Wikipedia:Reference desk/Archives/Science/2011 August 15

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August 15

Why are humans physically weak?

It seems to me that humans, compared to animals of similar weight and size, are quite weak. Especially taking into account the fact that we live in an advanced civilization were food containing the right amount of nutrients is served on time, we can get enough rest etc. etc., while animals cannot assume that they'll have the optimal amount of food every day.

Also we need to do quite a lot of exercise to be fit, while e.g. gorillas are much stronger than humans, even though they eat and sleep all day long. Count Iblis (talk) 00:12, 15 August 2011 (UTC)

Who needs physical strength when our brains allow us to coordinate our violence and use pointy sticks ? Warning - a very violent video, though it's the best example that I can think of that demonstrates man's (even those men that some would dismiss as 'primitives') utter superiority over far stronger animals. --Kurt Shaped Box (talk) 00:33, 15 August 2011 (UTC)

(Edit conflict) We don't depend on our strength for survival as a species, our cognitive ability has usurped that position. We used to be stronger not so long ago, you can see a record of decrease in masculinity and bone density only as recently as 1000 years ago. Plasmic Physics (talk) 00:37, 15 August 2011 (UTC)

The video isn't particularly good as an example, as the voice over is used to make the sociological points (rather tacky ones at that), rather than the cinematography or contents. As far as I can tell it also shows different people (dress, number of people, hunting styles) hunting different animals in different ways in different terrain. Some of the shots are obviously out of sequence. And it requires more than a little elementary reading to observe the role of mutual aid in hunting here due to its obscuration. Wouldn't Kropotkin's Mutual Aid—despite its methodological problems and age—make this point better? Fifelfoo (talk) 01:49, 15 August 2011 (UTC)

Kurt's linked movie incongruously shows hunters with primitive spears and wearing obviously machine-made short trousers. Why in such a large crowd has no one thought of using a bow and arrows which would save a lot of running? These are posed movie scenes using many extras not all of whom own spears or do more than jiggle them. ~~

Starvation seems to have been rampant in our past, such that we've evolved to use as little energy as possible. Thus we only develop big muscles when our body detects a need for them, that is, when out current muscles are overtaxed. StuRat (talk) 00:41, 15 August 2011 (UTC)

Exactly. μηδείς (talk) 00:47, 15 August 2011 (UTC)

Do other great apes suffer from this problem? Where their muscles deteriorate if not being exercised constantly? ScienceApe (talk) 13:06, 17 August 2011 (UTC)

Let's forget about the big brains for a second, just for the point of argument. In terms of physical fitness (from an evolutionary standpoint), there is a lot more than just "strength". Gazelles are not very strong, compared to a cat of the same size. But that's because they are optimized (by evolution) for speed. Some animals are clearly optimized for raw strength. Humans, taken from a purely physical view, and throwing out the lazy excesses of modern life, are optimized to be somewhat mediocre in strength (not at all "weak" — consider that humans whose lives rely on physical strength, like professional athletes, are actually pretty strong), mediocre in speed (we don't run terribly fast), but we are great at endurance. Check out the Man versus Horse Marathon for example — even horses, which we think of as being great draft animals (and are only as great as they are because we bred them for thousands of years), are pretty poor compared to humans over long hauls. We're great long distance runners. We have way more endurance than the gazelle like animals who can conjure up huge amounts of speed but not for very long. We fit a specific evolutionary niche, even without the brains (which can't be left out, in the end — your evolutionary niche changes once you can hunt in packs, use weapons, etc.). We are also terribly versatile — our body is great at regulating temperature and dealing with very different climates, which is something that a lot of very strong or very fast animals do not have. Having tons of extra muscle mass would not only require a very different type of diet (more reliably protein rich than we had for most of our evolutionary history) but would reduce that endurance advantage. I don't want to tell a "just so" story, but it seems rather clear that we have long occupied a very different type of evolutionary niche than, say, a gorilla, or even a chimpanzee. The particular primates we have evolved from all look like creatures that survived on endurance, adaptability, and intelligence, none of which are particularly served by gigantic muscles. --Mr.98 (talk) 01:46, 15 August 2011 (UTC)

Yes, the points of endurance and human eye-hand and other types of co-ordination (which are also highly important for speech) are quite important. Imagine an orangutan ballet. μηδείς (talk) 02:16, 15 August 2011 (UTC)

