Wikipedia:Reference desk/Archives/Science/2010 August 23

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August 23

Wipe chimenea with "oily rag"

The instructions that came with my cast iron chimenea and advice found on the Internet suggests wiping the chimenea with an oily rag to prevent surface rust. These sources neglect to mention what type(s) of oil is acceptable. What type(s) of oil is acceptable? ----Seans Potato Business 01:23, 23 August 2010 (UTC)

Any oil will stop the rust, but I would use Mineral Oil, also called Baby Oil. Organic oils will decompose or oxidize, especially with heat. You can also use tool oil, basically any oil from the hardware store. Fresh (new) motor oil is also good since it's specially made to resist heat. Ariel. (talk) 01:51, 23 August 2010 (UTC)

Best wavelengths for interstellar communication

In space the Cosmic microwave background radiation is a relic of the Big Bang event. On Earth there are many additional sources of Background radiation, see article. Cuddlyable3 (talk) 14:00, 23 August 2010 (UTC)

Which electromagnetic radiation frequency band that can be focused directionally has the lowest combination of background power and opacity in interstellar and interplanetary space? 208.54.5.76 (talk) 08:09, 23 August 2010 (UTC)

From 1420 to 1666MHz. See Waterhole (radio) - that's where SETI are putting most of their efforts. SteveBaker (talk) 22:27, 23 August 2010 (UTC)

Study of anti-HIV drugs, where there was little evidence of effect as the drugs became widely used by everyone before the trial finished

Hi, I'm looking for a study I read once before that looked at a drug to treat HIV, but before the trial could be completed the drugs became widely used by everyone (being purchased off the internet I think?) and so in the analysis there was little evidence of their effect as they were being compared to controls who also had access to the drug. Can anyone help me find it again please? Thank you. Last Polar Bear (talk) 10:20, 23 August 2010 (UTC)

I asked a relative of mine who is a pharmacokineticist and the only drug that comes to mind is AZT (zidovudine). He says it was on Glaxo's shelves for quite some time since it was being used to treat other ailments. That was back in the late '80s. Hope this helps... Dismas|^(talk) 23:40, 23 August 2010 (UTC)

Thank you for asking - you're very dedicated! :) I'll have a look into zidovudine trials, and hope I find something relevant. Thanks again!! Last Polar Bear (talk) 09:44, 25 August 2010 (UTC)

Redox confusion

This paper discussing the enzymes of Phanerochaete chrysosporium has a sentence which states "Cellobiose is oxidised by two electrons for the reduction of a wide range of electron acceptors". How can something be oxidised by electrons, when oxidation is the loss of electrons?! Thanks in advance. Smartse (talk) 11:31, 23 August 2010 (UTC)

They don't specify that those electrons are gained. Maybe they mean that it is oxidized by the loss of those two electrons. —Preceding unsigned comment added by 96.227.210.71 (talk) 11:35, 23 August 2010 (UTC)

It's a common "shorthand" way of saying things: in redox reactions, electrons are the "currency", so "oxidized by two electrons" doesn't mean the electrons were the oxidizing agent, it means that the molecule lost two electrons (and not one or three). Physchim62 (talk) 23:47, 23 August 2010 (UTC)

Species

A stamp from Switzerland

When a new species is discovered, do they still give them a latin name? Why, hasn't latin be depreciated? 82.44.54.25 (talk) 13:05, 23 August 2010 (UTC)

Yes, a new species will be given a two-part Latinized name - this is called binomial nomenclature. This is a convention that is practical, useful and well understood by biologists and other scientists. Many fields of study and human interest have created their own terminology - biology happens to have developed a richer and more structured nomenclature than, say, wine-tasting or baseball, possibly because it has more things to name. Why do you think this system should be "depreciated" (or perhaps you mean "deprecated") ? What would you replace it with ? Gandalf61 (talk) 13:18, 23 August 2010 (UTC)

The OP thought that Latin wasn't used anymore and wonders why it is still used in binomial nonclemature. --Chemicalinterest (talk) 13:26, 23 August 2010 (UTC)

