me to realize what happened. It doesn't hurt. --HitmanNumber86 (talk) 17:14, 14 September 2009 (UTC)

Hitman is right, it's not so bad, just very jolting (har har). Nobody wants to injure their herds, so the fences are designed to be just unpleasant enough to deter. I've used electric fences while backpacking to deter bears from food; the idea is you surround your food stuffs, etc. with a fence, and wandering bears get shocked while sniffing around. As might be expected with a bunch of bored males, we all took turns grabbing the fence, seeing who could hold on the longest. Nobody got hurt, just a little frazzled. ~ Amory (user • talk • contribs) 17:25, 14 September 2009 (UTC)

the longer the electric wire, the lower the shock. Also, if you are standing in mud or water, your shock will be significantly greater. Googlemeister (talk) 18:07, 14 September 2009 (UTC)

We have an electric fence article with some details about various pulse patterns. Googlemeister, why does the length of a conductor affect how much of a shock you get from touching it, and do you specifically mean the whole fence length or "from supply to point of contact" only? DMacks (talk) 20:00, 14 September 2009 (UTC)

Entire fence length. Personal experience, the same device produced a very mild shock when used on a 2.5 mile perimeter fence, and a very strong shock when used on a 150 yard perimeter fence. Additional OR, standing on a tire does not prevent the shock. Googlemeister (talk) 20:15, 14 September 2009 (UTC)

The current has to go down the line, through you, and then back to the grounding rod, which is often back by the charger. If that's a long way or the ground is dry, the resistance will be higher and the current lower. Also, there are usually weeds and things touching the fence which sap the current, so the longer the line the more there are. As an aside, I had to rush out from a dinner party this evening because my 6 pigs had decided to ignore the electric fence and go on walkabout. --Sean 08:42, 15 September 2009 (UTC)

Voltage drop. AlmostReadytoFly (talk) 13:29, 15 September 2009 (UTC)

As an aside, what would actually happen if you were to urinate on an electric fence? In one of Bam Margera's pre-Jackass videos, one of his buddies pees on an EF to test out the old folk adage that suggests that it is not a good idea to do this - and is apparently in great pain afterwards. However, I am aware to the possibility that this may have been staged or exaggerated for comedy purposes. --Kurt Shaped Box (talk) 20:11, 14 September 2009 (UTC)

MythBusters did it. I don't know the result. Googlemeister, Brainiac: Science Abuse prevented shock from a fence by getting participants to stand on styrofoam. —Preceding unsigned comment added by Vimescarrot (talk • contribs) 20:21, 14 September 2009 (UTC)

Mythbusters comprehensively busted it - proving that it's impossible to create a constant stream of urine - it always breaks up into droplets so there is no constant path for the current to follow. SteveBaker (talk) 20:36, 14 September 2009 (UTC)

Hmmmm. Not even if you hold your dick about two inches from the wire (as seen on the aforementioned vid)? Did they test that? --Kurt Shaped Box (talk) 20:57, 14 September 2009 (UTC)

I believe they busted it with peeing on an electrified third rail. They showed it is possible if you kneel down and have a really huge... yeah. Anyway, If you pee on an electric fence, you could pee on the part right in front of you, so the urine wouldn't fall as far, and thus would move slower and be less spread out. — DanielLC 03:48, 16 September 2009 (UTC)

A factor that makes these fences *much* less dangerous than one you might put around your average concentration camp is that they only give a short pulse about once or twice per second. That gives you the ability to let go, which you might not otherwise be able to do. The bottom line is that nobody's trying to impose the death penalty on their livestock for thinking about leaving home. --Sean 08:45, 15 September 2009 (UTC)

There is leakage of current through all the insulators, so a longer fence run has more parallel leakage paths to drain of the electricity besides through the person touching it. The voltage drop through a long wire would be more of a factor the larger the current flow, but the idea of a fence charger is to have a high voltage and a small current,to startle and inflict pain unlike prison camps in movies which have electric fences intended to electrocute escapees. If one fence insulator has a resistance of, say 50 megohms to ground, then 10 would have a combined resistance of 5 megohms (the leakages would be in parallel). If your resistance (including dry boots) was .5 megohm, then the leakage through the fence would be a small factor and you would get a pretty good jolt. If there were 100 insulators on a long fence, the leakage resistance would have a combined resistance of .5 megohm, the same as yours (hypothetically) and half the jolt would go through the fence leakage to ground. One cannot rule out some idiot wiring a fence to the power mains, so treat anything electrical with caution. Edison (talk) 14:31, 15 September 2009 (UTC)

If the shock does not hurt, then how does it deter large animals? 78.147.99.119 (talk) 19:18, 15 September 2009 (UTC)

Something does not have to hurt to be unpleasant. Your muscles involuntarily clenching is not all that fun even if it does not hurt in a traditional sense. Googlemeister (talk) 21:13, 15 September 2009 (UTC)

It definitely hurts - but it's brief and does no lasting damage. You could push the fence down if you were even moderately determined...and so can cows. The fact is that they are trained to avoid these fences - so the issue rarely comes up. My great uncle used to turn off his fences to save electricity - and the cows still wouldn't touch them. SteveBaker (talk) 21:22, 15 September 2009 (UTC)

Anecdote: we tried growing sorghum in our area in the '70's. Not sure if it's what this wiki calls sorghum, it looks like corn but grows faster and no ears of corn. Cows love it and it was great fodder. Our mistake was to plant it next to a pasture enclosed by an electric fence. It just tasted too good, and the fence meant nothing to the cows. So we cut down anything within a cow-reach of the fence - too late though, we'd provided a positive stimulus and nothing we could do would stop them anymore, except evacuate the pasture. Rounding up animals through 8-foot-high crops - ahh, good times! :) Franamax (talk) 21:54, 15 September 2009 (UTC)

This is actually a classic example of conditioning. Skinner even mentions it in Walden 2 with sheep—teach them it is electric a few times, and you don't have to have it turned on ever again. I imagine in practice there would need to be some occasional reinforcement (much less adaption for the fact that the herd changes over time). --98.217.14.211 (talk) 00:14, 16 September 2009 (UTC)

(e/c with SB, who says much the same more briefly :) The other factor is that for any animal, large or small, a completely unexpected experience in what had seemed like a familiar environment enforces an aversive response, i.e. they just never try it again. Especially with cows (and pigs), exploring is often done with the nose, which is especially sensitive, so they learn the lesson very quickly. I'm a large animal, and I learned very quickly to not touch an electric fence ('tho I learned that you can use a piece of grass to explore the pulse gradually, you need these techniques to find out whether the fence is really working). In fact, once all the cows have sniffed the fence once, you don't actually need to power it anymore, fence controllers with dead batteries aren't all that uncommon.

And I would indeed say it hurts! The first time, it feels like the end of the world. This is especially true of those fencers, usually AC plugged in at the barn as opposed to DC-battery remote fencers, which I believe sense the voltage at the "other end" and boost their output to overcome line-loss due to grounding. The mild experiences I've seen reported above are perhaps the result of touching battery-powerd fences. For a good AC-powered fence, you're getting into bee-sting territory, but without the swelling.

Also I've never seen an electric fence used to confine horses, in my experience there is way too much risk that they will surge forward in panic and wreck the fence. Horses can often act in counter-intuitive ways... Franamax (talk) 21:34, 15 September 2009 (UTC)

Electric fences are often used to confine horses, actually. You can use them inside another more substantial fencing, such as inside a hedge or a post-and-rail paddock fence (for example) to give additional security, or on their own to fence off parts of a field for strip grazing. Horses can be quite clever though. They can often sense when a fence isn't on and take advantage. One pony I know realised that when he was wearing his rug, it didn't hurt and he ducked underneath it. Serraching for equine electric fencing will give lots of examples.

Slightly off-topic, but electric fences don't have to be designed to deter large mammals – see "Battery Brainwave" at http://www.newscientist.com/article/mg18625051.800-feedback.html for one aimed at slugs and snails. Delightful. Adrian J. Hunter^{(talk•contribs)} 07:03, 17 September 2009 (UTC)

significant variation in the number of genes between homologous chromosomes

So ... I'd like to prove one of my professors wrong. I envision that it is quite frequent (like say 1/30, 1/50, etc.) for an individual to have homologous chromosomes with differing number of genes. (And by genes, I mean coding regions -- so if I have an extra copy of the same gene, that counts as an extra gene.) So let's say one homologous chromosome would have 1402 genes, and another would have 1403. I'm looking for situations like that (and these situations come about through gene flow).

Such variable frequency must be quite common -- the allele frequency can be kinda low (like 0.5-5%) so I'll get my points back, but not ridiculously low. (Higher frequency the better.) In this case, it would be like having one gene to no gene at all (so effectively the extra gene would be sort of X/0, but this is on an autosome). a Can anybody give me some examples? John Riemann Soong (talk) 18:02, 14 September 2009 (UTC)

The number of HLA-DR beta genes varies among alleles, as outlined in our article. Another example, which I don't know for certain, but still... I'd be very surprised if every individual had the exact same number of olfactory receptors. And then there's the blood group antigen Rh(D). Rh(D) negative individuals lack the D gene (or, more rarely, have a nonfunctional one). --NorwegianBlue ^talk 20:25, 14 September 2009 (UTC)

You could probably make the point that genome-wide copy number variation (CNV) accounts for a great deal of genetic diversity between individuals. Many CNV regions are considered polymorphisms in that they are present in a significant fraction (>5%) of individuals, and some CNV regions contain genes. My favorite paper on this topic right now is here --- Medical geneticist (talk) 23:17, 14 September 2009 (UTC)

I would agree with you and suggest that the burden of proof is really on your professor. It's quite ridiculous to assert that homologous chromosomes possess the identical number of genes -- that may very well be why they are called homologous and not identical. As homologous chromosomes derive from each parent, I think an example to be shown is not when there would be a different number of genes, but rather an instance of the same number of genes (that's what I meant by switching the burden of proof). Genetic variation is not only quality of alleles but also quantity of alleles (as in co-dominance/epistasis) -- in a sense, quantity translates (pun not intended) into a difference in quality. DRosenbach ^{(Talk | Contribs)} 00:07, 15 September 2009 (UTC)

Hmm -- that being said, I don't know if it would be significant -- depends on your definition. Quantitatively significant it might not be. DRosenbach ^{(Talk | Contribs)} 00:12, 15 September 2009 (UTC)

Let's not throw out the basic fundamentals of genetics just yet, ok? I think it is still safe to assume that the majority of genes follow the "one copy from each parent" pattern and that two copies is the general rule... not to mention the most correct answer on a test. Of course, as indicated above, there are exceptions to that rule (which is part of what makes genetics so interesting) but for the purposes of teaching fundamentals of genetics lets stick to the rules. The OP's Prof may have been a bit too dogmatic in his/her teaching, but that might have been totally appropriate for the level of the course. --- Medical geneticist (talk) 14:00, 15 September 2009 (UTC)

If the gene in question is subject to inhibition at either the transcription or translation levels, or the gene product is subject to a neutralization pathway - any of which are regulated by concentration of the gene product - then isn't the CN immaterial? Concentration-dependent inhibition is inhibition and reaches equlibrium. Yes, that may be beyond the scope of what the prof is trying to teach, just asking for my own benefit. Franamax (talk) 22:40, 15 September 2009 (UTC)

bird acrobatics

Small birds seem extremely good at flying around and not running into things (besides windows and cars) because they are incredibly nimble in flight. What kind of acceleration do these small birds reach, as human fighter pilots can hit 8-9Gs on much larger turns. Googlemeister (talk) 20:23, 14 September 2009 (UTC)

Apparently, A = v2 / r ... if we consider the airspeed of an unladen swallow as 11 metres per second, and postulate a turn with radius 1 metre, the acceleration will be 121m/s^2, which (divide by 9.8 m/s^2) is about 12g. However I'm not sure what the minimum radius of turn would be for such a speed, but this gives you a ballpark estimate. Double the radius and you halve the g force. --Tagishsimon (talk) 23:35, 14 September 2009 (UTC)

An African or European swallow? :-) --Phil Holmes (talk) 09:00, 15 September 2009 (UTC)

The Spine-tailed Swift is the fastest bird in level flight - 105mph or so (47 meters per second). A Peregrine Falcon can hit 175 mph (78 meters per second) - in a steep dive. But I'm pretty sure that neither of them can turn sharply at that speed. I'm kinda skeptical that a swallow could do it at 11 meters per second either. I've had an occasional small bird get stuck inside my garage - and they are definitely struggling to turn within a 20' wide garage at anything much faster than their stall speed. However, birds should be pretty good at withstanding g-forces. The strength of muscles and tendons depends on their cross-sectional area which increases as the square of the size of the animal - but the mass of the animal increases as the cube of the size. Because the actual force they have to resist is mass times acceleration, their small mass and proportionately thicker muscles and tendons should mean that smaller animals are much stronger, pound for pound than larger animals. Add to that that birds are highly evolved for minimum weight and you start to understand why a bird should be easily able of withstanding accelerations that would squish a human. SteveBaker (talk) 02:05, 15 September 2009 (UTC)

Speaking from personal experience here - and it's difficult to gauge the speed when they're flying in a living room or the confines of a small aviary, Budgerigars seem to be able to turn (but not quite literally) on a sixpence. --Kurt Shaped Box (talk) 08:03, 15 September 2009 (UTC)

This page claims that a Peregrine Falcon hits about 25 G pulling out of its dive. (Of course, that's in a different axis than turning in circle.) -- Coneslayer (talk) 14:13, 15 September 2009 (UTC)

G-related: here is an interesting article on how woodpeckers manage to survive 1200 G decelerations as they beat their heads against the wall. --Sean 08:53, 15 September 2009 (UTC)

Wood has a bit of 'give' in it. I wonder what happens to the brains and skulls of those confused woodpeckers which earnestly attempt to hammer metal poles? --Kurt Shaped Box (talk) 17:57, 15 September 2009 (UTC)

The linked article describes high-speed photography footage showing that they give a few test taps before hitting the gas. --Sean 21:09, 15 September 2009 (UTC)

These don't look like test taps to me. The woodpecker seems to be all 'WTF?' after each drilling attempt. --Kurt Shaped Box (talk) 00:35, 17 September 2009 (UTC)

Anicent plotting of landmass

We have a GPS can track the position of the plates is moving, then we should know the plates plate is moving. Is GPS tracking the plates from 5 years ago and now using magnifying glass the way we tell the positions of plates moving? For the places and exact lattitude of continents, could it be a mistake saying is 100 million years ago, tip of South Africa was 60 South? Could plotting the plates long time ago make a error bar?--209.129.85.4 (talk) 21:12, 14 September 2009 (UTC)

You idea is correct, GPS is used to track the movement of land masses. Over large time scales you have to assume that the rate of movement can be predicted to be the same as now. This will not precisely be the case, and other techniques can be used, such as dating the ocean floor, by looking at magnetic anomaly stripes, or preserved direction of magnetic particles in rocks of that age. Graeme Bartlett (talk) 21:54, 14 September 2009 (UTC)

Well, you can't really use a standard GPS unit - they only have an accuracy of around 10 feet (at best). Even an actively slipping fault like the San Andreas is only moving about an inch a year - so you'd have to wait at least 120 years before your GPS would be reliably indicating the motion. It is possible to use GPS - but you need some kind of a 'base station' in addition to the satellites. With that, you can get precisions down to a few inches - but you'd still need a few years worth of observations to see anything happening. SteveBaker (talk) 01:47, 15 September 2009 (UTC)

Of course the accuracy figure for the standard GPS unit refers to the accuracy of a single reading (once all satellites are acquired, plus WAAS etc). I would think, that if you left the GPS receiver in a single spot and averaged the lat/long figures over, say, a 24-hour period, you should be able to do considerably better, because fluctuations would average out. What the maximum improvement factor is, though, I couldn't say. --Trovatore (talk) 03:33, 15 September 2009 (UTC)

Steve is referring to differential GPS and it is indeed used for that purpose. 70.90.174.101 (talk) 04:21, 15 September 2009 (UTC)

Our GPS article has a careful breakdown of the causes of error. SteveBaker (talk) 21:16, 15 September 2009 (UTC)

As for monitoring stuff like faults they use other sensors (besides GPS), such as laser based instruments. I'm thinking they also use them to monitor volcanoes. 66.133.196.152 (talk) 09:27, 16 September 2009 (UTC)

Afterimage to work

How come when I try to look at green object I've try this few times for 60 second I count in my mind the white is still white green is still green. How long should I hold one color like blue to see blue color wear out? Will 5 minutes work? Usually when i look things for two minutes the afterimage is still the same.--209.129.85.4 (talk) 21:14, 14 September 2009 (UTC)

That's odd...are you sure? Usually, when people stare for even 30 seconds at some brightly colored image - then glance quickly over to an all-white surface, the after-images are in the reverse color of the original. So if you were staring at something green, then the after image should be magenta (a kind of purpleish-pink). If you stare at something red, the after-image is cyan (greenish-blue) - and if you stare at blue, the after image should be yellow. SteveBaker (talk) 22:27, 14 September 2009 (UTC)

yes, I'm positive no kidding. I've try look at computer screen is blue i concentrate on it for 60 minutes, blue is still blue, white is still white. i've try looking at someting lime green for 60 seconds lime green stays lime green white stays white. Do I have to look the color closely and take them close exactly at my eye, or I can look few inches away to do this lab right?--209.129.85.4 (talk) 21:35, 15 September 2009 (UTC)

Here's a commonly-cited one that uses the U.S. flag and doesn't even require you to look away - just stare at for a minute or so, click on it, the reverse-colored flag disappears in favor of a white surface, and thus the proper-colored flag will appear as an afterimage.[7] Baseball Bugs ^{What's up, Doc?} carrots 23:34, 14 September 2009 (UTC)

Fatigue colors ? Aha no article!--79.75.88.222 (talk) 01:01, 15 September 2009 (UTC)

Maybe its called Retinal fatigue ? Oh dear no article again!--79.75.88.222 (talk) 01:08, 15 September 2009 (UTC)

Try something simpler! Afterimage, Neural adaptation, Afterimage on empty shape. SteveBaker (talk) 01:35, 15 September 2009 (UTC)

It may seem obvious, but make sure you keep your eyes fixed on one exact spot. like a fixation dot in one of the classic afterimage samples, like the American flag. Then look at a white surface to see the complementary colors appear. Edison (talk) 14:17, 15 September 2009 (UTC)

Walking v. jogging for fitness

Is it possible to say that X minutes of walking are equivalent to Y minutes of jogging from a fitness point of view? Or similarly for distances? For example, might walking for 60 minutes increase your fitness as much as 10 minutes of jogging? 89.243.184.30 (talk) 21:58, 14 September 2009 (UTC)

Well I think it's going to vary immensely from person to person, depending on their speed, their gait etc, and what you mean by "fitness". If it's calories you're concerned about, most calculators you find seem to hold distance as most important, and modify it somewhat based on speed. This one for instance will let you do either, if you use the distance one and then your speed for the same distance you'll get slightly different answers. It seems to assume if you go faster you burn less calories per mile than if you go slow. As far as increasing your fitness, I'd say running, and specifically holding your heartrate up for a significant amount of time, is likely to be more effective that walking a similar distance. If you're training for a race or something, obviously running is going to be more effective preparation than walking. I find walking to be more boring than running, since you cover less ground in the same time, but I'm sure others would disagree. TastyCakes (talk) 22:11, 14 September 2009 (UTC)

The point about "what you mean by fitness" is very important. My personal prejudice is that running is damaging, at least for me. My joints don't seem to stand up well to it. So if you improve your cardiovascular fitness, but set yourself up for arthritis, what's the net effect on your fitness?

