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February 16

Very large cube

What is the largest solid steel cube that could, floating in free space, sustain its shape against the force of its own internal gravity (i.e. avoid the tendency to become spherical)? What solid material would allow the largest such cube? 86.133.247.182 (talk) 00:44, 16 February 2010 (UTC)

Any cube would deform to some extent under its own gravity, given that stress produces strain and thus some deformation. So. strictly speaking, no steel cube of any size whatever, even 1 cm, could maintain its form in space, with no deformation whatsoever. How much deformation is tolerable? Likewise, it is unlikely that a humongous cube of steel many lightyears across would become a perfect sphere under the deformation of its own gravity. Edison (talk) 01:17, 16 February 2010 (UTC)

well, I suppose you could reframe this question to read 'how big does a steel cube have to be before its own gravity causes plastic (rather than elastic) deformation, but even given idealized assumptions I wouldn't know where to begin with the calculations. perhaps we should ask the Borg, since they seem to be into the large cube thing.

Are roche limit and hydrostatic equilibrium relavent? ~AH1^(TCU) 01:46, 16 February 2010 (UTC)

I'm pretty sure that a steel cube many lightyears across would become a perfect sphere with radius zero Paul Stansifer 02:13, 16 February 2010 (UTC)

My thought too! 86.133.247.182 (talk) 02:20, 16 February 2010 (UTC)

Why would you think that? A lot of things can be very massive without becoming a black hole. Nimur (talk) 04:29, 16 February 2010 (UTC)

At 7.8 g / cm^3, a steel sphere would exceed the Schwarzschild radius limit at only 2.7 AU (415 million km). Any cubic solid that is light years across is already doomed to be a black hole. Dragons flight (talk) 05:09, 16 February 2010 (UTC)

Oops.My hyperbole collapsed under its own weight. I intended just to make the point that as steel cubes became larger and larger they would deform, but as they approached a sphere some small trace of the corners and edges might be seen. Edison (talk) 16:09, 16 February 2010 (UTC)

@Edison: If you like, turn the question round and ask what would happen to a cube, say, 1,000 miles across, or 10,000 miles across, and so on. I'm only after ball-park ideas. For example, would a cube 1,000 miles across, or 10,000 miles across, or whatever, remain a cube as far as you could visually distinguish from a distance, or would it noticeably sag, or would it be completely mashed? 86.133.247.182 (talk) 02:20, 16 February 2010 (UTC)

When discussing possible definitions of "planet" some 11 years ago, I came across the following passages in the junior-level The Universe and Planet Earth by Josip Kleczek and Petr Jakeš (Artia, Prague 1985; Translated by Stephen Finn, Octopus Books, London 1987) -

Figure 48 on p35 shows a crystal, a rock, a 500 km-diameter irregular asteroid and a larger, rounded, internally molten body, with the caption: "Small bodies are kept together by electromagnetic force, large ones by self-gravitation."

Discussing crystal structure, text on pp58-9 reads: " . . . The energy released by the crystal during its growth is also called binding energy. The greater it is, the more stable the system of molecules - the crystal - is, and the more resistant to external influences. It must be heated to a higher temperature before it melts. Or a greater pressure must be exerted on it to crush the crystal lattice. In the interior of solid bodies consisting of more than 10⁴⁶ elementary particles (Figure 48) self-gravitation is strong enough to achieve this."

Text on p61 discussing solar system bodies reads: "Small solid bodies made of rocks, such as meteoroids, the nuclei of comets, small satellites and the vast majority of minor planets, are held together by electrical force. Their mass is small, so their self gravitation is also low. [Various examples elided] Inside solid bodies more than 500 km (310 miles) in diameter the self-gravitation is so great that it breaks up the crystalline structure of the rocks. The solid rock thus becomes a pliable, dough-like material where the pressures in different directions are evened out. The irregularity of the body thus disappears: tall projections are heavy and sink downwards towards the middle while light, thin parts of the body (depressions) are pushed through the doughy material to the top. This is called isostatic equilibrium. The body tries to assume a round shape through its own gravitation (Figure 48)."

The figures of 10⁴⁶ elementary particles and 500 k (310 miles) diameter (which I've not come across elsewhere) may be of relevance - I suspect the difference between rock and steel at these dimensions may not be very significant. 87.81.230.195 (talk) 03:32, 16 February 2010 (UTC)

I beg to differ, only because my exoplanet geology textbook classifies planetary formation geology into three types of material: "things that are like water," "things that are like silica," (rock), and "things that are like metal." (They use a little more technical terminology, but I left my copy in my office, so I'm glossing over the details). Iron is much denser and has a variety of different parameters than rock (melting point, compressability, bulk modulus, electromagnetic effects...). In other words, there is a major qualitative and quantitative difference between rock and steel at the dimensional scales we're talking about here. But, this is all just hand-wavey science anyway... In any case, one could solve for the hydrostatic equilibrium of a 100% metallic planet, as AH1 has linked above, and calculate the minimum mass needed to form a sphere under self-gravitation. Nimur (talk) 04:35, 16 February 2010 (UTC)

The yield stress for steel ranges from ~250 MPa to ~1650 MPa depending on composition. Steel has a density of order 7.8 g/cm³. Using that and the higher yield stress, a solid steel cube could grow to about 650 km in side length before it deforms plastically. As for the largest cube, I think diamond would be in the running (yield stress 35 GPa) and should get you up to about 7000 km in side length.

Thanks! I'm impressed by the figure for diamond... never thought any solid material could grow that big! 86.134.30.55 (talk) 14:32, 16 February 2010 (UTC).

Don't we already know those heavenly bodies that don't become spheres? And don't we have an idea of the smallest heavenly bodies that are spherical, and that are likely to have become that way under the stresses of their own gravitational forces? Bus stop (talk) 15:25, 16 February 2010 (UTC)

Yes, but the OP asked specifically about a steel cube. We are partly arguing about (and avoiding actually calculating, because that would be too much like hard work) how much a steel cube would differ from comparable lumps of rock about which, as you say, we have observational as well as theoretical evidence. 87.81.230.195 (talk) 17:48, 16 February 2010 (UTC)

Effect of temperature change on skiing?

I'm watching the Olympic men's downhill right now, and the television commentators observed that there was a 5°C temperature difference from the top of the ski hill to the bottom — from 28°F to 36°F. What effect, if any, does this have on the conditions that the skier would notice? Nyttend (talk) 01:08, 16 February 2010 (UTC)

Just for the record, the recent warm weather is caused by an El Nino and PNA pattern, and Canada is at a lack of snow while the US gets most of the snowstorms.[1] As for the ski hill, I'm guessing that there would be a difference in snow conditions in powder vs. packing. ~AH1^(TCU) 01:38, 16 February 2010 (UTC)

The article doesn't help me very much — I understand that powder is better from the skier's point of view, but is it enough that he'd notice it while going down the slope? However, I'm well aware of the weather at large; I'm in western Ohio, and I spent most of last week shovelling :-( Nyttend (talk) 02:50, 16 February 2010 (UTC)

The skier likely wont notice a difference in the type of snow encountered (barring any ice that forms on the surface), as race courses are heavily groomed for a consistent surface. That said, the type of wax applied to the ski depends entirely on the snow temperature, and proper wax application is key to trimming those all important tenths of seconds off of times. Wired did a little write up that introduces the subject fairly well -here IMO, the most interesting thing is getting the layering of waxes just right so that the outer layer for colder snow is worn away by the time the skier gets to the warmer part of the course. 161.222.160.8 (talk) 05:10, 16 February 2010 (UTC)

Powder snow may be great for snowboarding, but for downhill skiers it puts the brakes on damn quick! A downhill ski course must be mainly ice for the skiers to get any sort of speed. Given that, temperatures above freezing would create a film of water above the ice and make things much quicker - and possibly dangerous. For the later skiers, prolonged temperatures above freezing combined with the pressure of the wafer-thin ski blades would mean the piste would rapidly turn to mush, and that's no good for speed skiing at all. --TammyMoet (talk) 12:35, 16 February 2010 (UTC)

Skiing on ice is horrible - you can't dig the edges of your skis in, which makes it hard to maintain control when turning. --Tango (talk) 13:53, 16 February 2010 (UTC)

For optimal traction and glide, Ski_wax is applied to the underside of skis. Which type of ski wax is applied is highly dependent on temperature. A single surprisingly bad performance by an athlete skier is often explained (rightly or not) by him or her having had the wrong type of ski wax. Amateur skiers will also be familiar with this problem, sometimes the snow stick to your skis because of the wrong wax. So yeah, the temperature could have a very big impact. EverGreg (talk) 13:05, 16 February 2010 (UTC)

The Planets

Why are the planets in the solar system so different in composition? Wouldnt the solar dust they were made of have been mixed up, so they should be made of similar material? 78.146.222.3 (talk) 01:44, 16 February 2010 (UTC)

One would hope that Formation_of_the_solar_system#Formation_of_planets would have the answers you need. Vimescarrot (talk) 02:25, 16 February 2010 (UTC)

Actually this is fairly similar to question which I've heard is one of the current difficulties in the theory of planetary formation. This is why the elements in the earth are often found in clumps. Like metal ores are generally found in big lumps of one type. No reason has been found yet why it isn't all arbitrarily mixed together. I wouldn't be at all surprised if there was at least some website out there claiming that just because we don't have a theory, must mean god did it. Vespine (talk) 04:10, 16 February 2010 (UTC)

...that seems incorrect. Ore Genesis —Preceding unsigned comment added by 24.137.114.204 (talk) 04:23, 16 February 2010 (UTC)

That's extremely interesting! I only just heard that recently and I thought it was a fairly reliable source, maybe it's some related problem that I just misunderstood. I'll have to see if I can find where it was. Vespine (talk) 04:41, 16 February 2010 (UTC)

The short answer is that different elements and compounds are retained by planets of different temperatures and masses. The Earth, for example, is to small to hold on to hydrogen, so the only hydrogen we have is locked up in compounds (eg. water). Jupiter is plenty big enough to hold on to hydrogen, so its atmosphere is about 70% free hydrogen. --Tango (talk) 14:05, 16 February 2010 (UTC)

Whereas Uranus is mostly filled with gases of various sorts. —Preceding unsigned comment added by 79.76.229.198 (talk) 00:41, 17 February 2010 (UTC)

LOL 146.74.230.82 (talk) 00:59, 17 February 2010 (UTC)

See Atmosphere of Uranus. At the core, Uranus and Neptune are thought to contain a layer of diamond[2]. ~AH1^(TCU) 03:11, 17 February 2010 (UTC)

So if we could get close enough to Uranus, could we detect ammonia and methane expulsions? What about H2S? Is there any of that gas inside Uranus? —Preceding unsigned comment added by 79.76.229.198 (talk) 13:58, 17 February 2010 (UTC)

If Titan do not heat to earthlike temperatures

If Titan do not heat to earthlike temperatures and stay below 50 C would Titan keep some atmosphere or at least 3/4 of it would be gone. This forum agrees with us and even said if Titan gets to Earthlike atmoshpere it would just be gray like our moon, I wonder if Titan only gets to -60 C, then probably the atmoshpere would be thin like Mars?--69.229.36.56 (talk) 01:47, 16 February 2010 (UTC)

I think the question is, if Titan's atmosphere is heated to Earth-like temperatures (possibly due to the expansion of the sun into a red giant), would its atmosphere evaporate from the heat and get thinner? ~AH1^(TCU) 02:35, 17 February 2010 (UTC)

Hydrogen

I have three questions to ask you:

1. Are there any commercial power stations that produce electricity by burning hydrogen?

2. Are there any motorbikes, buses, trucks, trains, boats, ships, submarines, or airplanes, etc, that use hydrogen as a fuel?

3. Are there any cooking appliances, heaters, or water heaters, etc, that use hydrogen as a fuel?

Bowei Huang 2 (talk) 04:13, 16 February 2010 (UTC)

The article Hydrogen vehicle has a few answers your second question. But mostly experimental stuff. APL (talk) 04:16, 16 February 2010 (UTC)

BMW has sold an extremely limited number of BMW Hydrogen 7 vehicles. It would be a stretch to call them "commercially available." I'm not aware of any (commercial) power plants that use hydrogen combustion for electric production. A few spacecraft do use hydrogen as a fuel. The big orange part of the Space Shuttle (rather, the "STS", to use the terminology correctly), is mostly a large hydrogen tank. Nimur (talk) 04:24, 16 February 2010 (UTC)

List of fuel cell vehicles Hydrogen fuel Hydrogen economy. BP had part of a power plant running on hydrogen but they pulled the plug. Italy has the 1st hydrogen power plant due to come online this year. strips hydrogen from methane. question 3, not sure. There is no readily available source of hydrogen yet, so most of those kind of things run on natural gas or electricity. I can't imagine they contribute enough to the problem to be considered a priority for conversion. Vespine (talk) 04:31, 16 February 2010 (UTC)

(ec)Was the BP plant really burning hydrogen for energy, or was it reprocessing it as part of an enhanced hydrocarbon recovery/refinery project? I see some mention of directly using the hydrogen stream, but given that BP is an oil company, I'd believe it more if they were investing in other uses for hydrogen - both in cracking and desulfuring. Nimur (talk) 04:41, 16 February 2010 (UTC)

(edit conflict)Hydrogen's potential as a fuel is better realized in its use in a device known as a fuel cell rather than in open combustion, such as in a standard internal combustion engine. Hydrogen has a rather low combustion potential; as actually burning it releases much less energy per gram than does burning most hydrocarbons, and the fact that it is a very light weight gas makes its use in open-combustion applications, like a standard car engine, quite impractical.

The hydrogen fuel cell, however, is hardly new technology; the basic design concept had been demonstrated in the 1800's and has been in use commercially since the 1950's; hydrogen fuel cells powered all of the electronics on the Apollo missions, and continue to be used by NASA for all of their electricity generation on all of their Space Shuttle missions. Hydrogen fuel cells are perfectly fine ways to power just about anything, you can run a fully electric car on one, producing only water vapor as a by product, and they don't burn anything, so there is no combustion. They operate like any battery, but with hydrogen rather than a metal as the cathode. Electric cars powered by fuel cells have been made which operate at modern highway speeds, and which can run at distances comperable to the distances a gasoline or diesel powered car can run on a full tank. See this C-net article about a fuel cell vehicle developed by Honda, which has a top speed of 100 mph and can run 270 miles on a tank of hydrogen. Indeed, such technology to do so has been around for years. The biggest issue is not in the way the car runs. A fuel cell car isn't the problem in converting cars to fuel cells, its hydrogen delivery infrastructure. An efficient and safe means of a) producing enough hydrogen to power a national fleet of fuel-cell cars and b) distributing the hydrogen to people so they can run their cars on it are the two main reasons why hydrogen has not taken off.

There are home generators which can make hydrogen for you using residential natural gas or just plain water and solar power; so hypothetically one possible solution is to allow everyone to make their own hydrogen at home rather than get it at fueling stations, see this description of both water and natural gas based systems, availible from Honda. --Jayron32 04:38, 16 February 2010 (UTC)

Regarding commercial power stations, hydrogen gas doesn't occur naturally, so you'd be better off using whatever you where going to use to make the hydrogen. It's useful in cars and such because it can still produce power relatively efficiently at a small scale, and driving with your car plugged in isn't an option. — DanielLC 05:34, 17 February 2010 (UTC)

That's a really key point: hydrogen is useful as an energy storage/transport medium, but not as a primary fuel itself. It's easy to make on large scale using some other energy source and then use to power other things elsewhere that are far from primary sources or somehow else can't use the primary source conveniently. But "generate hydrogen then use it" has an energetic cost, so you're better off not bothering with this intermediate form unless there is a reason. DMacks (talk) 05:43, 17 February 2010 (UTC)

I shouldn't have asked "by burning hydrogen". I should have asked if there were commercial power stations that use hydrogen to produce electricity.

Are there any commercial power stations that use hydrogen to produce electricity?

