Wikipedia:Reference desk/Archives/Science/2009 May 30

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May 30

Plumeria

I've posted a query on its Talk page about Plumeria's otherwise New World origins including one Asian locale. --Thanks, Deborahjay (talk) 05:09, 30 May 2009 (UTC)

Trees of the World (Russell et.al.) describes the genus as distributed in Southern Mexico, Panama, and the Caribbean. It is also mentioned ibid. that the "the trees are found growing in temple grounds of Buddhists, Hindus, and even [sic] Muslims". I think is is therefore safe to assume Plumeria to be introduced in Southern India rather than being native there. I'll keep looking for a more definitive ref though. Best regards, --Dr Dima (talk) 05:31, 30 May 2009 (UTC)

Carnivores' flesh indigestible for humans?

Over the decades, I've collected the following impressions I'd like confirmed or disabused:

• Fox meat is indigestible for humans; legendary example: fur trappers lost in a blizzard would starve to death beside their plentiful catch of foxes or similar animals.
• Humans lack the necessary enzymes to digest certain proteins found in carnivore flesh.
• The above does not apply to the flesh of omnivores (e.g. dogs, humans).

Any science to back this up or otherwise? And where might I have searched such info? (Afterthought: probably someplace like The Straight Dope, but since I'm a Ref Desk Regular, I naturally posted here.) -- Thanks, Deborahjay (talk) 05:33, 30 May 2009 (UTC)

Dog meat is definitely edible. Bear meat is edible, too; there is a sort of salami-like product made with bear meat that used to be sold in Russia, I forgot what it's called. --Dr Dima (talk) 05:37, 30 May 2009 (UTC)

The Bear page does state: "Bears have been hunted since prehistoric times for their meat and fur". But while I understand they kill and eat animals, I thought they were omnivores (perhaps based on cartoons viewed in my childhood?). -- Deborahjay (talk) 05:46, 30 May 2009 (UTC)

Yes, you are right, both brown bears and domestic dogs may be considered ominvores (even though wolves and polar bears are obligate carnivores AFAIK, and they are so close genetically that the dog-wolf and brown-polar bear hybrids are fertile). However, cats are carnivores, and cat meat can be eaten, too. --Dr Dima (talk) 06:06, 30 May 2009 (UTC)

This forum is of the consensus that fox may not be particularly tasty (depending on what it dined on last), but is edible; one person even provided a recipe ("boil slightly, then fry"). There's another recipe for "pan boiled fox" here, with a claim that the person has tasted it. Clarityfiend (talk) 05:44, 30 May 2009 (UTC)

We also have an article on cat meat (a.k.a roof rabbit). --Dr Dima (talk) 05:50, 30 May 2009 (UTC)

And from the Brits (who should know their foxes): fox pasta. That article also says that "the Thais eat a lot of fox." Clarityfiend (talk) 05:54, 30 May 2009 (UTC)

OP's interjection: The cat meat page includes a telltale line: "Because cats are carnivorous, consumption of cat meat is not permissible under Jewish or Islamic dietary laws." Given my longtime albeit sketchy exposure to the Laws of Kashrut, this may be the source of my having extrapolated "don't consume" to "can't digest". The bacteria-and-toxin warning is effectively alarming, though. -- Deborahjay (talk) 06:05, 30 May 2009 (UTC)

AFAIK, carnivore meat can be eaten under pikuach nefesh conditions. If cat meat was deadly, it would not have been allowed under any conditions, I think. --Dr Dima (talk) 06:09, 30 May 2009 (UTC)

There was the analysis once of the cause of death of a human fossil as having been eating the organs of a large feline (source?).Julzes (talk) 06:49, 30 May 2009 (UTC)

Big cats don't take kindly to humans trying to eat them alive. --Kurt Shaped Box (talk) 09:41, 30 May 2009 (UTC)

It might have had something to do with eating the liver. In many carnivores the liver can be poisonous with too much vitamin A. Dmcq (talk) 10:00, 30 May 2009 (UTC)

For which we have an article, of course. Vimescarrot (talk) 10:11, 30 May 2009 (UTC)

Yes, I believe skeletal analysis concluded that this woman probably ate a lion's liver.Julzes (talk) 18:30, 30 May 2009 (UTC)

Have you ever heard that whale intestines are considered bad food, for some reason? Apparently (according to to TV), not even the scavengers will touch them. --Kurt Shaped Box (talk) 10:09, 30 May 2009 (UTC)

