Wikipedia:Reference desk/Archives/Science/2009 April 23

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April 23

NRPG ?

NRPG. I'm uncertain as to what it means, and don't know where it is located in the CNS. Possibly called the Nucleus reticularis paragigantoceullaris, it definately excites the Raphe magnus and is involved in opiod modulation of pain transmission. Is that what its called and am I correct in assuming its next to the gigantocellular nucleus. Any help would be most appreciated, many thanks MedicRoo (talk) 01:15, 23 April 2009 (UTC)

Googling informs me that it's located in the ventrolateral part of the medulla oblongata, and that your speculations are correct. Looie496 (talk) 16:51, 23 April 2009 (UTC)

Light through optical centre

Imagine that a light ray passes towards the direction of the optical centre of a convex lens.

visit this[1]

when the light ray strikes the lens from air, it is not normally incident. So, it must be bent towards the normal at that point. It means that it will not pass through the optical centre. Even if it does, as it emerges out of the lens, it is not normally incident on the glass-air boundary. So it will be shifted away from the normal. It means that the light ray will emerge parallel to the incident ray. But the wiki article says that it will not get deviated. Please Explain with diagrams--harish (talk) 01:28, 23 April 2009 (UTC)

You didn't say what article you're talking about, but in any case, the ray will only emerge parallel to the incident ray if the angles of bending are exactly opposite when it enters and leaves the glass, which will only happen if the glass surfaces are parallel on both sides. For a convex lens as shown in the figure, the two sides of the glass are not parallel. Looie496 (talk) 02:46, 23 April 2009 (UTC)

The two surfaces are papallel at the center of the lens which seems to be the point of the question, though that is not entirely clear to me. Dauto (talk) 04:22, 23 April 2009 (UTC)

The thin lens equation in geometric optics is only approximate and assumes thin lens. Explanations of how lens work based on a simplified approximation may not be 100% accurate. 173.49.18.189 (talk) 04:57, 23 April 2009 (UTC)

I have fixed your image. Nimur (talk) 15:50, 23 April 2009 (UTC)

the wiki article is spherical lens and the question i ask is that why does the light ray experience no deviation according to the image?--harish (talk) 16:14, 23 April 2009 (UTC)

The diagram, ie the ray through the centre of the lens, is simplified. There is some refraction, but it is cancelled out on entry and exit. --Cookatoo.ergo.ZooM (talk) 17:51, 23 April 2009 (UTC)

The image is poorly drawn. The upper and lower rays are shown changing direction by refraction at both lens surfaces, as occurs with a lens of real thickness, while the purported central ray is unreal as the OP noticed. To be consistent with the thin lens approximation, the rays should change direction only at the center line of the lens (and in that case the central ray can arguably be drawn as it is). Cuddlyable3 (talk) 00:08, 24 April 2009 (UTC)

So, the total answer is that the ray will experience a little bit of deviation if it is not along the principal axis. Right?--harish (talk) 01:11, 24 April 2009 (UTC)

Bonjela and the news

I heard of the news today that medical research has shown that the use of Bonjela and similar over-the-counter treatments contain salts which could cause liver and/or brain damage in children under the age of 16. I'm curious in knowing which chemicals in Bonjela cause these side effects, and why the risk of damage to adults doesn't exist. Is it due to a more developed blood-brain barrier or maybe a metabolic deficiency that disappears over the age of 16? I can't find much reason why the same salts wouldn't cause toxic effects in adults. Regards, --—Cyclonenim | Chat  07:08, 23 April 2009 (UTC)

Bonjela contains similar ingredients to aspirin, whose use is strongly correlated with Reye's syndrome in small children. That article itself mentions that the cause really is unknown, and my quick search of google scholar shows that this is still a very active area of research with little concrete evidence on any reason for the link, although the link itself is very firmly established for at least injested pills. Someguy1221 (talk) 07:41, 23 April 2009 (UTC)

The Bonjela press release states that the problem revolves around the use of Choline Salicylate. Nanonic (talk) 12:48, 23 April 2009 (UTC)

Bonjela is amazing. I found it far more effective in treating mouth sores than comparable U.S. products. I have bought it from a London chemist at astronomical shipping charges after the tube bought in Britain ran out. Are they reformulationg it somehow to correct the problem but maintain the effectiveness? Edison (talk) 19:09, 23 April 2009 (UTC)

There was some iodine-compound stuff my friend managed to bring back from Sweden I think, and it's insane, you apply it and ulcer never comes back. Shame it's banned for whatever reason in the UK. Bonjela is the next best thing for us over 16s :) Regards, --—Cyclonenim | Chat  14:04, 24 April 2009 (UTC)

Oh, and to answer your question, they've just made packaging more obvious that under 16s shouldn't be using it, just like aspirin. Bonjela Teething Gel doesn't contain the salicylates, and therefore can still be used on chilren from 2 months to 16 years. Regards, --—Cyclonenim | Chat  14:05, 24 April 2009 (UTC)

What could a super-large telescope array see?

