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

January 3

What is it eating?

Chewing on something?

This Nestor meridionalis meridionalis of the South Island of New Zealand was featured on the Main Page in the "Did You Know..?" section. When I first saw the photo, I thought it was eating a snake and I was consequently inclined to start a civilization; but on closer inspection, I found that the parrot in question doesn't eat snake. I'm not too sure, but that doesn't look like a Longhorn beetle grub, or a flower bud, or anything identifiable to me (maybe a melon fragment?). So, what is it eating? Nimur (talk) 04:43, 3 January 2009 (UTC)

Looks like a piece of capsicum to me.Mattopaedia (talk) 05:09, 3 January 2009 (UTC)

Given that New Zealand doesn't have snakes [1] and they would be another serious danger to our wildlife, it's a rather good thing it isn't eating one. Even more so on Stewart Island#Fauna. Nil Einne (talk) 05:29, 3 January 2009 (UTC)

Are we sure this is a wild parrot? Perhaps it's someone's pet and it's chewing on a red plastic toy of some kind? Just think of the kind of lens/camera you'd need to get that kind of a shot of a wild parrot - it doesn't seem very likely to me. But this is Wikipedia - we're a collection of real people, not some anonymous corporation. Hence you can go to the information page for the photo (just click on it) - look at the 'history' tab and see who posted the photo. Now you can go to that person's talk page and politely ask them all about their photo. This might not work - but on the whole we're a pretty friendly & helpful bunch here and I'm sure the photographer will be only too happy to talk about their (now very famous) picture. SteveBaker (talk) 12:54, 3 January 2009 (UTC)

Done. But again, it really looks like a slice of capsicum to me. Mattopaedia (talk) 14:54, 3 January 2009 (UTC)

This picture seems to have a circuitous history. I saw the exchange on the picture's most recent editor's talk page, and then followed the trail back to the original Commons entry, which was created by the Flickr upload bot. The description's link to Flickr appears to be invalid, but searching Flickr yielded what appears to be the original photo: [2]. HTH. --Scray (talk) 18:09, 3 January 2009 (UTC)

BTW, it's not obvious to me that the Creative Commons license was applied properly by the Flickr user to that photo, as required for use of that bot, but I am no copyvio expert. --Scray (talk) 18:15, 3 January 2009 (UTC)

Hmm why did you need to search flickr? The photo clearly identified the flickr source for a while. I followed the source before I posted my first message and I just checked, it's still there and there's no sign from the commons history it was ever removed Nil Einne (talk) 16:08, 4 January 2009 (UTC)

Done? You do realise this photo came from flickr right? I don't see any comments on the flickr page. Or did you PM? P.S. Personally I'm more inclined to believe it's some part of a native plant although I can't say what Nil Einne (talk) 16:08, 4 January 2009 (UTC)

Nowadays, I don't think many people have kākā as pets (not counting those in zoos or being looked after by DOC staff of course). I'm not even sure if it's legal. I don't think DOC will take kindly to people catching them and I'm not aware of any population of domesticated kākās. Also bear in mind most NZ birds are fairly tame, one of their problems given the lack of predators during most of their past. This bird was on Rakiura as I mentioned above so it's unlikely to have encountered much to scare it. (And it's also more likely you'll actually spot one). Of course you still need a decent camera and to be a decent photographer but these are becoming more common in this digital age. The photographer seems to be an extremely experience wildlife photographer anyway Nil Einne (talk) 16:01, 4 January 2009 (UTC)

AFAIK, it's legal to keep any 'pre ban' parrot (or its captive-bred offspring) as a pet. Even hand-fed Keas (which must be the ultimate 'difficult' pet) are available to buy, though I've only ever personally seen two advertised for sale in 15 years or so... --Kurt Shaped Box (talk) 01:17, 5 January 2009 (UTC)

Yes that wouldn't surprise me. Do domesticated/captive bred kākās exist? I guess there's probably some although perhaps they're even more rare then keas (when I searched I couldn't find any references) Nil Einne (talk) 11:54, 8 January 2009 (UTC)

According to the photographer, the picture was shot in the wild on Stewart Island; using, as per exif metadata, a Canon EOS 20D + the Canon 100-400mm USM IS telephoto lens. Here is another picture of possibly the same bird with something else in its beak. (By the way, the image license {{cc-by-2.0}} seems fine to me) Abecedare (talk) 00:13, 4 January 2009 (UTC)

Could it be a piece of fruit rind/peel? Perhaps the photographer was feeding it in order to get a good shot? --Kurt Shaped Box (talk) 16:12, 4 January 2009 (UTC)

Stick of rhubarb? Size looks about right. XLerate (talk) 21:19, 4 January 2009 (UTC)

Could it be part of a fuchsia flower? Tree fuchsias are plentiful on Rakiura. dramatic (talk) 22:12, 4 January 2009 (UTC)

I think that rhubarb is supposed to be toxic to parrots. Well, it's one of those 'common knowledge' things that you get told when you first purchase a psittacine, at least. --Kurt Shaped Box (talk) 01:04, 5 January 2009 (UTC)

Well Rhubarb is toxic to humans, particularly the leaves so it wouldn't surprise me if toxic enough to parrots that it's a bad idea to give it to them Nil Einne (talk) 11:51, 8 January 2009 (UTC)

The photographer says he thinks it was a plum [3] Nil Einne (talk) 11:57, 8 January 2009 (UTC)

Do we have any defense at all against meteors, black holes, etc.?

Like, big ones! In all seriousness, if astronomers detected a continent sized meteor headed our way with say, a year's warning, -couldn't we do something? Or if a black hole was heading our way couldn't we use some kind of antimatter type force to push it towards the moon? Or for that matter, if the moon ever broke free (from a black hole?) and started slowly drifting towards us, could we use some greater force to fastly push it away? When our sun expands during it's death throes, how will life forms of that era deal with it?--Dr. Carefree (talk) 09:49, 3 January 2009 (UTC)

No problem. We have loads of asteroid deflection strategies.--Shantavira|^{feed me} 10:15, 3 January 2009 (UTC)

Um what? Antimatter type force? Our current ability to produce antimatter is very limited and our ability to use it for practical purposes almost non-existant. And I'm not quite certain what the use of pushing a blackhole to the moon is. Plus the concept of us moving a black hole anytime soon, if ever, seem absurd to me. As to what humans will do, billions of years from now if they still exist and live on earth, I don't think many people have given it that serious thought although I'm sure there's something in science fiction Nil Einne (talk) 10:51, 3 January 2009 (UTC)

In practical terms, not only do we have no defense - we don't truly know what form that defense should take (because we don't know enough about the meteors themselves) and we don't have the ability to detect meteors early enough to make a difference.

Let's look at those problems individually:

• Detection: With a large mass on a trajectory that's pointing it at us, the earlier we do something, the easier it is. To take an extreme example: Suppose we only have a few minutes warning...we might have to try to deflect a meteor when it's one earth diameter away from hitting us square-on at the equator...we'd have to bend it's path by 30 degrees to make it miss us instead. To deflect a mountain moving at a thousand miles a second through an angle of 30 degrees in just a few seconds would probably take more energy than we have on the entire planet - it truly can't be done. However, if we know that the meteor is a threat (say) 20 years before it hits us - then the amount of deflection we need is a microscopic fraction of a degree and a really gentle nudge would suffice to save our planet. So early detection - and (most important) accurate orbital parameter determination - is a massive priority both because it gives us time (it might take 5 years to put together a strategy for deflecting this particular rock, building the spacecraft and getting it launched towards it's target) and it reduces the magnitude of our response.
• Analysis: There are many possible categories of threat. Comets are mostly ice. Meteors come in several varieties - some are essentially solid chunks of metal, others are solid chunks of rock, still others may be loose collections of small bolders, pebbles or even dust. Right now, we don't know which is which - which ones are the most common - whether large, dangerous objects are predominantly of one kind or another. We know (for example) that Comet Shoemaker-Levy broke up into a dozen pieces as it descended towards Jupiter - if we'd had to deflect that comet and we'd sent (say) a single large nuclear bomb then a whole range of disasterous possibilities come to mind: (a) The comet might break up before our rocket gets there and we can now only deflect one out of a dozen large, dangerous chunks. (b) Our bomb might actually do nothing more than break up the comet prematurely without deflecting it's course at all. So until we "know our enemy" - we're kinda screwed. We need to send lots of probes out to look in detail at a statistically reasonable collection of comets and meteors - and do lots of science to figure out what's out there.
• Deflection/Destruction: The problem is that breaking up a large meteor or comet without deflecting it's path doesn't help us. The total damage to the earth from a single rock that's the size of a mountain that weighs a million tonnes is precisely the same as for a million car-sized rocks weighing one tonne each or for a trillion rocks the size of basket balls weighing a few kilograms each. Simply smashing the meteor into pieces doesn't help at all! (The number of movies that get this fact wrong is truly astounding!) So we have to think in terms of deflection - not destruction. If we have enough time (see "Detection" above) then something as simple as a heavy spacecraft that flies along parallel to the course of the meteor for a few years and provides a REALLY subtle gravitational shift - might be enough. That's great because it works just as well with a flying rubble heap as it does for a mountain of nickle-iron or a million tonne dirty snowball. However, getting big, heavy things out of earth orbit and flying as fast as a meteor requires a heck of a lot of fuel and a huge amount of up-front planning. We certainly don't know about these threats early enough to do that reliably. So then we're left with hitting the thing hard with a big bomb, hitting it hard with an 'impactor' or nudging it more gently with rocket motors. None of those things will work for a flying rubble pile. For solid bodies - that'll work. We can build a probe with a rocket motor on it. Make a soft-landing onto the object and start firing our rocket. So long as the object is strong enough to take that pressure without breaking up - or without our rocket sinking into the surface or tilting sideways and deflecting the rock in the wrong direction - that could work. But it's more complicated than that if the object is spinning (as many of them are) - because now the rocket has to fire intermittantly when the rock is at the correct orientation or else the miracle of 'spin stabilisation' (which is what makes bullets fly in a nice straight line) will frustrate our efforts.

So it's safe to say that right now, we're defenseless on all three levels. Our detection ability is getting slowly better - we have surveyed some of the very largest rocks - and we're tracking their orbits. Perhaps we can now see mountain-sized rocks soon enough - but something a lot smaller than a mountain (like maybe a school-bus-sized rock) can take out a city - and we're nowhere even close to being able to track those soon enough or accurately enough. NASA have sent out probes to several meteors and comets to take a close look at them - and we've even tried firing an 'impactor' at one them...but we have a long way to go. A lot of people are thinking about deflection/destruction strategies...but no governments are building rockets and putting them into storage ready for the day when we'll need them - and funding for the entire process is distinctly lacking.

At some point we (as a species) need to seriously consider having a colony somewhere away from the Earth. There is always the possibility of the ultimate planet killer coming along that's too fast, too large, too unstable and/or too close to do anything about. Having a colony of humans living on (say) Mars with a self-sufficient life-style and a large enough gene-pool is the ultimate way to ensure the survival of the species come-what-may.

SteveBaker (talk) 12:43, 3 January 2009 (UTC)

If you'd like to learn more about it and help create "coursework", there's some activity on Wikiversity at v:Earth-impact events/Discussion, as well as an opportunity to use your imagination and research skills for colonizing off-planet at v:Lunar Boom Town. (And SteveBaker: mind if I copy over what you just wrote above? Good detail there!) --SB_Johnny | ^talk 12:56, 3 January 2009 (UTC)

All contributions to the ref desk fall under the GFDL - so long as you are using them under those same terms, you are welcome to take whatever you need. SteveBaker (talk) 13:45, 3 January 2009 (UTC)

I've copied this section to v:Earth-impact events/Discussion, if anyone wants to explore this topic in more detail. --mikeu ^talk 16:52, 7 January 2009 (UTC)

Surely it would help to break it up as small objects can be burned up in the earths atmosphere, the amount of mass burned off an object will be proportional to the surface area of the object, which dramatically increases if the object is broken up. To take my point to its logical conclusion, an asteroid of a large given mass would cause significant damage, whereas the same mass of dust colliding with the earth would most likely just flouresce in the atmosphere as it "burned". —Preceding unsigned comment added by 84.92.32.38 (talk) 14:12, 3 January 2009 (UTC)

The net kinetic energy that has to be absorbed by the Earth system (atmo included) remains exactly the same. While a single large rock would probably cause more damage (at least more localized damage) based on impact, even the distributed vaporization of a massive asteroid would be a catastrophe. A school bus sized rock, sure -- vaporize it. A dino killer? That won't work. — Lomn 14:52, 3 January 2009 (UTC)

Our main capability in asteroid defense is early warning. Here is an incomplete list of early warning systems that I found:

• Pan-STARRS a (nearly complete) telescope which will continuously survey the sky for asteroid threats
• Near Earth Asteroid Tracking (NEAT) An organization which has several dedicated telescopes for asteroid detection and tracking.
• Spaceguard, a loose affiliation of asteroid detection programs/enthusiasts (including a formal program at NASA).
• Lincoln Near-Earth Asteroid Research (LINEAR) a NASA/USAF/MIT joint project for asteroid detection/tracking
• Lowell Observatory Near-Earth-Object Search (LONEOS) a completed 15-year project which detected hundreds of asteroids.
• Minor Planet Center an organization which is the recognized official center for collecting and publishing orbit data about all known asteroids and comets.
• Catalina Sky Survey another sky survey designed to identify asteroids.
• Spacewatch an University of Arizona program to discover near earth objects.
• Near Earth Object Program (NEOP) a NASA effort to study the list of known asteroids and determine the impact risk.

We currently know of around 5500 (see the NEOP page) Near Earth Objects, and hundreds more are being discovered every year. So as you can see, we humans have actually put a fair amount of effort into detecting impact threats from space. No one has ever tested any potential asteroid deflection systems, but as Steve says, early detection is key. --Bmk (talk) 15:44, 3 January 2009 (UTC)

That doesn't seem quite right... if gazillions of little pieces vaporize in the atmosphere or even hit the earth (somewhat more slowed down by atmospheric friction), they wouldn't also vaporize large amounts of actual earth materials as well (which would cause snowstorms in Havana, etc.). Am I missing something? --SB_Johnny | ^talk 15:33, 3 January 2009 (UTC)

This is little as in much smaller than a mountain, not little as in the size of a pebble. The pieces will still be much too large to burn up in the atmosphere. — DanielLC 19:11, 5 January 2009 (UTC)

(edit conflict)A meteor the size of a continent would be larger than the Moon. The largest asteroid we know of, Ceres, is only about 1/4 the diameter of the moon, and it's big enough to be called a dwarf planet. There are plenty of other potential risks, for example a rouge star passing through the inner solar system would disrupt the trajectory of many asteroids and comets, flinging some toward Earth. The chances for a large black hole to pass through the solar system are very small, since it would be more massive than the sun but smaller than New York. Small black holes could evaporate to Hawking radiation. Remember that the asteroid/comet that probably caused the Cretaceous-Tertiary extinction (the one that killed the dinosaurs) was only about 15 km (9 miles) in diameter. As for the sun expanding, we could maybe move to Mars, but chances are we won't even survive that long. Most estimates predict there is a "high probability" for us to become extinct within the next three million years or so. Anyway, an asteroid bigger than, say, Lake of the Woods, would probably crash through the Earth's crust, exposing its mantle, causing further problems. Anyway, there are plenty of other potential doomsday events that could affect us in the near future (try exitmundi, [warning, popups]), and many of those pose a larger threat to us than the likelihood of an asteroid hitting Earth (which will, with 100% probability, eventually happen). In fact, one potentially catastrophic scenario is already unfolding, and could affect us in our lifetime, yet many are refusing to do anything about it. It's called global warming. ~AH1^(TCU) 15:35, 3 January 2009 (UTC)

The sun won't just slowly expand to engulf the earth - it'll put out huge pulses of hard radiation and do all sorts of other ill-behaved things along the way. There is probably no place in the solar system where we could survive that event. However, the sun blowing up is a fairly predictable event. We can give a fairly accurate prediction as to when that'll happen - and doubtless if our ancestors survive that long - they'll know to a very accurate degree when this is going to happen. So they'd have time to do something to escape to another solar system. The problem with meteors and comets is that they are more random - and the best response is to try to deflect them somehow. We'll certainly have a few thousand or even millions of years notice that the sun is going to give up on us - but we'd be lucky to get 20 years notice of an earth-smasher en route. Black holes are not worth bothering about - there are no big-but-slow ones nearby - and we don't care too much about small ones. Fast-but-big ones are impossible to deal with - if one of those comes by, there is nothing we can do. Meteors and comets are in the middle ground - they DO wipe out entire ecologies (the Dinosaurs - and there was a report out a couple of days ago suggesting that the Clovis people of North America were wiped out by a comet/meteor impact) - and we could do something about it with present-day technology if we put our minds to it. The odds of you or I personally being wiped out by one of these things is tiny - but it's one of the top risks for humanity as a species - so I think we should spend commensurate effort on solving the problem. Global warming should be higher on our list - but comet/meteor protection ought to be up there in the top ten goals of humanity over the next 100 years. SteveBaker (talk) 02:31, 4 January 2009 (UTC)

We have one rock-solid defense against asteroids: Bruce Willis. —Preceding unsigned comment added by 79.122.10.173 (talk) 14:12, 4 January 2009 (UTC)

There is a new Asteroid Deflection Research Center that has been created to develop asteroid deflection technologies. You might also be interested in reading the news at the PlanetaryDefense blog. --mikeu ^talk 16:43, 7 January 2009 (UTC)

Shoemaker and Szabo took my idea already of nuclear-powered steam. -lysdexia 00:59, 9 January 2009 (UTC)

Pesticides

I was looking at pesticides recently and one thing which surprised me was the number of different products which are the same brand and seem to be the same thing.

For example there were a number of different products which were 12g/litre of Permethrin in the form of an emulsifiable concentrate, with the same total volume. Prices varied by a few cents in some instances. These were nominally intended for a different purpose, e.g. No Silverfish beetles, No cockroaches, No ants with appropriate instructions as to how much to dilute them (all with water only) and how to apply them although they sometimes gave instructions for some other purposes. Am I right that these are almost definitely the exact same thing but with a different label? Or is it likely they have other ingredients to aide in how they adhere to surfaces or whatever. There was one for spiders which was a higher concentration (50g/litre) which I can see the need for.

There were also a bunch of ready to use sprays for similar purposes most of which were 4g/litre of permethrin in the form of a ready to use liquid (why they recommended different dilutions for the concentrates but the RTU liquids are the same I'm not sure). These were the same quantity and IIRC the bottles were similar, I don't think they sprayed differently or anything. The prices varied more by about $2 or so. Similar to above, there could be differences in surfactants etc and particularly in this case what the containing liquid is although at least two of them said "Will remain active on inert surfaces for up to two months". Or is it likely these are more or less exactly the same product?

I do have photos of some of the products and you can also see them online e.g. [4] [5] [6] [7] and note they are registered as different products although under the same code HSR000265 (mentioned on the bottle) for the concentrates or HSR000263 for the RTU liquids.

Finally another thing I've noticed is certain wasp powders e.g. [8] have Permethrin in the same concentration (10g/kg or mg/g) as flea powder for carpets. Beyond perhaps difference in particle and in applicators on the bottle, am I right these are more or less the same thing? (Some are in higher concentration [9] but I'm guessing again there's little difference otherwise). Just to be clear I'm not referring to the stuff meant to be applied to pets, which are probably regulated differently (here in NZ they regulated as veterinary medicine as opposed to the carpet powder, wasp powder etc which are regulated as pesticides HSR000262).

P.S. It's possible some of the above have different cis/trans ratios for their Permethrin but any that did mention the ratio were 25:75 Nil Einne (talk) 11:55, 3 January 2009 (UTC)

It's certainly possible that the surfactants might be different for products labeled for indoor, horticultural, and veterinary uses. It's also possible that it's simply a marketing decision. I'm not sure how the regulators in NZ define the codes, but I know for the OMRI (wow, no article! OMRI rates products for the National Organic Program in the US) ratings in the US, it's a product-by-product registration. --SB_Johnny | ^talk 13:01, 3 January 2009 (UTC)

Kale

Why does kale taste so good? Does it have lots of iron or something? Because personally, I can't get enough of it. I can't understand why anyone wouldn't want to 'eat their greens'. There are people that I used to know who never eat fruit or vegetables of any kind, almost. I can understand fruit, because it's too sweet, but vegetables? No way, there's loads of good vegetables. Something like kale almost tastes better to me than any other food.--Veritable's Morgans Board (talk) 16:16, 3 January 2009 (UTC)

Our taste buds are each a little different; like human fingerprints, it's likely that no two people have the exact same taste for food. Hence, some people love the taste of certain foods more than others, because that particular food..well, arouses the taste buds, I guess you could say.

Another reason you might not be able to get enough of it is if it evokes pleasant feelings. If the first time you ate Kale was when a beloved relative served it, it may help; especially if that person is deceased and it helps you keep their memory alive. (And, if it was early enough in your childhood, you may not recall specifically that this is who served it to you first. For instance, I associate spaghetti o's with my geat grandmoth, because she always had some chef boyardee food around when I'd to see her.) It sounds like an unusual reason for something to taste good, but it's all part of how amazingly interconnnected the body is.Somebody or his brother (talk) 16:51, 3 January 2009 (UTC)

I should point out that most of what we call 'taste' is really 'smell'. Our taste buds give us only fairly crude information about flavor. (That's why things taste different - or "like cardboard" when our noses are stuffed up with a heavy cold.) SteveBaker (talk) 18:05, 3 January 2009 (UTC)

And overtly linking this to the OP, perception of smell is highly personal. This individuality is likely to be based on both experiential and genetic factors. --Scray (talk) 19:56, 3 January 2009 (UTC)

If I recall right, there's also been some research done that found something specific in dark-green vegetables (broccoli, spinach, kale, etc) that divides people. Some people are genetically far more sensitive to the taste of certain compounds in them and hence find them much more bitter (and hence more disgusting). [10] ~ mazca ^t|c 20:00, 3 January 2009 (UTC)

I'm quite convinced that's true of fish. So many people that I know will rave on about how wonderfully 'fresh' a particular lump of fish is - when I can barely taste the stuff at all - let alone determine freshness. Sushi is just kinda slimy and uninteresting for me - but my wife is a fanatic for the stuff - detecting amazingly subtle differences between one restaurant and the other. On the other hand - I'm pretty good at identifying types of wine and beer - so my taste mechanism obviously works well at some level. We know of all sorts of genetic differences that cause 12 different varieties of color-blindness - why should we be surprised at fishyness-tastelessness and veggy-tastelessness? SteveBaker (talk) 02:18, 4 January 2009 (UTC)

I'm afflicted with the ability to taste something nasty (metallic) in cilantro. I share this useless superpower with one parent and not the other. —Tamfang (talk) 19:59, 5 January 2009 (UTC)

I think the usually difference discussed is the dislike of some food by supertasters, not taste-blindness. But loss of tasting ability occurs with aging or with ageusia (never heard of that problem before). Rmhermen (talk) 00:59, 6 January 2009 (UTC)

"Blind spot" in face recognition?

Is there a name for the phenomenon in which a subject has difficulty telling apart specific pairs of faces (of different individuals) when most people in the general population have no difficulty telling one face from the other in those pairs? (The subject in question doesn't have a general problem recognizing or telling apart faces, only difficulty w.r.t. specific, idiosyncratic pairs.) —Preceding unsigned comment added by 173.49.15.111 (talk) 18:22, 3 January 2009 (UTC)

See Prosopagnosia. Of course, you may not recognise it, as it looks like thousand other articles. --Cookatoo.ergo.ZooM (talk) 19:28, 3 January 2009 (UTC)

Thanks for prosopagnosia reference, but the kind of confusion I was talking about is both selective and idiosyncratic, in that the subject generally has no problem recognizing and telling apart faces, except for specific pairs that most people won't find particularly similar or confusing. --173.49.15.111 (talk) 20:58, 3 January 2009 (UTC)

It's perfectly possible that this is a mild form of that condition. It seems that there is specific 'circuitry' inside the brain that is specialised for facial recognition. Prosopagnosia is a complete and utter failure of that circuitry - but it seems reasonable that there might be a partial failure that might make (say) recognising the shape of the mouth and nose work just fine - but eyebrows, eyes and ears fail miserably. It's tough to know - but 'mild' or 'partial' prosopagnosia would probably be acceptable terminology here. SteveBaker (talk) 02:10, 4 January 2009 (UTC)

The ability to recognize faces doubtless runs in a continuum, rather than an all or none distribution. Some of us are at the 95th percentile and others at the 5th percentile. Those at the 5th percentile may function pretty well, but be lousy as eyewitnesses, or as a doorman, receptionist, bartender or salesman who is expected to greet "regulars" or club members by name. Likewise a clergyman, teacher, policeman, bounty hunter or politician would benefit from being at a high level of memory for/recognition of faces. A workaround might be to remember verbally that "bushy eyebrows" is Mr. Smith, or similar cues, where someone good at facial recognition would just automatically recognize Mr. Smith. A psych experiment published in a journal a few years ago (I do not have the cite at hand) showed the power orf the normal person to recognize faces. The experimental subjects looked through an unfamiliar high school annual one time, looking at each face once. They then showed a good ability to distinguish faces they had seen from unseen faces from other similar annuals. At the other extreme, a clerk might see a person 10 times over a month and not recognize them the next time. Edison (talk) 05:28, 4 January 2009 (UTC)

Bolbidia

The following is from Aristotle's discussion of cephalopods: One of them is nicknamed by some persons the nautilus or the pontilus, or by others the 'polypus' egg'; and the shell of this creature is something like a separate valve of a deep scallop-shell. This polypus lives very often near to the shore, and is apt to be thrown up high and dry on the beach; under these circumstances it is found with its shell detached, and dies by and by on dry land. These polypods are small, and are shaped, as regards the form of their bodies, like the bolbidia. I can't seem to find anything about what a "bolbidia" is. Does anyone know? 69.224.37.48 (talk) 20:34, 3 January 2009 (UTC)

Most commentators on the Historia animalium seem to assume that a bolbidion is the same beastie as the bolitaina mentioned by Aristotle in the passage immediately preceding the one you quote. In any event, I think the best one can say is that it's some sort of small octopus; trying to identify it with any particular species is probably futile, especially since the word is apparently attested only here and in the Hippocratic corpus. Deor (talk) 00:24, 4 January 2009 (UTC)

The ancient Greeks didn't bother much with careful observation of nature or experimentation or things of that ilk. They felt that if you couldn't just think it up out of fresh air and prove it with some kind of math - then it wasn't worth considering. So it's likely that Aristotle's observations on marine life were sketchy to say the least! SteveBaker (talk) 02:06, 4 January 2009 (UTC)

Actually, Aristotle was one who did bother with observation, particularly with regard to marine life. He used to hang out with fishermen to get specimens. The problem is that he, and the fishermen, knew exactly what βολβίδιον denoted and we don't (other than that it's a small octopus), since the art of taxonomic description hadn't been invented yet. Deor (talk) 03:41, 5 January 2009 (UTC)

World steel supply irradiated ?

I saw this statement in the Wiki article Scuttling of the German fleet in Scapa Flow:

"The remaining wrecks lie in deeper waters, in depths up to 47 meters, and there has been no economic incentive to attempt to raise them since. Minor salvage is still carried out to recover small pieces of steel that can be used in radiation sensitive devices, such as Geiger counters, as the ships sank before nuclear weapons and tests irradiated the world's supply of steel."

Regarding the statement about irradiated steel, is this true ?

Thanks,

W. B. Wilson (talk) 20:35, 3 January 2009 (UTC)

I've heard it elsewhere, so it is plausible, but it involved very low levels of radiation. I do not recall the source. Edison (talk) 20:52, 3 January 2009 (UTC)

Google steel radiation battleship and you get some sources: IEEE mentions pre 1945 battleship steel as a bulk shielding material for delicate experiments detecting "cosmogenic neutron flux." Other materials of interest to such researchers include 400 year old lead. Another reliable source says that at many U.S. Dept of Energy sites, pre WW2 steel is used for shielding. Edison (talk) 20:59, 3 January 2009 (UTC)

Thanks! W. B. Wilson (talk) 21:11, 3 January 2009 (UTC)

Wow - that sounds AWFULLY bogus. I don't believe this is the reason. Sure, there obviously IS a reason for using that old steel - but I can't believe it's because of nuclear weapons.

Surely the amount of nuclear-weapon-derived radiation irradiating that 60 year old steel between the time you pull it out of the ocean and the time you form it into an instrument is comparable to the amount that modern steel picks up during the brief time between smelting the ore and casting it (remember - that iron ore is millions of years old and has been protected from atom bomb test contamination by being buried under hundreds of feet of dirt - which has got to be as good protection as 40 feet of water). The amount of time that the metal is above ground and exposed to nuclear waste contamination is going to be pretty comparable in either case. If the metal can pick up contaminants between digging the ore and making it into steel - then the finished instrument is going to be totally useless after just a few weeks because it'll pick up that same contamination during daily use.

It just doesn't make logical sense.

I'd be more inclined to suggest that steel that's been shielded from naturally occurring radiation by a large amount of water would have reduced amounts of radioactivity simply due to the half-life of whatever radioactive elements are there naturally. This would result in any radioactivity naturally present in the original iron ore having dropped off considerably over the past 60 years. Meanwhile, iron ore that's been buried in the ground (which produces background radiation from natural occurring uranium, radon gas, etc) could maybe have background levels of radiation that are unacceptably high.

I don't really see how atom bomb testing can have very much to do with it...but I could easily be wrong. If I am wrong - then I'd still lay odds that the fallout from Chernobyl was far more significant than those old bomb tests.

SteveBaker (talk) 02:02, 4 January 2009 (UTC)

Did you take a look at the sources I cited and other reliable sources from the Google search? Apparently fallout or other products of nuclear explosions since 1945 do in fact make their way into modern steel. It is not just the age of the steel per se, or the fact that it was in the ocean. Atmospheric nuclear tests after WW2 and Chernobyl may indeed have done more contamination than the 1945 tests and attacks, but that still leaves modern steel less useful for shielding sensitive detectors than steel from the pre-nuclear age. Edison (talk) 05:25, 4 January 2009 (UTC)

Yes - I did look at them - and I agree that this is what they seem to be saying - but if a reference says that 2+2=5 - then I'm going to have to at least stop and question it. This explanation doesn't make any kind of sense at all. I have no problem believing that modern steel is inferior - I just can't see how it can be artificial 'fallout' contamination that's causing that. I don't believe that those nuclear tests contaminated iron ore buried in mines that are hundreds of feet below solid rock...that just can't be true. It's also somewhat hard to believe that none of that fallout wound up floating down through 40' of water and landing on the decks of those sunken ships - or washed down into the ships from nearby rivers and beaches.

So if the ore is pristine when it's dug up - and even assuming that the metal from these wrecks is also pristine - we're only left with the time interval between mining our ore - refining it into steel and forging it into whatever the end user needs - during which time it's gonna get contaminated with all of the crud in our atmosphere and lying around on the surface layer of the soil, etc. But that's got to be comparable to the time between raising a lump of 1945 warship to the surface - cleaning off the barnacles - and reforging that into whatever the end user needs...and during that time, it's picking up contaminants at pretty much the same rate as the freshly mined ore. So it seems like there would be no advantage to using 'old' steel versus 'freshly-dug-up' steel.

I could understand not wanting to use steel made from recycled 1960 Cadillacs that have been sitting out in a scrapyard near ground-zero in the Arizona desert.

So - yeah - I could be wrong - and your sources certainly suggest that - but I still don't understand how that's possible. I strongly suspect there is more to this than meets the eye.

SteveBaker (talk) 06:30, 4 January 2009 (UTC)

It is possible that steel which was melted and re-forged would have the trace amounts of radiation throughout, but old steel which has not been molten may be immune to this radiation. Since steel does not occur naturally, the only way to get "clean" steel is that which was forged in the past before this "contamination" took place.

I have also heard this in the past, and I am unsure of its basis in truth, but that is the theory that popped into my head.RunningOnBrains 09:33, 4 January 2009 (UTC)

The reliable sources (specifically, the IEEE paper), do not cite reasons why the "pre-1945 battleship steel" is preferable or different - so there's a leap of logic to assume that this material has in any way been affected by nuclear testing. It may be different for a huge variety of reasons - different composition, different testing standards, something to do with aging process, ... etc. Nimur (talk) 14:32, 4 January 2009 (UTC)

The Health Physics journal does however. How reliable it is, I don't know Nil Einne (talk) 15:35, 4 January 2009 (UTC)

Atmospheric carbon-14 levels. Spike represents the end of aboveground nuclear testing in late 1963.

Not sure about the reliability of statements about radioactivity from atmospheric contamination, but I'm willing to say that they're plausible. Iron ore is usually refined in a blast furnace, which strikes me as a very efficient way to move very large volumes of modern, radioactives-contaminated air through the ore.

Meanwhile, the level of (radioactive) atmospheric carbon-14 just about doubled in the mid-1960s due to aboveground nuclear weapons testing. (Levels are still about 10% above 'natural' background carbon-14, which is generated mostly by cosmic rays.) Measuring the abundance of (excess) carbon-14 in tooth enamel (which lasts essentially for a lifetime, once laid down in one's adult teeth) and comparing to atmospheric abundance of carbon-14 is a recognized forensic technique ([11]) for determining the age of human remains. It's accurate to better than plus or minus 2 years.

With a half-life of about six thousand years, the level of carbon-14 in the pre-WWII steel won't have been significantly reduced by radioactive decay. That said, there are no doubt other radioisotopes released by the aboveground testing. I don't know what they are, or what their relative abundance is, or whether they would also find their way into steel. Just food for thought. TenOfAllTrades(talk) 16:08, 4 January 2009 (UTC)

Right, the problem isn't whether the iron ore is contaminated. It's whether the residual contamination in the atmosphere is enough to make its way into any steel processed in our modern, somewhat-contaminated atmosphere. And nobody is claiming the steel is glowing green—it's very minor contamination that only comes into play involving instruments that are sensitive enough to detect such contamination. And Steve, I think you underestimate the amount of residual, long-term fallout produced by the US and Soviet atmospheric testing programs, which detonated probably around 400-500 megatons worth of weapons from 1945-1963. It is significant and measurable amount. --98.217.8.46 (talk) 19:51, 4 January 2009 (UTC)

There was a time when children enjoyed "snow cream" made of snow, sugar, milk, eggs and vanilla. Then in the late 1950's or early 1960's parents stopped making it because they read about the danger of strontium 90 in the snow from atmospheric nuclear testing [12]. If steel was recycled, air used in the process would have brought these same nucleotides into the steel, certtainly in greater amounts than in 1944. If new steel is made from iron ore, there is no way to exclude the contamination laying on the ground when the ore is mined by blasting away the earth and digging up the ore. The difference is probably between a very low level in modern steel and a vanishingly small level in pre-1945 steel. Surface contamination would not put the radioactive particles in the bulk of the steel. Edison (talk) 23:04, 4 January 2009 (UTC)

sexual reproduction would never work.

God and I disagree about whether human reproduction works. The idea that you can combine two people's DNA to get a third working human is ridiculous. Would you combine two pieces of software, taking half the bits from one, half the bits from another, to get working offspring software? No... It would segfault as soon as you ran it. I estimate that fewer than 1 out of 100 humans would be born alive and well if DNA were really being 'combined' from the mother and the father. —Preceding unsigned comment added by 79.122.54.197 (talk) 23:37, 3 January 2009 (UTC)

Do you have a question? Deor (talk) 23:48, 3 January 2009 (UTC)

Yes. I'd like to clear up my confusion, hence sharing my arguments with you.

(To original Anon poster): Reality would disagree with you. -- Flyguy649 ^talk 23:50, 3 January 2009 (UTC)

I disgree strongly with reality on this point. The fact that it happens doesn't imply that it's possible.

But that's the definition of possible. When something can and does happen. --Russoc4 (talk) 00:07, 4 January 2009 (UTC)

then I suppose a woman u.s. president is not possible, since you said possible is what can and does happen. —Preceding unsigned comment added by 79.122.54.197 (talk) 00:52, 4 January 2009 (UTC)

I guess that wasn't what I meant. I mean that action implies definite possibility. It is possible for there to be an African American president of the US... it happened. --Russoc4 (talk) 01:23, 4 January 2009 (UTC)

it will happen in about 17 days. Didn't happen yet. In any case, you need to specify that anything that is, is possible, but that just because something isn't, doesn't mean it's impossible. - Nunh-huh 01:29, 4 January 2009 (UTC)

Comparing DNA to software is a false analogy. This is where your logic is going wrong. Read up on meiosis. Also, sometimes mixing DNA can go wrong, see: nondisjunction. --Mark PEA (talk) 00:02, 4 January 2009 (UTC)

So then if the current understanding of reproduction is wrong, what do you suggest is going on? --Russoc4 (talk) 00:06, 4 January 2009 (UTC)

To clarify Mark's answer, reproduction is not like cutting half out of each parent and sticking it together. Firstly, DNA replicates. The replicated versions of DNA are what go on to form a new human. I'm not convinced you'd understand if we went into detail here since you don't understand the basic concept, but there are plenty of good explanations out there if you search Google. —Cyclonenim (talk · contribs · email) 00:30, 4 January 2009 (UTC)

thanks for watching out for my interests, but why not try me. anyway DNA is just like software, the genetic code is completely equivalent to 2 bits per base pair -- there is NO OTHER INFORMATION it contains. Anyway you're technically right that replication happens before combination, since the reason those haploid cells exist in my testicles or your fallopian tubes at all is because they have reproduced from other cells. But then, when my sperm hits your egg, God would have these two haploid cells combine into a duploid cell (before starting to split etc), through sexual combination. Which is patently ridiculous -- otherwise you could just take a haploid version of two pieces of software, combine them willy-nilly, and get a new piece of software. Nice try God. —Preceding unsigned comment added by 79.122.54.197 (talk) 00:42, 4 January 2009 (UTC)

as an aside, your statement "there is NO OTHER INFORMATION it contains" is only approximately true. see epigenetics. - Nunh-huh 01:33, 4 January 2009 (UTC)

Don't tell God what to do with his software. bibliomaniac15 00:49, 4 January 2009 (UTC)

(edit conflict)Another analogy: science has trouble explaining how bees can fly. ~AH1^(TCU) 00:51, 4 January 2009 (UTC)

are you saying you disagree with God that bees can fly? What does that have to do with my question? Start your own thread!

Most software is a waveform, DNA is matter. They are not "just like" each other.--OMCV (talk) 01:12, 4 January 2009 (UTC)

DNA encodes genes. the code is almost binary. —Preceding unsigned comment added by 79.122.54.197 (talk) 01:15, 4 January 2009 (UTC)

DNA can exist without hardware, computer software can not. There is a ton more INFORMATION in a DNA base pair than two bits.--OMCV (talk) 01:21, 4 January 2009 (UTC)

I strongly disagree. There is NO more information in a base pair than two bits because physically, chemically and in every other way two atoms of the same isotope of an element are identical. Two adenine bases are quite utterly indistinguishable from each other (unless there is some weird isotope present in one or more of the atoms - and I REALLY don't think that codes for anything special). Hence there is no place for more than two bits of information to reside. Your claim is bogus - wrong, wrong, WRONG! Furthermore - the DNA *IS* the hardware - no different from a punched card, a flash memory chip or a hard drive in that regard. It's meaningless to say that the hardware can exist without hardware. With appropriate DNA synthesis techniques, we could store Wikipedia on a DNA molecule with two bits per base-pair.

The information contained in a DNA strand is independent of the 'hardware' DNA molecule (we did the human genome project thing and stored the information from the DNA strand onto a bunch of CD-ROMs). That's no different from the information contained in a flash-memory chip. The distinction (and it's a pretty subtle one) is that "software" is the information that's stored on a chip or a disk drive someplace and "DNA" is the storage mechanism itself. In the case of computers, we can copy the software easily from one piece of hardware to another - and in the case of the information on the DNA strand, we can copy it (painfully) by gene-sequencing onto different hardware (a CD-ROM maybe) - or copy it easily by the rather brute-force approach of making an exact copy of the "disk drive" that the information is stored upon. Sure, we slightly blur the terms "DNA" and "Genome" where we rarely blur "RAM Chip" and "Software".