Occasionally it's not Latin e.g. Proceratium google. Sean.hoyland - talk 13:31, 23 August 2010 (UTC)

Apparently it is permissible to call an insect "Google" but not "eBay"[1]. Alansplodge (talk) 16:13, 23 August 2010 (UTC)

Such thinking hasn't stopped scientists naming animals after celebrities. Smartse (talk) 16:21, 25 August 2010 (UTC)

Crikey steveirwini is possibly the worst! Smartse (talk) 18:38, 25 August 2010 (UTC)

It's of note that the entire point of using Latin was always that Latin was not much of a "living language" — because it didn't change regularly, it could be relied upon by people who spokes lots of different languages to be a "universal language". Of course, in practice anything that gets used probably "lives" a bit. But the point is still a nice one: use nobody's language when you mean something to be equally understandable in everybody's language. --Mr.98 (talk) 13:50, 23 August 2010 (UTC)

For the same reason, Switzerland uses the Latin form of its name on its stamps (see picture); it's far easier to use just "Helvetia" than inscribing the stamp "Suisse Schweiz Svizzera Svizra". They've issued a few stamps in modern times with significant amounts of text, but (if I remember rightly) in such cases they'll generally issue several different stamps with no differences except the language of the inscription. Nyttend (talk) 12:11, 24 August 2010 (UTC)

Key gets tight in lock

I have a lock that worked well. After I transferred it to another door, the key suddenly became very tight in the lock. It is very hard to push the key in. What could be causing this? --Chemicalinterest (talk) 14:10, 23 August 2010 (UTC)

When the key is hard to push into a lock, this can usually be solved simply by lubrication. Perhaps the process of transferring the lock from one door to another caused a slight change in alignment of the internal parts, leading to a higher-friction arrangement. A little graphite should fix the problem. Dry hem (talk) 14:25, 23 August 2010 (UTC)

Maybe you overtightened it? Or maybe the lock is slightly miss-aligned in the new lock, perhaps the hole for it is not as large or in the right place? Ariel. (talk) 18:38, 23 August 2010 (UTC)

I did some analysis on the lock (it is a keyed entry) and one of the pins inside seem to be bent. I just threw away the lock because I do not think that the pin can be adequately unbent. Thanks for the hints though. --Chemicalinterest (talk) 20:17, 23 August 2010 (UTC)

Sunny side condensation

I park my car every night outdoors in my driveway. On days that are dewy in the morning, there is often condensation on my car's windows, but rarely on all of them. In fact, the condensation is usually only on the windows that face the morning sun. Although the sun is not warm and bright in the morning hours, shouldn't those windows be the warmest ones, and therefore the ones with least amount of condensation? Dry hem (talk) 14:25, 23 August 2010 (UTC)

My guess is that the sun evaporates more dew from surrounding objects than the shade does, creating a sort of supersaturated atmosphere which readily condenses on the car windows. Where the sun doesn't shine the water doesn't evaporate so there is not as much condensation. Only a guess though. --Chemicalinterest (talk) 16:03, 23 August 2010 (UTC)

Is the condensation on the outside or the inside of the windows? 87.81.230.195 (talk) 16:37, 23 August 2010 (UTC)

The condensation is on the outside. Dry hem (talk) 15:35, 24 August 2010 (UTC)

Water condenses on cold surfaces - it seems more likely to me that the water is condensing onto the windows the previous night - so the side of the car that the sun set on (the West) stayed warmer for longer and the water therefore condensed on the Eastern side of the car where the window got coldest, soonest. Since the sun rises in the East - you'd see the condensation on the side of the car nearest the sunrise the following morning. SteveBaker (talk) 22:22, 23 August 2010 (UTC)

The car is generally in the shade late in the day, so the two sides of the car should start the night at about the same temperature. Dry hem (talk) 15:35, 24 August 2010 (UTC)

