Wikipedia:Reference desk/Archives/Science/2012 January 29

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January 29

Terminology question

Suppose you have a measurable quantity of some kind, such as 123 MWh of energy. This is the same as 123 thousand kWh. The "MWh" and "kWh" bits are called units, but what are the "123" and "123 thousand" bits called? JIP | Talk 00:27, 29 January 2012 (UTC)

Quantity? --Mr.98 (talk) 00:59, 29 January 2012 (UTC)

But isn't the whole thing called a quantity? I am asking specifically about the bit with the numbers. Changing that bit without also changing the unit would change the overall amount of energy. JIP | Talk 01:02, 29 January 2012 (UTC)

Numerical value. From WP: "the value of a physical quantity q is expressed as the product of a numerical value Nq and a unit of measurement uq" 88.26.74.157 (talk) 01:08, 29 January 2012 (UTC)

88.26 is quoting from Physical quantity#Definition of a physical quantity. -- ToE 02:56, 29 January 2012 (UTC)

Artificial melatonin

How can melatonin be synthesized artificially? I wanted to know both chemically and extracting it from plants. 88.26.74.157 (talk) 01:04, 29 January 2012 (UTC)

Note that if it's extracted from plants, it's natural, not artificial. StuRat (talk) 01:13, 29 January 2012 (UTC)

OK, I meant, not naturally produced in humans (the melatonin from pills). 88.26.74.157 (talk) 01:15, 29 January 2012 (UTC)

Three processes of chemical synthesis are shown here. Hmmm ... Firefox is telling me the site is untrusted, so proceed at your own risk. Clarityfiend (talk) 02:03, 29 January 2012 (UTC)

So chemistry sites are unsafe ? Good thing I limit my web browsing to Eastern European porn sites. :-) StuRat (talk) 03:34, 29 January 2012 (UTC)

That's it, time for a spanking! Whoop whoop pull up ^{Bitching Betty | Averted crashes} 05:22, 29 January 2012 (UTC)

That would be a case of "whoop whoop pull down." :) ←Baseball Bugs ^{What's up, Doc?} carrots→ 06:19, 29 January 2012 (UTC)

Whoop whoop pull up ^{Bitching Betty | Averted crashes} 06:32, 29 January 2012 (UTC)

Horses in roller skates

Would it be possible to fit specially shaped roller skates onto a horse's feet to allow it to move faster? Whoop whoop pull up ^{Bitching Betty | Averted crashes} 05:18, 29 January 2012 (UTC)

Fitting them would be no problem, but training a horse to roller skate would be difficult, perhaps impossible. You might be able to do it, if you put them on the horse from birth (putting on larger ones as needed).StuRat (talk) 05:35, 29 January 2012 (UTC)

According to Inline speed skating, rollerblading a "metric mile" is about 50 percent faster than running it would be. Here's the problem, though: rollerblades complement the way humans run, which is on two feet combined with arm-swinging. Horses don't have arms to swing and help them keep their balance. The side-to-side thing would be totally unnatural for a horse. It might be interesting to try, though. ←Baseball Bugs ^{What's up, Doc?} carrots→ 06:33, 29 January 2012 (UTC)

I googled [horse on roller skates], and a number of things came up, including this somewhat nondescript picture,[1] but I suggest you do some googling and see what you can find. The point being, it's been done. Whether it's faster than running, I couldn't say. But obviously it would have to be done on a paved surface. Roller blades don't usually do well on turf or earth. ←Baseball Bugs ^{What's up, Doc?} carrots→ 06:37, 29 January 2012 (UTC)

LIFE magazine ends the magazine with a "Miscellanny" picture. The first "Miscellanny" picture was a horse on rollerskates, Jimmy, he appeared in the May 19, 1952 issue. But no-one cares about Jimmy anymore, because now we have Tarra. Even parrots try to imitate Tarra. After a lot of training some cockatoo's can rollerskate pretty quickly. Abused monkeys rollerskate too. If you torture a bear long enough he can skate on ice. I don't think fish rollerskate, they usually prefer skateboarding, just like dogs. Dogs like surfing too. This planet is pretty weird. Did you see this ass called Pinky? Search for "Pinky" on this page, maybe you can find video. Here are the newspaper 1 and newspaper 2. extra info. Pinky was probably painted pink. Von Restorff (talk) 07:22, 29 January 2012 (UTC)

My chief concern with trying that would be the risk of the horse breaking legs, which usually ends in the death of the horse. Falconus^{p t c} 15:04, 29 January 2012 (UTC)

Jimmy! That rolls back memories. Here you can see him horsing around on skates -so to speak. It start just after 6 minutes in. I've Got A Secret - Easter Parade (2/3). It's not the horse but the panel of celebrities that appear to be worried about breaking a leg - their own.--Aspro (talk) 17:01, 29 January 2012 (UTC)

Anecdotes...