It would be a tough choice, but luckily you don't have to make it — there are lots of cardio options besides running. I'd look into swimming, cycling, or (deadly dull but terribly convenient) elliptical trainers at the gym. Caveat: These are my own personal prejudices; I have no real training and no professional qualifications in this area. --Trovatore (talk) 22:20, 14 September 2009 (UTC)

I go in for dancing instead, I walk to the shops rather than using the car but it only takes about twenty minutes. As a poster pointed out in a previous question if you don't find exercise interesting you may make an overall loss in worthwhile life. With a sociable exercise it is an overall gain, and dance or martial arts are good for exercising the mind as well as the body. If you like walking try joining a walking club, and if you like running you can go in for training for a marathon, but just walking or jogging for exercise?, I can't see the point. Dmcq (talk) 07:55, 15 September 2009 (UTC)

Tai chi chuan and Physical fitness also have sections on fitness as meaning more than replacing fat with muscles. Dmcq (talk)

Walking is certainly better than not walking, but it's unlikely that most walkers elevate their heart-rate enough to have significant cardiac benefits. Running is excellent exercise, but if you're heavy or particularly out of shape, or if you have the wrong shoes or a weird gate then, as Trovatore points out, it can be injurious. Swimming is fantastic exercise, although beginning/returning swimmers overestimate how much effort they're putting in, because they mistake being out of breath due to poor breathing technique to being out of breath due to exertion. For the gym, the elliptical trainer Trovatore mentioned is good exercise (I read Scientific American on it to alleviate the boredom - I find I get about 10% more performance than if I actually concentrate on the exercise), as is the static bike (although beware of knee-side pain, particularly if you are a woman - talk to the gym staff if this proves uncomfortable). And don't discount the gym rowing machine, which is good cardio and uses a wider range of muscles than bike/run/elliptical. -- Finlay McWalter • Talk 09:28, 15 September 2009 (UTC)

I've also seen it said that one ought to do a certain amount of "impact" exercise such as running or woodchopping because it increases bone density and strengthens connective tissue. Running too much certainly causes problems, but I think a modest amount of running is likely to be beneficial. Looie496 (talk) 23:35, 15 September 2009 (UTC)

I can no longer resist and must point out the alternative of playing squash. I've heard (unsourced) rumours that it is the sport with the lowest injury rate and highest cardio expenditure. It's also much more of a fun challenge than tackling an exercise machine. It combines athletic ability with tactics and realization of your own limitations, with an impact limited only by your own expectations of yourself. In a good club, you will always find someone else who plays at your own level. The drawbacks are: according to our article, possible heart attack; from my own experience as a tobacco smoker (inter alia), occasional doubling-over with coughing; again from my own experience, your opponent may run into the wall returning a shot and crack a rib (Bob still doesn't think that was funny! :); and if you possess any sort of massive ego, be ready to get beat by someone you were sure wouldn't be a problem. Also, I've noted that some heavier players complain of knee problems, but I've noted that those people were "heavy-landers", whereas many other players more weighty than myself had good "spring" on their landings and could beat me regularly. They were the ones thinking ahead of the current shot.

All-in-all, as a way to get a good workout, keep up your interest, socialize, and find your peer group in your interest in health - by my lights, it's squash all the way! :) Franamax (talk) 23:39, 15 September 2009 (UTC)

September 15

Integrins and signal transduction

It seems to me to be overkill for there to be tensile/contractile sensation in the form of integrins on the surface of cells that subsequently induce signal transduction. Why do proteins need to be made to order with immediate initiation of RNA transcription just because the chondrocytes in my nose get pushed a little when I scratch my nose. I suppose my question may derive from an oversimplification of this process as it was explained to me. DRosenbach ^{(Talk | Contribs)} 00:00, 15 September 2009 (UTC)

Grapes undissolvable?

I was holding a grape in my mouth for what seemed like ages, wondering when it would dissolve entirely by action of the saliva. Nothing seemed to change, except it was a very warm grape when I gave up and bit into it. Are grapes undissolvable by human saliva alone? Is it the skin perhaps?--The Ninth Bright Shiner 01:11, 15 September 2009 (UTC)

I can't see it dissolving at all. Chewing is an extremely important part of the process of breaking it down, it then gets broken down further by acids and enzymes in the mouth, stomach and intestines. Food doesn't really dissolve until it reaches the intestines and gets from there into the blood - until it is in the blood, it isn't dissolved (I'm not sure how dissolved it is then, it might just be suspended). --Tango (talk) 01:18, 15 September 2009 (UTC)

I'm pretty sure that the enzymes in your mouth are only there to break down starches into sugar. Other than that, it's really only things that'll dissolve in water. Since the skin of the grape is waterproof (Grapes on the vine don't dissolve when it rains!) - and they evidently aren't mostly made of starch - they will indeed just sit there until you bite into them. SteveBaker (talk) 01:32, 15 September 2009 (UTC)

Ah, that's nice. Occasionally when I'm eating a lot of something (Milk Duds at the movies, Cheez-It whenever), I'll see how long it takes to become...well, its technically not dissolved, but more like liquefied. You know what I mean. I have been defeated by grapes! But through defeat, comes wisdom...of saliva. Meh. Thanks y'all!--The Ninth Bright Shiner 02:04, 15 September 2009 (UTC)

Resolved

(ec) In addition to the fact that amylase in your saliva can only go so far, a large portion of any plant matter is made up of cellulose which can't be digested by humans at all. You need to chew in order to expose the parts that you can break down. So even without the skin a grape wouldn't dissolve in your mouth. Rckrone (talk) 02:08, 15 September 2009 (UTC)

There are enzymes other than amylase (the starch one) in saliva (see Saliva#Contents), but I think amylase is the only one there is significant quantities that is active in the mouth. --Tango (talk) 02:43, 15 September 2009 (UTC)

Fletcherizing might be the best you can do with a grape, where you chew it until it basically liquefies and slithers down your throat. An important advance in the field of nutritional psychoceramics! --Sean 08:59, 15 September 2009 (UTC)

You'll get cavities going too far into this research! Sagittarian Milky Way (talk) 16:10, 15 September 2009 (UTC)

stem cell

my sister has a cervical cancer. she has already undergone many chemotheraphy. How can stem cell help a patient with cervical cancer? —Preceding unsigned comment added by 125.212.67.220 (talk) 03:08, 15 September 2009 (UTC)

I am sorry for your sister's health trouble. Unfortunately, we at Wikipedia are not going to give any medical advice, nor should you take anything you read here, or anywhere on the Internet, as a substitute for qualified medical advice from a real physician. If you want to read a basic overview of stem cell therapy, we have an article titled Stem cell treatments, but even after reading that, you should have your sister consult her oncologist for any treatments she may receive. The doctor may be aware of some alternative/experimental treatments availible, inlcuding, perhaps, some stem cell-based treatments. --Jayron32 04:49, 15 September 2009 (UTC)

Jayron is correct; we can't possibly know all of the circumstances related to a person's medical condition or provide any advice. With regard to the question "How can stem cell help a patient with cervical cancer?" -- sometimes cancer patients are given a bone marrow transplantation or hematopoietic stem cell transplantation after receiving aggressive chemotherapy treatment. Whether this applies at all to your sister's situation is a question for her treatment team. --- Medical geneticist (talk) 13:14, 15 September 2009 (UTC)

Why are commercial culinary funnels made with pipes?

I bought a set of funnels from a shop the other day. You know, the sort of things you can put over an empty jar and pour sugar into, so that it doesn't go all over the bench. They are basically a cup with a pipe at the bottom. Then I noticed how often granules of sugar or rice or whatever get stuck in that dispensing pipe after you pour your mixture in the funnel cup. And then I thought, WHY OH WHY do you even NEED a pipe there at all, which only seems to serve the purpose of getting things stuck in it. Why not just the funnel cup with a hole at the bottom? Or if the cup needs some kind of stem to keep it stable, why not a little pole instead of a pipe? But I've never seen a funnel like this. Does anyone agree with my design critique? Myles325a (talk) 08:46, 15 September 2009 (UTC)

If you wanted to fill a bottle like a soda or ketchup bottle, your proposed device would be far inferior: you'd need one hand on the funnel while you pour, it would probably still leak some, and if it's thick stuff like ketchup you'd have to stand around holding it while it bloops down on its own schedule. --Sean 09:05, 15 September 2009 (UTC)

They do exist. I've seen them 2 feet in diameter and made out of metal for filling beer barrels, or 2 inches in diameter and made out of plastic for filling jam jars. --TammyMoet (talk) 10:22, 15 September 2009 (UTC)

The elongated end may helpful in directing the pour of liquids, as was already suggested above. Bus stop (talk) 11:25, 15 September 2009 (UTC)

In addition to stability and directing the flow, I'd also suggest that using a section of pipe would promote relatively laminar flow at the exit (the material exits as a stream} versus turbulent flow (the material spews out in all directions). A simple opening at the bottom of the receiving cup would only work if the vessel below was wide enough to contain spattering material. Franamax (talk) 22:05, 15 September 2009 (UTC)

Op myles325 back. I had thought of Sean's point to some extent. That is why I suggested that instead of a pipe you could have a short pole sticking down from the cone so that the whole contraption would be weighted down and you would NOT need to stand around holding it. The other main drawback to the current designs (and I've seen dozens of them, all sizes and shapes and they all have that damn pipe) is that as your jar fills up you have to keep raising the funnel so that the pipe is clear of the stuff you have already poured in there. That means at the end, you DO have to hold the funnel up ABOVE the jar and this means you can spill stuff. I did that the other day funneling sugar from a sugar bag into my sugar jar. The sugar was lumpy and of course it kept getting stuck in the pipe. I had to keep pressing it down and shaking the funnel. That was ok when the pipe was deep down in the jar, but as the level went up, I had to raise the funnel, and of course in no time at all, I had sugar all over my bench. That's when I had this brain wave. With my device you could easily perch the funnel on top of the jar and it would be weighed down by the rod. Also, I do take the point about the pipe encouraging laminar flows, but I think a very short pipe (only say a quarter inch) would do the job quite well. Myles325a (talk) 03:15, 16 September 2009 (UTC)

Not ALL funnels have long pipes. Jam funnels dont (see http://www.cookability.biz/hutzler-jam-funnel/b_1263.htm?SRC=GB1 for example) - you may want to try one of these for your sugar task. --Phil Holmes (talk) 13:50, 16 September 2009 (UTC)

The cause of gravity.

So, I'd like to know what the cause of gravity is. Einstein viewed gravity geometrically; as a distortion of space-time itself. But I'd like to know: Why does this happen? What causes mass to exert gravity? Or is this just a fundamental property that came with the universe?Unique and proud of it (talk) 12:39, 15 September 2009 (UTC) -Unique and proud of it. —Preceding unsigned comment added by Unique and proud of it (talk • contribs) 12:38, 15 September 2009 (UTC)

At present, "fundamental property" is as good an explanation as any. Gravity remains the only un-unified fundamental interaction not quantized under the Standard Model, and a theory of quantum gravity is one of the most highly sought-after prizes of the physics world. The linked articles can take you much further down the rabbit hole, depending on how much reading you'd like to do. — Lomn 13:01, 15 September 2009 (UTC)

The Strong interaction has yet to be unified acceptably with the Electroweak interaction; it has been quantized, though, which is presumably what you meant. Algebraist 13:31, 15 September 2009 (UTC)

Thanks, I've tried to correct/clarify the statement. — Lomn 13:54, 15 September 2009 (UTC)

I thought it had been shown that they unify at extremely high energy levels (fraction of a second after the big bang type stuff). --Tango (talk) 17:00, 15 September 2009 (UTC)

That's the electroweak interaction, per the article lead. — Lomn 18:07, 15 September 2009 (UTC)

No, I'm definitely thinking of the strong force unifying with electroweak. Looking it up, I see I'm talking about Grand unification theory, which is still a work-in-progress. I was jumping the gun a bit! --Tango (talk) 21:28, 15 September 2009 (UTC)

Because nature seems to like laws that can be described by a short formula that have complicated implications. Best I can come up with. See The Unreasonable Effectiveness of Mathematics in the Natural Sciences. Dmcq (talk) 14:30, 15 September 2009 (UTC)

Gravity and all the rest of the forces and particles in the Standard Model pop out of String theory automatically. Gravitons appear as the vibrations in closed loops in many dimensions, but string theory has a lot of holes in it. Fences&Windows 21:56, 15 September 2009 (UTC)

especially if you take all the strings and make little loops out of them...--Jayron32 02:30, 16 September 2009 (UTC)

If I could answer that question, you could just ask me why that's true. If I were able to answer that, you could ask me why that's true. At some point, there is no reason why. It's just the way the universe is. Perhaps this is that point. Perhaps string theory is that point. Nobody knows. — DanielLC 03:39, 16 September 2009 (UTC)

Thermite

How much thermite is needed to melt an inch or so hole through 1/16" thick steel? I'm using powdered rust and aluminum foil cut into small pieces. How small should the pieces be for maximum safety? What will contain that amount of thermite without cracking or hot substance leaving? I have two concrete blocks, 4" x 8" x 12", about 3 cm wall thickness, will stacking them: weight - concrete block "lid" - block #2 "reaction cavity" - 3 or 4 1/16" steel plates seperated by air spaces, or maybe just another block - kitchen sink be ok? If there are any problems with that, other possibilities I can think of are filling the blocks with dry sand, bucket of sand on the bottom (plus you get a fulgurite!), bricks. I've heard that match tip material burns hot enough to start the reaction, would that really work? Sagittarian Milky Way (talk) 16:05, 15 September 2009 (UTC)

Aluminum foil and flake rust will do nothing. If you want to make your own Thermite (and hey, they're your fingers... If you don't need them all, who am I to say anything), then you need very finely powdered aluminum and very finely powdered iron (iii) oxide. Foil has far two problems; first it has WAY too small a surface area to be effective, and secondly it tends to have an impervious coating of aluminum oxide on the surface, making it all but useless for a solid-state reaction like thermite. Secondly, rust isn't really pure enough iron (iii) oxide. Rust is a combination of multiple iron compounds, including iron oxides, iron hydroxides, and iron carbonates, in both iron (ii) and iron (iii) oxidation states. For an effective thermite reaction, you really need finely powdered and scrupulously pure iron (iii) oxide (Fe2O3). Thirdly, a match tip MAY possibly start the reaction, but not reliably. What you need is something WAY hotter, like a blowtorch, or even better, a chemical starter like sodium chlorate. All of this is MUCHO dangerous, and I probably wouldn't be messing around in any room you don't want burned to the ground. If you want to do real thermite, you need to order finely powdered aluminum and finely powdered iron (iii) oxide from a reliable chemical supply house; just be aware that they are likely required to report such orders to authorities, so don't be surprised if you get a call from the po-po before they even show up at your door, wondering what you are doing ordering ingredients for a dangerous explosive... --Jayron32 17:55, 15 September 2009 (UTC)

Welcome to the Wikipedia Reference Desk. Your question appears to be a controlled demolition question. I apologize if this is a misevaluation, but it is our policy here to not to tell people how to blow up tall buildings as part of a massive government conspiracy. Please attempt to solve the problem yourself. Fences&Windows 21:50, 15 September 2009 (UTC) Lol. Sagittarian Milky Way (talk) 17:09, 16 September 2009 (UTC)

I recall no such policy. We've given advice on how to hide the body before, which can't be much better. Vimescarrot (talk) 09:01, 16 September 2009 (UTC)

I believe Wiktionary has the definition of wikt:facetious, which may prove informative in understanding the subtext in Fences and windows comments. --Jayron32 12:05, 16 September 2009 (UTC)

I wouldn't be holding the match while it went off, lol. I'd make a rudimentary fuse. If the oxidation film is so bad, very finely powdering it will make it worse, and since powder lasts long enough to work, you could polish your foil before cutting. Does wood stop burning if it has low surface area to mass? It just burns slower. Sagittarian Milky Way (talk) 17:09, 16 September 2009 (UTC)

But if the thermite burns slow enough, there will never be enough activation energy present to maintain the reaction. That's the point, the thermodynamics of the reaction are invariant whether you use aluminum foil or powdered aluminum. However, the chemical kinetics are the controlling factor here. Aluminum foil's low surface area slows down the reaction SO MUCH that it will happen, but on the order of magnitude of days rather than nanoseconds. You can recreate the endproducts of thermite if you have ever left a rusty steel pan in contact with an aluminum pan. After a week or so, the aluminum pan will develop a white powder (aluminum oxide) all over it. Its exactly the same reaction as Thermite. Absolutely no difference, except it is happening VERY SLOWLY. The difference is the surface area. To use your wood analogy, its the difference between a slowly smoldering piece of paper and a sawdust explosion which has taken out many a wood shop... Same material, but what in one case is a slow, controlable reaction becomes a violent reaction only because of the surface area of the particles. In thermite, the relationship is magnified even more. It is ALL about using the powdered chemicals here. --Jayron32 17:21, 16 September 2009 (UTC)