I understand that the resolution or amount of detail that can be seen by telescopes, both optical and radio wave, increases with their width. And that very wide telescopes can be simulated by joining up two or more widely-spaced telescopes in an array. I know such arrays have been formed of radio telescopes at least. I'm not sure if optical telescopes have been linked like this yet, or if that is something for future technology.

My question is, if you had a very long baseline for two or more telescopes, such as one telescope being on earth and another on the moon or even on Neptune or Pluto, would the amount of detail be enough to see planets orbiting stars, or even see some surface detail on those planets? And is there any theorectical limit to the length of the baseline? 89.242.82.4 (talk) 10:56, 23 April 2009 (UTC)

What becomes tricky on very large scales is the speed-of-light limitations in the communications path between telescopes. Also, no matter how far apart you put your telescopes, their light-gathering abilities don't get any better - so imaging very dim objects doesn't really improve. SteveBaker (talk) 11:42, 23 April 2009 (UTC)

(ec) The technique is a type of astronomical interferometry called aperture synthesis. It's been done for a long time in radio astronomy; Very Long Baseline Interferometry can link radio telescopes across the entire face of the Earth. High-precision atomic clocks allow radio astronomers to synchronize and combine radio signals from widely separated telescopes.

The problem is quite a bit more difficult at optical wavelengths. Because radio waves are typically a million times (or more) longer than visible and near-infrared light waves, the problem of 'lining up' the data from multiple radio telescopes is correspondingly much easier than it would be for a similar array of optical telescopes. (On the plus side, the much-shorter optical wavelengths mean that comparable resolution can be obtained with a much smaller baseline size.)

Nevertheless, a substantial number of optical interferometers now exist: List of astronomical interferometers at visible and infrared wavelengths. One of the largest is the CHARA array in California; its six telescopes are linked optically through a series of vacuum-filled pipes to generate a 330-meter (1100-foot) baseline. Together, they can resolve features down to 0.0005 arcseconds (0.5 milliarcseconds) — in 2007 they generated images of the surface of the star Altair, 17 light years away.

The twin 10-meter Keck telescopes in Hawaii can be linked optically to generate a very sensitive nulling interferometer with an 85-meter baseline. In that configuration, they are aimed at a star and configured so that the light from that star is optically cancelled-out between the two telescopes. Off-center light – as from an extrasolar planet – doesn't get cancelled out. In principle, the planet should become visible once it's no longer drowned out by the glare of its star.

Off the top of my head, I don't think there's any upper limit imposed by physics on the size of an interferometer array. The real bounds are the limitations of engineering. For an optical interferometer to work, you need to know and maintain the relative positions of the components with a precision of less than one micron (smaller than the wavelength of the light you're collecting). It's painstaking but possible to do when you've got a group of telescopes all together on the same mountain; it's a nightmare to manage if you want to put the telescopes further apart. Proposals exist for space-based optical interferometers as well, though as far as I know none are currently under construction. TenOfAllTrades(talk) 12:10, 23 April 2009 (UTC)

I don't want to spoil your wonderful answer, Ten, but I have to say that "vacuum-filled" made me do a double-take. Deor (talk) 13:08, 23 April 2009 (UTC)

Himiko. Kittybrewster ☎ 14:59, 23 April 2009 (UTC)

Ha! Yes, I winced a bit when I typed it, too. I figured the minor scientific blasphemy could be excused for the sake of clarity of meaning. (When I was drafting the post, my original response described the system as being linked by 'vacuum tubes' — precisely correct, but horribly confusing to anyone who read the phrase as meaning the electronic device rather than simple empty pipes. I also toyed around with 'evacuated' tubes, but that leaves one shaking one's head at the obvious necessity to remove people from the light path.) TenOfAllTrades(talk) 19:47, 23 April 2009 (UTC)

I think too much is made of these kinds of "minor blasphemies". The meaning is perfectly clear in context and the phrase is entirely useful. Language is just language - it doesn't have to reflect precisely the deep-down scientific truth - so long as everyone is clear about what is meant by it. SteveBaker (talk) 03:34, 24 April 2009 (UTC)

The only limit imposed by physics on the size of those arrays that I am aware of is the coherence length of the radiation. This length is proportional to the square of the wavelength, so it becomes an increasingly harder problem to deal with as the wavelength beeing used becomes smaller. The coherence length is also inversely proportional to the bandwidth so it is possible to get arbitrarily large length simply by using arbitrarily narrow bandwidths. There is no free lunch though. An arbitrarily narrow bandwidth makes the source arbitrarily dim and hard to see. There's a trade off here that is taken into consideration when deciding how large to build an telescope array. Dauto (talk) 18:04, 23 April 2009 (UTC)

So if you did have an array consisting of optical telescopes on the earth and the moon, or at equivalent distances on satelites, and assuming the engineering problems were overcome, then would you be able to see any surface detail on planets orbitting stars? The baseline distance would be far greater than that of current arrays. Is there any formula that relates array width to resolution? 89.241.44.96 (talk) 10:10, 25 April 2009 (UTC)

Yes, it is possible in principle, though the technical difficulties would be very daunting. The formulae can be found at Angular resolution. Dauto (talk) 22:06, 26 April 2009 (UTC)