OK, I can't ignore this, too many bad memories...

• Much like today's problems involving a spherical cow, when I was in high school Physics, it was guaranteed that on every Mechanics exam, there was one question which began, A horse on frictionless roller skates is moving at [N] m/s..."
• It also seems that this piece of "Bumper sticker wisdom" applies: Never try to teach a pig to sing. It wastes your time, and annoys the pig.

--DaHorsesMouth (talk) 22:20, 29 January 2012 (UTC)

diabete melitus

is diabetes mellittus a x-linked character? if not on which chromosome is its character present? — Preceding unsigned comment added by 123.201.155.125 (talk) 11:50, 29 January 2012 (UTC)

See Diabetes mellitus type 1#Genetics and Genetic causes of diabetes mellitus type 2. Red Act (talk) 12:03, 29 January 2012 (UTC)

If everything is heavier than the air we breathe why do clouds and fog ( which are water droplets) apparently FLOAT ?

Floating clouds and fog- how are they supported. ? — Preceding unsigned comment added by Swavcrewson8 (talk • contribs) 13:35, 29 January 2012 (UTC)

Not everything is heavier than air; e.g. helium. Read this article. Von Restorff (talk) 13:47, 29 January 2012 (UTC)

Same reason why ships float and don't sink? Lynch7 13:48, 29 January 2012 (UTC)

Nope. Read Displacement (ship). Von Restorff (talk) 13:52, 29 January 2012 (UTC)

My chemistry lab instructor would always point out that we shouldn't leave a beaker upside down in a rack to dry as water vapor (H₂O at 2(1) + 16 = 18 g/mol) is lighter than air (roughly 80% N₂ + 20% O₂ at 0.80 (2) 14 + 0.2 (2) 16 = 0.8 * 28 + 0.2 * 32 = 28.8 g/mol). I always figured that there must be an optimum time to leave the beaker upside down so that as much liquid water as possible will drain out before inverting it to air dry the rest of the way; I doubt that such a time would be much more than a minute. The OP may also be interested in reading Density of air#Water vapor which explains why humid air is actually lighter than dryer air, a fact counterintuitive to many who feel hot, heavy air "weighing down on them", but an important fact for pilots as planes have less lift in less dense air and thus need longer takeoff rolls when it is hot, humid, or low pressure (either from weather or, more importantly, altitude). -- ToE 14:50, 29 January 2012 (UTC)

That's a very good point, and explains why the layer of humid air containing the clouds will float. Of course, individual droplets of water that we see (i.e. clouds) are heavier than air, but they fall so slowly due to air resistance that they can't get to the ground - until they join up to be big enough, at which point the rain most assuredly comes down. Wnt (talk) 16:12, 29 January 2012 (UTC)

That reason for not inverting beakers seems a bit silly, as the natural tendency of water vapor to diffuse will greatly outweigh any density differences, at that scale. I would invert them, both to let water drain out, and to keep dust from settling inside. This is particularly important if they are to be used for biology cultures, as that dust will inevitably contain bacteria. (Of course, the beakers really should be sterilized better than that, and not be allowed to air dry at all, but in a school lab they may not have the expensive equipment to do it properly.) StuRat (talk) 18:18, 29 January 2012 (UTC)

The chemical term is suspension. (Or, if the water droplets are small enough, an aerosol.) Firstly, due to square-cube effects, as you decrease the size of the droplet, air resistance becomes proportionally much larger when compared to the force of gravity, meaning that small droplets fall slower than larger droplets. Cloud droplets are very small, and thus take much longer to settle out than rain droplets. Also, below a certain size, the random drift of the droplets due to brownian motion is larger in size than the slow settling due to gravity, effectively keeping them "permanently" suspended in still air. But again, air is rarely still, and clouds typically form when warm, moist air rises as a mass, and then cools enough to for the water to condense. This bulk rising also can serve to keep clouds afloat, or even cause them to rise further. -- 67.40.215.173 (talk) 20:08, 29 January 2012 (UTC)