Can DNA exist without hardware? No - because the DNA *IS* the hardware. Can we store the information that's stored on the DNA without the DNA hardware? Yes! We already did that with many species when we gene-sequenced them - but no information can exist without being stored SOMEHOW in either matter or energy. Can we store software without hardware? No - just like the information on the DNA, it needs some sort of hardware to hold it. But that could be handwriting one a piece of paper - or photons shooting down an optical fibre. Your distinction is bogus - and grossly misleading. SteveBaker (talk) 03:44, 4 January 2009 (UTC)

Every base pair has vastly more information attached to it than the most complex computer subroutine. Lets remember that its not possible to simulate a single atom in a system containing more than one electron. There are thirty or so atoms and hundreds of electrons included in every nucleotides containing information about potential bonding and countless other physical properties. The fact that every one of these subroutines is identical and can be grossly simplified to a one of four bits does not negate any of this information. Its similar to claiming a stick figure or perhaps a nine digit number can accurately represent a person. At times such a simplification can be useful, for example in XKCD, but its still a simplification and limitations have clearly not been appreciated in this situations. The question posed here did not concern the ability of DNA, software, or a computers to store data but the functionality of the systems. Specifically the successful breeding to render functional offspring. The functionality of data is directly related to the hardware its stored in. In this case there is DNA, a type of hardware (I agree) with embedded data, versus computer software, which is comprised of bits independent of its hardware. It is not surprising that a system with an interrelated data/hardware system displays greater functionality, such as self replication, than a software system that simply resides in its hardware. To look at it from another angle we could also ask why two paper dolls (mostly hardware) can't breed to form a new paper doll while people can. As I mentioned there are similarities between people and dolls (stick figures) but for some reason most people think that sounds dumb. That was my point.--OMCV (talk) 05:07, 4 January 2009 (UTC)

It's very clear that you don't understand the first thing about information theory (and I happen to have a degree in the subject). And it's too hard and too late for me to explain it to you. You have not understood the distinction between the "information" and the "substrate" in these two cases. That blurring of boundaries is throwing off your thinking and causing you (honestly) to talk gibberish. Suffice to say that it's as irrelevant that a DNA base-pair has all of that internal 'state' (due to atoms and electrons and 'stuff') as it is irrelevant that the transistors that make up one 'bit' in your RAM chip is made of atoms and electrons and stuff. It's not the amount of stuff inside that matters - it's the amount that's stored and reproduced when the information is 'expressed' (copied, transferred, used). In the case of DNA, it doesn't matter what the spin on the 9th electron of that 3rd carbon atom inside that base pair is because that information doesn't get passed on to the other strand of the DNA as it's copied - and it doesn't cause any difference in how the gene that it's a part of forms a protein molecule. So just as the precise state of the atomic structure of one bit of your RAM chip doesn't affect how Internet Explorer runs - so the internal state of that base-pair doesn't affect how the DNA works. Hence two bits per base pair - period. This is a VITAL property of systems like software and DNA - and it's the reason computers use digital circuits and not analog circuits for running software...if every teeny-tiny quantum fluctuation affected how your software ran - it wouldn't work repeatably and it would be useless. Similarly, if the precise electron configuration of a DNA base-pair mattered when copying it or expressing a gene as a protein - then the DNA would make different proteins all the time and we'd die within a few milliseconds! Accurate reproduction and expression is a property of purely DIGITAL systems - and DNA is exactly that - a quaternary-digital system. Two bits per base pair - period - nothing else matters.

As for self-replication. We most certainly can (and do) make self-replicating software (we call them "viruses"...and there is a reason for that!). It turns out not to be very useful because computers can run multiple instances of a single copy of the code - but that's "an implementation detail" that doesn't affect any of the arguments...if it did, we'd make our software replicate - it's trivial to make it do that.

If you still think otherwise then I'm sorry but you simply don't know enough science to comment intelligably on such a technical matter.

SteveBaker (talk) 06:07, 4 January 2009 (UTC)

I don't have a problem with self-replication. It's the idea of two pieces of software replicating with EACH OTHER that I find ridiculous. And no, we don't have examples of two different viruses of the same "species" (close enough to reproduce 'sexually') combining with each other willy-nilly, so that if they have fifteen offsprings, each will be a healthy, working piece of software, and also subtely different from its siblings. It's a ridiculous thought, and I can't believe God would have people combine in such a way. It's absurd. As I said, I estimate fewer than 1 out of 100 offspring combined in this way from two people's DNA would be a healthy, functioning human. 79.122.10.173 (talk) 13:49, 4 January 2009 (UTC)

It's irrelevant that the code is almost binary, that doesn't make it software. DNA is not made of electrical signals, ones and zeroes and on and off, but chemicals. Not only that, but if we have to compare it to numbers, it's not two different digits it's four (for the four bases). You can't say DNA is like binary code when it simply isn't. —Cyclonenim (talk · contribs · email) 01:24, 4 January 2009 (UTC)

Software isn't "made of electrical signals" either - I can store software in my brain (I can recite the quicksort algorithm from memory in 10 different computer languages - so it's not even in 1's and 0's until after I type it into a computer and have the compiler compile it). I can store software as magnetic signals (most of my software is on a magnetic disk at this very moment) - Computer software is transmitted to the Mars rovers every day using a radio link - the software is 'made of' photons for the many minutes it takes to get to Mars...and I could go to any one of a hundred companies around the world and have them store a short piece of software as a DNA molecule (See: Gene synthesis) - although at about $0.25 per bit, I'm not sure I'd be storing anything very large that way! Then we can go the other way - we can gene-sequence a DNA molecule - get the long list of A's, G's, T's and C's - and replace each one of those letters with '00', '01', '10' or '11' and our genome information is just 1's and 0's. We can send it to Mars on a radio beam, copy it to our hard-drives - and (interestingly) pay a company $0.25c per bit to turn it BACK into DNA again. There quite simply ISN'T a distinction between software and the bits that make up a DNA molecule. You are confusing the information with the thing that holds the information. SteveBaker (talk) 03:58, 4 January 2009 (UTC)

Yes, DNA codons consist of three nucleotides, where four different nucleotides are possible. --Russoc4 (talk) 01:29, 4 January 2009 (UTC)

So it's a base-4 coding system - quaternary - not binary. However, that's a trivial distinction - they are both 'digital' codes and that's what matters. In the early days of computers, there used to be computers that worked in base-10. We software engineers habitually 'pretend' that binary digits are grouped into three or four so we talk about base 8 (octal) and base 16 (hex) numbers without caring too much how they are represented 'under the hood'. Many communication systems use base-4 coding schemes. That DNA happens to use base-4 is quite utterly irrelevent in terms of this analogy. You can analogize the DNA 'genetic code' with a piece of software code and the comparison stands up quite well: Nucleotides are like bits (except they are in base-4), Codons are like machine-code instructions, Genes are like subroutines, Chromosomes are like compilation units, the entire Genome is like a computer program (and a surprisingly small one IMHO). The analogies are very close (and I don't think that's an accident). However, the OP's analogy fails quite utterly - but not for that reason. My complete answer (which explains this point) is below. SteveBaker (talk) 03:07, 4 January 2009 (UTC)

While my background is in biologyu

I once found that if I added subroutines to a program from a library of Fortran subroutines, each did what it was supposed to do and the overall program worked. This might be a better analogy to the genetic combinations of sexual reproduction than your false analogy of taking a few bits from one program and a few bits from another. Each of the combined units has to have a certain degree of completeness, like a gene, and not just random base pairs like your analogy would imply. You need complete modules. Edison (talk) 01:31, 4 January 2009 (UTC)

(EC)I'll bite a bit. Meiosis is not like trying to put together two random programs; it's more like taking two versions of a program that were once the same but have been further modified or tweaked by different developers and then put together. However, the coding for each module within the software would have to be about the same size and in roughly the same place within the overall program. (I'm not a programmer; I'm a biologist. Pardon my gross simplification/poor analogies of programming. And I'm thinking Windows and its various components in my analogy.) Human chromosomes are by and large extremely similar, each is around 96-99% identical to its sister chromosome. (This is from the recent sequencing of the haploid human genome reported in Nature earlier in 2008; I've got to run, but I'll get the exact numbers and ref later.) So during meiosis, the two chromosomes swap genetic material but the genes are essentially in the same order, with only minor differences between them. You aren't trying to put together a fly with a human; that wouldn't work. Or Windows crossed to Mac OSX. I'll post more later, but I have to run now. -- Flyguy649 ^talk 01:38, 4 January 2009 (UTC)

The thing our OP is missing is that the two humans are ALMOST identical - they differ only by the tiniest percentage of their DNA (remember - human DNA differs from chimpanzee DNA by less than 1% - so a 1% difference is a LOT!) But if you attempt to cross-breed (say) an Aardvark with an Apple Tree - then the odds of getting a successful living plantoid-creature from the random gene shuffling are indeed almost exactly zero. I don't know where this 1 in 100 estimate comes from - but I can't believe there is any science whatever behind it - so that's what we call "a wild guess" and not "an estimate"!

Our OP's computer program analogy is also faulty. If you took two functioning computer programs that were both derived from the same original source code and did almost exactly the same thing - and were identical except for a few different lines of code and a couple of different constants - then you could indeed take random subroutines from one and put them into the other and the resulting code would stand a very good chance of working indeed. (In the software business, we do this all the time when we do a 'merge' using a version control system such as subversion - and indeed the resulting hybrid of my latest version and my co-worker's latest version does indeed work 99% of the time.)

More importantly for the survival of our offspring - there is a lot of redundancy in the genome - there are many genes that are duplicated on two different strands - so if one gene fails, the other takes over. That's how someone can be a 'carrier' of something like sickle-cell anaemia without suffering any consequences from it. It's only when both parents have one defective copy of the gene that their offspring stands a 1 in 4 chance of getting two bad copies and the disease manifests itself.

So you may rest easy - this is no problem at all to understand - no deep mysteries - just simple genetics. SteveBaker (talk) 01:41, 4 January 2009 (UTC)

I thought the Windows analogy was good. People can have a random assortment of different versions of different DLLs and it all still works. Sort of. By the way there are genetic algorithms implementing something like sex used in software and they are quite good at evolving useful designs. Dmcq (talk) 12:14, 4 January 2009 (UTC)

Nice one! Genetic algorithms are an excellent response. Remove the "reproductive" component and the algorithm will not improve. --Scray (talk) 15:55, 4 January 2009 (UTC)

In the computer code analogy, mixing bits or machine language instructions from two different programs is likely to end badly. But if the programs were Basic, and one was displaying a picture while the other was playing music, or printing text, mixing the instructions would often yield a program which would execute, occasionally with interesting results. There could still be structural errors which would prevent execution, but sometimes the result would be something like the combined execution of the two programs. If one programs said print "hello" and the other said to sound a "beep" these two events could happen in turn. Loops or "goto" statements could produce random results when intermixed. Edison (talk) 22:49, 4 January 2009 (UTC)

So here's where genetics and programming as we do it differ; especially as regards the poster's presumed dilemma. In order for there to be two humans creating a third human, they must be functional "programs." That is, PRINT "HELLO WORLD" and PRINT "HELLO World" are a priori valid programs, otherwise there would not be the issue at hand. Additionally, DNA when it is copied has a number of "protections" "built-in" such that it is very unlikely that copying PRINT -> PRINT you'll yield anything other then PRINT. It's still possible, and something along those lines may contribute to stillbirth, cancer, and spontaneous abortions. But the data isn't just held in quadrinary form - every value is duplicated, so not only does a mutation have to spontaneous occur AND sneak past the error checker (which was called p13 when I was in school, although apparently they went around and named these things since then) it also must occur at two sites! Even giving a 50-50 probability (which is surely outrageously in the arguments' favor) for all that, it's still less then 1/8 possibility for a single point mutation (contrast with 100:1, the OP's claim). Also in our favor is that a lot of our genetic material is junk DNA, or functionally irrelevent - say, my eye color. Even if I mutate a brand new spanking eye pigment, I'm still a functional human being. Finally, DNA - as best I understand it - doesn't seem to be a blueprint in the terms we'd think of it - "Make a five foot long spine, see page 15 for details," but rather, it's more like a progressive algorhythm (although I seem to have that name wrong - if anyone remembers the term, by all means, edit and claim) where "any" set of data can fit in. That is, if there was a point mutation in "five foot long spine", it would of necessity be a valid product (as opposed to, for example's set, a cluster resulting in "dive tool rong line") - although perhaps not necessarily "human".

Or, in short, while you're entirely likely to get PRINT "HELLO WoRlD" from the two parents, it's not terribly likely you'll just hop on over to "MOV AX,GGGG" It can and does happen, but consider Levenshtein distance as applied and given two functional inputs. 98.169.163.20 (talk) 23:55, 4 January 2009 (UTC)

While SB and 98 have given good responses and others have briefly mentioned this a key point is that you don't just randomly get bits and pieces of DNA from you parents. You get whole chromosomes. When we're talking humans your parents by and large don't really have different genes. They have different alleles, in other words different versions of the same gene. Most of these differences have little effect. To use a programming example, let's say you have a subroutine which in response to a signal adds questions marks to the end of sentences (that signal is sent by other subroutines which only send the signal when the sentence is a question). Parent A has two functioning copy of this subroutine, Parent B has two defective one. If Parent A and B mate, the resulting program could have either two copies of one gene, or one of both. If it has at least one copy of the subroutine, it will add the questionmarks. If it has none it won't. The later will be a little annoying but is not critical. We know that because parent B had it and parent B wouldn't exist if the problem was critical. And that's a key point. It's not possible that parents are missing key subroutines (or genes) because they wouldn't themselves exist if they were (it is possible they only have one copy of a key subroutine or gene). P.S. One clear example of the flaw in the OPs thinking is this "otherwise you could just take a haploid version of two pieces of software, combine them willy-nilly, and get a new piece of software". Except that a mother and father aren't two pieces of different software. They are both humans. We're not talking about a Dreamfall and NOD32 'mating' but two different versions of NOD32 with very minor differences mating. Nil Einne (talk) 10:49, 5 January 2009 (UTC)

Yes - exactly. And (as I pointed out) - software engineers do PRECISELY that as a routine part of their jobs. Already this morning I took a version of the software that I've been working on for a couple of weeks - and a version of the same software that someone else has been working on for several weeks and used the 'merge' feature of the subversion version control software to merge them together. The resulting program runs like a charm. Sometimes it doesn't come out like that - but generally, it does. This is precisely analogous to some set of DNA data that started off as a common ancestor of husband and wife - which has been altered (very slightly) by evolution over the past dozen generations so that the husband's version of those DNA strands is a little different from his wife's. The resulting "merge" of those two sets of information is (just like my merged software) very likely to work just fine. More importantly (as others have pointed out) - the way cellular biology works - there are two copies of most of the information in the DNA - and you get one from each parent - so there is a fair bit of redundancy that make the system much more fault-tolerant than my software merge analogy. That's reflected in the fact that perhaps one in fifty of my software merges results in a program that either won't compile or crashes in some way - even though both 'parent' versions of that software compiled and ran just fine...where much more than 1 in 50 children grow up without significant DNA defects. SteveBaker (talk) 15:18, 5 January 2009 (UTC)

It's an invalid analogy. DNA is more akin to data, not executable code. If I have two well-formed XML files, both of which conformed to the same set of strict XSD rules, you absolutely can combine the two XML files to produce a third valid XML file. 216.239.234.196 (talk) 13:36, 5 January 2009 (UTC)

No - I can't agree with that. There is VERY little difference between 'code' and 'data'. XML is virtually a programming language. Very often, what's data for one program (eg a '.html' file for Apache) is also code for another (JavaScript for Firefox). Sufficiently complex data file formats (like XML) can have bugs in them that are similar in nature to coding errors. I can't accept that analogy. SteveBaker (talk) 15:18, 5 January 2009 (UTC)

Executable code contains machine level instructions that a CPU will execute. Data does not. Think of code as action; data as information. 216.239.234.196 (talk) 17:50, 5 January 2009 (UTC)

Actually, code and data are indistinguishable. If you change a file extension from .exe to .bmp, what was once a program is now a weird-looking picture. That's how buffer overflows work, if you enter the right data, it becomes code and gets exectued. Franamax (talk) 18:39, 5 January 2009 (UTC)

No, just because both code and data can be stored in the same place doesn't mean they're the same thing or that they're indistinguishable. It's been a long time since I worked in machine language, but if you gave me binary code and binary data for a CPU I know, I could easily distinguish which was data and which was code based on the op codes, registers, values, etc. I could also write a program that could distinguish between the two. 216.239.234.196 (talk) 17:27, 6 January 2009 (UTC)

So I repeat - is JavaScript code or data? It doesn't contain "machine level instructions" because it's interpreted, not compiled so by your first criteria, it's data (and Apache would agree with you - but Firefox would not). It does cause 'action' - so by your second critera it's 'code' - but an XML file can also be "action" if it's interpreted as (say) a route for a robot to follow. You could have a tag in the XML that tells the robot to repeat the previous route - or to repeat that route until it hits a wall...before you know it, your XML "data" has become "code". I suppose one could resort to the Church-Turing thesis and say that anything that acts equivalently to a Turing machine is "code" and everything else is "data" - but the BIOS ROM in your PC (because it cannot modify itself) is not code by that definition. Think about programming in Logo. You say things like "left 90 ; forwards 10 ; right 90" to make a robot move around - is that a route like our robot's XML route-description-file? Is it code? Sorry - but your distinction is blurry as all hell - and there is a very good reason for that - some things are both code and data - some things are clearly just code and others just data - and yet other things change their nature from code to data and back again depending on the context.

In a sense, DNA is code that is "executed" by the RNA molecule 'computer' - in another sense it's data that the RNA "program" processes. It's a lot like JavaScript in that some processes are treating it as data (the process that duplicates a DNA molecule for example doesn't care what 'instructions' the DNA strand contains - it's just data) - while other processes treat it as code - with a proper instruction set (such at the process that creates proteins). Read our article genetic code - it describes DNA as a set of 'rules' - which is pretty close to saying 'code'. A codon is made of three base-pairs. Each base-pair represents a 2 bit value - so there are 4x4x4=64 possible codons. The analogy with bits and machine-code instructions is completely compelling. The 64 codons contain instructions to the RNA to grab a particular amino acid and hook it onto the end of the protein - but also has instructions that stand for "START" and "STOP". The analogy is even more complete than that - some organisms have different RNA "computers" that use different machine-code sequences from ours - just as the old Z80 computer had a slightly different instruction set from the (broadly compatible) Intel 8080. The RNA "computer" even has things like exception handling to deal with illegal instructions and prevent the system from "crashing" if a bad DNA sequence is encountered. We implemented all of these things into our computers before we understood how DNA worked - it's an amazing case of "convergent evolution" where cellular processes and electronics have converged on almost identical solutions. SteveBaker (talk) 18:39, 5 January 2009 (UTC)

Congrats to the OP for a provocative question topic... I presume from the way the question was posed that the intent was to stir up a great argument and it has certainly been fun to read. However, as stated by several others already, the analogy is false. While it may be true that DNA is "information" and that some aspects of the DNA code are similar (and in many ways analogous) to computer code, we're missing a huge point here. Humans are diploid organisms, meaning that there are two nearly exact copies of each chromosome, and two nearly identical copies of (almost) every gene being expressed at the same time. It isn't as though fertilization slaps together random halves of two parental genomes to get a new whole (it was already suggested that the OP review meiosis for further clarification).

• My question back to the OP is, Why don't computer systems work in such a way as to execute two nearly identical copies of each program simultaneously?

I assume (as a non-expert in computer programming) that it would be a lot more difficult to do that way. THAT is why the initial question is a false analogy. Computer systems are the equivalent of a haploid genome. To pose the original question, you would need to have a computing environment in which every computer was a diploid system (new DOS = Diploid Operating System?) running two versions of each program (gene) simultaneously. Allow the user of each computer system to make small alterations (mutations) in the programs to optimize them for their own uses. THEN, select two computers (perhaps via an online dating service?), randomly choose one version of each program running on those computers (the haploid gamete), compile the two sets of programs together into a new, unique diploid software combination (the diploid offspring), and determine whether the resulting software could operate a new computer. Keep in mind that you'd have to limit users to tweaking the existing programs rather than writing new programs within a given operating system, unless you wanted to create a new species of computer systems. I expect there would be changes made in programs that would be incompatible when both programs were being run simultaneously, but you might do better than 1:100 if you designed the system robustly enough. --- Medical geneticist (talk) 21:56, 5 January 2009 (UTC)

Actually some fault-tolerant systems do work that way, e.g. for the space shuttle. It's expensive though. Dmcq (talk) 15:06, 6 January 2009 (UTC)

(@Dmcq) Yes - although two copies isn't enough - if the two program produce different results - which one do you believe? This is a problem with DNA too - the two copies may produce subtly different enzymes for some key body function (for example) and if one of them works great but the other doesn't then you may simply be mildly deficient in some important respect - or you might die of it - or you might function 100% OK - except that one of your children gets two copies of the defective gene and dies. That kind of uncertainty isn't going to help the space shuttle (Shall we fire the rocket motors now? Dunno - one computer says "Yes" and the other "No" - so let's fire half of them?!)...so the shuttle has (IIRC) seven computers - some of which run different software written by different programmers - and they vote on what to do. If one computer consistently votes against the others - it gets turned off. But I've worked in fault-tolerant systems (telephone exchanges) that employed multiple computers and voting logic - and you end up wondering what happens if the voting logic fails. It's a pretty subtle business to make a truly fault-tolerant system.

(@Medical geneticist) what you are describing is more or less a 'genetic algorithm' - and we certainly have those and use them fairly often in some areas of computer science. We'll take a bunch of (literally) random computer instructions and call that a 'genome' - we'll make a bunch of random organisms and run them to see which comes closest to producing the output we want. The one that comes closest is then 'mutated' by changing a few instructions at random to make a bunch more programs - which we again run to see which comes closest to what we want. Do this (automatically) for a few million generations and the program to do what you need literally writes itself! It's not a diploid system - and it's typically an asexual process (we don't mix the genes from two parents - we just mutate one parent to make a LOT of children). This is OK for small, specialised cases (I used it for recognising and identifying the outlines of buildings in satellite photography) - but in general, it's a tough way to make software. I did once make a system for generating the parameters to make 3D models of trees for drawing a large forest in my graphics system. That allowed both random mutation and sexual reproduction which worked very well - the user looks at a bunch of 3D tree models and clicks on the one (or several) that they like the most. The screen then clears and the choices are cross-bred - or if there is just one, it's randomly mutated - and the descendents are used to generate more tree models. After just a handful of generations, you start to get really nice-looking trees that fit your personal idea of what a tree should look like. If you want things that look like mature oaks - that's what you get. If you want fir trees - you can make those. Skinny immature apple trees - no problem! If you'd like to play with a system like that, do a Google search for Biomorphs and find an online biomorph player to dink around with - it's fun! SteveBaker (talk) 16:33, 6 January 2009 (UTC)

January 4

Engineering indexes

I'm trying to get a handle on the publication history and relative importance of an engineer in the area of civil and mechanical engineering. He does work in earthquake resistance of structures and (more recently) mitigation of explosion damage to buildings.

I'd rather not name the individual in question, since I don't think the poor guy wants to see a Ref Desk discussion about him pop up the next time he does a vanity search on Google. For testing purposes, some of the (recently-deceased) 'grand old men' of the field include George W. Housner and John Blume.

Can anyone who has some experience with civil engineering research point me to the typical indexes and sources one might use to check out an engineering researcher's background and academic credentials? (I know that in the biomedical sciences I'd hit PubMed/Medline, and that for pure math and physics I'd go straight to arXiv — is there an engineering equivalent?) TenOfAllTrades(talk) 01:32, 4 January 2009 (UTC)

Try Engineering Village (also known as Inspec, Compendex), Web of science (also known as Institute for Scientific Information (ISI) database), , Scopus, or simply Google Scholar. These all are general engineering databases; I am not aware of any specialized to Civil Engineering alone. Abecedare (talk) 01:45, 4 January 2009 (UTC)

Frequency of mass

Since all mass has an associated energy according to Einsteins E=mc^2, and E=hf (according to Planck?); then can it be said that every mass has associated frequency and is traveling at the speed of light through something? If not, why not?--GreenSpigot (talk) 02:25, 4 January 2009 (UTC)

De Broglie hypothesis. Algebraist 02:29, 4 January 2009 (UTC)

Aha! But is everything traveling at c?--GreenSpigot (talk) 02:44, 4 January 2009 (UTC)

No. Algebraist 02:50, 4 January 2009 (UTC)

All matter has an associated wave. For 'macroscopic' objects (like Aardvarks...I'm trying to work Aardvarks into as many answers as possible today!) - the frequency is insanely high. De Broglie says that the wavelength is planks constant divided by momentum (which is mass times velocity). Since plank's constant is an insanely tiny number and we're dividing it by a macroscopic mass - the wavelength is tiny and therefore the frequency is crazily high. 6.6×10⁻³⁴ divided by the momentum of a typical Aardvark (we'll go with 66kg because it's a BIG aardvark and it's just fallen off a cliff so it's moving at 1ms^-1 relative to us) gives it a wavelength of 10^-33 meters - and an Aardvark frequency of about 3x10⁴⁰Hz (why is this not mentioned in Aardvark?). Considering that the highest frequency we 'naturally' consider dealing with is cosmic rays at about 10¹⁹Hz - this is an outrageously high frequency! SteveBaker (talk) 02:54, 4 January 2009 (UTC)

Spuriose Planck derivation, SteveBaker

The calculation never made sense. A macroscopic object is not a mote; it's a bunch of motes. Usually when we count quanta we put a n as the integral coefficiend, as in E=nh/t. So unless every atom in something is entangled or otherwise in a Fermi condensvum, the h/mv is bogus. -lysdexia 01:25, 9 January 2009 (UTC)

Yes but the aardvark universe is outrageous. Does, therefore, all matter travel at 'c' in the space time continuum?--GreenSpigot (talk) 02:59, 4 January 2009 (UTC)

A wave packet...possibly a falling aardvark

Not exactly. You have to distinguish the concept of a 'wave packet' which has a group velocity that isn't tied to the wave's speed (which is indeed 'c'). The graphic (at right) gives some kind of a visualisation of what's going on. The big bunched-up blob is the particle and it is moving across the screen at whatever (sub-light) speed it needs to...but the high frequency squiggles inside are moving along at the speed of light. Technically - the particle is spread out over space - it's not a point as you might expect - and that's something that comes out in Schrodinger's equation as a 'probability density function'. The blob is showing us the probability that the particle is at such-and-such position. In the case of an electron (for example) this is a rather diffuse thing - it's mass is tiny so it's wavelength is rather long - so we have the whole Heisenberg uncertainty principle business going on - where we don't know where the particle is if we measure it's momentum accurately (which you'll recall figures into that wavelength calculation from De Broglie) - or if we pin down it's position accurately - we can't know it's momentum. Our Aardvark however has a VERY small wavelength - so (fortunately for anthills everywhere) we know pretty much exactly where they actually are. SteveBaker (talk) 03:20, 4 January 2009 (UTC)

Just want to check, is it appropriate to say that a macroscopic object is associated with a well-defined wavelength, as per de Broglie? Not that I know much about this at all, but I felt it strange to describe an object by a wave with a wavelength much smaller than the object itself and therefore thought it applied only to particles. —Bromskloss (talk) 16:37, 5 January 2009 (UTC)

Advantage of large population

What are the advantages of the world population being as large as it is, and what would the potential advantages be of it being even larger? NeonMerlin 04:25, 4 January 2009 (UTC)

Well, "large labor pool" comes to mind, but since we're no longer engaged in massive slave labor-driven projects, that may not be such a huge advantage. Overpopulation is increasingly becoming a problem as it is; I'd be inclined to think that the advantages are far outweighed by the disadvantages. I'd be very interested in hearing arguments and facts to the contrary, though. -- Captain Disdain (talk) 04:42, 4 January 2009 (UTC)

I've been thinking a lot recently about the opposite case - the downsides of a falling population. But if I reverse my 'time arrow' - I can come up with some relevent thoughts on this topic:

Any possible benefits of population growth can't be in the form of production or consumption - because at best they cancel out - and at worst, consumption outstrips production because of limited resource availability. (Food, water, land, minerals, fuel, plants, animals - you name it!)

So the benefits of more population could only be in the areas of things like ideas or software - where one idea can serve any number of people and a piece of software can be copied as many times as you like - hence more people means more ideas and therefore more benefits.

Let's imagine a world where the population doubled:

Consider (say) the business of making cars. If you have twice the number of people - you need twice the number of cars but you have twice the number of people to work in car factories to make them - so no benefits.

But consider the business of making computer games. If you have twice the number of people writing them - then there are twice as many different titles on the store shelves - but the cost of physically manufacturing twice the number of disks is very tiny. So we'd have twice as much variety - twice as much choice. Since the total number of games sold would double - and the total number of people working on them would also double - the profit (and cost) per game wouldn't change. You'd expect to see twice the number of new movies made each year - twice the number of new opera's written.

So if more choice is a good thing - then so is more population.

Sadly - doubling the population also doubles the amount of CO2 pumped into the atmosphere - doubles the rate at which we pull fish out of the oceans (which dramatically reduces the fish population - resulting in immediate disaster) - doubles the amount of fossil fuels we need - and therefore halves the amount of time until we run out. This would be a truly monumental disaster.

So I see almost 100% downside - but in areas where ideas matter - it's possible there would be some upside. Of course in some fields there is already too much in the way of new ideas. Scientists find it increasingly impossible to keep up with the latest news in their chosen fields because the journals where such things are reporting are proliferating too greatly. Every year there are movies that I'd be interested to go and see - but there are more of them than I have time for. So ultimately - even this small upside loses it's value. I suppose our notional car factory has twice the number of clever guys figuring out fuel saving strategies - so there might be some claw-back there - but I think it's small.

Interestingly, the small upside of a growth in ideas is a major problem with shrinking population size...if we could somehow halve the world's population (which would solve an AWFUL LOT of problems!) - the number of new movies, new computer games, clever new products from Apple corp - all of those things would slow down dramatically. With half the number of people making new TV shows - but the exact same number of hours to fill each week - the number of reruns on TV would skyrocket. That would be necessary too because with only half the number of people to advertise to - the advertisers can't afford to spend as much.

I think mankind could take care of that though - and in a sense things like Wikipedia are already doing that. By getting a better quality of life for this smaller population (because we have less to struggle with in terms of pollution and dwindling natural resources) - people could have more leisure time. We could improve things like the Internet (half the number of people means more bandwidth per person) - and have better penetration of arts and sciences from other cultures - and have a larger PERCENTAGE of the population generating interesting new content. Within limits - it's probably manageable.

SteveBaker (talk) 05:45, 4 January 2009 (UTC)

I suppose one could come up with a scenario where a large population is necessary to save the Earth, like a meteor heading towards Earth and everyone working to create the rockets and equipment needed to save the Earth. It's an extremely unlikely scenario, though.

There is a huge benefit to an ever-increasing population, however, in that more workers are then available to support the retired population. China is headed into a period where this law will work against them, as their One Child Policy has produced workers who now must support two retired parents, and, in some cases, four retired grandparents, in addition to their own children. That's a lot to ask of a single worker. While an ever increasing population isn't the same as a large population, it inevitably leads us there. StuRat (talk) 14:46, 4 January 2009 (UTC)

A large population may be nessecary when people decide not to reproduce. This is happening in some European countries and the population is falling. Developing countries are still reproducing quickly but even their population increase will soon decelerate. ~AH1^(TCU) 14:54, 4 January 2009 (UTC)

Except that people stop reproducing precisely because of the large population. This can be due to wanting to prevent the global problems caused by overpopulation, or due to more immediate concerns. For example, a lack of housing can make people reluctant to have children, if they know they will all be crowded into the same small apartment. StuRat (talk) 15:04, 4 January 2009 (UTC)

This is not a professional answer, rather some thoughts and additional questions. An ever-increasing population in which more workers are necessary to support the retired sounds a lot like a pyramid scheme. Given finite resources, wouldn't this eventually lead to collapse? Also, the idea that people stop reproducing precisely because of a large population seems like a good model given the assumption of very short lifetimes - won't our huge rate of resource consumption, combined with our long lifetimes lead to an overshoot above the equilibrium, followed by a shortage of resources? 41.243.38.111 (talk) 19:22, 4 January 2009 (UTC) Eon

I think it's more likely that people reproduce less because they often have guaranteed pension now and don't need to rely on their children to support them when they are old. Another important reason may be "the pill". Icek (talk) 14:15, 5 January 2009 (UTC)

SteveBaker said that increasing production and increasing consumption would cancel out. This is false. Cost does not increase linearly with production. Some times, the cost per unit decreases, hence Mass production. Software is the extreme form. Other times, the cost per unit increases, such as energy. The question is which happens more. Also, StuRat said that people stop reproducing because of large population. IIRC, it's mostly based on how well off they are. People who are better off have fewer kids. — DanielLC 22:36, 4 January 2009 (UTC)

For your argument it is sufficient that the cost is not proportional to production; e. g. there is some fixed capital cost and linear operating cost. Icek (talk) 14:09, 5 January 2009 (UTC)

Well - yes - but that effect decreases with volume. Sure, a big car factory that only makes one car a day is going to be way less efficient than one that's utterly maxed out on production. However, at some point that factory can't make anymore and you have to build a second factory - and then your fixed costs just doubled. So the idealised view isn't really right. Cars made by (to take an example I actually know about) the MINI company (a subsidiary of BMW) in just one heavily loaded factory in Oxford cost a comparable amount to similar cars made by Honda, Ford and others - yet their production is about a quarter what each of their rivals makes each year. So in that case, there was little if any savings through volume because the other companies have to have multiple factories running. Also, as volume increases, the fraction of the cost of the item in terms of labor and raw materials starts to dominate the selling price. Sure, you save on the initial design costs - but those will become increasingly negligable as more cars are sold. I think the benefits of a larger population in terms of reduced cost per item are going to asymptote to almost nothing in most industries. (Although - as I said - there are exceptions such as the software, movie and TV businesses).

You don't have to build a second factory, you can just expand the bottlenecks. You don't have to design a new car. You can just build the old one. You don't even have to design a new factory. Your resources and advertising may be cheaper in bulk. There's a reason markets tend to get dominated by a few large corporations. On the other hand, as production in general increases, you have to mine less easily accessible ores. You can no longer get cheap power from things like geothermal energy. That sort of thing also happens on a smaller scale with individual businesses, I just can't think of any good examples at the moment. — DanielLC 18:59, 5 January 2009 (UTC)

Look at our diseconomy of scale article for more examples. I wish I'd written it myself. :-) StuRat (talk) 03:04, 6 January 2009 (UTC)

A related question: What is the lower limit for the population at which we still could have as high a standard of living as we have it now in industrialized nations? We would need a sufficient number of experts from every profession (well, in an ideal world, maybe some professions wouldn't need to exist, like lawyers), but I have little idea about what's the number of people that could be considered "sufficient". Icek (talk) 16:46, 5 January 2009 (UTC)

The tricky part is in areas of entertainment and such. You could probably reduce the world population to a few millions and still keep agriculture and technology running. But we would be unlikely to be able to afford (for example) the Hollywood movie business. The latest James Bond movie cost $230,000,000. If we only had 2 million people - the cost of making that movie would be pretty similar to what it is today. But then everyone would have to pay $120 to go see the movie in order for it to break even...and that assumes that every single person wants to see it! That means that movies at that production price simply won't exist. However, with more or less unlimited natural resources - it's likely that overall prosperity would be vastly bigger - and perhaps then $120 to see a movie isn't so unreasonable. But then consider that with around 3,000 times less people around than there are now - there would only be a handful of talented actors - maybe only one or two movie directors - it would be REALLY tough to keep that kind of activity afloat.

The problem with answering this clearly is that there are just to many variables. If we reduced the population by the same factor throughout the world - the consequences would be different than if all but a few countries were simply eliminated. Having just a couple of million people spread throughout the world would cause transportation nightmares - pushing everyone together into just one region the size of (say) a single US state would have different consequences because we'd be unable to take advantage of natural resources throughout the world.

SteveBaker (talk) 18:04, 5 January 2009 (UTC)

If we're going to assume a good infrastructure everywhere or something else that doesn't exist in reality, increasing the standard of living elsewhere to make up for it would be trivial. If not, I doubt this is possible with a population of any size. — DanielLC 18:59, 5 January 2009 (UTC)

If the population increase is mostly among low IQ religious fundamentalists, it will be a disadvantage.

Small populations, by our current standards, can support fantastic intellectual ferment and artistic genius, by any standards. London in the time of Shakespeare and Renaissance Italy are two examples that spring to mind. With a smaller population, your chances of meeting the great ones of your generation increase. Would you rather see a James Bond movie, or an original production at the Globe? Hang out at Starbucks with some coders who did CGI for Harry Potter, or in a tavern where Michaelangelo's apprentices drink? OK, leave out the smallpox and forced marriages. My point is that what nowadays would be the population of a small town can, with the right leadership and cultural infrastructure, support enormous human creativity and the productivity of intellectual capital that withstands time. BrainyBabe (talk) 11:26, 10 January 2009 (UTC)

Acceleration?

In this video, the parameter "acceleration" is specified in a couple of places. For example, "Acceleration ramp from 0 to 30g." What does this mean? I can't think of anything else to control on a wave generator besides frequency and, perhaps, amplitude. Besides, in a simple harmonic oscillator, acceleration is not constant anyway. --VectorField (talk) 04:49, 4 January 2009 (UTC)

Well, it didn't actually say it was a simple harmonic oscillator - so I suppose an initial accelleration at the start of each cycle is possible. But I agree - it's a strange way to state the amplitude and/or wave-shape. I presume that this number comes about because of the mechanism they are using to shake the liquid...but it's hard to know. SteveBaker (talk) 05:14, 4 January 2009 (UTC)

It's common practice with shaker tables, like the one in the video, to specify the output in units of acceleration. This is because standards for vibration and shock tolerance, such as those in MIL-STD-810, are specified in units of acceleration. For a sinusoidal waveform, the stated acceleration is usually the RMS value, but for other waveforms it could be the peak. You can convert from acceleration to displacement by integrating twice:

a = A sin ωt ==> v = -(A/ω) cos ωt ==> d = -(A/ω²) sin ωt

where a is instantaneous acceleration, A is peak acceleration, ω is angular frequency, v is speed, and d is displacement. The last expression shows that peak displacement (what you called amplitude) is A/ω². Don't forget to convert your 30g figure into m/s².--Heron (talk) 12:31, 4 January 2009 (UTC)

RMS acceleration makes sense, but strikes me as a queer way of specifying amplitude. Perhaps acceleration is more relevant to durability than amplitude? So,

rms acceleration = 30g = 300m/s² -> max acceleration = 600m/s² -> displacement = A/ω² = 600m/s² /(2π 120hz)² = 1.06mm.

That sounds about right for a displacement, eh? --VectorField (talk) 00:42, 5 January 2009 (UTC)

Almost right. I think you want to multiply RMS by root 2, not 2, to get peak. As you say, acceleration, not amplitude, is what breaks things. In vibration testing, nobody cares what the amplitude is, as long as it's small enough to fit inside the test chamber. :) --Heron (talk) 21:47, 5 January 2009 (UTC)

It means that the acceleration starts at 0g and increases in a linear manner up to 30g. Whats the problem with that?--GreenSpigot (talk) 01:24, 5 January 2009 (UTC)

Why is Jelly easier to swallow than water?