An Unknown Person (talk) 03:55, 18 February 2010 (UTC)

Solar power plants indirectly use the fusion of hydrogen into helium in the sun to produce electricity. Gandalf61 (talk) 15:57, 19 February 2010 (UTC)

Ground State Energy

What would be the potential real-world application(s) of knowing the ground state energy of one or more molecules? Truthforitsownsake (talk) 05:13, 16 February 2010 (UTC)

Knowing the relationship between ground state energy and exicited energy states has lots of applications. Exciting the nuclei of atoms to an excited state and alowing them to relax to the ground state is a fundemental part of nuclear magnetic resonance and its medical analogue, magnetic resonance imaging. Understanding concepts like Phosphorescence and Fluorescence requires understanding how energy states work. If you don't know what the concept of a ground state is, the entire quantum model of the atom will not be understandable, and not knowing how atoms work means you won't know how to effectively analyze them and use them. The entire field of analytical chemistry basically requires understanding how electrons and other parts of the atom behave as they are excited and allowed to relax to the ground state. Also, you can't pull some fact out of an entire discipline like this and say "how does this have a real world application". Take a holistic view; understanding Chemistry is useful; and this is a core concept to understanding chemistry. --Jayron32 05:29, 16 February 2010 (UTC)

It seems like your answer addressed the issue of knowing what the term "ground state energy" means. The question was in relation to knowing the actual specific energy value for a specific molecule. Truthforitsownsake (talk) 05:49, 16 February 2010 (UTC)

it allows you to predict the energy and therefore the wavelength of a photon emitted by an electron falling from an excited state to the ground state, and thus it allows you to figure out which elements are in certain light-emitting objects (e.g. stars) by observing the emitted light. I'm sre there are hundreds of other applications too. —Preceding unsigned comment added by 83.134.159.68 (talk) 07:25, 16 February 2010 (UTC)

The problem with that is that it would seem to require knowing the energy of one of or more of the excited states as well. Are there any you could think of using only the ground state energy? For example, is it possible to progress from the ground state energy of several molecules to a useful thermodynamic or kinetic property that could be used to predict the outcome of a reaction? I appreciate very much all the help being volunteered. Truthforitsownsake (talk) 16:31, 16 February 2010 (UTC)

KOH + CO2 → KHCO3

How much CO2 (in lbs or cu. ft.) will a gallon of reagent KOH convert to KHCO3 at STP and 100 deg. Celsius at standard pressure? (BTW - this is not a homework question but a question about how much KOH is needed to convert CO2 from IC engine exhaust to KHCO3. Also this is not a trick question since KOH is a solid or liquid and CO2 is a gas.) 71.100.8.16 (talk) 06:36, 16 February 2010 (UTC)

First, take a look at stoichiometry, which explains the mathematics of conserving mass in chemistry reactions. As far as I know, this reaction will not occur at standard temperature and pressure. We have a brief mention at Potassium_carbonate#Production and potassium bicarbonate, which make reference to electrolysis (generating K+ ions) as a necessary precursor step. Maybe an expert chemist can fill in the details. Nimur (talk) 14:11, 16 February 2010 (UTC)

I suppose that in a few hours, days or weeks I could calculate the output from an IC engine according to RPM x number of cylinder x cylinder bore and stroke, etc. and then how many lbs or gallons of KOH I would need to convert each cubic foot of CO2 to KHCO3 and at what temperature and pressure if I just knew how many lbs or grams of KOH I would need to convert just one cubic foot of CO2 to KHCO3. I was hoping this might have already been calculated somewhere and posted on the internet. 71.100.8.16 (talk) 14:37, 16 February 2010 (UTC)

Two points: First, KOH is a solid, so you need to know either the mass of KOH or quantity in solution (e.g. molarity). Second, you probably shouldn't be mixing US standard measures or Imperial with SI (you have gallons and 100 °C in your problem above). -- Flyguy649 ^talk 14:43, 16 February 2010 (UTC)

The issues you mention are also matters of conversion to the correct units, which should likewise be available somewhere on the Internet. So far I have only found this:

  1.  CO2 + H2O --> H2CO3
  2. H2CO3 + 2 NaOH (or KOH) --> Na2CO3 (or K2CO3) + 2 H2O + Energy
  3. Na2CO3 (or K2CO3) + Ca(OH)2 --> CaCO3 + 2 NaOH (or KOH) 

71.100.8.16 (talk) 16:00, 16 February 2010 (UTC)

Good, now you have the balanaced reactions for getting what you want. These reactions are in terms of molecules ("1 CO2 molecule + 1 H2O molecule gives 1 H2CO3 molecule", etc.), so you can use the molecular weight of each compound to convert those molecule ratios to mass ratios. You can check our article about each chemical to find these conversion factors. You could even do that for the theoretical reaction you proposed in the initial question. The only other ingredient in your later equations is water, and you already heard you need a lot of water just to dissolve and mix everything. DMacks (talk) 17:43, 16 February 2010 (UTC)

I'll assume that you want to use a temperature of 100 C, or 373.15 K, even though STP (Standard Temperature and Pressure) usually means 0 C or 273.15 K. First, lets assume we have a 1 molar solution of KOH. With a molar mass of 56.1 g/mol, that works out to be 56.1 g of KOH (1 mole) in 1 L of water. This means that the solution can theoretically absorb 1 mole of CO2, which weighs 44.1 g. Using the gas equation PV = nRT, we can solve for V using P = 0.986 atm (STP), n = 1 mole, T = 373.15 K and R = 0.08205746 atm*L/mol*K we get a volume of 31 L. This is all assuming that CO2 at these conditions can be treated as an ideal gas, but this should be a good estimate.

24.150.18.30 (talk) 02:26, 18 February 2010 (UTC)

sterno in racing

why did they use sterno in racing wouldent it make more sense to just use ethanol rather than hundreds of cans of sterno —Preceding unsigned comment added by 67.246.254.35 (talk) 08:49, 16 February 2010 (UTC)

Are you referring to the allegation the Michael Waltrip used Sterno during 2007 Daytona qualifying, as mentioned at Sterno#Use in racing? Three things come to mind - it's unlikely that the "bluish gel" was Sterno brand canned fuel, since Sterno is dyed pink; "hundreds of cans" would not have been used for that incident, since it was during qualifying, which is only a limited number of laps, and whatever the substance was could conceivably have been purchased in bulk, rather than cans. --LarryMac | Talk 13:50, 16 February 2010 (UTC)

WHY NOT JUST USE ETHANOL THOU? —Preceding unsigned comment added by Thekiller35789 (talk • contribs) 23:55, 16 February 2010 (UTC)

Possibly for timed release, or to avoid detection by inspectors looking for prohibited additives mixed directly into the fuel. --Smack (talk) 19:09, 17 February 2010 (UTC)

Wings and the human anatomy

I know this is impossible, but a human were to be born with feathered wings as pictured in typical angel pics, what kind of anatomy would he/she have to have? Meaning, will there be extra muscles, bones, etc? --Reticuli88 (talk) 13:51, 16 February 2010 (UTC)

Are the wings just ornamental or are they supposed to actually make one fly? The latter would require a massive anatomical overhaul in terms of more muscles, lighter bones, etc., if it were even going to be a little tiny bit possible. If they are just ornamental, then it just depends on the weight of them. --Mr.98 (talk) 14:07, 16 February 2010 (UTC)

Not ornamental. I just want someone to detail to me how it will not look like the typical angel pictures. --Reticuli88 (talk) 14:09, 16 February 2010 (UTC)

Angels are usually shown as having wings and arms. That means they have 6 limbs, which is a very different anatomy. If you replaced their arms with wings, it is much simpler. You can get an idea of how the arms and hands would need to change by looking at bats. The other major change in that the muscles in the chest would need to be much, much larger if you want them to be able to get off the ground. --Tango (talk) 14:12, 16 February 2010 (UTC)

(ec) We can't answer specific details about your hypothetical situation. You've already stepped outside the bounds of reality by suggesting the impossible - so requesting scientific analysis at this point is futile. There is no correct answer to this kind of "what-if" question. However, if you want to consider something scientific, you might notice that the closest winged relatives to humans are bats. Because they are mammals, like humans, they do not have feathers (their skin cells have adapted to form hair, not feathers). The wings are made of a skin membrane stretched across specially-adapted finger bones. Nimur (talk) 14:15, 16 February 2010 (UTC)

In the case of wing muscles they might look more muscular rather than larger since insect wing muscles are the most powerful muscles known... (correct me if I'm wrong.) 71.100.8.16 (talk) 14:16, 16 February 2010 (UTC)

The square-cube law means insects can fly extremely easily because they are so small, so using them as an example isn't useful. "More muscular" and "larger" are the same thing, anyway - muscles get stronger by getting bigger. --Tango (talk) 14:28, 16 February 2010 (UTC)

That is for true flight. Gliding would be much more feasible with only minor changes. In fact, they have clothing that will let you do that. Googlemeister (talk) 14:29, 16 February 2010 (UTC)

Obligatory link to Wingsuit flying. --Mr.98 (talk) 14:40, 16 February 2010 (UTC)

Gliding in a wingsuit is lot like plummeting.APL (talk) 15:35, 16 February 2010 (UTC)

errr... I'll point out that gliding usually preferences a non-feathered wing (feathers give control over lift, but introduce drag), but a human figure with huge bat-like wings starts to look decidedly non-angelic. --Ludwigs2 16:29, 16 February 2010 (UTC)

And that calls for the obligatory link to Childhood's End... alteripse (talk) 21:09, 16 February 2010 (UTC)

Also, angels are usually depicted with wingspans shorter than their armspans! Unless they can beat them faster than a hummingbird, that's not nearly long enough. Hangliders typically have wingspans of 30ft or more, and human-powered aircraft like the Gossamer Condor of nearly 100ft. It's difficult to imagine how that could fold comfortably onto the back of a humanoid when not in flight. APL (talk) 15:35, 16 February 2010 (UTC)

I remember reading that they would requie a huge musculartor to fly - so tthey wouldnt look like they do in paintings. 89.242.101.230 (talk) 20:41, 16 February 2010 (UTC)

Genetically - this is an essentially impossible mutation. It's conceivable that someone could be born with 6 limbs (this has probably happened more than once in human history) - but it's really hard to imagine how feathers could be there. The gene(s) for feathers came about as dinosaurs evolved into birds - but the mammal line had already branched off by then - so there isn't really a way for such a complex set of genes to appear in humans all in one go. Feathers are a modification of scales - and humans aren't scaley. So this would require truly massive amounts of incredibly lucky mutation. It's essentially impossible. SteveBaker (talk) 20:57, 16 February 2010 (UTC)

If we go down the bat-like wings route, rather than the angel-like wings route, then it is a little more feasible (bats are quite closely related to humans). You swap some human genes for bat genes and see what happens. With current knowledge of genetics, I would expect it to require a significant amount of trial and error to get it even close. I expect the most difficult part would be turning human arms/hands into bat's wings while leaving the legs/feet unchanged - as I understand it, the same genes are used, in part, for both. You also need to do something about the muscles, but perhaps that could be done with some well placed hormones during gestation or shortly after birth. --Tango (talk) 03:12, 17 February 2010 (UTC)

There are four levels we need to think about. First, could you make something the size and weight of an adult human fly under his/her own power? Theoretically, the answer is yes - there are birds and pterosaurs larger than humans who have flown under their own power. Second, could you make an animal with three sets of limbs? This is a hand-wavey theoretically "maybe" - I don't think it's completely and utterly impossible for there to be a second shoulder girdle at the bottom of the rib cage, for example. Third, could you make something the size of a human fly with wings as commonly depicted? No, not unless you seriously muck around with the mass involved. Of course, since an infinite number of angels can dance on the head of a pin without crushing it, perhaps this isn't really a problem! Finally, could you have wings in the place commonly depicted? No, there's just no extra space there for anything; your back muscles are a very complicated set of muscles that slide over and under one another; there's no room to just go adding extra bones and stuff there. And then you get into feathers... Matt Deres (talk) 22:05, 16 February 2010 (UTC)

Bear in mind that many people think angels are spiritual beings, and as such are "transcendent and therefore metaphysical" in nature (ie. incorporeal and therefore without mass). In other words, angels don't need large wings with even larger muscles to enable them to fly. Astronaut (talk) 01:08, 17 February 2010 (UTC)

There are flying birds the size of humans, but they are far lighter than humans due to different bone composition, etc. --Tango (talk) 01:12, 17 February 2010 (UTC)

According to the article I linked to, Argentavis has been estimated to weigh between 60-110 kg. Close enough! Either way, it ain't gonna happen. Matt Deres (talk) 01:37, 17 February 2010 (UTC)

According to the Bible, angels have neither wings nor a ring around their head. Maybe they look like humans but only "fly" vertically upward. ~AH1^(TCU) 02:26, 17 February 2010 (UTC)

We aren't being asked about supernatural angels - and we're not being asked whether such a creature could fly - we're being asked whether someone could be born looking that way - and for all practical purposes, the answer is a very clear "No". SteveBaker (talk) 02:57, 17 February 2010 (UTC)

The OP said "not ornamental", which I interpret to mean they are supposed to be able to make the person fly. --Tango (talk) 03:12, 17 February 2010 (UTC)

Thanks everyone for their input. I was trying to imagine if a human being had 6 limbs, two of those being wings (feathered or not) how much would it not look human. I mean, would the back look twice as huge? Or the chest? Will it have to have longer legs or a longer neck? --Reticuli88 (talk) 16:15, 17 February 2010 (UTC)

So I imagine that this human might have to look something like this. --Reticuli88 (talk) 19:28, 17 February 2010 (UTC)

But that's just not possible given the way genetic change and developmental processes happen. If you have a strong stomach here are some photos of an actual six-limbed human. SteveBaker (talk) 02:51, 18 February 2010 (UTC)

Even assuming you could genetically engineer (on purpose - highly unlikely - or by accident - infinitesimally unlikely) a human with wings, you have lots of additional problems to overcome before you could actually fly. As Matt Deres mentions, Quetzalcoatlus was more or less that same weight as a human, but it required a wing-span of around 10 metres. I don't know about you, but wings that size would seriously interfere with my social life.

Large wings needed

We would likely need to revamp our metabolism and bone structure, to provide enough energy and tensile strength, while minimizing weight. Finally, we would need tendons, to lever the wings, and muscular physiology to power them, that are on a completely unhuman scale. I'm estimating here (you could probably do the math), but I would guess we would need pectoral muscles that were 10-20 times bigger than any human has. We would probably also need a tail to help steer, and would have to ditch our legs or develop some system to keep them horizontal during flight. In other words, generating wings is just the beginning: making them work is a whole other story. Rockpocket 03:44, 18 February 2010 (UTC)

Why would you assume we'd develop an extra set of lims? As others here have alluded to, hexapods came on land separately from four-limbed animals. This shows any transitions between the two are extremely, extremely unlikely. Imagine Reason (talk) 04:24, 18 February 2010 (UTC)

I'm not sure why the article that Steve linked to (and Steve) refer to the girl in those photos as a "six limbed human". She clearly has eight limbs. Four Legs, Two normal arms, And two underdeveloped, upside-down arms. APL (talk) 16:08, 18 February 2010 (UTC)

Thanks RP. What does tensile strength mean? --Reticuli88 (talk) 15:02, 18 February 2010 (UTC)

got it --Reticuli88 (talk) 15:45, 18 February 2010 (UTC)

Signal White Now II

This question - [[3]] - let me thinking. If this dye absorbs light in the ultraviolet spectrum and emits light in the blue spectrum, it would yield a better or worse result depending on the amount of UV hitting the teeth. So, in a room with indirect natural light that comes in through a glass, its effect would possibly not be noticeable. However, under a black light in a night club the teeth could look whiter or perhaps simply blue (depending on how yellow they were), right?--ProteanEd (talk) 16:47, 16 February 2010 (UTC)

Right, and under such lights, to my personal observations, teeth often do glow blue-white, just as do white clothes washed in detergents containing similar 'white-enhancing agents.' Note that although this particular product apparently claims to (and doubtless does) contain a newly formulated (or utilised) ingredient, toothpaste manufacturers have been using other such ingredients with similar properties for some time. 87.81.230.195 (talk) 17:29, 16 February 2010 (UTC)

Teeth are made of apatite which fluoresces without any conspiracy involved ;-) Cacycle (talk) 22:56, 17 February 2010 (UTC)

Ferris/Chelsea wheel?

While researching the invention of the Ferris wheel I remebered years ago a story about a dispute over who had the invention first. The story was that a gentleman named Chelsea had first set out to build what is now the modern Ferris wheel. His invention was called "The Chelsea Roundabout" Has anyone heard this story or is it just some folk tale?Nijia2010 (talk) 19:09, 16 February 2010 (UTC)

I couldn't find any reference to this story at all. However, it is known that after Ferris built his wheel for the 1893 World Fair in Chicago, many people copied the idea and he spent most of the rest of his life launching (and defending against) lawsuits. So it's very possible that other people claimed to have beaten him to the idea. It might help if you told us where you heard about this "Chelsea Roundabout". SteveBaker (talk) 02:54, 17 February 2010 (UTC)

Parts of brain responsible for street smartness and academic intelligence

Some indivdiuals, who are quite good academically are easily duped in real life. They lack what is called street smartness or tact . There are others with bad grades but are very clever in real life and go on to become businessman etc. There are a few who are strong in both areas. However, since one sees quite clear division of skills. One may conclude that different parts of brain are responsible for academic / real life intelligence. Could you please throw some light on that? —Preceding unsigned comment added by 131.220.46.25 (talk) 19:19, 16 February 2010 (UTC)

Actually, terms like "street smarts" and "common sense" are probably most often used by the less-educated to claim some mental advantage over the more-educated. Your claims are quite dubious. A tangentially related article is Staircase wit, about people who are witty but slow in coming up with the response. Supposedly this described Rousseau. Comet Tuttle (talk) 19:49, 16 February 2010 (UTC)

I don't think there is any scientific evidence for this phenomenon - and without that, we're not going to have any explanations. I suspect it's not true. SteveBaker (talk) 20:50, 16 February 2010 (UTC)

In any case, I'm not sure how you would try to measure it. Compare someone's SAT scores with the number of times they've been mugged? "Street smarts" and "common sense" are necessarily fuzzy terms.