Sleep deprivation

Why is it that, after missing a full eight hours of sleep, a nap of only three hours or so plus sunlight and a meal is enough to leave me perfectly revivified? Whoop whoop pull up ^{Bitching Betty | Averted crashes} 17:57, 29 January 2012 (UTC)

It won't, actually -- if you tried to do that every day, you would find yourself suffering in the long run. But generally speaking, the relationship between sleep, time of day, light, and alertness is quite complex and far from completely understood. Our article on circadian rhythms contains some useful information, but I won't pretend that it fully answers the question. Looie496 (talk) 18:08, 29 January 2012 (UTC)

Agreed. Our bodies are designed to operate on limited hours of sleep, on occasion, but not full time. StuRat (talk) 18:11, 29 January 2012 (UTC)

Hopefully it leaves you "revived", not "revivified". StuRat (talk) 18:09, 29 January 2012 (UTC)

Yeah, I meant "revived", Stewed Rat. Whoop whoop pull up ^{Bitching Betty | Averted crashes} 18:15, 29 January 2012 (UTC)

I knew a guy who stayed awake 7 days straight, and was fine after 8 hours of sleep. by constrast, I feel cruddy after sleeping a few hours each of several consecutive nights. Heck froze over (talk) 18:46, 29 January 2012 (UTC)

Note that they may have only appear to be fine, the long-term consequences of sleep deprivation are fairly well documented. StuRat (talk) 19:23, 29 January 2012 (UTC)

Feeling awake doesn't mean that you are indeed equally able to perform any task. Self-assessment of your cognitive abilities is tricky, since you are employing your own cognitive abilities, which could be impaired. Do not try to drive under such conditions, since your body could ask you for some microsleep. 88.26.74.157 (talk) 20:01, 29 January 2012 (UTC)

• I work in a 24 hour a day business, and I can tell you that I have most certainly seen the negative effects of long term sleep deprivation with my own eyes. New night shift workers will often try to stay up during the day as well, either to hang out with friends or even to do another job. I've honestly seen people lose their minds doing this, they become extremely irritable and irrational and stop paying attention to details. I even had one guy come up to me several months after I fired him for such behavior and thank me for letting him go because he believed he was on the verge of psychosis caused by sleep deprivation. Beeblebrox (talk) 20:17, 29 January 2012 (UTC)
  • As noted in Fatal familial insomnia, which is the absolute worst form of sleep deprivation, namely that you can't sleep at all, sleep deprivation can ultimately lead to dementia and death. ←Baseball Bugs ^{What's up, Doc?} carrots→ 23:50, 29 January 2012 (UTC)

If you work out vigorously almost every day, like running fast for half an hour or longer, you will feel the difference between getting a proper amount of sleep at night or just napping for a few hours, already after a few times. Count Iblis (talk) 00:34, 30 January 2012 (UTC)

See sleep debt. ~AH1 ^(discuss!) 16:52, 31 January 2012 (UTC)

Incandescent light bulb self limiting current?

In the Incandescent light bulb one of the references says "Edison's research team was aware of the large negative temperature coefficient of resistance of possible lamp filament materials and worked extensively during the period 1878–1879 on devising an automatic regulator or ballast to stabilize current. It wasn't until 1879 that it was realized a self-limiting lamp could be built.". So how come the lamp is self-limiting?, and would the lamp life be extended if the lamp were current controlled? Electron9 (talk) 17:59, 29 January 2012 (UTC)

As the 'newer' bulb's 'tungsten' filament gets hotter so the resistance goes up (positive coefficient), with say silicon (transistors, glass bottles etc.) and carbon it goes down. This is a poor example on youtube but it was all I could find quickly. [2]. Early Wirelesses often used a bulb to regulate the current because the poor power regulation of mains electricity. Uranium is another element used to regulate current as its resistance go up when too much juice goes through it. The early carbon filaments had a negative coefficient -thus the need to regulate the current.--Aspro (talk) 18:31, 29 January 2012 (UTC)