The subjective experience of being blind

Does it seem like perpetual black night? Or might it even be whiteness, or nothingness? The blind spot on the eye is more like nothingness or whiteness rather than blackness, with the brain seeming to fill in what is there from the surrounding image. See http://www.colorcube.com/illusions/blndspot.htm As there are various causes of blindness, so the subjective experience may differ. 89.242.82.4 (talk) 11:07, 23 April 2009 (UTC)

As I understand it Blindness is dependent on the individual. Some see an out-of-focus world, some can see 'shadows' of things etc. This forum post might be worth a read (http://www.physicsforums.com/showthread.php?t=122382). 194.221.133.226 (talk) 11:22, 23 April 2009 (UTC)

For people who have been utterly blind since conception, whole areas of the brain related to vision don't develop so I doubt there would be any sense of 'blackness' - just no vision sense at all. That's impossible for a sighted person to even imagine and discussing what that means with a blind-since-birth person results in no common terms of reference. They can't explain what it's like to not have a sense that they never had. Can you explain to a dolphin what it's like to have no echolocation sense? Or to a fish, how it feels to have no lateral-line electrical sense? I don't think so. People who have become blind after being sighted will doubtless have a different sense of what it's like. SteveBaker (talk) 11:40, 23 April 2009 (UTC)

I once heard someone saying (I am not blind) that a completely blind person can see just as much with their eyes as I can see with my knees. That makes it pretty clear for me... -M —Preceding unsigned comment added by 195.67.112.146 (talk) 12:21, 23 April 2009 (UTC)

There is a phenomenon in perception (I'm blanking on the name right now, but it's related to change blindness and inattentional blindness) where the mind subtracts out a constant stimulus. It still may be registering at the sensory nerves, but after a while it is no longer perceived consciously. You've probably experienced this yourself. If there's a humming fan, after awhile it no longer registers, but when it turns off you can "hear" the silence. Likewise with scents - after a short period in a strongly scented room, you no longer can smell anything "off", but leave and reenter and the smell hits you. I would imagine the same would happen with a blind person. Immediately after becoming totally blind they might register a strong white/strong black perception. But after a while with that constant stimulus, the brain would ignore the signals coming from the optic nerves completely, and they wouldn't "see" anything at all. -- 128.104.112.117 (talk) 14:38, 23 April 2009 (UTC)

I have a blind friend who experiences different colours depending on the circumstances he is in, particularly when talking to certain individuals. I generate a blue/green colour. Normally he is not aware of any colour because he is not 'looking' but concentrating with his other senses. Richard Avery (talk) 14:54, 23 April 2009 (UTC)

Am I right that he wasn't blind since birth? Nil Einne (talk) 16:11, 23 April 2009 (UTC)

I'd bet that too - otherwise how could he know that this 'color' is blue and not pink? If you'd never seen blue or pink they be just arbitary labels. Assuming Nil Einne is right (and it seems very likely) then this is just a case of synaesthesia - which is a rather well-known phenomenon, even in sighted people. SteveBaker (talk) 20:05, 23 April 2009 (UTC)

I linked this article before, but you might find it interesting in this regard. [2] It illustrates that even when a blind person regains sight the brain is having trouble interpreting what it is "seeing". 76.97.245.5 (talk) 17:22, 24 April 2009 (UTC)

Why do people collect things / derive satisfaction from completing sets of objects?

I am well aware of hoarding, but I'm interested in the more mundane and widespread human compulsion to collect things. I know we're not the only animal to do this, but I'm having a hard time seeing the evolutionary value of such a finely honed desire to accumulate things.

I'm sure there are occasional cases where an impressive collection of _____ resulted in the acquisition of a mate, but I doubt that that was the conscious goal of the collection to begin with.

So... why do (most) humans feel a need and derive satisfaction from collecting things? What is it about a complete set that soothes the mind? Oftentimes these objects serve no use other than to occupy space (and please the collector...) 61.189.63.224 (talk) 13:00, 23 April 2009 (UTC)

Not all human desires/traits are linked (clear or otherwise) to an evolutionary reason. We could speculate that things that are collectable have their roots in effort/time/reward. It takes time and effort to get a complete set of something, so the satisfcation is the reward. If you receive a complete set instantly it wouldn't have your emotional journey attached to it. I'm not sure that everything needs to have an evoluntionnary reason for existence. 194.221.133.226 (talk) 13:52, 23 April 2009 (UTC)

Just a guess: In prehistoric times collecting nuts and berries (food) may, on occasions, have made a difference between survival or not. Equally, gathering bits of timber (fire) and heaps of rock fragments (defense / tools) may have given some hominids an advantage in survival. Collecting stamps, beer coasters or Van Goghs could be just a sublimation of this. --Cookatoo.ergo.ZooM (talk) 14:23, 23 April 2009 (UTC)

Is it possible that it's a learned behavior planted in our heads by society? How many times in your life have you heard the phrase "collect all six" (or whatever quantity)? Is the drive to collect a set universal in all cultures, or only in capitalistic societies? 168.9.120.8 (talk) 14:29, 23 April 2009 (UTC)

