Wikipedia:Reference desk/Archives/Science/2015 March 6

Science desk
< March 5	<< Feb | March | Apr >>	March 7 >

Welcome to the Wikipedia Science Reference Desk Archives
The page you are currently viewing is an archive page. While you can leave answers for any questions shown below, please ask new questions on one of the current reference desk pages.

March 6

Can regular cheetoes use really stain your fingers orange?

Question as topic. Sort of along the lines of how smoking unfiltered can turn your fingers brown... Just something that I was discussing with a friend today. --Kurt Shaped Box (talk) 00:44, 6 March 2015 (UTC)

Temporarily, certainly. Surface stains on the skin don't usually last very long. ←Baseball Bugs ^{What's up, Doc?} carrots→ 01:23, 6 March 2015 (UTC)

Oh yes, I know that they can make your fingers orange until you wash it off - but I was meaning long-term, like with cigarettes. Yaknow, if you were to eat cheetoes every day, would little bits of the orange colour stay on your skin and gradually build up? --Kurt Shaped Box (talk) 01:41, 6 March 2015 (UTC)

Cheetos' dyes are presumably excretable; certainly this is true of their "red hot" dye, which in a scene straight out of Cujo sent kids to the emergency room because parents thought they were bleeding internally (difference being that in the real world, this generated nothing but a passing news blip, no "I'm sorry" campaign needed!). The regular version contains (at least) Red 40 Lake, Yellow 6 Lake, Yellow 6, Yellow 5. [1]; in order for it to stain fingers one or more of these would have to find some way to pass into the dermis without interacting with the outer layer of skin, and stably bind onto cells there so that it wouldn't be destroyed. Can I rule it out? Well, no... not without a whole lot of data. But it's hard to picture. To begin with, those sorts of snacks don't even really stain fingers, not like a pomegranate or something (I mean, the old-fashioned super red pipped ones that seem to grow ever rarer; nowadays they don't seem to leave me yellow-fingered at all). You wipe your fingers after Cheetos and the color leaves with the crumbs, is my impression. What the dye does internally is apparently the topic of more spirited discussion, but you didn't ask that. Wnt (talk) 01:59, 6 March 2015 (UTC)

The top layer of skin is regularly shed, so it would have to get below the growing skin to become permanent, like a tattoo. I have a splinter that managed to do that, and the wood stain on it is still there some 30 years later (although greatly faded). So, I suspect a puncture would be needed to get the orange dye that far in. StuRat (talk) 06:40, 6 March 2015 (UTC)

Right. And I would like to see some evidence that cigarette smokers have permanently stained fingers. More likely they appear "permanently" stained because they continue smoking. Like with teeth stained by tobacco use. ←Baseball Bugs ^{What's up, Doc?} carrots→ 17:47, 6 March 2015 (UTC)

It's not a *permanent* stain. It just a stain that takes a while (two or three weeks, I think it was whenever I've stopped) to disappear entirely after you stop smoking. --Kurt Shaped Box (talk) 18:48, 6 March 2015 (UTC)

It goes faster with whitening toothpaste and steel wool. I still smoke, but don't like the look. InedibleHulk (talk) 18:46, 7 March 2015 (UTC)

Bingo. And if you were eating Cheetos constantly for some stretch of time, you might encounter that same problem (among others). Did you try soaping up with the kind you can use to wash off grease and the like? Or maybe a soap like Lava which has particles of pumice? ←Baseball Bugs ^{What's up, Doc?} carrots→ 05:31, 7 March 2015 (UTC)

Seconds of daylight gained or lost

How many seconds of daylight are gained or lost each day after solstice?Joey13952 alternate account (talk) 01:01, 6 March 2015 (UTC)

It isn't a constant number per day, and it varies depending on your exact location on earth. This website has all sorts of tools for calculating all sorts of things, I've linked directly to the page where you can search for the data you seek. Just enter your location, and it will give you tables of sunrise & sunset times, along with calculated time of daylight for any given date. --Jayron32 02:19, 6 March 2015 (UTC)

I believe it's sinusoidal, so there is very little change around the summer and winter solstices, and rapid change near the vernal and autumnal equinoxes. StuRat (talk) 06:18, 6 March 2015 (UTC)

Broadly it is, but because the Earth's orbit is not perfectly symmetrical, it means the behavior of daylight also isn't regular. See Analemma for a related discussion of the apparent position of the sun at various dates. --Jayron32 15:48, 6 March 2015 (UTC)

That's the fine detail. The broad effect is simply the inclination of the rotation axis to the plane of orbit. Dbfirs 16:01, 6 March 2015 (UTC)

We should also mention why the location on Earth matters:

1) Above the arctic circle and below the antarctic circle, you actually get some 24 hour days and 24 hour nights. So, the differences in daylight minutes each day will change more rapidly there, than in the tropics.