This clip demonstrates the negative coefficient of glass which at room temperature is normally a pretty good insulator but heat it up and its resistance goes way down and so starts to absorb microwaves very well . [3]

Hey thanks! An instance of melted Pyrex in the microwave was one of the Great Mysteries - and this provides the explanation. Wnt (talk) 01:35, 30 January 2012 (UTC)

It wasn't a Great Mystery to the wife – she simply clouted me with a rolling pin. But your support is most welcome.--Aspro (talk) 22:27, 31 January 2012 (UTC) --Aspro (talk) 22:27, 31 January 2012 (UTC)

Ships flying out of water

Can a large explosion really lift a large destroyer completely out of the water? Whoop whoop pull up ^{Bitching Betty | Averted crashes} 18:01, 29 January 2012 (UTC)

“completely' is maybe a bit of a euphemism. This clip is of a torpedo stick and the ship certainly rises some what.[4] A magazine explosion would be worse. Merchant ships carrying munitions have been reported to come out of the water when their cargo explodes but of the footage I can recall, the blast obliterates the ship making it impossible to tell. I would suggest that the bow and stern would blow fore and aft without leaving the water completely. The energy however, would be sufficient to raise it several miles if it was all applied evenly from beneath the keel.--Aspro (talk) 19:14, 29 January 2012 (UTC)

A Type 45 destroyer has a mass of about 8000 tonnes. Ignoring buoyancy and using the formula E=mgh, we find that it would take 78 Megajoules to lift it one metre. A tonne of TNT releases 4.2 Gigajoules, so could (if all the energy could somehow be used to lift it) lift the destroyer 54 metres. The Father of All Bombs, which is apparently the largest non-nuclear bomb, is equivalent to 44 tonnes of TNT. If you could get all of that energy to lift the ship, it would go 2.4 km (1.5 miles) into the air. Of course, you couldn't actually get all that energy to lift the ship, a lot of it would go down and sideways and a lot of it would go into destroying the ship rather than lifting it. If you really wanted to, you could probably get it to lift a metre of two clear of the water with a perfectly placed explosion. --Tango (talk) 22:52, 29 January 2012 (UTC)

There's some evidence that the Operation Crossroads nuclear test blew the USS Arkansas right out of the water. Mildly Mad^T_C 17:30, 30 January 2012 (UTC)

Nukeproof armor

Is there any known or hypothetical material which can shield a person from an atomic bomb detonating right next to them? Whoop whoop pull up ^{Bitching Betty | Averted crashes} 18:13, 29 January 2012 (UTC)

Depends on the size of the nuke and how close. A Hiroshima-sized nuke could be defended against with little more than a conventional bomb shelter, even at ground zero (directly below the air burst). If you were sitting atop the Tsar Bomba when it was detonated, though, you should kiss your ass goodbye. StuRat (talk) 19:17, 29 January 2012 (UTC)

I am not sure that a conventional bomb shelter would defend you against being directly below a nuclear detonation. Even if the structure was not crushed by the overpressures (which is not impossible, depending on the construction), the heat and radiation would be extreme. You'd roast. Put another way: a suitable rugged structure, like the Hiroshima Genbaku Dome, might survive such a blast (that building benefited by being directly under the explosion, because the forces on it were primarily vertical, which preserved many of the walls). But nobody inside it would likely survive. You'd need really much more than your conventional bomb shelter to take a direct hit with an atomic bomb of almost any militarily significant size. Even direct hits from conventional bombs can destroy conventional bomb shelters. Fallout shelters were not about surviving direct hits — they were about surviving misses or the effects of bombs some distances off, or avoiding residual radiation. They were meant to save some lucky lives, not all lives. Many of them would have just served as kettles for their occupants, as was the case of shelters used in the firebombings of Dresden. --Mr.98 (talk) 22:23, 29 January 2012 (UTC)

You don't need to be far underground to be protected from heat and radiation. Air is another problem, though, as you wouldn't be able to get breathable air from above for some time. So, oxygen tanks would be needed, and water. You could likely be rescued before a lack of food would kill you. StuRat (talk) 03:48, 30 January 2012 (UTC)