The standard explanation given to me is that it's inadvisable to eat carnivore flesh because they're higher up the food chain, thus will have more concentraded toxins (pesticides, herbicides, among any other, more natural, toxins). Vimescarrot (talk) 10:13, 30 May 2009 (UTC)

Another reason that's often been cited whenever the question of why people don't eat <carnivorous animal in question> has been raised here is that carnivore meat (supposedly) picks up the taste of whatever the animal has been feeding on. Which usually means that it's unpleasant on the palette. --Kurt Shaped Box (talk) 10:19, 30 May 2009 (UTC)

I would say that is a superstition. Most animals digest their food completely, breaking it down to basic molecules, then use these as nutrition for their cells. No "taste" can be transported from the stomach to the muscles in this way. This goes more into the spiritual direction "you are what you eat", the superstition that you take up spiritual parts of the animals/plants you eat. Biological nonsense. There are a few exceptions to this, but as far as I know these organisms enrich "by purpose" only certain contents of their food (e.g. toxins) they could not build themself. I would expect most mammal meat is perfectly digestible by humans, as the composition of mammals is mainly the same. Even other animals should pose no problem to our digestion, with the important exception of toxins that some have evolved to deposit in certain parts of their bodies, sometimes even in their flesh. And concerning the enzymes: What our digestion does is to cut down proteins/fats to very small pieces, than take them up. So it is basically unimportant what it was before, because afterwards it is just "basic chemistry stuff" that is then reused. It is a bit more complicated with sugars and other contents, but as we are talking about meat, which is mostly protein and fat, we are perfectly evolved to digest what may be in there. And as a remark: this is about digestion, not taste, and not about contamination if the meat is from carrion. --TheMaster17 (talk) 10:44, 30 May 2009 (UTC)

Actually it is partially true (just to be clear I was referring to Vimescarrot and KSB when I said it's partially true). Stuff like mercury, PCBs etc can't be digested... See also biomagnification and perhaps bioaccumulation. It's a far greater problem now then it used to be of course. This is of course in regard to toxins, not so much taste, although diet can definitely influence taste albeit not in such a simplistic way Nil Einne (talk) 11:36, 30 May 2009 (UTC)

This is not true at all, there are multiple examples of the animal's diet effecting taste and/or texture of the meat. Our cattle feeding article states there is a big difference in the taste between corn-fed and grass-fed cattle citing a study by Colorado State University. Corn-fed chicken is well known to be tastier and has a yellow colour, here's a recipe from a TV station saying so. The effect is scientifically objective enough that it can be tested for as this supermarket found to its cost when it tried to cheat. Atlantic salmon do not have the same taste as farmed salmon, even the red colour comes from their diet of krill, farmed salmon are either artificially coloured or dyes are added to their feed. SpinningSpark 13:55, 30 May 2009 (UTC)

I just want to point out that we do eat carnivores—lots of the fishes we eat are apparently purely carnivores. --98.217.14.211 (talk) 12:20, 30 May 2009 (UTC)

My (= OP's) intent was mammalian carnivores, though you're right, I did leave that unspecified. For the record (if I recall correctly), the Laws of Kashrut forbid eating scavengers and avian raptors, among other and better-known prohibitions. -- Deborahjay (talk) 12:59, 30 May 2009 (UTC)

I'm pretty sure if they'd had access to them, the Chinese would have given it a try, as per their saying "if its back faces the sky, you can eat it"[1]. TastyCakes (talk) 15:00, 30 May 2009 (UTC)

I once read in one of those SAS Survival Handbooks that you can eat at least some bits of just about everything that crawls, walks or flies, provided you know how to prepare it. In addition to the livers of several species and the skins of several more, you apparently shouldn't eat the heads of rats or venomous snakes (the latter seems obvious). --Kurt Shaped Box (talk) 16:29, 30 May 2009 (UTC)

I read the same handbook - you missed out "swims". Basically, the flesh of all animals is edible. You need to be a little careful with internal organs, but if you stick to flesh you are safe (at least, if you cook it, but even raw the risks are generally pretty small, the only diseases you need to worry about are those than can infect both the animal you are eating and you, and that's not many for most animals). --Tango (talk) 17:18, 30 May 2009 (UTC)

I don't know about 'swims' - there's plenty of odd things at sea. Would you be able to eat a stinging jellyfish, for example? --Kurt Shaped Box (talk) 17:34, 30 May 2009 (UTC)

Perhaps the handbook didn't count jellyfish as swimming, they generally just float around. At least some jellyfish are eaten, though: Jellyfish#Culinary uses. --Tango (talk) 17:49, 30 May 2009 (UTC)