That being said, I would hazard to guess that in the U.S., anyway, whatever we call "street smarts" (which is not the same thing as "common sense") does probably correlate with the economic conditions of one's upbringing, and so, probably, does advanced academic achievement. In my anecdotal experience, people who are very far along academically (e.g. Ph.D.s) at very prestigious East Coast institutions (e.g. Ivy League) are quite disproportionately from very wealthy personal backgrounds, and as a result have been, again from my experience, quite sheltered compared to the rest of the population (or, indeed, my own upbringing). As a result I have witnessed them be what I considered to be quite naive about the "facts of life" for the rest of the world out there, even if they are quite good in their own academic field of study. Again, totally anecdotal, not data. And I don't even know if my anecdotal examples are very representative. I also know a number of people who have achieved high academic status from remarkably low economic origins, even criminal backgrounds. None of it really tells us whether this is strong correlation, or just a stereotype. --Mr.98 (talk) 21:09, 16 February 2010 (UTC)

In more general terms, there's the question about what you mean by street smarts. Sure these people from wealthy and sheltered backgrounds may not do well in the mean streets of LA (or whatever). How will the average person from the mean streets of LA, even with their 'street smarts' do in a wealthy neighbourhood or when interacting with these wealthy people? For that matter, people from uneducated backgrounds are prone to being ripped off by banks, money lenders, dubious service providers and other such things, while academics are far from immune to this they do tend to less commonly fall for some of the common practices and pitfalls (and not just because they don't have to or they have advisors). Nil Einne (talk) 22:43, 16 February 2010 (UTC)

Additionally, if we fault the clueless academic for getting ripped off by the "I just need $5 to catch a bus" line, do we fault the uneducated for spending thousands of dollars (across their life) on lottery tickets? --Mr.98 (talk) 15:49, 17 February 2010 (UTC)

It's a naive, not an unanswerable or meaningless question. First, read our intelligence article on the different kinds of intelligence. Second, contemplate all the types that can go into "street smarts": usually a combination of being good at reading strangers' behaviors and intentions and familiarity with local customs, resources, and hazards. Third, contemplate the types of intelligence that make for "book smart": good grades usually means school study skills, comfort in a school environment, and being good at giving teachers what they want, perhaps with unusual reading background. These are somewhat overlapping skills: people-reading and knowledgeability about social demands of a specific environment. Obviously there are other dimensions to both types of success: numeracy, risk taking, perseverance, ability to learn from mistakes, use of contacts, luck, charm, attractiveness, etc. I would not be so quick to deprecate the level of intelligence needed for success in the two areas. alteripse (talk) 21:41, 16 February 2010 (UTC)

I think there's a reasonably good case for distinctions between spatial/mathematical intelligence, verbal intelligence, and social intelligence (ability to interact productively with other people), at the least. Street smarts, though, are largely a product of harsh experience rather than intelligence per se, I would guess. Looie496 (talk) 22:03, 16 February 2010 (UTC)

My take on this would be that people who are used to a professional culture are inexperienced when they find themselves in a machismo culture. For example they may expect people to be reasonably honest or altruistic. Vice versa as well, but because professionalim is 'nice' then people from the dark side are not so harmed by it. People from a professional culture are also at a disadvantage by being ethically constrained from using the manipulation or coercion that the machismos use. 89.242.101.230 (talk) 23:51, 16 February 2010 (UTC)

To the original poster: you might find the theory of multiple intelligences introduced by Howard Gardner in the 1980s of interest. It proposes different types of intelligence (usually eight), although none of them can be characterized as "street smarts". However, the "interpersonal" type is perhaps the closest to what you are talking about.--Eriastrum (talk) 00:00, 17 February 2010 (UTC)

False dichotomy. The subprime loan applicants are one example. People can be smart or stupid in academic and non-academic areas. It all depends on what you're talking about. Imagine Reason (talk) 00:03, 17 February 2010 (UTC)

Everybody has to paddle their own canoe. When one door closes another door opens. Bus stop (talk) 01:09, 17 February 2010 (UTC)

The closest article I could find on Wikipedia to "street smarts" was youth subculture. ~AH1^(TCU) 02:18, 17 February 2010 (UTC)

Concur with Alteripse: I think it's a reasonable observation, although it is not a rule by any means. The problem is that both perceived "academic intelligence" and perceived "street intelligence" are complex characteristics that include not only general "intelligence per se", which IQ tries to measure and which is a pretty problematic concept, but also various intellectual and social habits, acquired skills, experience and knowledge, as well as reaction speed (much more crucial in "street smartness"). Many of these things are such that you tend to specialize to varying degrees in each of them depending on your life history, and you are, naturally, weaker outside of your element. Others, such as reaction speed, probably have a genetic component which may influence what you choose to specialize in in the first place. --91.148.159.4 (talk) 04:16, 19 February 2010 (UTC)

This is just a stereotype put about by the media to flatter dummies. It also appeals to people with the tough minded personality type. 89.242.89.218 (talk) 14:27, 19 February 2010 (UTC)

So you think you're "smart" both academically and in real life, and the two are one and the same? I'm afraid this is a new stereotype put about by intellectuals and businessmen to flatter themselves. I'm an intellectual myself, but I don't buy it.--91.148.159.4 (talk) 14:32, 19 February 2010 (UTC)

Ganymede

Is the large blue part ocean or is it just iron mantle, since the tan-white part is the icy crust? I don't think Ganymede's surface ocean is as big as Europa's.--209.129.85.4 (talk) 21:43, 16 February 2010 (UTC)

Neither of them have a surface ocean, they are far too cold. Europa is believed to have a liquid ocean underneath the ice and Ganymede might too, but the description of that image (which concurs with Ganymede (moon)#Internal structure) describes the blue layer as "a deep layer of warm soft ice" ("warm" is presumably a relative term). --Tango (talk) 23:15, 16 February 2010 (UTC)

Fuel Consumption Problem - (How Much Extra Fuel Would I Use by Carrying More Fuel to Begin With?)

Let's say I have a car that weighs w kilograms and it is driving in a straight line at a constant speed along a perfectly flat road of zero gradient and zero camber. Let's assume we want to travel a total distance of d kilometres, and we start with s litres of fuel. Now, let's assume that we used u litres of fuel to make that journey. Next time we start with m litres more fuel than last time and make the same journey, in the same conditions, along the same road.

1. How much extra fuel, say e litres, would I have used by starting off carrying more fuel?
2. How far less, say l kilometres will the same u litres of fuel carry me given that I am starting off carrying more fuel?

To make things simple, assume that fuel consumption only depends on the weight of the car. Don't worry about the temperature of the fuel or of the tyres, etc. Add some assumptions if you like, and take some away if you like. I just want to know how much extra fuel I would use by carrying more fuel to begin with. I have a maths degree, and a strong theoretical grasp of differential equations, so don't worry about being too complicated. Thanks is advance. •• Fly by Night (talk) 22:13, 16 February 2010 (UTC)

P.S. I tried the maths reference desk and I got a single, unhelpful, reply. •• Fly by Night (talk) 22:14, 16 February 2010 (UTC)

The real question here is: How much does weight affect fuel efficiency for a typical car? Once you have that, the rest is algebra. This website says: "An extra 100 pounds in your vehicle could reduce your MPG by up to 2 percent. The reduction is based on the percentage of extra weight relative to the vehicle's weight and affects smaller vehicles more than larger ones." I'm not sure how reliable that is, but it will do for now. Petrol#Density says petrol ways about 6 lb per gallon. That means your MPG is going to reduce by about 0.12% per extra gallon of fuel. I suspect that is well within the margin of error of fuel efficiencies anyway, due to different driving styles, journey types, etc. --Tango (talk) 23:07, 16 February 2010 (UTC)

Thank you. I thought that some differential equations might have been needed, but the amount of wasted fuel is so small that I would probably waste more brain power solving the equations than I would on the extra petrol. Thanks again. •• Fly by Night (talk) 23:32, 16 February 2010 (UTC)

That single parameter will vary by type of vehicle. A truck which is already towing 25 tons will be largely unaffected by an extra 250 pounds of fuel. Meanwhile, a Prius (whose fuel efficiency is significantly improved by its extremely light weight may notice as much as a 10% fuel efficiency decrease when you add 250 pounds of fuel. Of course, a truck's fuel efficiency is already low - ~ 6.5 mpg, compared to a 45 mpg Prius. Nimur (talk) 23:12, 16 February 2010 (UTC)

What Prius has a 40 gallon fuel tank??? Googlemeister (talk) 13:53, 17 February 2010 (UTC)

The Prius HM - Hypothetical Model. The entire backseat was converted to a fuel tank. The connector hose goes out the window and connects to the main tank. Unfortunately, we forgot to account for the extra mass and aerodynamic effects of the tank, hose, and secondary fuel pump. Nimur (talk) 15:14, 17 February 2010 (UTC)

I have to wonder: does weight really change the fuel consumption rate in a car going at a constant speed on a flat road? The only forces that need to be overcome by burning fuel are drag and mechanical friction, neither of which are affected by weight. Weight only increases fuel consumption in start-stop traffic where a larger force must be exerted to the larger mass in order achieve the same acceleration. That is irrelevant here as the car is going at a constant speed. Planes, on the other hand, are much more sensitive to weight as additional weight requires a higher angle of attack to generate the required lift, increasing the drag it faces. --antilived^{T | C | G} 02:00, 17 February 2010 (UTC)

Wait... I'm pretty sure weight affects friction via the normal force. Weight is not an issue with a frictionless surface. John Riemann Soong (talk) 03:07, 17 February 2010 (UTC)

For a car it is the rolling resistance that is of interest more than any sliding friction. 58.147.58.28 (talk) 05:53, 17 February 2010 (UTC)

The problem is that it depends on how you drive. At a high constant speed on a level freeway, almost all of the energy goes into overcoming air resistance - the amount of power required to overcome air resistance goes up as the cube of the speed. Hence the weight hardly matters at all at freeway speeds. The amount of energy needed to go uphill or to accelerate depends largely on the weight and relatively little on everything else. At slow, constant speeds, the energy mostly goes into overcoming friction - some fraction of which depends on the weight of the payload and some fraction does not. This factor depends on the design and relative weight of the car itself. Consequently, we're not going to be able to come up with a definite formula. But at constant speed - the general answer is that the amount of weight in the car matters much less at high speed than it does at low speed because at high speed the energy consumption is dominated by drag and at low speed by friction. Because of the "cube of the speed" thing, you can get dramatically different fuel consumption driving into the wind versus with a tail wind because drag is determined largely by the speed relative to the air - not relative to the road. SteveBaker (talk) 02:33, 17 February 2010 (UTC)

Nice answer, thanks. But doesn't momentum need to be taken into account when considering wind resistance? If I throw a table tennis ball into the wind then it won't travel very far. It has very little momentum and the wind overcomes it very quickly. If I fill the same table tennis ball with lead and then throw it with exactly the same initial conditions it will travel much, much further. I will use more energy getting the heavier ball up to speed and so it will travel further. The same is true for a light car and a heavier car. Let's say the two cars are exactly the same but one has a bigger engine (i.e. more weight and more power). We get the cars up to the same speed on the same road in the same conditions and then cut the power and let them glide. The lighter car will use less fuel to get to the starting speed but will also stop sooner. The heavier car will use more fuel to get up to speed but will travel further. Plus, a lot of this momentum is built up at low speeds when friction really does matter. •• Fly by Night (talk) 18:37, 17 February 2010 (UTC)

P.S. The cube of the speed law needs some constants to make sense. A cube will grow faster than a square, that is true. But just because it grows faster it doesn't mean that it is larger. Consider x^3/1000 and x^2. We need x > 1000 for x^3/1000 > x^2. •• Fly by Night (talk) 18:47, 17 February 2010 (UTC)

Even for the specified conditions straight, perfectly level road and constant speed, rarely to be found on this planet, more weight means more friction in bearings and more work done on the tires. Granted, at highway speeds wind resistance is the main factor limiting fuel mileage, and adding more weight of fuel need not increase wind resistance. A higher load should mean more tire heating and less mileage. On practical roads, there generally is some hill climbing, and accelerating and decelerating due to traffic conditions, so the extra weight would decrease mileage (except on a hybrid with ideal regenerative breaking). Real cars must accelerate up to speed, and inability to merge onto an expressway due to undersized engine for the weight is dangerous. A lighter car allows a smaller and more efficient engine and transmission. Some information on weight versus fuel economy in real cars driven on real roads: [4], [5].Edison (talk) 21:35, 17 February 2010 (UTC)

This reminds me of similar considerations which lead to space rockets (nearly) always having three stages. If you objective was to go as far as possible on one filling of fuel, then you could tow a trailer full of fuel and ditch it when it when it was empty to save weight. 78.149.241.220 (talk) 16:20, 20 February 2010 (UTC)

Mars Colony

How much would it cost, in 2010 dollars with 2010 technology, to establish a self-sustainable colony of 50 men and 50 women on Mars? TheFutureAwaits (talk) 22:27, 16 February 2010 (UTC)

Well, it can't be done with 2010 technology. We don't currently have a spacecraft capable of taking people to Mars. Most of the cost is in developing the technology we need. How much that costs depends largely on how quickly you want to do it and what degree of safety you want. --Tango (talk) 22:55, 16 February 2010 (UTC)

Conceivably, you could try to run up a sum of all the necessary costs to build and launch the space mission; estimate going-rates for all the needed technology, etc; and generate a cost-estimate that way. I think that would probably be an alright way to do a cost-estimate, but it's very sensitive to the details of your mission plan. This is the way I would approach the cost-estimation problem - without presupposing any particular mission scheme or technology design. It would be a reasonable, albeit loose, claim, to state that such an endeavor would require the entire force of the current space administration in order to drive the enormous project and sub-projects needed to make that voyage possible. If political bickering was not an issue and you could throw today's entire space program budget at that particular task, it might still take five or ten years to ramp up the technology. So, noting that NASA's annual budget is ~ 17 billion US dollars, and the project may take 5 to 10 years, I would estimate that it might cost on the order of 100 to 200 billion dollars. Since "$100 billion" is a hard-to-conceptualize quantity of money, here's some other ways to think of it. It'd order about 10 billion cheese pizza deliveries, if you could find enough cheese pizza shops to deliver them. Or, it would be about as expensive as 500 deep-water oil rigs, or about as expensive as one year of sustaining a large overseas military campaign, or about as expensive as five to ten years worth of nuclear deterrence. These numbers aren't meant to be particularly accurate - but they highlight another mode of thinking about the budgets for such enormous projects. When NASA embarked on the Apollo Program, it was not like they could hold a bake-sale and raise some money, and then waltz down to the nearest retail store and pick up a Moon Spaceship once they had the right change. These kinds of enormous projects are better viewed in the context of nation-scale economic prioritization - not total dollar cost. Take a look, for example, at the Space Shuttle program budget. You can boil down the price to a succinct number (as NASA has done here) - but that number's pretty meaningless without context. (Phrased differently - could a billionaire with disposable income purchase a Space Shuttle for $1.7 billion dollars? If not, then is that really how much they cost? Nimur (talk) 23:22, 16 February 2010 (UTC)

5-10 years sounds like a big underestimate to me. 10 years might be enough for a small scale manned mission to Mars, but not to establish a large colony. I think 20-30 years is more realistic, even if the whole of NASA is devoted to it. --Tango (talk) 01:28, 17 February 2010 (UTC)

Well, when President Kennedy announced the plan to go to the moon in 1961, we had logged a total of 15 minutes of manned spaceflight - and had never even reached orbit. Yet, by devoting the entire national scientific establishment and a very significant chunk of our industrial base towards this simply-defined goal, we managed to make it happen. Mars missions bring a host of new technical challenges, but we have also advanced the state of the art very significantly since 1961. I think that we could do it in 5 to 10 years if we had the unfaltering, united will of the entire nation. Nimur (talk) 03:19, 17 February 2010 (UTC)

I suppose if we were willing for the first manned mission to Mars to have 100 people on board then it could be done, but I expect people would want to do at least one test flight with a handful of people first. That adds several years. (Remember, just getting to Mars takes nearly a year.) --Tango (talk) 14:09, 17 February 2010 (UTC)

Whatever estimate you come up with, you need to at least double it. It's always the way. 86.138.42.82 (talk) 01:03, 17 February 2010 (UTC)

How about this for a starting point: 100 people and their personal luggage have a mass of around 10 tonnes. All their food for a 4 year trip (18 months journey + something to get them started in their first martian year), all their water, and all their air would come to considerably more. Altogether a total payload of 100 tonnes or more. With launch costs of around $20,000 per kg that makes $2 billion just to get the payload into low earth orbit. You then have to develop the materials and tools to construct a martian habitat; and you have to develop, construct and fuel a spacecraft to get it all to Mars. And you have to get that lot into orbit as well. I wouldn't expect any change from Nimur's 100 - 200 billion dollars budget. Astronaut (talk) 01:50, 17 February 2010 (UTC)

The Constellation Program had a budget of $230B through 2025 and that was supposed to get us to a small manned lunar outpost. I would suspect the Mars mission proposed above would be closer to a trillion dollars. Dragons flight (talk) 02:03, 17 February 2010 (UTC)

Also, "self-sustaining" raises a lot of questions. It would be easier to make a "permanent" colony that requires regular rocket refills (which wouldn't need to be manned) than a truly "self-sustaining" one. --Mr.98 (talk) 02:31, 17 February 2010 (UTC)

Agree with above. People have tried making an isolated self sustaining habitat on earth, Biosphere 2 and it did not work out all that great. It only involved 8 people and a habitat area of 3.2 acres. Googlemeister (talk) 13:52, 17 February 2010 (UTC)

They tried to make an entirely biological system. That is useful for research purposes, but isn't required for an actual colony. For example, they had massive fluctuations in CO2 during each day due to photosynthesis dominating during the day and respiration at night. That is very difficult to solve with biology, but should be pretty easy with chemistry. There are plenty of ways of absorbing CO2 during the night and then releasing it during the day. --Tango (talk) 23:16, 17 February 2010 (UTC)

You could estimate it by guessing how many more times more expensive than landing people on the moon it would be. I'd say ten times more expensive. So the cost would be ten times more expensive than the Apollo cost in real terms. 89.240.100.129 (talk) 15:03, 17 February 2010 (UTC)

What kind of "Self sustaining" are we talking about? Is it acceptable to ship food from Earth? What about shipping supplies from Earth? What about shipping supplies from Earth, but they pay for them somehow by exporting martian goods? Or are you talking about a truly self sustaining colony where they can never get any help from Earth ever again?