It is not that theoretically hard when considering small tactical weapons. As Project Orion discovered, only a few millimetres of a strong shield gets to be eroded by the heat. Next problem: one needs sufficient 'mass' to resist the force to stop the occupants inside from being bounced around to a pulp. Nuclear bunkers are provided with very thick walls of hard zinc cement (like what your dentist uses – if you can afford visit one) reinforced with tungsten rods – all of which weighs many thousands of tons. On the inside, on the upper floors and ceilings, they often apply an epoxy composite layer, of about a foot in thickness. This both stops the concrete spalling off and hitting people, as well as absorbing any neutron radiation that gets through (and prevents some Bremsstrahlung being created as well perhaps). Of course, a poor man's equivalent, is to just use the closest Kelvinator or equivalent - as demonstrated in this clip by Mr. Jones. [5] Don't try this at home kiddies- they don't open from the inside. Hope this helps and are you asking because you’ve heard something on Fox news that we haven't?--Aspro (talk) 20:06, 29 January 2012 (UTC)

Most modern refrigerators do open from the inside, in that they are only held shut with a magnet, and can be pushed open from the inside easily. It's the old ones with latches that killed kids. StuRat (talk) 20:20, 29 January 2012 (UTC)

A lot of those fridges are still around in the world (they never brake down) and how is your magnet going to keep the door shut. It wouldn't even happen in the movies ;-) --Aspro (talk) 20:48, 29 January 2012 (UTC)

They are also angled so gravity holds the door shut, and the magnet doesn't have to do much, just keeps it from bouncing back open when closed (I've had some fridges with weak magnets that do bounce back open). Also, I'd put the brakes on that spelling of "break". :-) StuRat (talk) 22:02, 29 January 2012 (UTC)

There are three main effects from the atomic bomb: pressure, heat, and radiation. It's a lot of radiation we're talking about "right next" to the exploding bomb, so a few inches of lead ain't gonna do it. The heat is going to be extreme — millions of degrees celsius. The pressure is quite a lot. So one could imagine being in some sort of container that is going to be blasted into the distance — that's probably your best bet. But you'd still probably die from one thing or another. I think many of the posters above underestimate the amount of energy were talking about here. It's orders of magnitude more than what human beings are used to dealing with. Project Orion is paradoxically misleading on this front. If by "material" you mean, "an elaborately constructed giant spaceship that is designed to translate that energy into thrust," then sure. But that isn't "nuke-proof armor." It's a spaceship. The answer is more or less "no." You can imagine some setups where you could make some sort of container that might help with survival in that it would blast you out of the area once the bomb hit, but that would be pretty dang contrived, and require you to know a lot about the size and location of said bomb ahead of time to have any confidence in it working. In my opinion, the best nukeproof armor you could have would be the live children of whomever has the nukes! --Mr.98 (talk) 22:26, 29 January 2012 (UTC)

According to our Atomic bombings of Hiroshima and Nagasaki article; "Eizo Nomura (野村 英三, Nomura Eizō?) was the closest known survivor, who was in the basement of a reinforced concrete building (it remained as the Rest House after the war) only 170 m (560 ft) from ground zero (the hypocenter) at the time of the attack" (Hiroshima). He was in a concrete box though, rather than a suit of armour. Also nuclear weapons make a much bigger bang these days. Alansplodge (talk) 00:38, 30 January 2012 (UTC)

And 170m is a long way from "right next to you". --Tango (talk) 00:41, 30 January 2012 (UTC)

And he was ridiculously lucky. Don't let the fact of a special exception distract you from the general rule. --Mr.98 (talk) 00:55, 30 January 2012 (UTC)

I agree, your best bet is to not try and resist the explosion but to let it throw you clear. You need a sealed sturdy container with something inside to cushion you (some springs, maybe?). --Tango (talk) 00:41, 30 January 2012 (UTC)

Suppose Tsar Bomba (50 Mton) etc.. is unlikely to be used. But if an B90 nuclear bomb with rating of 200 kton (836.8 TJ) would be used. What level of radioactive exposure in [Sv] (J/kg) will occour?, this essential to calculate any shield. And how much heat energy per area [J/m²] is radiated in order to calculate condensation energy for any wall?, pressure level?, let's assume the distance is 10 meters. Regarding an "blast driven shelter" one still needs to keep the body exposed to less than 50 G in order to not get crushed even with soft cushion. Electron9 (talk) 03:16, 30 January 2012 (UTC)