Also note that extreme cases of "collecting" are considered compulsive hoarding and are classified by many psychologists as a personality disorder. In extreme cases, it can be linked to a variety of more serious conditions such as addiction, delusion, and obsessive-compulsive personality disorder. Viewed from this perspective, "collecting" may be seen as a disorder, rather than an vestigial evolutionary habit - but of course it depends on the severity and how much it interferes with other activities. Nimur (talk) 15:42, 23 April 2009 (UTC)

There is obviously value in an evolved tendency to collect stuff like food or sticks for a fire - but as the OP points out - we may get highly obsessed with having one of every kind of postage stamp released by Tibet - yet have no interest in collecting 400 almost identical postage stamps from Tibet. That's a totally different behavior. We would have no evolutionary advantage to collecting one of every kind of berry from the bushes near our caves - yet that's what we do with postage stamps. My guess is that it has more to do with tool use. When going hunting - you need one knife, one axe, one spear, one bow, etc - it's important not to leave without your complete "set" of tools - and it does you no good to have six knives with you if you forgot your spear. But that's a really wild guess...I bet the real answer is REALLY interesting! SteveBaker (talk) 16:29, 23 April 2009 (UTC)

It could just be a self-fulfilling thing. We collect things that are valuable, complete sets are often deemed more valuable than the sum of their parts, so we collect complete sets. There doesn't need to be a reason for complete sets to be considered valuable, they are because they are. It's like fiat currency. It has no inherent value, but because everyone thinks it has value, it does have value. --Tango (talk) 16:48, 23 April 2009 (UTC)

This same compulsion may be the cause of some Wikipedia editors creating stub articles about every highway exit, or other things that can be linked by succession boxes. The same satisfaction may accrue as when someone pops yet another US state quarter into an album. Edison (talk) 19:04, 23 April 2009 (UTC)

I have over 300 toy MINI Coopers...but I don't think they're valuable (well, except maybe one or two of them). It's not a matter of value...there is some deep obsessive streak in many people. Why we have that is hard to say - but it's clearly not the hope of monetary reward. SteveBaker (talk) 20:05, 23 April 2009 (UTC)

Collecting things isn't a particularly human trait. Just a couple of non-food examples: Bowerbirds collect all sort of decorative material to attract mates. Magpie nests often feature collections of lost glasses, spoons and assorted shiny objects. (Oops already mentioned in a post a bit higher up :-) Birds roosting on rocky ground steal pebbles they consider attractive from neighboring nests. Octopus vulgaris uses shells and other collected items to protect it's eggs. Hermit crab are well known for their skills in decorating their shells with all sort of debris and anemones. Domestic cats and dogs are sometimes found to have a hiding spot for socks, gloves, hair ties or shoelaces that they "collected". 76.97.245.5 (talk) 17:06, 24 April 2009 (UTC)

• Squirrels, beavers, and some other rodents stockpile food. So do some ants. And of course honeybees. Being able to maintain a larder gives a heterotroph a potential survival advantage in an environment where the food supply is irregular. See Hoarding (animal behaviour).
• The O.P. wrote: "I doubt that that was the conscious goal of the collection to begin with." In fact most adaptive behaviors do not result from conscious goal-formation. For example, most of the time when one human feels sexually attracted to another human, the cause of attraction is rarely a consciously felt desire to create offspring. In many encounters, perhaps even most, one or both partners have a consciously felt desire to thwart procreation. Quite clearly, in the ancestral environment it was not necessary to consciously desire children - it was only necessary for people to desire sex, and then be willing to love and care for the products.

--Teratornis (talk) 23:10, 24 April 2009 (UTC)

As I pointed out before though - simply collecting a large number of food items in order to survive the winter isn't the kind of behavior our OP is interested in. The question is about the tendency for people to want complete collections containing one (and typically, only one) of every representative of some kind of set. You would not want a thousand very similar empty coke cans on a shelf in your garage - but there are people who try to have one of every variation on the coke can from 1950 or whatever. Someone who had a thousand empty coke cans with no particular 'meaning' to them would be labelled kinda crazy. Someone who had a collection of every different can Coke ever made would be considered somewhat amazing - but not really crazy. That's clearly nothing like the same behavior. We can easily understand the evolutionary drive to acquire large amounts of 'stuff' - but where did the drive to collect just one of each different 'something' to make a set come from? It's hard to guess. SteveBaker (talk) 00:22, 25 April 2009 (UTC)

Also as I suspect some contributors can such as SB attest to, collecting 300 Tibetian stamps, wikipedia highway articles, US state quarters, beer coasters or toy Mini Coopers, doesn't generally help to attract mates. Nil Einne (talk) 20:08, 25 April 2009 (UTC)