That last might be very difficult. To do that, everything the martian colony depends on must be able to be manufactured locally. When a microchip fails, how will they replace it? When they start needing new spacesuits, how will they make them? If Mars had breathable air they could live a simple frontier life, but sadly, it doesn't. APL (talk) 15:57, 17 February 2010 (UTC)

(EC) I have to agree this "self-sustaining" bit is likely to be very difficult to achieve in the near term and probably even in the medium term. Most of the cost and time estimates above appear to be largely ignoring it yet it is surely one of the most difficult and costly things to achieve. Having food for 4 years sounds great, but is it really realistic to become self-sustaining in 4 years? Highly doubtful. We're still not even sure how to get water. Nil Einne (talk) 16:03, 17 February 2010 (UTC)

There's water ice underground in many places on Mars, that isn't a problem. --Tango (talk) 22:45, 17 February 2010 (UTC)

Could you spot them from orbit? Most of the martian ice we know about is near the poles. Not great locals for setting up a first colony. APL (talk) 15:58, 18 February 2010 (UTC)

You might be able to spot the ice from orbit, but if not you can just go somewhere that one of the landers we've already sent has found ice. --Tango (talk) 21:32, 18 February 2010 (UTC)

I think you're missing my point. Yes there is water. Finding enough of it and using it is another matter. We're talking about a self-sustaining colony of 100 people with 2010 dollars and 2010 tech. And people above were describing a 4 year time frame. Coming up with estimates when you haven't even solved one of the most basic problems seems pointless to me. It's all very well it being 'there' but you still have to find it, and find enough of it, and find a way to use it (which means sustainably release it etc) for your colony. If you're going to need to continually move your colony, or go further and further from your colony or whatever you further add to your difficulty particularly given the lack of resources and construction ability someone mentioned above. Perhaps it's just me, but when you say self-sustaning, I'm thinking we're discussing something which can barring catostrophic events survive thousands and thousands of years at a minimum without any involvement from earth. To put it a different way, once you start thinking self-sustaining with 2010 tech in 2010 dollars, all these things which seem minor and basic issues suddenly become a very big deal. (Of course some may question the basic premise, that a colony of 100 can ever meaningfully be self-sustaning.) Nil Einne (talk) 22:54, 19 February 2010 (UTC)

The details are not the same (far fewer than 100 people, not permanent, not self sustaining, and not necessarily relying on only 2010 technology) but estimates have varied widely. The first Bush administration called for a study and they came up with $400-$541 billion in 1989 dollars. Robert Zubrin and his Mars Direct plan say a mission is feasible for $55 billion (I think in 1990 dollars, possibly 1996 dollars when The Case for Mars was published). I think the real cost for a basic mission to mars would likely be somewhere in between - the 1989 estimate was way overboard and not a cost effective or sensible way to do things, Zubrin's estimate is optimistic and involves doing things on a shoe string budget that probably isn't practical (or is unacceptably risky). Based on even Zubrin's optimistic estimate, I don't think $100 to $200 billion is a realistic number for such a large colony (Zubrin's plan was for teams of 4). If I had to guess I'd say a 100 person colony would cost over a trillion dollars, possibly several trillion. TastyCakes (talk) 23:39, 17 February 2010 (UTC)

Have we replicated any ecosystem that can support vegetable and meat production here on earth using only plots with no soil? Have we created large artificial atmosphere anywhere? Imagine Reason (talk) 04:21, 18 February 2010 (UTC)

Well you don't really need to replicate an entire ecosystem to have a viable (or even mostly self-sufficient) colony. Nuclear submarines can stay underwater almost indefinitely as far as atmosphere goes, there is no reason to think similar technology wouldn't be possible on mars (see CO2 scrubber). And there's no reason I know of that you can't use martian soil as a plant medium. And even if farming is not possible, packing enough dehydrated food for years and years wouldn't be prohibitive. I think food and water are relatively small problems for such a mission, behind things like radiation, fuel, re-entries, debris/meteorites in transit and maybe even human personal issues after so long in a cramped space. TastyCakes (talk) 07:42, 18 February 2010 (UTC)

It is a big problem because near-lightspeed travel is not feasible for the foreseeable future. 67.243.7.245 (talk) 14:10, 19 February 2010 (UTC)

"packing enough dehydrated food for years and years " isn't self sustaining. Nil Einne (talk) 22:58, 19 February 2010 (UTC)

That reminds me of a project in the US where several people were put in a large hermetically sealed greenhouse-like building. It was on tv a few years ago. Unexpectedly, they had problems getting enough oxygen, even though they had been helped by the new concrete giving off oxygen. I think they were also short of food. 92.24.96.55 (talk) 21:18, 18 February 2010 (UTC)

That would be Biosphere 2, as mentioned above. --Tango (talk) 21:32, 18 February 2010 (UTC)

Or possibly Bio-Dome. TastyCakes (talk) 23:28, 18 February 2010 (UTC)

It would be a lot cheaper and perhaps more beneficial to mankind to spend money on developing some really clever robots. Then you could get them there with existing rocketry, and they would not need to come back. 92.24.96.55 (talk) 22:01, 18 February 2010 (UTC)

This somewhat glum editorial argues that maybe we shouldn't worry so much about bringing astronauts back either. TastyCakes (talk) 23:30, 18 February 2010 (UTC)

Again I think people are missing the point of the question which was a self-sustaining colony. Bringing them back isn't a big issue here. Nil Einne (talk) 22:55, 19 February 2010 (UTC)

God forbid a response to a ref desk question wander off topic... TastyCakes (talk) 20:48, 20 February 2010 (UTC)

February 17

Cabbage, salt and water... blue?

Hi all,

I'm making pickled cabbage. I shredded a bunch of red and savoy cabbage, sprinkled a few tablespoons of salt on it, and left it for 24 hours. Then I removed the cabbage. At the bottom of the bowl, there was a puddle of red liquid. I then brought the bowl to the sink and started pouring some water in it. To my surprise, the water turned bright blue!

Can anyone explain the chemical reaction that must have occurred?

Thanks! — Sam 76.24.222.22 (talk) 01:40, 17 February 2010 (UTC)

Red cabbage is a traditional pH indicator. [6] Dragons flight (talk) 01:43, 17 February 2010 (UTC)

The salt might have extracted the acidic component without extracting a basic component, maybe? John Riemann Soong (talk) 01:51, 17 February 2010 (UTC)

Very interesting. Any thoughts as to why it only appeared when I added water? (I was able to replicate this later.) I doubt my water is that basic! — Sam 76.24.222.22 (talk) 03:55, 17 February 2010 (UTC)

According to the "How to Make Red Cabbage pH Indicator" link on the Red Cabbage page, at pH 6 the solution is violet, and is blue at pH 8. I imagine at pH 7 it would be classified as "blue". Most tap water is around pH 7 (indeed, if it falls much outside that range, your water company will adjust the pH to avoid damage to the pipes and to keep the sanitizing power of the added chlorine). Now, why does the water *change* the pH? Most tap water isn't just H₂O, it also contains a number of buffering agents, especially if it comes from something like a limestone aquifer. The buffering capacity of the water probably overwhelmed the small amount of acid in the cabbage drippings, bringing the pH back to ~7 and turning the color blue. It's not that the tap water was very basic, it's just that it was less acidic than the juice. -- 174.21.247.23 (talk) 04:10, 17 February 2010 (UTC)

Orientation of the International Space Station

I've been watching live video of the STS-130 mission to the ISS online on NASA TV. At times (when they are not receiving video from the ISS) they display a graphic showing the ISS, from three views, as it orbits. From the relative motion of the Earth displayed below and what I assume are velocity and acceleration vectors displayed on the side view, it appears as if they are representing ISS orbiting with the Russian section leading and the shuttle, docked to PMA-2 (attached to Note 2, Harmony), trailing. This is the opposite orientation as described at International Space Station#Attitude (orientation) control. Exterior ISS video I saw yesterday of the PMA-3 attachment to Note 3 seemed to agree with the WP description. So, is the NASA graphic backwards, or do they occasionally reverse the orientation of the ISS, perhaps to help protect EVA crew from MMOD? 58.147.58.28 (talk) 01:53, 17 February 2010 (UTC)

It is hit and miss whether the orbital orientation graphic is displayed on NASA TV at any one time. I will try to find it in another source, but I don't know how easy that will be as it is not the sort of thing that typically makes it into the daily highlights videos. 58.147.58.28 (talk) 02:03, 17 February 2010 (UTC)

I haven't found another source for the graphic, but exterior ISS video of the EVA in progress showing Note 3, PMA-3, and cupola with the Earth seen moving below seems match the reversed orientation of the graphic. 58.147.58.28 (talk) 03:41, 17 February 2010 (UTC)

While the Shuttle is docked to ISS, the ISS attitude is yawed 180 degrees from normal such that the Russian Segment is in front and the Shuttle trailing, exactly as you describe. This is done to protect the Shuttle Thermal Protection System from micrometeroids and orbital debris. anonymous6494 08:49, 17 February 2010 (UTC)

Thanks. With the answer in hand I was able to search and find this reference which deals specifically with STS-130. I'd like to find one that mentions the practice in general, but I suppose that this one would be sufficient to expand International Space Station#Attitude (orientation) control. 58.147.58.28 (talk) 01:08, 18 February 2010 (UTC)

And I see that the orientation is back to normal as the shuttle undocks. (I missed the change which I assumed was done by the shuttle's RCS shortly before undocking). 58.147.58.28 (talk) 01:17, 20 February 2010 (UTC)

Correct! anonymous6494 05:07, 20 February 2010 (UTC)

Linear density

I computed the linear dord of quartz for a question earlier using wolfram alpha as ${\sqrt[{3}]{density}}$. The units for the result are ${{\sqrt[{3}]{g}} \over cm}$. I understand why it gave that result, but it doesn't make sense. Shouldn't it simply be $g \over cm$? What did I do wrong? Ariel. (talk) 02:45, 17 February 2010 (UTC)

The cube root of density is the cube root of (g/cm) not the (cube root of grams)/cm. Plus "dord" isn't a real word - as you'd know if you'd followed the link you kindly left us! SteveBaker (talk) 03:02, 17 February 2010 (UTC)

I know dord isn't a real word. It was a joke. You and Jayron below you said exactly the opposite things about the units. Ariel. (talk) 03:14, 17 February 2010 (UTC)

(edit conflict)Density is grams per cubic centimeter, or g/cm³. Taking the cube root of that returns g^1/3/cm or as you note above, the cube root of grams over centimeters. --Jayron32 03:05, 17 February 2010 (UTC)

If you take the cube root of g/cm³ you get g^1/3/cm, and yet linear density is g/cm - so what gives? Ariel. (talk) 03:14, 17 February 2010 (UTC)

That's because linear density is defined as mass per length, NOT as the cube root of density. So, you are starting from the wrong premise. Linear density is NOT the cube root of density; its just grams per centimeter. Wouldn't it be nice if there were some sort of free information resource on the web where you could look this stuff up? --Jayron32 03:25, 17 February 2010 (UTC)

OK, so in that case, if I calculate: I have matter with a linear density of 2 g/cm, by 4 g/cm by 1 g/cm the density is then 8 g³/cm³. So then why is density defined as g/cm³? And I did look stuff up, I read Dimensional analysis and Quantity calculus, and density and Linear density, and none of them explained why the units don't work. Ariel. (talk) 03:41, 17 February 2010 (UTC)

Linear density is not defined for material in general, but for a structure in particular. To determine the linear density of your quartz bar you need to know its cross sectional area. The linear density is then the density divided multiplied by the area, not the cube root of the density.58.147.58.28 (talk) 03:48, 17 February 2010 (UTC)

(edit conflict) Linear density is sort of a specialized unit; you can't cube it and get actual density. To get denisty from linear density, you don't multiply the linear density in three dimensions, you divide linear density (g/cm) by the cross-sectional area (cm²) and then you'll get the density. The reason for this is that the linear density of a substance is a measure of all of its mass divided by its length in one dimension. If you want volume density, you need to include the other two dimensions in terms of length, but you don't need to count the mass again, since that number is already included in the linear density. So linear density divided by cross-sectional area will give you volume density (i.e standard density). --Jayron32 03:54, 17 February 2010 (UTC)

If your quartz bar had a cross section of 1 cm x 1 cm, its linear density would be 2.634 g/cm. If it had a cross section of 2 cm x 2 cm, its linear density would be 10.536 g/cm. — Sam 76.24.222.22 (talk) 04:00, 17 February 2010 (UTC)

Thank you all. I understand it now. For some reason I thought linear density is a measure of "number of units of mass" per length, i.e. that it's the same for all shapes of objects, just like density is the same for all shapes. Clearly my math in this question was wrong, and I will redo it. Ariel. (talk) 04:10, 17 February 2010 (UTC)

Yeah. Density is a intensive property because it is a property of the material itself irrespective of the amount of material. Linear density is NOT an intensive property, except in limited applications. Linear density is intensive with respect to length ONLY, and only if cross-sectional area is kept constant. If you alter the crosssectional area, you change the linear density of the material. It generally has to do with the applications of linear density. You only usually use it in situations where you are dealing with a material which you work with in relatively uniform, long amounts of it, like say yarn or railroad rails or 2x4's. You would, for example, be interested in the linear density of a particular type of cotton thread, but two different types of cotton thread would have different linear densities, even if the cotton fiber they were both composed of has the same volume density. --Jayron32 04:31, 17 February 2010 (UTC)

Medical devices, WWII-era occupied Poland

The device in this archival photo was used in the Lodz ghetto, ca. 1940–1944. My questions: what is it, and was it used for diagnosis or for treatment? -- Deborahjay (talk) 09:08, 17 February 2010 (UTC)

And this one as well: same questions as above. -- Deborahjay (talk) 10:24, 17 February 2010 (UTC)

Guesses: First may be a medical diathermy machine. Second may be radiation therapy, or maybe just diagnostic x ray. The second setting is clearly institutional like a hosp x ray dept. The first setting may be a home doctors office. alteripse (talk) 11:12, 17 February 2010 (UTC)

Image one: From the position of the doc's hand and the direction of her gaze, I would say she is draining his left pleural cavity with a chest tube.

Image two: Certainly looks like a glass X-ray tube inside the enclose. I would think that under war time conditions of desperately severe shortages, all x-ray therapy would have been discontinued. It had very low success rates and so priority would have been given to diagnostic uses. Also, the woman has her hand on the x-ray collimator which is used to produce sharper x-ray images. --Aspro (talk) 18:18, 21 February 2010 (UTC)

I'm on a barge travelling across Neptune, towed by a cable connected to the moon Psamathe...

... how fast would I be moving, if my moon-towed barge was skimming the uppermost clouds?

Thanks Adambrowne666 (talk) 11:15, 17 February 2010 (UTC)

Since the moon takes 9074.30 days to orbit neptune, your barge circles neptune once every 9074.30 days. Neptune has a circumference of 155600 km. So you are going 155600 km per 9074.30 days = 0.443952 miles per hour. Try this as well (click on the text of the result, then the orange link under it to get it in other units). Ariel. (talk) 11:38, 17 February 2010 (UTC)

wow - so that's what you plugged into wolfram alpha, and it understood what you wanted? Cool. Adambrowne666 (talk) 20:32, 17 February 2010 (UTC)

155600km / 9074.30days = 0.4440 miles per hour. Don't forget your significant digits. Dauto (talk) 14:25, 17 February 2010 (UTC)

As a comparison, a sloth will be cruising by you at 3x your speed. Googlemeister (talk) 17:24, 17 February 2010 (UTC)

Thanks, everyone. Of course, the Neptunian sloth is a little faster, so would be cruising by at almost 4X my speed. Adambrowne666 (talk) 20:32, 17 February 2010 (UTC)

I think it would be more natural to measure speed relative to the clouds, not relative to stationary space. Neptune rotates once every 16 hours. Your boat anchored to the moon is nearly stationary in the external frame, so if you are at the equator the clouds would be whizzing by you at ~9500 km / hr. Not exactly a leisurely pace. Dragons flight (talk) 20:52, 17 February 2010 (UTC)

A extremely good point! Here it is in wolframalpha. Since Psamathe has a retrograde orbit the speeds add. Ariel. (talk) 22:42, 17 February 2010 (UTC)

Yes, of course! thanks both of you, didn't think of that either. Adambrowne666 (talk) 23:08, 17 February 2010 (UTC)

Besides just orbiting Neptune, wouldn't Psamathe be rotating relative to Neptune? If you fixed the cable to a point on Psamathe and the cable stretched all the way to you on Neptune then the cable would start to wrap around Psamathe as the base point rotated relative to your position. Eventually, as Psamathe continued to rotate, you would be pulled from the surface of Neptune, into space, and dragged back onto Psamathe. Think of your sledge being a fishing hook, the cable a length of fishing line, and Psamathe and it's rotation as a fishing reel being wound backwards. •• Fly by Night (talk) 22:38, 18 February 2010 (UTC)

Yoiu could anchor your point at the rotational axis of the moon and limit this action. Googlemeister (talk) 15:42, 19 February 2010 (UTC)

Yes, good point, Flybynight, and good idea, Googlemeister - cable's hooked to a rotating joint on the moon's axis; also, it's able to play in and out to make up for Psamathe moving closer and further away. Problems solved, now let's get down to making it! Adambrowne666 (talk) 22:44, 21 February 2010 (UTC)

Time Capsule

If I took my iPhone and buried it in a sealed vacuum capsule, how long would it remain useable (assuming the discovers could put in a new battery/power source). Which components would fail first? Would the OS start up? TheFutureAwaits (talk) 11:49, 17 February 2010 (UTC)

Indefinitely, I expect. You need to bury it deep enough that it won't suffer significant temperature changes, and you need to make sure the seal will last, but if you do that I can't think of anything that would damage it. --Tango (talk) 14:19, 17 February 2010 (UTC)

Does an iPhone contain any electrolytic capacitors? They eventually leak. Cuddlyable3 (talk) 14:34, 17 February 2010 (UTC)

Some types of battery can leak after a few years, however. 195.35.160.133 (talk) 14:56, 17 February 2010 (UTC) Martin.

You'd probably want to remove the batteries before you tried this. APL (talk) 15:38, 17 February 2010 (UTC)

How many years before the wireless technology has completely evolved and dropped backward-compatibility? I would estimate at least 25-30 years, but it's hard to say. Some analog mobile telephone technologies from the late 1980s are still supported by the transmitter towers and network providers; stepping even farther back, many land-line phone providers still provide support for rotary telephones or pulse dialing (probably using emulation with a software system). It seems plausible that 802.11 or "3G" GSM / WCDMA telephones might still be supported decades from now, even if they are no longer mainstream. Nimur (talk) 15:03, 17 February 2010 (UTC)

I wouldn't count on it. I had to replace my analog cell phone two years ago when the towers around here turned off their analog transmitters; the first-generation digital phone that replaced it lasted less than a year before the transmitters were turned off. --Carnildo (talk) 02:57, 18 February 2010 (UTC)

i would agree that any electrolytic capacitors are likely to become more leaky with time. Other components should not show significant ageing effects. However, some semiconductors may be compromised by the effects of nuclear radiation (gamma rays and cosmic rays). —Preceding unsigned comment added by 79.76.229.198 (talk) 15:36, 17 February 2010 (UTC)

After a while, tin whiskers may (or may not) start to form, these could cause shorts. The causes of tTin whiskers are not fully understood, so I'm not sure that a good estimate can be given.