It would have help if the OP had given a specific measurable distance and yield. For instance, folks in Washington USA who say they where right next to Mount St. Helens when it blew, really mean they where living 30 miles away, a distance which in little o' Europe is often somewhere in another country where everyone speaks a different language. Yet, let's go though it in more detail. Heat: yes millions of degrees but what does that do ? Just flakes of a little of the outer surface. Its not the temperature that's important. People think that the tower of the Trinity test got vaporised – myth. The Project Orion team scoured the area and found most of it, their just wasn't enough calorific energy in the fireball to vaporize it! Pressure: A direct hit means about 30 psi of over-pressure at ground level. Enough to destroy most structures -which is why the high of burst is chosen to give this figure. It would be a piss poor bunker that could not withstand this and they are often designed to withstand a 1000 psi and more. OK that's air burst. What about ground bust. Well, with an air-burst, one has the advantage, that the shock wave hitting the ground gets reflected back and more or less doubles the over-pressure. With a ground bust however this effect (known as the Mach reflection region -speed of sound relative to temp , density, blah, blah) is much reduced. So you need a at the very lest a contact burst. Also, the concrete is exceedingly resilient. Much the same stuff was used for the WW2 military defences in Europe, they could withstand explosive shells (the pressure of which I forget get but it is something like 25 to 35 bar). Which is why one can still see so many structures in Europe – how can you blow them up without ripping all the roof tiles off the neighbouring houses and shattering the windows in the hamlets round about. Radiation: Just 2.4 inches of concrete halves the transmission of radiation. The thickness of bunker-walls gives nigh on complete protection over 3 months of occupation. Children: This requires attributing the same rationality into the minds of the enemy warlords as on might poses oneself. Did Magda Goebbels accept the offer to have her children passed over to the safety of the Red Cross? History is littered with the children of leaders being less important that the 'great plan'. Just in the last half century there are numerous example of despots refusing to accept the inevitable without regard to their kin.--Aspro (talk) 01:30, 30 January 2012 (UTC)

In my opinion, one's best bet is to, first of all, attempt not to be close to a nuclear device when it detonates. --Ouro (blah blah) 07:27, 30 January 2012 (UTC)

The only genuinely effective "nukeproof armor" available with current technology is several billion tons of rock - for example Cheyenne Mountain. Roger (talk) 09:23, 30 January 2012 (UTC)

That depends on whether you're a high-value target (like a NORAD command facility) or just minding your own business, trying to avoid incidental nuking. It's widely believed that during the Cold War the Soviet Union had a number of ICBMs with very-high-yield warheads designed to incapacitate or destroy hardened U.S. facilities. (In the words of Tom Clancy, "to turn Cheyenne Mountain into Cheyenne Lake".) TenOfAllTrades(talk) 14:50, 30 January 2012 (UTC)

Remember Tom Clancy had a tendency to write a lot of fiction for his own monetary gain. Cheyenne Lake congers up a picture more in keeping with artistic licence, than anything else. --Aspro (talk) 16:32, 1 February 2012 (UTC)

Another consideration is that the force of the explosion is sufficient to evacuate the air from the region for a few seconds. The explosive force is followed by an implosive one as the air all rushes back into the space it just left. Combined with the heat and the radiation, the only way to survive the blast is with a self-contained bunker. — The Hand That Feeds You:^Bite 22:36, 31 January 2012 (UTC)

Bacteria ID₅₀

What is the average minimum number of bacteria of any one type that has to be present in the human body to cause an infection? Whoop whoop pull up ^{Bitching Betty | Averted crashes} 18:27, 29 January 2012 (UTC)

Okay, that makes two silly questions in a row plus one unanswerable question. Please try to restrain yourself. Looie496 (talk) 19:05, 29 January 2012 (UTC)

Per the guidelines at the top of the page, the reference desk is not a forum for general discussion. Wikipedia is not a discussion forum. Please try to stay on the task of creating an encyclopedia. Do you need help locating a general discussion forum? Nimur (talk) 19:46, 29 January 2012 (UTC)

42. Von Restorff (talk) 21:04, 29 January 2012 (UTC)

1. Count Iblis (talk) 00:24, 30 January 2012 (UTC)

0, infections are not always caused by bacteria. But 42 is much funnier. Von Restorff (talk) 05:46, 30 January 2012 (UTC)

Benefits of eating meals ?