Here's a quote from the survival instructions that live in my survival tin (which, usefully, lives on a shelf in my room...): "If it walks, crawls, creeps, flies or swims - it can be eaten. Avoid, however, oddly shaped fish, especially those with spines or horns or box shaped bodies." I believe the flesh of even those fish it says to avoid is edible, but it is just risky because you might accidentally eat a poisonous internal organ. --Tango (talk) 17:54, 30 May 2009 (UTC)

Poison... Poison... Tasty fish!. --Kurt Shaped Box (talk) 17:56, 30 May 2009 (UTC)

The reason those fur trappers died - despite stuffing themselves full of fox meat was because those kinds of animals are very lean - without enough fat content in your diet, you don't last long. See our article rabbit starvation. SteveBaker (talk) 15:07, 30 May 2009 (UTC)

Crocodile and alligator both taste pretty good and are easily digested. Rockpocket 20:56, 30 May 2009 (UTC)

We eat fish, and most fish we eat are strictly carnivorous. So are seals andf various other sea animals. Plus there's alot of scavenging bottom feeders like crab that we eat, and they dont eat any vegitation. Carnivourous snakes and frogs also eaten. Domestic dogs are a popular food in Thailand, although they are fed an omnivorous diet. 209.148.195.177 (talk) 11:06, 31 May 2009 (UTC)

What I've heard is that eating the liver of a predator can be fatal because they concentrate vitamin A at extremely high levels, but I don't think predator meat in general is inedible, although most of the muscule tissue must be so tough that you'd have to boil the hell out of it to make it chewable. Looie496 (talk) 18:09, 31 May 2009 (UTC)

Body pressure and atmoshperic pressure

what is the pressure inside an human body?How does it balance atmospheric pressure? —Preceding unsigned comment added by Mukildev (talk • contribs) 05:40, 30 May 2009 (UTC)

The most part of the inside of a human body is solid and will therefore be at atmospheric pressure. However there are some places within the body that are occupied by air but they are connected to the atmosphere to equalise changes in pressure. The middle ear is connected by the Eustachian tube, the digestive tract has an aperture at each end and cranial sinuses have external apertures. The lungs will have varying pressure depending on whether the person is inhaling or exhaling, but in any case they are open to the atmosphere. Richard Avery (talk) 09:18, 30 May 2009 (UTC)

However, Blood pressure is considerably higher. -Arch dude (talk) 10:11, 30 May 2009 (UTC)

Is that the reason for arterial spurt (wut, no arti-cool?), as a matter of interest? --Kurt Shaped Box (talk) 10:23, 30 May 2009 (UTC)

Roughly, yes. The reason it spurts is because of the varying pressure, due to the heart beating. If it were just constant high pressure it would spray out at a constant rate. --Tango (talk) 11:40, 30 May 2009 (UTC)

Thanks. Yes, that makes sense. --Kurt Shaped Box (talk) 16:31, 30 May 2009 (UTC)

• Pressures below atmospheric pressure often exist in the human body. Transpulmonary pressure has a red link for pleural pressure but says, "pleural pressure is always negative and relatively large". I do not think that is entirely true since pleural pressure is often said to be positive during forced expiration. See this and this. The page for transpulmonary pressure should link to pleural cavity. Breathing has a big ugly red link to negative pressure breathing. Interstitial fluid pressure is often negative due to lymphatic function, see. --JWSurf (talk) 00:49, 31 May 2009 (UTC)

Numerical Schrodinger solutions

Is this assumption that I'm making correct? If its not could anyone explain why? In an empirical method for the determination of electronic structure, the Schrodinger equation is written in terms of parameters chosen to agree with the experimental quantities. So, in density functional methods, can the schrodinger equation be solved numerically? Without needing parameters that appeal to experimental measurements? I appreciate thats a strange way of writing what I mean.....144.32.155.203 (talk) 14:05, 30 May 2009 (UTC)

You are asking too many questions at once... I think the best for you would be to read Density functional theory to understand what it is, and to read Hartree-Fock method and related methods to understand what the alternatives are. The simplest density-functional method is Thomas-Fermi model - it is really simple and intuitive. There are many good introductory-level quantum mechanics textbooks that cover both Thomas-Fermi and Hartree-Fock. Once you understand that, the rest will hopefully be easier. If you have any specific questions after you've done that - please don't hesitate to ask. As for "the Schrodinger equation is written in terms of parameters chosen to agree with the experimental quantities" - can you please be more specific? --Dr Dima (talk) 21:45, 30 May 2009 (UTC)

Is burnt food bad for you?