2) If you are at the top of mountain, you get more daylight minutes than if at the bottom of a deep valley. That's because the Sun sets behind those valley walls earlier than it would, if they weren't in the way. StuRat (talk) 17:56, 9 March 2015 (UTC)

Digging into Vesta

The protoplanet 4 Vesta is said to have a differentiated interior - mantle and iron core. It has a radius of roughly 260 km. With gravity just 1/40 that of Earth's (and considering that it drops to zero at the middle) that should be the rough equivalent pressure of 3-4 km depth on Earth. Which is to say, it should be physically conceivable for a tunnel boring machine to grind its way steadily to the core (with rather more difficulty than crossing the English channel, and I imagine the iron would tax the blades terribly once it reached the core). So...

• 1) Is the core cool? It was once liquefied by Aluminum-26, which should long since have decayed... since 4 Vesta is so small I'd expect it to be cooler inside, but how cold?

• 2) Would any sort of caverns be expected deep in Vesta, perhaps analogous to the cenotes of the Chicxulub crater?

• 3) Was there ever a sort of plate tectonics on Vesta during its initial cooling period?

• 4) Is there pressure, even atmosphere and water, in void spaces within the asteroid? That 3-4 km to essentially hard vacuum means that air would rapidly be lost from an open tunnel, but would the cooled exterior layers of rock be impermeable to their loss even over billions of years?

• 5) Would the complete cooling of core and mantle, if it happened, make for deposits of unusual minerals? For example, when freezing an iron core slowly, do vast layers of solid gold and platinum come out, or do they stay mixed in to the end? Would differential contraction create a fracture zone at the core/mantle boundary?

Wnt (talk) 01:45, 6 March 2015 (UTC)

(I added numbers):

1) A body that small which existed since the formation of the solar system, should be quite cool by now, unless it was actively heated by some means, such as tidal heating from a nearby planet. StuRat (talk) 06:26, 6 March 2015 (UTC)

@StuRat: That's what I'd expect, but is there an actual model or empirical rule to go by? (Conceivably there could be long-lived radioactives inside, etc., and I don't know if a lack of plate tectonics or a more solid mantle slows the rate of cooling, etc.) Wnt (talk) 14:50, 6 March 2015 (UTC)

The square-cube law explains why smaller bodies cool more quickly. However, in the case of planets, there may be an effect which counters that a bit. When still hot, convection moves heat from the center to the surface, where it then quickly escapes into space. However, once a thick crust solidifies, that stops convection from reaching the surface, slowing the rate of cooling. So, if a smaller body initially cools faster, it would also form that crust sooner and thus slow cooling more quickly. However, since all the planets, moons, asteroids, etc. have long ago formed a thick crust, that effect is likely negligible now. StuRat (talk) 20:35, 6 March 2015 (UTC)

But mantle convection... on Earth, the thin layer of crust is 24% of Earth's internal heat budget. If the entire mantle cools and forms "crust" (i.e. non-convecting material) that is 100 km thick or more, 10 times that of Earth, how much heat escapes? Those sort of considerations make me want to see a better calculation. (a pre-Dawn paper here provides some info, but doesn't seem to tell me much about the expected core temperature now, and in any case ... one hopes that the models have improved now that we know what it looks like, e.g. I imagine the metamorphism is easier to understand now that the whole asteroid is known to be circled by ridges from giant impacts ;[2] is more up to date but stops at core formation. [3] is interesting but focuses fairly much on early history - alas, most of these researchers have to focus on accounting for characteristics of observed meteorites rather than catering to sci-fi fantasies - but gives a figure of roughly 100 million years for the iron core to freeze.) Wnt (talk) 23:37, 6 March 2015 (UTC)