This could theoretically be repaired by the benevolent future-people who also replaced the batteries, but it wouldn't be easy. APL (talk) 15:38, 17 February 2010 (UTC)

Dopants within semiconductors could migrate, rendering the chips nonfunctional, over a very extended time. You specified vacuum, which would prevent the oxidation of copper or brass I have seen in hundred year old telephones and telegraph instruments. But I have heard that vacuum can promote switch contacts welding together (that might apply more to those carrying high current, not so much a problem in a phone). It can also cause evaporation of films of lubricant which help switches and contacts operate. Vacuum would accelerate leakage of electrolytic capacitors. I would not expect typical rechargeable batteries to survive long storage under the conditions specified. Temperature variation could cause by the breaking of conductive paths and connections. Communications protocols will likely move on so that the signals used in the distant future would be incompatible with those used by a wireless phone of today. General Motors sold very expensive OnStar systems for car communication from 1996-2002 model years which became unusable after 2007 (this coming obsolescence was not mentioned at the times the expensive systems were being sold). The 1996-2002 system was analog, and was abandoned in favor of digital, with no retrofit of a new transceiver offered to keep the service going. From that example it is hard to see why operators of wireless systems would go to great lengths to make decades-old communications systems still operable. Planned obsolescence dictates that old software packages or hardware systems be "no longer supported" a few years later so the consumer has to shell out for a new one. Edison (talk) 17:21, 17 February 2010 (UTC)

Even with the cel-phone network gone or incompatible, the iPhone would still be a decent PDA. APL (talk) 18:41, 17 February 2010 (UTC)

One more angle, how long before Itunes is no longer backward compatible with version x (whatever version you bury it with), making it useless unless you posses the proper version of Itunes to perform intermediate updates? It won't be any fun to have to suffer along with the collection of music from right now... --144.191.148.3 (talk) 21:47, 17 February 2010 (UTC)

But this thing wouldn't be a practical/useful object after that much time. It would be a collectors item, a curiosity or a museum piece. In 20 years, we'll probably have a 1mm capsule that can be implanted behind your ear that runs on power generated from vibrations due to your heartbeat and not only comes pre-packaged with every piece of music known to mankind and can update with new music as it's recorded - but can compose new music in any desired style by itself. Why on earth would you care what music an antique iPhone could play? That's like asking why you can't get much rap music on 78 rpm shellac records. SteveBaker (talk) 02:35, 18 February 2010 (UTC)

Plastics are in fact not everlasting. There are many types of plastics and other materials on the circuitboard alone, not to mention the plastics in the casing. These will react with air or components in other plastics. I heard a museum curator remark that cellphones he were collecting would become brittle and disintegrate in just a matter of decades. The flash memory cards in the IPhone may also degrade over time, the technology actually relies on trapping electrons behind an insulating layer and I'm sure there's several ways that could be degraded. Add to that the problem with electrolytte capacitors mentioned above and I think we'll have to accept that many of us are going to outlive our gadgets, even if we store them in a cool dry place. EverGreg (talk) 09:39, 18 February 2010 (UTC)

Air in vaccum (okay I'm aware it's unlikely to be a perfect vacuum but you get the idea)? Nil Einne (talk) 22:51, 19 February 2010 (UTC)

Seal it in a 'dry nitrogen' atmosphere not a vacuum (a lot of military spares are packaged thus). It will also maintain a higher partial pressure to discourages the evaporation of the volatiles in plastic components.

A lead shield will help to mitigate natural radiation damage. Slow down chemical degeneration by cryogenic freezing -- then it might just last to the end of your warranty period. If you live in Poland, maybe not even that long [7].--Aspro (talk) 18:51, 21 February 2010 (UTC)

Average world temperature

What is the average world temperature? I want to compare one country with an average of 21–33 °C with world average, but can’t find any reliable sources of world average. Caspian Rehbinder (talk) 13:59, 17 February 2010 (UTC)

The first picture of the global warming article might have the answer you are looking for. Dauto (talk) 14:33, 17 February 2010 (UTC)

Actually, the article I linked uses temperature anomaly instead of actual temperature. The article Temperature record since 1880 quotes: "1901-2000 global mean of 13.9°C". Dauto (talk) 14:45, 17 February 2010 (UTC)

This is can be a very difficult number to generate[8], and most sources will tell you the average variance per month, or the "anomaly." Here is a page that throughly goes through all of this stuff[9]. The website is biased in POV, but all the data is good and kept up to date. In short, according to United States National Climatic Data Center, the mean world temperature for January is 12.60 °C. When you compare the country's average temperature to that of the global average, make sure you compare the same years or months.Mac Davis (talk) 07:11, 18 February 2010 (UTC)

According to satellite data, global average temperature anomalies jumped from +0.29C in December 2009 to +0.72C in January 2010[10]. ~AH1^(TCU) 00:54, 20 February 2010 (UTC)

Ion list

Where can I find a complete list of cations and anions?--Mikespedia (talk) 14:13, 17 February 2010 (UTC)

The short answer is, "You can't". An anion is any moderately stable negatively-charged atom or covalently-linked collection of atoms, and there is an infinite number of such. Among the anions, there are a finite number of monatomic ones (like chloride, Cl^-), but when you start allowing multiple atoms you get things like hypochlorite (ClO^-), acetate (CH₃COO^-), and dodecyl sulfate (C₁₂H₂₅SO₄^-). It gets complicated fast. Our article on ions lists a very few monatomic and small polyatomic ions, but you can't create an exhaustive list. TenOfAllTrades(talk) 14:50, 17 February 2010 (UTC)

In other words, because there are an infinite number of stable ways to combine atoms, there are thus an infinite number of ionized forms. A comprehensive list might contain all the relevant ions for a particular domain, but it will never really be complete. Nimur (talk) 14:58, 17 February 2010 (UTC)

Since this is relatively answered, I'll steer it away with some nit-picking. Is there really an "infinite" number of stable ways to combine atoms? there clearly aren't an infinite amount of different components to molecules (elements and their isotopes), and I'm skeptical that their is an infinite amount of ways you can arrange atoms into molecules to get "stable" arrangements. I will add to this the note that I don't know nearly as much about chemistry as I would like, but the use of the phrase "infinite arrangements" for a concrete thing such as an Ions made question mark appear. Please elaborate if you don't mind, thanks! Chris M. (talk) 17:26, 17 February 2010 (UTC)

Actually, there probably are an infinite number of ways, owing to substances such as polymers and network solids. For example, a diamond is essentially a single giant molecule of carbon atoms, and something like polyethylene contains molecules containing millions of atoms each. With carbon-based molecules alone, there is no finite limit to the size of the molecule, so there is no functional upper bound to the ways they can be combined. --Jayron32 18:38, 17 February 2010 (UTC)

Ah, I had a feeling my lack of knowledge of chemistry would show when asking that question. Thanks! Chris M. (talk) 21:14, 17 February 2010 (UTC)

Eating coffee beans

Say that I have a bag of coffee beans and wish to obtain the effects of caffeination, but I lack the means to grind and brew the beans to produce coffee. How much caffeination will I experience by simply eating the beans versus drinking brewed coffee? Do the digestive fluids "brew" the grounds in the stomach, or will they pass through the digestive system without yielding up their caffeine? 129.174.184.114 (talk) 16:16, 17 February 2010 (UTC)

Are you planning on swolling them whole? Dauto (talk) 16:40, 17 February 2010 (UTC)

Brewing doesn't create caffeine and there are a number of foods that include solid coffee beans (tiramisu, chocolate-covered expresso beans). But the results of civet cat consumption of raw beans is worth a mention: (Kopi Luwak). Rmhermen (talk) 18:34, 17 February 2010 (UTC)

Yes, I am aware that brewing doesn't create caffeine. My question is whether brewing in near-boiling water is necessary to release caffeine from the beans. In other words, if I eat coffee grounds (not intact beans), will the caffeine in the grounds leech out in my stomach or will the caffeine remain "locked" in the grounds? 129.174.184.114 (talk) 23:01, 17 February 2010 (UTC)

I'm pretty sure you will get the caffeine from the grounds, warm water may be slower than hot, but it's in you for much longer. If you don't crush (or chew) the bean you might not any from that though. Ariel. (talk) 07:41, 18 February 2010 (UTC)

Cosmological argument and the fine-tuned Universe

I have browsed some related articles and from what I understand, the biological evolution is inapplicable in explaining the formation of the Universe and its components, as well as the symbiosis of beauty and functionality of some of its components. The expanding Universe should expand in some surrounding space, that is it’s a closed system in terms of the 2nd law of thermodynamics, and yet demonstrates a quite strange decrease in entropy since its formation. So could the intricacy of the Universe, which features numerous self-sustained, sophisticated components in itself, serve as an evidence of initial intelligent design (if there is nothing from nothing)? From what I've read, the murky Planck epoch for example does not explain, how the four fundamental forces have formed. Neither does the science explain, where all micro essentials like elementary particles come from (instead that could be easily explained with FTU concept, assuming that the Big Bang stuff for example was meticulously concocted in a stock cube fashion and then launched off to run). The article on cosmological argument cites Kaku's critical example on gas molecules, but I think the bouncing molecules or any such stuff moving in a Brownian motion pattern will never form something complicated and useful, unless driven externally.

Another issue of the fined-tuned Universe that came to my mind is the Earth atmosphere. It’s one of the Universe components, which features multifunctionality (protection from asteroids and excessive solar radiation, etc.), combined with nearly unquestionable beauty. We admire it since Gagarin and most likely even an ancient or medieval man would notice its beauty on photo without even knowing what it is. That is, neither the Earth atmosphere has evolved to suit us, nor we evolved to, which means that most likely it was made to be such intentionally. Also, are stars the closed systems under thermodynamic principles? If so, the historical decrease of entropy in space would be striking. So how such long-lasting set of nesting dolls could form and evolve randomly, including the Universe itself? Brand[t] 19:20, 17 February 2010 (UTC)

I don't know what you've been reading, but there is no surrounding space around the universe, the universe is, by definition, everything. The universe is expanding, but it isn't expanding into anything. Also, the total entropy of the universe has increased since the big bang, not decreased. Beauty is an entirely human concept that we have evolved. Things aren't inherently beautiful, there has just been a reproductive advantage to us considering them beautiful. I think once you resolve these misconceptions of yours, you'll find your questions are moot. --Tango (talk) 19:42, 17 February 2010 (UTC)

See Metric expansion of space, which has sections called "Understanding the expansion of space" and "What is the universe expanding into?" (Though I don't know why that section says that if space is infinite, this would be "easy to conceptualize".) Comet Tuttle (talk) 20:19, 17 February 2010 (UTC)

I am content to allow our concept of beauty to abide in metaphysics. The OP may find the article Intelligent design helpful. It is not a mainstream view that there is convincing evidence of initial intelligent design. Cuddlyable3 (talk) 20:22, 17 February 2010 (UTC)

Re: "That is, neither the Earth atmosphere has evolved to suit us, nor we evolved to, which means that most likely it was made to be such intentionally." I'd have to say we most certainly evolved to suit the atmosphere, if we had not we would of course not have survived. The atmosphere has changed plenty in the billion+ years life has been around and the life that did not evolve to suit it died off, as you would expect. Chris M. (talk) 21:13, 17 February 2010 (UTC)

The only honest answer is that we don't know why the universe has the properties and physical laws that it has. Our knowledge today is far better than that of our ancestors (to whom nearly anything could seem magical), and presumably our descendants will have a better and more fundamental understanding of the universe than we do today. However, we may never know the answer to "Why are things just so?". It is easy to say that life as we know it could not exist if the universe was much different than we know it to be. Of course, we also can not know whether other forms of sentient life might come to exist had things been otherwise, so it is difficult to know how significant our existence truly is.

Given our current state of ignorance (and the possibility that we will never know), I'd say that it is an entirely valid - as an article of faith - to assume that God or some other intelligent creator set up the laws of physics in just such a way so as to allow life to flourish. Such beliefs are essentially unscientific in the modern era since we have no meaningful way to test them, but if they help people find comfort and meaning in their lives, then I would say that they are nonetheless useful for those people. Dragons flight (talk) 21:20, 17 February 2010 (UTC)

It is entirely valid if you don't mind worshiping a god of the gaps. Dauto (talk) 03:46, 18 February 2010 (UTC)

If it were only a matter of people getting some comfort and meaning from an unprovable hypothesis - then I'd be fine with it too. But when they start to use that to prevent my kids from being taught about evolution in school - or to persuade gullible people to commit suicide by flying planes into buildings - then we really have to say "This Simply Isn't True" and mean it. A belief in a god that pushes the big red "CREATE UNIVERSE" button - then walks away is perhaps tenable - if unnecessary - but why does that lead you to have some kind of comfort? Only a god who actually intervenes on your behalf is of any practical use to you - and that's quite clearly ruled out by science - or indeed basic logic. Why pray to a god who walked away from the universe after pushing that big red button? SteveBaker (talk) 16:48, 18 February 2010 (UTC)

Actually, research by Victor J. Stenger has shown that this whole business of the universe being "fine tuned" doesn't entirely hold water. His work isn't published yet (AFAIK) but from what I gather he's found that provided that you assume only the conservation laws (which seem pretty reasonable 'immutable' properties of all universes), then you can't vary single fundamental properties - you have to move them in groups. When you do THAT, you wind up with a very large percentage of possible universes having the necessary properties to allow life to form. If that work turns out to be true - then rolling the dice and coming up with a universe with different constants which obeys these conservation laws would almost always result in a "reasonable" universe. He has written some details here. SteveBaker (talk) 22:18, 17 February 2010 (UTC)

I've never read anything by Victor Stenger before, but the argument in the essay you linked is shockingly naive. He starts by claiming that the alleged fine tuning can be confined to a four-dimensional parameter space; I don't think I believe that but I'll accept it for the sake of argument. Then he says that he investigated 100 randomly chosen values of those parameters varying by ±5 orders of magnitude around the real-world values, and found that many combinations yielded an acceptably large stellar lifetime. His formula for the stellar lifetime (found here) is of the form k x^a y^b z^c w^d where k, a, b, c, d are constants and x, y, z, w are the parameters. This means that the log of the stellar lifetime is a linear function of the logs of the parameters, so it will be larger than the central (i.e. real-world) value in exactly half of his parameter space. If the real-world value is larger than the acceptable lower bound then more than half of the parameter space will be acceptable. He should have realized that immediately, before he wrote the program. I don't understand how a (retired) professional physicist could be so dumb as to resort to statistical sampling for this problem instead of just calculating the output distribution. And why only 100 samples? Even a very slow interpreted BASIC (his program was apparently written in True BASIC) on a very old computer could handle thousands of samples per second. I can't see any reason to stop at 100 except to add spurious randomness to the plot and make it seem less trivial than it really is. At any rate, as trivial as this is, it would be an argument against fine tuning if stellar lifetime were the only constraint and if the parameter values he investigated were natural. But no one would have thought the parameters were fine tuned in the first place if those things were true. As you add additional constraints (and there are a lot of others) you can expect the acceptable parameter space to be whittled down to almost nothing. And he varies the parameters around the observed values. The electron mass is about 10⁻²² in natural units, so he allows it to vary from 10⁻²⁷ to 10⁻¹⁷. But the real question is, why isn't it 1? You certainly don't get an acceptable stellar lifetime if it's anywhere close to 1. This is essentially crackpottery. -- BenRG (talk) 08:48, 18 February 2010 (UTC)

Thanks for the analysis. I hadn't read anything by this guy before either - it seemed interesting that someone with some credible scientific credentials had actually tried to investigate this. But if he screwed up - then that probably explains why his work remains unpublished. SteveBaker (talk) 16:14, 18 February 2010 (UTC)

Selectivity effect. Countless universes with each its set of laws, and us humans happen to be in one of them wondering how come it sound this fine tuned. -RobertMel (talk) 23:40, 17 February 2010 (UTC)

That is one solution that has been proposed. There is not, and probably never will be, any evidence for the existence of other universes, though. --Tango (talk) 00:06, 18 February 2010 (UTC)

Picture a nearly infinite series of universes, some with physical constants such that there is no air on Earth, with us whining here on Ref Desk about how hard it is to breathe without air. There could only be human observers in universes where human observers could exist. There is no need to suppose that Divine Providence engineered a world just right for our needs. If randomly determined physical constants and laws of physics and chemistry were very wrong for us, we would not be here to complain about virtual absence of gravity, or Planck's Constant being 10²⁰ larger, or water contracting when it froze. There would be a vast array of very boring universes, some with no planets, others with no light, and others with very different rules for the formation of chemical compounds such that life (as we know it, carbon and water based) would never emerge. Edison (talk) 05:52, 18 February 2010 (UTC)

Are the physical constants indeed determined randomly? Are there any descriptions of what happens exactly when any or all physical constants and/or properties would be altered (to any degree)? Or what theoretically happens, when one starts messing around with them? Brand[t] 16:01, 18 February 2010 (UTC)

Without any intervention, they are determined randomly, some will never survive more than a fraction of a second, others will. It was even proposed some, a kind of natural selection, universes who survive long enough could be fecund and transmit their laws through a collapsing black hole. It would be like natural selection on Earth..., which means that more universes will emerge with the needed laws to form a fecund universe, and those sets of laws are the same which are needed for life to emerge. Since a universe which can produce many black whole and would survive more would be more fecund, the kind needed to form stars. See Lee Smolin about that. -RobertMel (talk) 16:16, 18 February 2010 (UTC)