Someone claims that burnt food creates harmful free radicals inside the body. Does burnt food cause any harm, radically or otherwise? Vimescarrot (talk) 19:00, 30 May 2009 (UTC)

I think it does, but then so does pretty much everything else. BBQs are particularly nasty for carcinogens, I believe, but I still love them! Unless somebody gives you statistics regarding how many years eating burnt toast will, on average, take off your life, treat claims of it being harmful with a pinch of salt. The mechanism they describe is probably true - burnt food probably does contain free radicals and free radicals are harmful, but the human body has ways of dealing with harmful things, including free radicals (and, even better, free radicals give you an excuse to drink red wine, because apparently it contains anti-oxidants which deal with the free radicals!). --Tango (talk) 19:13, 30 May 2009 (UTC)

I should probably give you some links - Free radical#Free radicals in biology would be a good place to start if you want to find out more - lots of great links in there. --Tango (talk) 19:14, 30 May 2009 (UTC)

Wouldn't the pinch of salt also kill you? 213.122.2.54 (talk) 19:26, 30 May 2009 (UTC)

I would be less worried about free radicals per se than about polycyclic aromatic hydrocarbons, which tend to form when organic material is exposed to high temperatures. Benzo(a)pyrene in particular (should be benzo[a]pyrene but for technical reasons I think you can't wikilink that) is a nasty carcinogen. --Trovatore (talk) 20:06, 30 May 2009 (UTC)

Yes burnt food definately is, particularly burnt meat. Its not just the free radicals, but other seriously carcinogenic chemicals. Acrylamide is widespread in baked or fried food, and I wonder if it is doing us harm without it being detected due to its ubiquity, in the same way that lead did with the Romans without them being aware of its dangers because it was in everything. 78.144.254.133 (talk) 20:17, 30 May 2009 (UTC)

It's something I have wondered about, this is conjecture but my guess is people have evolved some defences against the stuff in burnt food and we're probably much more resistant to these chemicals than other animals. Anyway a possible investigation for someone. Dmcq (talk) 20:58, 30 May 2009 (UTC)

(Proto-)Humans have been cooking food (Control of fire by early humans) long enough for evolution to have built up a defence to it, so that's a highly plausible conjecture. --Tango (talk) 21:11, 30 May 2009 (UTC)

Actually I'd be much more interested if we haven't built any defences against them. I haven't the foggiest what that would mean. Dmcq (talk) 21:36, 30 May 2009 (UTC)

I guess it would mean either that the problem of defending against these carcinogens biologically is an obstructively complex one compared to others solved by human evolution over the same time period, or else that the carcinogens don't kill significant numbers of people until old age, at which point throughout most of the time period in question we'd be dead anyway (or too old to breed would also do the trick, if there is such a thing). 213.122.49.104 (talk) 22:01, 30 May 2009 (UTC)

Or that burnt food doesn't offer a significantly greater risk than the numerous other causes of free radicals, so all animals already have the defences necessary. --Tango (talk) 00:29, 31 May 2009 (UTC)

Tango, keep up. It's not free radicals. It's polycyclic aromatic hydrocarbons.

Anyway, according to our article, there are specific defenses against benzo[a]pyrene, which after all occurs all over the place, not just in your barbecue but anywhere organic matter burns. --Trovatore (talk) 00:46, 31 May 2009 (UTC)

I'm surprised no one has pointed this out yet, but in addition to the polycyclic aromatic hydrocarbons and carcinogens and such, burned food tastes really nasty. - Sticking to Chocolate —Preceding unsigned comment added by 66.215.227.218 (talk) 21:42, 30 May 2009 (UTC)

Burnt chocolate is the worst - don't melt chocolate in a microwave, take the extra couple of minutes to do it properly over a bowl of hot water! --Tango (talk) 00:29, 31 May 2009 (UTC)

Burnt food is awesome. If my mother tells me my food is cooked, I tell her to leave it in for another ten minutes...which is why I asked this question. Vimescarrot (talk) 00:50, 31 May 2009 (UTC)

I don't care for burned food in general, but there are a few exceptions. Sharp cheddar cheese is very nice cooked to a slightly brown crust. When I make a pasta sauce from red bell peppers, I find that it comes out sweeter if I sautée them with the garlic and hot pepper until there are black spots on the skin of a few of them, before I put in the wine and veggie juice (which brings down the temperature). A similar principle applies to eggplant. --Trovatore (talk) 01:57, 31 May 2009 (UTC)