If one assumes that Vesta is a solid sphere, then the cooling time scale is of order (thermal conductivity) / (specific heat) / (density) * (radius / pi)^2, which gets me to about 10 billion years if I plug in rock values. Suggesting it is roughly half cooled at the present day. Dragons flight (talk) 04:24, 7 March 2015 (UTC)

If we compare the internal structure of the Moon and Earth, we see that the core on the Moon is much smaller. Since Vesta 4 is much smaller still, and lacks the tidal heating from Earth, I doubt that it would have any liquid or molten core. StuRat (talk) 16:17, 7 March 2015 (UTC)

The core of the moon being small is explained by the giant impact hypothesis. The general view being that the impact occurred after the Earth had already mostly differentiated, so the moon forming debris was low in iron and other elements that would typically participate in planetary differentiation, leading to a small lunar core. The respective cores are about 28% of Earth's mass, < 5% of the Moon's mass, and an estimated 20% of Vesta's mass. More relevant, the temperature at the core of the Moon is still estimated at 1400 C [4]. For the record, I didn't say Vesta was molten. I suggested it was half cooled, as in its core temperature might have declined by about half relative to its temperature at formation. Dragons flight (talk) 19:20, 7 March 2015 (UTC)

I'm more concerned with the temperature than the material. That 1400 C spread over a small core is a tiny fraction of the total heat retained by Earth's core, and the total heat contained within the Moon is also tiny compared to the Earth. When we then extrapolate to Vesta 4, the total heat retained in it's core and entirety ought to be far less, still. StuRat (talk) 02:38, 8 March 2015 (UTC)

Okay, I found a source with some modeling rather than dimensional guessing [5]. It places the interior temperature today between about 75 and 180 C, depending on structural assumptions. In their model, Vesta's core has retained between 20-30% of its initial temperature since differentiation. Dragons flight (talk) 18:06, 8 March 2015 (UTC)

This is indeed an interesting paper. Among other things, it is saying that if the megaregolith is thick, which is reasonably possible, you could go down 5 km or so and find a place at 0 C. This means that a "Journey to the Center of Vesta" scenario can indeed involve a descent through a maze of caverns that presumably are possible in ancient fractured bedrock, happening upon an underground sea of water that has melted in deeper layers, surmounted by some atmosphere that has outgassed... at least, provided that there is some way for the intermediate layers to provide a reasonably good seal against the hard vacuum above, which also remains an open question. Many of my astronomical questions over time seem to lead to the same conclusion: for those with reasonable chemical capabilities, and capable of withstanding great pressures, the question is not whether a planet is habitable, but only where and when. Wnt (talk) 18:53, 9 March 2015 (UTC)

That rather depends on what you consider "habitable". Considering that people can live in space, with a suitable ship and provisions, then a wide range of planets, moons, etc., could be considerable habitable in the same way. On the other hand, if you mean a self-sustaining colony could exist there, then that's a much higher bar, at least given our current technology. StuRat (talk) 20:00, 9 March 2015 (UTC)

Check-engine lights

In general, when did American-market cars change to the present type of malfunction indicator lamp? My 2009 Hyundai has the new type of "icon" that appears at the article's top right, and it took me forever to identify what it was (reading through the manual multiple times), because I'd never noticed such a thing before, although apparently lots of newer cars have these. Conversely, my previous car had an easy-to-understand verbal warning, simply "Check Engine"; it was a 2000, and other cars of the same period appear to use verbal indicators too. Nyttend (talk) 04:36, 6 March 2015 (UTC)

This is an example of a much broader problem. Manufacturers want to be able to sell their products in all markets without modification. Since different markets speak different languages, they therefore want to remove all writing from their products, and replace it all with icons. Sounds good, except that only the simplest concepts can be shown with an icon which is universally understandable. StuRat (talk) 06:14, 6 March 2015 (UTC)

The engine lamp is used to indicate several malfunctions. If the oxygen sensor, in Europe mysteriously called "lambda sensor", is broken or shortcut, the amount of oxigen in the exhaust can not longer be sensed to reduce the fuel injection into the engine. Values from preprogrammed memory are used instead as a running the engine in a backup mode, sometimes consuming more fuel. The former contact breaker to trigger the ignition on the spark plugs, today replaced by the dead centre sensor metering RPM and zero degree as beginn of a engine cycle. If this sensor fails, it is indicated by the engine lamp and the engine can not run, cause the engine controller can not know when to inject fuel or ignite a cyllinder. By turning the key the starter motor is operating only, turning the engine which will not start. --Hans Haase (有问题吗) 14:57, 7 March 2015 (UTC)