The sun could be a red herring. It could have to do with air-flow. If you park your car somewhere where a fog regularly rolls in from the east, you'd expect to see that pattern. Happened all the time in the house where I grew up, surfaces that faced the marsh would be covered in dew, but surfaces that faced away wouldn't be. APL (talk) 02:27, 24 August 2010 (UTC)

I'm not sure exactly which way the wind tends to come from, but this answer is (at the very least) consistent with my observations. Dry hem (talk) 15:35, 24 August 2010 (UTC)

Abiogenesis and RNA

So I understand that RNA could possibly form on its own due to crystalization of salt water bringing nucleic acid bases together, and these polymerize into RNA. But how did the nucleic acid bases like Uracil, Guamine, etc form in the first place? I know how Amino Acids, and peptides can form naturally. Are they related? 148.168.127.10 (talk) 14:23, 23 August 2010 (UTC)

The abiogenesis article talks about the possible origins of nucleotides (search for "uracil" and others in that article). The RNA world hypothesis, the specific type of abiogenesis you mention, has more details about the issue and difficulties in original-sourcing. One recurring comment I see is that "the nucleic acid bases like Uracil, Guamine, etc" are just the components of RNA as we know them today, but the same ideas could be applied to alternative bases. To answer your final comment: no, nucleotides and amino acids are not structurally related. They chemically interact and one can encode another in certain situations, but the compounds themselves are drastically different from each other. DMacks (talk) 15:50, 23 August 2010 (UTC)

Yeah, I checked those articles before, but I couldn't find anything. The RNA article does state, "Since there were no known chemical pathways for the abiogenic synthesis of nucleotides from pyrimidine nucleobases cytosine and uracil under prebiotic conditions, it is thought by some that nucleic acids did not contain these nucleobases seen in life's nucleic acids." So is the formation of nucleic acids bases currently unknown?

No, I didn't mean if they were structurally related, I was wondering if amino acids could have led to the formation of nucleic acids or if they are unrelated. I don't know if I'm phrasing this correctly... I know that amino acids can lead to the formation of peptides, and eventually protiens. I want to know if they can also lead to the formation of nucleic acid bases found in RNA. 148.168.127.10 (talk) 17:15, 23 August 2010 (UTC)

None of the "origin of life" experiments actually develops working enzymes - if they ever do, you'll hear researchers trumpeting to the heavens that they've evolved "life" in a test tube. Without catalysis, an amino acid is one compound and a nucleic acid is another, and they're not the same. They are all similar - carbon, nitrogen, oxygen, hydrogen, with a dash of sulfur or phosphorus for specific compounds.

Purely as a matter of speculation, I once devised a rather elaborate scheme by which I hypothesized that RNA chains might once have been converted directly into proteins by a splicing-like process. This was based on the modern (and universal) pathway of biosynthesis of histidine and tryptophan from PRPP. But it's far too elaborate to go into here. Wnt (talk) 18:12, 23 August 2010 (UTC)

Human feeding

How rarely can a human be fed and still remain alive? Let's use a healthy young adult with no health issues, who's not overweight or underweight, is not pregnant, etc. If this human is given one hour every week to eat as much food as she wants, can she stay alive? How about one hour every two weeks? What are the health issues associated with such intermittent feeding?

This question stems from a story I read where a girl was held captive and fed only once every week, and managed to live quite a while. I was skeptical as to whether this was possible. --121.29.125.172 (talk) 14:40, 23 August 2010 (UTC)

Assuming you need 1,000 food calories a day to survive, then you would need to eat 7,000 food calories in one meal to maintain the minimal standard. Very, very few humans would be able to consume that amount of food (equal to 13 Big Mac hamburgers). One could I suppose try to eat 2 pounds of butter to meet pure calorie needs, but then they would not get any of their other nutrients. You also need to consider that some nutrients can not be stored in the body, like vitamin C. So knowing this, I would say that it is not possible to survive long term on this feeding schedule. It will make a person utterly miserable, and while it might make them starve to death slower, it would still not be sustainable. Googlemeister (talk) 16:16, 23 August 2010 (UTC)