I'm actually very fond myself of the crusty edges at the corners of pans - someone actually made a maze-like baking pan in which everything would come out with crusty edges, and I so want to get one! But actual BURNT food - nah! I suppose it depends what you call "burnt." What I call toast, my brother calls "warm bread." What my brother calls toast, I call "charcoal." Each to his or her own, I suppose. - Sticking to Crusty Chocolate Brownies and Warm Bread —Preceding unsigned comment added by 66.215.227.218 (talk) 04:25, 31 May 2009 (UTC)

Thanks Trovatore for the Benzo(a)pyrene reference. So all mammals can deal with burnt food to some extent. The enzymes to do this are part of the very wide ranging Cytochrome P450 family and seemingly mice have more than twice as many genes for this family as people. Sounds like mice should thrive on welsh rarebit and the burnt edges of pie dishes. :) Dmcq (talk) 08:20, 31 May 2009 (UTC)

I think it's also worth emphasizing that protective measures selected during evolution might not be expected to prevent complications like cancer after childbearing years. This is a simplification, but not a worse simplification than the notion that it's safer to eat carcinogens because we have some protections against them. --Scray (talk) 14:30, 31 May 2009 (UTC)

It depends on the kind of food. Burnt fat gives barbecued meat a lot of its flavor, and burnt sugar, if not too badly burnt, is caramel. Burnt protein, though, is nasty. I too have heard that burnt fat can be carcinogenic, but don't know a source for the facts. Looie496 (talk) 18:04, 31 May 2009 (UTC)

It is I believe a scientific fact that a proportion of cancers are caused by the wrong kind of diet. If evolution has not protected us against that, or many other lethal illnesses such as heart disease or (formerly) diabetes, why should it protect us against burnt food? 89.240.58.231 (talk) 18:47, 31 May 2009 (UTC)

Perhaps because those wrong kinds of diets have only been around for a few tens to a few thousands of years, giving natural selection insufficient time to adapt populations to them, whereas diets incorporating burnt meat have been around for at least several hundred thousand years, as Dmcq and Tango suggested. Remember also that evolution mostly works by people with the less adaptive genes dying before they reproduce, hence naturally selecting in favour of the ones who have better adaptive genes: diseases that mostly affect people over, say, 40 are not very succeptible to natural selection, as .104 and Scray indicated. 87.81.230.195 (talk) 19:07, 31 May 2009 (UTC)

See Charcoal biscuit for beneficial use of "burnt" substances in your food. Eating soil by the shovel load is really bad for you. But a bit of certain kinds of clay can be quite healthy (surprise, surprise:-) You should remember that cooking food gets rid of a couple of nasty pathogens and parasites. Natural selection isn't going to help solve this puzzle as others above have indicated. Ultimately you are going to die of some form of cancer ... if you don't die of something else first. 71.236.26.74 (talk) 07:11, 1 June 2009 (UTC)

Storage capacity of the human brain, in gigabytes?

Remember the 1995 movie "Johnny Mnemonic," about the guy with the 160-GB data transport device implanted in his head? (Neither do I; I changed the channel after the first 15 minutes.) But today, something (OK, it was the fact that I found my keychain in the washer after doing my laundry, with my 512-MB thumb drive attached) made me think about how just a few decades ago, even the experts would never have thought that ordinary folk would need half a gig of storage capacity for personal use, let alone that it could fit in the pocket of a pair of shorts. And that brought back what I thought when I was trying to watch "Johnny Mnemonic": 160 GB may have been huge back in 1995 (as they implied), but even today the most amazing computers can't do what the human brain has been doing much better all along. Arguably the human brain is (and probably always will be) the most sophisticated computer yet devised: both the brain and computers as we know them require a sophisticated network of components devoted to specific tasks, relay information via electrical impulses, and process new messages/stored information via symbolic coding of sorts (be it "110=green pixel" or "your-cheating-ex's-perfume=adrenalin=angry"). What I'm wondering is, if the human brain were a computer, made of the materials and with the technology we have, what would its specs and storage capacity be? Has anyone ever calculated this? (P.S. Don't lose that protective cap that goes over the end of your thumb drive. Turns out, it's waterproof.) - AJ —Preceding unsigned comment added by 66.215.227.218 (talk) 21:30, 30 May 2009 (UTC)