During the last week or two I've been suffering from the acute phase of Infectious mononucleosis/Glandular Fever. During this time many of the symptoms are quite like tonsillitis and swallowing is painful. Can anyone suggest a good scientific reason as to why Jelly is less painful to consume than water is? Noodle snacks (talk) 06:47, 4 January 2009 (UTC)

Well if you're a UK resident, and jelly is what kids eat with ice cream (as opposed to the US meaning of "jelly" which is "sweetened fruit preserve"), there are two effects: one is that jelly is almost always served cold, which numbs the throat. The other effect is the gelatine (or gelatine substitute) used to set the jelly, which will coat the throat and soothe the inflammation. --TammyMoet (talk) 10:52, 4 January 2009 (UTC)

Water can also contain some irritants, like chlorine products, used to kill off the little nasties. This is true of tap water and bottled water that the makers fill from tap water. In addition, bottled water may contain some irritating chemicals which have leeched out of the plastic bottle into the water. StuRat (talk) 14:33, 4 January 2009 (UTC)

Such as Bisphenol A. However, what if it's previously boiled water? ~AH1^(TCU) 14:51, 4 January 2009 (UTC)

That would kill bacteria in the water, and maybe reduce the amount of chlorine products, but I doubt if it would remove chemicals leeched in from the plastic much. Just letting water sit for a while (in a glass container) also seems to allow chlorine products to vent off. StuRat (talk) 14:58, 4 January 2009 (UTC)

I'm not convinced the amount of Bisphenol A is enough to be much of an irritant. Indeed even chlorine. Note also any jelly made from said water is likely to contain the same chemicals. However the surface area your exposed to may be lower. IMHO the primary advantage other then the ones Tammy mentioned is that jelly is a softer product then water. Okay it's difficult to compare since jelly is a solid and water a liquid but IMHO it's true. Nil Einne (talk) 15:23, 4 January 2009 (UTC)

If by jelly we mean the fruit spread, then the plant which produces the fruit has filtered out many of the irritants, like chlorine, from the water. If by jelly we mean some concoction made with water and gelatin, then it has probably been let to sit long enough for most of the chlorine to outgas. StuRat (talk) 16:41, 4 January 2009 (UTC)

I'm still not convinced. According to [13] [14] (not the greatest sources but the best I could find) the halflife of chlorine in water is 1-5 hours. If your talking about a hospital setting I doubt the jelly would have been made more then 6 hours beforehand. Even in a home it seems resonable the jelly woulkd often be consumed within 3-6 hours of it being made. Perhaps not entirely consumed but the OP didn't say the jelly is fine if it's 2 days old but if it's just recently made its not. More importantly, whether at home or in a hospital there's a very good chance the jelly would have been covered for most of the time. Furthermore, it seems entirely plausible the half-life of chlorine in set jelly which is therefore solid/semi-solid would be significantly higher. All in all, particularly given it's not uncommon people will have an uncovered glass of water besides them for several hours it seems entirely plausible to me the water will actually have less chlorine then the jelly. BTW the production of jam does require water although that wasn't what were talking about. P.S. If you're in the US apparently a lot of water is now chlorinaminated and although I'm guessing the OP isn't from the US, in that case even leaving the jelly to set in the open air is not going to help you much. Nil Einne (talk) 10:20, 5 January 2009 (UTC)

I wasn't thinking of a homemade gelatin dessert, but one bought at a store (such as the two shown at the top of that article). Perhaps the original poster can tell us which one they meant ? StuRat (talk) 18:15, 5 January 2009 (UTC)

Another possible downside to drinking water is that hard water (such as well water), may contain high mineral levels, some of which can act as irritants. If the water is treated with a water softener, then it will have a high sodium level, instead, which can also be an irritant. StuRat (talk) 14:58, 4 January 2009 (UTC)

Alternatively, it may be the lack of stuff in the water. Pure water is bad for exposed (rough, raw) tissue. Try a lightly-salted water. Not good for hydration, though. Saintrain (talk) 19:52, 4 January 2009 (UTC)

Nothing at all to do with "stuff" or irritants, and everything to do with viscosity. Swallowing is a reasonably well-studied phenomenon, as it's necessary to evaluate stroke victims who have swallowing difficulties before permitting them to try to eat. In brief, the ease of swallowing varies with the amount you're trying to swallow at once (bolus volume), and by the consistency of what you're trying to swallow (liquid, semi-solid, and solid). Studies have shown that it's easier to swallow low bolus volumes, and it's easier to swallow semi-solid than liquid. [15]. - Nunh-huh 02:29, 5 January 2009 (UTC) (P.S. is British "jelly" the same as American "Jell-o"?

) <- Here's a closing parenthesis for you. Yes, I think you're right on the Jell-O theory, with the general name being gelatin dessert. StuRat (talk) 03:10, 5 January 2009 (UTC)

Many thanks for the ")". I have a chronic shortage. And for solving the "jelly" mystery for me...though in America it's traditionally accompanied by whipped cream, not ice cream! - Nunh-huh 03:30, 5 January 2009 (UTC)

Placebo

I was reading the wiki article on placebos and the placebo effect. I'm a major non-subscriber to non-western medicine. (Obviously the corollary is that I'm a major subscriber to western medicine.) I don't buy astrology, and I don't like religion or god, I don't believe in 'mystical energies' or in the healing power of faith.

My question therefore is--after reading about the placebo effect, people can actually get (somewhat) better just by thinking that they are? I don't really understand how that's possible, what's relieving the pain, or helping the suffering?207.172.70.176 (talk) 07:28, 4 January 2009 (UTC)

When given a placebo, there is no external, bioactive treatment relieving the pain, or helping the suffering. However because your body thinks it has been given something that has that effect, it is "tricked" into thinking it is feeling better. While there are obviously limits to the placebo effect, its remarkable how powerful, or influential, expectation is how our body reacts to injury or treatment. Have you ever noticed that you can cut yourself without even noticing (suggesting, therefore, there is no pain), but the moment you become aware of the cut it begins to throb? You see this in children (and association footballers) all the time, when they take a few moments for their brain to realise what just happened to them after they fall over, then they begin to cry. This is essentially the placebo effect in reverse: when you expect something to be painful, you begin to feel pain. Likewise, when you expect something to remove pain, the pain is attenuated. It works because pain and suffering are essentially mental states (in comparison to nociception). You can train the brain (through meditation, for example) or trick it (by placebo) to bypass or escape these states completely. See also Health applications and clinical studies of meditation.

While its relatively easy to appreciate how the interpretation of pain in the brain can be modulated by expectation of relief, its harder to explain how physiological effects are mediated by placebo, but they are. For example, a notable study showed that men with an enlarged prostate who were given a placebo reported improvements such as faster urine flow, and many even suffered from side effects (including impotence, diarrhea and constipation) - the so-called "nocebo" effect. The mechanism of these physiologic responses to a placebo are unknown, but the researchers suggest the the expectation of relief could have resulted in smooth muscle relaxation around the bladder, colon, prostate and urethra, which resulted in the effects reported.

So while relief of symptoms are now well established, what isn't clear, is whether anything can really be "cured" by placebo. People might feel better, but they aren't really "getting better" (in the example above, the paitients' prostates were still enlarged, even though some of the adverse effects of the enlargement was nullified by the placebo). There are occasional claims that people have been cured of cancer by placebo, but preciously little data to back it up. Rockpocket 08:18, 4 January 2009 (UTC)

I would note two distinct effects:

1) Placebos sometimes make people report that they are better, when they really aren't, as measured in any objective way. For example, somebody reports their flu is improved, but an analysis of their spittle finds the same count as before.

2) Placebos sometimes actually make people better, as measured in some objective way. There could be several mechanisms to explain this. Here are two:

a) It causes different behavior which helps reduce the disease. For example, if you have a rash, scratching it can make it worse. If the placebo convinces you that it doesn't itch any more, you stop scratching and the rash heals faster.

b) It reduces stress, which is known to trigger or worsen symptoms. The exact mechanism may be related to stress hormones in the blood, like adrenalin, which cause physical problems when they remain for extended periods.

I would expect that auto-immune diseases would benefit more from placebos, as they are more likely to be triggered by stress and behavior. StuRat (talk) 14:23, 4 January 2009 (UTC)

Also, a study shows that half of all American doctors have no ethical issues with prescribing placebos. ~AH1^(TCU) 14:49, 4 January 2009 (UTC)

Another reality is that many symptoms simply resolve if one is patient. A placebo, like any other medicine, is given a little time to work by the taker. If the symptoms are self-limited, the placebo gets the credit. --Scray (talk) 15:47, 4 January 2009 (UTC)

I haven't done much reading on the subject, it's generally believed that the opioid system is involved in the placebo effect, as an opioid receptor antagonist such as naloxone can block many of the effects of a placebo. Here's a ref: http://www.ncbi.nlm.nih.gov/pubmed/15820838 --Mark PEA (talk) 16:45, 4 January 2009 (UTC)

Animal cooperation and co-learning

it just struck me, can you teach animals to teach others explicitly or not.

Train a rat that when an LED in a box turns on, if you don't do something in 15 seconds it will shock you. Then can you put another rat in the cage and have him watch the other doing that?

Similarly, If you have two cages and two rats, but both levers have to be flipped for it to do anything.

I'm not asking for theories, I just want to know if anyone did this in the past, any reports on it... 68.37.71.40 (talk) 08:04, 4 January 2009 (UTC)

Animals rarely teach one another, but they often learn from each other. There is a subtle, but important difference: Teaching is a form of altruism, it requires the teacher modifies their behaviour to explicitly assist the student. Learning simply means the student watches and copies, at no cost to the teacher. While there are loads of examples of animal learning, there are only rare examples of animals teaching one another: See PMID 16407943 for one such example. Another possible example is Bonnie, a 30-year-old female orangutan at the Smithsonian National Zoo. She made headlines when she worked out how to whistle (the first primate to ever do so [16]) then soon after another orangutan, Indah, a friend of Bonnie's, aquired the skill also. Its not entirely clear, though, whether Indah simply copied Bonnie, or there was genuine teaching involved. But the fact that no other primate has copied human whistling, despite significant efforts to teach them, suggests there could have been some teacher/student interaction between Bonnie and Indah. Interestingly, this was done spontaneously and without human influence. Whether animals can be taught by humans to teach each other is an intriguing question. Rockpocket 09:06, 4 January 2009 (UTC)

What about birds giving flying lesson to their young? That's surely teaching. --86.125.163.133 (talk) 12:15, 4 January 2009 (UTC)

You you have any reliable examples of birds giving flying lessons to their young? Rockpocket 19:57, 4 January 2009 (UTC)

How about a mother predator who will catch prey, bring it back to her offspring, still alive, then let them practice catching it ? StuRat (talk) 14:12, 4 January 2009 (UTC)

That's learning, not teaching. The mother doesn't give feedback to the kids about how to improve, but rather demonstrates how to catch the prey and the children copy her. —Cyclonenim (talk · contribs · email) 14:38, 4 January 2009 (UTC)

I disagree. The mother will show them the proper technique (without the final kill), then encourage the young to do the same. If they don't she will show them again and again, until they get it right. This "showing them" phase has no benefit to herself, but is solely designed as a demonstration for her offspring. StuRat (talk) 14:52, 4 January 2009 (UTC)

Ah, very true. Good point. —Cyclonenim (talk · contribs · email) 17:22, 4 January 2009 (UTC)

Yes. Prey-handling skills have been demonstrated to be taught in meerkats (see PMID 16840701). But as Maelin points out, below, it all depends on how you wish to define teaching. A strict definition would require awareness of the ignorance of students and a deliberate attempt to correct that ignorance by the teacher. That is very difficult to demonstrate in animals. It unlikely the adult meerkats are actually thinking about teaching (our impression that they are, is just anthropomorphising on our part). Rather they are responding innately. The outcome may appear similar, but there are key mechanistic, behavioural differences. Rockpocket 19:53, 4 January 2009 (UTC)

One difficulty in the question is that it's not clear, even in situations where teaching appears to be going on such as predators bringing wounded prey for their offspring, whether the teacher is actively aware that the goal of the exercise is learning. Real teaching is a remarkably complex cognitive process, when you think about it. It requires the teacher to be able to model, in her head, the mind of her student - to create a mental representation of another mind with different knowledge to her own. The teacher then needs to work out how her own actions could increase the knowledge in that modelled mind of her student. This is an incredible bit of cognitive work going on here and it's not at all obvious whether any other species at all are capable of it. A leopard dragging wounded prey back to her young may not, at any stage, be aware that her goal is to educate her cubs. It may (indeed, probably is) simply be a purely instinctive behaviour, with the mother never realising (nor, perhaps, even being capable of understanding) that she is helping her cubs to learn. We humans are truly amazing creatures. Maelin (Talk | Contribs) 15:32, 4 January 2009 (UTC)

Wow, some of the best theroies on those type of experiments appear in the Saw movies but they involve only human behavior. The easiest to understand is probably in the wild, some chimpanzees eat termites by licking a stick and poking it into the termites hole so that little termites will stick to it and they learn that by watching each other. Also some types of monkey eat walnuts and they learn from each other to break them open using a rock (sorry can't rembember the exact monkey but they are strong little guys). All creatures possessing them have the capability to learn stuff but even your lovable Boxer dog will forget he has a neck and choke himself to death on his leash just because he is happy to be alive (ie, yes they are all capable but some would rather die or feel pain forever than participate in a pointless electrocution box) ~ R.T.G 18:02, 4 January 2009 (UTC)

I once had students try putting a naive rat in a Skinner box to see if the naive rat would learn from the highly trained rat that pressing the lever repeatedly brought water as reinforcement. Sadly, the naive rat just took the reward when it arrived and never pressed the lever, then the rats would fight. This is unpublished and thus anecdotal. Humans or apes might be quicker to learn by observation. Edison (talk) 22:42, 4 January 2009 (UTC)

Washoe is said to have taught some of the sign language she knew to another chimpanzee. Whether that was a deliberate attempt on her part, or perceptiveness and copying behavior on the part of the other is unclear. This article discusses orangutans playing charades in order to get specific desired food items. The article points out that "charades relies upon an awareness of what others do and do not understand". Recent research suggests that dolphins may possess a concept of mind. Finally, this article gives a good overview of animals teaching their young, but it is pretty loose on the definition of what constitutes "teaching." 152.16.16.75 (talk) 02:09, 5 January 2009 (UTC)

Where/when was c first used as the symbol for the speed of light?

Can anyone tell me where/when c was first used as the symbol for the speed of light (or for an equivalent like Maxwell's ratio of the electrostatic to electromagnetic unit, which has the dimension of length/time)? I know modern notations of Maxwell's equations contain c, but I don't have access to Maxwell's Treatise to find out whether it was Maxwell, Fizeau or someone else who may have first used the symbol c.Yetanothername (talk) 08:16, 4 January 2009 (UTC)

Although I'm not usually one for short answers, I'll just have to say click here. So much more information than I could even paraphrase with any justice. It's dry, I know, but what better scientific material is there right? Good day to you and I hope that helps. Operator873 (talk) 12:41, 4 January 2009 (UTC)

Great link! --Scray (talk) 15:52, 4 January 2009 (UTC)

The link is superb, and exactly what I was looking for! (I had always doubted the validity of Azimov's remark, but I see there is also more basis for it than I suspected.)Yetanothername (talk) 19:10, 4 January 2009 (UTC)

Time dilation

In the time dilation article it says that:

"In special relativity, the time dilation effect is reciprocal: as observed from the point of view of any two clocks which are in motion with respect to each other, it will be the other party's clock that is time dilated. (This presumes that the relative motion of both parties is uniform; that is, they do not accelerate with respect to one another during the course of the observations.)"

But if it were so, then wouldn't the two effects cancel each other out, and leave us with no time dilation whatsoever under special relativity? Then why do physics textbooks say that we can travel into the future by traveling close to speed of light, when we see that Earth's clocks ticks slowly at us too due to the reciprocal time dilation effect?

Thanks.

76.68.9.253 (talk) 15:31, 4 January 2009 (UTC)

In a word, no. Take two observers which are not accelerating; say, a man on a space walk in the middle of nowhere, and a man in a spaceship. The man on the spacewalk sees the spaceship traveling at 0.4c past him, and (if he could somehow see a clock on the spaceship) he would see the spaceship's clock running more slowly than his wristwatch. However, remember that neither man is accelerating: this the key point of special relativity! Because neither man is accelerating, there is no physical difference between the spaceship moving toward the spacewalk man at 0.4c, or the man moving towards the spaceship. Because of this "relativity" of non-accelerating frames (or lack thereof), the time dilation effect works both ways. If the man in the spaceship were able to see the spacewalk man's wristwatch, he would see that the wristwatch is running slower than his own clock.

In the case where you would use near-light-speed travel to travel into the future, you would only notice this change if you returned to the place where you started at rest (say, Earth). This would require a great force accelerating you away from Earth to a high speed, then an even greater force to accelerate you back. It is these great accelerations which lead to a different time effect, which is covered by general relativity, not special relativity. -RunningOnBrains 16:59, 4 January 2009 (UTC)

Thanks for the detailed response. It cleared up a long-standing confusion I've had with the twin paradox (I guess I should have consulted that article in the first place). Actually I was going with a different vein in my last question, allow me to rephrase it more clearly using the following scenario:

Let's say that about six months after a spaceship left earth, one of the astronauts traveling on the spaceship gives birth to baby A. By now the spaceship's engines are shut off and so the spaceship is coasting at a constant velocity 0.9c relative to earth ("for all eternity" -- as deemed by mission control), so that both earth and spaceship are now inertial frame with relative velocity 0.9c between them. Now, AT THE SAME TIME as baby A's birth on the spaceship, one of the mission directors gave birth to baby B on Earth. So that baby A and B are born at the same time, and are traveling in their respective inertial frames of reference that are 0.9c relative to each other at their birth and until their death. If both babies live to be 75 years old in their proper times, will B appear to die earlier than A to A's frame of reference, or will A appear to die earlier than B to B's frame of reference?

Thanks.

76.68.9.253 (talk) 18:24, 4 January 2009 (UTC)

That 'AT THE SAME TIME' is frame-dependent. Is it at the same time in earth's frame, or in the spaceship's frame? It can't be both. Algebraist 18:26, 4 January 2009 (UTC)

Let's say at the same time in earth's frame. And I also realized that I have phrased the final question incorrectly, allow me to rephrase it as follows:

If both babies live to be 75 years old in their proper times, will B see herself die ahead of A, since B sees A's clock dilated; or will A see herself die ahead of B, since A also sees B's clock dilated?

Thanks.

76.68.9.253 (talk) 20:07, 4 January 2009 (UTC)

after reading the Relativity of simultaneity article suggested by the Algebraist, I've reached a disturbing conclusion: B will see herself die ahead of A in B's frame of reference, and A will see herself die ahead of B in A's frame of reference, and BOTH ARE CORRECT!!! In fact, since A and B are separated in space, there will always exist frames of reference in which A died earlier than B, and frames of reference in which B died earlier than A, both observations are correct. Am I right?

Thanks,

76.68.9.253 (talk) 20:16, 4 January 2009 (UTC)

Yes - the disturbing thing about relativity is the end of the concept of 'simultaneous'. Observers moving at different speeds will come to different conclusions about the order that events happen...and the death of the twins is no exception to that. There are yet weirder things to consider because it's not just time that gets distorted - mass and distance also get changed. The Ladder paradox (and the related man-falling-into-hole paradox) really hurt my brain. SteveBaker (talk) 21:52, 4 January 2009 (UTC)

Thanks for the article, SteveBaker. My brain is already popping. 70.52.150.155 (talk) 20:58, 5 January 2009 (UTC)

Asteroid orbital elements

Hi. I'm looking for orbital elements for the asteroid 99942 Apophis. I need an online source from which I can copy-and-paste in a manner similar to this. I can easily find comet data such as from here, but I cannot find the asteroid data, can someone help search for such a site? Thanks. ~AH1^(TCU) 15:45, 4 January 2009 (UTC)

There is the JPL Small-Body Database browser. (Which I notice has fixed the problem with their precision field, since the last time it was mentioned here.) I think that gives you most of what you're looking for, but I'm no astronomer, so don't take my word for it. APL (talk) 16:30, 4 January 2009 (UTC)

The JPL site linked above gives the orbital elements, but not in a convenient format for cut and paste. Try going to the Minor Planet & Comet Ephemeris Service. Enter 99942 Apophis in the box below "Enter a list of designations..." and then scroll down and select the check box next to MPC 8-line for the format. You can leave the rest of the form set to the defaults. Click on the Get Ephemerides... button. The formatted orbital elements are at the top of the page. Here is a sample of the data that can be entered in the sky mapping website:

(99942) Apophis
Epoch 2008 Nov. 30.0 TT = JDT 2454800.5                 MPC
M 254.96401              (2000.0)            P               Q
n   1.11252452     Peri.  126.40626     +0.87279766     +0.48748942             T = 2454894.91229 JDT
a   0.9224220      Node   204.44527     -0.46434998     +0.81417405             q =     0.7460436
e   0.1912123      Incl.    3.33142     -0.15034405     +0.31539607    Earth MOID = 0.00052 AU
P   0.89           H   19.2           G   0.15           U   1
From 989 observations at 2 oppositions, 2004-2006, mean residual 0".47.

Thanks! ~AH1^(TCU) 23:26, 7 January 2009 (UTC)

Note that I added the name (99942) Apophis on the first line. --mikeu ^talk 16:26, 7 January 2009 (UTC)

Please identify this flower

Please identify the species of this flower, so that I can (or you can) include that in the image description page. --Kprateek88(Talk | Contribs) 16:37, 4 January 2009 (UTC)

It will dramatically assist identification if you specify the time and location that you took this photo. Nimur (talk) 17:49, 4 January 2009 (UTC)

Metadata on the description page says 28 December 2008 in Indore, India — Matt Eason ^{(Talk &#149; Contribs)} 18:10, 4 January 2009 (UTC)

That's right. This was in some sort of a garden, so it's likely that this flower was planted there (as opposed to occurring naturally). --Kprateek88 (talk) 11:14, 5 January 2009 (UTC)

It looks like some kind of Coreopsis. There are several different species and cultivars that are commonly grown in gardens throughout the world.--Eriastrum (talk) 21:14, 4 January 2009 (UTC)

According to Wikicommons, where this photo can be seen, it is a species of cosmos. [17] . Richard Avery (talk) 08:47, 5 January 2009 (UTC)

Special relativity, time dilation, practice?

(In responese to the Time dilation question above) So, equipment available today could use a laser to broadcast pulses and a receiver to time them at enormous speeds. My wireless receiver at home goes at 384,000,000 binary digits per second (its pretty advanced but its a non-expensive Motorola bluetooth type thing). Is it not possible to set up a supersonic craft with a transmitter/reciever and one on the ground which stay in line with each other and measure timing variations relative to speed? Surely if the speed of light would cause 8 x reduction in time-speed (is it 8 in Einsteins theories?) the fluctuations at double the speed of sound (which planes are capable of) could be measured by todays extremely capable hardware? Any notable time-speed theory experiments? ~ R.T.G 17:42, 4 January 2009 (UTC)

We can doa lot better than that. Please see the GPS article. the GPS system works by placing extremely accurate clocks in extremely well-known orbits. Orbital speed is a lot faster than aircraft speed. The GPS system must account for both the slowing predicted by special relativity and for the speed-up caused by general relativity. The fact that the system's accuracy requires these corrections is a proof that the effects exist. -Arch dude (talk) 18:14, 4 January 2009 (UTC)

It does say that at GPS#Relativity thanks Arch dude ~ R.T.G 19:00, 4 January 2009 (UTC)

The specific experiment you describe has also been done several times - flying an atomic clock around the world on airliners is sufficient to produce measurable time differences with one sitting on the ground. According to [18]:

"Two scientists, Hafele and Keating, did the most direct test of relativity possible, in 1971 they flew one set of atomic clocks around the world on a commercial jet liner and then compared them to a reference set left behind on the ground. The scientists flew the clocks around the world twice, once east to west and then west to east."

"The atomic clocks on the planes flying east lost 184 nanoseconds ... They gained 125 nanoseconds due to the gravitational red shift. The planes flying west gained 96 nanoseconds due to their motion and gained 177 nanoseconds due to gravity. The measured effects were within 10% of the predicted effects which was within the 20% error in the experimental technique. (The effect of gravitational redshift has now been confirmed to better than 1%)"

SteveBaker (talk) 21:43, 4 January 2009 (UTC)

It always seemed to me to be discussed as an unproven theory. Doesn't the fact that the direction of the plane affected the amount of difference show some proof that gravity and friction were not the only forces at work? Maybe not proof of a time-material but at least shows a strength in cosmic (or other) influences in motion. Wow. That will be their warp drive. ~ R.T.G 01:05, 6 January 2009 (UTC)

Oh - no - far from it! It's an exceedingly well proven theory - there have been hundreds (at least) of completely different tests of relativity - and they all come out right on the money. The reason the direction matters in the airplane experiment is because the earth is rotating with one plane and against the other - so their relative velocities are not the same. As the article says - the results were within 10% of the predicted value - within error estimates of 20% - which means "it worked!". There are plenty of scientific theories to be skeptical about - but relativity shouldn't be high on your doubt-list! SteveBaker (talk) 02:11, 6 January 2009 (UTC)

What is the difference between neuronal circuitry and neural circuitry?

Hi: I'm working on the Wiki article about the essay "Is Google Making Us Stupid?" and I have been unable to determine the difference between the adjectives neural and neuronal. The question has also been posed at WikiAnswers by someone other than me. If you could enlighten me about the differences I would appreciate it. Nicholas Carr, in his essay "Is Google Making Us Stupid?", says "Over the past few years I’ve had an uncomfortable sense that someone, or something, has been tinkering with my brain, remapping the neural circuitry, reprogramming the memory." However, in an email, he told me that "Given what we know now about neuroplasticity, it seems certain that internet use is changing our neuronal circuitry." So he even seems to use the terms "neural circuitry" and "neuronal circuitry" interchangeably. The same goes for "neural network" and "neuronal network", as well as "neural level" and "neuronal level"—terms which are used on page 117 of Norman Doidge's book The Brain That Changes Itself without any apparent differences. I can't see any at least. Sincerely, Manhattan Samurai (talk) 19:18, 4 January 2009 (UTC)

"Neural" means "of, relating to, or affecting a nerve or the nervous system" (Merriam Webster), whereas "neuronal" means "of, or relating to a neuron" (Wictionary - MW just redirects to "neuron"). That is, "neural" involves the large scale nervous system, whereas "neuronal" involves the small scale nerve cells (neurons). However, since the nervous system is made up of neurons, something that relates to or affects the neurons will relate to or affect the nervous system as well, so the to can be taken as synonyms in most cases. I'd use "neural" in most cases (being the older and more widely used word), only using "neuronal" when I wanted to stress the "on the cellular level" connotation. -- 128.104.112.113 (talk) 20:05, 4 January 2009 (UTC)

I agree. In my personal experience as a jobbing neuroscientist, they are often used interchangably. I get the impression neuronal tends to be used more often when referring to specific, defined circuits (because it pertains to specific neurons), whereas neural is more often used when referring to more complex, undefined circuits (because it pertains to the nervous system). That said, there are plenty of examples of the opposite [19]. I'd just choose one, and stick with it. Rockpocket 20:17, 4 January 2009 (UTC)

Thanks. I too came to a feeling that neuronal was low-level and neural was high-level. However, sticking to one or the other is out of the question considering everyone I have come across uses both terms.Manhattan Samurai (talk) 21:25, 4 January 2009 (UTC)

I meant stick with one type of usage in the article (unless in a quote), per WP:MOS. Since there is significant ambiguity, it probably doesn't matter which is used in the article, but consistency would certainly make it easier for the reader. Rockpocket 22:05, 4 January 2009 (UTC)

I actually would like to give brief definitions within emdashes for when I use either "neuronal circuit" or "neural circuit". I really think there is a very specific definition for both terms and they just haven't been sufficiently made explicit yet. I'm coming to my own intuitive definitions. I mean neuronal circuits would probably be very much within the synapses of a neuronal grouping, right? While neural circuits would be higher level functions that are using several different components of different brain areas to produce higher level functions like reading and writing, or interpreting symbols, or something like that.Manhattan Samurai (talk) 13:33, 6 January 2009 (UTC)

It's very puzzling. I mean at a neuronal level you would have neuronal links, which could form neuronal circuits within neuronal networks, right? And at a neural level you would have neural links, which could form neural circuits within neural networks. You would think those would be entirely different things but maybe not. What is a neuronal link? A link between two neurons? What is a neural link? A link between two nerves? Mysterious.Manhattan Samurai (talk) 18:43, 6 January 2009 (UTC)

On page 249 of The Brain That Changes Itself Doidge, in writing about old-think on the brain's inability to rejuvenate itself, "Besides, scientists asked, how could a new neuron enter a complex, existing neuronal network and create a thousand synaptic connections without causing chaos in that network? The human brain was assumed to be a closed system." Does the context suggest whether or not you should use neural or neuronal?Manhattan Samurai (talk) 22:37, 6 January 2009 (UTC)

Yes, intuitively I would say the its context specific and that particular uses makes sense to me. This example is pretty specific, right? A single neuron is being discussed and, with its interaction with other, local neurons, hence together they form a neuronal network. If I was talking in more abstract, generalist terms ("the brain largely remains mystery. Simple molecular inputs are integrated into circuits that talk to each other in an unfeasibly complex neural network, the result being a coherent output"), then neural network would sound better. But I think its a mistake trying to pin down a precise and different definition for each. Its more of a semantic issue, I feel. Rockpocket 08:13, 7 January 2009 (UTC)

Okay, and this follows somewhat from what Looie496 said at WikiProject Neuroscience: "since most neuroscientists believe that memory is stored in the brain by altering connections between neurons, it follows that anything whatsoever that you remember produces a change in neural circuitry." Thanks again, Manhattan Samurai (talk) 09:34, 7 January 2009 (UTC)

Looie496 had said, right before the above paraphrase, that neural is the more common usage of the two terms. But I get it, and I have a method that I can apply. Anything high-level will need the word neural, but anything low-level can use the word neuronal. Should this nuance be written up somewhere? It seems to need to be addressed definitively.Manhattan Samurai (talk) 12:45, 7 January 2009 (UTC)

How often do transposons jump?

Depending on the type, transposons can either jump around in the genome or they can proliferate by copy-and-pasting. I wonder how often this happens. Will a typical active transposon in a cell of my body jump once an hour, or once a month, or is it a rare event happening only a few times in my body in my life, or even rarer than that? I suppose the rate depends on the type of cell? Thanks, AxelBoldt (talk) 22:12, 4 January 2009 (UTC)

That is a really difficult question to answer, because actually observing transposition as it happens is like looking for a needle jumping around a haystack. Moreover different transposons will have very different rates of transposition, so generalizing is probably not helpful.

Nevertheless, some studies in Saccharomyces cerevisiae Ty retrotransposons have been carried out (we only have an article on Ty5, but the one they used was Ty1). The experiments were quite complicated, and contain a few assumptions that may or may not be accurate, but the bottom line was that a Ty1 transposition would occur in 1% of cell divisions observed. Given the number of transposons in the genome (and assuming each could function equally well in their assay), they calculated that the mean rate of transposition per Ty1 element was between 10^-4 and 10^-3 per generation. Therefore, calculating in a few more assumptions, on average Ty1's transpose once every 2000 to 20,000 hours. Thats between once every 2.5 months, and once every 3 years.

The authors predict that this rate estimate is probably erring towards the high side, and it could be more than 10-fold slower but not likely to be faster. Its also worth noting that Ty1 appears to have a higher transposition rate than Ty2 in their assays system (by as much as 25:1), and so could be an unusually active transposon and therefore not typical. Then you have to ask yourself, how applicable is this to human transposons? Rockpocket 00:07, 5 January 2009 (UTC)

Thanks a lot, that was a very thorough answer. If we take the rate "once every couple of years" as a rough estimate, another important piece of information would be the total number of active transposons in the human genome. Would you like to add some of this to the transposon article? I could also do it if you give me the reference for the paper you mentioned. Cheers, AxelBoldt (talk) 02:01, 6 January 2009 (UTC)

Sure, the primary reference is PMID 17815421 (though PMID 1662752 also discusses the data). Rockpocket 06:52, 6 January 2009 (UTC)

Rock, do you have any information on what actually causes a transposition event? It's always seemed to me that the jumpable transposon should be created either once per gene transcription (or once per DNA replication, depending on the type) - or never at all, if there's no promoter sequence for it. Is it just an accidental transcription, is there an active system to repress transposons, what? I may have just spotted an interesting paper at PMID 2851719, but if you have any general information, it's appreciated! Franamax (talk) 07:20, 6 January 2009 (UTC)

And to follow up on a brief look at the paper I just mentioned, "regulation of Ty transposition occurs at a posttranscriptional level" seems to imply an active system for repression - so do you know what that system is? and that paper involves dropping in GAL1 promoters to fire up the Ty elements - so again, what activates them in the wild? Franamax (talk) 07:27, 6 January 2009 (UTC)

I think the mechanism of transposition induction is likely to vary between Class I and Class II transposons. I'm far from an expert on the subject (though I do find them fascinating), but I know there are some examples of inducing agents. Copia has been shown to be responsive to a "variety of environmental stresses" [20] (possibly because it contains heat shock promotor-like sequences.) Both the Tys in cerevisiae and IS₁₀ (in E. coli) are induced by DNA damage via UV light or 4-nitroquinoline-1-oxide treatment. [21] I'm not sure the mechanism for this has been elucidated, but it appears to be under the control of the SOS response in bacteria. [22] So it appears that at least one endogenous mechanism is stress related, which kind of makes sense, I suppose.

There are both epigenetic, and genetic mechanisms are involved in repression of transposition. An example of the former: biotinylation of histones appear to repress transposition in some systems [23] In the case of the P element, the presence of a genes that inhibit transposase is sufficient to inhibit transposition (and, it follows, genes that promote transposase expression will induce transposition). I don't know whether there is a co-ordinated "active repression system" per se, or its simply the case that the transposons are by default quite stable, or that their RNA usually gets degraded by nonsense mediated decay, and there has to be specific (and quite rare) circumstances for them to escape that and fully retrotranspose. Rockpocket 08:25, 6 January 2009 (UTC)

Thanks. Fascinating? Yes, maximally so. I like the idea that HSP's would induce transposons, along the lines of "we've got a problem here, time to shake things up to see if we can find a new solution". I recall a paper about induction of HSP90 in A. thaliana which produced generationally stable phenotype changes - you've provided a clue to a possible mechanism. I recall also that I've seen some evidence that the homeobox genes seem particularly resistant to transposon insertions (which probably is the only thing keeping us from getting angel wings :). A vastly interesting topic - we seem to be getting closer and closer to adding a {{historical}} tag to the Junk DNA article. :) Franamax (talk) 09:02, 6 January 2009 (UTC)

I agree, a HSP-mediated mechanism makes intuitive sense to me. It hints at how transposons could play a role in generating genomic diversity at times of changing selective pressures. Rockpocket 07:55, 7 January 2009 (UTC)

This article describes piRNA and siRNA as active defense mechanisms against transposable elements. AxelBoldt (talk) 23:11, 9 January 2009 (UTC)

Hard-boiled eggs

When peeling a hard-boiled egg, sometimes the membrane is very hard to detach from the flesh, yet other times it comes away readily. What causes this difference, and is there any way to ensure that it peels away easily more often? (I am referring to hens' eggs in particular). DuncanHill (talk) 23:15, 4 January 2009 (UTC)

For hens' eggs, I was shown when I was a child that after boiling, you must quickly dunk the eggs in cold water specifically to make them easier to peel. I don't know if that works for roosters' eggs, so it is good you are only interested in hens' eggs. -- kainaw™ 01:23, 5 January 2009 (UTC)

Yes very good.... I of course intended the eggs of Gallus gallus, rather than those of any other fowl. DuncanHill (talk) 01:43, 5 January 2009 (UTC)

Yeah, that'll do the trick. The idea is that the soft insides of the egg contract in the cold water, while the hard shell doesn't. This makes it easier to peel the shell off. -- Captain Disdain (talk) 01:38, 5 January 2009 (UTC)

It's not the hard shell I'm worried about, but rather the soft and flexible membrane. DuncanHill (talk) 01:44, 5 January 2009 (UTC)

Are not roosters male birds that don't lay eggs?--GreenSpigot (talk) 01:45, 5 January 2009 (UTC)

Indeed, Kainaw was pointing out the redundancy of my specifying hens' eggs. DuncanHill (talk) 01:47, 5 January 2009 (UTC)

Sometimes a little redundancy doesn't hurt. At least you won't get hard-boiled snake's eggs. The dunking treatment is supposed to make the inside of the egg contract, while leaving the membrane adhering to the shell, so it is indeed designed to deal with the membrane. The trick is to dunk and then peel rather rapidly, as if you leave the egg sitting around for a while you loose the advantage of the contraction of its insides and the membranes re-adhere. - Nunh-huh 02:32, 5 January 2009 (UTC)

I just figured that he specified hen's eggs in case someone might have thought to ask for him to specify between chicken eggs and, for example, quail eggs. Dismas|^(talk) 03:07, 5 January 2009 (UTC)

Well, yes, but the quail that lays the eggs is the hen... - Nunh-huh 03:55, 5 January 2009 (UTC)

Dismas is right, I meant chicken eggs, as opposed to those of other fowl. I was using the word hen in its common usage to mean a female Gallus gallus. By the way, we have cocks here, not roosters. DuncanHill (talk) 11:56, 5 January 2009 (UTC)

Ah, nothing like Ref Desk pedantry ("I am soooo clever!") to completely derail something. And if you hadn't specified chicken eggs, you'd probably get some response about how duck eggs might be totally different, and thus there's no way to answer the question without more information. (Can you tell I have grown quite tired of this sort of "wit"?) --98.217.8.46 (talk) 15:47, 5 January 2009 (UTC)

Your complaint would have some weight if the comment you are complaining about didn't supply an answer. However, as can be seen, the main substance of the comment contained an answer that has been verified by others as being correct. -- kainaw™ 02:52, 6 January 2009 (UTC)

Don't hard-boil chicken eggs. Eggs plus cold water, bring to a boil, remove from heat, wait for 17 (seventeen) minutes, remove eggs from hot water and put into cool water. Fresh eggs will always be more difficult to peel than 2 to 3 week old eggs - its the law! hydnjo talk 02:38, 5 January 2009 (UTC)

I'd like to speak in favor of the 70° egg (see [24]). Some prefer 65° or 67° eggs, but for any of these you really need a water-bath with a thermostat. - Nunh-huh 02:46, 5 January 2009 (UTC)

The biggest factor I've found is using the aged eggs like Hydnjo suggestion: 2 to 3 weeks old. Anythingapplied (talk) 19:20, 5 January 2009 (UTC)

The only thing tasiter than a hard boiled Gallus gallus hen egg with a little salt on it is a devilled one of same. I've never had me fill of 'em. Yum!. Edison (talk) 04:12, 6 January 2009 (UTC)

ZMF in special relativity

If the centre of mass of a two body system has non-zero momentum what is the simplest way to calculate the energy available for particle creation (the total energy of the particles in the ZMF less their rest energy) from data of the particles energy in the lab frame.

The only method I can see that I am sure that works is to calculate the particles velocitys from their energys, then using the rule for velocity addition, caluclate their velocities in the lab frame, and then from this calculate their energies in the ZMF. However due to the need to calculate the velocity of the ZMF. And the equations get extremely complex and messy and I am sure there must be a simpler way. Is their a quick way to calculate the energy stored in the system as moving the centre of mass? —Preceding unsigned comment added by 84.92.32.38 (talk) 23:31, 4 January 2009 (UTC)

Unfortunately I don't know an easy way, as their always seem to occur quartic equations. But at least they can be solved in radicals. Icek (talk) 18:09, 5 January 2009 (UTC)

There is a way to do this using four-vectors, in particular, the four-momentum. The four-momentum is special because a Minkowski norm of a four-momentum vector is invariant under translation into different frames of reference. I'll state (without proof) that the total energy available for particle creation is ${\sqrt {-(p_{1}+p_{2})\cdot (p_{1}+p_{2})}}$, where $p_{1}$ is particle 1's four-momentum and $p_{2}$ is particle 1's four-momentum.