If you made a vitamin fortified brownie and could eat 2kg of them in an hour according to this you'd get 8,000 calories, you'd probably be sick though! It's important to bear in mind that the stomach shrinks when you don't eat, so if you went a week without eating, you'd be able to eat less than if you only went a day. Smartse (talk) 16:30, 23 August 2010 (UTC)

Big bag of chips, large can of cashews, container of string cheese... I don't think it's hard for some people to reach 7000 calories. But I think most extraordinary claims involving food come down to semantics. You typically end up finding out that "a little juice" or some stale bread or something was left out of the original count. Wnt (talk) 17:22, 23 August 2010 (UTC)

You don't necessarily need 1000 calories per day to stay alive for months or years of slow starvation. Elizabeth Hughes (edited to direct to the name used in the Wikipedia article) was diagnosed with Type 1 diabetes before the invention of insulin, and was put on a slow starvation diet which kept her from dieing of diabetic ketoacidosis or other organ damage from high blood sugar. Per "The fight to survive, (Cox, 2009)" she started at 14 years of age and 75 pounds in the fall of 1918, and slowly dropped to 45 pounds and the brink of death by the summer of 1922 when insulin became available. She was fed an average of 400 calories a day for very extended periods. The body digests fat and then muscle. Victims of Nazi slave labor camps, prisoners of war held by the Japanese in WW2, and prisoners in Soviet gulags were worked to death similarly and made to use up their bodies' stores. Old-time diabetics, COPD or cancer patients similarly wasted away on deficient calories. Accounts of persons rescued from vile captivity show concern by doctors not to suddenly feed them big meals, although Miss Hughes was immediately given 1100 to 1200 for ten days, then quickly advanced to 2500 calories per day, and more than doubled her weight in a few months. A starved animal, suddenly given unlimited food, often gulps down a lot and throws up. In the hypothetical story, reduced stomach volume might be a problem, If the person could fill the stomach with water on starvation days, I wonder if that would allow him to fill it with food on binge day? Edison (talk) 19:09, 23 August 2010 (UTC)

Her article is at Elizabeth Hughes Gossett, it has little details though. Ariel. (talk) 20:02, 23 August 2010 (UTC)

It is great to note that she had a long and presumable happy and fulfilling life after insulin became available and she could actually eat food. Edison (talk) 02:30, 24 August 2010 (UTC)

It's not so much the underfeeding as the intermittent feeding that you're wondering about, right? There's an article on "refeeding syndrome" which says: "significant risks arising from refeeding syndrome include confusion, coma, convulsions, and death." So it doesn't sound like being able to eat only one hour every week would be very healthy. I don't know if the exact limits of that sort of thing have ever been experimentally determined, but something like it seems to have been done in the Minnesota Starvation Experiment. Wikiscient (talk) 17:54, 23 August 2010 (UTC)

Re-feeding only happens if someone was starved previously. I think the 1000 calorie minimum food number is incorrect though. If someone is very passive and moves little, I think the minimum number is much lower than this. This talks about 800 a day - including exercise! I could not find a direct ref, but based on the holocaust I think the minimum is closer to 300, (500 including activity). So if your prisoner got 2100 calories in this weekly meal they could live for a very long time, assuming they rested almost constantly. Ariel. (talk) 18:54, 23 August 2010 (UTC)

A 470 g pizza might have 1200 calories, and two cans of Coca Cola would be 310. Add a banana split at DQ with 510 calories, and you have 2020 calories in one meal of a size that many gourmands have eaten and lived. One such treat per week would average 289 calories per day, still less than Miss Hughes (cited above) got over a period of 4 years or so of the old diabetes starvation diet. I can't picture eating a bigger meal than that if I had gone all week with an empty stomach. Even if one started as a 75 pound girl, and even if one could keep down all the food and digest it efficiently, it would be less calories than the slow starvation diabetic diet provided to Miss Hughes in 1919-1922. If an antinausea drug prevented regurgitation, and a feeding tube were stuck down the throat into the stomach, maybe a high calories food could be used to quickly fill the stomach. The max volume and the max nutrient content would be helpful information. Edison (talk) 19:26, 23 August 2010 (UTC)