This article makes a reasonable estimation. In summary, it proposes the brain is like a 168,0000 MHz Pentium computer by scaling up from an estimate of the processing power of the retina, which can transmit ten one-million-point images per second. This is likely a huge underestimation because the brain does a much more complex job, in terms of parallel processing, than a retina. But it is probably a reasonable minimum value. In terms of memory, they propose the average brain could hold about 100 million megabytes, based on total synapse estimation. This doesn't account for neuroplasticity, however, and how that modifies storage capacity is difficult to estimate (since we don't really understand it biologically yet). Rockpocket 21:46, 30 May 2009 (UTC)

The problem is, we don't really know how the brain works. We have some idea, but it does not make a comparison to a digital computer any easier. Problem #1: the brain uses a wide varety of coding strategies (population, rate, combinatorial, spike timing, etc...) while the digital computer uses only two (parallel binary and sequential binary). Problem #2: data processing in brain is not synchronous. Problem #3: for a data flow within the digital computer, Shannon information is well defined; for the "data" flow within the brain, it is not (for example, the more precisely you specify the spike timing the more "information" you find). Problem #4: the state of the digital computer is uniquely defined at any given moment, and there are only 2^(number of the gates) possible states. Not so for the brain, unless you count every sub-unit of every ion channel as a separate gate. And so on... --Dr Dima (talk) 22:02, 30 May 2009 (UTC)

Both you and the article say "168,0000 Mhz". Do you mean 168,000 Mhz or do you mean 1.680.000 Mhz? The figure I get from the numbers given in the article is 16,800,000 Mhz. 89.240.58.231 (talk) 18:58, 31 May 2009 (UTC)

I mean what the article said, since that was where I cut and pasted it from. I didn't do the calculation myself. Looking at it again, it is a very weird way or writing it though, so I guess your calculation might be correct and they made a typo. Rockpocket 03:30, 1 June 2009 (UTC)

Thanks, Rockpocket - that was an excellent article! Unfortuantely, it was outdated by about 10 years, making it hard to compare the human brain with the latest in computer technology, since I don't know what the very latest and greatest human creations are capable of. Still, I have no doubt the human brain is still the clear winner when it comes to sheer capacity, if not always speed. Still, artificial intelligence is a very interesting field - it's always interesting to see how AI and psychology have taken from and built off of each other. Even the old dualistic talk of the "ghost in the machine" acknowledged that there had, in fact, to be a machine for the ghost to operate - and whether there's any spiritual dimension to our consciousness or not, everything that we are and do does in fact exist in the brain in some way. On the other hand, as a big fan of The Sims and its sequels, it's funny and a tad ironic to dive into the programs' inner workings and see how some of the most apparently natural humanlike behavior is brought about through the most mechanical and artificial ways . . . Dr Dima, you raise some excellent points. I'm very aware that we don't understand exactly how the brain works - a fact which brings me endless wonder (and frustration!). I don't claim that the computer and the brain are exactly parallel - only that there are enough similarities to make the comparison, and my question, compelling. As for the possibility for counting every sub-unit of every ion channel as a separate gate . . . Data storage, even by computers, need not be digital. There is such a thing as a "trit," or trinary bit, with three possible states, so the brain may have any number of possible states. . . . Obviously the state of the brain is "uniquely defined at any given moment" in some way - the way my brain now is the result of its unique chemical composition, history, and recent input, and were those exact data to be duplicated in your brain, or in my brain at some future time, you or my future self would experience this precise moment I'm having now. Strong emotional flashback memories, or even recurring dreams, demonstrate the abilty of the brain to reproduce at least partially a previous state. Furthermore, what's to say that there *aren't* a finite number of brain states? After all, there are definitely a finite number of computer states, but their capacity is great enough that no two computers (not counting networks, etc.) are in exactly the same state. As a writer, I type things all the time that have never been typed before. Sometimes I even share my writing with friends - and if I've been successful, my choice of words will stir up in them the same things I was feeling when I sat down to write - experiencing a few of the same cognitive patterns. Yes, it's *very* complicated, and I realize that I can't expect a definitive answer to this question. But it's sure fun to think about, and to explore the parallels and divergences while we're at it. - AJ —Preceding unsigned comment added by 66.215.227.218 (talk) 22:42, 30 May 2009 (UTC)

For a discussion, see Technological singularity and related articles. For the "latest" computers, see Supercomputer. -Arch dude (talk) 01:26, 31 May 2009 (UTC)

Thank you! Unfortunately, the specs for the supercomputers are given in FLOPS instead of MIPS, but at least after searching around a bit I was able to compare the human brain to my own desktop PC. (Of course, I'm really going to feel stupid now next time it gets the better of me, which still happens once in a while!) - AJ, Clearly the Better Machine —Preceding unsigned comment added by 66.215.227.218 (talk) 04:44, 31 May 2009 (UTC)