I have a collection of about 2,500 LPs, many of which I still play frequently (partly because I have some rarities that have not yet made it to CD transfer, and partly because I prefer the sound of LPs, even on crappy equipment such as I have). My collection includes some LPs that I played once, and never again. It also includes some LPs that I never played at all. These include the start of the complete set of Haydn symphonies (he wrote over 100 of them). A complete set occupies about 50 LPs. I acquired about half of them, then the company that produced them went bust or something. Although I've never played any of them (well, maybe just a couple), I've always been deeply, profoundly dissatisfied at owning only half the set. I've often asked myself: since I'm not that interested in Haydn, why did I start collecting his symphonies to begin with? I still have no answer to that. All I know is that my life would be immeasurably richer if I owned a complete set of unplayed Haydn symphonies rather than half a set of unplayed Haydn symphonies. Go figure. -- JackofOz (talk) 20:52, 25 April 2009 (UTC)

Brain food

Which foods are good for the brain? Are bananas good for brain function? Are there other foods? Thanks for any help received. —Preceding unsigned comment added by 58.161.138.117 (talk) 13:57, 23 April 2009 (UTC)

You might like to try Brain food, section 3.10 seems to have a few words about dietary brain enhancers. Most foods purported to assist brain function are of dubious value, but there's no accounting for placebos. Richard Avery (talk) 14:49, 23 April 2009 (UTC)

Jeeves recommended fish. Kittybrewster ☎ 14:53, 23 April 2009 (UTC)

Yes - but that's fiction and this is the science desk. Could we please try to stick to actual facts? SteveBaker (talk) 16:20, 23 April 2009 (UTC)

Wodehouse in the Jeeves account (early 20th century) was reflecting a common belief. Fish had been considered "brain food" way back in the 19th century, and nutrition books in the 21st century still claim it is "brain food," with some dissent that it is not particularly a brain food. See Google book search:[3]. Edison (talk) 19:01, 23 April 2009 (UTC)

Sugar enhances brain function over the short term by enhancing arousal, if you don't eat too much. Over the long term, I'm not aware of any solid evidence for foods whose value for the brain is different from their value for the body in general. You'll find vast numbers of claims all over the place, but solid evidence is sorely lacking. Looie496 (talk) 16:44, 23 April 2009 (UTC)

Fish oils are pretty good for the brain as Omega-3 fatty acids help the brain to repair and maintain itself. Regards, --—Cyclonenim | Chat  16:49, 23 April 2009 (UTC)

Grace Slick of Jeffersen Airplane in the song "White Rabbit" urges us to "Feed your head". It is not clear with what, but the audience at Woodstock seemed to know what she meant. Peace. Cuddlyable3 (talk) 19:25, 23 April 2009 (UTC)

Judging by how good fish is often said to be for the brain, maybe it'd be worth trying some dolphin. 86.8.176.85 (talk) 19:34, 23 April 2009 (UTC)

Dolphins aren't fish. A Quest For Knowledge (talk) 20:01, 23 April 2009 (UTC)

Actually, this dolphin is a fish. cheers, 10draftsdeep (talk) 21:01, 23 April 2009 (UTC)

The actual facts, with regard to omega-3 fatty acids, is that their effect on brain function has not been proven, see these abstracts. --NorwegianBlue ^talk 19:57, 23 April 2009 (UTC)

Whilst not conlusive, there is a lot of evidence in support of the theory too. See [4], [5], plus many more in support on PubMed. The topic is still under heavy debate, but most articles seem to confirm the effect of n-3 fatty acids on the brain. Regards, --—Cyclonenim | Chat  23:36, 23 April 2009 (UTC)

Many infant formulas are fortified with DHA (Docosahexaenoic acid) as DHA is used in metabolic pathways in the production of phospholipids found in the brain. It is also of rather high concentration in natural mother's milk. Primary natural source of DHA? Fish oil. Jeeves may have been on to something. --Jayron32.talk.contribs 00:45, 24 April 2009 (UTC)

Amygdala

Is there any classification that considers the Amygdala part of the Basal ganglia?? Thank you for your time :-) Maen. K. A. (talk) 18:27, 23 April 2009 (UTC)

Sorry for disturbing you, I found the answer at the Amygdala article Maen. K. A. (talk) 18:29, 23 April 2009 (UTC)

Resolved

StuRat (talk) 19:15, 23 April 2009 (UTC)

Must be the easiest question you've dealt with today Stu. SpinningSpark 21:35, 23 April 2009 (UTC)

In case you're not kidding, let me say that I only add my name after I add the resolved flag to show that it's my opinion, based on the original poster's comments, that this question is now fully resolved. If you were kidding, then sorry to be such a nuisance. StuRat (talk) 07:48, 24 April 2009 (UTC)

Minimum amount of fuel to circumnavigate the globe

If you were limited to travelling only by propulsive transport (ie no bikes, swimming, hangliding etc) what is the minimum amount of fuel that you would have to use? And presuming that different vehicles will use more/less efficient fuel etc, what's the least amount of CO2 you'd emit doing it? If anyone has any thoughts that'd be great. 86.8.176.85 (talk) 19:18, 23 April 2009 (UTC)

Where are you starting from? Altitude, location, and path (equator) are very important factors. -- kainaw™ 19:22, 23 April 2009 (UTC)