But the OP wanted to know about the case where "this human is given one hour every week to eat as much food as she wants". The problem here is going to be refeeding syndrome as I posted above. So it's not about the average caloric intake over the course of that week, and it's not about stomach shrinkage either so much as about suddenly shifting out of the "starvation mode" of metabolism as described in refeeding syndrome#syndrome. The caloric content of that one meal a week might be enough to keep her alive for a week, but its ingestion will lead to serious physiological complications every week, too. That can't be healthy, but it's probably not known exactly how much of a process like that would kill a subject. Wikiscient (talk) 20:11, 23 August 2010 (UTC)

You would have more trouble without water than without food. Human body stores fat to use as energy source to survive with no food, and I believe that when the fat is gone other tissue also can be used. Some people acctualy don't eat for extended periods of time on purpose, you may want to research them - I once read one such persons claim that her record of not eating was 29 days in a row. Eating once a week sounds pretty realistic to me, especialy if one gets to eat as much as they want, I don't think one week is enough to cause so severe malnorishment that it would cause refeeding syndrome. Also on avarage recomended diet is 2000 calories a day (varies depending on gender, lifestyle and if you are overwight or not). However there may be a diffrence between how long one can willingly survive without food and not being fed in captivity as a prisoner will also have to cope with stress and possible abuse ~~Xil (talk) 22:02, 23 August 2010 (UTC)

Well, the Starvation mode article does say: "People who practice fasting on a regular basis [...] can prime their bodies to abstain from food without burning lean tissue." So, I guess something like that would probably happen in this case, too, and so there probably would not be a refeeding syndrome issue as I figured above there would be. :S Wikiscient (talk) 22:27, 23 August 2010 (UTC)

Nobody has mentioned the issue I was thinking of: can the digestive system absorb an arbitrary amount of nutrients in the time that a meal takes to pass through it? If somebody eats a huge meal with 2200 calories' worth of food, how much of it would be absorbed compared with, say, if the 2200 calories were spread out over 7 days?

An additional question: would this intermittent feeding achieve its goal of making the prisoner perpetually suffer hunger cramps, or at least severe discomfort? In the story, the point is to make the prisoner suffer, not to run a medical experiment. --121.29.115.22 (talk) 17:37, 24 August 2010 (UTC)

Can planets form and orbit around a white dwarf or neutron star?

Topic says it all. 148.168.127.10 (talk) 14:45, 23 August 2010 (UTC)

A white dwarf is the final remnant of a low-to-medium mass star that has exhausted its nuclear fuel supply, so it is as likely to have planets as any main sequence star, although any inner planets may not have survived if it passed through a red giant phase. A neutron star is the remains of a supernova event, so you would think it was unlikely to have any remaining planets; but, surprisingly, some neutron stars do have planets - see pulsar planet. Gandalf61 (talk) 14:58, 23 August 2010 (UTC)

I should have clarified this a bit better. Accretion disks form around white dwarfs and neutron stars (although I don't know if this is always the case). Now in our system, the planets were formed by the accretion disk surrounding the proto-star that later became our sun. Can the same thing happen in accretion disks surrounding white dwarfs/neutron stars or is that matter doomed to fall into the star? 148.168.127.10 (talk) 15:05, 23 August 2010 (UTC)

An isolated stellar remnant (e.g. white dwarf / neutron star) is unlikely to have an accretion disk as there is no new material to accrete, and all the original material was eliminated during the main sequence life of the star. In general, when we talk about an accretion disk for these objects it is usually because they exist in a binary system and are stealing material from a companion star. That kind of accretion disk would be dominated by hydrogen and helium, and be unlikely to contain enough heavy elements to form planets. Dragons flight (talk) 19:11, 23 August 2010 (UTC)

So we don't know of any white dwarf/neutron stars that have accretion disks without a larger companion star near by? 148.168.127.10 (talk) 20:12, 23 August 2010 (UTC)