If problems are not insurmounatble, the beach in winter would be a better place. No one's there, the shielding/target material is plentiful, and you can use as much as you want. Run! Sagittarian Milky Way (talk) 17:15, 16 September 2009 (UTC)

Careful with the beach...one of the dangers of the standard thermite demo with sand to catch the results is that the sand needs to be dry. Otherwise the molten iron lands on damp sand, the heat vaporizes some of the water, and you get some ejection of sand and hot metal. This exact expermental setup has been used as a model of some processes related to volcanic activity (for example, doi:10.1016/S0377-0273(01)00280-3). DMacks (talk) 20:27, 16 September 2009 (UTC)

As a point of further clarification, I have personally done the thermite reaction in front of a classroom of students. If one is properly trained, it is safe. But you must be aware of the dangers, and take proper precautions, and know exactly how, and why, and exactly what happens in the reaction. I didn't just learn how to do it as an educational demonstration from a book either, or tried to figure it out myself. I worked personally with an ex-professor of mine who showed me exactly how to do it right. Like anything else of this magnitude, it is OK to do in the right hands, but if you have never worked with Thermite before in a supervised situation, it is NOT the sort of stuff you want to play around with. --Jayron32 17:26, 16 September 2009 (UTC)

rice growing

The instructions I have for growing rice seeds says to soak them for 36 hours and then to let them dry out for 24 hours and then to plant then in potting soil covered with several inches of water. However, after soaking some seeds have already sprouted roots. Should these seeds be dried for 24 hours too? -- Taxa (talk) 20:36, 15 September 2009 (UTC)

Without even researching this, I'd say divide the sprouted seeds into two groups. Plant one group right away, dry the other group for 24 hours before planting. Let us know the results! The main rationale I can see for the drying step is to prevent rotting. Totally WP:OR on my part! ;) Franamax (talk) 22:21, 15 September 2009 (UTC)

About half do not have roots so I'll have 2 test and 2 control groups. -- Taxa (talk) 23:39, 15 September 2009 (UTC)

Looks like the ones put in yesterday with only an hour or so of drying have shoots (or upsidedown root tips) that are doubling in length every 12 hours. I've setup a crude timelapse camera. -- Taxa (talk) 03:05, 17 September 2009 (UTC)

I guess this has to do something with dormancy breaking for which I can't find an article. But there is an article on seed dormancy. 95.112.171.137 (talk) 18:10, 16 September 2009 (UTC)

matter, gravity, space and time

How can matter influence space and time? I mean sure if you have a tree lying in the road and have to take a longer route then matter (the tree) can increase distance and time but that is not what I mean. -- Taxa (talk) 20:39, 15 September 2009 (UTC)

Matter has mass - mass distorts space and warps time. Einsteins discovery of special relativity was only widely accepted after an expedition measured the amount by which the light of a distant star was bent by the curvature of space due to the sun's mass during a solar eclipse. In everyday experience, the effect is far too small to measure - but for things like stars - it's very important. SteveBaker (talk) 20:57, 15 September 2009 (UTC)

That's general relativity, Steve. GR is SR+gravity. --Tango (talk) 21:20, 15 September 2009 (UTC)

The traditional analogy is one of masses placed on a trampoline, they all indent the surface, and all to some extent lie in each others indentations, and thus roll together; ergo gravity. Einsteins revelation was that time and space are a single fabric which is distorted by mass, acceleration of the observor and appears differently from different reference frames (an important implication being that there is not absolute frame, hence relativity). The best places to start are introduction to special relativity and introduction to general relativity, the former not relating to distortions by mass, but is bust understood prior to the latter. Elocute (talk) 23:17, 15 September 2009 (UTC)

That analogy is more the "what" than the "how". The "how" is more difficult, I don't think we really have an explanation for that, it's just the way it is. --Tango (talk) 23:22, 15 September 2009 (UTC)

Just as an aside...how were things like this explained prior to the advent of the items we generally use in analogies to explain them. I mean, before trampolines existed, before thin sheets of rubber and foam existed, and all they had was, I don't know...sticks, ,bricks and papyrus, how did people speculate how this would appear and work? DRosenbach ^{(Talk | Contribs)} 02:13, 16 September 2009 (UTC)

Well, the flat-earth nut-jobs believe that gravity doesn't exist at all - it's just that the earth itself is accelerating at 1g straight upwards. SteveBaker (talk) 19:26, 16 September 2009 (UTC)

One thought that came to mind which your question give me the opportunity to say is that any solid object in air at sea level sort of forms a dent or hole or something in the air. The space part is easy to see and so is the time distortion if the object is moved. In fact you could probably apply the analogy of the need to go around a solid sphere located in air as an increase in distance and time. Mass occupies space and two masses can't occupy the same space at the same time. Think of a solid sphere and air. -- Taxa (talk) 05:21, 16 September 2009 (UTC)

General relativity was first presented in 1915. Predecessors to the trampoline date back at least as far (Trampoline#History). --Tango (talk) 02:17, 16 September 2009 (UTC)

Tango is right to point out that the trampoline by far predates the concept of spacetime. In fact the most abstract of physical theories are all fairly recent, electromagnetism, GR and SR all within the last 150 years, all being somewhat hard to get your head round, and of course QM which has no conventional interpretation, was a product of the 20th century. Before this, I think it is fair to say, that theories explained things in terms of Newtonian hardball particles, which essentially act like billiard balls, and waves, like the ones in the sea, so theories were largely tangible in terms of common natural phenomena. Elocute (talk) 09:18, 16 September 2009 (UTC)

Bugs, Sun, Moon

Bugs seem attracted to light. At least, it seems so at night while I'm inside, the lights are on, and a window is open. Questions: (a) Is there a Wikipedia article on this phenomenon? (b) Do adventurous bugs therefore try to reach the Sun during day, and the Moon during night? Comet Tuttle (talk) 22:06, 15 September 2009 (UTC)

The phenomenon is called phototaxis and its existence in insects is very well known but not very well understood. Our article doesn't even mention it, but you can find stuff on the web, for example this page. (b) No, but one hypothetical explanation of the phenomenon is that they use the sun and moon as navigation cues. Looie496 (talk) 23:29, 15 September 2009 (UTC)

I wonder if this is what moths that fly several miles above the earth in very large groups at night are doing? -- Taxa (talk) 23:49, 15 September 2009 (UTC)

Several miles? What makes you think there are moths several miles up? --Tango (talk) 02:18, 16 September 2009 (UTC)

Maybe not several but probably higher than a mosquito would fly. -- Taxa (talk) 05:13, 16 September 2009 (UTC)

QI says moths orientate themselves by moonlight. When Man comes along and creates a million tiny artificial moons, moths get confused. Vimescarrot (talk) 08:57, 16 September 2009 (UTC)

Not that I'd want to argue with Mr Fry's researchers but here is a bit more information on this behaviour in moths. There still seems to be some debate. Martlet1215 (talk) 13:33, 16 September 2009 (UTC)

Design specifications for industrial pipeline flame arrester

I am a manufacturer's representative and have been approched about selling a line of flame arresters,tank vent and vacuum release valves, and tank seal valves. I'm attempting to evaluate how acceptable these products will be in the U.S. market by detemining if they meet the most commonly required U.S. design and operating specs. I have not been able to find a source that calls out those specs.

Can anyone tell me what they are, or suggest where I might find them? 69.152.195.244 (talk) 22:21, 15 September 2009 (UTC)

Right off the bat, I'd suggest contacting Underwriters Laboratories directly. They are one of the US NRTL's who would have good information. Possibly our ASME article or links therefrom would have some contacts also. Franamax (talk) 22:27, 15 September 2009 (UTC)

Why is it colder in the winter?

1. Angle of incidence of sun's rays.
2. Depth of atmosphere through which sun's rays must travel.
3. Length of day.

Does anyone know the relative importance of each of these factors? I would like to be able to say that x% of the difference is due to factor 1, y% to factor 2, etc. -- even if the x and y are just ballpark figures. —Preceding unsigned comment added by 86.134.9.51 (talk) 23:44, 15 September 2009 (UTC)

Start with the Winter article and see where it takes you. Baseball Bugs ^{What's up, Doc?} carrots 23:49, 15 September 2009 (UTC)

Already been there I'm afraid. The linked Effect of sun angle on climate makes the rather vague statement that "the angle of sunlight" is the "basic mechanism" but does not give the specific comparative information that I'm after. It also isn't clear in context whether "the angle of sunlight" includes the depth-of-atmosphere effect. 86.134.9.51 (talk) 00:01, 16 September 2009 (UTC).

For all intents and purposes, the first item is the only one that matters. From the first sentence of that linked article, "The amount of heat energy received at any location on the globe is a direct effect of sun angle..." Moreover, the change in the length of the days is technically also due to the tilt of Earth's axis, and you can relate the depth of the atmosphere to that as well. If you want numbers, you can say that the angle of incidence is responsible for about 100% of the difference, although location in orbit does have a small influence. This of course only applies macroscopically, as local patterns and locations (currents, water, mountains, etc.) can change things radically. ~ Amory (user • talk • contribs) 00:41, 16 September 2009 (UTC)

However, for a factor that is unrelated to axial tilt, consider the effect of the eccentricity of Earth's orbit about the sun. — Lomn 00:48, 16 September 2009 (UTC)

For half of the planet -- the Northern Hemisphere -- that operates against the other effects. The Sun is closest in January. --Anonymous, 04:30 UTC, September 16, 2009.

Earth's_orbit#Events_in_the_orbit also discusses this. Mitch Ames (talk) 11:52, 16 September 2009 (UTC)

The length of the day certainly matters - but the angle of incidence is the critical factor. The amount of sunlight hitting one square meter of the earths' surface is proportional to the cosine of the angle between the direction of the sunlight and a line at right angles to the surface. Since the earth's axis is tilted by 23 degrees - when the bit of land you happen to live on is tilted away from the sun - in winter it intercepts less sunlight. Suppose you happen to live in Havana, Cuba - which (by an amazing coincidence) is at 23 degrees latitude. In the middle of summer, the sun's rays are absolutely vertically above you at midday. The angle between "up" and the sun is zero degrees and cosine(0)=1. So 100% of the sun's energy is beating down on you. In mid-winter in Cuba, the axis has tilted and Rio de Janeiro is now right under the sun and in the middle of it's (southern hemisphere) summer. Havana is now pointing 46 degrees away from the sun at midday. cosine of 46 degrees is about 0.7 - so you're only getting 70% as much sunlight in midwinter as in midsummer at noon. However, that ratio varies depending on where you are on the planet. At the equator, the sun's angle changes by the same number of degrees as it does in Havana - but when you look at the shape of a cosine curve, you see there isn't any difference between -23 degrees and +23 degrees. On the other hand, if you are within 23 degrees of the North pole - the angle between "up" and the sun becomes 90 degrees and you don't get any sunlight falling on flat ground at all!

The day length varies too - check out File:Day length.jpeg - and you'll see that that Havana's day length changes from around 10.5 hours in the winter to about 13.5 hours in the summer. That's a +/- 15% variation - so there is about a total 30% variation between summer and winter - which is about the same as the amount of variation due to the angle of the sun's rays.

The amount of atmosphere that the sun's rays have to pass through is much less important - if the sunlight is absorbed by the air - then the air must heat up. The total amount of heat that hits the ground is less when the path-length is long - but there is more heat being dumped into the air. What's more difficult to understand is that when sunlight hits the ground - if the ground is (for example) bright white snow - then it's going to be reflected away again without warming it up much. But on (say) dark soil, most of it will be absorbed and turned to heat. So heating up the air on the way in (and out again) actually saves some heat.

But it's not really that simple - there are vast numbers of other variables to consider. The amount of cloud cover for example. Bright white high altitude clouds will reflect the sun away before it gets any chance to be absorbed at all. The amount of humidity in the air will alter the ability of the air to hold the heat. If the prevailing winds shift from on-shore to off-shore or from blowing across a major desert or not.

It would be rash to come up with a single answer here. The result certainly depends dramatically on your latitude. SteveBaker (talk) 00:44, 16 September 2009 (UTC)

Steve, good explanation; but I got a little lost reading your explanation about atmospheric absorption. Categorically, if the insolation is being absorbed by a lot of atmosphere, then it's warming air somewhere else (e.g. at a lower latitude). Complicated, as you say. Primarily, I think the incident energy per square meter (which is dictated by the incoming solar illumination angle), is the chief driving factor in seasonal temperature variation. Large-scale convection in the atmosphere (e.g. "prevailing winds") would be the next most prominent effect (noting, of course, that these prevailing winds are coupled to the seasonal solar heating in a complex way). Nimur (talk) 14:31, 16 September 2009 (UTC)

Thanks for the replies guys... 86.134.9.51 (talk) 01:15, 16 September 2009 (UTC).

Heh. Now I'm trying to imagine an environment which is warmer in winter due to vertical elements. Something like a sparse forest full of tall trees, with snow on the ground all year round. 81.131.45.124 (talk) 09:50, 16 September 2009 (UTC)

There's another factor to consider, and that's the "delayed effect" of heat buildup and dissipation. I don't know what the technical terms are for it, I just know its effect. Based on angle of sun and shortness of day, you'd think December 21 would be the coldest day of the year and June 21 the hottest. But the "height of summer" and the "depth of winter", in terms of heat (or lack thereof) really occur roughly halfway into the season, i.e. early August and early February, and some days or weeks either side of those points. Baseball Bugs ^{What's up, Doc?} carrots 01:40, 16 September 2009 (UTC)

That delay effect is based on the heat capacity (more specifically the Thermal mass) of the atmosphere and ground. If you were standing on an atmosphereless and perfectly reflective sphere, then the hottest day WOULD be the summer solstice. However, since you are not, the material of the atmosphere and the ground takes time to absorb energy and change temperature accordingly, and that time is a direct consequence of the heat capacity of the stuff the earth is made of. --Jayron32 02:27, 16 September 2009 (UTC)

Actually, if the earth had no atmosphere and it was perfectly reflective, would there be any heat at all, other than geothermic heat? If you were standing anywhere on that surface, absorbing the sun's rays with no protection other than your space suit, wouldn't you pretty much be equally hot no matter where you were? Baseball Bugs ^{What's up, Doc?} carrots 04:35, 16 September 2009 (UTC)

My space suit is height h and w x w when viewed from above (it's the new cubist model). Standing at a pole at equinox I get h/w more warmth than standing at the equator. Cuddlyable3 (talk) 08:51, 16 September 2009 (UTC)

The intensity of the sun's radiation hitting the surface of the Earth is proportional to the sine of the angle of the sun above the horizon. We can find this value based on the time of day, latitude, and time of year. In particular if A is the strength of the sun directly overhead, then the strength of the sun during daytime in general is

$f(t)=A[\cos({\frac {2\pi }{day}}t)\cos \psi \cos \theta -\sin \psi \sin \theta ]$

where t is the time of day in relationship to noon, θ is the latitude, and ψ is the angle that the Earth's axis is tilting away from the sun at the given time of year (at the north end). Let α be the overall tilt of the axis, which is about 23.5°, then ψ = α in the (northern hemisphere) winter, ψ = -α in the summer and ψ = 0 at the equinoxes. More generally

$\psi =\sin ^{-1}(\sin \alpha \cos({\frac {2\pi }{year}}T))\approx \alpha \cos({\frac {2\pi }{year}}T)$

where T is the time of year in relation to the northern hemisphere winter solstice. From this information, we can find sunset based on latitude and ψ, which is the time t₀ after noon where f(t₀) = 0. That gives

$t_{0}={\frac {day}{2\pi }}\cos ^{-1}(\tan \psi \tan \theta )$

Similarly sunrise is at t₀ before noon, and so the length of the day is 2t₀. Note that if |ψ|+|θ| > π/2, there's no solution for t₀, since this corresponds to places that are experiencing 24 hours of light or darkness so there is no sunset or sunrise. To find the total incident radiation per area over the course of the day, we can integrate f(t) which yields

$R=\int _{-t_{0}}^{t_{0}}f(t)dt=2A[{\frac {day}{2\pi }}\sin({\frac {2\pi }{day}}t_{0})\cos \psi \cos \theta -t_{0}\sin \psi \sin \theta ]$

for places with day and night and

$R=\int _{-{\frac {day}{2}}}^{\frac {day}{2}}f(t)dt=-A(1day)\sin \psi \sin \theta$

for places with 24 hours of daylight. With these tools you can get some actual values for how the length of day and amount of sun you get where you are varies over the course of the year. This ignores any atmospheric effects and also the fact that the Earth's orbit isn't totally circular, which messes things up a little, but I'm definitely not going to attempt to correct for that. Rckrone (talk) 06:45, 16 September 2009 (UTC)

The example given of a planet without an atmosphere, thus removing air absorption from the discussion, leaves us with the question of why the sun angle matters. If you position yourself such that you're facing the sun directly, you're going to get the same number of photons hitting you directly from the sun, no matter where you are on the half of that sphere that's facing the sun. The difference, I suppose, would be the number photos reflected and hitting you, which would tend to be greater or lesser depending on the angle at which those photons are hitting the planet at the point you happen to be standing. Baseball Bugs ^{What's up, Doc?} carrots 02:33, 17 September 2009 (UTC)

That answer doesn't make any sense. Being without an atmosphere would kinda make the whole thing meaningless. You can't talk about 'weather' without considering the atmosphere! However, despite that, the temperature of the ground would vary depending on the angle of the sun to the surface - and assuming you're not trying to measure the temperature of the vacuum - or that of your own body - neither of which have anything to do with this question - then what are you measuring if not the temperature of the ground - which is most certainly affected by the angle of the incident sunlight?!? SteveBaker (talk) 12:23, 17 September 2009 (UTC)

September 16

What is "absolute mass"

What is meant by the term "absolute mass?" --Simeon24601 (talk) 00:02, 16 September 2009 (UTC)

See Atomic mass unit. SteveBaker (talk) 00:10, 16 September 2009 (UTC)

It's in direct comparison to a relative mass (i.e. the ratio with respect to a second mass). In general, "absolute mass" would be measured in a standard unit (such as kilograms), while "relative mass" should be dimensionless. Nimur (talk) 14:33, 16 September 2009 (UTC)

Michelson-Morely Experiment

Let's imagine that we have the typical setup of a M-M interferometer, as shown in the picture, and that there is actually an ether, with the earth travelling through it at a speed v. The lengths of each arm are l. Normally the analysis for this setup is done where one arm is parallel to v, where the time delay between the paths is v^2*l/c^3. My question is(yes it is a homework question, but I've worked on the problem already and just need a hint) to show that the formula for this time delay if one arm is at an angle of θ to v is v^2*l*cos^2(θ)/c^3. My approach was say that ether was moving with respect to the experiment. The velocity vector of light observed from our reference frame would therefore be equal to the vector sum of the actual velocity of light and the velocity of the ether. Using the law of cosines, I managed to get what appears to be the exact formula for this time delay. But the formula's really messy, and I can't for the life of me see how it would reduce to v^2*l*cos^2(θ)/c^3. There's also a lot of algebra and trig identities involved...the math is a bit involved seeing as how the final answer is so simple. Is there a simple way of going about this? —Preceding unsigned comment added by 76.68.245.124 (talk) 06:44, 16 September 2009 (UTC)

Sorry, I forgot to include the picture.