Most of the computers we used are based on a Von Neumann architecture. This is the sort of thing that looks so obvious to anyone who uses computers that it's hard to remember why it was so ground-breaking—you keep the memory in one area, the input/output in another, have another part for doing the logics, have another part for taking care of the operations, etc. It's a great way to design a piece of hardware—each component can be relatively independent of each other, so when your hard drive crashes you just put in a new one, and all is well. But as far as I can tell it's a lousy model of the human brain (which is not it's fault—it wasn't trying to be one). While it's clear that our brain has specialized sub-organs for handling different types of "processing" (language centers are particularly conspicuous in this regard—if you suffer damage to them, you suddenly can't do certain types of language operations), it seems fairly clear that all parts of the brain are suffused with some aspects of all of the other components, and the divisions between these sub-organs appear somewhat fluid.

I sort of see digital computers and wetware processing as apples and oranges. There are a few ways in which they can interface but they aren't the same architecture. They have superficial similarities—like a dolphin and a tuna fish do—but they operate on quite different means. I think the computer metaphor probably does more harm in understanding how the brain works than it does good. (But I'm not an expert at this, just someone who has read a few books here and there.) --98.217.14.211 (talk) 14:24, 31 May 2009 (UTC)

It is tricky to think in terms of the brain as a piece of electronics because they work very differently. The brain has relatively few cells and an awful lot of 'wiring'. Each cell has thousands of connections out to other cells. Cells (and the connections between them) work VERY slowly compared to the logic gates in a computer...a million times slower. In a computer, the nearest thing to a "cell" might be a logic gate (AND,OR,NOT,XOR,etc) - it takes a couple of gates to make a memory bit and thousands of gates to make (say) a 32 bit floating point addition unit. But the computer has much, much less wiring. Most gates have only two or three wires going to them...and they are a few million times faster than a cell. Furthermore - in the computer, only a fraction of the gates inside the CPU are switching at any given moment - and barely a handful of the memory bits are switching on each clock cycle. By contrast, most of the cells in the brain are firing all the time.

Comparing a large, slow, vastly-interconnected, highly active "biological machine" with a small, fast, minimally-connected, rarely-switching one is very difficult - the comparisons just don't make sense numerically.

However, we can do this: With a digital computer, we can write software that emulates a brain...'neural network' software can simulate what happens at the neuron level in the brain. So we could ask how much of a 'brain' could a modern computer simulate? I did some calculations here a while back that suggested that the speed of neural network software running on a PC is about a factor of a billion short of a real brain...that's actually not very much. I believe (on that basis) that if Moore's law continues at it's present rate (doubling the performance of computers every year) then in about 25 to 30 years - with a warehouse-full of a few million bucks worth of electronics (something like Google's massive computer farm) - I think we could build a complete simulation of a human brain - accurate and functional.

But using a computer to simulate a brain is a severe mis-use of it's resources. If you try to do the reverse and use a brain to simulate a computer (something I often have to do when I'm debugging a computer program by following it through line-by-line) - I'd be lucky (even with support of pencil and paper) to run one line of software per second. That makes my brain a few billion times slower than a real computer - with a few billion times less 'fast RAM'.

So if a modern PC is a billion times 'less' than a brain when simulating a brain. And my brain is a billion times 'less' than a PC when simulating a PC...what can we truly say about their comparable performance? You could argue that by some bizarre kind of averaging - they are about the same. But that's not right. So what about some actual experiments?

I like to do this one. Imagine somewhere in your home where you have a shelf - maybe in the garage, full of paint cans and such. Now - imagine that the bracket holding the shelf up at one end were to fail - what would happen? I'm sure you can imagine the rapid sliding of everything off one end - a big pile of stuff on the floor - some of the lids came off of the paint cans - so there is a spreading puddle of paint - maybe colors mixing and flowing together. You did this "calculation" in a fraction of a second. The results are horribly inaccurate - you don't know the precise positions of the paint cans or exactly where the paint will be distributed...but you know the important parts of the answer AMAZINGLY quickly. Doing that same thing inside a computer would take weeks of CPU time. The results would be much more accurate (but not perfectly so) - but the essential useful data (did it make a horrible mess?) is still there.

So in doing that kind of calculation, our brains are vastly more efficient than computers.

On the other hand - the time it would take you to divide two hundred-digit numbers in your head - and get a result accurate to two hundred digits - is similarly wildly different from the time the PC would take to do the same thing. Even 'savants' who can actually do this kind of thing take a long time.