I suspect that one could find some exceptional cases (e.g. neutron star fed by flying through a giant molecular cloud, or some such), but accretion from the interstellar medium is usually too inefficient to be appreciable. So, in general, you are only likely to have an observable accretion disk for a stellar remnant when it is being fed by a nearby companion. Dragons flight (talk) 23:54, 23 August 2010 (UTC)

tomatos

YEARS ago someone told me or maybe I saw a tv program that said that sewers have LOADS of tomato plants growing there, because of all the tomatos people eat the seeds end up at the sewers. Is this true? —Preceding unsigned comment added by Prize Winning Tomato (talk • contribs) 15:40, 23 August 2010 (UTC)

Very little light in sewers, therefore photosynthesis can't occur. Do trolls eat tomatoes? --Mark PEA (talk) 15:50, 23 August 2010 (UTC)

Go ahead, throw the food on the ground; the troll isn't there.--Chemicalinterest (talk) 16:01, 23 August 2010 (UTC)

What about open sewers? Also, I don't mean the pipes as such, I mean more wherever it all ends at like a treatment plant or whatever, where they clean the water. —Preceding unsigned comment added by Prize Winning Tomato (talk • contribs) 15:57, 23 August 2010 (UTC)

(edit conflict)According to this you are correct, but it doesn't make it clear where they are growing in the sewers. _{A lack of light didn't stop this pea growing.}Smartse (talk) 15:59, 23 August 2010 (UTC)

It says they aren't growing in the sewers, but at the treatment plant, where the sewage dries and is presumably exposed to the light. --Mr.98 (talk) 16:48, 23 August 2010 (UTC)

They do grow where the solids are exposed to the air and left static, but it would be unwise to eat any as sewage contains a lot of heavy metals. On the other hand it is sometimes used for agricultural fertilizer. I wonder how the solids are otherwise disposed of. 92.28.246.109 (talk) 21:51, 23 August 2010 (UTC)

More confirmation, again from Northern Ireland. --Tagishsimon (talk) 22:23, 23 August 2010 (UTC)

And a more scientific (and less recent) confirmation. This research found that using sewage sludge as fertiliser for tomato plants doesn't lead to higher levels of heavy metals. Smartse (talk) 23:57, 23 August 2010 (UTC)

They still could absorb a lot of the toxins in sewage.Smallman12q (talk) 16:18, 25 August 2010 (UTC)

Since I saw this in The Telegraph (also about tomatoes funnily enough) I don't really trust their reporting on plant related matters. I'm not sure which toxins you're referring to (it's a pretty broad term!) but most are broken down in the soil or in the plant. I've been doing a fair of reading on bioremediation recently but haven't seen any mention of this. Smartse (talk) 21:34, 27 August 2010 (UTC)

Honey

Is it true honey doesn't go off? —Preceding unsigned comment added by Prize Winning Tomato (talk • contribs) 15:41, 23 August 2010 (UTC)

Bacteria won't grow in it. It can get moldy, though. Looie496 (talk) 15:53, 23 August 2010 (UTC)

Yes: Honey#Preservation. Moulds can only grow on top of it. Smartse (talk) 15:54, 23 August 2010 (UTC)

what's the (then) oldest honey anyone's eaten? 92.224.207.105 (talk) 18:05, 23 August 2010 (UTC)

Very old. Some honey was found in an Egyptian tomb, and the explorer tasted it. (Most of the refs are from hone-health sites, I didn't find any original sources of this.) Ariel. (talk) 18:59, 23 August 2010 (UTC)

This newspaper claims that honey from 1400 B.C. is kept in the Agricultural Museum in Cairo, but it is doubtful anyone has recently eaten from it! Nimur (talk) 20:44, 23 August 2010 (UTC)

Yes, it is true. Dolphin (t) 22:31, 26 August 2010 (UTC)

A couple questions for a sci-fi world

I'm starting up a campaign for an rpg, so I'm only really looking for approximate answers. The first question being-If a colony ship landed on a planet and it was of a homogeneous group (IE all white/black/asian) and they spread out over a planet similar to earth, how long would it take before they broke up into different races? Are we talking 100s of years, 1000s or 10s of thousands? The second question, is I'm wondering what sort of effect having year long days would have on plant life. The planet I'm thinking of making would have very little spin, so it would be the travelling around its sun that made the day change into a very long, cold night, making most of the population migrate with the dawn/dusk to avoid the really harsh climates. Would plants (as we know them at least) respond well to the year of light, or would it be too brutal for them to grow? I'm also thinking of having eclipses of the sun with the moons bringing storms and such. Realistic?