Though using a contemporary laser, this Michelson interferometer is the same in principle as those used in the original experiment.

I suspect v^2*l*cos^2(θ)/c^3 is a first order approximation. The exact value probably isn't going to come out to anything nice, but v is assumed to be much smaller than c so higher order terms are going to be negligible. Rckrone (talk) 16:58, 16 September 2009 (UTC)

Since you did not post your calculations, there is no way to verify wheather you have made any mistakes. Nevertheless I suggest you should check if the angle you define as theta is indeed the same angle the problem defines as theta. Dauto (talk) 18:55, 16 September 2009 (UTC)

neurovegetative

What does neurovegetative mean, as in "neurovegetative symptoms"? Lova Falk (talk) 10:52, 16 September 2009 (UTC)

The term Neurovegetative system is a redirect to Autonomic nervous system; I am pretty sure that unqualified, the term "neurovegetative" refers to loss of consiousness, either temporarily or permanently, as in Persistent vegetative state. --Jayron32 11:59, 16 September 2009 (UTC)

More specifically, a 'vegatative state' is one in which the patient is no longer comatose – indeed, may be awake – but has no awareness or apparent consciousness. The article on PVS linked by Jayron32 has a bit more description and details. TenOfAllTrades(talk) 13:03, 16 September 2009 (UTC)

Thank you, but actually I don't think this is correct. For instance this sentence: "A relationship between neurovegetative symptoms and an increased risk of sudden infant death (SID) has been frequently described. Such symptoms are vomiting because of gastroesophageal reflux, breathing disorders while nutritive sucking, excessive sweating during sleep, prolonged apneas and apneas with associated symptoms, further unexplained episodes of cyanosis, pallor and loss of muscle tone." (http://www.websciences.org/cftemplate/NAPS/archives/indiv.cfm?ID=19973095). In this article vomiting, breathing disorders etc. are examples of neurovegetative symptoms, but I would like to get an exact definition instead of examples. Lova Falk (talk) 13:50, 16 September 2009 (UTC)

In that context neurovegetative = autonomic system exactly, which was the first guess I made. All of the symptoms are events of the autonomic nervous system, which means that they occur outside of conscious control (things like vomiting and breathing regulation). What it is saying is that events controled by the autonomic nervous system are closely linked to SIDS. --Jayron32 17:12, 16 September 2009 (UTC)

Glomerular filtration rate

In terms of eGFR, what's the sense of the 1.2 and 0.75 coefficients for blacks and females, respectively? Are blacks assumed to be bulkier and have greater metabolism, the same way in which I sense females are assumed to be more slender? Would black females be 0.9, a combination of the two? This would seem to skew the results for a large subset of skinny black men and an even larger subset of black females, who I can't seem to conjure up as being necessarily less slender than white females. DRosenbach ^{(Talk | Contribs)} 14:27, 16 September 2009 (UTC)

That article cites several sources for the equations. Since these are empirical formulae to describe clinical data, it is unlikely that there is a better source than the original research articles, which are linked in the footnotes of renal function. This one explains some of the statistical derivation; and this one establishes the +1.21 "ethnicity bias". Nimur (talk) 14:38, 16 September 2009 (UTC)

Thanx! DRosenbach ^{(Talk | Contribs)} 14:56, 16 September 2009 (UTC)

Healthy liver

What food/drink is good to keep the liver healthy and look after it? Thanks for info. --AlexSuricata (talk) 15:22, 16 September 2009 (UTC)

The liver is perfectly capable and has been designed and developed over millions of years to stay healthy as long as it is not abused with unhealthy food or drink. I would have serious doubts about any food, drink or other product that claims to make your liver healthy in the absence of any pathology. Bear in mind 'detox' is an advertising weasel word little used by proper doctors. 86.4.181.14 (talk) 17:00, 16 September 2009 (UTC)

That would be pathosis. Pathology is the study of disease. DRosenbach ^{(Talk | Contribs)} 02:20, 17 September 2009 (UTC)

It's more like what food/drink is NOT good. Too much fatty food, too much alcohol, to name two. Baseball Bugs ^{What's up, Doc?} carrots 02:27, 17 September 2009 (UTC)

In the UK medical staff talk about 'pathology' meaning the presence of disease. "I can find no evidence of brain pathology in this patient" for example. 86.4.186.107 (talk) 06:28, 17 September 2009 (UTC)

is it common for people to sneeze after taking cough medicine

and if so why do they do that? —Preceding unsigned comment added by 218.186.12.249 (talk) 15:54, 16 September 2009 (UTC)

People sneeze for the strangest reasons. exposure to Sunlight or chocolate, being sexually aroused or having a full stomach are all documented examples. There was an article on it in the 15th of April 2009 issue of New Scientist [8] if you'r interested and can get hold of it at a library.

That said, I seem to recall that sneezes can be induced by an increased serotonin level. Cough syrup often include Dextromethorphan which is Serotonergic, which means it can increase the serotonin level. So that's a possible explanation for why cough syrup makes a person sneeze.

As an aside, you may want to see Dextromethorphan#Drug interactions for drugs that should not be taken at the same time as one is using cough syrup, but apart from that we're not allowed to give medical advice here at the reference desk. EverGreg (talk) 19:56, 16 September 2009 (UTC)

Perhaps a simpler explanation is that cough syrups often have aromatic substances in them (to help clear your nose or something, I suppose) - so it could easily be that this is somehow irritating the lining of you nasal passages and causing a sneeze. SteveBaker (talk) 12:16, 17 September 2009 (UTC)

Aromatic substances? Yeah, many of'em can make you wanna sneeze alright.  ;-) 98.234.126.251 (talk) 03:36, 19 September 2009 (UTC)

Help identifying an insect (and maybe a flower)

I'd like to identify the hummingbird moth I've photographed so that it can be inserted into the appropriate article. At the moment it's located here, on Flickr, but once it's been identified I'll add it to Commons. It looks to have a distinctive red blotch on its back, but none of the species of the hemaris genus seem to have this marking as far as Wikipedia is concerned. Any help will be gratefully appreciated! To aid your efforts, the photo was taken in the south of France. I have no idea where to begin in identifying the flower, though. Seegoon (talk) 17:21, 16 September 2009 (UTC)

Looks to me like, not a Hemaris genus Hummingbird moth (more often called Sphinx moths in the UK), but a Macroglossum genus Hawk moth, specifically a Hummingbird Hawk-moth Macroglossum stellatarum (both Hemaris and Macroglossum fall within the Sphingidae family). The russet-brown dorsal patch may be a local sub-species variation, or particular to one sex.

I'm not so good with garden plants, but the flower might be a cultivar of Phlox. I'll delve into my Mother's more extensive garden reference books when I visit her tomorrow, unless someone else has already come up with a firm ID. 87.81.230.195 (talk) 17:57, 16 September 2009 (UTC)

I agree; definitely doesn't look like a Hemaris, which apparently all have windows in their wings. These M. stellatarum pics show a bit of a reddish patch on the back: [9], [10]. The parent site has a ton of Sphinx pics: [11]. --Sean 18:44, 16 September 2009 (UTC)

<sings> You are the windows in my wings.... --Trovatore (talk) 01:23, 17 September 2009 (UTC)

Yes, now I look at these further pictures of life-worn individuals, rather than idealised illustrations from books, I realise that the reddish patches are actually areas of 'naked' thorax, which in a pristine specimen is entirely covered by the greyish thorax scales/hair. 87.81.230.195 (talk) 19:28, 16 September 2009 (UTC)

I think the flower is Cape Plumbago, Plumbago auriculata.--Eriastrum (talk) 23:52, 16 September 2009 (UTC)

You guys astonish me. I expected a couple of shots in the dark at best, but this is impressive. Collaboration in motion. Thank you all! Seegoon (talk) 18:38, 17 September 2009 (UTC)

how to make a mini hot-plate?

how do i make a mini hot-plate? prefibly about an inch long and wide. —Preceding unsigned comment added by DanielTrox (talk • contribs) 19:06, 16 September 2009 (UTC)

I guess I'd start with something like a soldering iron - you can pick them up pretty cheap - then you just need to figure a way to keep it in good thermal contact with the underside of your small metal plate. I'd probably dismantle the iron and just keep the heater and associated wiring. You can even get soldering irons with adjustable temperature. SteveBaker (talk) 19:11, 16 September 2009 (UTC)

No liability is assumed in the event of injury or damage from experimenting with a red hot object. Use extreme caution. Avoid using a resistance heat element like ones in a toaster, which have the line voltage present on the resistance wire, or anything with an energized conductors exposed. Photographic supply and art supply houses sell "tacking irons," used in dry-mounting art or photos. They have an insulated handle and a small heated area. Some have a heat control. Attaching a soldering gun to a small metal plate might do the trick. Edison (talk) 20:25, 16 September 2009 (UTC)

Most electronic stores sell miniature heaters. They are resistors that generate a lot of heat. The resistor is usually wrapped in a metal heat shield to help dissipate the heat. They get pretty hot - but maybe not as hot as you like. I've only used them for temperature control for camera housing units. If it gets too cold inside the unit, I send electricity to the heater (resistor) until it warms up. -- kainaw™ 02:08, 17 September 2009 (UTC)

Electron microscope?

Hey, y'all, what's up? So the other day in Biology class, we were talking about microscopes. My teacher mentioned something about an electron microscope, and said something like they cost 7 billion dollars or something. He also said there's this one school that has one. So I was wondering, what would happen if someone dropped it? I need to get this off my mind 'fore I do something stupid. Thanks. --Evan —Preceding unsigned comment added by 99.61.157.103 (talk) 22:14, 16 September 2009 (UTC)

You can't "drop" an electron microscope (of any type). They take up a space of at least several cubic metres. Even lifting one up would require Heraclean strength. By the way, I think you mean seven million dollars, not seven billion. Intelligentsium 22:17, 16 September 2009 (UTC)

cf home made electron microscope, which Wired says cost $10,000 -- Finlay McWalter • Talk 23:13, 16 September 2009 (UTC)

(ec) Most of them aren't worth nearly that much. Right now on eBay you can have an as-is may-be-incomplete buy-it-now transmission electron microscope for less than five thousand U.S. dollars. More realistically, you can get working, good-quality used TEMs and SEMs from a few tens of thousands of dollars up. (All the bells and whistles will run you a quarter million or so, used.) If you tried hard and bought a lot of ancillary accessories (or picked up a bunch of features not actually part of the imaging side of the instrument), I suppose you might be able to spend seven million on a new EM.

Any decently-sized university science department will have one or more, as do many large hospitals. You won't be able to drop one, because as Intelligentsium notes, you wouldn't be able to lift it in the first place. A good running tackle might screw up the alignment of the optics, though. TenOfAllTrades(talk) 23:18, 16 September 2009 (UTC)

Large SEMs and TEMs weights hundreds of kg and cannot be lifted by human, but small tabletop SEMs weights only about 40-50kg an is of size of about 2 to 3 ATX cases, so these can be picked up (and dropped (if unlucky)). -Yyy (talk) 09:28, 17 September 2009 (UTC)

As it happens, my son went to the only high school in the USA to have a working electron microscope (or so they claim). The School of Science and Engineering in Dallas, Texas. [Their website has a short video about it]. SteveBaker (talk) 01:10, 17 September 2009 (UTC)

Maybe one of the few. A more credible claim would be only-in-state, similar to what is said about this one in Connecticut. And there's this one in Washington state. DMacks (talk) 01:25, 17 September 2009 (UTC)

I would guess that a reasonable entry-level scanning electron microscope costs only a few thousand dollars; this is not so different from a high-quality optical stereomicroscope price. I've found a few on eBay for about $3000 in "as-is" condition (presumably functional). As far as damage, I'd be more worried about clogging the vacuum system or putting the wrong kind of lube on the roughing pump - these are the sort of "newbie hazards" that can destroy or damage such equipment (hopefully nobody's clumsy enough to drop the gear, but I can imagine some transport hazards). Nimur (talk) 02:36, 17 September 2009 (UTC)

September 17

Sunscreen stability?

Hypothetically, if I apply sunscreen in the morning (before sunrise) and stay inside a dark room with no windows, will I have any UV protection by the afternoon? I was shopping for sunscreen today and noticed many formulas are marketed with "UV Extenders" that supposedly keep sunscreens from breaking down in the sun. Is this true? Are sunscreens really that short lived -- even without exposure to UV light? --70.167.58.6 (talk) 00:08, 17 September 2009 (UTC)

This is a complete guess based mostly off of my own readings of sunscreen bottles, but I imagine a large portion of the reason why sunscreen wears off and needs to be reapplied is due to your activities when wearing such things, namely swimming and sweating. If you sit in the dark for a few hours, you probably will have some protection(after all, you're supposed to apply (half) an hour before exposure) but some will have worn off due to your bodily secretions. ~ Amory (user • talk • contribs) 02:16, 17 September 2009 (UTC)

Wouldn't the lotion also absorb and dissipate? Baseball Bugs ^{What's up, Doc?} carrots 03:47, 17 September 2009 (UTC)

Probably, although I suppose that depends on how well it puts the lotion on its skin. ~ Amory (user • talk • contribs) 04:46, 17 September 2009 (UTC)

Quantity certainly matters. You've probably seen cricketers, for example, with a thick slather of sunscreen on exposed tips that are in the sun for hours, or folks on the beach that put a big glob of it on their noses. Nothing's going to penetrate that for awhile. Baseball Bugs ^{What's up, Doc?} carrots 04:51, 17 September 2009 (UTC)

Sorry but I'm a bit confused by your question. At first in the hypothetical example it sounds like you are asking whether sunscreens break down after application without exposure to UV/sunligh. Then you say many sunscreens have formulas to reduce break down under sunlight/UV light and whether it's true they break down I presume you mean in the sun/UV light. Then you ask again whether sunscreens are short lived without exposure to sunlight/UV light. Do you want to know about breakdown to sunlight/UV light, due to other reasons or both? Anyway as has been mentioned, sunscreens may wear off for a number of reasons. If you want to know about whether they break down upon exposure to UV/sunlight, the answer is yes they usually do. [12] says 17 ingredients approved for use in the US break down significantly within 30 minutes. In particular "works by first absorbing the sun's energy so it doesn't penetrate our skin, and then releasing that captured energy by breaking apart, reacting with other chemicals in the sunscreen, or even kicking off free radicals. Some active ingredients are more stable than others, but nearly all break down to some extent in the sun." Unfortunately their figures are screwed so it's not clear how common these are used. This [13] and [14] may also be of interest. I have the idea this may have came up before so you may want to search the archives. Nil Einne (talk) 06:57, 17 September 2009 (UTC)

Number of planets

As solar systems go, does ours have a lot of planets? Or do we not have enough data to be able to make such a judgement? Dismas|^(talk) 00:26, 17 September 2009 (UTC)

No, we don't have enough data. However, a very large ( >> 10 ) number of planets seems unlikely, since, by definition, a planet must clear out its vicinity, and there is only so much vicinity available within a protoplanetary disc. --Dr Dima (talk) 00:33, 17 September 2009 (UTC)

Actually, the IAU didn't extend their (extremely bogus, IMO) definition outside our solar system.