Expanding this out using the distributive law (which holds for the Minkowski inner product), this because ${\sqrt {(-p_{1}^{2}-p_{2}^{2}-2p_{1}\cdot p_{2})}}$. Evaluating the Minkowski inner products results in: ${\sqrt {(m_{1}^{2}+m_{2}^{2}+2(E_{1}E_{2}-{\vec {p_{1}}}\cdot {\vec {p_{2}}}))}}$. For reference, $p_{1}^{2}$ was evaluated in particle 1's rest frame, $p_{2}^{2}$ was evaluated in particle 2's rest frame and $p_{1}\cdot p_{2}$ was evaluated in the lab frame. Also, note that ${\vec {p_{1}}}$ and ${\vec {p_{2}}}$ are ordinary three-vectors (ie. normal momenta). If $\theta$ is the angle between the two particles then the total energy available for particle creation is ${\sqrt {(m_{1}^{2}+m_{2}^{2}+2(E_{1}E_{2}-\left\vert {\vec {p_{1}}}\right\vert \left\vert {\vec {p_{2}}}\right\vert \cos \theta ))}}$. Knowing the particles' rest mass and energies in the lab frame, you can calculate the magnitude of their three-momenta in the lab frame and just substitute into the most recent equation.

To prove my previous statement (that the total energy available is just the square root of the sum of four-momenta dotted with itself), let the lab frame be the ZMF so that the 3-momenta are equal in magnitude but opposite in direction. Then you should get ${\sqrt {-(p_{1}+p_{2})\cdot (p_{1}+p_{2})}}={\sqrt {E_{1}^{2}+E_{2}^{2}}}$ (in the ZMF). Someone42 (talk) 11:24, 6 January 2009 (UTC)

I see there is a more elegant way than what I suggested ... just a small correction: The right hand side of the last equation should be ${\sqrt {(E_{1}+E_{2})^{2}}}$

January 5

Possible Meteorite strike

Looking at Southern Russia on google earth Two round lakes caught my eye.North 52.44'58.11" East 78.37'05.37" Bolshove lake The other lake not sure the name but its @ North 54.35'17.46" East 71.45'21.10"Nasa has an icon in the area called KULUNDA STEPPE Could these lakes be Craters from meteorites? They are almost prefect circles.My email is <removed to prevent spam> Thanks. —Preceding unsigned comment added by 5544mik (talk • contribs) 01:02, 5 January 2009 (UTC)

Not answering the question, but here's a quick link to the location: 52.749475°N 78.618158°E / 52.749475; 78.618158. [ cycle~ ] (talk), 02:01, 5 January 2009 (UTC)

I'm no expert - but wouldn't there be raised edges if they were craters? Where did all of the ejected material go? The agriculture around these lakes appears to go right up to the edge of the lakes without interruption - which seems unlikely unless the edges of the lakes are dead flat...but I could easily be wrong. SteveBaker (talk) 04:07, 5 January 2009 (UTC)

While it's certainly plausible, I wouldn't say its the most likely, or even one of the top 3 most likely methods of formation for these lakes. Just because a lake is circular does not mean that it is a crater lake; I'm sure most lakes in flat-terrain areas are roughly circular in shape. They appear similar to Kettle ponds, although I doubt glaciers would reach that far south in recent eras. It could be an old shaft mine which has filled with water (although this is unlikely given the flatness of the nearby terrain). It could be a man-made reservoir or irrigation lake. It could also just be a natural dip in the terrain which is below the current water table. Without knowing the depth of the lake, it is hard to make a judgment in any case. -RunningOnBrains 20:40, 5 January 2009 (UTC)

The maximum extension of the Wisconsin glaciation, about 21,000 years ago, terminated roughly at that latitude in that region (though in North America it extended quite a bit further, to about 40°N). I'm not an earth scientist of any kind, but I would have to agree that these are probably Kettle ponds. In fact, they're very similar to Lake Ronkonkoma (the lake, not the hamlet), which isn't far from where I live. – ClockworkSoul 16:45, 6 January 2009 (UTC)

An old eroded crater may not have a raised rim. —Tamfang (talk) 20:31, 5 January 2009 (UTC)

I don't see anything round enough to scream 'crater'. —Tamfang (talk) 20:31, 5 January 2009 (UTC)

See the Earth Impact Database. Under Criteria (for determining if a geological feature is an impact structure) there is a note under #4 Morphology that states "a circular structure alone is not sufficient to claim impact structure status" due to other processes on the earth that can cause circular features. It is possible that it is an impact, but the only way to distinguish between other causes is to examine the geology on the ground and look for evidence such as Shatter cones or Planar deformation features. --mikeu ^talk 15:38, 7 January 2009 (UTC)

Ray that stops internal-combustion engines

I was browsing through an old newspaper online and found an article about supposed Nazi secret weapons. The article (Hurt Doberer, "New Reich Weapon May Be Dust Bomb, New York Times, 15 October 1939, p. 36). went over some things that th Nazis had claimed to invent in the 1930s, and points out that none of them are that spectacular or were original to the Germans. The last entry was:

Ray Z—the ray that could stop an internal combustion engine. (This secret also was shared. And, anyway, the ray, though effective when dealing with a near-by motor-car engine, ha never been effective against an airplane.)

I've never heard of such a thing. I googled "Ray Z" and "Z-Ray" and found, well, nothing relevant. Anybody have a clue what this refers to? --98.217.8.46 (talk) 01:59, 5 January 2009 (UTC)

Electromagnetic pulse? Did they know how to generate one by non-nuclear means back then? I dunno. --Kurt Shaped Box (talk) 02:17, 5 January 2009 (UTC)

I figure that everyone who ever went to school to learn to work on radars (the big ones that track aircraft) will have heard a story about a radar killing engines or catching a camera shop on fire. The claim is that the electromagnetic radiation from the radar will cause all spark plugs to fire at once - killing the engine. I never attempted anything of the sort. However, I have seen fluorescent bulbs light up only through the power of the radar flowing through the air. Come to think of it, it also caused my radio to turn on and faintly play some music as the radar sweep passed by. I had it sitting on top of the cabinets above my work desk, so it was above the safe altitude. -- kainaw™ 02:53, 5 January 2009 (UTC)

There's no need to worry. If the Nazis do indeed invent such a weapon, our esteemed scientist Nikola Tesla has already invented a death ray capable of shooting planes out of the sky and annialating entire armys. [25] 216.239.234.196 (talk) 13:27, 5 January 2009 (UTC)

---

So the answer is, basically, nobody knows, really? Except maybe radar or EMP, neither of which existed at energies in which this would be possible (much less a routine thing) in 1939? What impresses me about the article is the smug way the author shrugs off this idea as something both the Nazis developed and that many other people developed. Obviously law enforcement agencies today would be pretty interested in something that could easily stop car engines (it would make car chases a thing of the past, at no risk to the officer or the public). --98.217.8.46 (talk) 19:20, 5 January 2009 (UTC)

Could this have been written by the same NYT ignoramus who mocked Robert Goddard? Moral: never ever fully trust what you read in the papers about science. Clarityfiend (talk) 20:54, 5 January 2009 (UTC)

The cops are interested in the idea. See "Stopping Cars with Radiation" (2007). --Heron (talk) 21:37, 5 January 2009 (UTC)

That device attacks the microprocessors controlling modern cars, which weren't around during the second World War. I doubt even an EMP could have much of an effect on an old-fashioned internal combustion engine; EMPs affect tiny sensitive circuits used in computers and such, not levers and pistons and other mechanical components.

I don't know what "near-by motor-car engine" is supposed to mean, but I'd say any device that can stop a vehicle reliably is tremendously useful, unless "near-by" means going up to the car with hand tools and disassembling the engine. --Bowlhover (talk) 05:35, 6 January 2009 (UTC)

There was a TV show recently ("Prototype this" IIRC) which was somewhat successful in stopping cars by releasing a large cloud of an inert gas (I think they were using CO2) right in front of them to briefly cut off the oxygen flow to the engine. But I agree - using an EMP to try to stop a WWII-era car would be fruitless. Even my '71 VW bug has no significant electronics in it - an EMP might take out the radio - but it's not gonna stop the engine. It really wasn't until about the 1980's or so that EMP-sensitive electronics started to appear in most cars. Perhaps a really large induction coil - buried under the road and set off by the weight of the car pushing down on a switch could make the sparkplugs fire prematurely - or maybe do something nasty to the alternator - but a car moving at speed would recover from that and restart almost immediately. A bunch of tyre spikes would have been far more practical. But an induction coil would have been in reach of German science & engineering of the 1940's...but it's hardly a "ray" that you could selectively aim from a long-ish distance. The inverse square law is a harsh mistress! If they could have done that - then sticking it on an aircraft to take out incoming fighters would be much more interesting to them than taking out cars. SteveBaker (talk) 15:51, 6 January 2009 (UTC)

Are there any Nobel winning scientists in baseball?

Seems a bit far fetched, believe it or not, - not all jocks are stupid. I figured at least one of them cured the cancer of a teammate or two. Has anyone ever abandoned our beloved game of baseball and followed a noble scientific pursuit? Has any big leaguer ever broke out a chemistry set in the locker room?--Baseball and and and Popcorn Fanatic (talk) 02:29, 5 January 2009 (UTC)

Frank Sherwood Rowland played at College level (for Ohio Wesleyan University), but the Laureate who is was the best baseball player is probably Lester Pearson (who wasn't a scientist, but won the Nobel Peace Prize in '57). He was a semi-pro who played for the Guelph Maple Leafs. Rockpocket 03:32, 5 January 2009 (UTC)

Not a Nobel winner, but Kerry Ligtenberg (formerly of the Atlanta Braves, among others) has a degree in chemical engineering: http://mlb.mlb.com/team/player.jsp?player_id=117763 —Preceding unsigned comment added by 24.98.239.50 (talk) 03:44, 5 January 2009 (UTC)

Dr. Bobby Brown was an all-star third baseman for the New York Yankees, and studied medicine while still an active player. He became a cardiologist and surgeon with a successful practice for several decades, then returned to baseball after retiring from medicine as President of the American League. — Michael J 23:27, 5 January 2009 (UTC)

Titanium Knives vs. Stainless Steel

I saw some Titanium kitchen knives on sale at a houseware store this weekend. They were rather expensive, but very nice looking. Are there any pros or cons of using titanium for knives? Do they hold their edge longer than normal stainless steel? Are they sharper? --71.158.216.23 (talk) 06:24, 5 January 2009 (UTC)

This blog post seems to have some good points. Dismas|^(talk) 07:00, 5 January 2009 (UTC)

Aside from the points mentioned there, titanium is also not as dense as steel; according to titanium and iron, its density is only 4.5 g/cm^3, compared to iron's 7.9 g/cm^3. (Stainless steel's density is similar to that of iron since it is only a few percent carbon.) For that reason, it's sometimes used for mountain equipment. See the camping utensils here, for example. Of course, I doubt your houseware store was targeting mountaineers, but titanium offers a much greater advantage in mountain equipment than it does in a regular kitchen. --Bowlhover (talk) 09:08, 5 January 2009 (UTC)

According to our article on Mohs scale of mineral hardness, hardened steel is quite a bit harder than titanium (2-3 times harder on the scale of absolute hardness). I'm not a materials scientist, but I believe blade hardness would be directly correlated with how well it holds its edge. --Bmk (talk) 13:44, 5 January 2009 (UTC)

Harder materials are less likely to wear down, but more likely to chip or crack. Japanese swords often combine harder steel for the cutting edge with softer supporting steel, to get the best benefits of both. StuRat (talk) 18:06, 5 January 2009 (UTC)

I don't think I'll be using any Samurai swords in the kitchen! --71.158.216.23 (talk) 03:02, 6 January 2009 (UTC)

Not even a Ginsu ? But what if you need to cut a can in half and then slice tomatoes with the same knife ? StuRat (talk) 05:06, 6 January 2009 (UTC)

Daytime Conflict with clock time

The day time is not exactly equal to 24 hours .It is short of 4 mints a day .But th eclock shows exactly 24 hours then how will this difference keep correct. —Preceding unsigned comment added by 123.237.213.65 (talk) 07:54, 5 January 2009 (UTC)

See sidereal day. The clocks are based on the Sun's apparent movement; every 24 hours, the Sun returns to approximately the same place in the sky. Because Earth is also orbiting the Sun, it only takes 23 hours and 56 minutes for a star to return to the same position. That's why a sidereal day is 23 hours and 56 minutes. To see how this works, look at the diagram in the article I linked; it explains the concept much more concisely than I can using words. --Bowlhover (talk) 09:34, 5 January 2009 (UTC)

Headphones jack or line out?

I am going to record the audio signal from a reel-to-reel tape recorder. It offers both a headphones jack and some kind of line out DIN connectors (and arc of 5 pins or so) on the back. Which option would give me the best result?

For AD-conversion, I'm thinking about using a gramophone, which connects to a computer via USB, and which has a connector for taking in an external audio signal. If it makes my question easier to answer, we can assume that I'll connect the reel-to-reel directly to the simple sound card of the computer instead of to the gramphone. —Bromskloss (talk) 09:50, 5 January 2009 (UTC)

Probably the LINE connections would give the best impedance match - but IMHO, you should try both and see what gives you the best results - you won't break anything by doing that. Old tape recorders tend to be pretty well-behaved. The things that are a pain to interface to is old record players...but I guess you've already solved that one! SteveBaker (talk) 14:51, 5 January 2009 (UTC)

Thanks for taking the time. Impedance matching, does it really matter? The input impedance of the receiving equipment is supposed to be "very high" anyway, isn't it? As for the "pain", do you refer to RIAA equalization? It's convenient not having to fiddle with that. —Bromskloss (talk) 15:06, 5 January 2009 (UTC)

I would use the line out thereby bypassing the headphone amp (which may introduce some distortion). Impedances do not have to be matched as long as you are not overloading the output of the tape recorder. Direct input to the sound card should not be a problem.--79.75.49.50 (talk) 16:56, 5 January 2009 (UTC)

We seek to load up an output. The input impedance of the thing you are connecting to should be as high as or higher than the output impedance of the source, and never lower, to avoid distortion and damage. What does a gramophone to do with electronic audio? That is a British term for a wind up disc phonograph with purely acoustic output. Edison (talk) 04:07, 6 January 2009 (UTC)

Ah, I did have my doubts I was using the right word. So, phonograph it is. —Bromskloss (talk) 10:03, 6 January 2009 (UTC)

Brit's wouldn't say "phonograph" either - "Record Player" or "Turntable". But it's OK - most of us speak American fairly fluently. SteveBaker (talk) 15:41, 6 January 2009 (UTC)

Thanks. I strive to follow British conventions unless I am speaking only with Americans so this is useful information to me. —Bromskloss (talk) 19:34, 6 January 2009 (UTC)

How long will it take for Pluto to clear its neighborhood?

I was just wondering if anyone's ever tried to figure out how long (persumably, millions or billions?) of years for Pluto (through collisions with meteors, comets, asteroids, etc.) to clear its neighborhood and become a "planet"? —Preceding unsigned comment added by 216.239.234.196 (talk) 13:19, 5 January 2009 (UTC)

I don't know the answer to your question - but I'm not sure that this would ever happen. Clearing the neighborhood would be a major deal - as our article on Pluto points out, Pluto's mass is only 7% of the mass of the other objects in its orbit. Earth's mass, by contrast, is 1.7 million times the remaining mass in its own orbit. So Pluto would have to get something like 14 times bigger before it could be considered to be a planet under the present rules. Of course that would depend on whether Charon would gain mass proportionately or disproportionately to Pluto - and whether that large weight gain would cause their orbits to misbehave and one to collide with the other or break apart and form yet more debris to be swept up. Worse still - Pluto/Charon's orbit around the sun is retrograde and tilted at a crazy angle - if much of the debris turns out to be in the plane of the ecliptic (as one might expect) then Pluto's rare intersections with the ecliptic (just once every 120 years!) would make the opportunities for it to pull in rocks in orbits that intersect somewhat unlikely. So my gut feel is that the answer has to be "a very long time" - possibly longer than the predicted life of the Sun. SteveBaker (talk) 14:44, 5 January 2009 (UTC)

While it may be possible for Pluto's orbit to be cleared (although unlikely for the reasons Steve gives), it wouldn't contain anything we recognise as Pluto by the end of it. Pluto would have to merge with lots of other objects (including ones of comparable size), so only part of the remaining object would be Pluto. Alternatively, lots of objects could be thrown into different orbits, but if that happens there is no reason to believe it would be Pluto that remained, it may well be thrown into a different orbit itself. --Tango (talk) 22:19, 6 January 2009 (UTC)

We need to take into account more than just the mass of pluto. Pluto is in a region of the solar system where neptune dominates. Orbital resonance is an exception to clearing the neighborhood where a number of objects can be trapped in a resonant orbit. [26] But, also see [27] for information about how pluto does influence nearby objects. --mikeu ^talk 16:04, 7 January 2009 (UTC)

how many horsepower can a horse pull with?

how mnay horsepower can a horse pull with? 1? —Preceding unsigned comment added by 79.122.29.166 (talk) 16:03, 5 January 2009 (UTC)

See Horsepower from a horse. Echinoidea (talk) 16:27, 5 January 2009 (UTC)

Ah, that explains it. I've often wondered why a 50 horsepower car has difficulty going up a steep hill, when 50 horses would have no trouble pulling the same car up the same hill. StuRat (talk) 18:00, 5 January 2009 (UTC)

No, that's not the reason. A car is not designed to climb a steep hill. A small tractor has a lot less power, but it can climb the hill because it has a much lower gear ratio and it has cleats on the tires. Similarly, horses can "gear down," and they have adaptive traction control (loosely speaking.) You can raise a large car up a steep incline, or even a vertical cliff, using a 1Hp winch, given the proper gearing. -Arch dude (talk) 02:19, 6 January 2009 (UTC)

I saw a comic once, which clearly stated that one horsepower is defined as the power of the prototype horse in a Parisian archive. ——Bromskloss (talk) 16:22, 5 January 2009 (UTC)

Note that there is a difference between horsepower and torque. --Russoc4 (talk) 02:25, 6 January 2009 (UTC)

When early steam engines were rated in "horse-power" the steam engine promoters were very conservative in rating the engines. Thus a factory owner or mine owner who replaced a horse driving a sweep arm around with a 1 "horsepower" steam engine was pleasantly surprised, and advised his friends to also buy steam engines. Edison (talk) 04:04, 6 January 2009 (UTC)

J/k then when everyone was hooked on steam engines, they began to find their new 1 'horsepower' engines were less and less powerful until they couldn't even pull 1 horse! j/k Nil Einne (talk) 12:10, 8 January 2009 (UTC)

Racemates/racemic mixtures

In my exam specification we know that we have to learn about optical isomers, with dextroenantiomers and laevoentantiomers and why reactions tend to produce racemic mixtures.

I understand these terms, but I do not know why racemic mixtures are formed. Why is one enantiomer not formed more than the other? Note this isn't homework, it's revision. Cheers :) —Cyclonenim (talk · contribs · email) 16:04, 5 January 2009 (UTC)

In many cases, the production may go via an SN1 reaction or similar, in which the intermediate molecule in the reaction actually loses a functional group temporarily - as the carbon center, for a brief moment, only has 3 other groups attached to it any existing chirality at that centre is lost. Even in the case of a bimolecular reaction (such as an SN2 reaction) there is often no real factor that causes the attacking group to come in from one side in preference to another. ~ mazca ^t|c 17:54, 5 January 2009 (UTC)

Er, in a normal S_N2 reaction, there is usually a nearly complete preference for the atacking group to come in opposite to where the leaving group is. That type of reaction usually gives clean inversion of configuration, completely not racemization. DMacks (talk) 04:29, 6 January 2009 (UTC)

You're right, my bad. My chemistry degree is evidently rapidly vacating my brain. :D ~ mazca ^t|c 18:29, 6 January 2009 (UTC)

Genetics

Some traits come in two varieties( for example Mendel's round and wrinkled peas with green and yellow colors)Do all traits for all species come in only two varieties?Justify the answer by explaining the relationship between genes and traits. —Preceding unsigned comment added by Shadnasa (talk • contribs) 17:35, 5 January 2009 (UTC)

This really sounds as if it breaks the "The reference desk will not do your homework for you" rule. -- Aeluwas (talk) 17:43, 5 January 2009 (UTC)

Please do your own homework.

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

All traits come in just two states, such as "blue eyes" and "not blue eyes". :-) StuRat (talk) 17:55, 5 January 2009 (UTC)

You could start by reading the Genetics article. The Quantitative trait article will at least give you the "yes/no" part of your answer. The rest of the question is going to require some basic understanding of genes/proteins and sounds like a good essay to work on. You will find sections on "multifactorial inheritance", "complex traits", "polygenic traits", etc. in any good genetics textbook. As a general rule, if the question says "all", you should automatically suspect that the answer is "NO". The goal here is for you to understand why not. --- Medical geneticist (talk) 19:06, 5 January 2009 (UTC)

Volume controller

I got a fancy new radio for christmas and would like to listen to it at work, however it does not have a headphone jack, only a "line out" jack. The volume knob on the radio does not affect the "line out" signal, and when I plug my headphones in it is super loud. My headphones do have their own volume knob, but the control is not fine enough and I have to turn it to its lowest setting just so it doesn't hurt my ears. So currently I have to choose between super loud, kinda loud, and off. I'm wondering if there is a device I can stick between the radio's line-out jack and my headphones which would allow me to have greater control over the volume, or is there another solution? — jwillbur 18:05, 5 January 2009 (UTC)

Considering how cheap headphones are, you could just buy a set with more precise volume controls. Specifically, look for a volume slider or knob, not a separate "up" and "down" buttons, as that type never seems to have much precision. If you want a free solution, put something between the headphones and your ears which will absorb most of the sound. StuRat (talk) 18:44, 5 January 2009 (UTC)

A volume control is just a variable resistor - if you have any construction skills you could buy a 'potentiometer' (aka: a 'variable resistor' or a 'pot') and wire it up in series with your headphones. That would give you another volume control that you could use to cut the volume from the radio before sending it to the headphones - and the headphone volume control would still operate after that to adjust to personal preference. Sadly, I can't think of any devices that you can just go out and buy that'll do the job. Some radios have either a switch or a menu option to switch the output jack between 'LINE' and 'Headphone' levels - but I guess you've already checked that. SteveBaker (talk) 18:49, 5 January 2009 (UTC)

I would expect a headphone amplifier, like this one, to be an off-the-shelf solution. -- Coneslayer (talk) 20:47, 5 January 2009 (UTC)

Cheap off the shelf solution: [28]--GreenSpigot (talk) 01:29, 6 January 2009 (UTC)

"Line out" outputs should, in general, not be connected to a load (like low impedance headphones) of low impedance. Headphones vary in their electrical characteristics. Excess current might be drawn, and distortion might occur. Manufacturers might have taken this into consideration and used a hardy output stage. A headphone amplifier can solve this problem if it has a high input impedance and a low output impedance, as well as providing a volume control. Some modern audio devices provide equalization to boost the bass to compensate for poor low frequency response by headphones, and this might also be a feature to look for in a separate headphone amp. For a Powerbook G4 audio system, for instance, the headphone impedance is 32 ohms, and the headphone jack (the output) has 10 ohm impedance. The line out or "audio output " jack has a recommended minimum of 1000 ohms impedance for the load connected to it.[29]. Your radio instruction book might state the minimum load for the line out. Edison (talk) 20:45, 6 January 2009 (UTC)

Artificial Gravity

I heard a idea in a sci-fi book one time to create artificial gravity in a space station all you have to do is spin the space station at the right speed so that the Centripetal force pushing you into the outer edge of the space station matches that of gravity on earth. If this is indeed possible, how fast would it have to spin to simulate Earth’s gravity? I suppose it'd be a function of the diameter? Would it be possible to spin fast enough that it would rip anything apart that happen to be in the center? Now that I think about it, this all seems wrong to me since if we choose the station to be the reference point it as the station is stationary and the universe is spinning around it so no force should even be created. Am I thinking about that wrong? Thanks. Anythingapplied (talk) 19:12, 5 January 2009 (UTC)

All this and more is covered in Artificial_gravity#Rotation. Except maybe the bit about tearing something apart in the center, which doesn't seem all that likely to me unless you were spinning it at ridiculously fast rates and the thing in the center was especially prone to being ripped apart (you'd have to spin it at a rate that would be much much much more powerful than any simulated earth gravity, yes? You'd be essentially just creating a giant centrifuge). --98.217.8.46 (talk) 19:13, 5 January 2009 (UTC)

Centripetal force can work to provide artificial gravity. However, there are some reasons why it hasn't been done so far:

1) Since the force of gravity reduces to nothing at the center, that means the apparent force of gravity changes when you move toward or away from the center. Also, for a small station, the distance between your head and feet causes a significant change in apparent gravity. This causes nausea.

2) A rotating station is more difficult to use for docking. Generally, docking would only be possible at the axis, allowing two ships at most, and they would still need to match the station's rotation to dock, which is difficult, but not impossible.

3) Items like solar panels and antennae, which need to point in one direction, either need to be moving constantly relative to the station, which makes for many moving parts to break down, or they would need alternative designs. For the antennae, you could have a separate, nearby, non-rotating antenna ship that always points toward the target, and uses a low-power signal to communicate with the rotating ship with the people on board. The rotating ship could use an omni-directional antenna. For solar panels, you could put them on all sides of the rotating ship, so some are always pointed towards the Sun. This would, of course, increase weight relative to energy produced, but would also provide for redundancy, eliminate the need to use energy to aim them at the Sun and would reduce complexity which would be likely to cause failures.

4) Space walks away from the axis wouldn't work, as the astronauts would be pushed away from the ship. Thus, you would need to stop the space station's rotation to do exterior maintenance. StuRat (talk) 19:30, 5 January 2009 (UTC)

I think the major reason we have not done this yet is that we have not put anything bigger than a large truck worth of manned station up into orbit. Especially to overcome problem 1 above, you need a big station. For our small stations with small, highly trained crews that only stay up for a few weeks or months, the price for artificial rotation is not worth it. If we ever get to build real habitats, rotation will likely be the means if providing simulated gravity. Von Braun's space station design was a torus with a diameter of 76m, i.e. with similar outer proportions to the ISS, but much much more livable space and a much larger crew. --Stephan Schulz (talk) 20:03, 5 January 2009 (UTC)

That's partly true, but I think the main reason is that we want to study all the negative effects of microgravity on the human body and how to combat it. Lose of muscle mass and bone strength are major issues. If the ISS was built as a rotating wheel, we lose an opportunity to figure out a cure/treatment. 67.184.14.87 (talk) 23:54, 5 January 2009 (UTC)

That sounds rather unethical: "Let's damage the health of some astronauts so we can collect data". StuRat (talk) 23:58, 5 January 2009 (UTC)

Not really. The point of space travel is learn more about the universe and our place in it. If we cannot overcome the health issues of space travel, that severely limits our ability to explore it. Besides, astronauts already know that space travel is dangerous. I'm not sure if this is still true but in at least the early days, astronauts were recruited from test pilots where risking your life with each flight is a basic part of the job. 216.239.234.196 (talk) 15:19, 6 January 2009 (UTC)

This one doesn't quite fit in with the other's: Microgravity (say 1% of normal gravity) is actually the best for getting work done, as massive objects (like satellites) can be moved easily and yet your tools don't float away. This might mean you want to spin the station slowly, instead of at the 1g speed. StuRat (talk) 20:12, 5 January 2009 (UTC)

The force doesnt dissapear when you change reference frames because the artificial gravity is due to the centripetal acceleration. This means that the spinning frame is non-inertial (as spinning frames always would be), and so the force is maintained when the transformations between reference frames occurs.

Certainly 'spin gravity' works. There is absolutely no doubt about that. The problem is that (as already noted) the station has to be large enough that you don't notice significant difference between gravity at your feet and your head - but remember that once you are spinning the thing - these outer sections of the station are going to be pulling on the central 'hub' with the full force of gravity. So instead of the station being a typical lightweight construction - it's suddenly got to be built with all of the structural strength of something like a bridge on earth. Since we've already agreed that it also has to be large - you have something that's physically huge and has to be strong - so it's chunky too. That's going to make for a pretty major launch weight. The suggestion to use fractional 'g' is a good one - but it's essentially impossible to determine what fraction of a 'g' is enough to counteract the alarming dangers of staying up there for prolonged amounts of time. We know that zero 'g' is incredibly harmful - both to health while aboard the craft - and (more worrying) to the long-term health of the astronauts once the mission is over. We know that 1g is good...but what happens if you spend a year on the moon at 1/6th g? We really don't know because short of building a moon-base or an actual spinning space station - we can't do the experiment. It might be sufficient (for example) to have a pair of small cabins (each the size of a phone booth - say) attached to opposite ends of a long cable so that they are able to spin. The astronauts take turns to eat, sleep and exercise in 1g while they do all of their daily work activities in zero 'g'. That might be enough to keep them healthy - and it would be vastly cheaper than spinning the entire station. But we don't know. As for the issue of performing maintenance on a spinning space station - you'd have to use ladders and safety lines and all of the other apparatus that you need for doing that kind of thing down here on earth. That at least is something we understand! Alternatively - you could always have a large flywheel for storing the rotational inertia while the station (or perhaps just the two phone-booths) is spun down to normal speeds. That would consume relatively little energy - so altering the amount of artificial gravity and allowing transfers from the non-spinning parts of the station. Docking could be handled the same way - turning off the spin for however many days the docking is going on - and putting spin back on again once the shuttle departs. SteveBaker (talk) 21:57, 5 January 2009 (UTC)

Not only the gravity gradient (difference between feet and head) is of concern, but also the Coriolis effect. For constant apparent gravitational acceleration, Coriolis effect is proportional to ${\frac {1}{\sqrt {r}}}$ and gravity gradient is proportional to ${\frac {1}{r}}$.

The tension in a rotating ring or the maximal tension in a rotating rod is both $\rho \cdot a\cdot r$, where $\rho$ is the density of the material, $a$ is the pseudo-gravitational acceleration (9.80665 m/s² is one standard gravity ('g')) and $r$ is the radius. This and the article on tensile strength gives you an estimate how large you can build the structure - with steel it would be a few kilometers.

If there is only 1 rotating wheel-like space habitat, then it's a problem to change the orientation due to gyroscopic effects - it's better to have 2 counter-rotating wheels on one axle. To prevent bending of the axle during re-orientation one could build opposing magnets at the rims of the wheels where the forces due to the torques are smaller than at the axle.

Icek (talk) 23:12, 5 January 2009 (UTC)

I'll just make two points relating to the fact that artificial "gravity" due to rotation of a structure diminishes as you get nearer the center. First, this could be useful. If it's found that say a level equal to say 60% or 100% Earth gravity is necessary to maintain the health of the station occupants, but 1% is better for some kinds of work area, then all that has to be done is to place those work areas near the center of the station and the living quarters farther out. This might involve an elongated station rather than a wheel-shaped one that would put most of the usable space around the rim.

And second, the original poster asked if the station might come apart at the center. While a flaw anywhere in the structure could cause its destruction, this would be more likely to happen near the rim, where the forces are greatest. But such a thing isn't a major risk: the forces are well understood, just as gravity is on Earth, and it's only a matter of properly engineering the structure to resist them reliably. It might be harder than doing it on Earth because the costs of lifting materials into space are large, but it's basically just a matter of engineering. And while ordinary structures sometimes do fail here on Earth, it's a pretty rare event. --Anonymous, 00:00 UTC, January 6, 2009.

A Zebra Finch as a pet?

Does anyone here have one? What are they like as pets? My impression from seeing them is that they don't really do much, have no interest in interacting with people and are a bit like just having a sparrow in a cage. Whenever I've seen them, they just seem to jump from perch to perch, tweet, eat, drink and back away if a person gets too close. Am I wrong? --84.67.67.100 (talk) 23:14, 5 January 2009 (UTC)

The article on Zebra finches mentions a bit about their behaviour and taming them. Mattopaedia (talk) 00:37, 6 January 2009 (UTC)

Have you only seen them? You must hear them before you ever consider them as pets. Zebra finch vocalizations can be very loud and, to some people, very, very annoying. Make sure you like what you hear first ;) --Dr Dima (talk) 01:20, 6 January 2009 (UTC)

January 6

Looking back in time through space

In terms of looking into space, does anyone know, in light years, what is the furthest back in time man has peered? Are we talking thousands or millions of years here? 79.75.238.142 (talk) 02:37, 6 January 2009 (UTC)

More like billions: [30]. StuRat (talk) 02:43, 6 January 2009 (UTC)

13,699,600,000 years ago!

It's a substantial fraction of the time since the big bang. We've observed and mapped the "cosmic background radiation" - which according to our article was just 400,000 years old at the time. We believe the universe is 13.7 billion years old - so the answer is something like 13,699,600,000 years. (OK - we should be rounding that to 13.7 billion). (That's "years" not "lightyears" - a light year is a measure of distance - not time). In some sense, it's not possible to look further back in time than that because there was nothing like atoms for photons to bounce off of - so we've pretty much seen as far back as it's possible to see. SteveBaker (talk) 05:15, 6 January 2009 (UTC)

If you consider detecting microwaves to be a method of "peering", the cosmic microwave background radiation has been travelling in space since the universe first became transparent to light 13.7 billion years ago, 400 000 years after the Big Bang. It isn't possible to detect light from any earlier time because earlier photons were continuously being emitted and scattered before travelling any appreciable distance.--Bowlhover (talk) 05:11, 6 January 2009 (UTC)

There are two potential ways to "look" even further back in time. One is the detection of the cosmic neutrino background: neutrinos decoupled from the rest earlier than the electromagnetic radiation of the cosmic microwave background. The other method would be to look for gravitational waves from the earliest epochs of the universe. Alas, we do not have the technology for detecting either of these backgrounds yet. --Wrongfilter (talk) 13:42, 6 January 2009 (UTC)

Yes, agreed. Although detecting neutronsneutrinos and gravitational waves stretches the definition of the word "see" further than I'm comfortable with! I'd prefer "infer from". I believe the CMB is the first detectable electromagnetic radiation (although you could probably argue with using the word "see" for microwaves too!). SteveBaker (talk) 15:07, 6 January 2009 (UTC)

Careful - neutrinos, not neutrons. --Tango (talk) 01:28, 8 January 2009 (UTC)

oops! all better now! good catch. Thanks. SteveBaker (talk) 16:41, 8 January 2009 (UTC)

Considering the observations of specific objects see the Hubble Ultra Deep Field. --mikeu ^talk 17:15, 7 January 2009 (UTC)

Potassium supplement dosage

I was at the health food store this weekend and looked at Potassium supplements. I was surprised that they were all 99mg and only supplied 3% of your RDA. Any one know why they are all capped at 99mg? A person would have to take 33 tablets to get the full recommended daily allowance! --71.158.216.23 (talk) 03:00, 6 January 2009 (UTC)

The reason is that an overdose of potassium can kill you, so they don't want to take any chances that the supplement, along with your normal diet, will do that. The 3% is just so they can claim their supplement has a valuable nutrient in it. Potassium is actually what they use in lethal injections (in much higher dosages, of course). See hyperkalemia. StuRat (talk) 04:53, 6 January 2009 (UTC)

That explains the reason why there would be a limit. If all the tablets are exactly 99 mg, then a likely reason for that particular size is that someone wrote the law or regulation so as to say "any tablet containing 100 mg or more of potassium requires a prescription" rather than "any tablet containing more than 100 mg of potassium requires a prescription". Perhaps at the time the next-largest size below 100 mg was 50 or 75 mg, and they assumed it would continue to be, but manufacturers saw a loophole and created 99 mg tablets in order to gain a competitive advantage and stay within the law.

In that paragraph I'm just guessing, but I do know about a similar occurrence in the field of railroads. In 1922 the Interstate Commerce Commission in the US was trying to reduce the number of train crashes due to signals being passed at danger, so they mandated the installation of measures such as automatic train stops on all railways that allowed trains to run at 80 mph or more. And the result is that to this day a large number of main US rail lines have a speed limit of 79 mph. --Anonymous, 07:56 UTC, January 6, 2009.

The Universe

Could it be possible that the universe is spherical and when one looks through a telescope in any direction they could see all the way around the universe back to ones position at earth in the future,assuming light would bend around the universe and also assuming one had a telescope that powerfull.Grimmbender (talk) 03:58, 6 January 2009 (UTC)

Sounds like you mean the universe being on a spherical surface not being a sphere itself. Consider standing on Earth: if you go forward a long distance along the surface you come back to where you are. But if you are underground and you move in a straight line (cartesian, not spherical) you wind up bursting through the surface and heading out into space. The only way "universe is a sphere" would lead to "seeing forward back to behind you" is if light somehow bounced (or tunneled, or whatever) around when it got to the edge. DMacks (talk) 04:21, 6 January 2009 (UTC)

A sphere is a surface. The solid that you're thinking of is a ball. Technically, he should have said 3-sphere. I think it should actually be 3-spherical cone, to account for space expanding through time. Anyway, I think we all know what each other mean. — DanielLC 21:06, 6 January 2009 (UTC)

It is possible that the universe wraps around itself like that (I think we'd be talking about a hypersphere or something) - we don't know for sure - but if it does, we'll never be able to do the experiment you're thinking about because the 'observable' universe appears to be smaller than the entire universe. Because the speed of light is the universal speed limit - we can only ever see or know about parts of the universe that are close enough for light to have travelled from there to here in less than the time since the big bang. Anything further away than that (including, perhaps, the back of your own head) is forever too far away to ever be visible. SteveBaker (talk) 05:05, 6 January 2009 (UTC)

"The back of one's head is inches from the eyes but too far away to be seen." DMacks sends contents of coffee mug out for tox-screen. DMacks (talk) 05:17, 6 January 2009 (UTC)

I haven't seen anything later than this and this. It looks like the Universe is a closed Poincaré dodecahedral space, it is a "small universe" with positive curvature, and yes, we can see all the way around it (same glowing spots from the CMB in different parts of the sky). This is difficult stuff, I can put the cites here or send copies of various papers and reviews to anyone interested. Franamax (talk) 07:41, 6 January 2009 (UTC)

"same glowing spots from the CMB in different parts of the sky" -- sweet Christ that's weird! --Sean 13:04, 6 January 2009 (UTC)

Wow! That is REALLY cool! But doesn't that just prove that back at 400,000 years after the big bang (which is when the CMB was 'formed') - it was all close enough to be within the observable universe - but the expansion of space (which happens faster than the speed of light at large distances) has since made everything so much larger that now we can't see it all anymore? This is tricky stuff - and the theories are changing rapidly - so it's hard to know what is considered to be "true" on any given day! SteveBaker (talk) 15:02, 6 January 2009 (UTC)

Almost no cosmologist accepts the conclusion of those papers currently. I think they blame the apparent effect on cosmic variance. Here's a slightly more recent analysis that reaches an opposite conclusion. The best bet right now is that the universe doesn't wrap around at the scale we can see, as SteveBaker said.