Even more-so than eye-hand coordination is simply the intricacy of control of the hands and fingers in general. Humans are capable of some rather minute and complex hand and finger control. Even ignoring the problem of figuring out music in general, I'm not sure you could teach a chimpanzee to play halfway decent electric guitar, or to stitch a quilt, or anything like that. I'm not sure that any other animal has the motor control that humans do over their fingers. --Jayron32 02:53, 15 August 2011 (UTC)

Yes, I was negligently vague in saying just eye-hand co-ordination. We also have amazing coordination of our faces and vocal apparatuses. Speech is essentially a sort gesture transfreed to the mouth. Another thing to consider is that we can transfer learned modules from one organ to another, for instance signing our signatures, which we have only ever practised with our fingers, to a pen held by our lips or our toes. That's actually quite amazing and something no animal can really copy. μηδείς (talk) 03:18, 15 August 2011 (UTC)

That's quite a formidable wall of text you people have conjured up, so forgive me if I'm echoing a previously stated point: Who needs strong muscles when you have the knowledge to smith a sword? --Σ _{^talkcontribs} 03:37, 15 August 2011 (UTC)

Because big muscles are required to wield the sword, of course. StuRat (talk) 03:50, 15 August 2011 (UTC)

Smithing a sword is actually a pretty recent innovation from an evolutionary standpoint. It's not what got us through those thousands of years before civilization really started up. The real human innovations are being able to organize themselves in groups, be extremely adaptable, and have lots of fine motor skills. High tech (which metal smithing counts as) is pretty cool but didn't play any real role in our evolutionary history, except for the fact that it allowed a few groups of humans to kill out a bunch of other groups of humans. --Mr.98 (talk) 15:06, 15 August 2011 (UTC)

Well, actually you do see heavier musculature in areas like New Guinea and Subsaharan Africa where physical competition between equally armed males is more important for reproductive success. Males in New Guinea tribes that still practice intertribal warfare can have the same chance as male chimps, about 30-35% of dying in violence. To the victors go the ladies. See the well written and researched Before the Dawn. μηδείς (talk) 03:46, 15 August 2011 (UTC)

I agree entirely that the strength of humans is really underestimated by most here in this thread. Humans whose life depends on their raw strength (rare in any state of "civilization") are pretty formidable creatures. They couldn't arm wrestle with a full grown chimp, but they are not indefensible weaklings. The fact that all its takes is a spear to hunt lions says something quite profound about the abilities of humans to be pretty dangerous even without a huge amount of technological augmentation. Stone age man was a pretty formidable animal, as the record of megafauna extinction shows. --Mr.98 (talk) 15:06, 15 August 2011 (UTC)

I feel this thread is going somewhat off track when talking about all the things humans are good at. This would only be relevant if they were somehow mutually exclusive with being strong. I don't see how having dexterity in the fingers precludes strength, for example. We should instead focus on the disadvantages of strength. The two I've seen mentioned so far are the energy requirements and the need to eat meat on a regular basis. StuRat (talk) 03:48, 15 August 2011 (UTC)

Well, and the fact that hypertrophy in certain areas leads to hypotrophy in others. (There's a Somebody's Law about that in developmental biology, but I forget who.) Big muscles do compete with big brains and other sorts of costly development. Heavy musculature didn't lead to Neanderthal dominance Given we interbred, and the gracile form succeeded, that likely says alot. You can't look at just musculature and judge its value on its own. Biology doesn't work that way. You have to look at other tradeoffs like long distance stamina and human memory and coordination (which are interrelated) to make any holistic sense. Otherwise, by itself, cost no object, bigger muscles will obviously be beneficial. μηδείς (talk) 04:05, 15 August 2011 (UTC)

The endurance running hypothesis is probably the favoured reason for why we are not built for strength. Look at the winners of the marathon event and you'll see what's optimal for persistence hunting where one man can hunt down and kill an antelope with a stone. Wolves are the other main persistence hunters, they have a bit more speed and use teeth instead of stones but have less persistence. Dmcq (talk) 12:48, 15 August 2011 (UTC)

So would it be safe to assume that other apes don't have anywhere near the endurance that humans do, and that the distance covered by the ape army in Rise of the Planet of the Apes is pretty unrealistic? (Because otherwise the film is very plausible!) —Akrabbim^talk 14:22, 15 August 2011 (UTC)