Well, assuming you aren't going to let us use yachts or sailing ships or hot air balloons of any kind - the Virgin Atlantic GlobalFlyer circumnavigated on about 10,000kg of JP4 jet fuel. That was a solo flight in one of the most efficient planes imaginable - so it's probably about the best you can do in a plane. Concorde needed about sixty times as much fuel (and consequently, six refuelling stops) to do the same thing. Doing the trip in a boat ought to be a lot more efficient...especially if you can cheat and use sails. SteveBaker (talk) 19:57, 23 April 2009 (UTC)

Is it cheating to use a solar-powered aircraft that uses 0 combustible fuel? Tempshill (talk) 20:10, 23 April 2009 (UTC)

If you don't count the fuel you use in the 1st 10 minutes, a satellite really can go around thousands of times while using no fuel. Otherwise, I would say That a helium balloon would do pretty well. 65.121.141.34 (talk) 20:29, 23 April 2009 (UTC)

The trouble with a helium balloon is that you do actually need to consume helium and ballast on those long flights because you have to 'steer' by rising up and dropping down into the wind currents that happen to be going in the direction you want to go. Doing a round-the-world trip on helium alone would be really tough! There are various hybrids of helium balloons and solar-heated hot-air (a "rozier"), for example. A rozier was the first balloon to circumnavigate the world - but it needed a lot of propane still - certainly less than the GlobalFlyer thing...but I suspect our OP won't let us use balloons. I love the satellite idea though - that's great! SteveBaker (talk) 20:38, 23 April 2009 (UTC)

The added bonus is that a H2 + O2 reaction will not cause any CO2. You will of course use CO2 doing the air sep to get the O2. 65.121.141.34 (talk) 18:22, 24 April 2009 (UTC)

As always, this sort of thing comes down to clearly defining some ambiguous criteria. As noted above, how strict is "propulsive"? Sailpower seems rather obviously against the spirit of what you've requested, but consider these less-obvious problems:

• GlobalFlyer flew west-to-east to benefit from the jet stream, a non-propulsive ~150 kph boost
• Satellites, considering launch propulsion, launch from west-to-east to benefit from the Earth's rotational velocity, a non-propulsive ~1500 kph boost.
• Ships of various forms often exploit ocean currents, non-propulsive ~5 kt boosts.

Additionally, why disallow bikes or swimming? Humans require fuel and a decent CO₂ estimate could be made.

Anyway, for my take on the answer: You expend the least fuel/CO₂ circumnavigating the globe via nuclear fission. Take your pick of several naval vessels. — Lomn 20:55, 23 April 2009 (UTC)

For some specifics, the S9G reactor used in Virginia-class submarines has a design lifetime of 33 years and an estimated reactor mass of 360 kg.[6] The USS Triton required two months to circumnavigate the globe (the first submerged circumnavigation). The Virginia would "use" 1.8 kg of reactor mass over that time frame, with effectively no CO₂ emissions associated with propulsion. — Lomn 21:15, 23 April 2009 (UTC)

To be complete, I'd argue you also have to amortize some cost for the radioactive nuclear vessel and other stuff that, upon decommissioning, has to be trucked somewhere to be buried and monitored for the next 10,000 years. Tempshill (talk) 22:15, 23 April 2009 (UTC)

A Cessna 150 cruising at 198 km/h consuming 23 L/hr of Avgas should be able to fly a 36 787 559km circumnavigation consuming 4 273 302 L. I wonder whether the OP wants such an abstract calculation or practical information?

The good news is that thousands of Cessnas have been produced so they are readily available, not too difficult to fly and you have room for a passenger. The bad good news is that the standard aeroplane needs a LOT of refuelling stops, about every 600km. Arranging that on land would need international negotiations and almost certainly demand a longer route. Over the oceans....well, if you are in no rush you could beg "friendly" aircraft carrier captains to let you land and fill up. Cuddlyable3 (talk) 23:44, 23 April 2009 (UTC)

You might want to check your decimal point – the circumference of the Earth is roughly 36 thousand kilometers, not 36 million. That would make a much more reasonable four thousand liters of fuel. Cheers! TenOfAllTrades(talk) 01:50, 24 April 2009 (UTC)

Eeek! I'm not sure I'd want to contemplate landing (or taking off for that matter) from an aircraft carrier in a Cessna 150! It's a seriously scarey business in something like and F18 that's designed for the job. The lack of an arrester cable hook would mean you'd either have to pull off some impressively short landings or smack into the crash netting each time. The relative fragility of the landing gear would demand really smooth seas when you did it - and I honestly wouldn't want to be in a Cessna that's hooked up to a modern deck catapult for the take-off run! If you have to stick to land-based routes, you'll be taking some considerable detours...but still, I think you could do it using marginally less gas than the Virgin Atlantic GlobalFlyer - so perhaps this is still the best solution so far in terms of fuel efficiency. SteveBaker (talk) 03:30, 24 April 2009 (UTC)

The stall speed of a Cessna 150 is only 42 knots, minimum ground roll for landing is 450', 1075' for takeoff. Remember, the carrier would be travelling at least 25 and as much as 35 knots into the wind. No problem, no arresting gear or catapult required, it would be loads of fun, though a pitching flight deck might make it a little more interesting.—eric 05:36, 24 April 2009 (UTC)