I don't recognize the IAU definition, of course, so the problem could be reconsidered using a more sensible geology-based definition. --Trovatore (talk) 00:37, 17 September 2009 (UTC)

I don't see why it particularly matters what you recognise. You aren't the OP. In any case, if you want to use another definition, you should at least tell us what that definition rather then expecting us to guess what this 'more sensible geology-based' definition is, since none is given at planet Nil Einne (talk) 02:32, 17 September 2009 (UTC)

My point is that the IAU is without authority to redefine the word planet, and we should not be paying as much attention to them as most people seem to be doing. --Trovatore (talk) 03:54, 17 September 2009 (UTC)

As to what a more sensible definition would be, the "hydrostatic equilibrium" one that they rejected was not too bad. Except that it shouldn't matter whether the body is in orbit around another non-stellar body or not. My preference would be that the Moon, Titan, and the Galilean moons of Jupiter should all be recognized as planets. But I would like to see this happen by natural linguistic evolution, certainly not by the arrogant vote of some organization. --Trovatore (talk) 04:00, 17 September 2009 (UTC)

What I see is an arrogant notion that the IAU is not allowed to make their own decisions. They never said anything about the use of the word planet outside the IAU. They stated that when they use the word "planet", it must have a specific meaning that they chose to use. If you want to call any rock you find floating around in space a "planet", you are free to do so (as long as it is not in paperwork to be published to/from the IAU). Nobody from the IAU is going to toss you in jail. -- kainaw™ 04:11, 17 September 2009 (UTC)

If in fact the IAU definition were applied only in an IAU context, that would be fine (even though they still picked the wrong one). Unfortunately it seems that it is being followed much more generally. I deplore that fact — we should not follow them in this. --Trovatore (talk) 04:19, 17 September 2009 (UTC)

I don't understand why you consider a vote by a panel of experts to define a formerly rather fuzzy term to be "arrogant" - where as you (a single individual) can make up your mind without reference to the rest of the community and NOT be arrogant! That makes no sense. Anyway - there is now a perfectly usable definition for the word 'planet' - and here on the RD, we should use it because that's the scientifically correct thing to do. If you choose to use the word in some other context - you'd better make that clear on each and every occasion to avoid the chance of ambiguity. SteveBaker (talk) 12:11, 17 September 2009 (UTC)

Steve, the fact that the IAU has made its decision does not make it "the scientifically correct thing to do". Science is not conducted by votes. The IAU's action was completely improper, and we should resoundingly reject it. --Trovatore (talk) 20:13, 17 September 2009 (UTC)

Regardless of how we feel about the IAU, this discussion is not answering the original poster's question. Nimur (talk) 20:33, 17 September 2009 (UTC)

Our solar system has at most 4 planets (probably fewer) that we could detect if they were in the same orbit around another sun-like star. We have found stars with several planets, so it would seem we aren't that unusual. Until we have some data about smaller planets around other stars (work is being done - give it a couple of years), that isn't much more than a guess. --Tango (talk) 00:40, 17 September 2009 (UTC)

Right now, we can't detect planets even as small as Earth - let alone Venus, Mars, Mercury and stuff like Sedna and Pluto. Worse still, the further the planet is from the star, the harder it is to detect - so while we might have a shot at spotting another Mercury - we have a long way to go to be able to spot another Sedna...it took quite a lot of effort to find it right here on our doorstep! SteveBaker (talk) 00:55, 17 September 2009 (UTC)

Well, to be sure, apparently we have detected things that are pretty close to Earth size (1.7X)... see COROT-7b, which was in the news just today. --98.217.14.211 (talk) 01:20, 17 September 2009 (UTC)

Mass and orbital radius are generally the more relevant considerations, though, and COROT-7b is 5 times Earth's mass and 70 times closer to its star in those cases. As Steve notes, we're still a long way from finding Earthlike planets in Earthlike orbits, much less the smaller stuff. I think a previous discussion even established that it's not likely we could find a planet with Jupiter's mass and orbit from any astronomically appreciable distance. — Lomn 02:33, 17 September 2009 (UTC)

Diameter is significant for the newer "transit method", which is likely to be how we will detect Earth-like planets. The Kepler Mission should be able to detect Earth-like planets, but it will take some time - such a planet will have an orbital period of about a year (by definition!) so it will only transit about once a year. We need two transits, at least, to get meaningful data. --Tango (talk) 02:39, 17 September 2009 (UTC)

Well, actually - the difficulty of detection for the transit method is proportional to the cross-sectional area of the planet versus that of the parent star. So a 1.7 times bigger diameter planet is still almost three times easier to detect than an earth-sized one - and the fact that the parent star is considerably smaller than our sun makes it even easier to detect using this method because the planet occludes a greater percentage of the parent starlight. When you combine both of those things - I think you'll find that COROT-7b is at least five times easier to detect (in terms of required telescope sensitivity) than Earth would be. SteveBaker (talk) 12:11, 17 September 2009 (UTC)

I never said otherwise - I was just saying that diameter is a highly relevant consideration. Lomn was thinking of the wobble method, which isn't the way we're going to detect Earth-like planets (and isn't how COROT-7b was detected). I think the main thing that makes COROT-7b easier to detect is its orbital period of 20 hours. That means we can easily detect a large number of transits, which allows us to do fancy data analysis to remove noise and find the signal. An Earth-like planet will have an orbital period of about a year, which means we will only have a few transits the study so the signal:noise ratio needs to be much higher. A 5 times louder signal isn't that big a difference - these things are usually compared in terms of orders of magnitude. --Tango (talk) 16:18, 17 September 2009 (UTC)

Short Fever

I recently experienced a short (12 hour) intense fever, with temperatures of around 102. The fever was preceeded by a slight headache, and followed by a period of about 12 more hours of achy muscles and slight dizziness. Then it was gone, with nothing left but a slightly upset stomach (no vomiting, holding food without problems). The upset stomach has since passed, and left me thinking- wow, what just happened? There were no other flu symptoms beside the fever. Was it merely a passing bacterial infection that my immune system dealt with quickly? I realize advice cannot be given out, but explanations are appropriate I assume. Thanks 72.65.96.147 (talk) 02:47, 17 September 2009 (UTC)

No, explanations are not appropriate. A visit to a doctor is appropriate. You are explicitly asking for a diagnosis which we cannot provide. Sorry. --Dr Dima (talk) 03:10, 17 September 2009 (UTC)

This being the "change of seasons", there are plenty of bugs going around, like always. The symptoms vary in intensity and duration. Anything resembling the flu can be dangerous. See a doctor. Baseball Bugs ^{What's up, Doc?} carrots 03:45, 17 September 2009 (UTC)

Certainly we can't diagnose, whereas a medical doctor can. But are you all really sincere when you say "see a doctor"? Personally I would never bother the medical profession (or more to the point, subject myself to the inconveniences associated with the medical profession) based on the facts described. This is not advice of any sort; I'm just reporting what I would do. --Trovatore (talk) 05:07, 17 September 2009 (UTC)

Since they're being paid, going to a doctor is not "bothering" them, it's their job. And it's true a lot of us don't go to doctors when we maybe should. The issue is that the guy is asking for a medical opinion, and no one here (so far) is qualified to give an opinion that's anything more than "folk wisdom", so to speak. So if he wants a medical opinion, he needs to go to a medical professional, such as a medical doctor. Baseball Bugs ^{What's up, Doc?} carrots 05:15, 17 September 2009 (UTC)

As I explained in the parenthetical, it's not them so much I'm worried about being bothered; it's me.

My strong suspicion is that I would not get any satisfactory answer from a medical doctor on a question like this. He'll tell me a bunch of things it could have been, and explain that there's really no practical way to find out which, but since I'm already feeling better, why do I care? For this I should take time out of my day, get poked and prodded, and pay money? --Trovatore (talk) 05:21, 17 September 2009 (UTC)

Only if you choose to. No one can force you to go to a doctor. But if you want medical advice, wikipedia is not the place to get it. If you want to read wikipedia articles that describe various ailments, you're free to do so. That's not the same as giving medical advice to an individual. The articles merely explain some things about the diseases. It doesn't tell you what disease you have, if any. To get a diagnosis, you must see a professional. That doesn't guarantee a satisfactory result. But it's his job, so it's the best shot you've got. Baseball Bugs ^{What's up, Doc?} carrots 05:31, 17 September 2009 (UTC)

(to Trovatore) If you don't even trust a medical doctor to give a reliable solution to a problem like this, then what about random strangers on teh intrewebz makes you think that you are going to get a BETTER solution!?!? If doctors aren't going to give an acceptable answer, then you aren't likely going to get one, period... --Jayron32 12:18, 17 September 2009 (UTC)

Well, as for me, the answer is obvious. I can't go to much more than one doctor but I can ask many, many people on the net. Asking on the net is far less costly in time and money than going to one doctor, let alone to many. Asking on the net gives other people the chance to learn something, too. Asking on the net is far more safe than an overcrowded waiting room full of sick people with all kinds of infections. And what you'll get as diagnosis from a doctor in this case would be acute fever which is precisely what you already know. And as in this case the illness has already gone and it's pure curiosity to guess what it could have been I wouldn't see any use spending up to several average peoples wages on doctors. 93.132.128.221 (talk) 16:30, 17 September 2009 (UTC)

Absolutely right. Moreover, using medical care when you don't need it drives up the cost; basic supply and demand. Completely off topic -- very interesting article on health care in The Atlantic this month which I strongly commend to anyone thinking about the problem. The author wants to get away from using insurance to pay for routine medical care (which he says is like using your accident insurance to put gas in your car). If medical care were treated like a consumer good, there would be actual market discipline on the pricing.

So as to my completely unqualified guess, with ABSOLUTELY NO WARRANTY -- it's possible you had food poisoning. I recall reading somewhere that the so-called "24-hour flu" is usually food poisoning. It's hard to understand the lack of gastrointestinal symptoms, though. --Trovatore (talk) 20:06, 17 September 2009 (UTC)

If I visited a doctor right now, he/she would tell me I am perfectly healthy and then hand me an exorbitant bill. I have no reason to visit a doctor, because I am now fully recovered. I am merely in retrospect pondering what hit me. Trovatore gave me a straight answer. 72.65.96.147 (talk) 22:18, 17 September 2009 (UTC) 72.65.96.147 (talk) 22:17, 17 September 2009 (UTC)

Sound in free-space/vacuum

This is a completely hypothetical question about a scenario I'm trying to work into a piece of writing, and I'd be much obliged if someone could help a person who's very much not a scientist wrap his head around this subject. I've looked through all the articles on sound, vacuum, interplanetary and interstellar mediums and a number of other pages. The understanding I think I have is: Sound cannot travel through such a low-density, low-pressure body of matter like space because there is not enough for the vibrations to bounce off of, and therefore travel through. Theoretically, knowing that such a scenario is completely outside of the realm of possibility, what would have to happen to the interstellar medium in order for sound to travel through it? I would guess that the medium would have to increase in density and/or pressure, so that it more resembled something that could transmit vibrations, like atmosphere, air, water, etc... Is there a named process for these increases, when applied on a smaller scale? And then, radio waves can travel through space because they are NOT vibrations, and simply require a receiver to be turned into something a human would recognize as sound, right? Apologies for the rambling...99.62.112.181 (talk) 03:01, 17 September 2009 (UTC)

Sound is simply harmonic vibrations occuring in a substance. Nothing more than that. If you have matter (i.e. anything made of atoms) which is vibrating, you have sound. No atoms, no sound. The vibration is carried because the atoms bump off of each other, transmitting the energy from one atom to another. In "outer space", there are still atoms, but they are so far apart from each other that they cannot reliably transmit such vibrations; any energy you impart to one atom cannot be propagated in any predictable fashion because of the fantastically low densities of space. Basically, the signal-to-noise ratio is nill. So there is nothing you could do to "space" to make it transmit sound short of making it "not space" anymore, i.e. making it actual matter and filling it up with atoms and molecules and stuff. --Jayron32 03:48, 17 September 2009 (UTC)

Also, to answer your second part, radio waves are merely electromagnetic waves like light, that is they aren't really "waves" in the classical sense any more than a photon is a classical particle like a bowling ball is. Light does not "propagate" through matter like sound does. We use the term "wave" to describe both sound and (sometimes) light, but they are really VERY different phenomenons... --Jayron32 04:01, 17 September 2009 (UTC)

So, for example, if you're in a space suit on a walk-in-space on the shuttle or something, and some object bangs your helmet, you'll hear it, because there is air in the suit. But someone outside the suit won't hear that bang. Here's a poser, though. There are certainly individual atoms and/or molecules floating around in the so-called vacuum of space. They are just very far apart. But how far apart? Or has this ever been studied? Baseball Bugs ^{What's up, Doc?} carrots 04:14, 17 September 2009 (UTC)

Our article on Outer space notes that the matter density is on the order of "a few" hydrogen molecules per cubic centimeter; if we take a few to mean a countably small number (say a few hundred or a few thousand) then it becomes obvious how far apart these atoms really are when, at sea level pressures, a cubic centimeter of hydrogen contains 10¹⁹ molecules; by extension that means that the open space between those molecules is on the order of one billion billion times greater. This becomes even more understandable when put on human scales. Thus, if the distance between hydrogen atoms on earth were, say, 1 mile apart, then the distance between hydrogen atoms in space on the same scale would be roughly the distance between the Earth and the other side of the Milky Way galaxy. --Jayron32 04:25, 17 September 2009 (UTC)

OK, what I'm thinking is this, tell me if I'm wrong: sound comes from particles "banging into" each other. The closer together the particles are, the better resonance you get. For example, sound travels better under water than through the air, right? Consider an explosion of some kind. It makes quite a racket. If the air were thinner, it would make somewhat less of a racket. But if it were a greater explosion, it would make a greater racket. So what I'm suggesting is that the incredible amount of energy from, say, an exploding sun, might be sufficient to cause some degree of sound waves in the almost-vacuum of space. Not that you would live long enough to hear much of that sound if you were out in the midst of it. But that's the concept. What do you think? Baseball Bugs ^{What's up, Doc?} carrots 04:44, 17 September 2009 (UTC)

Not really. For something to propagate, you need to be able to create at minumum a "pulse" which can propagate through matter. An exploding star would generate such a "pulse", but regardless of how strong that pulse was, you would still need the surrounding matter to, when pushed, be able to hit other matter in such a way as to continue the pulse. Regardless of how hard it was pushed, the hydrogen in the deep of space is so diffuse that it can't be counted on to hit other hydrogen molecules in that manner. --Jayron32 12:16, 17 September 2009 (UTC)

I see. The way you would probably get a sound in space from that explosion would be if the energy started slamming those molecules closer together - in effect, creating a temporary "atmosphere" in that region, which goes back to the original point - that the molecules have to be close together. I'll postulate something else here, though - that you could, possibly, get some molecular collision in space as it is now, and hence some degree of sound - but probably at such low volume level as to be virtually undetectable. No U.S.S. Enterprise "whoosh", no matter how fast it's going. Baseball Bugs ^{What's up, Doc?} carrots 13:19, 17 September 2009 (UTC)

Sound in an ideal gas is not transmitted by particles bumping into each other. It's transmitted by simple motion of the particles. There are always gas particles bouncing off the diaphragm of your speaker. When you push the diaphragm toward the gas you reflect a few more particles per unit time than usual. Later, a few more particles per unit time than usual hit the receiver, pushing it backwards. The speed of sound is basically just the average speed of the gas particles, which is a function only of the temperature and the type of particle. It doesn't depend on the pressure or density. However, as the pressure or density goes down the received signal energy gets weaker (fewer particles) to the point where it's hardly worth trying to detect it. In principle, though, the interplanetary medium and interstellar medium do transmit sound (with a pretty high speed, but terrible signal strength). -- BenRG (talk) 13:28, 17 September 2009 (UTC)

For a truly ideal gas, wouldn't you get massive diffusion of the pulses because of the varying speeds of the particles? --Tardis (talk) 18:02, 17 September 2009 (UTC)

Remember that the mean separation between particles goes as the -1/3 power of the number density, so the billion billion factor difference in number density corresponds to "only" a million factor difference in distances. --Tardis (talk) 18:02, 17 September 2009 (UTC)

(ec)Well, come on, there's enough in common to use the word wave for both. Both phenomena are sinusoidal oscillations in something (pressure in the case of sound, electric/magnetic field strength in the case of EM). In similar ways they diffract around obstacles and interfere to produce an interference pattern. They actually have quite a lot in common.

There are also important differences, as you note; besides the one relevant to the original question (sound needs a material medium; EM doesn't), there's also the fact that sound waves are longitudinal whereas EM waves are transverse (so for example there can be no such thing as "polarized" sound). --Trovatore (talk) 04:17, 17 September 2009 (UTC)

In high school science, they used to teach us that literal "waves", like in those little wave-tank machines with the two vibrating probes (whatever those machines were called) are essentially analogous to electromagnetic waves, or simplified explanations, but not precisely the same thing. Baseball Bugs ^{What's up, Doc?} carrots 04:38, 17 September 2009 (UTC)

In one tiny respect, those are actually closer to EM waves than sound waves are to EM waves -- at least they're transverse. You still can't polarize them, though, because there's only one direction for them to be transverse in. --Trovatore (talk) 04:42, 17 September 2009 (UTC)

There's hardly any difference between light and sound. Light is a vacuum sound wave. Every kind of sound has a particle nature (see phonon). Photons are just phonons of light. Light can travel through vacuum because it's the vacuum that's waving. Ditto gravitational waves. Ditto everything, actually—electrons are also vacuum waves and that's why they can travel through the vacuum. -- BenRG (talk) 13:28, 17 September 2009 (UTC)

As I understand it, a gravitational wave is essentially a sound pulse traversing the spacetime continuum -- but generating a high-frequency gravity wave would be a pretty amazing feat. Looie496 (talk) 05:13, 17 September 2009 (UTC)

Two astronauts in vacuum could talk to one another via sound waves if the fronts of their helmets were connected by a tightly stretched string or wire. The sound should travel fine for many miles, since there is no wind, which interfered with 19th century acoustic phones on Earth. Edison (talk) 00:23, 18 September 2009 (UTC)

Moons of Mars

Keep reading articles on Mars dont know why but cant help it leaps out at me - the article that appears in wiki talks about the moons having starnge orbits for captured asteriods; My question is what would be the expected orbit of captured bodies around a planet thus making the moons of mars orbit strange?Chromagnum (talk) 05:37, 17 September 2009 (UTC)

I don't know the answer but I just thought you'd like to know that this site is not "wiki"; this site is called Wikipedia. A wiki is any website using wiki software. There are thousands of them.--162.84.164.115 (talk) 06:06, 17 September 2009 (UTC)

You are exactly right. Wikipedia uses wiki software but isn't wiki any more. Last time I tried to create a redirect I was not allowed to so I left it and I feel appalled by the ever increasing rules and regulations. 93.132.128.221 (talk) 06:41, 17 September 2009 (UTC)

People on Wikipedia often refer to Wikipedia as "wiki". It's not a problem. And if the meaning of the questioner is clear, don't get pedantic about picking apart the question. It doesn't help anyone and it's a jerk thing to do. It seriously does not make you look clever—much to the contrary, in fact. --98.217.14.211 (talk) 13:51, 17 September 2009 (UTC)