It is a fact that other apes do not have the body structure or musculature to endure long distance upright walking, let alone the endurance for long marches. Apes revert to knuckle walking about as quickly as we revert to flat footed from tippy-toe walking.No ape other than Oliver (chimpanzee) has ever been documented as adopting an upright stance as a matter of habit, hence speculation as to his unique species status. As for plausibility, that depends more on the ignorance of the audience than the accuracy of the artwork. For example, those who know nothing of physics might accept the notion that there could be such a thing as "red matter" which could in the most recent Star Trek movie be used to create a black hole. But any knowledge of gravity and the types of substances that exist show the idea to be ridiculous, not to mention the idea that a supernova of one star could immediately destroy a planet in another system over as was done to Romulus. I have not seen the new Apes movie (the first remake was dreadful) so maybe I am wrong, but given what I know about the creators I don't find it plausible that it will be plausible. μηδείς (talk) 15:47, 15 August 2011 (UTC)

Thanks everyone for the replies so far. Reading all the replies, what is still an issue is more or less what StuRat wrote above about why physical strenght would have to come a the expense of physical strength. Of course, having an extremely muscular body build may not be comaptible to being able to perform well at long distance running, while the latter ability may have been important for us in the past. Now, it seems to me that humans are more susceptible to become "couch potatoes" when they don't exercise a lot while a gorilla can just eat and sleep all day long. As suggested above, that has to do with the human body adapted to deal with famines. Count Iblis (talk) 17:23, 15 August 2011 (UTC)

Guinea pigs and motion sickness

According to author Mary Roach in the book Packing for Mars (2010), guinea pigs do not suffer from motion sickness. Why is this? Viriditas (talk) 06:21, 15 August 2011 (UTC)

Googling "guinea pigs motion sickness" brings up several research papers that suggest this is untrue.--Shantavira|^{feed me} 07:41, 15 August 2011 (UTC)

I think Roach means to say that guinea pigs don't suffer from motion sickness in zero-g. In any case, I'm not seeing anything showing they suffer from motion sickness like other animals. Viriditas (talk) 10:11, 15 August 2011 (UTC)

A key point is probably 'what do you mean by motion sickness in zero-g'? If you mean something that really is motion sickness that occurs in zero-g environments, then there's no to think any animal which gets motion sickness won't get it. This ref [1] ([2]) supports the conclusion that what you call 'zero-g motion sickness' or is also (and more commonly) called space (motion) sickness or space adaptation syndrome is indeed a form of motion sickness. That being the case, there's reason to think animals which get motion sickness aren't going to get zero-g motion sickness. However the ref also suggests it's still something that is poorly understood (in terms of what causes it).

While there has been a fair amount of research, I don't find much evidence it's been that well observed in animals in space. A lot of research treats space motion sickness as a form of motion sickness, so use methods to stimulate it. Notably from a few quick searches, I can't find any refs discussion space motion sickness in dogs or guinea pigs or mice. However, it has evidentally been observed in monkeys [3].

BTW [4] mentions guinea pigs and rats are a poor model for ('normal') motion sickness since they don't vomit (leading to dogs and monkeys being the most commonly used ones). The earlier ref on space motion sickness also mentions this for rats and rabbits. Evidentally Suncus murinus can be made to vomit and do get motion sickness including vomitting [5]. Cats have also been suggested as models [6], including for zero-g maneuvers in parabolic flight, although I presume that's a poor model if you believe space motion sickness is unique, since the maneuvers would generally induce motion sickness ala Airsickness anyway hence Vomit Comet. (I should mention I didn't read the article as I don't have access to the archives [7].)

From [8] and [9], I gather antiemetic drugs are one of the targets to try and prevent or reduce space motion sickness, which isn't surprising since it's perhaps one of the worse symptoms. Some experiments relating to space motion sickness have used guinea pigs [10] (admitedly a rather long time ago) and more recently rats [11] which would seem odd if the researchers did not believe they could get space motion sickness.

All this leads me to conclude there's no reason to believe guinea pigs don't get space motion sickness. They don't vomit, so are often a poor model for motion sickness, unless you use a more sophisticated system, although this still won't work if one of you specific targets is vomiting. But it seems to be usually accepted (as Shantavira said) they do get ('normal') motion sickness e.g. [12] [13] [14]. As hinted at earlier, other non-emetic species like rats [15] [16] also seem to be considered to show motion sickness (the first ref on space motion sickness also mentions this in general). This old article [17] doesn't entirely agree, but that just seems to relate to the lack of vomitting. If you follow a similar definition then the answer is obviously, no they don't get motion sickness including space motion sickness. (IMO a more logical POV is they do get motion sickness but it isn't as bad as in some other animals due to the lack of vomitting.)

BTW one of the key signs of motion sickness in non-emetic animals appears to be pica and immobility (from the first ref but I think I also read it elsewhere) although there are also other symptoms like those relating to food and water intake, urination and defacation.