I don't remember which one, but in one edition of Microsoft Flight Simulator, landing some manner of Cessna on an aircraft carrier was one of the built-in "adventures". Who knows how accurate it was modeled. I'm not sure you'd be able to find carriers that carried the right fuel, though. (Maybe for helicopters?) APL (talk) 13:38, 24 April 2009 (UTC)

Well, the largest carrier on the planet is probably the Nimitz - it's entire deck is 1100' long - so your 1075' minimum take-off run would require you start at one end of the deck and you'd 'unstick' about 30' from the end...well, 30' minus the length of the plane - maybe you'd have three feet to spare. Yikes! But recall that the flight deck of a carrier doesn't work like that. The landing and take-off areas are both much shorter than the total length of the deck because the thing is designed to have planes landing and taking off simultaneously. Also, not many carriers are the size of the Nimitz - most are more like 800 feet long - and then you're flat out of luck for your take-off run. Worse still - the minimum take-off run you're quoting for a Cessna assumes a near-minimum take-off weight...and since we're nowhere near the next airfield - you're definitely going to be needing a full fuel load! As for steaming into the wind at 25 to 35 knots...yeah - it can definitely do that - but the turbulance that causes at the front and back end of the deck would flip a little cessna around like a dry leaf in the fall! You're going to need very light winds and a very, very calm ocean and the biggest aircraft carrier in the world to stand a chance in hell of doing that! (Maybe if we put a huge conveyor belt onto the carrier deck and landed on that?) ;-) SteveBaker (talk) 13:48, 24 April 2009 (UTC)

If your airplane needs 50 knots airflow over the wings to fly, which is very close to the requirements of our Cessna 150, a takeoff into a headwind of only 5 knots (which is 10 percent of the takeoff speed) will reduce the length of the takeoff run by approximately 19 percent over what would otherwise be required with no wind. A headwind of 25 knots (50 percent of the takeoff speed) will reduce the ground run by 75 percent. Eichenberger, J. A. (2003). Your Pilot's License. p. 183.

I've never been on the flight deck of a carrier, so can't speak to how much turbulence there would be.

Sorry, but typed in the distance for landing over a 50' obstacle rather than the short field takeoff distance, it's actually 735'[7]. As to takeoff weight, the distance quoted is for a 1600 lb. aircraft, 22.5 gal. fuel (max is 38 gal.), 340 lbs. for pilot and passengers and 76 lbs. for baggage. From the flight manual, 1600 lbs, sea level, 59°, 20 knot headwind, ground roll: 305'. No worries.—eric 16:47, 24 April 2009 (UTC)

According to [8] which links to [9] and says "Cessna O-1B Birddog in the colors of the South Vietnamese Air Force. This aircraft was landed onboard USS Midway during the fall of Saigon in 1975, by a pilot who had never before landed on an aircraft", this was the only case of a Cessna landing on a aircraft carrier. I don't know how that compares to a 150 Nil Einne (talk) 15:57, 25 April 2009 (UTC)

The original questioner mentioned bicycles. Since you can't circumnavigate on a bike, the questioner must be thinking about switching vehicles. You could arrange your trip so that the last leg of the trip was made on a small, fuel efficient scooter carried on your original vehicle. I'm not saying it would be a safe thing to do, but you could cover about sixty degrees of longitude by scootering across Africa sticking reasonably close to the equator.

But then again, if you're going to take it to that ridiculous level, you might as well go all the way and procure some sort of solar car.APL (talk) 02:24, 24 April 2009 (UTC)

And if you're not in a hurry - or under any cost limitations - then a solar boat would not be out of the question so you don't have to worry about putting the car on a boat in order to get it across the wetter bits of the planet. The point is that if you have no time or budget constraints, you could use a series of electric cars and boats with batteries charged from solar panels - lined up waiting at each port of call along the way. But truly, a yacht makes more sense...plenty of people have sailed around the world using nothing more than the wind and a technology that's been around for thousands of years - it's a very do-able thing. This is one of those questions where you have to keep excluding the obvious, practical answers in order to get the answer the OP wanted - and that just gets silly! The proper answer is: zero...unless you're in a hurry or trying to do it within a particular budget. SteveBaker (talk) 03:30, 24 April 2009 (UTC)

Wow, thanks for ll these great answers guys. In answer to your musings, I'd be fine with any vehicle as long as it is powered by more than human energy, although I guess I'm more interested in fuel-burning methods. I like the ideas of a nuclear submarine and a solar car, though. I'd be fine with vehicle changes, and I'm interested in both hard numbers answers and "well, if you put a flux capacitor on a jetpack, then..." sort of answers too. Thanks, again, you've all been great. 86.8.176.85 (talk) 03:25, 24 April 2009 (UTC)

LAMP is Lutheran Association of Missionaries and Pilots. They fly donated planes across the oceans for Christian mission work, including providing planes for medical flights in third world countries. I read of one such plane which was flown from California to Hawaii enroute to Asia. It was a single engine small plane with extra fuel tanks, making a near-suicidal long duration over-water flight. When it contacted Honolulu air control, it was give priority for landing over larger commercial craft. They routinely do what are, basically, Charles Lindbergh flights.Edison (talk) 05:36, 24 April 2009 (UTC)