This link says lambda is the symbol for air/fuel ratio (in automotive or mechanical engineering, presumably). That's probably the reason behind the "lambda sensor" name. --173.49.18.106 (talk) 17:13, 7 March 2015 (UTC)

The criterion for the existence of the scientific meaning of scientific discoveries (explanations)

1) Did it true the assertion, that failed to comply with the Law of conservation of energy in scientific discoveries (explanations) is always been denied the possibility of the existence of the scientific meaning (know) of these scientific discoveries (explanations)?

2) If magnetic (electromagnetic) fields are always been moving in space at the speed of light or even at the much faster speed, so why did in these magnetic (electromagnetic) fields, the electric current did not had the same speed?--85.141.236.107 (talk) 09:36, 6 March 2015 (UTC)

3) If any magnetic (electromagnetic) fields are always been moved by speed (work) of the electric current, why did the electric current did not had the same speed (work) as had the magnetic (electromagnetic) fields?--83.237.208.214 (talk) 12:58, 6 March 2015 (UTC)

4) If the properties of all substances in nature are always been depended on the properties of the electric current which was had in these substances, so is it possible that the electric current in all environments is always been behaved in the same (identical) way? — Preceding unsigned comment added by 83.237.201.125 (talk) 14:24, 6 March 2015 (UTC) --83.237.201.125 (talk) 14:25, 6 March 2015 (UTC)

---

Note: It is always assumed, that in nature the speed (work) of the electric current is always been absolute, that is, the speed (work) of the electric current is never been depended on the properties of the environments in which the electric current is been.--83.237.201.125 (talk) 14:06, 6 March 2015 (UTC)

Please try writing your questions in English. AlexTiefling (talk) 14:20, 6 March 2015 (UTC)

I’m always assume that in nature all physical and chemical environments are always been conducted an electric current, because in these environments is always been an electric current!--85.140.143.233 (talk) 15:03, 6 March 2015 (UTC)

Yes, you find electricity just about everywhere, and it travels fast like light (see Speed of electricity), and the associated magnetic effect travels at the same speed, but, of course, the electrons themselves (if you can distinguish them) flow at a very much slower rate DC (perhaps a quarter of a millimetre per second in a copper wire) and not really at all for AC where they oscillate a couple of micrometres. Of course the electrons are also "rattling around" within each atom at a speed determined by the Fermi energy if you interpret it that way. Dbfirs 15:58, 6 March 2015 (UTC)

The case is not been in the speed of the electrons in AC or DC, but the case is been in the work of these electrons - the work of the electric current, as the form of electric energy. I’m thinking, that all substances in nature was always had existed under the laws of the electric current!--83.237.218.93 (talk) 16:41, 6 March 2015 (UTC)

Physics did not excluding the scientific fact that different kinds of energy could done its work, including the work of the AC and work of the DC!--83.237.218.93 (talk) 16:56, 6 March 2015 (UTC)

I’m suppose, that in your's countries there are be universal generators which simultaneously generate as AC and as also DC, and of course there are be such universal transformers which simultaneously transform as AC and as also DC.--85.141.232.34 (talk) 17:52, 6 March 2015 (UTC)

I like the idea of universal generators and universal transformers. I suppose Switched-mode power supplies are capable of that magic in a sense. As for all the rest, I haven't the slightest idea what you are going on about, Alex. Dbfirs 18:12, 6 March 2015 (UTC)

I’m suppose based on that, since the work of the electric current (AC and DC) is always been only the kinetic potential of energy (energy - work of dynamics), so in this kinetic potential could always been the potential of potential energy (energy - work of kinetical statics), which as also could been done the work of electric current (AC).--85.141.235.69 (talk) 23:48, 6 March 2015 (UTC)

In any cases, in nature the electric current is always been the dynamics of electric charge, so that in nature all substances (physical environments) are always contained in self an electric current, because in nature all substances (physical environments) are always been electrified.--85.141.238.46 (talk) 06:09, 7 March 2015 (UTC)

The dynamics of electric charge was always had a electrify(-ing).--83.237.207.17 (talk) 07:22, 7 March 2015 (UTC)