Also I would point out from what I've seen (and as is hardly surprising), that at the current time most research on space motion sickness is targetted at ways to reduce and prevent it, as well as trying to understand it, ultimately for humans. The well-being of pet or research guinea pigs in space may be a minor concern but isn't the biggest concern (by which I mean researchers probably aren't going to spend great amounts of time studying space motion sickness in guinea pigs so they can work out what harm it is doing except to study the effects in general or to prevent their experiments being screwed up by sick guinea pigs).

P.S. I just found [18] which does mention space motion sickness in rats.

Nil Einne (talk) 14:55, 15 August 2011 (UTC)

What leaf is this?

can anyone tell me what leaf this is?Accdude92 (talk) 06:39, 15 August 2011 (UTC)

It look quite a lot like basil (Ocimium basilicum). Richard Avery (talk) 07:07, 15 August 2011 (UTC)

(e/c) Most probably basil (possibly an Ocimum basilicum cultivar).

But we can't really know for sure without other info. Where is it from? Can you describe the odor? Do you have pictures of other parts of the plant? Can you describe the flowers? How large is it?-- Obsidi♠n Soul 07:18, 15 August 2011 (UTC)

Quantum mechanics/many-worlds

If I understand correctly, then the many-worlds interpretation of quantum mechanics implies (among other things) that for every quantum mechanics experiment performed, there is a universe created that observes every possible result, e.g. if an experiment is performed, and a particle is measured that can be in state A or state B, then there will be a universe in which the outcome is A, and a universe in which the outcome is B. Does this mean that there would be a universe in which the results of every single quantum physics experiment ever would be consistent with a wholly deterministic (i.e. not probabilistic) theory of quantum mechanics? Like, as in, all the scientists in that universe (justifiably) think if you set up x equipment in y configuration and perform a measurement, then you will always get z result without fail, and they all have no idea what 'superposition of states' means? --superioridad ^(discusión) 11:33, 15 August 2011 (UTC)

Yes. When scientists do experiments they usually look at what the probability of such an outcome is given the theory they are testing (eg. classical mechanics) and if that probability is very low (less than 5% is common, although some fields use much lower values) then they reject the theory and try and come up with something else. Just because there is a less than 5% chance of something happening obviously doesn't mean it can't happen, so there is always a possibility of incorrectly rejecting a correct theory. Since it's possible for that to happen once, it is also possible for it to happen every time. Under many-worlds, anything that is possible happens in some universe, so if many-worlds is correct there must be universes where no-one has ever noticed a quantum effect. The "density" of such universes in the multi-verse would be extremely low, though. --Tango (talk) 11:40, 15 August 2011 (UTC)

No. When repeating the experiment, the longer the uninterrupted run of outcomes A (or B) the rarer the universe. An infinite run is unobtainable due to the finite time to measure (frequency of measurements) and lifetime of that universe. NB: The "rarity" or low probability of a universe is irrelevant if you are in it. This one is probably one of the rare ones. Cuddlyable3 (talk) 12:10, 15 August 2011 (UTC)

The example given isn't well specified, because you have a continuum of superpositions of the form cos(theta)|A> + sin(theta)|B>. Then you could assume that for every theta there only has been one outcome (A or B), and this similarly generalized for more complicated superpositions. This is then equivalent to replacing the Born rule probability by a probability function that can only take the value of either zero or one. But then, you can't observe interference effects anymore, so you don't reproduce classical phenomena correctly, like refraction of light, sound waves etc. etc. Count Iblis (talk) 15:32, 15 August 2011 (UTC)

I think there could be such a universe (with a bit more specification), but I don't think there would be any scientists in it to carry out experiments. The existence of life as we know it depends on the principles of thermodynamics, which would completely break down in that universe. (The laws of thermodynamics are statistical, not directly physical.) Looie496 (talk) 16:13, 15 August 2011 (UTC)

Also note that quantum effects aren't only measured or observed by humans in experiments, quantum states collapse everywhere due to a wide variety of phenomena. Alternate universes would be created unimaginably often in the Many-worlds interpretation. Many academics do not lend much credibility to the interpretation. Rosilisk (talk) 16:39, 15 August 2011 (UTC)

Rckrone (talk) 17:14, 15 August 2011 (UTC)