Practically everyone believes that the part of the CMB that we can see was all in causal contact at one time, since it's pretty hard to understand the uniform temperature otherwise. But according to current dogma that time was before the inflationary epoch, while the fluctuations in the uniform temperature arose during the inflationary epoch, at which point the different parts of the CMB sphere had lost contact with each other. Even if that's wrong, it's hard to imagine what mechanism (other than a wraparound universe) could produce correlated fluctuations of the specific kind you expect to see in a wraparound universe. (As the paper I linked explains, you can expect to see correlated circles, regardless of the details of the wraparound.) -- BenRG (talk) 17:48, 6 January 2009 (UTC)

Hmm, interesting stuff. The paper you link doesn't completely falsify Luminet, but it looks like Cornish et al bought a bigger computer and kept at it. Here they devote a paper to trashing all notion of a dodecahedron. So we still don't know the shape of the Universe and the LHC is still busted. C'mon scientists, get it together! :) Franamax (talk) 19:21, 6 January 2009 (UTC)

Four fundamental interactions as four formulas

It's my understanding that the inverse square law applies to gravitation for most intents and purposes, but with famous exceptions such as the Mercury anomaly. I'm trying to understand (1) why exactly the relativistic understanding of gravity changed the actual calculations of orbit, and (2) whether all the fundamental interactions can be expressed as simply as gravitation (either Newtonian or Einsteinian) can. I know this is a "big" question, so feel free to contribute whatever you can — don't feel pressured to answer the "whole thing"! Also, let me know exactly how I am thinking about this incorrectly, as is usually the case with me and quantum physics.$\sim$ Lenoxus " * " 05:01, 6 January 2009 (UTC)

It's not quantum physics here, but general relativity. Mercury does obey the inverse square law for gravity, but space is behaving weirdly. I think Kepler problem in general relativity will answer most of your question (if you get the maths, which I don't just now ;-). --Stephan Schulz (talk) 09:11, 6 January 2009 (UTC)

There are four known fundamental interactions: gravity, electromagnetism, strong nuclear and weak nuclear. Gravity, at least the Newtonian model of it, is pretty simple to understand. Electromagnetism isn't too bad, that's just Maxwell's Equations. It doesn't get it down to one equation but close. I haven't seen a simple expression for either of the nuclear forces. DrAstro (talk) 21:25, 6 January 2009 (UTC)

There are only three! Electroweak theory (unifying what was known as electromagnetic interaction and weak interaction) is well-established, and I think it's the one that's best understood. Gravity is hard to test experimentally because it's so weak, and the strong interaction is hard to compute because it's so strong. Icek (talk) 23:50, 6 January 2009 (UTC)

Thanks for all your responses! They've all helped a lot with my understanding of the subject. I think I'll rephrase my question as follows: Has all of physics been "in principle" narrowed down to the consequences of the fundamental forces, and if so, does that mean that everything in the universe can be understood as a consequence of three or four equations and the wave/particles they affect? (Obviously, the whole deal is a heck of a lot more complicated than that, but it's just that I figured that physicists wouldn't keep saying "just four/three forces!" if something like, say, momentum or thermodynamics was really just as fundamentally "mysterious" as gravitation.) $\sim$ Lenoxus " * " 20:56, 8 January 2009 (UTC)

All three theories are still subject to experimental tests (this is science!). And furthermore, not everything in the universe can be understood exactly because there are 3 theories and not just 1 (there are situations where all interactions are important, and the predictions are different depending on how you combine results from different theories). Attempts to get 1 theory for electroweak and strong interactions are called Grand Unification Theories (GUTs). Most attempts to get 1 theory for all three interactions are called quantum gravity as they are quantum mechanical in nature (Roger Penrose thinks that it should be non-quantum mechanical).

The equations are:

• for gravitation, the Einstein equations
• for electroweak interaction, the equations resulting from applying the Lagrangian formalism to the electroweak Lagrangian
• for strong interaction, the equations resulting from applying the Lagrangian formalism to the quantum-chromodynamical Lagrangian

The latter 2 are quantum field theories, while general relativity (the theory of gravitation) is not quantum mechanical.

Icek (talk) 00:19, 9 January 2009 (UTC)

So to re-re clarify, there are formulas for each force, but not just one per interaction. Even though I understood that the different models/formulas/understandings conflict with one another in various ways, I guess I'd always assumed that each basic interaction got its own formula that could be described in concise language, the way each of Newton's laws can — and that everything beyond that involved the "mixture" of the formulas, something complex enough it couldn't all be done a priori. To put it all another way, why does an interaction that requires multiple formulas get to be considered "one" interaction, instead of the Standard Model saying, "Here are the ten fundamental forces that together produce gravitation, and here are the four that produce electroweak", ect? Thanks again for keeping up!$\sim$ Lenoxus " * " 01:12, 9 January 2009 (UTC)

(Clarification: I know the Standard Model doesn't actually include gravity, but you know what I mean $\sim$ Lenoxus " * " 03:45, 9 January 2009 (UTC))

Maybe I can illustrate the reason using a simple example in electromagnetism - why e. g. Coulomb interaction and magnetic interaction are not considered separate interactions (I will neglect the weak interaction as well as quantum mechanics).

Consider 2 balls, each having a charge of +q. Now these balls are initially at distance x from each other and are traveling at the same velocity v (parallel to each other). The Coulomb interaction now says that they will repel each other. The magnetic interaction says they will attract each other because each moving charge is also an electric current. You can add the forces (you will always get a net repulsion, but of course smaller than the Coulomb repulsion).

Now consider the same problem in the inertial frame moving also at velocity v - the balls are initially stationary in this frame. They only repel each other by Coulomb's law. You might think this is a contradiction, as the repulsion is larger in one frame than another one, but it isn't, when viewed in the context of special relativity. Time dilation makes everything consistent (if the acceleration caused by the forces calculated for one frame is Lorentz-transformed to the other frame, the acceleration is the same as the one calculated from electromagnetism in the other frame).

My point is that a purely electrostatic phenomenon in one inertial frame has magnetic components in other inertial frames.

Icek (talk) 11:14, 9 January 2009 (UTC)

mech engineering related(new idea)

i want to do project on solar pumps,in a new way.i want that hand-pump must be operated automatically. for that my idea is that like in IC as connecting rod connects piston and crank, in this my idea is to connect piston(some long rod may be connected along its axis)and handle of hand pump by a connecting rod, so that linear motion of piston causes handle to move so taht we can get water w/o human. my question is whether we can achieve this.pls answer its urgent —Preceding unsigned comment added by 210.212.223.138 (talk) 05:55, 6 January 2009 (UTC)

See Newcomen steam engine from 1712. Substitute solar energy for coal fired boiler. Edison (talk) 15:32, 6 January 2009 (UTC)

It doesn't sound very efficient to me, as there is an unnecessary conversion from rotational motion to linear mechanical motion. Instead, I suggest a small submersible pump, which pumps water into an above-ground tank when the Sun shines, to be poured out of the tap as needed. It would need a shut-off valve that triggers when the tank is full. This allows water to be had at night as well as the day, and doesn't waste solar energy when nobody wants water but the Sun is out. If in a cold climate at winter, you would need to protect against freezing by insulating the tank and/or placing it partially underground or inside a heated building (or, a more fun option is to add grain alcohol to the tank). StuRat (talk) 21:44, 6 January 2009 (UTC)

Ice in craters of Mercury

There may be ice in craters at the North Polar region of Mercury. How many creaters with possible ice in them? What is the diameter and how deep? —Preceding unsigned comment added by Johnz Johnz (talk • contribs) 09:29, 6 January 2009 (UTC)

At first I thought this might be similar to the problem of measuring a coastline, that it's always longer if you look for smaller details. However, craters below a certain size probably can't support any ice, because the sunlight hitting the lip would warm the inside of the crater enough to melt any ice. This, of course, wouldn't apply to craters inside a larger crater, and thus in permanent shade. BTW, why not any at the South Polar region ? StuRat (talk) 21:30, 6 January 2009 (UTC)

Ice In An Unlikely Place: Mercury states that there are "about 20 circular areas" and there is a radar image/map at The Discovery of Water Ice on Mercury --mikeu ^talk 14:14, 8 January 2009 (UTC)

Atomic masses

which element is chosen as a standard for measuring the atomic masses?why? —Preceding unsigned comment added by 59.103.70.116 (talk) 09:32, 6 January 2009 (UTC)

According to atomic weight the standard is 1/12 of the mass of an atom of carbon-12. I think the isotope is chosen because it has the same number of protons and neutrons. A historical account can be found in [31]. EverGreg (talk) 10:16, 6 January 2009 (UTC)

If you look at that "historical account", it specifically says that the carbon-12 scale was suggested because "because of carbon's use as a secondary standard in mass spectrometry" and because it gave numerical values close to the old scale used by chemists (which was based on a natural mixture of oxygen isotopes). Also, I remember reading in one of Isaac Asimov's monthly science essays that carbon-12 was adopted because it was particularly easy to measure and for the same reason regarding the numerical values. This is likely an interpretation of the same facts: if it was used as a "secondary standard" that was probably because it was easy to measure. --Anonymous, 19:34 UTC, January 6, 2009.

And don't copy the above word-for-word, everyone will know :) hydnjo talk 04:44, 7 January 2009 (UTC)

chemicals for surgical gloves

i am small scale manufacterer of surgical gloves. i want to improve my product. so, i want a chemical composition for (natural latex)surgical gloves. Thanking you.Arijitkm (talk) 10:08, 6 January 2009 (UTC)

Natural latex is a polymer of isoprene. Graeme Bartlett (talk) 10:58, 6 January 2009 (UTC)

Makes me wonder where my hospital gets its surgical gloves :( hydnjo talk 04:41, 7 January 2009 (UTC)

Definition of "Life"

How do we define "Life"? I have already looked up in a number of books. One said "Life is a set of characteristics which distinguish living organisms from non-living objects" but I want a definition without relativity with non-living things. Please note this is not a homework. Many thanks. —Preceding unsigned comment added by 59.103.70.227 (talk) 12:31, 6 January 2009 (UTC)

There is no hard, fast, agreed-upon definition for life. As our article notes, "to define life in unequivocal terms is still a challenge for scientists, and when derived from an analysis of known organisms, life is usually defined at the cellular level." Further, we note that life exhibits all or most of a given (and itself flexible) set of criteria. Our article contains many further attempts to phrase a concise definition. — Lomn 14:04, 6 January 2009 (UTC)

Well, "life is the process that organisms go through during their lifetime", perhaps? I'm not sure it's reasonable to demand a definition that doesn't relate to non-living things, though, simply because I'd say a big part of the definition is precisely that it's not a part of the non-living things. Not that you can't define it otherwise, but it might not be a very good or informative definition. -- Captain Disdain (talk) 14:06, 6 January 2009 (UTC)

See Life. It has a section on "definitions." -Arch dude (talk) 14:37, 6 January 2009 (UTC)

One annoying problem for definers is that with the advent of computers, it's pretty easy to take any reasonable definition that they come up with and write a computer program that fulfills that set of criteria. Since biologists are pretty snobbish about such things and don't want computer software classified as "alive", we can pretty much mess with their heads by doing this. Sadly, "life" like so many other words is just a label we humans use to attach to things and nature does what nature wants regardless of our petty classifications. Consider, for example, efforts to define the word "Planet" - astronomers wanted desperately to keep Pluto as a planet but to exclude all of those interesting new bodies we kept finding further and further out (eg Sedna) - it proved impossible to come up with a reasonable definition for the word that would exclude things they didn't like and include things they did. So we end up with a tortured definition that excludes Pluto and upsets a huge number of people. It's kinda silly because it's just a word - it doesn't prove anything. It's the same with the word "Life" - whether it includes viruses - whether it excludes computer software that reproduces, evolves, etc - whether synthetic life forms made of lipid bubbles with weird chemicals instide count or not...these are just issues with the human obsession with naming things and trying to categorize them with black and white terms. In the end, some things reproduce some don't - some eat and defecate - some don't, some respond to external stimuli - some don't. Our biology teacher in high school was an old lady who never married and had no children - when she taught us the (then) standard definition with the mnemonic "RINGPERM" (REPRODUCTION, INGESTION...argh...yadda, yadda...I forget...MOTION!) - some idiot from the back of the class yelled "You've never reproduced - so you must be dead" - which actually reduced the poor lady to tears. So let's not obsess about the word - but instead use it loosely as the need fits and resort to formal definitions of capabilities when it actually matters. SteveBaker (talk) 14:53, 6 January 2009 (UTC)

I've heard there are two kinds of people: These who divide things into distinct categories, and those who don't. What would be the criteria for determining whether a potato is "dead" or "alive" when it is on a shelf in my kitchen? It arrives full of vitality, and eventually sprouts. If planted, it would produce roots and leaves and more potatoes. Seems to be alive. But if I remove the "eyes" when it arrives, surely that does not mean it is suddenly dead, any more than a steer is dead. If I boil it long enough, that would seem to make it dead. If it rots, that would also seem to make it dead, although full of bacteria. Edison (talk) 15:22, 6 January 2009 (UTC)

Indeed - "There are 10 kinds of people in the world - those who understand binary numbers and those that don't.".

The example you give exhibits the same problem as the guy at the back of my high school biology class - we aren't defining whether some particular instance of a thing is "alive" at this precise instant - we're asking whether an entire class of things can be considered to be "life". Reproduction does indeed seem to be an important feature of life (rocks don't make copies of themselves - bacteria do - but viruses can only do so with help from something that is in itself able to reproduce) - but an individual creature may be considered to be alive even if it has not nor ever will reproduce. Indeed, creatures who are born with some congenital defect that prevents them from reproducing are not pronounced "dead". That's because we're talking about a general property of all such creatures - not of one individual. So the definition of "life" doesn't really encompass the issues of whether your potato is alive or not right now. That is the subject of an entirely different fuzzy term: "death" - which doctors and medical ethicists struggle with all the time...which is a similar debate - but over an entirely different word. Coming back to the "10 kinds of people" joke - the problem is that when you try to treat words like "planet", "life" and "death" as binary states, you get into a lot of trouble - and the two kinds of people you were talking about overlap fairly strongly with the 10 types I'm talking about! SteveBaker (talk) 16:03, 6 January 2009 (UTC)

The Stewart Test is probably the best you can do outside of a given context. --Sean 16:13, 6 January 2009 (UTC)

I remember reading a Lyall Watson book on the subject of "what happens after death", which was similarly ambiguous about the definition of "death". --TammyMoet (talk) 19:15, 6 January 2009 (UTC)

Entropy and life#What is life?. Schrödinger and Lehninger both state that life can be said to be anything which feeds off of negentropy. I think Gibbs free energy also has something to do with it. --Mark PEA (talk) 20:44, 6 January 2009 (UTC)

The trouble with negative entropy is that all sorts of things that are very clearly not 'alive' (refrigerators, for example) exhibit that. It's very easy to show it by (for example) programming a robot to sort a pile of randomly colored lego bricks into piles of red, blue, green and yellow. The entropy of the blocks after sorting is less than when they were randomized beforehand - so the robot is producing negative entropy...do we want to call a really simple 'bot qualify as 'alive'? I don't think so. SteveBaker (talk) 05:11, 7 January 2009 (UTC)

I've seen arguments, based on some definitions of life, that black holes are actually alive. They slowly move towards food sources. They maintain a high gravity within themselves which is the only thing keeping them from exploding. And there were a bunch of other arguments to attempt to satisfy the various established conditions of life. Anythingapplied (talk) 21:52, 6 January 2009 (UTC)

Again - if you make a bad enough definition - you'll either let in a lot of silly things like refrigerators and black holes - and you'll exclude a bunch of things like celibate biology teachers. I do think that (the capability of) reproduction is one of the touch-stones of life - so refrigerators and blackholes should certainly be excluded for that reason alone. I can't think of anything that I'd call "alive" that doesn't have the capability to reproduce (even if only at the cellular level). You need other caveats to avoid things like fires from being declared 'alive' (a fire creates more fire - it consumes food and produces waste - it moves away from places where there is no food and into places where there IS food - it is born and eventually dies - it breathes oxygen and expels CO2 - it consumes animals and plant material for nutrition). To exclude fire - you have to require inheritance - that some attribute of the parent is handed on to the offspring. But a definition that excludes 'artificial life' computer software (like Conway's Game of Life for example) is exceptionally tricky.

A LOT of the definitions to "Life" come down like Oliver Wendell Holmes, Jr.'s definition of obscenity, to paraphrase, "I may not be able to define it, but I know it when I see it". The problem is that any basic definition of life either excludes things which should probably be considered alive (like viruses and prions.) or includes things which should probably not be considered alive (like computers and fire and black holes and all sorts of weird things). --Jayron32.talk.contribs 13:23, 7 January 2009 (UTC)

Whistle in water

When dip into water I hear (as everybody, hopefully) a sort continuous whistle, or hiss. I wonder what it is, and where it's coming from. Is it just my eardrums under the effect of the pressure, or is it a kind of ground noise that propagates particularly well into the water? --PMajer (talk) 13:27, 6 January 2009 (UTC)

You are hearing the underworld. Try to talk into the water... Do you hear replies? —Preceding unsigned comment added by 94.27.209.85 (talk) 13:52, 6 January 2009 (UTC)

no but I can read it --PMajer (talk) 14:44, 6 January 2009 (UTC)

I think it's like when you hold a seashell to your ear (actually, pretty much any concave object - a teacup for example - will do) and "hear the sounds of the ocean". What you're hearing is the blood flowing through your head that's being reflected back into your ear because of the unusual acoustics. SteveBaker (talk) 14:38, 6 January 2009 (UTC)

If blood makes a faint noise as it circulates, a microphone should pick it up and it could be amplified and heard. Furthermore, the microphone could be placed on any part of the body. I have never read that to be the case except for an audio stethoscope placed over the heart. Just what does a stethoscope pick up anyway? Blood rushing through heart valves? And what is a heart murmur? And just what is heard when a sea shell is held near the ear - is it resonance to ambient noise? No, a sea shell is too small to resonate to audible sound. Also, if two persons place their ears together, they will not hear anything, so why does a sea shell pick up sound emanating from the ear, and reflect it back? –- GlowWorm —Preceding unsigned comment added by 174.130.253.174 (talk) 23:43, 6 January 2009 (UTC)

There are lots of conflicting explanations around - and many pooh-pooh the old blood-flow explanation. However, putting a seashell over a microphone doesn't produce any sound at all - so THAT explanation is bogus. I wouldn't expect a microphone held over your body to produce a sound - the concavity of the seashell is acting like a 'retroreflector' - sending all of the blood supply sounds precisely back into your ear...that has the effect of amplifying that very subtle sound to the point where you can hear it. You can actually use your hand in place of the seashell - and that lets you adjust the shape. A flat palm doesn't produce anywhere near as much white noise as a cupped palm. The 'resonance' theory fails miserably here because that soft bag of water that is your hand can't possibly resonate in the same way as a seashell or a teacup - so how come it sounds the same? My 'focussing' explanation also explains why two people's ears put close together don't do it - the ear is carefully evolved to absorb the energy from feint sounds and translate them into nerve impulses - so it's not gonna reflect ANYTHING. Sure - this isn't a 100% accepted explanation - but it does fit the facts better than the others. SteveBaker (talk) 04:52, 7 January 2009 (UTC)

@GlowWorm: Your questions about what the stethoscope picks up, are answered in the articles Heart sounds and Heart murmur. --NorwegianBlue ^talk 15:29, 7 January 2009 (UTC)

Charges on a sphere

Imagine positive charges confined to the surface of a sphere. If there are two positive charges then they will move apart until they are "poles apart".

But I have difficulties imagining three positive charges. If the location of one of the charges, is defined as position A, where will the other two charges be located relative to position A? 122.107.203.230 (talk) 13:40, 6 January 2009 (UTC)

While I'm not certain that charges would behave in this fashion, three equidistant and maximally distant points on a sphere are on a plane that bisects the sphere, 120° apart from each other. — Lomn 14:01, 6 January 2009 (UTC)

...and 4 would be located on the points of a regular tetraeder that is circumscribed by the sphere. Both solutions are non-unique unless you fix at least two of the points. --Stephan Schulz (talk) 14:10, 6 January 2009 (UTC)

• For greater clarity, in English that's a tetrahedron. --Anon, 19:36 UTC, January 6, 2009.

Thanks! --Stephan Schulz (talk) 22:32, 6 January 2009 (UTC)

I would expect a charged conductive sphere to have evenly distributed charges, in the absence of an external field. The "charges" would not generally isolate themselves to a small number of distinct locations. Do you consider each of your "positive charges" to be one atom which has given up an electron? What is the experiment, or thought experiment, exactly?Edison (talk) 15:15, 6 January 2009 (UTC)

The total energy of 3 unit point charges constrained on the unit sphere, $\scriptstyle {\frac {1}{2}}\sum _{i\neq j}|x_{i}-x_{j}|^{-1}$, is certainly minimized exactly when the charges are in the positions described by Lomn (equilateral triangle on a maximal circle). This is easy to see by direct comparison (one first proves that they have to stay on a maximal circle, then that they have to be equidistant). The general geometrical problem of the minimal energy position of n unit charges on the unit sphere is called Thomson problem (yes, we have it!!); here there are some nice pictures [32]. Note that the problem is not even obvious in the unit disk version; in particular for $\scriptstyle n\geq 12$ the configuration of minimal energy is not on the boundary of the disk, a 1985 result by A.A.Berezin [33]. --PMajer (talk) 16:17, 6 January 2009 (UTC)

Well, for 2, 3, and 4, it is easy, because they correspond to the 1-, 2-, and 3-simplices, respectively, because they all fit in 3 or less dimensions. However, I wonder if there is an easy systematic way to compute the optimal solution for higher numbers; say, if you had 17 charges. I wonder if the solution is even unique (up to rotations and reflections of course) in that case. --Spoon! (talk) 05:35, 7 January 2009 (UTC)

well, no... 4 is not that immediate, still it's true that it is the regular tetrahedron. In the reference above you can find a list of the numerical solutions up to n=400 and also interesting links --84.221.209.108 (talk) 09:44, 7 January 2009 (UTC)

By the way, I see in the wikipedia article that the solution for n=24 is still unique up to rotation and reflections, but not up to just rotations (it is not congruent by rotations to its mirror reflection, like a hand). It is given by the vertices of the snub cube, a chiral polyedron--PMajer (talk) 16:16, 7 January 2009 (UTC).

Breathing in cold weather

When I want to go to sleep, I unconsciously breathing using my mouth. Is it normal? When I remember I try to breath using my nose, but in a while it's just getting back using mouth. Is it a phenomenon in cold temperature or is it just me? Second question, when breathing in cold weather, the air we breath in should be converted to our body temperature, right? How cold it is that human will feel uncomfortable breathing in cold temperature? What about people who is standing in an -20 degree Celcius environment, is the air temperature would change from -20 to 37 degree just within a few seconds? Thanks for the response. roscoe_x (talk) 15:55, 6 January 2009 (UTC)

See, believe it or not, "Mouth breathing". The nose warms air before it gets to the lungs more efficiently than the mouth does, so I would expect nose-breathing to be a better cold-weather strategy. As for the temperature that would cause discomfort in breathing, I suppose that that depends on the person. The coldest I've been out in is minus 5 Farenheit, about...let's see, 32 is zero, 1.8 per degree, 5 below is 32 + 5, 37 divided by 1.8 is times 5/9, roughly 20 below, Centigrade, I mean Celsius. I don't remember having trouble breathing, but that's me. --Milkbreath (talk) 20:54, 6 January 2009 (UTC)

I sometimes feel a burning in my lungs when breathing extremely dry, cold air. It starts somewhere around 14°F, or -10°C, but, as I said, the humidity may also play a part. When it gets colder than that, I try to breathe through a scarf, as that gives the air more time to warm up. For someone at the South Pole at it's coldest, I'd expect they'd want to use a tube to breathe through, wrapped several times around their torso, so it warms up a lot before hitting their lungs. StuRat (talk) 21:22, 6 January 2009 (UTC)

I've never heard of someone using a tube for breathing like that in Antarctica, but then again, I'm sure that people improvise a lot down there. It kinda makes sense to me, but also potentially very, very inconvenient, not least so because when the cold gets really extreme, most flexible things -- like long plastic tubes -- tend to become rigid and brittle. Do they really do that? Man, it's a fascinating place.

Anyway, as for breathing in cold temperatures, I've been at and around -30 degrees Celsius, which isn't a lot of fun, but I don't recall having much trouble breathing, at least when compared to how my nose and cheeks felt at the time. That said, if you run around or do something else that makes you breathe heavily, you'll definitely feel it in your lungs. It's certainly not very gentle weather, especially if it's windy (though make no mistake, it's almost balmy compared to the South Pole during the cold season). -- Captain Disdain (talk) 23:21, 6 January 2009 (UTC)

I've been out in -40C (also -40F) a few times and didn't have much trouble breathing. However, I noticed a strange sensation in my nose that I think was the water vapor in my breath freezing on the hairs in my nose. After about 5-10 minutes my sinuses started to hurt and they cooled down. After that if I took a deep breath my throat hurt, but I never noticed any problem with my lungs. Of course they are in your chest and should be at core body temp, which should stay high unless you're getting ready to freeze to death.Tobyc75 (talk) 03:39, 8 January 2009 (UTC)

NEUROLOGY/RADIOLOGY

This question has been removed. Per the reference desk guidelines, the reference desk is not an appropriate place to request medical, legal or other professional advice, including any kind of medical diagnosis, prognosis, or treatment recommendations. For such advice, please see a qualified professional. If you don't believe this is such a request, please explain what you meant to ask, either here or on the Reference Desk's talk page.

This question has been removed. Per the reference desk guidelines, the reference desk is not an appropriate place to request medical, legal or other professional advice, including any kind of medical diagnosis or prognosis, or treatment recommendations. For such advice, please see a qualified professional. If you don't believe this is such a request, please explain what you meant to ask, either here or on the Reference Desk's talk page. --~~~~

Gaining immunity to the common cold?

Hopefully, this question isn't considered medical advice. Per the Wikipedia article, "Common colds are most often caused by infection by one of the more than 100 serotypes of rhinovirus, a type of picornavirus. Other viruses causing colds are coronavirus, human parainfluenza viruses, human respiratory syncytial virus, adenoviruses, enteroviruses, or metapneumovirus. Due to the many different types of viruses, it is not possible to gain complete immunity to the common cold."

I have 3 questions:

1) Does that mean that each time someone catches the common cold, he or she builds an immunity to that particular virus? (I'm pretty sure the answer is yes, but I want to confirm.)

2) As a person gets older (ignoring the effects of aging) is he/she less likely to get a cold since he/she may have immunities to dozens of cold viruses?

3) Does the immune system 'forget' how to fight a virus if it's been a long time since it encountered a virus? For example, I were 100 years old, would my immune system remember how to kill that cold virus I had when I was 20?

216.239.234.196 (talk) 16:32, 6 January 2009 (UTC)

The problem with immunity to viral diseases is that viruses mutate so quickly. You catch this year's strain of cold - now you're immune so you probably don't get another cold this year - but as the virus makes its way around the world and comes back the following season - it's mutated to the point where your immunity stops working and you catch it all over again. That's why (for example) influenza shots have to be given each year - and the manufacturers have to guess which mutant of the 'flu virus will strike this time around.

SteveBaker (talk) 17:58, 6 January 2009 (UTC)

1) Yes.

2) Not really, as the strains to which they have developed an immunity no longer exist, having died out after a significant portion of the population became immune to them. Entirely new strains replace them.

3) Yes, loss of immunity does occur over time. First there is a period of partial immunity, then eventually none at all. StuRat (talk) 21:11, 6 January 2009 (UTC)

2) Yes to some extent. The Spanish flu is supposed to have affected younger people disproportionately because of this. Dmcq (talk) 08:35, 7 January 2009 (UTC) Sorry I see the latest theory is that people who had a good immune system died because of a cytokine storm and the old with weaker immune systems livd through that. Dmcq (talk) 08:52, 7 January 2009 (UTC)

Fighter plane firing a bullet

What is the effect on the speed of a fighter plane chasing another when it opens fire? What happens to the speed of pursued plane when it returns the fire? Please explain. Also note, it's not a homework. Many thanks. —Preceding unsigned comment added by 59.103.69.24 (talk) 20:33, 6 January 2009 (UTC)

I think recoil is a good place to start. Also see Newton's laws of motion- in particular, the third law. Friday (talk) 20:36, 6 January 2009 (UTC)

And yes, there are extreme instances of this. The A-10 Warthog's main gun has a recoil on par with the thrust of one of its two engines (see the GAU-8 article). — Lomn 21:36, 6 January 2009 (UTC)

Shape of Planets

What is the reason for all the planet has spherical shaped? 91.140.217.144 (talk) 21:42, 6 January 2009 (UTC)

Because they're massive enough that their gravity is strong enough to pull them into a hydrostatic equilibrium. In fact this property is now part of the definition of a planet. Algebraist 21:45, 6 January 2009 (UTC)

Note that they aren't perfect spheres, however. They are all somewhat elliptical due to centripetal force, and can have some "lumps" as well. StuRat (talk) 01:04, 7 January 2009 (UTC)

Oblate spheroid is the actual term for their shape, in case you were wondering.-RunningOnBrains 01:15, 7 January 2009 (UTC)

A simple way to think about this is that gravity is pulling everything as close together as they can get. Any bits of the planet that were a lot further away from the center than the rest would tend to move to be closer to the center...this results in everything ending up at the same distance - and the geometric shape that has everything at the same distance is a sphere.

Think of it another way - if the planet was (say) a cube - then there would be eight amazingly tall mountains (one at each corner) - these would be so massive that they would tend to slump and collapse under their own weight - so gradually, the planet would turn back into a sphere again.

The reason planets are slightly 'oblate' (squashed at the poles and fatter around the equator) is because they are spinning and at the equator (where they are spinning faster) the centrifugal force slightly opposes gravity - that "weaker" gravity results in that bulge.

Only 'lumps' that are small enough and strong enough to stay put under their own weight can withstand that tendancy to becoming spherical - hence mountains here on earth don't get bigger than Mt.Everest. On lower gravity worlds (Mars, for example) there are bigger mountains - "Olympus Mons" is truly, stunningly gigantic!

SteveBaker (talk) 04:33, 7 January 2009 (UTC)

See geoid and equipotential surface. If a planet's surface were covered by liquid then (in the absence of tides) the liquid would assume a shape such that the local apparent gravity vector (true gravity vector - centripetal force vector) was everywhere perpendicular to its surface - this shape is a geoid. Rock, unlike liquid, is able to resist tangential forces, so it can form mountains and valleys that deviate above and below the geoid surface. Gandalf61 (talk) 11:32, 7 January 2009 (UTC)

Deliriants vs. Hallucinogens

Hi, just a quick question. What is the difference between a hallucinogen and a deliriant? I have heard the 2 terms and don't know the difference.Cssiitcic (talk) 23:08, 6 January 2009 (UTC)

Delirium says: "While the common non-medical view of a delirious patient is one who is hallucinating, most people who are medically delirious do not have either hallucinations or delusions". --Sean 00:10, 7 January 2009 (UTC)

Hallucination is the sensing of objects which are not in the real world. There are halucinations of every sense (visual, auditory, tactile, etc.) but the common thread is that our brains tell us something is there which is not. Thus, a hallucinogen causes that reaction in the brain. One can be perfectly lucid and still be having a hallucination. Delirium is a loss of lucidity, that is one becomes less than perfectly responsive to the outside world. Its not that you see stuff thats not there, its that your brain does not react "appropriately" to stuff that IS there, so you don't recognize the real world for what it is. It is also entirely possible to be delirious without hallucinating; and there are of course situations where both are occuring... --Jayron32.talk.contribs 13:11, 7 January 2009 (UTC)

To confuse matters Delirium tremens does cause hallucination as one of its symptoms. 76.97.245.5 (talk) 16:21, 7 January 2009 (UTC)

I think the general view is that hallucinogens produce hallucinations which the person is aware are hallucinations. Where as deliriants produce more vivid hallucinations (like those in dreams) which the person is not aware are hallucinations. --82.21.25.219 (talk) 17:51, 7 January 2009 (UTC)

The above was me by the way. I don't like to recommend anecdotal evidence, but trip reports are one of the only sources of evidence for this kind of thing (due to obvious legal and ethical reasons). If you are further interested in this kind of thing, on Erowid compare the trips of say magic mushrooms ([34]) with belladonna ([35]). My judgement is that being on a typical anticholinergic delirant is like dreaming whilst being awake, which could cause some large issues such as walking into roads or cutting your self completely unknowingly. --Mark PEA (talk) 18:10, 7 January 2009 (UTC)

January 7

This

How is Avobenzone formed? What is the science behind Methylchloroisothiazolinone? What is it's occurrence in nature?96.53.149.117 (talk) 00:53, 7 January 2009 (UTC)

Methylchloroisothiazolinone (also commercially known as Kathon CG when mixed with methylisothiazolinone) is a synthetic preservative. Thus it is made by humans via a series of chemical reactions and is not known to be generated in a naturally occurring process (at least not at significant levels). I'm not sure what you mean by the science behind it, but it is a known human allergen that can cause contact dermatitis, and has been shown to be mutagenic and cytotoxic in some studies. Rockpocket 08:43, 7 January 2009 (UTC)

Transistor configuration in a radio Tx/Rx

Picture:[36] I've been looking up simple radio transmitters/receivers on the net.

1. In many sites, as in the above picture there is capacitor connecting the collector and emitter of the transistor which is connected to the antenna. What is that for?
2. Also in the above picture of a receiver and many others, the input from the antenna seems to be given to the collector. As far a I know, in all three configurations of the transistor, base and emitter are used for input. what is this connection?

59.93.4.189 (talk) 09:36, 7 January 2009 (UTC)

For #1, maybe impedence-matching (see Antenna tuner)? Or wait, do you mean the "10" or the "50"? DMacks (talk) 18:31, 7 January 2009 (UTC)

Interesting circuit. It maybe looks like a self oscillating mixer at first sight. Perhaps the input signal is large. Since the detected output seems to operate a relay, perhaps this is a remote control Rx?--GreenSpigot (talk) 04:33, 8 January 2009 (UTC)

The first transistor is in sort of common base config. There may be coupling between the emitter coil and the collector coil which would make an oscillator. The input signal is fed to the collector and to a parallel tuned circuit in the collector and so would not see much loading at the res frequency of the collector tank.--GreenSpigot (talk) 04:39, 8 January 2009 (UTC)

Unless of course, the input signal is intended to make the input circuit oscillate (at its res freq) and thereby generate a signal that can be rectified later in the circuit to operate the relay!--GreenSpigot (talk) 04:42, 8 January 2009 (UTC)

The frequency f0 on the diagram is 27.145 MHz, which is RC Yellow Band. That first stage is an oscillator, no doubt, and it looks like it must drive that antenna; you can't take input on the collector like that. What it's using for input, I can't tell, and the mess leading to the relay is a mystery, too. That second transistor might be biased to chop the waveform into class-c, and the final has a little power supply in the bias, fed by the output signal, that looks like AGC. What the relay controls is anybody's guess. The 50p across the transistor is there because the circuit didn't work right unless it was there, basically; it shunts higher frequencies around the transistor so they're not amplified. --Milkbreath (talk) 15:39, 8 January 2009 (UTC)

It seems pretty obvious that the signal flow in the diagram is from left to right. In that case the oscillator is acting as a receiver (albeit a strange one). Otherwise there is no control of the oscillator and the rest of the circuit is junk. But I believe the rest of the circuit amplifies and detects the oscillator output to drive the relay.--GreenSpigot (talk) 16:52, 8 January 2009 (UTC)

1. It has to work because, not just in this site, but in many other sites there is similar diagram with the input from the antenna given to the collector with a capacitor connecting collector and emitter. I'm using Qucs and/or gnu spice right now to see what happens when the 50p is changed...
2. It is OK to rpleace the antenna with a signal source with 50 Ohm resistance in series, right?
3. Another funny thing is that if the o/p of the first stage is taken from above the 10uH i.e @ at the other end of 50p, the waveform there is stronger(!) than if o/p is taken from above the tank circuit. Since you said the first stage looks like an oscillator I'm going to take a look at regenerative receivers.
4. Another thing is that the 40n is a large value as far as 27MHz is concerned (.147 Ohm reactance). So even on the presence of the 5.6k Ohm resistor, the place that they take o/p of first stage is practically @ Vcc or ac-ground. Any way I'm probably going to try anther circuit. 59.93.21.70 (talk) 10:59, 9 January 2009 (UTC)

Quantum Physics - The double Split Experiment

The concusion for the double split experiment was that particles behave differently when 'being observed' - ie it was mysteriously just the ACT of us OBSERVING that changes particle behaviour. Is it not possible that it was the observing APPARATUS ITSELF that was interfering with the particle behaviour & therefore the experiment ? How exactly did they detect the respective particles (photons/electrons)- what type of apparatus did they use? No one ever questions this? —Preceding unsigned comment added by 165.145.151.160 (talk) 10:09, 7 January 2009 (UTC)

"The" double slit experiment isn't one experiment like the michelson-morley experiment, it's an experiment that can be performed in the classroom and has been repeated with several different variations. The idea that it's the observation that causes the wavefunction to collapse is the Copenhagen interpretation of quantum mechanics, which is still being debated. So yes people question this, but it's more a debate about interpretations of quantum mechanics than a debate on what apparatus to use. EverGreg (talk) 10:29, 7 January 2009 (UTC)

What that is referring to is simply that in order to measure anything of any order of magnitude or size, you must modify it. For example, if you wish to measure the piece of wood you are using to build a tree house, you must manipulate that piece of wood with your hands, use a tape measure of sorts, and determine a length. Not that the action really changes the size or shape of a piece of wood. But when you are dealing with attempting to observe something as small as a electron or photon etc, there's nothing small enough to really measure directly. So, when studying electrons, scientist bounce other electrons off of the object or subject and observe the trajectories after impact and deduce from the deflections the properties of the object/subject. If you wanted to observe a red wavelength photon, and bombard it with electrons or white wavelength photons (light), you are going to add energy to your subject and thus, change its color or in some cases, composition and structure completely. There are new encryptions for computer lines using this quantum mechanic. They are already calling it Quantum cryptography. Hope that helps a bit.... Operator873 (talk) 10:25, 7 January 2009 (UTC)

Thanks Operator873 - but surely knowing that alone - that there is no way to observe the electrons without disturbing them and their path, it brings renders the results of the experiment inconclusive? All I'm hearing is this massive hype about how this experiment has opened a whole new door into science in that things arent really there until we observe them - and all of this is based on an experiment which has 'fake' results? —Preceding unsigned comment added by Nickylaatz (talk • contribs) 11:12, 7 January 2009 (UTC)

One question is if the Heisenberg principle is caused by a real uncertainty of the underlying system, or is caused only by the fact that to measure a system, we necessarily need to disturb it. The surprising thing with the double slit experiment is that over time a double slit inference pattern forms even if we can guarantee that only a single photon (or electron for that variant of the experiment) is in the experimental apparatus at any one time. If we consider a photon as a discrete particle, each of these photons flies through exactly one of the slits and has no way to interact with the other slit, or other photons. Still, in sum the photons behave just as interfering waves would. This strongly suggests that photons (and electrons, and other particles) "really" have wave-like properties, and hence do not have one discrete position, but are spread out in space. --Stephan Schulz (talk) 11:59, 7 January 2009 (UTC)

Except that if we place a detector of some sort to determine WHICH slit the electron passes through... If we make any attempt to identify the specific slit, then we end up with two discreet bands immediately behind the slits, whether we fire one electron at a time or many. Again, the addition of the measuring device appears to change the nature of the light from wave-like behavior to particle-like behavior. Or, light is doing the same thing in both cases, and its our measuring device which changes the experiment... --Jayron32.talk.contribs 13:05, 7 January 2009 (UTC)

First off, we're talking about the observer effect. The Heisenberg uncertainty principle has nothing to do with it. Second, it's not so much that light has wave-like properties as theoretical waves have light-like properties. Also, theoretical particles have light-like properties. Third, Jayron, the measuring device doesn't change the nature of the light (or electrons or whatever you use). It just causes the waveform to collapse and expand from there, and behaves like it would if there was a single slit, which makes sense, as it's only going through a single slit. — DanielLC 16:26, 7 January 2009 (UTC)

There are at least three things being discussed in a big tangled mess here. Firstly - indeed it is impossible to measure the position and speed of an electron without disturbing it in some way. Secondly - even without that - the precise position and speed is unknowable because an electron is a fuzzy probability cloud not a solid 'dot'. Thirdly, the duality of particles and waves do indeed seem to act such as to make things like the double-slit experiment do different things depending on how you measure them. The first of these is (I think) easy to understand. You can't measure something without affecting it in some way - duh. If it's small enough then the way you affect it makes a HUGE difference - but for large objects, it doesn't. The second of these is definitely a bit strange - but it's clear that "this is how the universe works" - and just because it seems weird to beings like us that learned and evolved in a 'macro-scale' world doesn't make it any the less valid. The really REALLY disturbing one is the double-slit experiment where the outcome depends qualitatively on how you look at it. Fire one photon at a pair of slits - it interferes with itself just like a wave that's travelled through both slits and you get a diffraction pattern. Put a photon counter in the way to figure out which slit the photon went through and you get an answer as to which one it passed through - but as if by magic, the diffraction pattern goes away and the particle seems to say to itself "OK - if you want me to behave like a particle - so be it - so you don't get a diffraction pattern anymore."...but how did the part of the light that went through the other slit in the first experiment "know" that you had a detector on the other slit - which could be some distance away? That's weird...it IS a whole new thing for us to understand.