Could you please let us know why you think you should be permitted to continue to use this page as a forum for your unintelligible ramblings? AndyTheGrump (talk) 07:36, 7 March 2015 (UTC)

As far as I can tell, these questions are not soapboxing, trolling, disruptive or discourteous. —Tamfang (talk) 08:19, 7 March 2015 (UTC)

As far as I can tell they are not questions. AndyTheGrump (talk) 09:06, 7 March 2015 (UTC)

I’m sorry for my mind suppose discussion, but I must said that the nature of magnetism and electromagnetism is always been the same (equal), as which was always had been the nature of electric current and electric charge. Sorry!--85.141.236.38 (talk) 10:05, 7 March 2015 (UTC)

User is been obvious troll, did not speaking English or Russian, never the yet geolocate to Moscow but never answer if been asked Russian been being language native. Is having been banned on ru.wikipedia accords to other editor. OP speak nonsense about nonsense but not even speak Russian. Never answer he direct answer of this question. Его попросили, если он говорит на русском. Fools continue. μηδείς (talk) 03:55, 8 March 2015 (UTC)

Alcoholic pickles

Can homemade pickles contain alcohol if no alcohol was originally added to the mixture during preparation?73.160.39.193 (talk) 10:31, 6 March 2015 (UTC)

There are traces of alcohol in vinegar.

http://www.drgourmet.com/askdrgourmet/cooking/vinegar-alcohol.shtml#.VPmO8SzLyJ0

http://www.islamawareness.net/Alcohol/fatwa_vinegar001.html

"Acetic acid is produced by the fermentation of ethanol by acetic acid bacteria." If a foreign yeast contaminated your mixture it is possible that fermentation (of the pickles themselves) may produce ethanol (or even methanol which is toxic). Your pickle jar will probably explode.196.213.35.146 (talk) 11:46, 6 March 2015 (UTC)

Thanks. What would vinegar do to a breathalyzer test result?2601:C:3600:46B:34DF:F9E6:2B0F:22E5 (talk) 12:25, 6 March 2015 (UTC)

It's unlikely that the amount of alcohol in most vinegar would even register on the breathalyser, but if your pickles have fermented and you are in a country with a very low breathalyser limit, then perhaps you shouldn't eat a whole jar just before driving. Dbfirs 12:53, 6 March 2015 (UTC)

per Dbfirs, we can't give advice on what you should or shouldn't do. Be aware that many foods contain non-zero amounts of ethanol, but the amounts they DO contain is, while measurable, too small to have an effect on you as you couldn't physically consume enough of the food to have a marked effect on your blood alcohol level. Just because something contains any amount of something doesn't mean it contains a meaningful amount. For example, here's a study: [6] which measured the amount of ethanol in found in the juice of freshly picked oranges and grapefruits in California, and it found about 40 mg/100 mL concentration. For comparison, 5% ABV beer contains about 264 mg/ml concentration (see here for calculation). Thus, you'd need to consume 6.5 times as much orange juice to get the same amount of alcohol as a typical beer. Thus, a non-zero amount, but quite literally almost impossible to get drunk on; you'd need to drink nearly 1/2 of a gallon of orange juice to get the effect of one can of beer, for most people that isn't enough to go over the blood alcohol limit, and consuming that much orange juice would likely make you sick. Additionally, just about any fermented foods, including but not limited to, yogurt, bread, cheese, etc. also probably contain measurable (but insignificant) amounts of ethanol. --Jayron32 15:44, 6 March 2015 (UTC)

Two quibbles:

1. There's a factor of 100x difference between the units mg/mL and mg/100 mL, so it's 650x rather than 6.5x.
2. The figure of 264 mg/mL is not the alcohol content of the beer, it's the blood alcohol level resulting from drinking the beer.