You just have one big static multiverse, the state of this satisfies the equation H|psi> = 0. The splitting doesn't happen on the level of the multiverse, it's just what you get when you focus on a particular component of |psi> in the basis of "pointer states", apply the operator exp(-i H t) and then expand what you get again in that pointer basis. Count Iblis (talk) 17:34, 15 August 2011 (UTC)

I don't understand that, but you mentioned "splitting", and a couple of people spoke of universes being "created", and those are both conceptual pitfalls. The universes in the many worlds interpretation are equivalent to instants of time: therefore they don't change, or age, or have a point in time at which they are created or split apart. They are points in time, and pre-exist. Perhaps, though, that's what you just said? 81.131.26.155 (talk) 09:17, 16 August 2011 (UTC)

For the record, I meant things behave only in a seemingly deterministic manner in certain experiments (through sheer chance), not in all cases (i.e. everyday quantum interactions that happen constantly go on as usual). But, of course, as has been mentioned, you wouldn't be able to reproduce classical effects properly if you counted them as "quantum mechanics" experiments. But if classical physics (say, diffraction of light) works, and more fundamental, particle-physics-oriented stuff demanded a deterministic, non-probabilistic explanation, (suppose, for example, that the double-slit experiment, when done with a single particle emitted at a time, gave results that could be predicted deterministically) would everyone just be completely mystified as to how to explain physics? --superioridad ^(discusión) 05:05, 16 August 2011 (UTC)

The many-worlds interpretation seems pretty sensible compared to the Copenhagen version, but I still have substantial trouble with it. As I understand it, if a single atom hangs in the air in an auditorium, everyone in the audience splits as photons from the projector bounce from it carrying the information (unknown but still potentially interpretable) that an electron sits in p_x or p_y or p_z as measured from the individual frame of reference of each member of the audience. I'm not sure, but I think, in a lab, one researcher might try to measure the position of a particle, and another the particle's momentum, both at the same instant, each with a 50% probability the experiment doesn't happen. For a moment (50% chance) one researcher has one result, very precisely, and the other has the other result, very precisely, neither having any knowledge of the other value. The world splits to accommodate the precise value of each of these measurements. So you end up with universes defined by measurements that collectively violate Heisenberg uncertainty, which seem to have no physical meaning, don't you?

To me the transactional interpretation makes the most sense.

As for the original poster, quite likely there are worlds where, through simple bad luck in experiments, people never figured out the laws of physics. I don't think we need to call on the many-worlds interpretation for it; a short jaunt with the warp drive should be enough. We might find out that this is one such world... Wnt (talk) 14:39, 18 August 2011 (UTC)

Growing catnip

I have got a packet of seed of Nepeta cataria, when and where should I grow it. — Preceding unsigned comment added by 182.178.218.76 (talk) 13:33, 15 August 2011 (UTC)

It is not very demanding, but likes full sun in damp, uncompacted soil. It commonly grows as a weed along ditches and streambanks. Plant in the early spring, as soon as the soil thaws. Or you can start the plants indoors and transplant outdoors in mid-spring. If conditions are right, the plant will continue to grow in the same place for many years. Be careful where you plant it, because catnip can become quite an aggressive and invasive weed. Dominus Vobisdu (talk) 14:24, 15 August 2011 (UTC)

And we should also mention the obvious: Grow it where cats can't get to it, or you will likely find the plant ripped up by the roots and dirt all over the place. StuRat (talk) 17:13, 15 August 2011 (UTC)

can I grow it in the current season ? — Preceding unsigned comment added by 182.178.185.63 (talk) 08:08, 16 August 2011 (UTC)

That depends on what season you're in, winter or summer. Plasmic Physics (talk) 08:31, 16 August 2011 (UTC)

I live in northern hemisphere, it's summer here. — Preceding unsigned comment added by 182.178.201.112 (talk) 06:23, 17 August 2011 (UTC)

manual

is there a COMPLETE list of army and cia manuals here — Preceding unsigned comment added by Von1235 (talk • contribs) 14:09, 15 August 2011 (UTC)

Would the U.S. Army and CIA interrogation manuals article be of any help? —Akrabbim^talk 14:28, 15 August 2011 (UTC)

We also have Category:Handbooks and manuals and Category:Military training books, if that leads you to any other information you may be looking for. —Akrabbim^talk 14:38, 15 August 2011 (UTC)