I've personally done the double-slit experiment (we did it in 1st year college physics) - and I have to tell you that it's completely compelling. It's not just some flakey result - or something that's open to interpretation - it works and it's a really simple experiment. At small scales, the universe is a very weird place - but that's because we're not equipped to think in terms of the way it works at those scales - not because it's wrong. The problem is with our brains - our "common sense" - which turns out to be a mere approximation of the way things are that's only valid at large scales. It's like an astronomer saying that bacteria don't exist because he can't see them with his telescope. Our minds are simply unable to do this...but the universe doesn't care about that - it works however it works. SteveBaker (talk) 18:02, 7 January 2009 (UTC)

SteveBaker (talk) 18:02, 7 January 2009 (UTC)

Steve, I've observed two copies of your signature, so you must have sent it through two slits. There's no interference pattern, however, so there must have been a detector used. :-) StuRat (talk) 19:04, 7 January 2009 (UTC)

No, not quite. For such a small number of Steves, you get a probabilistic result. He may constructively interfere with himself here. --Stephan Schulz (talk) 21:15, 7 January 2009 (UTC)

Probably Steve has built his own home setup to search for gravitational waves. Franamax (talk) 23:08, 7 January 2009 (UTC)

Steve, you did the quantum mechanical double slit experiment in a first-year physics lab? With individual particles, and a detector at one of the slits? And it was "a really simple experiment"? In 1970 or 1980 or whenever you went to college? I find that hard to believe. Plenty of physics labs include a "double-slit experiment" that consists of observing a diffraction pattern from a laser, but that's explainable with Maxwell's equations. -- BenRG (talk) 04:56, 8 January 2009 (UTC)

Just playing devil's advocate here, my professor demonstrated the double-slit experiment to us my freshman year in lab, and I performed it in my sophomore year. It really is simple, though the equipment involved (ultra-dim lightbulb, with a photodiode capable of detecting single photons) was a bit complex by itself. I was able to perform it, with multiple distances, comparing one- and two-slit results, in just 3 hours.-RunningOnBrains 05:33, 8 January 2009 (UTC)

Yep - it's been a long time - but I believe we used a sodium lamp as the light source (it produces nearly monochromatic light - not quite as good as a laser - but enough to show the effect) - the photon counter was some kind of electronic gizmo - a photo diode is a possibility. But the photoelectric effect (which is what you use to count photons with) was demonstrated in the 1850's - so it was certainly around in 1975. I kinda recall a techtronic's storage scope might have been the way we recorded photons arriving at the detector...but honestly, it's been too long for me to recall the details. We had pretty good science labs in British universities back then - they took this kind of undergrad stuff rather seriously compared to modern colleges who find it cheaper to teach it out of a text book. SteveBaker (talk) 16:39, 8 January 2009 (UTC)

It seems pretty obvious to me that the problem is your 'photon counter'. How does this photon counter work, exactly? This rather crucial aspect of the double slit experiment always seems to be glossed over. People say, "but if you watch to see which one the photon goes through, the interference pattern vanishes! Amazing!" and glide right over the part where you have to explain just exactly how you "watch" a photon. Like many ideas in quantum mechanics, this seems to be an impressive conclusion drawn from some very dodgy reasoning. Maelin (Talk | Contribs) 05:20, 8 January 2009 (UTC)

The photon counter works because of the photoelectric effect - which is important because that's the effect that led Einstein to show that light acts like particles. Einstein won a Nobel prize for that work. It's effectively a solar-cell - a photo-diode - which produces electrons when struck by a photon. If you can find a decent translation of Einstein's paper on the photoelectric effect - you'll find it pretty compelling as an explanation of why light "is composed of particles"...that guy was actually rather smart! SteveBaker (talk) 16:39, 8 January 2009 (UTC)

Aaaaaaaah - Maelin - this is PRECISLY what I'm on about!!!!! Maybe if we watched it in a different way, with different non-intrusive apparatus/method, it would NOT collapse after all. It might be OUR EQUIPMENT causing this MYSTIFYING, effect that so maany other science ideologies are BASED on!!!! One day we might think....OH...&#$*!.....it was our stupid equipment. —Preceding unsigned comment added by 165.145.103.161 (talk) 06:35, 8 January 2009 (UTC)

It's known that the effect isn't caused by interaction with the apparatus. See interaction-free measurement and the linked articles. In the case of the double-slit experiment, consider the fact that the "photon detector" at one of the slits, however it works, only detects half of the photons. If the measurement effect were due to physical interaction then you ought to see a 50% interference pattern on the screen from the photons that evaded the measuring device (combined with some other pattern from the photons that were detected). But that's not what quantum mechanics predicts and it's not what's observed. The photon's behavior is also modified by the fact that it could have interacted with the measurement apparatus but didn't. -- BenRG (talk) 10:38, 8 January 2009 (UTC)

Indeed. Quantum theory is SO bizarre and SO contrary to people's expectations that great minds have tried to wiggle their way out from under the experimental evidence pretty much since Einstein got everyone excited about the problem again. This is a very well proven thing. Much of our modern electronics wouldn't work if it wasn't true. Have you ever seen a blue LED? Ever used a flash memory? Well there you are then. No quantum theory - no MP3 players...you choose! SteveBaker (talk) 16:39, 8 January 2009 (UTC)

I'm perfectly happy to accept that light behaves neither like billiard balls nor like water waves, but I refuse to accept that the universe alters its behaviour on the basis of whether humans are looking at it. How does this photon detector work? Why does it only pick up half the photons? Why don't I just stick an opaque photosensitive screen over one of the slits? Now I've transformed it into two single slit experiments! There's a "photon detector" that won't miss ANY of the photons. Can anybody here who accepts the result of this experiment actually, genuinely explain the precise mechanism by which these photon detectors work? The linked articles on interaction free measurement are unintelligible. Maelin (Talk | Contribs) 00:26, 9 January 2009 (UTC)

Well, you may refuse all you like - but that's what happens. The photon detector works via the photoelectric effect - for which we have an article. I think BenG says it only picks up half the photons because he's imagining an experiment where only one of the slits has a photodetector behind it. Just imagine two photodetectors - one behind each slit - then you know exactly where the photons went...it doesn't help you. The diffraction pattern DOES disappear when you try to find out where the photons went. Yes, it's deeply weird. I know you're going to start looking for trivial errors in the experimental approach - but don't you imagine that far greater minds than either yours or mine have not been examining that question for the close to hundred years that we've known of this 'wave/particle duality' thing? The effect IS real - and we use it (and it's consequences) all the time in day to day electronics. Like I said - the universe is WEIRD at the quantum level. SteveBaker (talk) 06:03, 9 January 2009 (UTC)

To make it even more weird (correct me if I'm wrong though), if you use entangled pairs of photons and send each one of the pair to a different double-slit experiment, counting the photons at one of the experiments also destroys the interference pattern at the other one. At least I think I've read that paper... Franamax (talk) 06:42, 9 January 2009 (UTC)

Steve, I don't like this "my head hurts and so should yours" approach to explaining quantum mechanics (to quote you from a thread below this one). The basic quantum rules have been known since the 1920s. You can learn them and use them to figure out the outcomes of experiments of this kind. It's not magic. People are fond of saying that no one understands quantum mechanics—a virtually meaningless statement. Do you understand gravity? Sure you understand some things about it, but do you really truly understand it, at the deepest imaginable level? Of course not. The quantum rules are unsatisfying as a just-so story about the universe, but so is every aspect of current physics. Why are there three particle generations? Why is the strong force so elegant and the electroweak force so ugly? The explanations for these things, if we ever find them, will probably be unsatisfying themselves. That's the nature of the frontiers of physics.

Also, the quantum rules may be strange, but so are "the classical rules". People are just more used to them. They happily talk about "unbiased coins" that have a "50% probability" of coming up heads, blissfully unaware of what crazy nonsense they're spouting. It's impossible to make sense of classical probabilities, and all of science is based on them (all experiments have error bars), so all of science is meaningless. Yet somehow it works anyway. Quantum mechanics is no more absurd than that.

I think I'd better revise my previous response in this thread. The measurement effect is due to interaction with the device, in that it is the construction of the device—the nucleons and electrons that make it up—that dictates its effect on the experiment, not mysterious measurement dust that adheres only to measurement devices. But quantum mechanics happens to have a concept of null measurement, or null interaction, which doesn't exist in classical physics, and which says that an interaction that could (probabilistically) have taken place, but didn't, has an effect that's very similar to the effect when it does take place. The presence of the apparatus introduces a possibility of interaction, and that has an effect on the behavior of the system even in trials where no interaction actually takes place (in the ordinary classical sense—things bouncing off of each other, if you like). To put it another way, interference effects show up when information about which way the particle went is lost, and conversely, interference effects don't show up when information about the path is retained, in any form whatever. A detector at one of the slits yields which-path information whether or not it detects a particle (if it doesn't detect one, that's evidence that the particle didn't go that way). As a result it affects the interference pattern whether or not it detects a particle. This can all be formalized. -- BenRG (talk) 08:42, 9 January 2009 (UTC)

Sorry? The photoelectric effect? You mean the one where a photon hits a bit of metal and is absorbed and an electron pops out? So let's see. You have two slits, and photons go through them and, wow, even though we know that light has particle behaviour (due, in fact, to the photoelectric effect), it turns out to still have a wavelike behaviour because we get interference patterns even if we only send one photon through at a time. And then, what, you shove a bit of metal in front of one of the slits, and sit there catching the electrons that pop out as the photons are absorbed, and you say, "Look! The interference pattern has collapsed now that we are observing the system! Amazing!" Obviously you've ruined the experiment because you've stuck a bit of damn metal in front of one of the slits to catch the photons. If you still got interference patterns EVEN WITH one of the slits blocked up by your detector, now THAT would be really amazing. But this is like being amazed that a Magic Eye vanishes if you hold your hand over one of your eyes. Maelin (Talk | Contribs) 09:04, 9 January 2009 (UTC)

Maelin....spot on...you and I are of like minds. Theres all this scientific talk meandering off in a thousand directions, without actually adressing the plain and simple issue....The device/detection method..is there irrefutable proof, that its not the PHYSICAL equipment CAUSING this effect? If someone says No, fine. If someone says yes....without redirecting to any 'thought experiments' as backup, please explain in laymans terms (well as close as possible - this IS quantum physics) WHY this is the case... —Preceding unsigned comment added by 165.145.117.62 (talk) 10:24, 9 January 2009 (UTC)

I want to know exactly HOW it is that photons are detected, do they fire electrons at it? does someone have the details (in simple terms) of how they detect the photon? Where do they detect it? at the slit or anywhere between the slit and the screen? thise sort of details? Can someone tell me exactly how the experiemtn is set up? in a vacuum? whats the detector etc etc? —Preceding unsigned comment added by 165.145.117.62 (talk) 11:15, 9 January 2009 (UTC)

Here's a weird proposition for possible explanation of the double-slit experiment outcome ... Perhaps photons and electrons (and maybe even all things 'teeny tiny quantumy') naturally exist & travel around as WAVES (naturally being on their own without any interferrence of other particles) ...or frequencies if you will. BUT - As soon as you introduce another different tiny PARTICLE (in this case electron to a photon-wave or photon to an electron-wave) , the wave collapses, and photon-wave becomes photon-particle and suddlenly EXISTS and ofcourse visce verce.......

If all this were true, how scary would it be that in total darkness, nothing really exists ?? eeeeek!!!!! —Preceding unsigned comment added by 165.145.117.62 (talk) 12:45, 9 January 2009 (UTC)

dextrose & ct scans

why must dextrose be held for a period of time prior to performing a ct scan? —Preceding unsigned comment added by Cecollins64 (talk • contribs) 10:11, 7 January 2009 (UTC)

Have you read our article on Computed tomography? --Jayron32.talk.contribs 13:25, 7 January 2009 (UTC)

I can't see anything in that article that's relevant; perhaps I've overlooked it. In any case, I suspect that our questioner may be thinking of a PET scan (or a combined CT/PET scan) rather than a CT scan per se. The PET scan article indicates that dextrose should be held if the PET scan uses fluorodeoxyglucose (FDG) as its tracer molecule, as glucose/dextrose etc. would compete with the tracer for uptake. - Nunh-huh 13:58, 8 January 2009 (UTC)

Darting PVDF membrane magic trick

I recently prepared a peice of PVDF membrane by soaking breifly in methanol, and then transfering to a container of water. I noticed that the strip of membrane darted around the container, hitting the sides and bouncing back. Eventually it slowed down and stopped but what caused this? --129.125.160.178 (talk) 13:40, 7 January 2009 (UTC)

Sounds like Brownian motion. Apparently some reaction took place which gave off energy that became motion. Hopefully others will have the specifics. StuRat (talk) 18:54, 7 January 2009 (UTC)

Brownian motion only is visible at the microscopic level, it is probably osmotic pressure. Graeme Bartlett (talk) 21:01, 7 January 2009 (UTC)

The behavior sounds more like you get when you drop a small piece of dry ice onto water - the rapid liberation of gas from the dry ice makes it behave like a hovercraft and it rapidly zips around the surface. If this membrane absorbed a ton of methanol and then for some reason caused it to evaporate out when it came in contact with the water - then the methanol vapor would make it zip around like that. Sadly, I don't know enough about this weird membranous stuff to comment further. SteveBaker (talk) 15:47, 8 January 2009 (UTC)

Scabies

What causes intense itching in scabies? —Preceding unsigned comment added by 59.103.69.8 (talk) 14:34, 7 January 2009 (UTC)

Our article gives two causes: "action of the mites moving within the skin and on the skin itself", and "presence of the eggs produces a massive allergic response" - Nunh-huh 15:07, 7 January 2009 (UTC)

you better have an explanation for this

This question has been removed. Please do not start debates or soapbox on the Reference Desk. Matt Deres (talk) 17:10, 7 January 2009 (UTC)

I (Matt Deres (talk)) have reinstated the question:

In my heart I know that God simply cannot exist. Yet I keep finding things that seem to debunk current "scientific" understandings of how the universe, the earth and humanity came to be. How can there be identical lines of DNA coding in identical order for the structure of an eye in an octopus as in a human when they aparently evolved seperately and the order of the sequence wouldn't effect the program the lines were switched? Why do people cling to the idea that fossils don't form for millions of years when a quick trip to the local quarry will present fossilised mining equipment and boot prints? Why do we still place our faith in carbon 14 dating when it has proven inaccurate every single time sombody has tried to trick the system? Is there really a single scrap of evidence that supports evolution over intelligent design? Can anybody show me an intermediate fossil of any missing link which hasn't been found to have been tampered with? When Dawkins himself is saying that the only plausible explanation for this particular universe happening is that there are infinite parralel universes with every posibility, siting the existence of this universe as proof of this theory, what seperates the Athiests from every other faith based religion? —Preceding unsigned comment added by 194.80.240.66 (talk) 16:53, 7 January 2009 (UTC)

OK - I'll bite:

• In my heart I know that God simply cannot exist. - If you want to treat things as a scientist then the "in my heart" stuff has got to go. You need a reason.
• Yet I keep finding things that seem to debunk current "scientific" understandings of how the universe, the earth and humanity came to be. - When that happens, scientists get very, very excited - because it means we can learn something new.
• How can there be identical lines of DNA coding in identical order for the structure of an eye in an octopus as in a human when they aparently evolved seperately and the order of the sequence wouldn't effect the program the lines were switched? - What makes you think that's true? I doubt very much that enough research has been done into the DNA responsible for the development of eyes in Octopii and Humans to know this. Where did you find this information? Sure, there will be proteins and other structures that are common between the two systems - but that's because those chemicals were probably used for something else before they came to be used inside eyes - and hence they would have evolved prior to the last common ancestor of man and cephalapod. My inclination is to yell "BOGUS!!!" at this claim - until/unless there is some solid proof that it's true.
• Why do people cling to the idea that fossils don't form for millions of years when a quick trip to the local quarry will present fossilised mining equipment and boot prints? - Eh? There is no fossilised mining equipment. Boot prints are a different matter - a print can fill with something like concrete that sets hard in a short period - but technically that's not a fossil. Again - I don't believe this claim. Fossils do indeed take a very long time to form...and we can easily prove that.
• Why do we still place our faith in carbon 14 dating when it has proven inaccurate every single time sombody has tried to trick the system? - Sure you CAN trick the system (eg by injecting some extra carbon-14 into your sample or irradiating it with a strong neutron source). But if you DON'T trick the system - if you use it honestly - it works rather well. But this is true of ANY scientific process. If I write a scientific paper that says that the rate that a pendulum swings is proportionate to the weight of the pendulum times it's length (which is NOT true BTW) - then should everyone rush off and build clocks on that basis? Hell no! You repeat my experiment first (and you find it's wrong - so you publish a report saying why - and then nobody trusts me anymore). Trusting the scientists that did the C14 dating in any particular case is certainly important - and that's why we have things like peer review and the general principle that we don't trust the results of some experiment until it's been independantly verified. The fact that it's POSSIBLE to cheat - doesn't make the testing any less valid providing we stick to the rules for scientific acceptance.
• Is there really a single scrap of evidence that supports evolution over intelligent design? - YES! Absolutely! Ask anyone who runs a hospital about how bacteria evolve immunity to our drugs. Examine the way that humans have become lactose-tolerant in response to the domestication of cattle. Actually READ Darwin's book - it's really quite compelling. (Heck - I read the bible from cover to cover - it's the least you can do to return the favor!) I'd turn the question around - where is there any piece of evidence that intelligent design is true? I've never seen anything.
• Can anybody show me an intermediate fossil of any missing link which hasn't been found to have been tampered with? - Sure - go to any decent natural history museum that has rows of fossil human skulls - what's on display is likely to be replicas - however, if you politely ask the curator whether you could please examine the original bones - they'll generally find a time when you can come and do that. You'll see a set of gradual changes from something that's clearly not "human" into something that is - with very small changes at each stage along the way. It's completely compelling. This claim from the intelligent design nut-jobs that there are these enormous gaps in the fossil record is completely bogus. Bear in mind that these people are more than happy to lie to you about stuff like this - they don't have independent testing and peer review - any idiot publishes something - and the rest parrot it as if it were truth. Take nothing on trust - go to a good museum and see for yourself.
• When Dawkins himself is saying that the only plausible explanation for this particular universe happening is that there are infinite parralel universes with every posibility, siting the existence of this universe as proof of this theory, what seperates the Athiests from every other faith based religion? - I don't recall hearing or reading that Richard Dawkins said that. However, he's just one more person who has an opinion - your use of "himself" as though he were some great high-priest of science and/or atheism shows your need to have a heirarchy of priests telling you how to think. The world of both science and atheism don't work like that. He's just another guy with an opinion...and sometimes (albeit rarely) he's wrong.

We don't know (and almost certainly CAN'T know) about the existence of parallel universes. I personally find them to be a rather elegant (if deeply weird) explanation for things like the 'Schrodinger's cat' thought experiment - but there are no solid reasons why the alternative explanations involving the effect of observers on wave-function collapse is an equally valid explanation that is only slightly weird. Certainly, the explanation of why the universe happens to have the properties it has comes down to something like "well in order for there to be thinking beings to ask the question - it has to be how it is". So either the universe just happens to have properties that are suitable for us...and that's all just a coincidence...or perhaps no matter what properties the universe might have, some form of intelligent beings would have arisen - and it just happens that it come out this way...or PERHAPS it was all magicked into existance by The Great Pink Aardvark In The Sky...or perhaps there are an infinite number of parallel universes and the ones that have properties close to the one we happen to live in all have intelligent beings asking this question on THEIR Wikipedia reference desks. I don't think we have an answer for that one. Occam's razor (which is a great principle to live by) says that we should pick the simplest explanation until we have evidence to the contrary - so "it's all just a coincidence" is probably the best guess that most scientists would give...although if they are honest, they'll add "but we don't know for sure". Science is not 'finished' - there are things we don't know yet. It's still possible that something like string theory will come up with a reason why the fundamental constants of the universe come out the way they are - it's possible that there is some simple reason why the speed of light is what it is - why the charge on the electron is just right for making atoms and molecules work. Certainly you can be an atheist without subscribing to the "many worlds hypothesis".

SteveBaker (talk) 17:33, 7 January 2009 (UTC)

I'd also like to add, that while science will never be able to provide all the answers, as there's always more to learn, the same is true of religion. Just as we don't really know the reason for the existence of the universe, saying God created it doesn't help, as we then need an explanation for where God came from. If you accept that God was always there, or just mysteriously popped into existence, how is that any different from accepting that the universe was always there or just mysteriously popped into existence ? StuRat (talk) 18:50, 7 January 2009 (UTC)

Anyone who has spent any time in the usenet talk.origins debates would immediately recognize the questions above as creationist trolling, notwithstanding the "I believe God doesn't exist" disclaimer preceding them. I see this so often from creationists, it's hard for me to assume good faith here. ~Amatulić (talk) 19:08, 7 January 2009 (UTC)

I agree - but if you simply delete or refuse to answer, that will be a victory for the nut-jobs. "You suppressed me" is a rallying cry. So - I prefer to take the OP at face value, answer the questions as posed as honestly and accurately as possible...pretty much what we always do around here. Nothing the OP said is hard to explain or refute - except for the things that don't seem to be true. I'd be VERY surprised if there was any evidence that Octopus DNA has similar coding to Human DNA for the process of eye development. If there is no evidence for it - then it's almost certainly untrue. I have no clue why ANYONE would imagine that construction equipment becomes 'fossilised'?!? That can only be a misunderstanding of what the term means. All we can do for the people afflicted with this terrible meme-infection is to try to educate. It's what we do here. SteveBaker (talk) 19:35, 7 January 2009 (UTC)

It's at least controversial that the octopus and the human eye represent convergent evolution, as previously thought. There is about a 70% genetic similarity, probably traceable to a conserved ancestral gene set. For a discussion of the genetics of the convergent evolution of the camera eye, see Ogura, Atsushi (2004). "Comparative Analysis of Gene Expression for Convergent Evolution of Camera Eye Between Octopus and Human" (PDF). Genome Research. 14: 1555–1561. Retrieved 2009-01-08. {{cite journal}}: Cite has empty unknown parameter: |month= (help); Unknown parameter |coauthors= ignored (|author= suggested) (help). It's not the data that's suspicious, but rather the idea that the data somehow does anything but support evolution. It's a good example of science being self-correcting (as new data is obtained, understanding changes), and nothing for creationists to be shouting "Aha!" about. - Nunh-huh 01:05, 8 January 2009 (UTC)

The problem with the creationist/ID people's take on data like this is that the work isn't done yet. I'd have no problem with their extreme brand of scepticism if only they applied the same standards to their own theories. Where are the peer-reviewed journals? Where are the chains of logic and evidence for this nutty idea they have? I can't be merely sceptical about their stuff because they don't HAVE any stuff. There is some dogma - but zero evidence. SteveBaker (talk) 03:27, 8 January 2009 (UTC)

I cannot help quoting myself from these desks. I apologize for this. So, I have a theory about the existence of God, that may possibly be of some help. I am convinced, with some good arguments indeed, that God exists, and does not exist, at the same time. This may sound contradictory at a first glance; but after a short reflection, you'll agree there is no real contradiction; clearly it looks paradoxical to us just because our mind is limited. But if you think, anybody is able to just exist, or, just not to exist: evidently God, in his/her omnipotence, is able to do both simultaneously. Of course I can't prove this as a theorem, but I wish to remark that this principle allows to explain quite easily any Religious Dogma, Sacred Mystery etc. (for instance: the Trinity Mystery, 3=1, follows as an exercise from 1=0). Moreover, this principle embraces and welcomes all different points of view in matter of faith and religion, including the heretical and the schismatic ones, and even atheism, and in fact smooths their differences, which are a source of animosity and misunderstanding between men. I am, correspondingly, believer and not believer at the same time. A position very suitable for tolerance indeed, and I am delighted to confront it with any other one (who created the stars? God. When? Never. etc)--PMajer (talk) 01:17, 8 January 2009 (UTC)

Great - so you have a theory. It's not falsifiable so I can't prove it's not true - and you have no evidence so you can't prove that it IS true. The trouble is that I could sit here all day and all night for weeks and weeks and type in other theories...my current 'Pink Aardvark' theory for example - the Russel's teapot-in-orbit-around-Mars theory. The problem for every thinking being on the planet is to know which theory to pick. Why a here-but-not-here-God and not a bunch of pink aardvarks? You have no evidence - neither do I - I can't disprove yours and you can't disprove mine...but the problem is that there are a million - or a billion - or a trillion of my crazy ideas and only one of yours. Mine are all just as plausible as yours. With no way to choose between them - they are all just as probable. So what are the odds that your's is true? Zero...near as dammit. So as rational beings, our only LOGICAL conclusion is that there are no gods - and that things that are unfalsifiable might as well be ignored - at least until we have some pretty solid evidence. It's POSSIBLE that you're right - but it's utterly, astronomically improbable. So I call "BOGUS" on your theory...like every other religion on the planet it's a complete pile of crap. SteveBaker (talk) 03:11, 8 January 2009 (UTC)

hey, hey, that's just irony... which doesn't mean I'm not serious. I personally do not feel the religious problem, nor I feel the need of having any belief about it more than about the teapot. But I equally respect who has a religious faith and who has not --with a small personal sympathy for the latter, statistically. But: as long as they remember that their belief is just a personal belief (in particular, that has nothing to do with science). So, I strongly agree and sympatize with what you wrote, except your last sentence, to whom I give, I'm sorry, a kind of self-referencing collocation.--PMajer (talk) 10:46, 8 January 2009 (UTC)

Your theory has certain resemblances to negative theology, PMajer. Deor (talk) 13:51, 8 January 2009 (UTC)

I hope you liked it. I invented it expressly for discussing with creationists, as a young student, one day that they knocked at my door, having great fun. And to their credit, they gave to my theory much more credit that I have gathered here --that's no problem of course, it's kind of friendly fire that I'm used too (after all Matt Deres knew very well what he did when removed the OP). So, I give you my theory for free, should they knok at your door too. As to the originality issue, I'm sorry to firmly decline any resemblance with negative theology ;) --PMajer (talk) 15:47, 8 January 2009 (UTC)

I cannot help quoting myself from these desks. I'm sorry - where was the quote? Anyway, if you want a good argument for the existence of god(s), how's this one? I'll even use science against itself. According to the many worlds interpretation of quantum mechanics, there may be an infinite number of alternate universes. If there are an infinite number of alternate universes, it is inevitable that god(s) will exist in at least one of these universes. After all, if an infinite number of monkeys can type out the script for Hamlet, an infinite number of universes will have god(s) in at least one of them. Now, where do I collect my Nobel prize? :) 216.239.234.196 (talk) 13:52, 8 January 2009 (UTC)

In one or more of these universes, for sure; most likely even in the present one according to it's level ;) --131.114.72.215 (talk) 14:02, 8 January 2009 (UTC)

There are several problems with '216s suggestion:

1. We don't know that many-worlds is true. We may never know that it's true - it's a neat explanation - but it's absolutely unfalsifiable right now - so it's up there with the teapot, the aardvarks, and god(s). Invoking an unfalsifiable claim in order to "prove" another unfalsifiable claim is exactly like me saying: "The universe is ruled by Pink Aardvarks and I believe that Pink Aardvarks create gods as a kind of hobby. Hence god exists."...that's an unbelievably stupid argument - but it's logically no different than claiming that god must exist because there are infinitely many universes when we can't prove that there are infinitely many universes.
2. Most versions of many-worlds say that the laws of nature would be the same in all of the universes because they are all created as a result of quantum events such as Schrodinger's cat. You stuff the cat into the box - the poison gas is either released by a quantum event or not - our universe splits into two copies that are utterly identical EXCEPT that the poison gas is release in one and not in the other. In this (more likely IMHO) version of many worlds, the only differences between them are the consequences of all of the quantum events since the big bang. However, it doesn't seem likely that the speed of light or the charge on the electron would be any different in any of those other universes. If the laws of nature are identical in all parallel worlds then gods (which require 'magic' in order to make them omnipotent) can't exist in the other universes any more than they can in this one. That busts your argument wide open. However, you may choose to define "gods" as "super-advanced life forms" and note that "any sufficiently advanced technology is indistinguishable from magic". But these so-called gods still can't fly faster than the speed of light or precisely measure both the position and momentum of an electron. Hence they are neither omnipotent nor omniscient - which I think disqualifies them from the "God" title for most religious nuts.
3. So maybe you're right - but who cares? These gods could not possibly affect us in any way shape or form - so we needn't bother worshipping them or fretting about whether they are planning to send us to hell for our little indescretions where we'll be tortured for an infinite amount of time by those guys with the pointy tails, tridents and bright red skin.
4. If you accept the common definition of a god as "a creature with omnipotent powers" - something with literally no limits on capability - then your claim that there are an infinite number of universes containing gods which (because they have literally no limits on their powers) would allow them to be able to cross the boundaries between universes. This would inevitably lead to an INFINITE number of them deciding to come to our universe and an INFINITE number of them would be messing around in our lives. An infinite number of them would choose to manifest themselves. If you believe THAT then you have a huge problem with the whole worship thing! No matter which one you pick - you're in deep trouble with the other infinity-minus-one of them!

So - no - you don't get to sneak God past the laws of physics like that. This is another very stupid theory. Sorry. SteveBaker (talk) 15:27, 8 January 2009 (UTC)

I think 216 was ironic too --PMajer (talk) 19:44, 8 January 2009 (UTC)

If so then both you and 216 need to stop making "ironic" posts because as far as most of us are concerned, the appropriate adjective is not "ironic" - it's "wrong". Stick to writing the truth please. (Personally - I think you're just falling back on that when I shred your crazy theories into teeny-tiny shreds with rather elementary logic.) SteveBaker (talk) 00:17, 9 January 2009 (UTC)

Maybe you are right that irony is not appropriate here, and could be misleading for a simple-minded reader. Ok, bye. PS: As to my poor theory, it's even too kind of you to give it a microsopic, still non zero probability... thanks (you know, there is inside a minor problem with the Principle of contradiction... have a look to it btw, just to improve your elementary logic)--PMajer (talk) 14:07, 9 January 2009 (UTC)

It's not fair play to stir up debate and then object to the form your counterpart's discourse takes. I'm just sayin'. --Milkbreath (talk) 14:13, 9 January 2009 (UTC)

I appologize. I didn't mean for that post to be taken seriously. Anyway, it is not merely a very stupid theory, it is absurd. 216.239.234.196 (talk) 16:56, 9 January 2009 (UTC)

Does this represent inertia?

If I drop an egg on to a hard surface and the egg Breaks (obviously). Is this a representation of inertia at work?? —Preceding unsigned comment added by 65.184.51.249 (talk) 17:47, 7 January 2009 (UTC)

Eh... inertia is involved, to be sure, but I wouldn't consider that a good representation of "inertia at work" -- I'd think it's a better representation of acceleration/g-forces and structural load limits. Specifically, I don't think the tendency of the egg, or of the egg's contents, to remain in motion is what causes the egg to break.

I suggest that examples a fixed force on differently massed objects would be a more clear representation -- for example, it's easier to impart motion to a baseball than a shotput (a mass difference factor of about 50). — Lomn 18:08, 7 January 2009 (UTC)

Urgh...kinda related. Newton's 1st law (which is really talking about inertia) says that an object will keep moving in a straight line at constant speed until acted on by an external force. So your egg is trying to move at constant speed until it hits the hard surface. The inertia of the part of the egg furthest from the surface is still trying to do that when the front end hits...so it's resistance to that change in speed is what imparts a force against the surface. So the egg has to decelerate to a stop - and because F=ma (yep - that Newton fellow again...the second law this time) that accelleration imposes a force against the surface. Then (because every action has an equal and opposite reaction - per Newton's third law) the surface has to push back with an equal but opposite force...which cracks open the egg. So I suppose you could maybe argue that inertia started the whole chain of events (which in reality is just one event). If the egg had no mass or no velocity - then it would have had no inertia and it would have simply stopped without breaking. But the first law is really just a special case of the second. When F=0 (there is no force acting on an object), and m > 0 (it has mass) F=ma says that 'a' has to be zero...so no accelleration is possible. If you look at it like that, then the whole 'inertia' thing is a bit of a non-event because it's just a special case when there are no forces lying around. So I dunno. There are better examples. Swing an object around on the end of a piece of string - then let go of the string. As soon as the force due to the tension in the string drops to zero - the object goes off in a straight line...which is a perfect example of inertia in action. SteveBaker (talk) 18:30, 7 January 2009 (UTC)

This reminds me of bad test questions I always had, where the answer was "kind of, but not really". Unfortunately, they were always true or false questions and I never could quite guess which way the teacher was going to rule. StuRat (talk) 18:37, 7 January 2009 (UTC)

I'm going to go ahead and say "No". The law applies to objects not being acted on by outside forces. The law says nothing about when happens when you DO apply an outside force. So the only cases you can say Inertia applies is when there are no outside forces, or more realistically, no significant outside forces. In this case we have two forces: The force of gravity and the force of the ground acting on the egg. Both of these forces are significant since without either one the egg would not break. Anythingapplied (talk) 23:36, 7 January 2009 (UTC)

If an egg was on the seat of a moving car,going, say 60 miles per hour, not constrained from moving forward, and you suddenly applied the brakes, the egg would continue moving forward until it hit something. It might break on the dashboard. This is why wearing seatbelts/shoulder straps is a good idea. Edison (talk) 23:47, 7 January 2009 (UTC)

.249, are you sure you didn't mean to say entropy rather than inertia? Because, yes, the fact that intact eggs break all the time but broken eggs never become intact is a classic example of increasing entropy. --Sean 13:03, 8 January 2009 (UTC)

Buying Optical fiber

How much does it cost? (an estimation is enough) Where can I buy it? (and similar things) --Mr.K. (talk) 18:27, 7 January 2009 (UTC)

A Google search on "Buy optical fibre" turned up many possible places. However, you need to be MUCH more specific about what you need. There are many different things called "optical fibre". There is cheap, short glass fibre that is used in things like toys and those lamps that are made from a bundle of fibres. There is hugely pure glass for which a 20 mile length of the stuff is more transparent than a single pane of window glass. There is single-mode and multi-mode fibre which had graded refractive index that varies from the core to the outside to better 'steer' the light...there are bundles of fibres where the arrangement of the fibres is identical on both ends of the 'cable' so you can send pictures through it. There are bundles of fibres that are just to get light from A to B where the fibres can be all muddled up inside the cable. There are fibres encased in various sheaths to protect them and there are bare fibres with no sheaths. The length you need makes a MASSIVE difference to the price. If there are connectors on the ends of the fibres - or if the ends are cut at precisely 90 degrees and carefully polished so they make a good optical connection - then that's yet another parameter. In short - I can't give you even an estimate on price. But do the Google search and you'll find out for yourself. SteveBaker (talk) 18:37, 7 January 2009 (UTC)

If you don't want to buy them for industrial purposes, but for a DIY project you could try a company that buys electronic scrap. Old copiers and fax machines have a strip of (rather short) good quality optical fibers. Apart from that, as Steve said we can only guess. Lisa4edit76.97.245.5 (talk) 23:40, 7 January 2009 (UTC)

January 8

problem in thermodynamics

friends, if hydrogen and oxygen are present in a sphere of radius of 6cm, in a ratio of 2:1, and they are burned, what will be the pressure exerted on the walls of the sphere? will it be able to move a vehicle with a mass of 25kg if appropriately transmitted? —Preceding unsigned comment added by 117.193.227.111 (talk) 02:10, 8 January 2009 (UTC)

The former would appear to be highly dependent on the quantity of hydrogen and oxygen. The latter seems unlikely; "if appropriately transmitted" seems to be the core problem rather than a minor issue to gloss over. — Lomn 02:40, 8 January 2009 (UTC)

To clarify my dismissal of the second part of the question: what motive force does a closed pressurized scuba tank provide? None. The vessel is rigid and has no opening, just as you appear to have theorized with a "sphere of radius 6cm". There's nothing to "appropriately transmit." If you're willing to allow for a nozzle of some sort, then yes, said pressure can move a vehicle of any weight. It just may not move it much. — Lomn 02:51, 8 January 2009 (UTC)

Yeah - I think we can assume that the OP has a valve on the outside of the sphere that lets air in or steam out depending on...whatever...and some kind of a piston or turbine or something to efficiently extract energy from the reaction. In an IDEAL world - any amount of pressure can move any mass of object - but in the presence of friction, the force of 'static' friction ('stiction') will actually prevent things from moving at all - unless there is a reasonable amount of energy liberated from the sphere. I rather suspect nothing would happen - but that's "gut feel" kind of a thing. SteveBaker (talk) 02:59, 8 January 2009 (UTC)

Well, you'd have the same mass of steam/water/water-vapor left inside. It's kinda tricky to figure out the pressure of the water vapor versus the pressure of the hydrogen/oxygen mixture because there is temperature change as a result of the exothermic reaction and a lot would depend on how well that temperature is maintained subsequently. So I rather think there would be not a whole lot of change. If the water would condense back to a liquid - then the pressure inside would drop to essentially zero - but water boils at room temperature in a vacuum - so we know that's not gonna happen. Well - assuming there is SOME change - then with appropriate transmission, we need to know about the frictional forces for your vehicle - the mass of the vehicle doesn't help us to calculate that. In a perfect frictionless world, any force, however small can move a vehicle of any mass - albeit pretty slowly! So you really havn't given us anything like enough information. Sorry! SteveBaker (talk) 02:46, 8 January 2009 (UTC)

An aside - hydrogen was used as the fuel in the very first vehicle powered by an internal combustion engine, which was built by Swiss inventor François Isaac de Rivaz in 1807. Gandalf61 (talk) 10:45, 8 January 2009 (UTC)

That's true - but it was working like a gasoline engine. Inside the cylinder would be AIR and hydrogen. When the hydrogen burned with the oxygen, water was formed but the remaining nitrogen from the air (4/5ths of the air is nitrogen, remember) would be heated by the combustion - expand greatly and force the piston down the cylinder. Our OP is talking about pure oxygen & hydrogen - so there is no nitrogen there to act as the "working fluid" (in heat engine terms). I don't know whether water vapor (which would be all that was left inside the OP's sphere) would have more or less pressure than the original gasses because that depends on heat and initial pressure - and we don't know what those are without knowing a lot more about the 'engine'. These days, we know that reacting hydrogen with oxygen from the air in a 'fuel cell' to produce electricity without generating heat is the way to go with hydrogen fuelled vehicles. Hydrogen simply doesn't have enough energy density to efficiently replace gasoline in conventional cars. SteveBaker (talk) 15:05, 8 January 2009 (UTC)

The volume of a ball of 6 cm radius is V = 904.8 cm³. I assume the H2/O2 mixture is initially under standard pressure (p = 101,325 Pa) and at standard temperature (T = 25 °C = 298.15 K) - the amount of substance is p*V/(R*T) according to the ideal gas law (do I need to mention that the units have to be correct when you do the calculations?). Multiply that by 2/3 in order to get the amount of water resulting from the combustion (1 mol O2 + 2 mol H2 -> 2 mol H2O).

Now look up the standard enthalpy change of formation for water - in the gaseous state it's ΔH = -241.8 kJ/mol. Approximating water vapor as being an ideal gas, you can first calculate the pressure of the water vapor at standard temperature by p₀ = (amount of water)*R*T/pp₀ = (amount of water)*R*T/V (edit: you don't need that), then compute the temperature rise as ΔT = ΔH/c_V, where c_V is the (molar) heat capacity at constant volume (c_V = 6*R for an ideal gas with 3 internal degrees of freedom, like water is approximately). Now you can again use the ideal gas law to compute the resulting pressure at the temperature you just calculated, with the volume of the ball and the amount of substance of water.

This will be an upper limit for the pressure. Once the combustion process is over, the pressure will fall again as heat is conducted through the spherical shell. Also note that water vapor is not really an ideal gas and also that at high temperatures, the heat capacity increases, so the total temperature will be a bit lower than what you get from the simple calculation.