That's not known to be true. There is no reason whatever to assume that they are determined randomly. We don't (yet) know WHY they have the values they do - but it might very well be that we find certain interrelationships that force the number to be what they are. The worst case scenario is that they are determined randomly - but over what range? If they are random - plus or minus 1% then that's a different thing than if they are random plus or minus 20 orders of magnitude. They cannot possible be random over an infinite range because then we wouldn't be here...and we are. So even if you assume random settings of these parameters, you have to come up with some mechanism that limits the range - and if/when you find that mechanism, it might very well be that the randomness is limited to plus/minus one part in a trillion. We simply don't know. This discussion only comes about because the Intelligent Design nut-jobs want to make it sound like the answer is SO random that there had to be a designer. SteveBaker (talk) 16:24, 18 February 2010 (UTC)

It's true that there is no reason that the laws are set randomnly as in without range. But, I never meant to say that there was no range, ranges could exist, but if there are infinit numbers of universe, in the scale which could somehow compete with a boundless randomnity, then ranges don't need to exist. -RobertMel (talk) 16:41, 18 February 2010 (UTC)

If there are an infinite number of universes with randomly set parameters for each then the problem is trivially solved. The difficulty only exists if this is a small, finite number of universes (like "one") and the values are determined randomly and over a very large range and if over a large fraction of that range, no life of any kind is possible. But even then, the anthropic principle is a perfectly valid explanation in the absence of something more satisfying and is more than enough to deny the necessity of an intelligent designer. However, science isn't here to disprove the existence of god(s) (although it often looks that way) - it's here to find answers to deep questions. For that, the anthropic principle is useless. We would very much like to know why these constants are the way they are - are they determined by some deeper relationship? Could they have been different? Did they come about randomly? If so, over what range? Are there multiple (or even infinite) universes - all with different values? These are all great science questions that would lead to a greater understanding and perhaps even some interesting technological spin-offs - but we don't need to answer any of them in order to say conclusively that an intelligent designer isn't required. SteveBaker (talk) 17:04, 18 February 2010 (UTC)

"we don't need to answer any of them in order to say conclusively that an intelligent designer isn't required" - I'd say that is just as much an article of faith as saying that an intelligent designer is required. We don't have enough information to draw a conclusion. Why does a universe exist at all? If there are multiple universes, then why should that be? Etc., etc. The anthropic principle is a statement about the nature of our existence, but it doesn't explain the more fundamental question of how did there come to be a universe like ours. Maybe someday we will know the answers, but right now saying that God could definitely be excluded seems just as unfounded as saying that God must definitely be the answer. Dragons flight (talk) 21:19, 18 February 2010 (UTC)

If I had said that we didn't need to answer this in order to prove that an intelligent designer does not exist - then you might maybe have a point - but I didn't. This is evidence that an intelligent designer isn't required - which is quite something else. I can show that an ID isn't required by coming up with any hare-brained theory for the formation of the universe. To show that there definitely was an ID, you have an awful lot of proof to come up with...and we all know you don't have that or the question would already be solved. What the anthropic principle shows is that even if the probability of a single universe having exactly the right properties for human life to form is exceedingly small - providing it's not exactly zero, then we have an acceptable hypothesis that doesn't require ID. Hence suggesting that this 'fine tuned' property is proof of ID is pure nonsense. It proves nothing of the sort. The flip side of that argument would be if we could somehow prove that the universe HAD to form with a set of properties that would inexorably lead to intelligent life - then we would have proved conclusively that no intelligence was involved in the setting of those parameters. However, we have not shown that yet - and maybe we won't ever manage to do that. So this leaves us in a state of knowledge that says that we don't require ID - and that the ID proponents may have lucked out and guessed the truth against spectacular odds. Occams' Razor and Russels' Teapot suggest to rational people that the simplest explanation is the best - hence, no ID is where the smart money is...scientifically speaking. SteveBaker (talk) 22:49, 18 February 2010 (UTC)

I still disagree. Your "acceptable hypothesis", if true, merely pushes back the question of primary cause one more notch. Or to put it another way, the man-behind-the-curtain (if there is one), would simply be doing something like creating a multiverse that allowed for the creation, however improbable, of a universe like ours. That seems to be a property of all such theories, in that they can only push God further back into the shadows, but they can't rule him out any more than any existing evidence can rule him in. Eventually one might ask: "If God's only role was create the rules that eventually led to the creation of the universe, then is that really 'God' as most people envision him?", but that is rather something of a diversion. Did an intelligent process have any role in creating the physical laws that allowed our universe to exist? I don't know, but as long as physics is based on the assumption of physical laws whose origins are unknown, I don't see how any hypothesis could claim to exclude the possibility of God. Dragons flight (talk) 23:54, 18 February 2010 (UTC)

I can't believe you said that! Your "God hypothesis" also only pushes things back one more notch. Why do religious/ID people never address the question (which for scientists is inevitable) of "Where did the designer come from?". The only answers out there are of the "God was always there" or "Time is meaningless for God" or (worse still) "It is heresy to ask such questions" variety. But if that's an acceptable answer, then so should be a scientific answer such as "Time and space were formed by the big bang and therefore it is literally meaningless to ask what came before the singularity". That's a solution which (if true - as was recently believed) would not push things back one more step - at least no more than "Time is meaningless for God" does. You may be right that there is no ultimate way to disprove a god. What there most certainly IS is the ability to progressively narrow the influence that this god can possibly have on the subsequent progress of the universe. There comes a point (and I think we're already WELL past that) where if there is a god, there is no point in worshipping him - no benefit that he can possibly provide us with - he might as well not exist in that case. A hypothesis which predicts no new, testable/observable phenomena has zero value. At which point, we might as well simply apply Occam's razor and go with the simplest answer. SteveBaker (talk) 03:41, 19 February 2010 (UTC)

The idea of a Fine-tuned Universe is an interesting one to consider, but the degree of "fine tuning" (if any actually exists) is often grossly overstated, or at the very least stated in a way the leads to gross misunderstanding. I've heard some proponents of the fine tuning argument state that if you used a scale that stretched across the entire universe to representing the possible range of values for the strength of the force of gravity, then life would not be possible if the actual value varied by as much as one inch from what it is. People may take from this that the gravitational constant must not vary by one part in more than 10²⁸ (1 inch / 93 billion light-years) when in fact the actual value of G (6.67428(67) x 10^-11 m³kg^-1s^-2) is not even know to a precision greater than one part in 10⁴, and could presumable vary by considerably more than that without life extinguishing consequences. The trick is choosing the "range of possible values" (possible according to who and why?) as mind boggling huge as desired. I do wish that our Fine-tuned Universe article went more deeply into the numbers that are used and the justification offered for their use. 58.147.58.28 (talk) 02:04, 18 February 2010 (UTC)

I find the idea of a fine tuned universe a complete nonsense. First we don't know if the universe could actually be any different than it is. There is to reason to believe either way. Second we don't know for a fact that life would not be possible in a different universe, or how different it would have to be to prevent life from existing. That doesn't sound like strong grounds for anything as far as I can see. Definatly not strong grounds for a proof of the existence o god. If that's all that the god believers have, I think they are better off simply saying that they believe in god out of pure faith and that is that. Dauto (talk) 04:12, 18 February 2010 (UTC)

I defer to Douglas Adams: ". . . imagine a puddle waking up one morning and thinking, 'This is an interesting world I find myself in, an interesting hole I find myself in, fits me rather neatly, doesn't it? In fact it fits me staggeringly well, must have been made to have me in it!' This is such a powerful idea that as the sun rises in the sky and the air heats up and as, gradually, the puddle gets smaller and smaller, it's still frantically hanging on to the notion that everything's going to be all right, because this world was meant to have him in it, was built to have him in it; so the moment he disappears catches him rather by surprise. I think this may be something we need to be on the watch out for." Imagine Reason (talk) 04:18, 18 February 2010 (UTC)

The presence of multiply universes may additionaly point to external intervention I think. If such complex object as Universe evolved randomly, then why far more simple things like metal details for example do not assemble into a car? The countless universes should be complex too, which reduces their chance of being formed randomly IMO. I think it is very safe to suppose that initially there was nothing (the same way when I want to make a snack without having ham and bread). Then something from nothing has appeared like protons and neutrons, which suggests the external assistance. Brand[t] 06:39, 18 February 2010 (UTC)

I think it is safe to say that there will always be a why or a how beyond the current limits of our knowledge, and one can always choose to believe that the ultimate answer to how our universe came to be is God. I have no objections to that, if that is what you choose to believe. However, it is worth noting that a watchmaker God that sets everything up and then lets it evolve according to fixed and scientific laws is fairly different than the interventionist personal God that many people envision when they pray. Dragons flight (talk) 08:25, 18 February 2010 (UTC)

It also doesn't help with the task of explaining things. If you have a gap where science does not yet have an answer - and you insert a "god" in there - you really haven't added anything to the explanation because explaining how the god got to be there is a vastly more difficult question than explaining the gap that you dropped the god into in the first place. This is becoming most evident as science begins to plug some of the more traditional gaps.

But in this particular case, we don't need a god to explain why the universe is the way it is. Although we'd like a better explanation, the anthropic principle is actually a perfectly sound scientific explanation. In short, if those 'fine-tuned' variables are truly randomly set at the point when the universe popped into existence - then beings exactly like us can only be there to comment on the matter if the dice rolled the way they did. Sure, it might only be a one in a trillion chance that the universe could support life - but if there are a trillion parallel universes - or if the universe is re-made over and over - then sooner or later one will come up with intelligent life - and by definition, that's the one we'll happen to be living in. So we don't have a "gap" here...there is no need for a god to fill it. It would be nice to be able to come up with a reason why it's not a one in a trillion chance but maybe a one in ten - or better still, an absolute certainty - but even without that, we don't have to postulate an even harder to explain 'thing' to cover some horrible error in science as we know it. What we know is that no matter what the odds of getting a universe like ours - so long as the probability isn't zero - then this is how it turned out. If you roll three dice and you happen to get three sixes - do you seek an explanation as to WHY they came up that way? No! You realise that this was always a possibility - and that's what happened. SteveBaker (talk) 16:14, 18 February 2010 (UTC)

After millions of years of its existence the Brownian motion failed to produce something more than just a random bouncing. So it’s absurd to state that our universe started to produce the necessary stuff and subsequent components by itself, as if it were intelligent. I share the view that the constants were not set randomly, but if so, the logic, mine at least, suggests them to be affected externally and, most likely, to be rendered immutable to avoid terrific troubles.That’s why these values are constant, not variable like many others. And since God by definition is not detectable scientifically, being transcedental , I think the gap could be filled in such a way. Also, any possible intelligent designer including God would be naturally wiser than we, rendering us incapable to adequately describe him. Brand[t] 21:02, 18 February 2010 (UTC)

I'm not sure what that disconnected set of ideas proved - but let's take your reply a bit at a time:

• After millions of years of its existence the Brownian motion failed to produce something more than just a random bouncing. - Firstly, it's billions of years - not millions - secondly, how do you know it failed to produce something? Random bouncing will (over enough volume and time) eventually produce the complete works of Shakespeare. But it can destroy things just as quickly. You don't know that.
• So it’s absurd to state that our universe started to produce the necessary stuff and subsequent components by itself, as if it were intelligent. - The word "So" implies that your second thought follows from your first. But random motion can produce meaningful things (eventually) - if you roll 100 dice enough times, sooner or later, they'll all come up 6's. If you pack them into a 10x10 grid, they could equally probably produce a crude approximation of the MonaLisa (actually, more probably). That's not "intelligent" though - that's just random. Well, the appearance of the first self-replicating molecule could perfectly well have come about randomly - and having done so, would inexorably evolve into something like the life we see around us today. You don't need intelligence to get complexity.
• I share the view that the constants were not set randomly, - I didn't say that I believed that. I have an open mind about how those parameters came to have the values they do.
• but if so, the logic, mine at least, suggests them to be affected externally and, most likely, to be rendered immutable to avoid terrific troubles. - The trouble with "affected externally" is that for us to be talking about a "universe" there can't be "externally" because the word "universe" means "absolutely everything". If you want an external influence, you have to explain about how THAT came about. This is the massive problem with ID. If you finally prove that there is a "designer" out there - the very next words out of your mouth had better be "...and the way the designer came about was..." with a ton more explanation. The usual cop-out is to say "The designer was always there" or "Time does not exist for the designer". But when scientists offer the much simpler explanation that "The singularity that formed the big bang was always there" or "Time does not exist for the singularity", you ID'ers get upset and accuse scientists of failing to answer the question. So - how about you explain why the ID's "designer" offers us any additional explanation?
• That’s why these values are constant, not variable like many others. - Eh? So you're saying that God is what stops the charge on the electron from changing over time? As "God of the gaps" arguments go - that's the mother of all tiny gaps! Perhaps god also stops the value '6' from magically becoming '7'? Constants are (by definition) constant.
• And since God by definition is not detectable scientifically, being transcedental , I think the gap could be filled in such a way. - God is only undetectable so long as his believers continue to retreat into every smaller gaps. "God created created the heavens and the earth"...but when we prove conclusively that the earth was formed by gravitational forces operating on the stellar disk - you guys don't go "Huh! Well, whatddayaknow? We must have been wrong!" - instead you retreat a bit into a smaller gap. We prove that the story of Genesis is complete bullshit - and you retreat into "Well, that's just a metaphor". When we show that above the clouds, there is no heaven - you push it off into some metaphysical plane where we can't disprove it anymore. This "not detectable" approach forces your beliefs into smaller and smaller gaps. In the end, the problem is this: For a god to be entirely undetectable - he has to hide very, very carefully. Answering prayers is detectable, miracles are going to be violations of thermodynamics and conservation laws that science can spot a mile off. Your great and mighty god is reduced to cowering in tiny little gaps where science can't (yet) find him. That's not really a very pretty picture is it? So, sure - you can plug a god into the gap where science doesn't know how these numbers came about - but what do you do when we prove conclusively where they actually did come from? You have to run and find another gap.
• Also, any possible intelligent designer including God would be naturally wiser than we, rendering us incapable to adequately describe him. - You have no proof of that. Tell me - if your designer is so amazingly wise - why the hell did he come up with such an amazingly crappy design for the Recurrent laryngeal nerve in the Giraffe? SteveBaker (talk) 23:33, 18 February 2010 (UTC)

Well, I would reply in the same order.

• Billions of years are naturally better and in order to calculate the probability of producing the complete works of Shakespeare from the Brownian motion you should take some limited time span (800 billion years for example), not infinity. But is there a single evidence, that the Brownian motion has produced something sizeable and useful after billions of years have passed? Imagine another situation. A single normal car has everything to set it in motion. But it will not move unless we affect the ignition and accelerator. Maybe someday something will fall down, penetrating the roof and pressing down the pedal, but even after the infinitely long period of time (after the infinity, roughly speaking) nothing would be able to turn around the keys and ignite the engine. That’s why it’s impossible that our universe appeared and evolved randomly, the probability is zero I think. So the basic idea of specified complexity is quite plausible.
• I didn't say that I believed that. You state above: There is no reason whatever to assume that they are determined randomly and even: A belief in a god that pushes the big red "CREATE UNIVERSE" button - then walks away is perhaps tenable.
• The word "universe" may mean "absolutely everything" just in terms of our science. A single cat doesn’t know, from what and how it evolved. But unlike that cat, our advantage is that we as Homo sapiens can make plausible assumptions even within the cosmological argument, other than throwing dice around.
• So you're saying that God is what stops the charge on the electron from changing over time? I believe yes, since that value is a constant, unlike the values of such fundamental force like gravitation which may vary.
• "God created created the heavens and the earth"...but when we prove conclusively that the earth was formed by gravitational forces operating on the stellar disk - you guys don't go "Huh! Well, whatddayaknow? There is an artificial gravity, which means that initially it would not occur unless we influence the spaceship in a proper way to rotate it. Besides, actually there is an example of divine omnipotence, when God turned detectable and accessible to humans – Jesus (unless you don’t believe in him or think he was merely a human). He was certainly able to scientifically explain the divine engineering, in proton-neutron terms for example, but for obvious reasons did not – it was a different historical period of mankind. Brand[t] 06:23, 19 February 2010 (UTC)

I don't quite understand what you are getting at, your arguments seems disorganized. How can you suppose the chances are zero, under what basis? It is pointless to discuss the improbability of our existance to prove a God, because had we been not there we would have never asked those questions. (selectivity effect) It took a lot of orders (which means, a lot of accidents) for us to be here. The main point is that, for example us humans, we would have never been here, without all the other nature trials which we have evidence of. Of course we see order, because we are here, we being here required this order, which gives the illusion of a creator. The accident turning the key would have been irrelevant had there been no car in the first place. Some cars will be destroyed and turned into another thing until by accident the key is turned. Suppose that insteed of the key turning the engine on, it gives the car awarness of its seroundings and of its own existance. What the car will observe, it will observe the complexity of its own existance, and the complexity of all the machinery which were created by accident to permit its own creation. The car will believe it was created by a being until it discovers all the other trials. This amount to when Darwin discovered evolution. As for the laws of physic which seems fine tuned. Of course they will seem fine tuned for you and me, because if laws didn't permit your existance you would have never been here. So what you see as orderly laws is expected, just by the fact that an evolved being such as yourself is trying to understand and questioning their improbability. Of course there can alws be a god setting the laws, but you have to explain that being own existance.