My appologies i was typing fast and used wiki for short wont happen again thanks for your usefull knowledge that helps me through my day to day lifeChromagnum (talk) 06:08, 17 September 2009 (UTC)

Just for kicks a site using "Wiki" software is not refered to as a wiki :) least could have given the correct answerChromagnum (talk) 06:12, 17 September 2009 (UTC)

What? Yes it is. Vimescarrot (talk) 10:45, 17 September 2009 (UTC)

Instead of a bit bucket, they have a wiki basket. Baseball Bugs ^{What's up, Doc?} carrots 06:14, 17 September 2009 (UTC)

The way I read the article, the orbits are nearly circular, which could be considered unusual, as captured objects might be expected to be significantly elliptical. Baseball Bugs ^{What's up, Doc?} carrots 06:18, 17 September 2009 (UTC)

Before we sent rockets to Mars and determined its surface nature and that of its moons close-up, i.e. when some people still thought there could be humanoid life on Mars, there was a hypothesis that Deimos and Phobos were artificial. That now seems unlikely. But the near-circular orbits appears to be a poser. Baseball Bugs ^{What's up, Doc?} carrots 06:20, 17 September 2009 (UTC)

Drilling down from your original link, you can find articles on Phobos and Deimos, each of which describes the unusual characteristics of their orbits. It appears that the expected orbit, as you ask, would be more elliptical, less aligned with the equatorial plane and possibly at a greater radius from the planet for starters. For comparison with the other moons of the solar system you may find this comparison helpful. Erector Euphonious (talk) 12:06, 17 September 2009 (UTC)

Cute animals

What evolutionary factor could have possibly made humans sympathetic to cute little animals? Also, is it possible that other animals think other species of animals are cute as well? If so...why!? -- penubag  (talk) 07:25, 17 September 2009 (UTC)

The article on cuteness is a bit short but basically what you are asking for. 93.132.128.221 (talk) 07:46, 17 September 2009 (UTC)

That article doesn't fully answer my question but it is interesting, thanks. -- penubag  (talk) 08:22, 17 September 2009 (UTC)

Seems to provide a full explanation that I can see. What do you see as a problem? It's fairly straightforward, infants are a bundle of problems and annoyances and we have a built-in drive to nurture them. As to other animals finding the young of another species cute don't you often see these 'cute' pictures where one animal has adopted the young of another? Dmcq (talk) 10:32, 17 September 2009 (UTC)

query? The article says "That is, humans prefer animals which exhibit pedomorphosis." I don't think this is right - Giant pandas do not have pedomorphosis. Nor do humans appear to prefer animals which retain their gills from a larval stage, is there a better term.87.102.94.154 (talk) 10:38, 17 September 2009 (UTC)

Atavism? --TammyMoet (talk) 11:20, 17 September 2009 (UTC)

Interesting, but no. Unless maybe you mean Atavistic regression as a behaviour83.100.251.196 (talk) 11:45, 17 September 2009 (UTC)

I had considered adding that to the link, actually. It's one reason why we enjoy fussing dogs and cats, especially cats, whose behaviour in the wild is completely different to their behaviour around their staff (kneading, purring, dribbling etc). --TammyMoet (talk) 13:20, 17 September 2009 (UTC)

Domesticated dogs are interesting because they are supposed to have an arrested development stuck at the 'object play' stage.[15] - which links in vaguely with the cute(likeable)=child like theory.83.100.251.196 (talk) 17:37, 17 September 2009 (UTC)

The theory is that human beings find things cute that resemble human baby characteristics becuase this illicits a caring response - such characteristics include round head, large eyes, small nose, slightly fatty build, and maybe relative lack of hair.83.100.251.196 (talk) 11:45, 17 September 2009 (UTC)

For example, little tarantulas are just darling. Ugh. I think it has to do with attractive appearance in general. Why are baby ducks cuter than baby geese? Because adult ducks are attractive and baby ducks look like miniatures of the adults. Not so much so with geese. Baseball Bugs ^{What's up, Doc?} carrots 13:15, 17 September 2009 (UTC)

I don't think there are any objectively cute animals -- it's complete and utter editorialization, much like referring to the weather as "nice" or "crummy." In those societies in which children play with furry stuffed animals, perhaps an association is made to those animals that appear similar to such a toy. In a theoretical society in which children are restricted to playing with other things, those things may then take on a "cute" factor. Another aspect would be the size of animals -- small size may ingenuinely suggest docility, such as small pythons and alligators. DRosenbach ^{(Talk | Contribs)} 13:32, 17 September 2009 (UTC)

I find baby geese pretty cute! --98.217.14.211 (talk) 22:29, 17 September 2009 (UTC)

Does sound play a factor in that too? When I hear gull chicks plaintively begging for food or calling for their mothers, I get the 'awww, the poor cute little scared, hungry thing' response. --Kurt Shaped Box (talk) 22:43, 17 September 2009 (UTC)

For a truly comprehensive examination of the "Laws of Cute", you simply have to read http://cuteoverload.com/tag/the-rules-of-cuteness/ - it's true and really funny. SteveBaker (talk) 18:16, 17 September 2009 (UTC)

Eye pain / Menstrual Cycle

My girlfriend told me today that she often gets a rather strong pain in her eye a day or so before her period. It doesn't happen every time, but whenever it does it's pretty much a failsafe predictor that she'll start in the next 12-24 hours. How can this happen? I'm really interested in what sort of mechanism could cause it. Insperatum (talk) 07:43, 17 September 2009 (UTC)

I bet her doctor could give her a much better answer than we can. It could be an eye-based migraine, it could be a coincidence, it could also be a serious problem. Seriously, ask a doctor. Matt Deres (talk) 15:48, 17 September 2009 (UTC)

Gravity at the center of a body

This is probably a classic question but if I were to drill a hypothetical hole through the diameter of a large object (like the Earth) and drop a body of mass through it, what would happen as the mass approached the center? Since gravity is acting on all angles of the mass, would it remain suspended at the center? -- penubag  (talk) 08:18, 17 September 2009 (UTC)

In the classroom case (nice, straight hole, spherical cow in a vacuum, no rotation of the planet or hole drilled right along the rotation axis), the body would accelerate exactly up to the mid point (although the acceleration would slow down smoothly), and then continue through the middle, still moving but decelerating, until it came to rest exactly on the other side of the Earth. If unstopped, it would then fall back and oscillate forever (in Newtonian physics) or for very very long (in General relativity). If you allow for air, it would fall very slowly and either soon be crushed, or come to rest at the point where the density of the atmosphere equals the density of the object. --Stephan Schulz (talk) 08:45, 17 September 2009 (UTC)

see http://en.wikipedia.org/wiki/Wikipedia:Reference_desk/Archives/Science/2009_September_11#Path_through_Earth it oscillates. 87.102.94.154 (talk) 09:04, 17 September 2009 (UTC)

Assuming that the volume of the hole << volume of the planet, you have a Harmonic oscillator. Elocute (talk) 09:49, 17 September 2009 (UTC)

I don't think you even need to make that first assumption.87.102.94.154 (talk) 10:34, 17 September 2009 (UTC)

He does plus that the density is uniform. Anyway even with that it won't be exactly harmonic as time will go slower right at the very centre even though there is no gravitational accceleration there due to gravitational time dilation never mind its greater speed there. Now that's really idealizing things. Dmcq (talk) 13:39, 17 September 2009 (UTC)

What happens if there is a large hole then?83.100.251.196 (talk) 17:24, 17 September 2009 (UTC)

If there was a big hole in the centre of the earth you'd be weightless there, unlike some wierd sects or sci fi about walking about on the inside. You feel zero gravity inside a uniform spherical shell. Dmcq (talk) 17:47, 17 September 2009 (UTC)

You're weightless inside a (big or) small hole at the centre (not anywhere inside it) - what is the difference between a large and small hole through the earth when something is dropped into it? (The hole is cylindrical - they were going to drop something down it..)83.100.251.196 (talk) 18:19, 17 September 2009 (UTC)

You are weightless everywhere inside a shell of uniform density. This is somewhat surprising, but a well-known fact. Intuitively, the larger forces from closer matter on one side side are balanced by the larger mass of the matter on the other side of the sphere. As for the second part of your question: The problem with a large hole is that a harmonic oscillator is not just any oscillator, but an oscillator where the acceleration is proportional to the distance of the oscillating mass from the zero point. This is true for a mass falling through the earth - the gravity of the outer shell cancels, so the effective mass goes down with the third power of the radius. Since gravity is an 1/r² force, two of those powers cancel, leaving a linear dependency on the radius. If you consider a big hole, what you get in the end is more or less a doughnut shape, and the relation does not work out anymore. --Stephan Schulz (talk) 18:31, 17 September 2009 (UTC)

Can I assume that you are talking about spherical holes, and me about cylindrical holes.. I thought the idea was that the earth was being treated as a Shell_theorem#Solid_spheres, and that there was a cylindrical hole (large or small) - in this case it seems likely (without doing the maths) that the net force will only be zero when the particle is inside an 'empty sphere' ie when the particle is inside a sphere or radius r (where r is also the radius of the cylinder).. In the big hole case it is interesting because whilst inside the zero force void the speed will be constant - but when leaving that space it will experience a force (towards the centre) again.

Therefor I think that even with a big hole - the particle will still oscillate.83.100.251.196 (talk) 19:02, 17 September 2009 (UTC)

Oh yes, it will oscillate. But it will not be a harmonic oscillation. It's only harmonic if the diameter of the (cylindrical) hole is negligible. --Stephan Schulz (talk) 19:26, 17 September 2009 (UTC)

For the record the shape of the hole is irrelevant, if it is large enough to cause non-negligible deviations in the gravitational field of the large body in question from the gravitational field of a solid sphere, at any point along the particles path, then the oscillation will no longer be harmonic. My earlier statement was made with the same interpretation that you hold, one of a solid sphere with a cylindrical channel cut through it. Elocute (talk) 01:56, 18 September 2009 (UTC)

Very sorry - I totally failed to notice that you wrote "harmonic" - I just saw the oscillator part. Hence my stupid questions. Sorry again.83.100.251.196 (talk) 11:09, 18 September 2009 (UTC)

I need to ask a question on the maths desk arising from this, please feel free to look at it and answer if you can, thanks.83.100.251.196 (talk) 19:08, 17 September 2009 (UTC)

Thanks for the replies, but if there were air resistance what would end up happening? -- penubag  (talk) 08:08, 19 September 2009 (UTC)

See above. Any kind os permanent resistance will dampen the oscillation. If you assume the air pressure hat would "naturally" form in such a whole, the air would soon become so dense that it would crush and/or float your oscillating body. --Stephan Schulz (talk) 08:30, 19 September 2009 (UTC)

Finding a vein: legs, arms and the jugular

At the execution attempt of Romell Broom, why did they try to find for two hours - without success - a vein in the legs or arms? Isn't it much easier to use the jugular?--Quest09 (talk) 09:12, 17 September 2009 (UTC)

It's (nearly) always possible for someone with adequate medical training to obtain venous access. But it's likely that [1] since most physicians consider it unethical to take part in a medical capacity in an execution, those trying to gain IV access had little experience doing so, and that [2] they would have had training only in accessing peripheral veins rather than central ones. And it's likely that [3] the Ohio state execution protocol makes no allowance for use of the jugular vein, and that the executioners would not be allowed to improvise in that way. - Nunh-huh 09:26, 17 September 2009 (UTC)

Anti - Perspirant causes Cancer

A while ago there was a mail doing the rounds claiming that the use of anti-perspirants could be a major factor in womans breast cancer as wel as other cancers of the glands. It was based upon the "Fact" that the armpit and the area behind the knees are the major areas where toxins are excreted through the sweat glands. This process is then infuanced by the use of anti-persperants which prevents this cleansing action, toxins build up and causes cancers. Specificaly in the chest/breast area !

How true is this and ho save is the use of anti-perspirants?

Regards ~~

Snopes flags this as "undetermined"--Shantavira|^{feed me} 11:46, 17 September 2009 (UTC)

If the word "toxins" is involved, then it is likely bullshit. No actual scientific study in a peer-reviewed journal would use such terminology. --Jayron32 12:09, 17 September 2009 (UTC)

To be fair, 'toxins' is the sort of word used by 'science reporters' when summarizing and relaying the results of genuine scientific papers (which those reporters may or may not fully understand themselves) to the lay public. That said, the links provided by Shantavira to Snopes and to Nanonic to our own articles contain the relevant references. My personal take on it is that a) the body doesn't use sweat to get rid of any significant amount of cytotoxic material; b) the lymph nodes don't drain fluid (toxic or otherwise) through the sweat glands; and c) tumours of the breast virtually never start in the lymph nodes, but rather originate in other tissues and then metastasize (migrate) to the lymphatic system. It's a creative hypothesis, but one unsupported by convincing evidence. TenOfAllTrades(talk) 12:40, 17 September 2009 (UTC)

See Deodorant#Aluminium neurotoxicity and Deodorant#Cancer. Nanonic (talk) 12:21, 17 September 2009 (UTC)

Safety of soy protein extraction using hexane

There are alarming claims on the Internet about the safety of using hexane to extract soy protein. Based on the evidence available and what we know about the chemical, what would be a scientifically-sound risk assessment of the practice?

I'm not aware of the specific claims, buy vegetable oil has been extracted using hexane for many years, - if there were any ill effects it should have shown up by now.

Also hexane is used to extract fat and oil from soy, not the protein.

I can't find any realistic claims of dangers amongst all the scaremongering - most of the sources appear to be based on cornucopia.com which found hexane at 21ppm. (And this bears all the hallmarks of scaremongering by an interested party to easily worried organic food people.)

If 21ppm was remotely harmful the FDA or similar would have acted ages ago. I hope.83.100.251.196 (talk) 17:22, 17 September 2009 (UTC)

See this [16] a recommended limit of 50ppm, and no adverse effects reported at 500ppm long term exposure. However I think that is for atmospheric exposure, though 83.100.251.196 (talk) 18:39, 17 September 2009 (UTC)

[17] gives some FDA standards for hexane for food residues - typically requiring less than 25ppm.83.100.251.196 (talk) 18:46, 17 September 2009 (UTC)

The same source states that hexane is GRAS Generally recognized as safe for these processes. So at current levels of understanding I would assume that there is no particular danger from soy bean.83.100.251.196 (talk) 18:48, 17 September 2009 (UTC)

A greater danger comes to those that work with hexane.83.100.251.196 (talk) 18:53, 17 September 2009 (UTC)

(I don't know if alternatives exist - possibly supercritical carbon dioxide extraction might work, and work eliminate these problems.)

The main problem here is that practically all the population of many countries is exposed to hexane processed foods (vegetable oils excluding cold pressed, margarine, also animal feed) - if there was a general effect such as mental retardation in adults, it wouldn't be easy to show, since practically everyone would have it...83.100.251.196 (talk) 19:53, 17 September 2009 (UTC)

Pure Hexane itself is probably pretty safe, but if it is contaminated with benzene or other substances, it could be hazardous. Graeme Bartlett (talk) 06:15, 18 September 2009 (UTC)

Hexane#Toxicity has some good info. Aligns with what I've read in chemical-safety publications and chats with other chemists. DMacks (talk) 06:44, 18 September 2009 (UTC)

Why not extract with heptane to avoid any chronic side-effects? Anyway, solvent extraction is done all the time -- for your prescription drugs, your vitamins, for the phosphoric acid they use to acidify your coke, etc. Hexane has a lower boiling point than water or ethanol, so what you do next is prolly extract into ethanol and then distill the hexane off. I imagine in the food industry has pretty high standards. John Riemann Soong (talk) 13:45, 18 September 2009 (UTC)

They usually just evaporate the hexane extract leaving the oil behind, a vacuum will also be applied to aid the process. No ethanol in vegetable oil extraction not entirely true - may be used - but in a different process. (This is a simplification) It's different for stuff like flavourings etc. were ethanol is used.

There's an example here using hexane and ethanol for extraction [18], ethanol for oil has been tried - but basically doesn't work [19] (my synopsis) - however getting more complicated it may work [20] (here they 'precipitate' the oil out of the extract as micelles. there are issues with ethanol extracting stuff that hexane doesn't..)83.100.251.196 (talk)

This is all off-topic, and simplified - search the web for "vegetable oil ethanol extraction" or similar, for the full picture.83.100.251.196 (talk) 15:40, 18 September 2009 (UTC)

Good question - actually I've just tagged hexane with "citation needed" as regards heptane as a replacement - it's not clear to me that heptane would actually be any better. Specifically I suspect the reason why heptane may appear a better choice on the surface is that it is relatively unused - in contrast to hexane which has vast amounts of literature relating to its toxicity - it could turn out that heptane is no better - but simply that toxicity data does not yet exist.83.100.251.196 (talk) 14:13, 18 September 2009 (UTC)

eg http://www.cdc.gov/niosh/pel88/142-82.html

the ACGIH concluded that heptane was more acutely toxic than hexane. The ACGIH therefore recommended limits for heptane that are somewhat lower than the limits for the hexane isomers."

chronic toxicity not mentioned.

also:

..because NIOSH believes that "it would be incorrect to conclude that the neurotoxic properties ascribed to n-hexane are unique to this compound [n-hexane]. Other alkanes or related chemicals [such as heptane] that are ultimately metabolized to gamma diketone may have similar toxicity

OSHA is the organisation that thinks hexane is uniquely toxic (or did-they may have changed there minds) - there's more evidence for exactly the same sort of toxic effects from heptane as found from hexane occuring at basically the same concentrations.