Icek (talk) 15:18, 8 January 2009 (UTC)

So what's the answer? Did you crunch the numbers? Well, anyway - if the thing were to work, the ball would have to be a pretty chunky piece of metal (probably) - so the conduction of heat away from the resulting water vapor would probably be significant. SteveBaker (talk) 19:31, 8 January 2009 (UTC)

It's only 1.166 MPa, but the temperature is quite high, 5145 K (which means that it will be considerably lower at least due to vibrational degrees of freedom; they raise c_V to 9*R for higher temperatures). Icek (talk) 11:33, 9 January 2009 (UTC)

In Electric current(AC-230V) transmission-household wiring, why cannot we sense Nutral current using normal Current tester?

why cannot we sense Nutral current using tester? —Preceding unsigned comment added by Ranga333eie (talk • contribs) 05:19, 8 January 2009 (UTC)

There is no such thing as neutral current. A neutral wire simply completes the circuit by carrying the alternating current from the live wire, and is usually the same potential as (and connected to) earth/ground. So there's nothing to measure. (Note that this DOES NOT mean it's safe to touch the neutral wire, it's not or at least not always.) Nil Einne (talk) 13:35, 8 January 2009 (UTC)

Purely for the sake of pedantic completeness, there is neutral current - but it's definitely not something you would measure with a current tester. Gandalf61 (talk) 13:55, 8 January 2009 (UTC)

Aarrh, I hate quantum physics and its wacky names ;-P Nil Einne (talk) 18:11, 8 January 2009 (UTC)

If you were to insert an ac ammeter into the neutral lead of a household appliance then of course you would measure the electric current drawn by that appliance so I dont understand the Q (or the above answers for that matter). The neutral is only connected to earth in any installation at the consumer unit.--GreenSpigot (talk) 18:22, 8 January 2009 (UTC)

In some countries, a 230 volt appliance has a hot lead (at 230 volts relative to earth ground) and a neutral lead, which is connected to earth ground back at the power panel, so has very small voltage difference from ground, as well as a safety ground wire, which carries no current if the equipment is working properly, but could carry fault current if the insulation failed somewhere in the circuit. In these locations, the neutral current should be equal to the hot lead current on the equipment power cord. In other countries like the U.S., a 230 volt to 240 volt appliance has 2 hot leads, each at 120 volts relative to ground, as well as a ground conductor. Each of the hot leads should carry the full load current, and there is no neutral conductor. The safety ground should carry no current under normal conditions. Edison (talk) 19:44, 8 January 2009 (UTC)

Perhaps the OP doesn't understand the difference between voltage and current, or is using the word 'current' in the colloquial sense of 'something to do with electrical power'. I say this because most householders lack the equipment to measure the current in their mains (house current) wiring. All most people have is a voltmeter or a neon tester, so perhaps when the OP writes "current tester" he really means "voltage tester". In that case, as Edison says, the neutral wire may be at or near ground potential and so a voltage tester will read practically zero. To check the actual current in the neutral wire without breaking it, you need a current clamp. --Heron (talk) 20:41, 8 January 2009 (UTC)

Light as waves AND particles

Our first observation of waves and wave like action in nature was with ripples of water in a pond. The little particles of water are moving in a wave like fashion up and down. This is what we picture in our heads when we think of light waves also....Why is it that it is incorrect to assume that light can't be light particles moving up and down in a wave like fashion....why can it only be one or the other PARTICLE or WAVE? How is it that they proved that photons dont move up and down in a wave like fashion as they travel? —Preceding unsigned comment added by 165.145.103.161 (talk) 10:12, 8 January 2009 (UTC)

Light exhibits properties of both wave and particle. It is not "one or the other". But it also is not a particle moving in a sine pattern up or down. Such a model would not explain interference, for example, or standing waves as in a microwave. --Stephan Schulz (talk) 10:38, 8 January 2009 (UTC)

I like it! Proof of the wave nature of light using chocolate: [37]. SteveBaker (talk) 19:28, 8 January 2009 (UTC)

Light is very different from water or sound or other kinds of waves. It's not correct to say that light "is a wave" - we should say rather that "under some circumstances it behaves like a wave". Ditto for particles. Photons are definitely not "normal" particles. But it's certainly not as simple as photons (particles) wobbling up and down...that's a bad image to have in your head. Why is this bad? Well, it's just not how things are.

The 'wave/particle' duality thing is best demonstrated in the double-slit experiment (which we described and discussed a few questions ago). If you take a water 'wave-tank' and make a ripple pass through two slits in a wall of some kind - then the ripples that spread out on the other side of the wall will 'interfere' with each other. As the peak of one ripple crosses the peak of another - they add together to make a double-sized ripple - and where the peak of one ripple crosses the trough of another, they cancel out and leave calm water. This produces an "interference" pattern of radial lines that is quite distinctive. Soundwaves can be made to do the same thing.

So if light "is a wave" we should be able to do the same thing. So we take a sheet of glass - paint it black and score two very thin lines into it that are very close together. Then we can shine a source of light at the glass and look for interference patterns. If you do that experiment - you get interference patterns that look EXACTLY like the ones you got from your water tank experiments. Hence (you conclude) "light is a wave"! Hooray! Problem solved - right? Nah...not that easy.

Along comes that nice Mr Einstein. He observes experiments on what is called "the photoelectric effect". This is a situation where you have something like a solar-cell and you shine light on it and look at the electricity that comes out. Let me quote from our article photoelectric effect:

"Eduard Anton von Lenard observed that the energy of individual emitted electrons increased with the frequency, or color, of the light. This was at odds with James Clerk Maxwell's wave theory of light, which predicted that the electron energy would be proportional to the intensity of the radiation. In 1905, Einstein solved this paradox by describing light as composed of discrete quanta, now called photons, rather than continuous waves."

So this experiment can ONLY be explained if light is a bunch of little particles. So "light is particles"! Hooray! Problem solved right? Nah...not that easy.

We've still got to explain the double-slit experiment. We have double-slit which says "wave" and photoelectric-effect which says "particle". They can't both be right can they? ...Well, sadly, yes they can. But it gets weirder. You want to take the red pill and see where this rabbit-hole leads? OK.

So - someone has the bright idea to put the two experiments together. We take our double slit and we shoot single photons at it...if the particle theory is correct then the photon goes EITHER through the left slit OR the right slit - and so it can't interfere with itself...right? Nah...'fraid not. Even if you shoot a SINGLE photon at the double-slit, you STILL get interference. So the photon must be acting like a wave and going through BOTH slits. OK - but we can use the photoelectric effect to build a detector for single photons. When the photon hits the solar panel, we can look at the electricity it produces. So let's build a 'photon counter' and stick one behind each of the two slits. If the photon is a wave that's going through both slits then we'll count "half a photon" in each detector - right? Nah...sorry. Wrong again.

This is where things get SERIOUSLY weird.

When you try to count the number of photons going through each slit - you find that it behaves just like a particle and either one or the other photon counters kicks in. You know which slit the photon went through - for sure. So how come it's interfering with itself if it didn't go through the other slit? Well - guess what: When you set up the experiment to count the photons - the interference pattern disappears - as if by magic. This is deeply - DEEPLY strange. When you decide to try to treat the light as particles - it somehow magically KNOWS that you're trying to do that - and obligingly behaves like particles. It's wave-like properties disappear BECAUSE OF THE WAY YOU ARE MEASURING THE RESULTS. If you switch off your photon counters - the interference pattern obligingly comes back.

My head hurts - and so should yours.

At the quantum level where photons and such like play - the universe simply doesn't behave the way 'common sense' says it should. Our brains are simply not equipped to understand this. So - light is a..."something"...that behaves like a wave when we try to treat it as a wave and like a particle if we do that instead. Try not to rationalise this as a particle that's moving in a wavelike manner because that doesn't explain the double-slit experiment at all. A particle that wobbled like a duck on a pond as a ripple goes by wouldn't be able to go through both of the slits in the double-slit experiment...so it doesn't help.

Sadly, there is no simple thing you can hold in your head that explains what a photon is.

When you get into relativity, light is even weirder. It's the only thing in the universe that can travel at the speed of light. Anything else that tried to do that would have infinite mass and time for it would literally stop...photons don't seem to be bothered by that at all. They have perfectly sensible masses and they behave quite sensibly at that speed.

SteveBaker (talk) 14:56, 8 January 2009 (UTC)

Maybe time for photons does literally stop, sort of like the opposite of someone falling past an event horizon. For an outside observer the guy slows down until he's going imperceptibly slow and finally freezes and fades. But the guy just experiences himself falling a bit and getting stretched to death. Maybe photons don't have any perception of time, but when you watch them you don't see that weird effect at all. Maybe that explains some of the weird quantum EM effects. Just a thought.. Pez00 (talk) 18:28, 8 January 2009 (UTC)

Gravity also travels as fast as light. Light technically only refers to a certain spectrum of electromagnetic waves, all of which move at the speed of light. The stuff you mentioned before relativity applies to everything. I've heard the double-slit experiment has been done with buckyballs. Pez, you can't plug the speed of light into the relativistic equations. You could get it to work with limits, though. — DanielLC 19:53, 8 January 2009 (UTC)

It's -> Its

Wrong, SteveBaker, the fotoelèctric effect finds the fotòn is a—a—wave. Rather, it's the elèctròn and its associated transition thas is the mote. The same goes for the two-slit experiment: The elèctròn, whose inner size is the classic radius and outter size is its causal radius (by propagation—that is, its field) inducts the charges in the whole target and both slits, in the same way your finger can strike two keys on a keyboard, and reaches a path between the slits. It's not a wave by itself; its wave is the fotòn. -lysdexia 21:27, 8 January 2009 (UTC) —Preceding unsigned comment added by 69.108.164.45 (talk)

I'm sorry - but the photoelectric effect article (which I quoted directly) says otherwise. Here is the quote again:

"Eduard Anton von Lenard observed that the energy of individual emitted electrons increased with the frequency, or color, of the light. This was at odds with James Clerk Maxwell's wave theory of light, which predicted that the electron energy would be proportional to the intensity of the radiation. In 1905, Einstein solved this paradox by describing light as composed of discrete quanta, now called photons, rather than continuous waves."

If you think that's incorrect and can provide references to prove it - then you should go to the photoelectric effect article's Talk: page and argue it there. However, I'm very sure that you're wrong. SteveBaker (talk) 00:14, 9 January 2009 (UTC)

if an acid is added to a salt...?

what would happen to a salt if an acid is added to it? —Preceding unsigned comment added by 121.96.121.79 (talk) 10:41, 8 January 2009 (UTC)

I'm pretty sure it would depend on what acid and what salt. Nil Einne (talk) 11:59, 8 January 2009 (UTC)

The rule from high-school chemistry is "Acid + Alkali = Salt + Water"...salt is the end result of a reaction with acid - so it's hardly going to react with the acid further. So GENERALLY - nothing. However, there are a lot of exotic chemicals that we call "salts" and a lot more that we call "acids" - and that leaves open the possibility for all sorts of exciting reactions in the right combinations. Basically, we're going to need a lot more information. SteveBaker (talk) 14:28, 8 January 2009 (UTC)

You're missing a key ingredient:

Dilute acetic acid plus sodium chloride plus tuberous starch sections (hot) equals Delicious!

On a more serious note, SteveBaker and Nil Einne are quite right — we need more information. In the example above (without the fries), mixing acetic acid and sodium chloride (an acid and a salt, respectively) has no particular effect. On the other hand, mix acetic acid (vinegar) with sodium bicarbonate (baking soda), and you get the carbon dioxide bubbles which feature in every kid's science fair volcano.

And it gets worse — depending on how you choose to define 'acid', you can fit a vast number of reactions under the 'salt plus acid' umbrella. Using the Brønsted or Lewis definitions of an acid, many 'salts' are 'acids'. TenOfAllTrades(talk) 15:00, 8 January 2009 (UTC)

Mensa and god

I recently encountered someone who was a member of Mensa who also believed in god. Why would an otherwise intelligent person believe in supernatural beings? Surely, this person is smart enough to know better. But obviously isn't. This seems to be a paradox. Is it a question of emotion versus logic? Or intelligence versus knowledge? How is this possible? 216.239.234.196 (talk) 15:09, 8 January 2009 (UTC)

The only criterion for membership in Mensa is a high IQ, so the question is how well IQ correlates with a realistic world view. I think that even if IQ was a measure of a person's ability to cope with reality, 132 would not be good enough to get you clean over the god hump. But it isn't. IQ, that is. A measure of that. Sophistication, I've heard it called—nothing much to do with a problem-solving, mathematical intelligence. And your nerdy genius types are often colossal crackpots. Take Feynman with his goddam bongoes. --Milkbreath (talk) 15:52, 8 January 2009 (UTC)

IQ is a measure of ability to do IQ tests, nothing more. There is a correlation between that and intelligence, but it isn't particularly strong. However, you do get otherwise intelligent people believing in god(s), I think it's a matter of them being capable of reasoned decision making but choosing not to do so in the case of their religious beliefs - religion is all about not questioning what you've been told. --Tango (talk) 15:56, 8 January 2009 (UTC)

You said "There is a correlation between that and intelligence but it isn't particularly strong." You really need to define "intelligence" better before you make claims like that. All tests test only what the test tests. That's nearly a tautology and hardly even worth mentioning. If you say there's a correlation to "intelligence", but it isn't very strong, then you must be comparing IQ results to some other measure of intelligence. Unless you explain what that is, your statement has no meaning.

I know you're only saying what many, many others have said before (Some with modesty, others with sour grapes), but that's no excuse on the reference desk. APL (talk) 16:20, 8 January 2009 (UTC)

It's a fair point. Can I get away with saying "any reasonable definition of intelligence"? (Reasonable is, as always, defined as something I agree with. ;)) The problem is that intelligence (in the sense that the word is commonly used to mean, which is the only real definition of any word) isn't really quantifiable. It's a measure of collection of abilities and any weighting of them to get a single number is going to be completely arbitrary. Exactly what it means for a numerical measure to be correlated (however weakly) with something unquantifiable, I'm not sure, but I think everyone knows what I mean (the various abilities we include in intelligence are correlated themselves, so you can often at least put people into bands, even if you can't give them a precise number, there will be people that don't fit in any band, though - such discrepancies are often associated with learning difficulties). Incidentally, tests do generally measure more than just what they test - we interpret the results of the test in order to draw more useful conclusions. For example, a reading test tests whether or not someone can read a given bit of text, but what it measures is how good they are at reading in general (it doesn't measure this perfectly, of course). In order for a test to be used to measure something more than just what is actually being tested there needs to be a strong correlation between the two things - the ability to read a given sentence and the ability to read other similar sentences are very strongly correlated, so reading tests are useful. Similarly, the existence of a particular bacteria in a blood sample is strongly correlated with the existence of that bacteria in the rest of the person's blood, so we use tests on blood samples to measure things about the blood in general. The ability to solve the extremely obscure questions in an IQ test isn't strongly correlated to anything particularly useful. --Tango (talk) 16:43, 8 January 2009 (UTC)

a bacterium. "whether or not" means "whether or not whether". Someone is not a they. -lysdexia

"a bacteria" is commonly used to mean "a species of bacteria", "bacterium" refers to a single cell. I don't understand your second point. The use of "they" as a gender-neutral 3rd person singular pronoun is very widespread. The English language is defined simply by how people use it, so it being widespread means it is, by definition, correct. In future, if you don't have a refutation for someone's arguments, keep quiet, don't pick holes in their English - and if you are going to, at least do it right. --Tango (talk) 21:04, 8 January 2009 (UTC)

This question is based on the assumption that there is proof that God does not exist. In order to ask this question (without being a simple troll), the questioner must provide the proof that God does not exist, which all intelligent people must know, and this otherwise intelligent person is ignoring. -- kainaw™ 16:27, 8 January 2009 (UTC)

There is no proof of the non-existence of some kind of god and never will be since it isn't a mathematical statement, so a mathematical concept like "proof" is irrelevant. However, intelligent people generally draw conclusions about reality based on evidence, and there is no evidence of the existence of any kind of deity. obligatory link to Occam's razor --Tango (talk) 16:52, 8 January 2009 (UTC)

The proof

There is nothing which cannot be described by maths and loghics—so there can be such a proof; otherwise, one could not bring up the whim of "God" in the first stead, or contrast one God with another God, say what God is and is not or has and has not. God must be supernatural and infinite. However, the world and everything is natural and finite—otherwise, it would be God—so World and God cannot meet; that is, be in the same univers. By definition, if the world is natural it must make itself; otherwise, there would be nothing different between creation and creator as the former would also be supernatural and indistinguabil from God. As we cannot know God, there is no God and the world has nothing to do with God. The three kinds of god—theotèt (of theism, lord god), deotèt (of "deism", "god"), and pantheotèt (of pantheism, heaven-and-earth god)—with a mind informed of their proper meanings, can be stripped of their god-name for the first and last kinds and relegated intom natural and modern terms. The other kind left has nothing to do with mest of the world's sense or belief about God, so if god=God, god is everyways proven not.

I'll go with the others and say belief in God is dependent on ineducation—or more exactly, a miseducation of everything they believe in, which is mostly a monotheistic coverup of pollatheistic pagan roots. Their scriptures are ripoffs of Sumerian-Babilum creation and disaster stories, along with their misunderstandings of the size, scale, and shape of the world; whenever the Tanac or Vivli says something is true of the whole world or earth, it is wrong. Both texts (the Vedas too) like to blow up the lifetimes of their first men by some factor—12 or 60 or 360—by a spuriose reckoning of the year-day relationship as godly bodies rather than "heavenly" bodies. Every monotheism in order to please the old world makes up many Gods of their own, between five and eiht by my count, which are in sooth accessories of God but which they call servants of God, but which are nonetheless heavenly beings with God-like powers who pull off the same functions as the older pagan Gods. Kristianity, by exemplar, has pneýma, Immanuel, Ghabriel, logho, Mikael, basileia, and decsio—and the other Abrahamic religions hav variations of such, all in exact correlation with their pagan Gods, which I count fivefold (without the sun and moon) to sevenfold (with the sky and heaven). I'm about to finish a treatise against Creation and Creationists, with such a master list of Gods and other details against Ghenesis. My earlier writings can be found at Google Groups and Beliefnet, and some of the links are also where I proved, manifold, how there are no black holes. (Hint: The black hole is not a relativistic hýpothesis, but a classic and Newtonian one.) -lysdexia 20:09, 8 January 2009 (UTC)

All mathematical theorems are of the form "A implies B". "There is a god." is not of that form, so cannot be a mathematical theorem (I guess you could try "We observe the universe as we do, therefore there is a god.", but I don't see how you could translate that usefully into something you can do mathematics with). The existence of a god is a matter for theology, mathematics doesn't come into it (science can impose restrictions on what kinds of gods are likely to exist by finding evidence which contradicts the relevant religion, but you can't contradict the whole concept of religion). --Tango (talk) 21:15, 8 January 2009 (UTC)

There had already been a mathematic proof for God with transfinite sets in extrapolation—which faild, as it would expect any nominally trivial being. Likewise, one can use the same sets as a mathematic proof against God. -lysdexia 23:45, 8 January 2009 (UTC) —Preceding unsigned comment added by 69.108.164.45 (talk)

Intelligent people can also draw conclusions such as: We do not know what happens after death. If there is no God and you do do not believe in God, that is fine. If there is no God and you do believe in God, no real problem. If there is a God and you do not believe in God, you may be punished in whatever happens after death. If there is a God and you believe in God, you may be rewarded in whatever happens after death. How is that less intelligent than "I ain't seen nun'it so's I ain't believin' nun'it!" -- kainaw™ 17:15, 8 January 2009 (UTC)

Pascal's Wager is not exactly new. It's also not valid for any number of reasons. But to add another angle: What you propose really is the 1984 approach. "Say that 2+2=5 or I'll hurt you". I refuse to worship a god who needs such crude methods (and believing without worshiping is typically worse than not believing at all, of course). --Stephan Schulz (talk) 17:24, 8 January 2009 (UTC)

I'd say the main reason it isn't valid is that it seriously stretches the definition of "belief". In what way is such a conclusion a belief? It's just going along with it because it has the greatest expected outcome. I, too, would refuse to worship a God as megalomaniac and sadistic as the Christian God, even if I did believe in Him. --Tango (talk) 17:42, 8 January 2009 (UTC)

Pascal's wager is perfectly valid for the claim that I made. I stated that it is possible for an intelligent person to believe in God. Your response is that you refuse to believe in God. The point of this thread is not if you believe in God or not. The point of this thread is: Is it possible for an intelligent person to believe in God? Is your claim that you are the only intelligent person and, since you refuse to believe in God, no intelligent people believe in God? -- kainaw™ 17:41, 8 January 2009 (UTC)

• I would say that a person practising religion because of a decision based on Pascal's wager does not "believe in God". (And, do you really think someone that is meant to be omniscient would fool for such nonsense?) --Tango (talk) 17:58, 8 January 2009 (UTC)

• Why not? Those Sabbath mode ovens have been fooling Him for years.  :) --Sean 20:32, 8 January 2009 (UTC)

(And one of my favorite factoids: The bible is the most shop-lifted book in America...maybe people don't learn the "Thou shalt not steal" thing until AFTER they read it!) SteveBaker (talk) 22:05, 8 January 2009 (UTC)

• I have not claimed that it is impossible for an intelligent person to believe in god at all. On the contrary, I'm very much aware that many intelligent people do. Pope Benedict XVI would be a current example, as would be Kenneth R. Miller. For historical examples, Alhazen comes to mind, or Isaac Newton. But Pascal's Wager is not a good reason to do so. It assumes, without any reason, a particular configuration of god or gods and the afterlive. Under that assumption (there is one god, and it will treat me better if I pretend to believe in it for the expected gain in the afterlive, and I pick the right god from the many possible ones to believe in), it is valid. But what if Thor is pissed off because I believe in that Christian upstart? Or what if god despises people who only believe in him for the pay-off? --Stephan Schulz (talk) 18:16, 8 January 2009 (UTC)

You can strategically pick your god :) Thor hitting you with his hammer or being reincarnated as a hamster can't possibly be as bad as hell. Pez00 (talk) 18:33, 8 January 2009 (UTC)

Have you ever hit your thumb while nailing down a board? But by your argument, I would have to pick the god or godess that will treat non-believers the worst. Kali, here I come! ;-) --Stephan Schulz (talk) 18:42, 8 January 2009 (UTC)

Don't fall into the trap of thinking that religion is only worthwhile as an answer to the 'unknown', and that as science progresses and uncovers these secrets that religion becomes less and less worthwhile. Religion isn't like that in practice - it may be a cultural tradition, it might be a philosophy or guide for a person, it might be of comfort to them, or make them feel self-worth/purpose in life. Intelligent people are not devoid of wanting things that religion provides, and the fact that they are 'intelligent' enough to realise their belief isn't founded in perfect logic/scientific truth doesn't prevent them getting value from practicing their religion. The pursuit of knowledge and the pursuit of happiness are different things. Additionally we are not 'logical' beings, we can happily exist with giant contradictions and we fool ourselves into believing something that to every outside is blatently lies. Finally just to note - i'm not religious in any way, but try to appreciate that the 'truth' isn't necessarily what's right/important. 194.221.133.226 (talk) 16:43, 8 January 2009 (UTC)

I think you're confusing the issue here. The OP specifically asked why an intelligent person may believe in God. Not why an intelligent person may be religious. You can and many people do participate in religious ceremonies or religion for cultural reason, as a guide etc. However while it may be more likely that such people will believe in God, it's not a precondition and many people don't Nil Einne (talk) 18:52, 8 January 2009 (UTC)

To be honest, I think I may have confused the issue, too. I did not consider that there can be a distinction between being religious and believing in god. I don't suppose you know of any articles about people who are religious but don't believe in god? 216.239.234.196 (talk) 19:08, 8 January 2009 (UTC)

Take a look at cultural Judaism for starters. These include people who may be involved in religious ceremonies and practices for cultural reasons, without actually believing in God. Indeed there are even ancient religions e.g. Buddhism which don't even have the concept of God. And new ones are cropping up e.g. Unitarian Universalism and other Liberal religions have no defined God (although some people involved in them obviously do believe in God) and many of the new age religions lack God. For those who do like the sense of community etc given by religion but who don't believe in God, as churches and the like are appearing [38] [39] [40] [41]. Douglas Adams a self described radical atheist, funeral was held in a Christian church with Dawkins in attendance. Parents sometimes attend church to give their children a change to explore religion or because they believe it's beneficial in other ways but don't believe in God themselves [42]. I've tried to avoid referring to these people as religions since whether you consider these people religious or not is an unnecessary distraction. I would say many are religious e.g. Buddhists, those involved in new age religions etc i.e. all of those with a sense of spirituality are religious, even though they may not believe in God. Indeed you could go further since it appears to me the OP was specifically asking about the Abrahamic monotheism concept which most Eastern religions lack. Of course you could argue that many of the spritual religious beliefs have the same problem as the concept of God and therefore it makes as much or little sense for an intelligent person to believe in them but I don't think it's a simple matter. To me, the idea of an omnipotent being (particularly one who punishes the 'wicked' for enternity although that's obviously not a precondition for believing in God) makes less sense then the idea we are all connected on a spiritual level. Then there are also those without any spirituality, i.e. do it solely for the sense of community, moral guidance etc who you could probably say are not religios but they still "participate in religious ceremonies or religion for cultural reason, as a guide etc" as I stated even though they obviously don't believe in God. P.S. You may want to ake a look at religion. Nil Einne (talk) 10:26, 9 January 2009 (UTC)

At my church we have professionals is many, many areas including biologists, chemists, physicists, doctors and surgeons, lawyers, architects, engineers etc. All these areas require intelligence, logical thinking and the like. Whatever their/my personal reasons may be, religious beliefs have very little correlation with intelligence in my honest opinion. As the IP above me has noted, it's not always in a search of God and the paranormal, its often a cultural reference in how to live in a generally accepted better way (with a few nutjobs taking it too far). —Cyclonenim (talk · contribs · email) 17:23, 8 January 2009 (UTC)

You can have a sense of morality without being religious. What does visiting a given building every 7th day and worshipping a mythical figure have to do with living in a "generally accepted better way"? There have been studies which have shown a significant correlation between level of education and religious belief (the higher the level of education you've achieved, the less likely you are to be religious) - you can argue than education and intelligence are not the same thing (and you would be right, of course), but your examples are all of highly educated people, so such studies are relevant. --Tango (talk) 17:42, 8 January 2009 (UTC)

There are also studies that show that older people tend to be more religious. So, can we safely assume that religion is a product of age and life experience? Is there a correlation between age and education? Do these correlations have no cause-effect relationship? -- kainaw™ 17:46, 8 January 2009 (UTC)

Unless such studies have been repeated at different times, you need to be very careful what conclusions you draw from them. It could well be when you are born that is significant, not how old you are. --Tango (talk) 18:00, 8 January 2009 (UTC)

@Tango, sorry I didn't mean imply that only religious people can me moral. I'm saying that almost all religious people are, it's an almost ensured way of living morally. It's not going to church and worshipping a God as such which has anything to do with living your life a better way, it's adapting to the guidelines given in religious texts (of which many are now bound socially as well as religiously). How do such studies as you mentioned above help discourage my point? The vast majority of adults at my church are well educated and successful, and still religious. Studies based on religous belief and education is essentially like going and doing a survey of "Are you religious?" at an educational establishment. —Cyclonenim (talk · contribs · email) 18:13, 8 January 2009 (UTC)

Sorry, but being religious does not seem to increase your chance of living a moral life. For one, many religious demands are outright immoral ("stone the witch!"), but also, believing in a religion does not at all imply that you follow the moral rules of that religion at all. "We are all sinners..." --Stephan Schulz (talk) 18:38, 8 January 2009 (UTC)

Two things. First as I noted above, being religious and following religious guidelines doesn't require you to believe in God which is the real question at hand. As also noted above, many people can and do do so without believing in God. Technically the guidelines may require you to believe in God but people can and do choose to ignore that part as nonsense in their opinion. Second I think many would argue the guidelines have been bound socially long before they appeared in religios. They would say the reason they appeared in religious texts is because of the social tradition Nil Einne (talk) 18:58, 8 January 2009 (UTC) Edit: Struck out being religios to avoid confusion Nil Einne (talk) 10:26, 9 January 2009 (UTC)

Intelligent people can usually understand that there are things that logic and science can't deal with. Do you believe in beauty? Science cannot really measure that sort of thing and logic can't prove it exists. With no available evidence for or against, belief in god(s) is more or less a matter of personal taste. I don't think you can particularly draw conclusions about intelligence based on the god question. Friday (talk) 17:50, 8 January 2009 (UTC)

There's a lot of defense you can throw behind the idea that a god exists, but a better question would be which religion do you believe in? Christianity? Try to reconcile all we know about the age of the universe and the earth with a recent creation and a god who "is not the author of confusion". Scientology? Perhaps the most relevant example; reason screams against their doctrine Pez00 (talk) 18:18, 8 January 2009 (UTC)

To be fair, it's only a small radical fringe of Christians who believe in a young Earth. Friday (talk) 18:22, 8 January 2009 (UTC)

Personally I'm not altogether happy that I think all that God stuff is rubbish. I know the statistics show that religion is correlated with wealth happiness, and more children. I feel like the person who was offered great health, wealth or wisdom by a genii and asked for the wisdom, and a moment later says 'Oh I see now I should have asked for the wealth' :) Dmcq (talk) 18:34, 8 January 2009 (UTC)

Correlation != causation. You are assuming that wealth comes about BECAUSE of religion - but how do you know it's not the other way around? People with a lot of money on their hands have nothing better to do maybe? Correlation with more children has GOT to be because so many religions encourage more children (eg by making women subsurvient to men - or by banning condoms). Without studies into causation - these statistics don't tell you a whole lot...it's possible for example...that like US politicians, you're doomed to becoming a social outcast in wealthy society unless you tell people that you are religious. So everyone lies. It's possible that in the past there was causation - and because children of religious parents tend to be religious - and children of wealthy parents tend to be wealthy - the statistical 'ghost' of that causation lives on. We simply don't know. Suffice to say that I consider myself reasonably well off - and I'm a total atheist. I only have one child - but family size correlates inversely with wealth - so we can't make any conclusions about that. SteveBaker (talk) 19:41, 8 January 2009 (UTC)

Believe it or not - we have an article on the subject: Religiosity and intelligence - broadly speaking the percentage of religious people does go down with increasing intelligence - more or less independently of how "intelligence" is defined. (eg IQ or educational achievement or job title) - however, almost every statistical test you apply comes out like a bell-curve - so it's no surprise that even in people with the highest IQ - there are a few who buck the trend. Mensa's requirements for entry really aren't that great - and it's rather well established that you can pass their test even if your initial IQ is too low simply by practicing a lot. Since practicing IQ tests doesn't really shake your religious beliefs to their very core - we may conclude that this is all very unsurprising. IQ tests really only measure how good you are at IQ tests. Some very smart people (Einstein comes to mind) are very incapable at getting through their daily lives - a narrow intelligence is a very different thing from a broad one. However, it is still mostly true to say that in general...statistically speaking...smart people are less likely to believe in God. There is a reason for that. SteveBaker (talk) 18:57, 8 January 2009 (UTC)

There is a lot of discussion about Pascal's wager here. This needs to be shot down in flames. It suffers from what I'm now going to be calling "The Pink Aardvark Gambit^(tm)". I have decided to believe that giant Pink Aardvarks with terrifying levels of technology are ruling the universe and if you don't pray to them every day (using telepathic thought projection) - they do horrible things to you after you're dead. It's a new religion - I just made it up. I have no evidence for it - but a part of it is that all believers have to send $10 to the Wikimedia foundation in order to supplicate the holy Aardvarks. You seem skeptical...

But if I merely apply Pascal's wager - magically, it's all true. If there are no Pink Aardvarks, it costs you almost nothing to pray to them redundantly - if there are then it's going to save you an infinite amount of torment in the after-life. Multiply the probability of their existance by the cost of praying to them and the result is non-zero - multiply the cost of torment for a day by an infinite number of days and the result is infinite.

...and with a brief *POP* of logic - everyone must now believe in my Aardvarks. So are all you religious nuts now believing in Aardvarks? No? What happened to this claim that Pascals Wager is worth a damn? You guys seem to have changed your mind.

The problem is that the wager assumes you are betting only on one very special thing (the existance of a very specific Christian deity). But a mathematician isn't going to let you get away with that. You have to apply a rule like that to everything to which it's relevant. So my Pink Aardvarks, the Invisible Pink Unicorn the Flying Spaghetti Monster, ever OTHER religion on the planet - and every conceivable concept like that - including a bunch we haven't thought of yet. When you do that, you multiply the 'cost of believing' number by the number of things you might have to believe in. Now, the wager doesn't look so good. You have an infinite personal belief "cost" balanced against an infinite "penalty" if any one of those things might happen to be true. So Pascal's wager says that you either need to spend 100% of your existance in a dedicated effort to believe and supplicate every concievable crazy religion - or you've got to say "screw it" and get on with your life without god or gods or unfalsifiable beliefs of ANY kind. Rational people take the latter - stupid people go and ask a priest who doesn't know much math and is perfectly prepared to lie to you in order to keep his job.

SteveBaker (talk) 19:22, 8 January 2009 (UTC)

Hey, that's pretty good. Can you get that published by a reliable source so we can include it in the Pascal's Wager article. 216.239.234.196 (talk) 20:21, 8 January 2009 (UTC)

I don't have a cite off hand, but I believe that Pascal had previous, less famous, proofs that the christian god was the only possible god that offers infinite bliss. (And in a wager of this sort, infinite bliss trumps all other forms of reward.) If you accepted that, Pascal's wager would suddenly seem a lot more attractive.

In any case it's a good answer to the original question. He was clearly an intelligent person who believed in god. APL (talk) 21:07, 8 January 2009 (UTC)

Tribes and nations everywhere on earth have always had some sort of god or gods. There has been only a very few exceptions. These exceptions were in tribes that had a very low level of general civilization – they lived little better than animals and ignored inner religious promptings. However, as the human race evolved from an earlier type of anthropoid, it developed a dim understanding or feeling that there is a higher being or beings. It could be called a hunch. But it was a powerful hunch that appeared in all parts of the world before there was contact between the people in different places. From that hunch, specific gods were created. There was also a desire to relate to these gods by worship. Most early religions were terror religions which inspired fear. In ancient Egypt, for instance, the gods took the form of grotesque animals which could not be regarded with any feeling of worshipful friendship or personal closeness. But as time went by, there seems to have been a sort of evolutionary development in religious understanding. Religious views that seemed more suitable, more true, were adopted. The multiple gods were replaced with a single god. The concept developed that this one god was a beneficent god. Furthermore, this god was not just beneficent toward human beings, he also wanted humans to be good to each other. ("Love ye one another.") In some cases, rather than a religion developing gradually, it was abandoned when a more suitable religion was introduced by missionaries or conquerors. This happened with Christianity and Islam. In a further evolutionary development, Christianity abandoned the concept of Hell and damnation by ignoring those concepts. The evolution of religious understanding may be likened to a lesser concept – the development of typography. Many forms of typeface have been designed, and there was the question of which was easiest to read. Tests were made in which people were given texts in various typefaces and asked which was easier to read. The readers' opinions varied somewhat, but the general consensus was that Times New Roman, and some fonts very similar to it, were the best typeface for ease of reading. So it has been with religion. Down through the ages, countless millions of people have considered religion. Most of these persons simply accepted what they had been taught. But there were a few persons who developed new major or minor viewpoints on religion. Their views were considered by others, and were either adopted as being better, or discarded as being useless, harmful, or wrong. (Fundamentalists rejected all change. Thus, they do not allow religious evolution.) Abandoning the concept of Hell is an example of a major evolutionary development that has, in effect been adopted. Thus, while there is no proof that God exists, the concept of the evolutionary development of religion offers intelligent persons a way to accept a current interpretation and manifestation of the near-universal hunch that God does exist. – GlowWorm —Preceding unsigned comment added by 174.130.253.174 (talk) 20:47, 8 January 2009 (UTC)

A shorthand for what you are saying is that religion is a 'meme' - an idea that spreads itself much like a gene does. Memes reproduce (for example when I tell you a joke and you tell the joke to someone else) - and they evolve (someone tweaks the wording of the joke to make it a bit funnier - or changes "polish guy" to "irish guy" to better fit the times). In short, they work just like genes do. Things like "money" and "rock music" are memes - and so is religion. Thinking of it like that is instructive because it lets us consider analogies. Successful memes outlast unsuccessful ones. But note that a meme doesn't have to be a truth in order to be popular - it just has to be something that someone will tell someone else. Hence we get all sorts of Internet memes that turn out to be hoaxes - but if they are funny or amazing they become more popular than truth and they are VERY tough to kill.

The reason (I believe) that religion has shown up in so many cultures - possibly by "parallel evolution" - is that they have acquire power. If someone in a primitive atheistic village gets the idea that because an Aardvark stole his shoe - and that year his crops did better than his neighbour that maybe if he leaves a shoe next to the anthill then maybe his crops will do better the following year. He does this and there is maybe a 50/50 chance that it works. If it DOES work - then he'll tell everyone else and they'll all do it. If the crops are good the following year (again, by chance) then everyone believes that this guy has found the answer to why crops mysteriously fail sometimes. But he's a clever guy and he realises that he can make a killing here. He says "Well, actually - the Aardvark spoke to me and said that I'm the chosen one and I have to deliver the shoes to the anthill every month."...now you have a high-priest - his power will grow he can give up farming - when people's crops fail despite the offering of shoes to the Aardvark he makes up excuses ("Oh - did you forget to turn around three times before you came to me with the shoe?") large books will be written about the precise protocol - acolytes will flock to him because they have the possibility to sit around in the big comfy temple without working. Before you know it - it's everywhere and they own their own cable TV channel and have people with Aardvark badges on their lapels demanding donations outside shopping malls throughout the holy month of March. The fact that the meme builds itself from a series of coincidences is enough to ensure that sooner or later every civilisation is going to get infected by one. The very process of evolution is (ironically) what polishes and perfects the meme over the generations. Meme's that attract followers and money and respect grow in popularity - religions that are a pain to deal with fizzle out. Natural selection at work.

SteveBaker (talk) 21:56, 8 January 2009 (UTC)

lysdexia's first assertion that everything can be described by maths and logic is false. Gödel's incompleteness theorems. At the first hurdle! —Preceding unsigned comment added by 92.16.196.156 (talk) 00:22, 9 January 2009 (UTC)

Be REALLY careful around Godel's theorem. It's a bomb that'll take off your head if you aren't careful with it! It DOES NOT SAY that math and logic don't work or that they don't have descriptive power. It says that there exist some theorems that can neither be proved nor disproved. No all theorems - not even most theorems..."some". It also doesn't say that mathematics somehow "goes wrong" and produces the "wrong answers". What happens is that there are circumstances where math doesn't have an answer - not that an incorrect answer is produced. But Godel's work has to be taken alongside such things as the Church-Turing hypothesis which asserts the equivalence of essentially all logical systems. Godels theorem actually says that ANY system of thought that has enough power to describe things in a reasonably powerful manner will suffer the exact same problems. That means that your brain can't solve these problems in ANY manner - the things that Godel says can't be proven by math can't be solved by other means either. SteveBaker (talk) 05:38, 9 January 2009 (UTC)

False dichotomy

See the work of the late Harvard University evolutionary biologist Stephen Jay Gould, especially Rocks of Ages. Saying that having a strong background and understanding of science and mathematics, or even of being "intelligent", is somehow mutually exclusive is a false dichotomy. Its like saying "You cannot like apple pie and drive a motorcycle". Science and religion do not have to serve the same purpose in a person's life. It is entirely reasonable, for example, to fully understand and accept the tenets of evolution, cosmogonic physics, and every single commonly accpeted scientific fact, and yet science for many people does not answer the questions of purpose and being and the entire field of Ontology. Science explains the mechanistic aspects of the world quite well, but it does not answer the questions such as "Why are we here?" Even if the answer to that question for you is "There is absolutely no reason at all.", science cannot even begin to answer that question. There are many people for whom the answers to those questions are different than that.