We want to compare the alcohol content on an equal footing. 5% beer is 5% alcohol by volume. It should have alcohol content of (0.05 mL/mL) x (density of alcohol = 789 g/mL) = 39.45 g/mL. This is about 100,000x more than the orange juice. It's like in the old commercials for Total cereal: You'd have to drink a lot of orange juice! --Amble (talk) 17:08, 6 March 2015 (UTC)

Thanks for correcting my math, but now i need to correct yours. Density of alcohol is 789 g/L. 789 g/mL would be far denser than lead (11.34 g/mL). So, the alcohol content in orange juice is 1/100th that of beer, not 1/100,000th. Which makes it even MORE impossible to get drunk by eating oranges. Still, even at 1/100th, it is STILL impossible. --Jayron32 17:34, 6 March 2015 (UTC)

Turnabout is fair play :-) Thanks. --Amble (talk) 17:42, 6 March 2015 (UTC)

Non water based life

Is non water based life possible? — Preceding unsigned comment added by Joey13952 alternate account (talk • contribs) 23:02, 6 March 2015 (UTC)

See non-water based life. Possible, yes, known, no. Tevildo (talk) 00:02, 7 March 2015 (UTC)

More precisely, we don't know if it is possible. Looie496 (talk) 15:20, 7 March 2015 (UTC)

I think of course – Yes, because same chemical reactions in nature could been done without water (or without any more liquid).--85.140.131.223 (talk) 15:56, 7 March 2015 (UTC)

And so, the life on the planet Earth is not been depended on the Sun and water, because in deserts (shadow deserts) the life are been.--85.140.131.223 (talk) 16:14, 7 March 2015 (UTC)

All life we know is cellular. Cells consist of small bubbles with a bi-lipid layer which contain metabollically active molecules, keeping them together and preventing their dilution in the ocean or evaporation in the atmosphere. It seems likely that cells could form in an ocean of ammonia NH3, rather than in an ocean of water, OH2. μηδείς (talk) 17:16, 7 March 2015 (UTC)

It perhaps be, that a biochemical protocells are also been possible.--83.237.196.48 (talk) 17:35, 7 March 2015 (UTC)

You get into trouble with deciding what constitutes "life". Virusses, for example, are not cell-based. Are they "alive"? That's more about the arbitrary definition of that word than about any actual scientific fact. Some people would argue that self-reproducing entities inside computer software (artificial life) is life - and such things can certainly survive very well without water. We could easily imagine an artificially intelligent robotic civilization living on a distant alien world without water...but other people would say "Oh, no! Those aren't alive!"...so without a solid definition for the word, this question is unanswerable.

Our Life article talks about the 'biological' definition of 'life' - which requires that living things are made up of cells...which seems like an odd requirement. If some green skinned alien were to step out of it's flying saucer on the front lawn of The White House and say "Take Me To Your Leader", I doubt we'd say "It's not alive" just because it didn't have cells...so the 'biological' definition isn't what common usage would suggest. An alternative definition is "Life is a member of the class of phenomena that are open or continuous systems able to decrease their internal entropy at the expense of substances or free energy taken in from the environment and subsequently rejected in a degraded form"...which would certainly allow artificial life inside a computer - or self-reproducing nano-machines - to count as "alive" without water. But yet another definition is "Living beings are thermodynamic systems that have an organized molecular structure."...which would allow virusses and nano-bots to count - but not software entities or clanking metal robots with artificial intelligence.

So for some definitions of the word 'life', the answer to your question is "yes" and for other definitions "we don't know" - and for yet other definitions "no".

SteveBaker (talk) 18:42, 7 March 2015 (UTC)

SteveBaker, please add to this the possibilities of gravity.--83.237.196.48 (talk) 19:00, 7 March 2015 (UTC)

Viruses still have envelopes, SteveBaker, and they could not exist without cellular metabolism to hijack for reproduction. Indeed, that's how they are defined. Earth-based life is dependent on the existence of cells in a water matrix with bi-lipid layer containment. Insofar as such cells could exist in a matrix of ammonia, water-based life would not be all that's possible. Methane is also similar, but lacks the polarity of water and ammonia, so it would lead to a radically different type of life. Methanol is polar, but it is also complex, having more than two constituent elements, and the likelihood of an inorganically caused methanol ocean is rather small. μηδείς (talk) 22:06, 7 March 2015 (UTC)

Not all viruses have envelopes - some have nothing more than their 'capsid'. Check out Viral envelope for details. I, personally, agree that all known earth-based organisms that I'd normally consider to be "alive" have cells and water-based chemistry...but I wouldn't want to rule out hypothetical non-earth organisms that were not cellular and didn't require water. This is especially the case in synthetic organisms. But it all depends on the definition of this highly slippery word: "life". Mostly, the definition boils down to "We know it when we see it"...which causes problems for this kind of hypothetical question. Since science has no solid definition that everyone agrees upon, we have to first establish what our OP means by "life" before we can answer the question adequately. Is an intelligent robot "alive"? If "yes" then you don't need water for life. If "no" then...we don't know. SteveBaker (talk) 23:01, 7 March 2015 (UTC)