We one day may simulate a universe in a Quantum computer, with entities which become self aware and wondering about their own existance, making of us gods. There will be nothing which would permit those entities to distinguish those universes from ours. But I highly doubt that's the kind of god which you had in mind. -RobertMel (talk) 15:53, 19 February 2010 (UTC)

I have already programmed a computer to be self-aware. It is not very smart, but it is self-aware. It speaks very little English, but it does know the answer to one question, "Are you self-aware?" It always answers "Yes" to this question, and it answers "I don't understand your question, because the universe is so very complicated and I have limited processing power" to every other question. That poor computer - it suffers from a perpetual crisis of existentialism - but it is indisputably self-aware! All you have to do is ask it! Nimur (talk) 17:25, 20 February 2010 (UTC)

How can you suppose the chances are zero, under what basis? Existing evidence. Our universe is not a crude approximation, but a well-ordered reality. It means that the random cause, instead of tossing dice, packed into a 10x10 grid (which is already an evidence of external intelligent influence) throughout zillions of years, would have needed an oil and canvas at least (i.e. appropriate and meaningful stuff) to produce a Mona Lisa-like image. I think Dembski’s problem is that he applies specificed complexity to living forms instead of non-living. Unlike live forms, the matter or any non-living form has no stimulus to appear and/or evolve in a meaningful manner by default and thus requires an external assistance. But every physical life form requires matter to appear and evolve. Also, a random cause would make all physical values to be either constant (fixed) or variable in my opinion. But the fact is that some values are constant and some are variable.

The accident turning the key would have been irrelevant had there been no car in the first place. Some cars will be destroyed and turned into another thing until by accident the key is turned. Do cars appear out of nothing? Turned into another thing until by accident the key is turned? Turned by what? Which natural accident would turn the keys? The creator, whoever he is, seems the only one to act beyond the confined laws of science (like admin), including those not yet discovered primarily because they were created by himself (the same way when we develop and pass various new laws, which did not previously exist – civil, criminal etc). I would add that God (or an uknown ID, as you wish) rendered himself generally undetectable probably because his existence and the complexity of his acts exceeds human understanding and is coupled with a certain degree of freedom of choice. That’s why one can only operate with observations and comparisons, but applying duck test, that would suffice, sapienti sat. Brand[t] 08:38, 20 February 2010 (UTC)

In my world view, cars have just assembled naturally. Of course, it took 4 billion years of evolution to get some of the assembly equipment in good working order. As for a fine-tuned universe, it seems like a dead-end argument since whatever airtight case for fine-tuning you come up with must also apply to whatever universe your "external force" grew up in. --Sean 16:46, 18 February 2010 (UTC)

You misunderstood the "sentient puddle." It is a story about how life can fit in the universe nicely by having developed in it and not at all designed for it. 67.243.7.245 (talk) 14:09, 19 February 2010 (UTC)

Brand, I don't you're really understanding Steve's points. Take the dice example, see this [11]. But basically the oil and canvas are the particles in the universe which due to the laws of nature have the ability to form complex structures. Ultimately there's no evidence for a god but what I would like to know is why you think a God that made himself undetectable deserves any attention? He created the universe. Well fantastic, that's quite a feat. But it doesn't mean that God was Jesus and if he doesn't perform miracles/answer prayers/etc. then why should I build my life around it? Do you spend your time worshiping the man who invented the lightbulb, or the automobile? It's fantastic that they did it but enjoy it and get on with your life. TheFutureAwaits (talk) 00:40, 22 February 2010 (UTC)

Capacitor

When a capacitor charges, both the negative and positive plates will always have the same charge (ie current in = current out). Why is that? —Preceding unsigned comment added by 173.179.59.66 (talk) 19:29, 17 February 2010 (UTC)

Current passes through the capacitor which builds up a charge of stored potential energy in the form of a voltage difference between the plates. See the article Capacitor. Cuddlyable3 (talk) 20:13, 17 February 2010 (UTC)

Yeah, I understand that...but why are the two charges equal, and not different? —Preceding unsigned comment added by 173.179.59.66 (talk) 21:13, 17 February 2010 (UTC)

Isn't the charge stored in the dielectric separating the plates? One dielectric, one value for charge. Add or take away electrons from either plate, and the one value of charge in the dielectric changes. In a Leyden Jar, the two conductors (inner and outer can be removed and grounded, then the capacitor reassembled, and found to be charged, because the charge was stored in the dielectric. Edison (talk) 21:22, 17 February 2010 (UTC)

No, the charge is in the plates, the dielectric must be nonconductive. The two sides normally hold equal amounts of charge because they are connected to metallic wires which supply large quantities of movable electrons -- if one side had an excess of charge, it would attract charges from the wire on the other side until the charges were balanced. If you disconnected both sides of the capacitor, it would become possible to have unequal charges on the two sides. Looie496 (talk) 23:10, 17 February 2010 (UTC)

Of course the dielectric is nonconductive. But note that a disassembled capacitor, with the metal plates thoroughly grounded, when reassembled is found to be charged once again, supposedly because of the charge stored in the dielectric. If it were stored only in the plates, then shorting them together and to ground after disassembling a Leyden Jar ( a common lab demo in college physics) would prevent the reassembled capacitor from being charged ( without connecting it again to some source of electricity). Edison (talk) 00:39, 18 February 2010 (UTC)

Thanks for the simple answer! —Preceding unsigned comment added by 76.68.246.12 (talk) 23:42, 17 February 2010 (UTC)

My thoughts are: charge (electrons etc) is moved from one plate to the other when charging. So one plate ends up with a charge +Q that has been supplied by and moved from the other plate that now has acharge of -Q. Charge exists on the plates (or the surface of the dielectric). By contrast, the energy is stored in the dielectric. In the above case, when the plates are removed, (most of) the stored charge will then reside on the surface of the dielectric. This charge will spreed out onto the plates when they are reattached. What happens when one side of the capacitor is connected to the earth (a source of infinite charge)? —Preceding unsigned comment added by 79.76.229.198 (talk) 01:57, 18 February 2010 (UTC)

You could charge an ungrounded Leyden Jar or capacitor to any voltage which was not so high as to rupture the dielectric. Then you could connect one plate to ground: no effect on the voltage across the capacitor, or the energy stored in it. Next, connect only the other plate to ground: again the voltage and stored charge are unaffected. The earth is indeed a giant conductor, but a giant conductor connected to one side of a capacitor would not change the charge, it would just change the voltage relative to that ground, causing one plate to be at zero volts from ground and the other to be at the full voltage relative to ground. Transformer secondary windings work similarly. Edison (talk) 05:39, 18 February 2010 (UTC)

Geological history of CT or North Eastern US coastline

I don't know where to go to find the geological history of CT, US (or NE US coast). Mostly interested in knowing if and when a huge galacier passed through this area. --Reticuli88 (talk) 19:53, 17 February 2010 (UTC)

• Wisconsin glaciation. Rmhermen (talk) 21:34, 17 February 2010 (UTC)

See also Laurentide ice sheet. Deor (talk) 23:45, 17 February 2010 (UTC)

And here is a brief account that focuses on Connecticut in particular. Deor (talk) 00:28, 18 February 2010 (UTC)

Semen and skin

okay, this question could be slightly improprious, so stop reading if you want.

I heard that human semen is excellent for the compexion of the face; is this true? Would rubbing semen in one's face actually be good for the skin? If so, then why? 82.113.106.198 (talk) 19:53, 17 February 2010 (UTC)

We can refer you to the article Semen. I know of no reliable source for what you have heard. I have changed the question title for easier reference noting that WP:NOTCENSORED. Cuddlyable3 (talk) 20:09, 17 February 2010 (UTC)

It would be a very amusing study to read if a study was carried out to study this hypothesis (or maybe it already has been done?). Acquiring funding and volunteers though might be a challenge. --antilived^{T | C | G} 23:58, 17 February 2010 (UTC)

College sophomore psychology students would sign up for almost any boring experiment or indignity for a few dollars or some course credit. This included studies of sexual arousal, or experiments involving painful electric shocks. The difficulty would be getting such an experiment as the one described by the questioner approved by the "human subjects committee." Edison (talk) 05:29, 18 February 2010 (UTC)

I find it tends to make my skin rather tight and shiny when dry. —Preceding unsigned comment added by 79.76.229.198 (talk) 01:59, 18 February 2010 (UTC)

There are some data on Facial_(sex_act)#Cosmetic_usage regarding this matter.--121.54.2.188 (talk) 02:00, 18 February 2010 (UTC)

Tangentially related is Semen#Psychological aspects. Which is worse, acne or depression? 58.147.58.28 (talk) 02:16, 18 February 2010 (UTC)

Reaching the conclusion that semen must chemically act as an antidepressant is a strange one. Wouldn't it make more sense to say women who have been getting laid more are happier? Mac Davis (talk) 06:57, 18 February 2010 (UTC)

They compared groups with/without condom use. Ariel. (talk) 03:53, 19 February 2010 (UTC)

Did they try to account for confounding factors like differences between the groups other then a regular dose of semen? I'm sure it's occured to many as it did to me that there's likely to be a difference between the average of both, for example women who have sex with men without using condoms may be more likely to be in a committed relationship. As for those who aren't in a committed relationship, the women who don't use condoms may be more likely to trust even casual partners and/or be move naïve about the risks of sex and may be more relaxed (well until they get a STD or pregnant) whereas the women who do use condoms even though they do use condoms may still be more concerned about the risks and so may not find sex as enjoyable. Nil Einne (talk) 21:26, 21 February 2010 (UTC)

Are you sure you weren't told a fib? I know someone who told his girlfriend that semen was full of nutrients that women couldn't get any other way, for obvious reasons. She believed him...--92.251.162.146 (talk) 22:00, 21 February 2010 (UTC)

Variables in procession

can anyone explain what the various constants in this article stand for, notably R and q are given without explanation Lense–Thirring precession

Cheers —Preceding unsigned comment added by 129.67.116.172 (talk) 20:47, 17 February 2010 (UTC)

I can only offer wild guesses (R probably is the radius of the large rotating mass), so I have added a request for expert attention, see Talk:Lense–Thirring precession#Expert attention needed. -84user (talk) 14:07, 18 February 2010 (UTC)

Thank you. I hope someone can help.

Outgassing on Earth and Mars

Earth is beleive to have runaway greenhouse effect when it is on the way as the sun warms up. Because Earth and Mars is bigger I thought the outgassing would be slower than the outer planet's moons. I still don't what what it means when Earth becomes Venus like planet. Will it's atmopshere become thicker. During this time it is possible that as Mars's surface temperature gradually rises, carbon dioxide and water currently frozen under the surface soil will be liberated into the atmosphere, creating a greenhouse effect which will heat up the planet until it achieves conditions parallel to those on Earth today, providing a potential future abode for life. From Mars citation from Formation and evolution of the solar system said Mars may become like earth again and Mars is only little bigger than Titan when sun just heats up Mars atmosphere can become thicker but I wonder if it can have any oxygen and can have a watery surface. This shows Mars atmosphere won't just leak away. This source is cite from google books and it is not speculation.--209.129.85.4 (talk) 20:50, 17 February 2010 (UTC)

Atmosphere to boil away on Earth

On earth ocean boil at 100 C (212 F) but what temperature will our atmosphere black out into space and become like Moon is it over 600 F?--209.129.85.4 (talk) 20:52, 17 February 2010 (UTC)

I don't know what the actually temperature would have to be, but given that Venus has >90 times as much atmosphere as we do and a surface temperature over 850 F (450 C), I think we can confidentially assume that the temperature to boil away the whole atmosphere is over 600 F. Dragons flight (talk) 20:58, 17 February 2010 (UTC)

The ocean certainly would not boil at 100C. It is salt water which means it has a lower boiling point then regular water, various sources in quick google searches point to a change of around 20 degrees in boiling point, but it various depending on the salinity of the particular part of the ocean. Chris M. (talk) 21:09, 17 February 2010 (UTC)

Salt water boils at a higher temperature than fresh water, not a lower one, per Boiling-point elevation. Having something in solution also lowers the freezing point, per Freezing-point depression. Sea water is said to boil at 103.7 C (compared to 100 C for pure water). Edison (talk) 21:17, 17 February 2010 (UTC)

Not sure how useful a comparison with Venus is since the gas properties of CO2 and the N2 O2 mixture we have are quite different. Googlemeister (talk) 21:10, 17 February 2010 (UTC)

On the other hand, Venus has more N2 than we do, and if you boil the biosphere and the oceans you'd destroy our O2 and get a lot of CO2 on Earth as well (though no where near as much as Venus has accumulated over billions of years). Dragons flight (talk) 21:39, 17 February 2010 (UTC)

Have you tried looking this up on Wikipedia ? The earth losses gaseous oxygen all the time because it can get enough kinetic energy to escape. The ionic oxygen then corrodes the artificial satellites. There is more here: Atmospheric escape--Aspro (talk) 19:10, 21 February 2010 (UTC)

Question about male genitalis

Why do male genitalia flop around?

The testes work best at temperatures slightly less than core body temperature. This is presumably why the testes are located outside the body. See the article Testicle. The Penis that forms the other part of the male genitalia must project in order to be able to penetrate the female genitalia. Please sign your posts. Cuddlyable3 (talk) 21:39, 17 February 2010 (UTC)

And what's more, observation has demonstrated that many animals streamlined for marine life (cetaceans, for example) exhibit internally located testicles that are surrounded by a venous plexus that effectively lowers the regional temperature. DRosenbach ^{(Talk | Contribs)} 13:51, 19 February 2010 (UTC)

glacial lake in siberia

File:Last glacial vegetation map.png This map shows an enormous lake covering eastern Siberia during the last ice age. What was its name so i can look it up? —Preceding unsigned comment added by 70.29.47.142 (talk) 21:32, 17 February 2010 (UTC)

It's hard to tell which lake you mean - but if you bring up Google Maps, you should be able to zoom in and find it very quickly - IF it's still there...it probably isn't - in which case it may not have a name. SteveBaker (talk) 21:47, 17 February 2010 (UTC)

It is the blue area covering eastern Sibera and north of the bering land bridge. Blue on the map means a lake. It is not still there, it was there in the ice age. I would like to find out more about it. there are names for the ice age lakes in north america like Lake Ojibway. 70.29.47.142 —Preceding unsigned comment added by 70.29.47.142 (talk) 22:07, 17 February 2010 (UTC)

I don't think that's a lake; it's an area of "polar and alpine desert". The two colors in the legend of File:Last glacial vegetation map.png are virtually indistinguishable, at least on my monitor. Deor (talk) 23:34, 17 February 2010 (UTC)

I checked the colours with Gimp and you're correct. FYI lake colour is 0094c8 and polar-and-alpine is 00a4c0; the two are very close indeed. -- Finlay McWalter • Talk 00:07, 18 February 2010 (UTC)

thank you. Does that mean Tibet was not a lake either? I don't see how it could be if there were still mountains there. Thank you for helpimg. 70.29.47.142 —Preceding unsigned comment added by 70.29.47.142 (talk) 00:47, 18 February 2010 (UTC)

Yes, it looks to me like Tibet was another "polar and alpine desert" area. As far as I know, there have never been freshwater lakes of that size on the earth. Deor (talk) 18:34, 18 February 2010 (UTC)

The supposed lake in Siberia is contiguous with the Arctic Ocean, which would make it an ocean, not a lake. Here's another question, though. I know that there were some very large lakes in North America during the Ice Age (such as Lake Bonneville and Lake Lahontan). Why aren't these shown on the map? --Smack (talk) 20:01, 18 February 2010 (UTC)

February 18

A greenhouse on Mars

If you put a large air-tight greenhouse on Mars and fuilled it with air, how warm would it get? Would earth-plants grow in the Martian "soil"? Maybe with some human 'compost' mixed in? 78.146.206.38 (talk) 00:00, 18 February 2010 (UTC)

To answer the first part, there is no theoretical barrier to designing a solar greenhouse on Mars that operated at comfortable temperatures of plant life. Dragons flight (talk) 00:14, 18 February 2010 (UTC)

The temperature would depend on the latitude. Climate of Mars#Temperature indicates that temperatures do get up to nice warm temperatures (27 °C max), presumably on the equator. With the (literal) greenhouse effect, the temperature inside your greenhouse would be higher than the surroundings, so anywhere reasonably close to the equator should be fine temperature-wise. The Martian soil might be suitable for the growth of Earth-plants - it seems from that article that more research is required. --Tango (talk) 00:18, 18 February 2010 (UTC)

The temperature would drop quite low, especially at night in the winter, unless there was sufficient thermal mass and a high insulation level. Mars gets on average only 43% the solar intensity or "insolation" received on Earth per [12]. The mean surface temperature (outside the greenhouse) is only -63C (per the NASA site, varying with season and latitude). The air pressure is very low, so a greenhouse dome would have to be quite strong to hold in enough airpressure for earth type plants. See also a NASA project looking at a Mars greenhouse. Apparently 1/4 of earth normal pressure would suffice. Actually sounds doable. The Mars Society also has some suggestions how to build the greenhouse. Edison (talk) 00:21, 18 February 2010 (UTC)

As that Mars Society link says, you can keep it warm with what is essentially an enhanced greenhouse effect - they suggest a silver compound in the plastic that will allow visible light and near-IR (ie. sunlight) through but stop far-IR from getting out. --Tango (talk) 00:45, 18 February 2010 (UTC)

a little help with equilibrium constants and partition coefficients as they relate to solubility

Admittedly, the whole "mole product / mole reactant" thing goes over my head when I imagine scenarios like adding more reactant or taking away more product. So ... like take these titration results.

There's approx 0.013 mmol of dissolved iodine (without iodide) in 50 mL solution.

When I add 5 mL cyclohexane, approximately 0.008 mmol of it escapes into the cyclohexane, resulting in a concentration-in-cyclohexane figure of 0.0016 M. From the new concentrations I calculate a partition coefficient of approximately 16.

When I add 8 mL cyclohexane, despite a 60% increase in the amount of lipophilic solvent there's only a 25% increase in extraction ... Indeed, the concentration of iodine in cyclohexane is now 0.00125 M, a concentration fall. This sort of makes sense since as the iodine gets less-concentrated in the water phase, iodine becomes harder and harder to extract from aqueous solution. The concentration in aqueous phase is now 5.6 * 10^-5 M and the new partition coefficient is 22.