I think I will delete the claim at hexane.83.100.251.196 ([[User

talk:83.100.251.196|talk]]) 14:18, 18 September 2009 (UTC)

What about branched isomers? John Riemann Soong (talk) 16:32, 18 September 2009 (UTC)

isohexane [21] 83.100.251.196 (talk) 17:39, 18 September 2009 (UTC)

Would it still be metabolised into gamma-diketone? John Riemann Soong (talk) 20:12, 18 September 2009 (UTC)

It can't be since the 2 carbon (of 2,4 diketone) is tertiary. (assuming isohexane is 2methyl pentane)

For the 'isohexane' mixture of isomers only 3methylpentane can do this without rearrangement. I don't know what exactly will happen.83.100.251.196 (talk) 21:43, 18 September 2009 (UTC)

As far as I know, most alkanes (hexane, heptane, etc.) are pretty much biologically inert as far as metabolism is concerned, and whatever toxicity they might have is caused by their physical properties (hydrophobic properties, vapor pressure, etc.), mainly at pretty significant doses. So we don't really have to worry about traces of hexane in the food we eat. A bigger danger (as 83.100 pointed out) is to the workers that work with hexane -- and that danger mostly comes from hexane's extremely high flammability. :-) FWiW 98.234.126.251 (talk) 02:40, 19 September 2009 (UTC)

Unknown beetle

Hi!

During a travel in Minneapolis, I saw the beetle on the picture. The problem is, that I don't know which beetle it is. Can someone help me?

Regards, Tanzania (talk) 14:13, 17 September 2009 (UTC)

Looks like a Three-lined potato beetle, Lema trilinea. --Sean 18:09, 17 September 2009 (UTC)

I see they've renamed it to Lema daturaphila. There are lots of beautiful pictures of them online. --Sean 18:15, 17 September 2009 (UTC)

Or Lema trivittata. It's pure hubris for a non-expert like me to even be guessing on exact species; what's that line about God and beetles? --Sean 18:33, 17 September 2009 (UTC)

It does look as one of the pictures you linked to. There are no article about the specie or the genus on english wikipedia, am I right? Tanzania (talk) 19:47, 17 September 2009 (UTC)

But all the species you wrote look the same... Are they different? Tanzania (talk) 19:56, 17 September 2009 (UTC)

All three names are for the same species, here's even more images [22]

Though this [23] suggests there are sub-species -- 83.100.251.196

Thank you! Think I'd better create articles about the subfamilies etc..

Tanzania (talk) 20:30, 17 September 2009 (UTC)

Good idea (but I'd recommend only covering down to the species level - subspecies can be dealt with in the main species article !83.100.251.196 (talk) 20:41, 17 September 2009 (UTC)

(EC) Presumably they are different in some way, or they would all be the same species. I really don't know anything about them, I just googled "Template:Websearch" and saw them on Google Image Search. Before that I tried some of the bug ID sites, but wasn't successful (none of them are very good, that I've found). --Sean 20:34, 17 September 2009 (UTC)

on gas cylinders

hi,

when we ignite a gas stove, we obtain a flame. But there is no possibility of the tube connecting the stove and the cylinder, catching fire thereby leading to the explotion of the cylinder. Why is it so? What is the mechanism behind it?

Combustion requires oxygen (among other things). With a pressurized gas tank, though, only gas is flowing through the tube and only toward the outside air. Thus, there's no oxygen in the tube via the tank nor is there oxygen in the tube via atmospheric mixing. Combustion, therefore, cannot happen. — Lomn 15:21, 17 September 2009 (UTC)

I have an uncle who almost died from a gas explosion like this. Off course, like Lomn said, the stove can't ignite it, but an open fireplace ignited it and the pipe burst into flames and he had to leg it.--Patton123 (talk) 17:23, 17 September 2009 (UTC)

pervaginal examination

• This question has been removed as it may be a request for medical advice. Wikipedia does not give medical advice because there is no guarantee that our advice would be accurate or relate to you and your symptoms. We simply cannot be an alternative to visiting the appropriate health professional, so we implore you to try them instead. If this is not a request for medical advice, please explain what you meant to ask, either here or at the talk page discussion (if a link was provided).

Please see your medical professional. Wikipedia is not able to answer your request for medical advice. Nimur (talk) 20:39, 17 September 2009 (UTC)

Do chimps sit?

You know how humans sit, as in knees & butt making 2 right angles. Do you ever see any other animals doing that?

Many apes (chimps gorillas whatever) will 'sit on their haunches' (butt to ankle) but I've rarely seen them sitting on a tree stump etc in a 'right angled' pose.

So have we evolved to sit, or is sitting a handy convenience that for some reason no other animal takes advantage of?

Discuss... --Mortice (talk) 21:52, 17 September 2009 (UTC)

I don't know the answer, but one note that I think has to be made is that we have not evolved from chimps, but rather both we and chimps have a common ancestor. I realize that you didn't say that we evolved from chimps, but a reader might mistakenly get that impression. Bus stop (talk) 22:04, 17 September 2009 (UTC)

Well, all of these are pretty fun. The closest I saw was this one, which is essentially what you're looking for, although it's a barbary ape, i.e. not actually an ape. This, also, is... interesting. I'm no expert on ape movement, but I did just see a bunch at the zoo. You'll notice that (Gorillas, anyway) swing their legs when differently than we do, indicating a different comfort range of motion. Also, don't forget, we have chairs. They have rocks and logs. Some of them are okay, but sitting on a flat rock with your legs at right angles? The backs of your upper legs can really start to hurt and have decreased blood flow, especially if you've got long/heavy legs, as a number of monkeys and apes do (relative to us). ~ Amory (user • talk • contribs) 22:35, 17 September 2009 (UTC)

Thanks for the pics - the majority of those are what I refer to as 'sitting on haunches', and you picked out a few where they're sitting with legs splayed. Perhaps it's really not in their anatomy to 'sit' as we do - and by 'their' do I really mean all creatures other than Man? People seem to 'sit' very naturally (although I've seen some ethnicities are more likely to 'sit on haunches' than others). Is there anything in the evolutionary path which brings us to it, or an evolutionary step-change, or just a more modern social trend to sitting? --Mortice (talk) 18:08, 18 September 2009 (UTC)

Global warming

What makes us think it is human caused? How much greenhouse gas do human produce and how much is produced by natural processes? The charts I have seen only show temperatures slightly higher than the medieval warm period. Is this true? How do we know it isn't the Sun's absense of sun spots? Sorry just don't know much about it.--92.251.140.93 (talk) 22:30, 17 September 2009 (UTC)

The Sun's low activity only started in the last year or so, global warming pre-dates it. Temperatures aren't increasing to higher levels than they have been in the past, but they are doing so faster. --Tango (talk) 22:37, 17 September 2009 (UTC)

Read attribution of global warming and our main article on global warming. Essentially, there is no doubt that the increase in GHGs is man-made - it's shown by simple mass balance computations and confirmed by changes in the ratio of carbon isotopes - see Suess effect. Yes, our contribution is small compared to the overall flows in the carbon cycle, but it is actually larger than the overall increase (some natural carbon sinks become temporarily more efficient with increased atmospheric CO2). It's the difference between a circulation pump and filling the pool. We also understand the basic effect of GHG's from first principles, and there is no serious doubt about that - if the Greenhouse effect did not work, we would all freeze to death. What is more tricky is the modeling of second-order effects and feedbacks. However, even there we have good models that allow us to make educated predictions, and that are supported by a large consensus (see Scientific opinion on climate change). --Stephan Schulz (talk) 22:59, 17 September 2009 (UTC)

The combined plot above (showing records back to a nominal 500 million years ago) should be examined with caution. Particularly worth noting is that the time axis is a logarithmic scale; the apparently gentle sloping increase of the last few decades would be a vertical line if it occurred nearly anywhere else on the graph. TenOfAllTrades(talk) 15:55, 18 September 2009 (UTC)

File:Co2-temperature-plot.svg

The most convincing evidence for the layperson is to examine a graph of temperature over the past few hundred thousand years versus the amount of CO2 in the atmosphere. The graphs are essentially identical. This essentially proves that the fluctuations we're seeing are directly related to CO2 in the atmosphere. Now - mentally zoom into that graph and look at just the last 10,000 years since human civilisation has been around...the stuff before that doesn't matter because we weren't around to care about it. Now you can see that the levels have been increasing steadily since humans became civilised - but even on that scale, the numbers are kinda similar to the worst spikes from before humans were around. The telling fact is that this graph has an arrow pointing to TODAY's CO2 levels...which are essentially "off the chart". There is no line on the graph showing that because it's happened on such a short timescale. So - now we know that (a) global temperatures track CO2 in the atmosphere very closely...and (b) that the levels have gone through the roof over the last 100 or so year. So now we have to figure out what's causing that abnormal increase in CO2 levels. Well, we know how much we're producing - we can calculate it from fossil fuel consumption - and lo and behold - the amount of the crazily abnormal increase is a really close match for the amount we're pumping into the air. Conclusion: It's all our fault. I honestly can't see a way out of that logic. SteveBaker (talk) 17:55, 18 September 2009 (UTC)

Actually, this graph is one of the things that seems to *debunk* the CO2-causes-temperature argument. I'd like to see the actual numbers, but in this graph it appears that changes in temperature *preceed* changes in CO2. Wikiant (talk) 18:02, 18 September 2009 (UTC)

I think the graph's axes are too small to show that accurately...and you have to look at the START of the temperature increase - not the peak. Look at the very start of the 350,000 and 250,000 year increases - and in both cases, you see a rather modest (blue) CO2 increase just before a huge (red) temperature increase - which the CO2 level then tracks. That suggests that the Greenhouse effect is the trigger for the temperature rise - which (once it's already shooting up) pulls the CO2 level up with it. That suggests a vicious feedback effect...which is a very possible (and vary scary) thing. SteveBaker (talk) 18:23, 18 September 2009 (UTC)

See [24] and the accompanying discussion. Dragons flight (talk) 05:02, 19 September 2009 (UTC)

There are tests one can do for (granger) causality, but again one needs the data. What gives me pause is that, every time I hear someone point out an inconsistency in the CO2-warming argument, what I hear back is not a refutation on the grounds of the argument, but an increase in the complexity of the argument. In the end, the CO2-warming argument begins to sound like a non-falsifiable hypothesis. Wikiant (talk) 18:31, 18 September 2009 (UTC)

Those tests won't be able to tease out a graph like the one above because, as steve pointed out, the is a possibility of a positive feedback effect. causality tests can't tell which one comes first, the chiken or the egg? The point is that it doesn't matter whether the CO2 is the chiken or the egg. Either way, more of one leads to more of the other. More CO2 leads to higher temperatures. Dauto (talk) 19:09, 18 September 2009 (UTC)

You are incorrect. Granger causality tests can tease out (granger) causality in the presence of positive feedback. Wikiant (talk) 20:43, 18 September 2009 (UTC)

"Despite its name, Granger causality does not imply true causality." But that's a bit besides the point. While the correlations are striking (and useful in understanding the effects of feedback), the basic "CO2 causes warming" argument is not a statistical one, but is based on simple and uncontroversial spectrographic properties of CO2. See below. --Stephan Schulz (talk) 20:58, 18 September 2009 (UTC)

Hmmm. What "inconsistencies" in the basic arguments have you heard? CO2 is nearly transparent in the visible light. The sun, at 6000K, emits mostly in the visible light. That light hits the earth and warms it. The earth is around 15K°C or so, and emits mostly in the infrared. CO2 absorbs very well in the infrared, so the infrared cannot escape directly into space, but heats up the atmosphere. If there is more CO2, this effect becomes stronger. The warmer atmosphere will emit more energy from higher altitudes (where there is less chance of interaction with GHG molecules), so that eventually a new equilibrium is reached, but at a higher temperature. That's the basic mechanism that has been understood for much longer than we can reliably measure either the temperature or the atmospheric CO2 content. See Svante Arrhenius, who predicted the effect in 1906. --Stephan Schulz (talk) 20:54, 18 September 2009 (UTC)

The Earth is substantially hotter than that. Algebraist 21:33, 18 September 2009 (UTC)

Swedish scientist/Scot scientist - the difference is only 273.15 degrees ;-). --Stephan Schulz (talk) 21:49, 18 September 2009 (UTC)

This is an example of my earlier point that it seems like the CO2-warming hypothesis is non-falsifiable. (1) "A" presents the graph as evidence that CO2 causes temperature; (2) "B" points out that changes in temperature predate changes in CO2; (3) "A" says that what's going on is a feedback and it is not possible to tease out which causes which; (4) "B" says, no there are tests that help us get at that; (5) "A" says, forget the tests, we know that... For each point that "B" raises, "A" shifts the grounds of the argument. It feels all too similar to the evolutionist-creationist debate. Wikiant (talk) 21:36, 18 September 2009 (UTC)

Oh, it's quite similar to the evolution/creation debate indeed. In both cases there is a large, coherent theory, supported by massive evidence, a near unanimous consensus among scientists, and support by all major scientific organizations. In both cases the theories are quite detailed, with a stable framework but ongoing refinements, and not fully understood by the general population. And in both cases an organized campaign uses the complexity of the issue to build straw men, misrepresent the science, and repeat long refuted arguments ad nauseam. And, btw, I never offered these graphs as evidence - exactly because their interpretation is not trivial, and they are not needed for the basic argument. Your "A" is several different As. --Stephan Schulz (talk) 22:02, 18 September 2009 (UTC)

Despite of what you said, your test doesn't work here because there is a feedback is the correct answer for your point. Your test might be able to tell us that the temperature change predates the CO2 but is a case of positive feedback that does not matter. It does not matter which one comes first because either one of them can get the feedback cycle started. Dauto (talk) 04:39, 19 September 2009 (UTC)

For those that didn't read Dragon flight's post, see What does the lag of CO2 behind temperature in ice cores tell us about global warming? and The lag between temperature and CO2. (Gore's got it right.) -Atmoz (talk) 05:07, 19 September 2009 (UTC)

Has anyone noticed that in the first graph (which is the only one with sufficient detail to show temperature variation year by year), the annual average has actually been going down for the past 4 years? Now that might be just a statistical blip, but then again, it might be the start of a cooling trend, which would contradict the "greenhouse effect" hypothesis. FWiW 98.234.126.251 (talk) 02:51, 19 September 2009 (UTC)

Greenhouse effect has been known about for a long time IIRC from secondary school chemistry class, and is the reason the earth isn't absolutely feezing, it can easily be proven by filling a bottle with CO2 and another one with O2 and putting a thermometre into each one (At least I think it was a bottle...can't quite remember) and the CO2 one turned out to heat up faster than the toehr one when left in the Sun. It's the earth getting hotter because of humans you're talking about, not hte greenhosue effect.92.251.201.218 (talk) 09:13, 19 September 2009 (UTC)

natural or something else?

Is a blind canyon related to weather or nature-made structures?69.203.157.50 (talk) 23:26, 17 September 2009 (UTC)

Our article on Canyons says nothing about "blind" ones. An article on flying in mountains describes flying into a blind canyon, and the need to be able to turn and fly back out. Presumably a canyou might be when a river runs through elevated terrain so that the heights on either side rise up. If a watercourse flows down a mountain, then the pilot might fly in at one altitude, and be unable to climb over the terrain at the point where the watercourse enters the canyou. In western movies, they often spoke of "box canyons," which let you ride in, but you could not ride out the far end, because it rose up. It is something with just one reasonable way in and out. (Good spot for an ambush). The term "blind canyon" is sometimes used as a metaphor for thought processes or organizational processes which lead to a dead end. It is a common place name. I would vote for "nature built" unless it is a metaphor. It is related to weather only in that watercourses carve out canyons over eons and precipitation, a part of weather, makes the river flow. On places with little or no rain, like Mars, wind and sand might be able to carve out canyons over a longer time span. Edison (talk) 04:22, 18 September 2009 (UTC)

Is "blind canyon" a specific place -can you link to it. I would expect there might be more than one...83.100.251.196 (talk) 14:10, 18 September 2009 (UTC)

"Blind canyon" is mentioned in the article about Lance Reventlow and an article about one other person.69.203.157.50 (talk) 15:29, 18 September 2009 (UTC)

In that context "blind canyon" is an aeronautical term, and not a geological one.83.100.251.196 (talk) 16:50, 18 September 2009 (UTC)

Weather might play a part, but I would think that it is called a blind canyon due to visibility being obstructed by the mostly vertical walls of the canyon. Also perhaps radio contact is affected by flying in a canyon. Bus stop (talk) 17:19, 18 September 2009 (UTC)

A blind/box canyon is one you can ride or walk into, but the sides are too steep to be climbed easily, and when you reach the end, it is also too steep to climb. As I said, it would typically be a geological feature carved out over thousands or millions of yearasa by the flow of water from the high end. The watercourse might have dried up or only flow intermittently.There are many such places, as shown by a Google search Edison (talk) 19:49, 18 September 2009 (UTC)

September 18

Water and the Human Body

If there was a video camera which could only film the movement of water inside people's bodies what would the footage look like of people going about their daily lives? Would it look like fluid sloshing all over the place or would it be mostly static except for arteries and veins? TheFutureAwaits (talk) 08:20, 18 September 2009 (UTC)

Given that most of the water is contained in individual cells and the bloodstream, the only "sloshing" would be water that has just been consumed or has gathered in the bladder. In the bloodstream, it would be "flowing" rather than "sloshing". Baseball Bugs ^{What's up, Doc?} carrots 14:04, 18 September 2009 (UTC)

Sloshing is generally a Bad Thing. To get 'sloshing', you need to have free liquid and open air in the save cavity within the body. Usually this doesn't happen (or happens rarely and is quickly remedied). You can get a mixture of gas and liquid in the upper gastrointestinal tract by swallowing air with your food or drink, or by consumption of carbonated beverages; either way, this gas is released through belching. Gas further down in the system (generated by the action of digestion) usually comes out the other end.