Thanks for any help 68.149.151.242 (talk) 16:43, 23 August 2010 (UTC)

Answering each separately:

• Racialisation: The degree to which different populations diverge is a function of how richly they interact with one another. If your colonists quickly spread across the new world and then (perhaps due to some catastrophe) lose the capacity to travel long distances, you're back to the the condition of pre-historic humans. Mitochondrial Eve lived as recently as 45,000 years ago, so you get at least as much diversity as humans now exhibit from separation of that time (if your fantastic planet is more restrictive of motion, probably you'd get a bit more diversity sooner). If, on the other hand, the colonists retain the technological civilisation they arrived with, and can travel with aircraft etc. then it's quite credible that there would be much less diversity (more of a kind of spread of a single continuous population). If you want to justify diversity, you'd want a) major barriers to intermixing, like oceans, mountains, deserts and b) environmental diversity (really cold places, really hot places, etc.) - modern humans are (rather badly) adapted to the different climates to which they're indigenous. If you want much more diversity (aqua-men, flying-women, volcano-livers, desert burrowers) then you'll need a radically more varied landscape (super-tall mountains, super-deep dry valleys, giant forests, voids under glaciers full of life) and 10 to 1000 times as long. But it's SF, so you can fudge evolution away altogether - they racialised, or even speciated, deliberately, using genetic technology (perhaps now lost). See pantropy for this. Frankly if I was playing an SF game and the only differences between the tribes of people was trivia like skin colour and eye shape, I'd be pretty disappointed. Mer-men fighting the arborial sloth women - now that's fiction.
• Plants: the situation to describe is very similar to what plants in the high arctic have to endure right now (maybe 3 months of constant sunlight, six months of twilight, and three months of near total darkness). Brian Aldiss' Heliconia novels describe a planet which has hugely long (millenia) seasons, so that might interest you.
• Eclipses: eclipses on Earth are rare and mostly inconsequential because Earth has one moon, which is small enough and far enough away to barely cover the Sun (and Earth's moon is really very big compared with those of other planets), and because it rotates around the earth on a plane that isn't the ecliptic. If you want eclipses to be more than an occasional novelty, you need one or several moons on the ecliptic and ideally subtending a much bigger angle in the sky than the sun does. That means they're either much closer or much bigger than Luna; I suspect you'd get more fun out of the wacky tides this would cause than the storms. Some (very unrealistic) science fiction puts small moons in the atmosphere (the moons of Mongo in Flash Gordon) which means they can (with difficulty) be travelled to. In reality this would have devastating environmental effects, but you can always say "it's that way because some ancient technology (tractor beams, whatever) makes it so".

But frankly planets are for squares. If you want real diversity, and a milieu that's not just "20th Century California in Space", get yourself a Dyson swarm and the worlds are your oyster. -- Finlay McWalter ☻ Talk 17:22, 23 August 2010 (UTC)

For the first, I'd guess more than tens of thousands of years, and even more if it's a modern (mobile and intermixing) society.

For the plants, the year of dark might be a bigger problem, depending on what you're doing with temperature. Sci-fi or fantasy, though, this is an area where you can do some handwaving and move on. Plants are very hardy, or hibernate well, or they're giant colonial organisms and survive by covering both dayside and nightside, or whatever. On the surface, however, this sort of Mercury scenario rules out recognizable megaflora.