By envelope I did not mean bi-lipid layer, or I would have said so. I find it ironic that you point me to viral envelope to explain this. Nevertheless you do point out something which I did not go into depth on, and which the OP may find helpful, thanks. The basic concept is, life ase we understand it requires a locally contained self-replicating metabolic agent. Stuart Kauffman's Origins of Order is still the seminal work on this issue. And, of course I won't rule out anything a priori, but I think cellular life with an ammonia matrix is a lot more likely than non-cellular self-replicating 'naked' sulfur or silicon molecules. μηδείς (talk) 03:10, 8 March 2015 (UTC)

• An article on Methane-based life with membranes based on nitrogen compounds suitable suitable for worlds like Titan: http://www.news.cornell.edu/stories/2015/02/life-not-we-know-it-possible-saturns-moon-titan μηδείς (talk) 05:17, 8 March 2015 (UTC)

I think that gravity are always been determined a new possibilities (opportunities) of alive and technics, and as also a new possibilities (opportunities) of mind (new mind apparatus) of intelligent alive forms.--83.237.192.255 (talk) 09:11, 8 March 2015 (UTC)

In my mind, are possibilities (opportunities) of gravity are always been infinite (are more without less), even in the world of biology (biochemistry)!--85.140.136.25 (talk) 10:39, 8 March 2015 (UTC)

The induction (inductance) of the core of atom (molecule) is always been the same as gravity.--83.237.216.191 (talk) 13:06, 8 March 2015 (UTC)

What about life based on radioactive elements such as uranium instead of carbon? — Preceding unsigned comment added by Joey13952 alternate account (talk • contribs) 17:36, 8 March 2015 (UTC)

As for me, the radiation is a weak factor of influence (determine) on alive as opposed to (at different of) the powerful factor - gravity.--83.237.211.217 (talk) 20:35, 8 March 2015 (UTC)

• If you are asking about whether fission could be used as an energy source, then you could just construct large self-reproducing robots that use fusion reactors to run turbines, something along the Doomsday Machine episode of Star Trek.

But there's a reason why plants use visible light and we can see visible light. Visible light is strong enough to catalyze the release of electrons using phot-sensitive pigments without destroying the molecules that run the show. Ultraviolet light is to strong, it disrupts molecular structures. Infrared is too weak, it can't excite electrons sufficiently to power an organism. Vision works on the same principle, visible light can excite eye pigments without destroying the eye structure. This can go up to the lower energy bands of ultraviolet light and infrared canalso be detected, but with a much lower resolution given its lower energy.

Fission produces neutrons, as well as alpha particles, beta particles, and gamma rays. The first are accelerated helium nuclei, the second are high speed electrons ("ionizing radiation"), and the third are very high-energy damaging photons. That would all be to damaging for cellular life. Gravity is no good, because there's no cycle--it's a one-way trip. μηδείς (talk) 21:46, 8 March 2015 (UTC)

"If you are asking about whether fission could be used as an energy source, then you could just construct large self-reproducing robots that use fusion reactors"

Make both of these "fusion", or both "fission", and you're right. ;)

The funny thing is it's probably a typo followed by autocorrect, and fusion became fission. Now what are the typos called where one word becomes a different word? Typo#Atomic typos.

Oh the irony. - ¡Ouch! (^{hurt me} / _{more pain}) 09:59, 10 March 2015 (UTC)

I had an idea of a Borg (Star Trek) queen once, not the one in Star Trek but that the ship itself is the "queen" of the multi-species hive. However, that wouldn't work on TV, missed fanservice opportunity and all that.

On the low end, "living solar cells" could exist; they would grow, move, and multiply via crystalline growth and harvest solar radiation. More advanced species could have a "brain" that works like a microchip.

I wonder if silicon crystals can occur naturally?

Pure iron exists in many asteroids, but silicon is closer to oxygen on the periodic table, so an oxygen-free environment for silicon looks less likely; that could mean no living chips for you. - ¡Ouch! (^{hurt me} / _{more pain}) 08:20, 9 March 2015 (UTC)