...as opposed to snacking continuously all day long (and assuming the same food is consumed either way, in the same quantities). And does the blood sugar spike after a meal actually have a purpose, like the blood pressure spikes during a heartbeat, or is it just a negative consequence of eating meals ? StuRat (talk) 20:15, 29 January 2012 (UTC)

[6] — Preceding unsigned comment added by 92.28.79.174 (talk) 21:15, 29 January 2012 (UTC)

That doesn't answer my Q. StuRat (talk) 21:23, 29 January 2012 (UTC)

Part of the reason would be social. For most of the time humans have eaten meals at "fixed" times, it's been with other people. It would be a time for doing many of those things that humans do when they gather in groups, especially involving talking to each other. HiLo48 (talk) 21:38, 29 January 2012 (UTC)

I've read that in young children, continuous snacking can inhibit the onset of socialism (it is typically hard to learn to socialise with a breadstick in one's mouth), increase the likelihood of choking (because a toddler who is playing might forget that he's also eating), and increase the likelihood of tooth decay (because the toddler has food continuously in her/his mouth for a longer period of time), but I have no information about effects of continuous snacking in anyone else. :S Whoop whoop pull up ^{Bitching Betty | Averted crashes} 21:44, 29 January 2012 (UTC)

I think you meant "socialization" rather than "socialism", unless you were being funny. :) But I think the answers given here are correct - that a few meals a day, as opposed to a "continuous meal", fits better with agrarian and industrial societies, as compared with hunter-gatherer societies. ←Baseball Bugs ^{What's up, Doc?} carrots→ 23:46, 29 January 2012 (UTC)

The main benefit from eating fixed meals is that is works well with a sedentary agricultural lifestyle. I'm not sure there's much more supporting it than that (other than habit and culture at this point). Before agriculture — at least, this is my understanding — humans fed more or less continuously through the day. Agriculture and division of labor means you can't do that as easily. --Mr.98 (talk) 22:33, 29 January 2012 (UTC)

Primates including primitive peoples often eat as they come across food. The only reasons that springs to my mind for three-square-meals-a-day is that it is more convenient for a diet of cooked food, it also allows time to work on other activities, as found in non nomadic societies. The blood sugar spike -if its too high- is not good, but this is less pronounced on say a Paleolithic diet. The spike just means that that sugar is being absorbed by the guts faster that the body can convert it. It serves no purpose, other that to provide pharmaceutical companies with a steady supply new patients to buy their type 2 diabetes treatment products.--Aspro (talk) 22:40, 29 January 2012 (UTC)

I was fascinated by this research; "In a first-of-its-kind study, Harvard researchers have shown that cooked meat provides more energy than raw meat, a finding that challenges the current food labeling system and suggests humans are evolutionarily adapted to take advantage of the benefits of cooking." The researchers present a hypothesis suggesting that the extra calories provided by cooked food may have allowed developmental changes to early humans 1.9 million years ago. Obviously, if you have to cook food on a fire, it makes sense to do a whole lot together and then sit down with your family and eat it (ie "a meal"). Anyone who has tried cooking food from scratch on a campfire will know that it's a lengthy process. The ability to open a packet of pre-prepared food and bung it in the microwave is a recent luxury. Alansplodge (talk) 00:26, 30 January 2012 (UTC)

But cooked food doesn't have to be eaten immediately. Heck, if you make jerky out of it, you can eat it months later. StuRat (talk) 03:42, 30 January 2012 (UTC)

It's a lot less effort to eat it as soon as it's cooked isn't it? Alansplodge (talk) 09:08, 30 January 2012 (UTC)

Not if it's more than you can eat and/or food might be in short supply later. StuRat (talk) 05:35, 31 January 2012 (UTC)

That claim depends on two big and very shaky assumptions: one, that people ate meat in significant quantities 1.9 million years ago; two, that they had enough control over fire to cook that meat. Both of these would, I think, be considered extreme fringe theories in anthropology. There is no evidence of cooking beyond 300 or 400 thousand years before present. There's very little evidence of systematic big-game hunting, and essentially no evidence of serious hunting weapons like bows or throwing spears, before ~100 thousand years BP. By 100 kya, humans had modern-size brains and were in many ways similar to us (there are tribes in Africa whose ancestors split from the rest of the human phylogenetic tree 140 kya ago).