For eclipses, not realistic at all. Eclipses have no effect on Earth's weather, and the rigors of orbital mechanics mean that Earth eclipses are a very good projection for eclipses generally. However, you might pull off something like Io and its interactions with Jupiter's magnetosphere. — Lomn 17:26, 23 August 2010 (UTC)

Races are social constructs, and can arise (and be persecuted) very quickly. See Burakumin. Or consider American myths/prejudices about blondes, brunettes, and redheads. There is no predetermined amount of difference that makes a geographic or caste variant of humans distinguishable by cultural prejudices.

If you want a physically distinct race, then consider that the differences between current races represent roughly 10,000-100,000 years of largely random change, though certain features such as skin pigmentation and stature were also clearly influenced by sun and cold exposure. This rate doubtless can be sped up drastically if the environmental circumstances are severe and differ between your regions to force rapid selection. Note that natural selection doesn't actually have to mean death, if people can freely migrate between regions and choose the one best suited to them; the traits simply have to be removed from local populations by some means. Likewise a racist regime would have a major impact, if they send brunettes to the Camps and blondes to the Breeding Pits (or vice versa, depending on the Führer's tastes). Wnt (talk) 17:38, 23 August 2010 (UTC)

Regarding races, note that the colonization of the Americas is thought to have occurred on the order of 15,000 years ago, pretty much everywhere at once, and there has been pretty minimal racial divergence since then. So I would say tens of thousands of years. Looie496 (talk) 01:04, 24 August 2010 (UTC)

Ah, that brings up another point: genetic diversity. Native Americans have been said to have originated from a very small number of Asian founders (though I doubt that all of the peoples of the Americas have been properly studied...) The lack of initial genetic diversity makes it harder to create new racial characteristics by genetic drift or selection from a pool of ancestral traits. Note however that race is cultural: as noted in Human genetic variation, sub-Saharan Africa, where humanity began, has the greatest phenotypic variation; and Africa as a whole is the one continent with all three of the main genetic subdivisions of humanity - yet in many societies there is very little sense of distinction made between any of these people. I would even go so far (too far, expert opinion would say) as to speculate that the next human species may already have evolved there, like so many before it, and awaits only the opportunity to escape from persecution to the shaping rigors of interstellar travel... Wnt (talk) 05:30, 24 August 2010 (UTC)

Libellula

Are these two dragonflies Libellula pulchella or Libellula forensis (or perhaps some other Libellula species)? Thanks, --The High Fin Sperm Whale 16:49, 23 August 2010 (UTC)

Looks like male L. forensis to me. Almost certainly not L. pulchella or Plathemis lydia. --Dr Dima (talk) 17:21, 23 August 2010 (UTC)

Galilean moons

Are all the Galilean moons tidally locked with Jupiter? Are there any of the large moons (say 1,500km diameter or larger) not tidally locked with their planet? Googlemeister (talk) 18:50, 23 August 2010 (UTC)

1. Yes, 2. No. There is a detailed list and discussion in Tidal locking. --Dr Dima (talk) 19:36, 23 August 2010 (UTC)

See Io (moon)#Tidal heating. ~AH1^(TCU) 19:28, 26 August 2010 (UTC)

What bug is it?

The critter from Hawaii

Could anyone tell me the name of the critter I saw in the picture? It was very peculiar looking.Smallman12q (talk) 22:25, 23 August 2010 (UTC)

Looks like an Earwig. -- Finlay McWalter ☻ Talk 22:29, 23 August 2010 (UTC)

Ye that looks right...thanks!Smallman12q (talk) 22:43, 23 August 2010 (UTC)

Which of the 1,800 species though? Smartse (talk) 23:44, 23 August 2010 (UTC)

Try posting it on What's That Bug?. Richard Avery (talk) 07:12, 24 August 2010 (UTC)

Maybe no need for that, "hawaii earwig" in google brings up this page about the imaginatively named black earwig (Chelisoches morio) which looks very similar. Smartse (talk) 12:56, 24 August 2010 (UTC)

Thanks! I've also started a stub on it.Smallman12q (talk) 13:24, 25 August 2010 (UTC)