This is a measure of how the differences between the design of (and demands upon) brains and computers is so different that we really can't come up with a scale of comparison...not numerically, not functionally.

SteveBaker (talk) 17:59, 31 May 2009 (UTC)

light acting like a solid

Hi

I read somewhere about someone producing light that could act like a matter to some degree, I know that it doesn't mean we are gona make green lantern rings or something, but is this true, and if it is how does it work and to what extent, just quantum size or perhaps a new kind of optical levitation for micro chips.

Thank you

Rob —Preceding unsigned comment added by 79.68.182.166 (talk) 23:03, 30 May 2009 (UTC)

The Z boson possibly? SpinningSpark 01:59, 31 May 2009 (UTC)

Preempting my reply with the caveat that I don't really fully understand quantum mechanics myself, I was under the impression that the idea behind wave–particle duality was that all light (energy) showed matter-like properties, and vice versa. Rockpocket 02:05, 31 May 2009 (UTC)

It can behave like a particle (photon) but not like solid matter the way I think you are getting at. -RunningOnBrains^{(talk page)} 02:20, 31 May 2009 (UTC)

As I understand things, since photons have energy, they also have mass and momentum. When photons are absorbed by or reflect off of other objects, those objects react. See radiation pressure and solar sail. -- Tcncv (talk) 04:51, 31 May 2009 (UTC)

Photons do not under any circumstances have mass. They have energy, they have momentum, and they can behave like a particle, but they are explicitly and exactly zero mass. Nimur (talk) 18:36, 31 May 2009 (UTC)

Wikipedia article: Lene_Hau claims she changed light to matter which I believe is an oversimplifaction of her experiments with Bose–Einstein condensate --Digrpat (talk) 04:41, 31 May 2009 (UTC)

Judging from the paper abstract and the Scientific American article, what they did is transfer a qubit from a photon to some sort of matter substrate and then to another photon. That sounds like it might be useful for quantum computing, but it doesn't make the light act like matter. -- BenRG (talk) 10:27, 31 May 2009 (UTC)

Perhaps I should have expanded on my answer a little, the Z boson, like the photon of light, is a boson that mediates a force. Like the photon it carries no charges. The difference is that the mass of the photon is zero while that of the Z boson is very large. For that reason, the Z boson is sometimes described, rather inaccurately, as "heavy light". SpinningSpark 09:56, 31 May 2009 (UTC)

To be completely clear - the photon has no REST mass - but moving at the speed of light, it does indeed have mass (as it must because it has energy and E=mc²). But the line between 'light' and 'matter' is a fuzzy one. We can regard photons as particles - and we can regard electrons, neutrons and protons as waves. We can (if we choose) regard a 1972 VW bug as a wave! But in terms of shining a laser beam and somehow making it 'hard' so you could hit it without your hand going right through it - no. There is no way for that to happen. However, the same thing is true for a beam of alpha radiation (helium nucleii) or beta radiation (electrons). The idea of "hard light" that the authors of StarTrek talk about in the holodeck of the starship Enterprise is pure fiction. SteveBaker (talk) 17:34, 31 May 2009 (UTC)

To be clear, what Steve is calling "mass" is "relativistic mass", which isn't a concept used much in modern physics. It's a useful way of getting your head round this kind of stuff, but isn't actually useful for doing anything. "mass" in modern terminology means "rest mass". The key thing which stops light being "hard" isn't that it isn't matter (it is, for sufficient intents and purposes), it's that there are no bonds between photons. Solid matter is lots of particles bonded together, a beam of light is just lots of particles. (Star Trek holodecks use "force fields" to make things hard, the term "hard light" appears in Red Dwarf in reference to holograms, though, perhaps you were thinking of that?) --Tango (talk) 17:52, 31 May 2009 (UTC)

The reason that this concept is not much used in modern physics is because it misrepresents the equation (E=mc^2), and encourages its use in situations that do not apply. Making a clear distinction between mass and energy is important to correctly understand that they are interchangeable, (via nuclear processes, for example), but they are not equivalent in every circumstance. (Matter can be converted back and forth to energy, but it is not the same thing as energy - the key difference being the presence or absence of mass. This dramatically affects the physical processes which can and do occur). Nimur (talk) 18:44, 31 May 2009 (UTC)

Thank you for clarifying. I should not have used the unqualified term mass when I meant relativistic mass, which itself is a questionable concept. I would have been better to relate energy directly to momentum. -- Tcncv (talk) 18:33, 31 May 2009 (UTC)