Look at it another way. I can take apart a beautiful and intricately made watch. I can understand fully how the watch is made, I can study and understand every part and every working and movement of the watch, take it apart, put it together again, etc. etc. Such understanding of the workings of the watch, however, in no way proves that the watchmaker does not exist, or that the watch arose spontaneously. Understanding the details of creation to the most exacting detail does not disprove the creator. Neither does it prove the creator. You must arrive at your belief in a creator, or in a belief in a spontaneous universe, entirely by faith. Having a different focus of that faith (either in God or in his non-existance) is in no way connected to intelligence or scientific understanding, or anything else except your own personal faith. --Jayron32.talk.contribs 00:52, 9 January 2009 (UTC)

I don't see a dichotomy here at all. What you are talking about is the concept of non-overlapping magisteria. One problem with this is that many religions do make claims about the physical universe, and thus the different realms of science and religion do overlap in practice. --Stephan Schulz (talk) 01:01, 9 January 2009 (UTC)

However, the initial question did not ask about the tenets of a specific religion, or even about how a personal belief in religion which can work with an understanding of science. Rather, the question asked about a rather general belief in the existance of an intelligent creator, i.e. God. There is organized religion, and then there is personal religion. There is what has been written down and codified by people in the past, and then there is how people work the entire system into their own world view. My point is that it is not inconsistant to have a world view which both holds the existance of an intelligent creator (God) and which also fully understands the mechanisms of His creation. Any claims that these fields are somehow in conflict or mutually exclusive is themselves creating false conflict where there is none. A scientist who tells you that evolution and the big bang somehow proves there isn't a God (as opposed to disproving the literal explanation of creation in Genesis 1, which is entitely different) is committing the SAME falshood as a priest who tells you that if you believe in God, you must disbelieve evolution... --Jayron32.talk.contribs 13:15, 9 January 2009 (UTC)

Ignoring all this worthless bickering, here are some stats on Canadian MENSA religious beliefs compared to the general population. They seem to be less religious, but not to the degree that the AAAS is less religious (I can't find exact numbers but I remember them being very disproportionately non-religious.--droptone (talk) 13:30, 9 January 2009 (UTC)

Solar power for a house

My south facing house has an area of about 500 square feet of available space for solar panels. If I were to maximize the available area with soalr panels, what could I expect to "power" in my house? Undoubtedly, there are many variables, but I am wondering in general. Just my lights? Maybe lights and electronics? My hopes are too high? —Preceding unsigned comment added by 209.161.223.61 (talk) 15:43, 8 January 2009 (UTC)

What latitude do you live at and what is the weather like? And what time of year are you considering? Those are the key variables, I think, and they will make a massive difference. Under poor conditions, you'll get next to nothing, under good conditions you may be able to get several kilowatts, maybe even more, that will certainly power your lights. However, you would need batteries to store the energy until you need it (powering lights directly by solar power is rather pointless!), so power isn't the best measure, we need to look at total energy. If you're getting around 20 kilowatt-hours a day (which seems reasonable if you are somewhere pretty sunny and at a fairly low latitude), and you're pretty energy efficient, you might just about be able to power everything. You would need a connection to the national grid to make up the shortfall during winter or a few days of overcast (you can only have so many batteries), and also to sell any excess. (Note, these are all back of the envelope calculations with extremely approximate assumptions, but my conclusion is that, depending on where you live, you may well be able to make a significant contribution to your energy needs with 500 sq ft of solar panels. If you want something more precise than that, it will take more research and would require knowledge of your location.) --Tango (talk) 16:15, 8 January 2009 (UTC)

Also, consider to set aside something for a solar hot water and possibly heating system. These are typically better value for money and a more efficient use of solar power than solar electric systems. --Stephan Schulz (talk) 16:20, 8 January 2009 (UTC)

Thanks for the feedback. I live near Toronto, Ontario, Canada. I know that there are a lot of variables so would need to consult with a professional company to get an accurate measure. I wanted to get a general sense of things (which I now have!) —Preceding unsigned comment added by 69.77.185.91 (talk) 17:40, 8 January 2009 (UTC)

One major thing when you don't have that much strong sunlight is to try to get the solar panels to be as close to being at right angles to the sun's rays as possible for as much of the day as possible. As far North as Ontario, the sun is low enough in the sky that putting the panels on a vertical wall might make more sense than on a flat or sloping roof - a simple rule of thumb is that the amount of light you get varies as the cosine of the angle between the sun's rays and the direction the panel is pointing. If you are investing in a lot of panels, its worth considering some motor-driven means to track the sun across the sky. Everything moves very slowly so the motor can be geared down fairly dramatically and your motor can be small and energy efficient. SteveBaker (talk) 18:47, 8 January 2009 (UTC)

The earth's surface receives ~1 kW / m^2 in direct sunlight. If your system is say 15% efficient you could get as much 7500 W from 500 sq. ft. if the sun was directly above your installation (with no clouds or other impediments). The average 3 person American household uses a time averaged 400-700 W of electricity, so your peak production should be way more than you need for the entire house. Once you add in other factors (e.g. nightfall, cloudiness, latitude, etc.) your average power generation from solar would be much less than your peak possible, but with 500 sq ft of panels there is still a good chance you would make more electricity on average than your home can consume. If you are serious about pursuing this, you can get solar power companies to evaluate your location and give you a more rigorous estimate of what to expect. Dragons flight (talk) 21:42, 8 January 2009 (UTC)

You know, many people around the world are either using clean technology to power their homes and live off the grid, or for internal heating. Solar, wind, and corn are just some examples. There's also a store in Toronto called EfstonScience which is a passive solar building that uses solar for internal heating. The GTA doesn't get much sun in the winter, though, especially considering it's often cloudy (although sometimes it does snow under a clear sky). You need a way to store your power so it can be used later and at night. If you can make enough power, I believe there's also a way you can "sell" your power to the grid and earn money doing it. ~AH1^(TCU) 23:44, 8 January 2009 (UTC)

Temperature at which Magnesium ignites

At what temperature would a piece of magnesium ignite in air? (Magnesium says molten magnesium is highly flammable and gives the melting point of magnesium, but doesn't say it has to molten to ignite and doesn't say melting is sufficient.) RJFJR (talk) 16:17, 8 January 2009 (UTC)

No idea if this is what you're looking for, but Magnesium is listed at Autoignition_temperature#Autoignition_point_of_selected_substances. It's way below the melting point so I guess you have to melt it in partial vacuum to keep it from burning. Pez00 (talk) 18:20, 8 January 2009 (UTC)

Or, more easily, under an inert gas atmosphere, either a noble gas, or possibly something as cheap and abundant as Nitrogen. --Stephan Schulz (talk) 18:46, 8 January 2009 (UTC)

Not nitrogen--most active metals react with it and some even have specific warning labels about not using nitrogen atmosphere. See Magnesium nitride. DMacks (talk) 19:38, 8 January 2009 (UTC)

Thank you. That's what I was looking for but didn't know what to call that temperature. RJFJR (talk) 20:39, 8 January 2009 (UTC)

Colorlessness of a solution

I want to quantified how 'colored' a solution is, without regard to wavelength (within the visible range). The idea is that I am formulating a product for which the ideal is colorlessness; I'd like to be able to quantify how far from this ideal various versions of the product are, but ignoring that one might be a little green, and another might be a little red, etc.

The only idea I've had so far was to use a spectrophotometer to scan the entire visible range and integrate the area beneath the transmittance curve, and subtract this from the value that you'd get from 100% transmittance at all wavelengths. I'm afraid this is probably a little naive. Can you suggest a better way? I think I also have access to meters for getting Lab color space values, if that would be better. ike9898 (talk) 19:06, 8 January 2009 (UTC)

That will work, but you may have to correct for the visible range (if ambient light isn't equally intense across the spectrum, your result may get skewed by a strong absorbance at a wavelength that doesn't matter much practically. How about a white light (or a lightbulb, or something else corresponding to "what looks like broad-spectrum visible") and a similarly broad-spectrum (non-monochromator or filtered) PMT/photocell/photoresistor/etc? Still need to correct for visible-range, but at least you're starting with ambient-light spectral characteristics. You don't need the accuracy (I don't think?) of X decimal places at each wavelength, just the overall transmittance. DMacks (talk) 19:36, 8 January 2009 (UTC)

Any one have any more input? I'd like my method to be reasonably defensible when put into a paper. ike9898 (talk) 22:05, 8 January 2009 (UTC)

Do you want it to be colourless or transparent? They are different things. You seem to be describing transparency. --Tango (talk) 23:58, 8 January 2009 (UTC)

An important article dealing with this is the Beer–Lambert law, which describes the relationship between the intensity of a color in a solution to the properties of that solution. --Jayron32.talk.contribs 00:34, 9 January 2009 (UTC)

If you do choose to integrate over wavelengths, you should probably weigh the integration using the photopic Luminosity function. If the "application" of the transparency is not related to human vision (eg. it is for a light sensor), then the sensor's spectral response curve would be an appropriate weighing function. Weighing ensures that you don't have to pick arbitrary limits for what constitutes visible light - the weighing function will smoothly roll off into the limits of human/sensor vision. From an experimental standpoint, try to obtain the highest possible concentrations of your solutions, because measuring very small Absorbance is generally hard (unless you have good equipment). Someone42 (talk) 10:43, 9 January 2009 (UTC)

knotty problem

regarding entanglement on the quantum level, is there a limit to how many things can be entangled with each other? 86.155.28.235 (talk) 19:34, 8 January 2009 (UTC)

Not as far as the theory is concerned and not as far as anyone knows, but there is a limit on the extent to which entanglement has been tested. Quantum algorithms depend on entangled states more complicated than any that have been created experimentally so far, and one of the reasons for trying to build big quantum computers is as an experiment in basic physics, to see if the world can actually sustain that level of entanglement. -- BenRG (talk) 20:26, 8 January 2009 (UTC)

It is very likely that most of reality is entangled with itself, as all the particles now in existence have interacted with each other in the past. Graeme Bartlett (talk) 20:31, 8 January 2009 (UTC)

what would be the consequences of this? 86.155.28.235 (talk) 23:11, 8 January 2009 (UTC)

You could expect that any measurement made will affect the potential results from any other measurement, but in unknown ways. For example if you measure the speed of a particle it will affect the results of a speed measurement of another particle that collided with it in the past, or collided with a particle that it collided with earlier etc. I am sure there will be many more consequences, physical and philosophical that I am not aware of yet. Graeme Bartlett (talk) 01:20, 9 January 2009 (UTC)

This doesn't sound right to me. Entanglement is not one measurement affecting another (ignore the popular books claiming it is), it's just a statistical correlation that's stronger than is classically possible. We don't see such super-classical correlations in the world at large, only in carefully isolated systems (because of quantum decoherence). Different parts of the universe are similar in a way that suggests former interaction (e.g. the CMB is uniform), but that's classical correlation at most, and it's problematic to even call it that since you need multiple trials to establish a correlation and we've only got one universe. -- BenRG (talk) 06:55, 9 January 2009 (UTC)

A more used term is universal entanglement. This results in decoherence and is on way to explain how macroscopic reality is so different to the quantum experience. Graeme Bartlett (talk) 05:38, 9 January 2009 (UTC)

If the sun went out...

Assume the sun either disappears somehow or stops giving off all forms of radiation right now. If this happened(I realize there's hardly any way it could, but this is a hypothetical question) how long would it take for Earth to become uninhabitably cold? How long would it take for Earth to cool down to absolute zero? 69.224.37.48 (talk) 19:46, 8 January 2009 (UTC)

Uninhabitably? Difficult to say. Depending on the lengths to which humans are willing to go, it could take quite a while. Geothermal energy will continue to be useful for billions of years, most likely. That said, I'd guess that surface temperatures would plummet below freezing within a week (consider that temperature drops of 10-15°C overnight are common). For absolute zero, not until the heat death of the universe. Thanks to the cosmic background radiation, temperatures bottom out at about 3 Kelvin or so. — Lomn 19:52, 8 January 2009 (UTC)

We could probably support a small number of humans using geothermal energy (the remaining fossil fuels and tidal energy will also help), but given that all life outside of specially constructed biospheres would be dead it would be difficult to support a large number of humans - we would need to support an entire ecosystem as well to oxygenate the air and to provide food. I'm not sure how long we could support them for, though - as the Earth cools down the energy required to heat the biosphere increases and I'm not sure how cold the Earth would get and how quickly (uninhabitable without technological assistance within a year, certainly, since crops would all fail, but more than that, I don't know). --Tango (talk) 21:33, 8 January 2009 (UTC)

Land and air gets cold a lot faster than oceans because the mixing in the surface layers mean you have to remove heat from a substantial volume of water. In a previous reference desk thread it was estimated that it could take months for the tropical ocean to start freezing if you assume a typical 50 m mixed layer. Dragons flight (talk) 21:58, 8 January 2009 (UTC)

I don't feel like searching for that discussion (which I don't recall, so it may have been before my time), but I can try and repeat it (standard disclaimers about back of the envelope calculations apply). According to insolation (assuming I'm reading it correctly), a square metre of tropical ocean would receive an average of 250W from the Sun. Since the ocean doesn't change temperature much, we can assume it is losing that much too and would continue to do so if the sun went out (at first, anyway). For a 50m mixed layer, we need to cool 50m³ of water. The specific heat capacity of water is about 4 J cm⁻³ K⁻¹. Let's say the water starts off at 25C. That means we need to remove 4*25*50*1,000,000=5,000,000,000J. At 250W, that would take 20,000,000 seconds, or nearly 8 months. And that's just for it to start freezing, it would take longer for it to completely freeze. That's all very approximate, though. --Tango (talk) 23:41, 8 January 2009 (UTC)

I don't think it would drop to absolute zero, since the Earth has internal heat. Maybe geothermal heating could work for a while. ~AH1^(TCU) 23:32, 8 January 2009 (UTC)

As Lomn said, it wouldn't drop to absolute zero due to the CMB, geothermal would keep it well above even that 3K for billions of years, though. It would still be far too cold on the surface to support life as we know it pretty quickly (although the lack of light may be more deadly than the lack of heat). --Tango (talk) 23:56, 8 January 2009 (UTC)

The current geothermal heat flux of ~50 mW/m^2 would keep the surface at 30K if treated as a black body. Dragons flight (talk) 00:23, 9 January 2009 (UTC)

The other thing, and it has nothing to do with the Earth's internal heat, is that it will never drop to absolute zero (which is an asymptotic condition anyways) because the entire universe has an ambient temperature of roughly 2.725 K; so that is the theoretical lowest temperature that the earth could reach. In practical terms, the final temperature of the universe (and thus the lowest temperature the earth will reach) at the end of time will likely be higher than this, as the warmer parts of the universe will be slightly heating up the colder parts over time as well, so when the entire system equilibrates, it will fractionally higher... --Jayron32.talk.contribs 00:31, 9 January 2009 (UTC)

But the universe expands, which causes the CMB to red-shift over time, i.e. the energy density goes towards zero. Surprisingly, the time the Earth would need to cool down is quite long, even on a cosmological scale. I think we discussed this before. --Stephan Schulz (talk) 00:41, 9 January 2009 (UTC)

2.7 K is the current CMB temperature; it declines as the universe expands. In the limit of a flat universe, the CMB temperature (along with everything else) asymptotes to zero K. See also: Heat death of the universe. Dragons flight (talk) 00:40, 9 January 2009 (UTC)

Great minds... ;-). Does anybody else have the feeling that edit conflicts are now very often resolved automatically? DF's answer was not there when I started editing, and I got no conflict, either. --Stephan Schulz (talk) 00:44, 9 January 2009 (UTC)

Yes, I've noticed a lot of messages getting posted at almost the same time in the wrong order, which seems to be due to automatic resolution of edit conflicts. --Tango (talk) 00:47, 9 January 2009 (UTC)

As an engineer and a musician of sorts, I find the projected heat death of the universe depressing. If there is to be no practically exploitable difference of potential, and the universe is just a uniform, flat, cold, mucky bog at 3 K (or 2.7 K, or whatever K), no useful work could be done and there would be no need of engines or power transmission or power conversion. Thus there would be no need for engineers, even if life of some form existed. There might be a need for poets, or composers, to write dirges for what had once been, but there would be no means of performance. Edison (talk) 05:34, 9 January 2009 (UTC)

Thinking requires energy, so there can't even be poets. --Tango (talk) 12:41, 9 January 2009 (UTC)

Alcohol

Disclaimer: this is NOT asking for medical advice - merely trying to find the answer to an argument!

During a conversation the other day, the subject came up about a man who has given up beer and started drinking vodka instead - as vodka is apparantly less fattening. I thought the man was being quite ingenious in trying to lose weight as the fattening effects of beer are well known (hence the term "beer belly!") but my friend said it wasn't as apparantly spirits are much worse for the liver than beer. I argued that this was not the case as provided he drink the same number of units of alcohol, the effect on the liver would be no different...so here's the question.

1. Is say 8 units of alcohol drunk as vodka (about 200ml I think) any worse for the liver than 8 units of alcohol drunk as beer (about 4 pints of standard 4% ABV beer)? Obviously there are other factors at play that would affect how the alcohol is absorbed, such as the individual's body and how much they've eaten etc but assuming all other factors are the same?

2. Would the guy in question actually lose any weight by substituting beer for vodka? OK, silly question as obviously the answer would be no if (as I suspect in this case) said guy did little excercise and ate loads of junk food but if it was just the beer that was making him fat, would this actually work? I've never heard of that method of losing weight before. Beer presumably has loads of carbohydrates in it therefore loads of calories but I presume vodka would too? Alcohol is made from sugar isn't it and sugar is a form of carb?

Answers on a postcard (oh OK then, on here) please to settle this question! —Preceding unsigned comment added by 78.33.180.73 (talk) 19:59, 8 January 2009 (UTC)

I think one factor to consider is the effect of drinking large quantities of liquid on the muscles keeping the stomach in place: usually they become stretched to cope with this volume and that's what gives men the "beer belly", not the deposition of extra fat round the middle. So if you switch to vodka, as long as you're not diluting it with a pint of lemonade or coke, the volume will be less and the stomach muscles will not need to stretch in order to cope. Of course, your mate will then need to do exercises to tighten his stomach muscles and get rid of the beer belly. No gain without pain as they say. --TammyMoet (talk) 20:07, 8 January 2009 (UTC)

Are you drinking the vodka straight or mixing it with orange juice or something? If the latter, keep in mind that those add calories to the drinks. 216.239.234.196 (talk) 20:16, 8 January 2009 (UTC)

Vodka does have fewer calories per serving than beer. And, you will lose weight any time you're using more calories than you're taking in. So, a reduction in your caloric intake is good for losing weight, as is increasing the calories you burn. The calories in vodka (and pretty much any liquor) is from alcohol, not carbs. Fermentation changes the sugars into alcohol- after that, it's not sugar anymore. There would be sugar left over that did not ferment, but in a distilled beverage this sugar is not in the end result like it is with beer or wine. Friday (talk) 20:18, 8 January 2009 (UTC)

Be careful. According to this, there are 30 calories in 100 ml of beer and 222 calories in 100 ml of vodka (at 40%, which is slightly lower than what I'm used to). So even if a serving of beer comparable to 100 ml vodka is 700 ml, there would still be more calories in the vodka excluding the mix. And according to this, one gram of alcohol has more calories than one gram of carbohydrates. Here's another comparison. Zain Ebrahim (talk) 20:47, 8 January 2009 (UTC)

It says 55 calories in a shot of vodka. Compare with 100 or so calories for even a very light beer. There are no carbs in (normal) liquor, so liquor is the winner if you're looking to maximize alcohol content and minimize calories. Friday (talk) 20:51, 8 January 2009 (UTC)

Even for a pretty light beer, a pint is worth about 2 shots of a spirit alcohol wise. Assuming Zain's figures are correct, 570ml (about one UK pint) of beer would be 171 kcal. 1ml of alcohol in vodka would require 2.5ml of vodka, which would be 5.55 kcal. For the beer to have a calorie to alcohol ratio of 5.55kcal/ml it would need an alcohol content of 5.4%, which is a pretty strong beer. So, assuming the 30kcal figure holds for all beers (the source actually says 30kcal is for stout, bitter is 32 and lager 40), most beers are slightly worse than vodka in terms of calories per unit of alcohol, but strong ones are pretty similar. If you do switch from beer to vodka, though, you need to make sure you drink more water, since you aren't getting the water from the beer. --Tango (talk) 21:59, 8 January 2009 (UTC)

Water from the beer?? lol.. Beer is a diuretic, it makes you pee more then you drink, the resulting dehydration is one of the main causes of hangover.Vespine (talk) 05:24, 9 January 2009 (UTC)

No, that's wrong. In medieval times, small beer often was the staple drink for people, as water was likely contaminated. It's quite hard to get a hangover from normal beer alone, simply because it's 95% water - and this is also the main reason why it makes you pee. --Stephan Schulz (talk) 08:24, 9 January 2009 (UTC)

What is it in beer that is a diuretic? Isn't it the alcohol? Drinking vodka will also make you pee more, but it doesn't have the advantage of including lots of water, so it dehydrates you more. --Tango (talk) 12:44, 9 January 2009 (UTC)

Child and Adolescent psychotherapist

Hello, I'm de:Benutzer:Widescreen from German WP. I'd like to know what kind of education and trainig Child and Adolescent psychotherapist got to have, to work in a Hospital or by there own. (excuse my bad english). In USA & GB please. Widescreen ^® 20:08, 8 January 2009 (UTC)

In the UK, I don't think there are any restrictions on who can call themselves a "psychotherapist". I think anyone explicitly practising psychotherapy in a hospital would be a psychiatrist, which is a type of doctor and they have the same medical degree(s) as any other doctor (they just specialise in psychiatry after they qualify). --Tango (talk) 23:24, 8 January 2009 (UTC)

"Psychotherapist" is definitely a licensed profession in the US. Not to the same degree as "psychiatrist", which requires a medical degree, but the US has a variety of licensing standards for anyone who professes to "treat" or "diagnose" patients for specific psychological conditions. Dragons flight (talk) 00:29, 9 January 2009 (UTC)

Or, of course, you could be a psychologist, which requires a degree in psychology. There are psychologists working in hospitals. See here for a job description of a psychologist's role in the NHS in the UK. However, treatment, as implied by 'therapy', is limited to psychiatrists. Psychologists do the talking and counselling instead. At least this is how I think things work here. —Cyclonenim (talk · contribs · email) 23:40, 8 January 2009 (UTC)

Counselling sounds like a kind of treatment to me. Prescribing drugs is definitely restricted to psychiatrists, but beyond that, I'm not sure how it works. --Tango (talk) 23:44, 8 January 2009 (UTC)

In US, psychotherapy can be provided by psychiatrists, psychologists, counselors or social workers and their education, and the type of service they provide, will vary accordingly. See the Occupational Outlook Handbook pages I have linked to, for more details. Abecedare (talk) 00:11, 9 January 2009 (UTC)

If you are an psychiatrist, you can work with both, adults and childs in USA & GB? Theres no specialization needed in Child and Adolescence? If you are an psychologist or social worker you can work as an psychotherapist (adult and child) in Hospital and as an own offer in USA. In GB only psychiatrists. I've read for example Peter Fonagy (GB) is trained in child and adult psychoanalysis. Is this an privat amusement? Got this education effects on the status in the health system? What about other Schools of Therapy for example Cognitive behavioral therapy? Got they any training in child psychology or is this part of the clinical psychology education? Widescreen ^® 09:02, 9 January 2009 (UTC)

In the UK there are basically two kinds of recognised professional working in this field. Psychiatrists are qualified as medical doctors and then also in psychiatry as their specialism, then in child psychiatry as a sub-specialism. The other kind of professional is a clinical psychologist who has a doctorate in clinical psychology (D.Clin.Psych.), a qualification that is equivalent in level to the PhD. These people would usually first have a first degree and perhaps also a master's degree in psychology and then would take their doctorate part-time while also training in the NHS. There are also postgraduate courses in clinical counselling. Itsmejudith (talk) 13:38, 9 January 2009 (UTC)

What's the lowest pint in Badlands national park?

Pleas place {{tb}} on my talk page when you have an awnser.--Ipatrol (talk) 22:03, 8 January 2009 (UTC)

January 9

Do we know if egg-laying is painful for birds?

Is laying an egg be as painful for the hen bird as childbirth is for human women? I'm just guessing that no-one has researched this in any great depth - but the thought crossed my mind when seeing these videos on YouTube. It certainly doesn't look as though it's fun for her - put it that way. Anyone have any info? --Kurt Shaped Box (talk) 00:11, 9 January 2009 (UTC)

I believe the main reason for the amount of pain human women have during childbirth is that the process works the same way as in other mammals, but with the pelvis rotated 90 degrees (to enable us to walk upright), so it doesn't quite work as "planned". Also, the large size of a human's brain (and therefore head) at birth relative to their pelvis in adulthood (compared to other mammals) is going to cause problems. So, I would expect (without evidence to the contrary) that egg-laying is as painful as childbirth in a typical mammal, which is significantly less than in humans. Someone else may well have evidence to the contrary, of course. (Also, quantifying pain is extremely difficult just within humans, trying to do so meaningfully between different classes is going to be next to impossible.) --Tango (talk) 00:25, 9 January 2009 (UTC)

Yeah, I suppose. Birds (or at least the species I'm familiar with) seem to have an incredible tolerance to pain - or at least they're better at keeping a stiff upper lip than we are. I've seen gulls trying to walk on two badly broken legs without crying out, or even losing their composure. A budgie of mine that caught a toenail in the wire of its aviary and ripped it off trying to escape squeaked in pain exactly once when it happened, then afterwards *seemed* completely unconcerned. Though I'd guess that their biochemistries would be screaming out if we were to examine samples of their blood... --Kurt Shaped Box (talk) 01:29, 9 January 2009 (UTC)

Well, eggs are a lot more, er, "vagodynamic" than babies, for one, and presumably if a woman were to give birth every second day or so like chickens lay eggs, it would get significantly less painful. My impression from watching my hens is that the process is more along the lines of taking a satisfying shit. --Sean 01:33, 9 January 2009 (UTC)

Speaking as a guy with no kids (so I might be completely and utterly wrong) - but it's the contractions (not the 'passage' of the infant itself) that are the main cause of pain in childbirth, aren't they? --Kurt Shaped Box (talk) 01:38, 9 January 2009 (UTC)

The crowning is apparently one of the most painful parts. --Tango (talk) 02:20, 9 January 2009 (UTC)

Also, while the same situation applies to me as KSB I suspect one of the reasons the contractions are painful is because of what happens during them Nil Einne (talk) 09:36, 9 January 2009 (UTC)

What happens during a contraction? Isn't the contraction what is happening? The muscles around the cervix contract, dilating it. --Tango (talk) 12:47, 9 January 2009 (UTC)

A chicken egg seems larger than the mother's skull, whatever that's worth in comparing human childbirth pain with egg-laying pain. The chicken should be laying a quail egg for it to be comparable. But, then, maybe a hen has a larger pelvis relative to the egg than a human mother does relative to the baby's skull. Edison (talk) 05:22, 9 January 2009 (UTC)

Shouldn't you be comparing it to the body size rather then skull size? Part of the reason is because the chicken has a rather small head compared to its body compared to humans. Nil Einne (talk) 09:38, 9 January 2009 (UTC)

Indeed, the reason I mentioned heads above is because with human babies the head is the largest part. That's not the case with chickens. --Tango (talk) 12:47, 9 January 2009 (UTC)

Another data point for my "it's not particularly painful" opinion is that childbirth is usually injurious -- and commonly fatal (absent medical care) -- to the mother, while egg laying almost never is. --Sean 11:56, 9 January 2009 (UTC)

Using the definitions of pain from the article, "an unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage" or "Pain is whatever the experiencing person says it is, existing whenever he says it does" then we cannot know if the bird doesn't talk. We should define our terms before answering. Icek (talk) 11:59, 9 January 2009 (UTC)

If our universe is an open one, is not that a a paradox?

Assuming that the bing bang theory is true, it would have sense to think that the matter is eternal going on from big bang to big crunch (not a big crunch exactly)over and over again, but if the universe is an open one.. wich is the origin of the "extremely dense and hot state point" that gave origin to the big bang expansion? --Starlingmaximilian (talk) 01:10, 9 January 2009 (UTC) Thanks and sorry for the poor english. —Preceding unsigned comment added by Starlingmaximilian (talk • contribs) 01:10, 9 January 2009 (UTC)

That's an excellent question, and not one we have a clear answer too. There are some theories involving multiverses, or you can go with "God did it", or probably one of numerous other ideas I can't think of. There is no widely accepted answer among the scientific community though (it's difficult to even work out what the question means, "what happened before the big bang" makes no sense since time started at the big bang, so it can't have a cause in the usual sense). --Tango (talk) 02:25, 9 January 2009 (UTC)

It's certainly a question that doesn't have an answer just now. It's possible that we'll never be able to answer it because when all of existance is contained in a literal singularity - then all information from "before" the singularity has been erased. If no information whatever passed between what came before - through the Big Bang - and on to us, how could we ever work out what came before? The "Big Crunch" hypothesis was a rather elegant and satisfying one - but sadly, it doesn't appear to be true. One kinda comforting thing is that the answer doesn't matter. For the same reason that we can't find out what happened before, there can be no influence from that time on present or future times - so the knowledge is purely a matter of satisfying curiosity - it wouldn't lead to further insights - useful inventions - or anything of that sort. SteveBaker (talk) 05:11, 9 January 2009 (UTC)

Perhaps all previous universes were closed, and this was the first big bang with enough oomph to be open. Last call, drink up, heat death awaits! --Sean 12:01, 9 January 2009 (UTC)

Strength of intermolecular forces

I know that dipole-dipole attractions hold solids and liquids together for polar molecules, and that london dispersion forces hold the solids and liquids for nonpolar molecules.

However, given several molecules (their formulas), I was asked to determine which had the "strongest intermolecular attraction"

For example, between (A) H2NCH2CH3CH3NH2 and (B) CH3CH3CH3NH2, I thought that (B) would have the strongest intermolecular attraction since the molecule is polar, whereas (A) is symmetrical and thus doesn't have a dipole moment. However, my teacher said that (A) has two sites, one on each end, where opposite partial charges between the molecules can attract each other, so (A) has stronger intermolecular forces. I am very confused: how can (A) have stronger intermolecular forces when the molecule does not display a dipole moment and thus has no dipole-dipole attraction. I thought we had to look at the polarity of molecules as a whole, not the polarity of individual bonding regions. Can someone please explain? —Preceding unsigned comment added by 68.111.75.89 (talk) 04:11, 9 January 2009 (UTC)

Intermolecular attraction is often local, especially for polar/ionic effects: "an amine group" is able to hydrogen bond, regardless of whatever else may be happening anywhere else in the molecule. Also, (A) doesn't actually look like you think it does...writing the way you did reinforces a very incorrect fiction for the overall molecular geometry. DMacks (talk) 05:17, 9 January 2009 (UTC)

Also, molecule A, being a rather long chain alkane, will have free range of motion around each C-C bond, and will assume whatever conformation will be the most stable. Get a simple molecular model kit and build it; you can easily make a "V" shaped conformation with the amine groups at the tips and a CH2 at the point. With that conformation, one can easily see (even ignoring H-bonding effects) that one can make a conformation which is quite polar; the question then becomes whether the energy of the intermolecular forces in THAT particular conformation can overcome the energy difference between that conformation and, say, the somewhat more stable "straight chain" conformation. Of course, none of that matters much because the H-bonding effects from the 2 amine groups overwhelms any other forces. However, my explanation could possibly work for a molecules where, say, the H's are replaced by say CH3 groups or something like that.

The questions about intermolecular forces are not as simple as often made out in a high school chemistry class, as there are often factors that, for simple reasons of time constraint, cannot be taught. There's lots of factors happening here, and one needs to consider all of them... --Jayron32.talk.contribs 13:06, 9 January 2009 (UTC)

Lightning

Hi, here are some questions my son has been asking me and I would be interested in hearing some thoughts. I'm not sure if I've answered him correctly...
1. If lightning follows the path of least resistence, why does it strike the highest point? Surely it should bypass a pole for example and go through the air and hit the ground?
2. When lightning strikes the ocean, how far does it spread? Does it kill fish on the surface only?
3. Somewhere I've read that a single lightning strike can power New York for a year. Why can't scientists capture lightning and harness its power? What are the challenges faced in doing this? (this one got me thinking too)
thanks, Sandman30s (talk) 11:39, 9 January 2009 (UTC)

1) Because the electrical resistance of the pole is enormously less than that of the air. Algebraist 12:26, 9 January 2009 (UTC)

3) Your source was wrong. The amount of electricity New York uses in a year is rather more than the amount of energy released by a hydrogen bomb, let alone a lightning bolt. Algebraist 12:31, 9 January 2009 (UTC)

(ec)Lightning follows the path of least resistance, yes. But air has a much higher electrical resistance than the pole in question. I don't know anything about the ocean question, but the energy will dissipate very quickly in the water. And the meme about the single lightning strike powering New York for a year is simply wrong. A lightning's power is in the terawatts, but it's lifetime is very short. The energy is impressive, but not that big. I may have dropped a zero here or there, but I come to about 500kwh for one lightning strike - theoretically enough to cover the electricity used by maybe 1000 average flats for one hour, not 10 million for a year. The problem is reliably capturing that energy and releasing it in a controlled manner. --Stephan Schulz (talk) 12:47, 9 January 2009 (UTC)

Our article on Resistivity has info to help quantify the first question. Resistivity is the measure of how much a substance resists the flow of electricity; i.e. low resistivity = high conductance. Air, being made of gasses, has large gaps between individual molecules, meaning that in order to conduct electricity, one has to force electrons to jump across a HUGE gap. At standard earth conditions, a good approximation is that most gases are 1/1000 as dense as solids or liquids; so all other things being equal, gases should be 1000x more resistive to electricity than solids. Of course, there is a huge variability in the resistivity of solids, largely due to how strongly those solid materials "hold on" to their electrons; however for nearly all but the most exotic materials, air is almost ALWAYS more resistive. So electricity will only stay in the air for the shortest distance possible... As far as number 3 goes; the difference between harnessing the electricity in a lightning bolt and generating it in a power plant is something akin to harnessing the power of a nuclear bomb and using nuclear fuel in a nuclear power plant... It may be possible to a point to do so, but there are so many more practical means of generating electricity. --Jayron32.talk.contribs 12:59, 9 January 2009 (UTC)

Number 2 was asked here a while back, only about a lake instead of the ocean. Same difference. Here is the answer from that question. --Milkbreath (talk) 13:07, 9 January 2009 (UTC)

CO2 in a fish tank for plants

I keep fish in a tropical aquarium and I'm trying to encourage better plant growth. It has been suggested that I introduce a CO2 injection system to up the amount of CO2 in the water. Could I just add some fizzy bottled water every now and then? Wouldn't this add more CO2? Would there be any risks to the fish? Thanks.91.111.119.120 (talk) 12:51, 9 January 2009 (UTC)

Adding carbonated water might boost the CO2 -- I'm not sure what the injection system would actually inject (basically, whether it'd be acidic or not). As for risks to the fish, it seems likely. I strongly suspect that ingredients apart from water and CO2 are in whatever bottled water you have -- even chlorinated or fluoridated water would present hazards, and treatments like those might not be required listing on the side of the bottle. — Lomn 13:50, 9 January 2009 (UTC)

Fizzy bottled water is probably a bad idea as this will be (I believe) more acidic than your usual tapwater, upsetting the pH of your aquarium. Not to mention the hardness of some fizzy drinks. When it comes to plant growth, have you tried other remedies first? This includes fertilizer for the plants (which go well with most fish but some snails and shrimps are sensitive to it) and changing the fluorescent light to one optimized for plant-growth. The choice of plants also matter of course. EverGreg (talk) 14:06, 9 January 2009 (UTC)

Soda water is acidic, but there's no way around that — adding CO₂ to water makes it acidic regardless of the source. If that's the only problem (I don't know this), you can easily offset the acid by adding something alkaline to the tank also. Drops meant to alter the pH of an aquarium are available at any supply store. --Tardis (talk) 16:23, 9 January 2009 (UTC)

How is it that all life on Earth descended from a common ancestor and not multiple ancestors?

One thing that has always wondered about as far as evolution goes is the concept that all life on Earth descends from a common ancestor. It seems to me that if life was created in primordial soup, it would have done so multiple times. That is to say, if one pool of primordial soup produced life, so would a second pool of primordial soup, a third pool, a fourth, etc.. Also, it seem to me that life could have formed more than once within the same pool of primordial soup. Therefore, there should be multiple ancestors and multiple lines of descent, not a single common one. How is this possible? Does this mean that one line of life wiped out all the other ones? Or is the spontaneous generation of life so unlikely that it only occurred once on Earth? (If that latter, is this a possible explanation for the Fermi Paradox?) I'm aware that we have articles on evolution, abiogenesis and common descent but other than a single sentence in the common descent article, "The theory of a common ancestor between all organisms is one of the principles of evolution, although for single cell organisms and viruses, single phylogeny is disputed" I don't see anything that specifically addresses my question (but maybe I missed it). 216.239.234.196 (talk) 14:25, 9 January 2009 (UTC)

There are two point here. The first is that, given enough resources, life grows exponentially. Hence, without competition, once the first life has been established, it will spread very quickly (on an evolutionary time scale). The second point is that once one kind of life has been established, the very existence of this may inhibit the formation of an independent strain, as the existing life forms are much better at consuming precursor molecules and structures than potential proto-life strains. Thus, even if it takes an average of only a million years or so for primordeal life to develop, the chances of two independent strains are very low. Thirdly, as we now know, there has been and still is a horizontal exchange of DNA, e.g. via viruses. Thus, the tree of life really is a complex graph, and only the major gene flow follows the tree structure. --Stephan Schulz (talk) 14:39, 9 January 2009 (UTC)

I don't think anyone is saying life couldn't have evolved more than once here on earth. However there is no evidence of more than one line, the form that gave rise to our current DNA and RNA. For all I know there could be some other form of life on earth not reproducing that way but I very much doubt it. It may be there was more than one form of life and the current form was just far better and the other form just died out, just look how many good viable species go extinct nowadays - there's a lot of competition. It is all speculation though without any evidence and I wouldn't hold my breath waiting for some evidence to come along. Dmcq (talk) 14:54, 9 January 2009 (UTC)

In addition to the points above, I also would say that the spontaneous generation of life may be so unlikely, that not only did it only occur once on Earth, it may not have occurred on many other Earth-like planets where it could have. We may be the only planet in the universe, or even among many parallel universes, where it did occur. One piece of evidence that it may be more common than this is that life seemed to evolve shortly (on geological time-scales) after the Earth cooled, which would seem to indicate that life occurs as soon as conditions exist which allow it. StuRat (talk) 16:49, 9 January 2009 (UTC)

Orders of magnitude for force...?

Hi. Why isn't there an orders of magnitude table for force? (Like there are for pressure, mass, etc. etc.) It'd be nice to have one, no? Kreachure (talk) 16:30, 9 January 2009 (UTC)

Sure, but this isn't the place to request a new article. This is: Requested_Article#Topic_areas_in_applied_arts_and_sciences. You might also leave your request on the talk page for orders of magnitude . StuRat (talk) 16:37, 9 January 2009 (UTC)

Well okay then, I just thought there was a particular reason for there not being one. Sorry... Kreachure (talk) 16:52, 9 January 2009 (UTC)

Cnidocysts stronger than a bullet??

Hi (again). After I found sources for the cnidocyte article claim that a cnidocyst accelerates to over 5,000,000g, I noticed that the cited source also says that despite its small mass, it's able to produce over 7GPa of pressure, "which is in the range of that generated by some bullets". According to orders of magnitude (pressure), the weapon discharge of a bullet is of 400MPa. I would like to know if all this makes sense. Even if it doesn't, I would like to know how a cnidocyst actually matches up to a bullet. Would it be able to puncture (on the microscopic level) a flak jacket significantly, for example? Thanks in advance, Kreachure (talk) 16:50, 9 January 2009 (UTC)