You can accumulate air/fluid mixtures in the digestive system if there is some sort of obstruction or bowel perforation, and in the lungs due to inflammation or inhalation of liquids. [25] shows a person with a bowel perforation. The description is on this page. The pelvic bone is visible at the bottom of the frame, the lower edge of the lungs is at the top, and the spine runs up the center. Arrowheads indicate multiple air-liquid interfaces in the bowel. TenOfAllTrades(talk) 14:31, 18 September 2009 (UTC)

Okay....um why don't we steer away from the bowels. The water in people's cells, is it moved around when someone is walking, jumping or falling? TheFutureAwaits (talk) 14:43, 18 September 2009 (UTC)

There should not be any air bubbles in cells, and the interior of cells is partly water and partly other stuff, as I recall from biology class, so you might get smooth motion of the cells themselves, in response to body movements, but no "sloshing" as such. In fact, the same presumably should hold true of the bladder and stomach - there should be no air at all in the bladder, and not much in the stomach - so you would see "rolling" as a result of change of position of the containing organ due to body movement - but no real "sloshing" in the bladder and not much in the stomach. And the rest of the body, I think, would be smoothe motion. Baseball Bugs ^{What's up, Doc?} carrots 14:46, 18 September 2009 (UTC)

In Cells tehmselves the Cytoskeleton keeps things from moving around. Or even keeps them moving. The liquid just flows around them. Even though cells are somewhat flexibile, human cells (except for a few kinds) are pretty rigid things. --212.6.123.204 (talk) 16:47, 18 September 2009 (UTC)

There are other places where fluids move around besides the circulatory system, though. Besides the contents of the digestive tract there's also bile, lymph, tears, urine, semen (for some of us), and probably others I've forgotten. However, in all cases these things are produced in small quantities and normally move slowly (with obvious exceptions), so they'd hardly be noticeable in the original poster's scenario. --Anonymous, 18:43 UTC, September 18, 2009.

Don't forget cerebrospinal fluid. As you say, though, all of those are generally small volumes, moving quite slowly relative to blood. (For CSF, you make about 500 mL (two cups) per day, and the brain and CNS hold about 150 mL (a little over half a cup). It's a modest trickle.) TenOfAllTrades(talk) 22:32, 18 September 2009 (UTC)

Energy eigenfunctions of a free particle

If someone could help me with this it'd be much appreciated - the more help I can get the better.

"Find the energy eigenfunctions ψ_E(x) for a free particle of mass m subject to the periodic boundary condition

ψ_E(x) = ψ_E(x + L).

What are the allowed values of E? What are the degeneracies of the energy levels? Comment on the limit L → ∞."

For the eigenfunctions, I think they're the f satisfying -(h²/2m)$\nabla ^{2}$f(x) = E * f(x) - working in 1 dimension.

This means our functions have to be of the form Asin(kx)+Bcos(kx) with k^2=2mE/(h^2), and the periodicity implies kL=2npi, right? In which case we can find the values of E in terms of n,L etc.

I'm not really sure if I'm at all right on this, or what the 'allowed values' are, and I'm clueless about the degeneracies too.

If anyone could walk me through some of it i'd really appreciate it!

Thanks :) Spamalert101 (talk) 12:54, 18 September 2009 (UTC)

If the boundary condition is periodic then the function (solution) must be periodic too, as you guess. But shouldn't you consider higher harmonics as part of the function. eg Function = Sum over n ( A_nsin(knx)+B_ncos(knx) ) maybe that's implicit and you already have

Your equation for k looks right.

Don't you also need to state the nature of the boundary to get a solution eg the potential energy that relates to the boundary

(h2/2m)$\nabla ^{2}$f(x) = (E-boundary energy function) * f(x) maybe you are expected to ignore this and just assume an approximate solution?

With that you can then attempt to get a full solution. But as far as you have got what you have written seems basically not wrong.83.100.251.196 (talk) 13:08, 18 September 2009 (UTC)

You've already got allowed values - these are values - from kL=2npi gives k=2npi/L so you have a range of solutions to try with n=1,2,3,4 etc - these will be your allowed values - solving for E_function for each n gives the allowed values of E (these are called the eigenvalues I think)83.100.251.196 (talk) 13:16, 18 September 2009 (UTC)

You're most of the way there. n has to be an integer, and it follows (using the equations you wrote above) that E can only have certain discrete values for a given L. The degeneracy comes from the fact that different values of A and B with the same k give different solutions with the same energy. (Only the ratio of A and B matters, since the overall scaling factor on the wave function is irrelevant.) -- BenRG (talk) 13:16, 18 September 2009 (UTC)

Does it tend to a continuous function as L goes to infinity, or something else? Spamalert101 (talk) 14:16, 18 September 2009 (UTC)

Assuming that the boundaries are potential barriers, and do not dissapear - I think part of the solution would be to make the assumption that the wavefunction goes to zero at +/- infinity. Maybe I'm missing something, but I think a little more info about the boundaries is needed...83.100.251.196 (talk) 14:28, 18 September 2009 (UTC)

83.100.251.196, you are missing the fact that there are no boundaries (Or rather the boundary condition is just periodicity and nothing else). The problem is perfectly fine the way it is stated whithout any other conditions at +- infinity os anywhere else. Dauto (talk) 15:21, 18 September 2009 (UTC)

Incinel, inkinel, ...?

I was watching an episode of World's Toughest Fixes where they were working on an aircraft. The vertical fin was attached with bolts made of a metal that sounds like inkinel ("a metal harder than steel, harder than titanium"). I tried a couple of spellings but found little on google. What is that metal? Do we have an article on it? 62.78.198.48 (talk) 18:01, 18 September 2009 (UTC)

Inconel ? 83.100.251.196 (talk) 18:16, 18 September 2009 (UTC)

Inconel is used for high temp applications. I would question why the bolts on the vertical stabilizer of an airplane would need that (unless perhaps it was supersonic), but it sounds like 83.100 might have it. Googlemeister (talk) 18:43, 18 September 2009 (UTC)

It seems like inconel has similar properties to Kovar (which is a brand-name, I believe, for particular nickel-iron-cobalt alloys). Kovar is a useful alloy because its coefficient of thermal expansion matches that of glass. It's possible that Inconel's thermal expansion matches that of the carbon-fiber, fiber-glass, or other synthetic or composite material that the vertical stabilizer is made of. It would be extremely undesirable if the metal tail portion thermally expands at a different rate than the vertical stabilizer - potentially leading to cracking, fissuring, and other disaster scenarios for an airframe. I would guess that Inconel is used for this reason, rather than its high melting point. One of the most complicated mechanical challenges in a modern airframe is making all the exotic materials (carbon fiber, phenolic paper, fiber-wrap, exotic metal alloys, plastics and other synthetics) play nice together. Remember that hardness used in lay-person-speech may not be the correct usage - they may actually be referring to a wide variety of material properties - toughness, ductility, hardness, impact strength, compressive strength, etc. Nimur (talk) 21:27, 18 September 2009 (UTC)

This search seems to confirm it http://www.google.co.uk/search?hl=en&q=inconel+boeing+767&meta=&aq=f&oq= it looks like they had problems with the standard stainless steel bolts (as well as some other parts), so went for the 'best alloy' they could get for bolts - it's probably not a specific design requirement for inconel - they just will have wanted an alloy that would be trouble free.83.100.251.196 (talk) 21:53, 18 September 2009 (UTC)

[26] ".. replacement of all H-11 steel alloy barrel nuts and bolts with Inconel nuts and bolts, which ends the repetitive inspections. " 83.100.251.196 (talk) 21:56, 18 September 2009 (UTC)

remove reproductive organs

I'm writing a book about a woman who hates her reproductive organs and wants them gone. She absolutely hates the idea of pregnancy, sex with men or any implication that her body could produce a child if she was raped or something. What scientific things could she do to either remove or destroy her reproductive organs without causing damage to herself? What medical procedures would be most efficient and safe for her to undergo to achieve this? Any and all suggestions are welcome, this book is a wacky tale so weird and wonderful ideas are welcome, as long as they actually work in real life. Thanks.

For starters, you want to read hysterectomy. --Anonymous, 18:46 UTC, September 18, 2009.

Oh, you already posted about that on the Miscellaneous Desk. Okay, it's not the same question, but... --Anon, 18:52 UTC, Sep. 18.

Yes, similar question although I thought this aspect of the question would be better suited to the science desk

Also look at Oophorectomy - remove the ovaries and there are no eggs, just like spaying female cats and dogs.  Ronhjones  ^(Talk) 20:40, 18 September 2009 (UTC)

You can sterilise a women without removing the ovaries - you just need to cut/partially remove the fallopian tubes. --Tango (talk) 01:30, 19 September 2009 (UTC)

Phalloplasty? Presumably without the other aspects of gender reassignment. Not sure about efficient, but it's certainly wacky. 84.12.138.49 (talk) 22:09, 18 September 2009 (UTC)

Tying the tubes is the way to go. The female equivalent of vasectomy. You don't want to mess around with innards too much - the more you do, the more risk of complications. Tie the tubes and leave everything else intact. Especially leave the ovaries, as the source of female hormones and such - unless you want your protagonist to develop a mustache. Baseball Bugs ^{What's up, Doc?} carrots 02:15, 19 September 2009 (UTC)

This seems like a good option. Is there a specific name for female phalloplasty or cutting the fallopian tubes which I could look up? Tempoaryrefdeskaccount (talk) 08:36, 19 September 2009 (UTC)

People's feelings change over time - it would be a serious mistake to do something irreversible even if it seemed like a good idea today. SteveBaker (talk) 02:21, 19 September 2009 (UTC)

Since the book is supposedly a fantasy, maybe instead of having them tied she could have a valve installed in each tube, which could be turned open or closed under certain circumstances. Baseball Bugs ^{What's up, Doc?} carrots 02:32, 19 September 2009 (UTC)

No, she wants any possibility of becoming pregnant gone for good. This will NEVER change. Tempoaryrefdeskaccount (talk) 08:36, 19 September 2009 (UTC)

1,2 diketones and ascorbic acid

I know 1,3-diketones rapidly convert into their enol forms because of hydrogen bond stabilisation. But what about ascorbic acid? Why is it predominantly in enol form? Here, the inductive effect seems more important than any hydrogen bonding effect (you'd have to form a four-membered ring for the alcohol proton to hydrogen bond with the ketone.) Is it carbonyl-carbonyl repulsion and also the fact that the alkene bond stabilises the carbons next to the alcohol groups? John Riemann Soong (talk) 20:20, 18 September 2009 (UTC)

very short answer - enol form includes a conjugated pi system: an enone - which gains additional stabilisation from interaction of the C=C and C=O pi systems. (also see diketone)

1,3 diketones are predominately in the enol form for this reason eg 1,3 dioxocyclohexane (cyclohexane-1,3-dione) has increased acidicity too, despite being unable to form the hydrogen bond. For unconstrained 1,3 diones the potential for hydrogen bonding (or coordination to a metal) is 'icing on the cake'.83.100.251.196 (talk) 23:45, 18 September 2009 (UTC)

Natural walking speed?

Hi. I know that I swing my arms while walking, kind of like a pendulum. The swinging of my arms is coordinated, more or less, with the speed of my gait. (The right arm goes forward as the left leg steps forward.) I also know that a pendulum has, at least at a decent first approximation, a natural period that depends on the pendulum's length. Therefore, since my arms are of fixed length, they must have a natural period. Therefore, I have a natural walking speed determined by the lengths of my arms.

Does that make any sense? If so, do people tend to walk at this pace, or not? Would it be more efficient if we did? -GTBacchus^(talk) 23:38, 18 September 2009 (UTC)

yes it makes sense - but I don't think that the arms are free oscillators - specifically consider the rotating motion of the hips (and to a lesser extent torso) as you walk (eg think about those 'speed walkers' at the olympics) - so the motion of the arms, can serve also to provide a small amount of additional thrust or drive to the walking motion. I'm sure a human locomotion expert will be along soon>.83.100.251.196 (talk) 23:50, 18 September 2009 (UTC)

Clarify - it's not clear to me whether the arm motions helps thrust, or serves to reduce impulse or control balance when walking.. It does seem that the movement of the arms is related to walking motion and is muscular in nature [27], nor is it clear whether this reflex muscle motion of the arms is helpful, or an evolutionary throwback to quadrupeds , or a safety mechanism, or a bit of all. [28]83.100.251.196 (talk) 00:37, 19 September 2009 (UTC)

This seems convincing to me:

During rhythmic movement, arm activity contributes to the neural excitation of leg muscles. These observations are consistent with the emergence of human bipedalism and nonhuman primate arboreal quadrupedal walking.[29]

This seems to confirm that swinging arms is beneficial to reducing impulsive forces:

Among measures of gait mechanics, vertical ground reaction moment was most affected by arm swinging and increased by 63 per cent without it. Walking with opposite-to-normal arm phasing required minimal shoulder effort but magnified the ground reaction moment, causing metabolic rate to increase by 26 per cent. Passive dynamics appear to make arm swinging easy, while indirect benefits from reduced vertical moments make it worthwhile overall.[30]

Also from the same place "The shoulder muscles contribute to active swinging (Fernandez-Ballesteros et al. 1965)" see link above.83.100.251.196 (talk) 00:45, 19 September 2009 (UTC)

After all that sigh see [31]

..A vast majority of people exhibited an actual angular velocity exceeding the expected theoretical angular velocity calculated for a virtual pendulum of similar mass and length characteristics..

This suggests that people swing their arms faster than that expected from a pendulum, but doesn't answer if it would be more efficient to walk slower.83.100.251.196 (talk) 00:50, 19 September 2009 (UTC)

You might find the graph: figure 8.19 page 212 "Muscles, reflexes, and locomotion" by Thomas A. McMahon [32] helpful - note that at below 5mph (a good walking speed) that energy use is not linear with speed (ie not E=k x Speed ) - but that the energy use remains almost constant for motion between 1 and 5 mph - though it does decrease a little at lower speeds - the obvious conclusion to this is that it is not more efficient to walk slower than a standard walking pace (assuming a power=force x velocity law).83.100.251.196 (talk) 00:58, 19 September 2009 (UTC)

September 19

Alcohol by volume myths

In college a friend told me that the difference between 3.2% ABV beer and 4.5% (or whatever other beer is) was very small and only amounted to a difference of a beer per case. After doing the math though, this seems clearly untrue (it should take 2 three-percent beers to equal one six-percent). First, is my math reasoning correct and if I am, what is the origin of this myth? I've heard it from lots of people but the math seems easy (double the percent, double the amount). I need help knowing where people are making the mistake.

Well, let's see. there are 24 beers in a case and there are 12oz in a beer, then that is 288oz of liquid per case. For a 3.2% alcohol beer, that is 9.2 oz of alcohol per case and 0.38oz of alcohol per beer. So the "extra beer" in this exact case would be in increments of 0.38oz of pure ethanol...follow me? Let's look at the 4.5% case, it has 13oz of alcohol per case. This is a difference of 3.8oz!! In terms of "extra beers" as we defined earlier, that is 10 more beers! Looks like the difference is bigger than even I thought before I walked myself thought it.Mrdeath5493 (talk) 03:10, 19 September 2009 (UTC)

Now after doing some more math I see that if you want to find a rough one "extra beer" beer increment then multiply the ABV of any beer by 0.04 (4%) and that represents the 1 beer "step." So for the previous example if I multiply 3.2% by 0.04 I get 0.128ABV...this means that every 0.128% ABV difference between my reference beer and a different one represents an "extra beer." So, looking at the previous example I can just say 4.5-3.2 = 1.3% abv difference. 1.3/0.128 = ~10 extra beers. Cheers!Mrdeath5493 (talk) 03:20, 19 September 2009 (UTC)

As far as I can tell, you're absolutely correct and I don't know why people would say it's 1 beer worth ((4.5/3.2)*24 = 33.75 beers, so about 10 extra per case of 24). There are other things to take into account besides just the amount of alcohol when considering how drunk someone will get, for example you'll get more drunk on an empty stomach. However that seems to work in the favor of the higher alcohol beer, since you'll have less non-alcohol stuff in you for the same amount of alcohol. Maybe it has to do with perception? How drunk people act might be related to how drunk they think they should be, so if they've had more beers they might feel more drunk even if they've had less total alcohol? Rckrone (talk) 03:44, 19 September 2009 (UTC)

Thank you for the responses. I agree, I don't understand how people believed it was less. Thank for confirming that my math was right. Part of my question is how others could have come to the opposite conclusion. I wonder now if it was due to someone using addition and not multiplication on the numbers. Although even after doing those numbers it doesn't make sense. Does anyone else have any info on the myth (thank you for confirming those numbers are right).

Alkene Nomenclature

Hello. Is it internationally acceptable to name 1-alkenes larger than propene with one carbon double bond by simply their parent chain? For example, could 1-butene be simply called butene since there are no other isomers? Thanks in advance. --Mayfare (talk) 02:27, 19 September 2009 (UTC)

There's also 2-butene (with cis and trans isomers) and isobutene. You should stick with calling 1-butene by its proper name, and not just "butene" -- the latter could be any of 4 different things. 98.234.126.251 (talk) 02:59, 19 September 2009 (UTC)

There's also cyclobutane and methylcyclopropane which are isomers of butene (though, not themselves alkenes). And to confirm the above response, the name "butene" is ambiguous, because it does not indicate where the double bond occurs. You would need to specify 1-butene or 2-butene. For shorter chains (propene, ethene), there is exactly 1 version of the molecule, so it does not have to be numbered, because "propene" and "ethene" can ONLY be one structure. --Jayron32 05:55, 19 September 2009 (UTC)

Just a small addition, the IUPAC mane is actually but-1-ene. Rkr1991 ^{(Wanna chat?)} 07:47, 19 September 2009 (UTC)

Does a knife wound to the stomach cause immediate death?

I've just watched the high-quality film Faster Pussycat! Kill! Kill! on TCM. In the course of almost every member of the cast getting murdered, the cute girl with the Italian accent gets stabbed three times in the abdomen and dies immediately.

Would this happen in real life? Assuming a major abdominal artery was severed, how long would it take to bleed out sufficient to lose consciousness? Alternatively, how near the ribcage would the knifeblow need to be to hit the solar plexus and would that produce immediate death? (This is not a homework question :) Franamax (talk) 07:40, 19 September 2009 (UTC)

Depends on where you stabbed and how big the knife was. It's very possible it could happen immediately, for example bullets cause almost instant death if they hit certain areas of the body and they are about as damaging as a knife.--Patton123 (talk) 09:04, 19 September 2009 (UTC)

Genetically engineered corn seed

What would be the impact of genetically engineered corn seed that required a proprietary germination activator and had a proprietary terminator gene if it became dominant? -- Taxa (talk) 09:14, 19 September 2009 (UTC)