You could use a yacht over sea and a land yacht over land. Or bicycle over land and a rowing boat over sea. Many people cycle 'around the world' and often write books about it. It started in the 19th. century on penny farthings, aklthough I see from the article that someone also did that on them in 2008. See Thomas Stevens (cyclist) And why not use a solar powered car and motor-boat. 78.151.148.89 (talk) 22:44, 24 April 2009 (UTC)

If you are not in a hurry, you could sit where you are and wait for plate tectonics to take you at least part of the way around in a few hundred million years. Best to position yourself as far as possible from a subduction zone, however. A somewhat faster option, but also not guaranteed to work, and probably not something you could survive, would be to seal yourself into a Drifter (floating device) and release yourself into the ocean. I'm pretty sure that some of these devices have circumnavigated the globe. Neither option requires any fuel for propulsion, but if you wanted to survive a circumnavigation in a drifter, you would probably need to pack enough food to last for several years, along with enough clothing to handle whatever climate regions you drifted through. --Teratornis (talk) 22:56, 24 April 2009 (UTC)

Maybe you could use a stirling engine in a hybrid car on dull days when the solar power was not working. Stirling engines seem to have a lot of potential. 89.241.44.96 (talk) 10:04, 25 April 2009 (UTC)

Nobody, except at the very beginning, said anything about latitude. If you start far enough south, you can go around many times, using this for propulsion, without needing to refuel until after several times around the world. And there's even a place where they have the fuel that you'd need to go around the world that way! Nyttend (talk) 12:50, 26 April 2009 (UTC)

'A true circumnavigation of the world must pass through two points antipodean to each other.' Norris McWhirter, founding editor of Guinness, 1971.[10] Cuddlyable3 (talk) 18:57, 28 April 2009 (UTC)

Slit-Like Iris

What is the technical word for the slit-like irises that cat's have? What other animals have it? Why or how did cats develop this?--Threebears2000 (talk) 21:44, 23 April 2009 (UTC)

Among the vertebrates, as far as I know, cats (but not lions), fennecs, and some snakes have vertical slit pupil; and goats have horizontal slit pupil. Frogs and toads have a variety of pupil shapes. Most others have a round pupil. Of the invertebrates, cephalopods have some pretty interesting eyes. A slit pupil is associated with eyes that have multifocal optics [11]. In addition to the slit pupil, cats also have a non-circular high-resolution region of the retina (not a true fovea AFAIR). This region is shaped like a lance-head or a distorted diamond, elongated horizontally, perpendicular to the pupil slit orientation. --Dr Dima (talk) 01:08, 24 April 2009 (UTC)

Not having slit pupils is one identifier how Big cats or Pantherinae (we have 2 pages??) are distinguished from other Felidae. 76.97.245.5 (talk) 14:40, 24 April 2009 (UTC)

current procedure terminology - has it changed over the years?

I am currently researching a cancer case for a deceased fire fighter from 1970. His family is adamant that he died due to colon cancer, the death certificate states diverticular disease.

With the CPT, is it possible that in 1970 diverticual disease was the term used to describe colon cancer? I had another file from the 70's that stated a person passed due to lymphosarcoma, this turned out to be what was later referred to as non-Hodgkin's lymphoma.

I have looked for a history of the terminalology with out success.

Any help or suggestions are appreciated.

Thanks. —Preceding unsigned comment added by Firefighter751 (talk • contribs) 21:50, 23 April 2009 (UTC)

I'm just Googling, but the first result if you google "diverticular disease" "colon cancer" states that the two diseases can have very similar symptoms and can be mistaken for each other, for what it's worth. Tempshill (talk) 22:18, 23 April 2009 (UTC)

Diverticular disease, particularly diverticulitis complicated by intestinal perforation and peritonitis, could be quickly fatal. Colon cancer might be present in such a situation but might not be listed as the proximate cause of death (either because the person filling out the form was unaware, or just not thinking of it). Death certificates are notoriously unreliable in this way. --Scray (talk) 02:05, 24 April 2009 (UTC)

As someone in medical school in the year you cited, I can assure you that colon cancer and diverticulitis were just as clearly distinguished by doctors and the CPT codes then as now. However, I agree entirely that causes of death listed on death certificates are not always entirely reliable. I remember being surprised as a covering intern the first time a patient died and the unit clerk handed me the death certificate to fill out-- it needed to be done right away so the body could be released to the funeral home. I had not been involved in the care of the patient and could have put down "hiccups" and no one else had to approve it. There are two common potentials for error: (1) a doctor available to pronounce the patient dead and fill out the certificate may not have known much about the patient, or (2) may have arbitrarily selected one of the patient's problems as the "cause of death" even though other conditions may have been present and contributed to it. People with diabetes often die of heart attacks, but a death certificate may not list the diabetes even though the heart attack may not have happened without it. alteripse (talk) 18:23, 28 April 2009 (UTC)