There is also Army Knowledge Online (and DKO for the consolidated services; similar resources for other services) but you don't have access unless you are in the Army, (or other branch of the United States armed forces); or, certain types of contractors or liaisons, or other special category. Even if you have access to AKO, it's implausible to expect a complete listing of all manuals for the Army; the institution is huge, and there are lots of subject or domain-specific expertise documents that would be irrelevant to most users. Regarding the CIA, there are lots of resources available online at the CIA website. Most of these manuals will bore the average person to tears. ("Manual for operation of telephone in Ghana Field Office"). What sort of manuals are you looking for? You probably want to start with FM-1, "The United States Army", which you can download free of charge, without needing to log in, from the United States Army website. Then, consider reading FM-3, "Operations." You can buy reprints of these manuals at almost any book retailer. You may find them to be disappointingly dry reading-material. Nimur (talk) 16:57, 15 August 2011 (UTC)

Also, the CIA and US army are constantly revising existing manuals and creating new ones, so maintaining currency on more then a single field would require a major time commitment. Googlemeister (talk) 18:08, 15 August 2011 (UTC)

transformed circuit drawing for all electrical component

please send me the above mentioned subject drawing — Preceding unsigned comment added by 210.212.4.187 (talk) 14:32, 15 August 2011 (UTC)

I don't understand what you are asking for. Looie496 (talk) 16:09, 15 August 2011 (UTC)

I suspect, based on your request, that you found one of our over 3.7 million articles and thought we were affiliated in some way with that subject. Please note that you are at Wikipedia, the free online encyclopedia that anyone can edit, and this page is for asking reference questions about science topics.--Shantavira|^{feed me} 16:20, 15 August 2011 (UTC)

You may find what you want in the article Circuit diagram. Cuddlyable3 (talk) 17:50, 15 August 2011 (UTC)

Human survivability envelope on a newly discovered planet

I am trying to come up with the range of human compatible requirements for colonizing a distant planet or moon. I am thinking of places where humans are not going to need more equipment for survival then is commonly used on earth for long periods (central heating, clothes, sunblock, not SCUBA equipment or radiation suits). So I have thought up a list of things humans would require of a planet and would like to know what ranges people can handle long term (more then 20 years). Critical things to look at would be...

Gravity. Obviously 1g on earth.

There night be a wider range here than you'd think. Probably not more than 1.1 or 1.2 g, but on the low side we might be able to survive quite low gravities, with the proper exercise to save bones and muscles from atrophy. StuRat (talk) 20:05, 15 August 2011 (UTC)

Radiation. Background radiation on earth varies on location, but I think 0-10 miliseverts a year is typical

Oxygen. Earth has 21% O2 at sea level with a standard pressure of about 101 kPa. Human habitation at high altitudes can be down to about 50-60 kPa.

Our article Breathing gas says humans can survive partial O2 pressure of 16-180kPa, but don't know about long term.

Temperature. Humans live in a temperature range with extremes of -100 up to 130 deg F, though we prefer a more mild climate and have special needs at extreme cold. Telling against this is the expensive equipment at Antarctic science bases.

Lack of atmospheric toxins. Mostly concerning volcanic activity.

Obviously humans need water, but how much depends on the environment they are in.

So what kind of ranges for these variables can humans take for the long term? Googlemeister (talk) 18:34, 15 August 2011 (UTC)

Atmospheric pressure is another important parameter. You would also ideally want a planet with a similar day/night cycle to earth. Lack of hostile native lifeforms is a plus! --Goodbye Galaxy (talk) 19:53, 15 August 2011 (UTC)

You should have a good background in Larry Niven's Known Space. One recurring theme of his is the interesting consequences of a space colonization program that send colonist ships to worlds, Jinx, Plateau, We Made It, where robots have found a point habitable to humans. μηδείς (talk) 19:58, 15 August 2011 (UTC)

One other thing to mention is food. If we are to grow our own, we'd need sunlight, around 1% carbon dioxide in the air, and soil with all the necessary minerals and no toxins/poisons (or water with all the necessary minerals, and no toxins or poisons, if we are to grow food there). StuRat (talk)

Adverse airborne bacteria et al.? 16th century explorers might have brought smallpox and others to South America, there could be nasty stuff awaiting us on other worlds as well. --Ouro (blah blah) 07:53, 16 August 2011 (UTC)

1% CO2 seems pretty high if the pressure is what it is on earth. Here we only are around 0.04% CO2 (400ppm). Sunlight would be needed to grow food though unless there is some kind of natural species that survive without it that we could eat. Googlemeister (talk) 20:20, 15 August 2011 (UTC)

Thanks, for the correction. StuRat (talk) 20:31, 15 August 2011 (UTC)