Hunting and cooking certainly played an important role in colonization of Northern Europe and Siberia, but they haven't been with us as long as the authors of that article claim.--Itinerant1 (talk) 07:09, 30 January 2012 (UTC)

What do they know in Harvard? Alansplodge (talk) 09:08, 30 January 2012 (UTC)

Being a Harvard student does not keep you from getting involved with fringe theories.--Itinerant1 (talk) 09:53, 30 January 2012 (UTC)

Some of the evidence presented at Control of fire by early humans sounds like more than fringe theories. For some reason, most scientists seem to be dead-set on presenting ancestors' abilities (whether cultural or evolutionary landmarks) as limited only to what has been conclusively proven, even though this by necessity consistently underestimates them. I think you can only read so many silly stories about how the eye is so easy to evolve, so must it evolved independently late in the development of many different lineages, before you just get tired of it. Wnt (talk) 21:26, 30 January 2012 (UTC)

A lot of the evidence beyond "what has been conclusively proven" is sensation-seeking findings which can be interpreted in many different ways (and the correct way is usually mundane). For example, it has been "conclusively proven" and there are numerous pieces of evidence that humans first made it to the Americas ~13kya. It would be huge to prove that humans were there earlier. Therefore, from time to time some scientist announces a revolutionary discovery of an excavation site with some funny-looking rocks next to some pieces of charcoal which were C14-dated to 50kya (even though the whole setup could have occurred naturally), it gets picked up by the media, and in the end the scientist is feeling bitter and slighted by the "scientific establishment".

With regard to fire and cooking, I think that the wiki article gives too much credence to alternative theories. Here's what other anthropologists have to say:

The consensus among many paleoanthropologists is that unequivocal evidence for the use of fire dates to the beginning of the Middle Paleolithic, ca. 200-300 ka. Even during this period, however, evidence of fire is sporadic. ... Extensive sequences of burnt remains and control of fire are clearly observed in Middle Paleolithic contexts younger than 200 ka. These Middle Paleolithic cases present many indications that social activities centered around hearths.

[7]

Where we would expect habitual use of fire in the Paleolithic, i.e., the northern latitudes, we do not see any clear traces of it at all until the second half of the Middle Pleistocene. Cave sequences spanning the later part of the Early Pleistocene and the earlier part of the Middle Pleistocene in Europe do not have convincing evidence of fire. The number and quality of these early sites are significant, and this absence of evidence cannot be ignored. The simplest explanation is that there was no habitual use of fire before ca. 300–400 ka and therefore that fire was not an essential component of the behavior of the first occupants of the northern latitudes of the Old World.

[8]

--Itinerant1 (talk) 23:24, 30 January 2012 (UTC)

Thanks! Your response is very nearly persuasive, but I still have a little skepticism focusing on the "you would expect" bit. What if ancient humans invented fire, but at first they couldn't stand it? Maybe they had an uncontrollable terror of it, or the smell repulsed them or something? And maybe they didn't need it in the same way as modern populations either - better immunity against meat pathogens, better heat regulation in the cold. I can picture that it might have been hundreds of thousands of years until natural selection made them more tolerant of fire, or so far gone in their addiction to it that they brought it into their homes despite the gruesome deaths they must have witnessed. Of course, that's not evidence ... just, I'm still not totally convinced. Wnt (talk) 22:57, 1 February 2012 (UTC)

Eating the food as you find it is meaningful if you cannot protect it from others. Eating meals is meaningful when it comes to time management. 88.26.74.157 (talk) 15:41, 30 January 2012 (UTC)

I almost agree with you. I can't cruse by the fridge without dipping in, because if I don't, I know someone else will raid it, for those bit left over from the night before. As to time management. Whilst I'm walking by it takes no time at all to open the door ... Oh, I see what you mean - I don't have to wast time sitting down. Note: it is also a well known proven fact, that food eaten straight from from a fridge contains no calories whats-so-ever and thus don't need to be counted on any dietary weight loss plan .--Aspro (talk) 22:52, 31 January 2012 (UTC)