Also, this planet can't have bad weather, like the 1000 mile an hour winds of Jupiter. And there can't be a constant barrage of meteors, as would be common in many new star systems. StuRat (talk) 20:19, 15 August 2011 (UTC)

An ozone layer, or some means of blocking UV light, seems important not just for people but also for any food we grow (plants or animals). StuRat (talk) 20:35, 15 August 2011 (UTC)

An ozone layer is likely to be a natural consequence of an oxygen atmosphere: ultraviolet light interacts with O2 to produce free oxygen atoms, which in turn react with O2 to produce O3. --Carnildo (talk) 02:10, 19 August 2011 (UTC)

Our planet's axial tilt, which gives us seasons, and large moon, which, along with the Sun, gives us tides, are necessary for some plants and animals, but I'd guess we could survive without them. The partially molten core, on the other hand, is important in maintaining a strong magnetic field, which deflects the solar wind enough to allow for a thick atmosphere to remain. StuRat (talk) 20:41, 15 August 2011 (UTC)

So How high of pressure can humans live in long term? How low? How much radiation can we handle long term? How high of gravity could we take long term? Long term being decades. Googlemeister (talk) 18:38, 16 August 2011 (UTC)

We may not know the answers to some of those, yet. For gravity, I imagine it would depend on the degree of power equipment we use to aid us in our normal lives. Somewhere around 1.5 g it might become impossible to carry much of anything (in addition to our own weight), so we would need power carts to carry our groceries into the house, etc. Also, stairs would be out, we'd need ranch homes only, or homes with elevators.

At 2 g we might find it impossible to move more than short distances, so would need power wheelchairs. Having a chance to acclimate would also be important, so being able to steadily increase the gravity until out bodies got used to it would be far better than just landing on a 2 g planet.

And, of course, only those with athletic builds should be accepted for this colonization project, the obese would quickly die. Being short would also be quite useful, as a fall can be deadly at 2 g, for the tall. And you'd need shoes with lots of padding, or better yet, springs, as well as a pressure suit to keep your blood from pooling at the low points.

The good news is, high gravity isn't likely to be a limiting constraint, since only the larger of the Jovian planets, which are inhospitable for a number of other reasons, are likely to have too much gravity for us to stand. In our own solar system, for example, only Jupiter and the Sun have too much gravity: [19].

The same is also true of low gravity. Any planet or moon with too little gravity for us to maintain bone density, etc., would likely also lack a significant atmosphere.StuRat (talk) 21:08, 16 August 2011 (UTC)

Good point, these variables would likely have some kind of degree of connection with each other. Googlemeister (talk) 14:29, 17 August 2011 (UTC)

See Ramsar. People and animals are more capable of adapting to new environments over time than is commonly imagined! Wnt (talk) 14:42, 18 August 2011 (UTC)

The Ramsar link is to a dab and your meaning is not immediately apparent. μηδείς (talk) 20:56, 18 August 2011 (UTC)

Ooops. Try Ramsar, Mazandaran. Wnt (talk) 21:52, 19 August 2011 (UTC)

How can I get rid of Acetone in my car

A few weeks ago I applied Acetone on my car windshield. The vapors and fumes got so bad that it irritated my body and eyes. I will roll down the windows to air it out but its still there.

I tried almost everything. I even bought a car purifier but that didn't work. Please help me. Does anybody have any helpful suggestions?

It seems like the whole car is infected. How can I get rid of the fumes and vapors of Acetone in my car? — Preceding unsigned comment added by 174.111.55.161 (talk) 20:17, 15 August 2011 (UTC)

Something doesn't make sense here. Acetone is volatile, so should have all evaporated in short order. I suspect that something else must have been mixed with the acetone. Can you check the ingredients list, maybe an odorant was added ? The only other thing I can think of is that the acetone decomposed some of the materials it contacted, and they are now giving off that odor. Does the odor come from the paint, windshield, or where, exactly ? StuRat (talk) 20:24, 15 August 2011 (UTC)

Thanks for your comments StuRat. I didn't read the product before I used it, made a mistake. I threw away the Acetone can. The odor comes mainly from the windshield. — Preceding unsigned comment added by 174.111.55.161 (talk) 20:28, 15 August 2011 (UTC)

Acetone is pretty volatile, so the best strategy is simply to air out the car as much as possible. You're probably also hypersensitve to the smell of acetone since you had a bad experience with it, and you're reacting a bit more strongly than you normally would. That's a normal reaction, and it should wear off soon. Time and air are the best solutions to both problems. Trying to mask the smell would probably make matters worse, and there is nothing that you can use to "absorb" the acetone. Just keep airing it out and not using the car for a few days, and things should return to normal. As StuRat said, there is the possibility that some other ingredient besides acetone is to blame, or that the acetone reacted with the coating on your windshield to produce a noxious product. However, I think that temporary hypersensitivity is the most like reason for your discomfort. Dominus Vobisdu (talk) 20:33, 15 August 2011 (UTC)

(EC) For the record, gasoline will do the same thing if it gets spilled in your car, so keep the gas can in the trunk. For the acetone, don't car windshields have plastic layers in the middle? I know that acetone will react with several different kinds of plastic so if you had a crack or chip in your windshield, acetone could have gotten to the plastic, and reacted with it to form a less volatile, longer lasting odorous compound. The same could happen if it got on other plastics in the car, like the dashboard. Beyond that, the only other things I can think of is to get some fans to blow air through the car while you have it parked to try and remove all the smell you can. Be prepared though, that there is a chance the smell will never fully go away. Googlemeister (talk) 20:38, 15 August 2011 (UTC)

OK, time to list some desperate measures:

1) You could replace the windshield.

2) You could sell the car to somebody with little sense of smell, like a smoker. StuRat (talk) 20:56, 15 August 2011 (UTC)

Or, a little less radical, take it to a body shop and let them bake the car in the oven for a few hours. With the windows down, of course. Dominus Vobisdu (talk) 21:50, 15 August 2011 (UTC)

I wonder if you got some water with a few drops of something like eucalyptus oil or lavender oil and gave the hard surfaces of the inside of the car a good rub down with it.. Might be worth a try. Vespine (talk) 00:53, 16 August 2011 (UTC)

Do you have leather seats by any chance ? I had a problem with them having absorbed a rather unpleasant odor (of a toddler who had an "accident", in this case). I found that I had to use an oil to remove the oil-soluble odors present in the leather. I used cocoa butter, since it was cheap and I like the smell. My car smelled like sunbathers for a few weeks, but that was a marked improvement over baby poo. After the cocoa butter smell dissipated, the baby poo smell was gone, too. I suspect that oil would work on vinyl seats, too, but not on cloth.StuRat (talk) 00:11, 17 August 2011 (UTC)

I don't know, but I'd be suspicious that the acetone dissolved into some rubber or plastic part (or into the plasticizer mixed with it). Simply squeezing or rubbing the culprit substance when the car is aired out should give you the scent of it. Once identified, I would think that a thorough soap and water rubdown might get some of it out that is absorbed close to the surface; then spraying it with lots and lots of plasticizer ("Armor All", etc.) should compete with it, so when you wipe off the excess more acetone is removed. I don't know if this will work to any significant degree though, it's just an idea to try. Wnt (talk) 14:50, 18 August 2011 (UTC) - Actually, on double checking, Armor All doesn't sound like it is a plasticizer as I'd once heard; it would just form a hydrophobic layer on the surface. That might slow the release of the acetone, which you might also find a positive solution, not sure. Wnt (talk) 14:53, 18 August 2011 (UTC)

what is the function of the iPhone's 3GS 6R8 coil?

It's this thing that relays power to the LCD display...but I'm curious why this seems to short out first upon water damage (or why coils tend to short out), and why use a coil at all? Is it an inductor? Why would you need an inductor -- surely everything in the circuit board is DC? elle _{vécut heureuse} ^{à jamais} (be free) 22:05, 15 August 2011 (UTC)

Any LCD screen has a backlight to illuminate it. I don't know about in an iPhone, but for laptop LCDs, the backlight is a fluorescent bulb that runs on high-voltage AC current, so maybe the coil is part of a CCFL inverter. Rckrone (talk) 22:45, 15 August 2011 (UTC)

I thought that too but then thought surely all phones these days use LEDs for illumination? However I'm having trouble finding a confirmed source and there are several forums which don't seem to come to a confirmed conclusion as to whether the iPhone uses LED or CCFL backlight. I have found the 6R8 coil for sale on fleabay and it says that it is a part used in the repair of dead or dim backlight, but I'm not 100% sure if that confirms the backlight must be CCFL or that there is some other exotic LED circuit using a coil. . Vespine (talk) 00:47, 16 August 2011 (UTC)

The article about the Royer oscillator notes that an inductor in the centre-tap transformer supply reduces harmonic content and improves efficiency. A Royer oscillator is often used to drive the cold cathode fluorescent lamp (CCFL) backlight of an LCD display. Cuddlyable3 (talk) 11:15, 16 August 2011 (UTC)