This is clearly experimental error right? Shouldn't the partition coefficients remain roughly the same? (We measured concentrations by titration.) Let's take an ideal case with no experimental error and say I'm adding more water or more cyclohexane. How would I use the partition coefficient to predict new concentrations? What does the partition coefficient really mean, as an equilibrium constant? How likely is it that mistitration or something like that is the source of my error? Basically, I don't know how to think of "mol product over mol reactant" when I say add more of one type of solvent to the mixture. Are the concentrations going to rearrange themselves such that the ratios of concentrations in the different solvents will somehow remain constant.

I get even more lost when I deal with saturated solutions and there's apparently an equilibrium constant between the pure solid phase and a dissolved phase as a solute, because if I add more excess solute to a saturated solution, clearly the ratios cannot adjust themselves to the equilibrium constant since the solution is already saturated. John Riemann Soong (talk) 01:34, 18 February 2010 (UTC)

To address your last question, you need to remember that the concentration of a pure solid substance (or even a pure phase of a liquid) has a constant concentration. TenOfAllTrades(talk) 04:03, 18 February 2010 (UTC)

Coming back to the first part of your question, what's the precision with which you're measuring the amount of iodine (to start with, and in each phase)? If that 0.008 mmol iodine is ± 0.001 mmol (for example), then what is the range of partition coefficients that you could calculate (based on 0.007 or 0.009 mmol in the cyclohexane phase)? TenOfAllTrades(talk) 13:38, 18 February 2010 (UTC)

Angular momentum in collisions

The angular momentum of any object can be divided into the angular momentum of it's center of mass, and it's angular momentum with respect to the center of mass. When analyzing collisions, the total angular momentum is said to be conserved. However, sometimes both the angular momentum of it's center of mass and it's angular momentum with respect to the center of mass are considered, but other times only the angular momentum with respect to the COM is used. Why would there be this discrepancy? And when finding the rotational kinetic energy, are both types of angular momentum used? Thanks. 173.179.59.66 (talk) 04:24, 18 February 2010 (UTC)

I think the OP really means ITS center of mass and ITS angular momentum, without apostrophes in the ITS. Cuddlyable3 (talk) 12:50, 18 February 2010 (UTC)

Angular momentum will be separately conserved around any point. Often you only need to consider it around one point to get the information you need. --Tango (talk) 18:02, 18 February 2010 (UTC)

I'm sorry, I don't see what mean... —Precedingunsigned comment added by 173.179.59.66 (talk) 20:38, 18 February 2010 (UTC)

Angular momentum around point P will be conserved and angular momentum around point Q will be conserved and around point R, etc. etc. You often only need to apply one of those conservation laws to get the answer you are looking for. Sometimes it will be easier to use P, sometimes Q. That's why you see different ones used in different problems - you just use whatever is easiest. --Tango (talk) 21:08, 18 February 2010 (UTC)

Hmmm, I guess my question wasn't well worded. Let's say two billiard balls are heading towards each other and collide (with some impact parameter). When doing all the calculations, the angular momentum due to their pure rotation (ie due to w=V/r) is used, while the angular momentum due to their net velocities are ignored. However, in a problem where a superball is bouncing off a wall, both the objects rotation and net velocity are taken into accound when detailing how the angular momentum is conserved. Why would we look at both in one, and only look at rotation in another? If I'm not being clear, let me know. Oh, and he talk about rotational kinetic energy, is it just equal to (1/2)I*w^2, or does the angular momentum of the center of mass need to be considered as well?

Ok, I don't understand that either. The rotation of an individual ball about its centre of mass won't be conserved during such a collision, because it isn't a closed system (the ball interacts with the other ball). --Tango (talk) 01:03, 19 February 2010 (UTC)

But if the rotation of one ball slows down, the other will speed up, keeping angular momentum conserved, right? —Preceding unsigned comment added by 173.179.59.66 (talk) 03:48, 19 February 2010 (UTC)

To be strictly correct, the 'orbital' angular momentum always should be included along with the 'rotational' angular momentum, but under certain circustances one or the other might be considered negligible.Dauto (talk) 15:40, 19 February 2010 (UTC)

Math in physics

Out of curiosity, do most physicists (outside of ultra theoretical fields like string theory) spend time manipulating equations and such by hand, or is basically all the math handled by computers. The reason I'm asking is that I'm sifting through a textbook on quantum mechanics, and it's evident that to make any progress, physicists back then had to be able to work out equations and model situations by pen and paper...is that still true today? —Preceding unsigned comment added by 173.179.59.66 (talk) 04:40, 18 February 2010 (UTC)

Yes, even experimental physicists still need to keep the pen and paper at arms length. But computers play a increasingly indispensable role on more advanced calculations. Dauto (talk) 05:04, 18 February 2010 (UTC)

To turn the (usually continuous) models of classical physics into discrete computer-solvable models which have the same properties as the original continuous model (conserved quantities, stability, ...) is mathematics in itself. In short: you need to use mathematics in order to get the computer to do the mathematics you want it to do. http://en.wikipedia.org/wiki/Numerical_methods —Preceding unsigned comment added by 157.193.173.205 (talk) 10:57, 18 February 2010 (UTC)

There is really three parts to this - there is the business of arithmetic - plugging actual numbers into the equations to get answers in practical, numeric form - and for that, a simple calculator will sometimes suffice - but computers are better for repetitive stuff. Another aspect is taking raw data and performing statistics or fitting equations to those numbers (for which computers are pretty indispensable). But the other part is in the development of the equations themselves. Computers are making inroads into that too - we have 'symbolic math' packages that can manipulate equations symbolically - but it still takes a human mind to spot some of the subtle changes that can change a sheet of paper covered with hieroglyphics into something small, elegant and memorable. SteveBaker (talk) 15:52, 18 February 2010 (UTC)

In my experience, "it depends whether the physicist knows how to tell a computer to solve their problem." That depends on the individual physicist's level of interest and formal training with computers. I hang around mostly with "numerical physicists", which is sort of techno-jargon for "computer programmer". The types of problems we know how to solve with computers reach pretty far and wide. Categorically, we use more computational power than a theoretical physicist. For example, this last week I have been solving the wave equation for residuals in a numerical inversion scheme. Now, when a theoretical physicist "solves the wave equation," they write down some variables on paper and call it "solved." When I "solve the wave equation," that means that I arrange the equation to the simplest form that I can use to represent. Then I formalize an algorithm, and write computer code to represent that scheme. When the computer "solves the wave equation," it reads input data, performs calculations on that data following my instructions (that hopefully represent some physical process), and spits out numerical output data representing a model of experimental observations. So in some sense, both me and the computer are doing math - but I save the redundant calculations for the computer, and the mathematical formalism for myself. We blur the line as far as where the mathematics is actually being "done," and me and my team of powerful computers really solve the wave equation together.

Obviously, the simplest case to consider is basic arithmetic. I'm mathematically inclined, but even I have limits - so when I need to determine a value like (36 + (50*2)/1024)/4, it's a waste of my time to do that in my head or on paper. A computer gives me the correct answer, the first time, as quickly as I can type that in. But in my brain, I have done math to estimate the acceptable range of answers I expect. In that case, the computer has pretty much done most of the math.

Non-arithmetic calculation is a little harder to type into a computer. If I want to know the instantaneous phase of a function or a scale-factor for a fourier transform, I often have to decide whether it's easier to use a symbolic algebra system, a numerical approximation, or a paper-based analytic solution. It depends on the problem. But I'm a physicist, not a "number-cruncher" - so it'd be a mischaracterization to say that I spend all day typing out equations and hitting "enter." So let me diverge a little and explain a bit about what a physicist like me actually does.

People come to physicists with quantitative problems that they would like to answer. In my particular field, they come to us with field-recorded geophysical survey data, and ask us to generate images of the Earth from it. We want to perform this process faster and better, creating clear pictures even if the source data is crappy. So, I look at the physics that represents the field-data collection; I model the physical phenomena, observe the effects of unknowns and interferences, and use those insights to design an algorithm to convert input data into output data, while preserving the physical constraints that we know apply.

I would categorize the design of algorithms as a subcategory of "mathematics." Now, whether we design a particular algorithm with a computer or not depends on its complexity. Having some training in formal software engineering, I find UML diagrams to be a great way to set forth a large numerical physics scheme - especially since I like modular code. So, I can use a CAD tool to help me draw out the mathematical operations I plan to do. But, I also keep a stack of blank paper at my desk to scratch work on - diagrams are easier drawn by hand than by mouse. When I have to do geometry, I do it on paper with a pencil. When I need the value of a tangent, I get that answer from a computer (or desk calculator). When I want to do a coordinate transform for an integral kernel, I often use a computer algebra system, but more often than not, I need to do it by hand anyway. In this way, I am "doing math" - I am applying the structure and formalism of analysis to solve a physics problem. The overwhelming majority of this stage of work is by hand and in my brain.

By the time I have formalized my problem, I inevitably write it out as a series of program statements, in the form of a standalone subroutine, a full-blown application program, or a short script for simple arithmetic - all depending on the scale of the problem. The repetitive calculations are performed by machine - and sometimes, intelligent mathematical decision-making is programmed in as well. I would say that almost everybody (physicist or not) knows how to perform arithmetic by computer; almost all physicists know how to perform algebra and calculus by computer; and many specialized physicists and mathematicians (and others) know how to perform matrix mathematics, optimization (mathematics), and so on.

One of the turning points in formal physics education is being able to distinguish the subtle, qualitative difference between "math" and "physics." In other words, when a physicist sees a new form of the wave equation, they aren't looking at the values of the constants - they're looking at the qualitative interactions and relationships between components. (Ask a real physicist whether Schroedinger's equation, which defines a wave-function, is actually a wave equation! The way they approach that question will astound you). And if you sit in on enough physics seminars, you'll inevitably hear some stodgy old guy grumbling something to the tune of "That's all great, but where's the physics!?" What they mean by this is that despite a load of impressive mathematical maneuvering or experimental observation, the presenter has not identified any qualitative physical principle. In the same way, when you ask whether a physicist manipulates math by hand or computer, they can really do either - whether their physics needs a numerical result will modulate the way that they interact with their computers. Nimur (talk) 22:35, 18 February 2010 (UTC)

Great, thanks for the detailed response. PS Is the Schroedinger's equation a wave equation? —Preceding unsigned comment added by 173.179.59.66 (talk) 00:03, 19 February 2010 (UTC)

Yes. See the article Schroedinger's equation. Please sign your posts. Cuddlyable3 (talk) 17:02, 19 February 2010 (UTC)

Actually it is a diffusion equation ([13], [14]), because the time derivative is first-order and complex (a complex parabolic partial differential equation); while a wave equation is a hyperbolic partial differential equation). Ultimately, you can define a "wave equation" a lot of ways - but most commonly, the defining factor is whether you can construct an invariant of the form (x_i +/- v*t) - in other words, propagation - which cannot be done for Schroedinger's equation! It's the defining state-equation for the wave function - but it is not a wave equation! To some extent, this is semantics and a matter of definition - but the idea is that we care about the physics that the mathematics represents - in other words, the algebraic term that represents wave propagation is decidedly absent in the Schroedinger solution. This means a lot of things - there is no effective velocity to propagate perturbations of the wave-function. This has implication to quantum entanglement, because in the absence of a term to define a velocity, technically there is no speed limit on the propagation of quantum information - hence the paradox of faster-than-light propagation of quantum entanglement information! So, by playing with the maths analytically, we can try to peel away at the actual physics implications. Nimur (talk) 18:14, 19 February 2010 (UTC)

Hydrogen bond position transition

I was trying to understand the File:Glycine-zwitterion-2D-skeletal.png variant of Glycine but then I realized that File:Glycerin Skelett.svg might be subject to the same hydrogen bond position transition.

What reasons are there to believe that glycerin hydrogen bonds are stationary? 99.60.3.241 (talk) 05:02, 18 February 2010 (UTC)

In glycine (the neutral form), there is an "acid" part (a hydrogen can be released easily) and a "base" part (has a high affinity for free hydrogen). Acids and bases react with each other pretty well, and the result is the zwitterionic form. Glycerin does not have any part that is particularly acidic or basic, so it does not change to an alternate hydrogen attachment pattern. DMacks (talk) 18:25, 18 February 2010 (UTC)

Black hole

Hello i have read article on black hole but i do not understand how in some documentary space time is shown to be warped so much that it is such one layer is underneath or over lap with another layer such that a large enough distortion of gravity though to another place in space time that is space can be warped by mass but how can it tunnel be created or what causes space to warp in such that the infinite steep sides of a black hole gravity impression comes out on space time instead of just going forever (Dr hursday (talk) 06:29, 18 February 2010 (UTC))

It sounds like an Einstein-Rosen bridge. Check out that article and see if it answers your questions.  :) Mac Davis (talk) 06:54, 18 February 2010 (UTC)

Hello yes this is what I am talking about but i do not understand how the "U" curve at the left of this picture http://en.wikipedia.org/wiki/File:Worm3.jpg occurs. what causes this? (Dr hursday (talk) 07:01, 18 February 2010 (UTC))

The U is only there because of the way the image is drawn. The same thing is happening in this image (imagine the plane "above" the wormhole extending on forever instead of only in two spots). The only difference is the way it was drawn. The U is there because two places in spacetime are connected by a jump through a higher dimension. If you were on any part of the "U" you would not notice any bends and it would appear perfectly "flat." Mac Davis (talk) 07:43, 18 February 2010 (UTC)

The "higher dimension" has no physical relevance, it may be useful to "visualize" the situation but it need not "exist" in any physical sense. The last paragraph in http://home.fnal.gov/~skent/cosmo/cosmo3.pdf makes this point too. —Preceding unsigned comment added by 157.193.173.205 (talk) 08:28, 18 February 2010 (UTC)

Strange bug

Omg what is this. Can someone tell me? --✶♏‭ݣ 06:31, 18 February 2010 (UTC)

Belostomatidae. -- kainaw™ 06:35, 18 February 2010 (UTC)

Ew ew ew. But thank you. Ew. *shudders* --✶♏‭ݣ 06:37, 18 February 2010 (UTC)

Sometimes fear of the unknown is the scariest thing of all!!! What the Jesus God Hell ever happened to curiosity. 86.4.186.107 (talk) 06:58, 18 February 2010 (UTC)

Given that the sting of the Belostomatidae is considered "one of the most painful that can be inflicted by any insect" and thus is beyond the highest on the Schmidt Sting Pain Index (which is limited to Hymenoptera) "4.0+ Bullet ant: Pure, intense, brilliant pain. Like fire-walking over flaming charcoal with a 3-inch rusty nail in your heel" perhaps Belostomatidae should be rated "5.0+ Jesus God Hell that hurts!" 58.147.58.28 (talk) 08:33, 18 February 2010 (UTC)

Why the profanity? Did your question get a better or quicker answer because of it? Just curious. Kingsfold (talk) 14:51, 18 February 2010 (UTC)

Did the profanity ofend you?Dauto (talk) 15:27, 18 February 2010 (UTC)

No. The answer was quick because all it took was a simple web search. Instead of trying to make a highly juvenile joke by seeing how profane I could be, I went to http://tineye.com and pasted in the URL of the photo. It showed multiple results. The second one was to a Russian site that had a link below the photo right back to the Wikipedia page for the bug. Then, all I had to do was put a link to the article here. I didn't complain because many people seem to prefer to ask questions instead of searching for themselves. -- kainaw™ 14:58, 18 February 2010 (UTC)

Thanks for that link. I didn't know that site. Dauto (talk) 15:27, 18 February 2010 (UTC)

There's a Firefox extension that lets you just right-click on an image and search for it in Tineye. Unfortunately, Tineye seems to have a very tiny index. I wish Google would just buy them and do it right. --Sean 16:10, 18 February 2010 (UTC)

I think it's obvious that the OP was humorously incorporating the sort of reaction one might make upon seeing this beast into his/her question. "Jesus", "God", and "Hell" seem pretty mild profanities for such a sight. --Sean 16:13, 18 February 2010 (UTC)

If you think that's bad, you should meet my Italian girlfriend. Imagine Reason (talk) 16:59, 18 February 2010 (UTC)

I hope you're talking about the use of colorful language and not about the Belostomatidae! (I also hope she doesn't read this page!) SteveBaker (talk) 20:17, 18 February 2010 (UTC)

I'll point out, just because nobody else yet has, that the stuff on the back is a mass of eggs. Looie496 (talk) 00:42, 19 February 2010 (UTC)

Although Ferrofluid smeared on the back of a magnetic beetle would appear similar. I have changed the question title for clearer reference. Cuddlyable3 (talk) 16:52, 19 February 2010 (UTC)

I agree with that but for clarification for any future readers, the profanity discussed above was largely in the title [15] Nil Einne (talk) 22:44, 19 February 2010 (UTC)

What would happen to photon

Hello if I shine a flash light out into space in such a direction that it never encounters anything what happens to the photon over time? (Dr hursday (talk) 06:55, 18 February 2010 (UTC))

It keeps going and will get redder due to the metric expansion of space according to Hubble's law. Mac Davis (talk) 07:20, 18 February 2010 (UTC)

If the photon gets redder where does the energy go? Ariel. (talk) 07:44, 18 February 2010 (UTC)

Nowhere. Hubble flow implies that the farther away one looks, the faster the local matter is moving away from you. By extension, if one travels to those distant places, then you have to subtract the effect of the average local velocity when considering your motion. Hence the farther the photon travels the more it will appear doppler shifted with respect to the local standard of rest. Dragons flight (talk) 08:15, 18 February 2010 (UTC)

Put another way, the photon appears redder because whoever is observing it happens to be moving away from us. Someone moving towards us would see a bluer photon. I think this effect is indistinguishable from that of the space itself between the objects having expanded.. EverGreg (talk) 09:22, 18 February 2010 (UTC)

It's not only indistinguishable. It is the same thing. Dauto (talk) 13:32, 18 February 2010 (UTC)

No. The redshift due to the expansion of space depends on how much space has expanded during the photon's free flight. The usual picture of this is that it's the light-wave that's stretched along with the space it travels in. These are distinctions with real consequences. Consider for instance that distant objects are more red-shifted than nearby ones, so their apparent speed is greater, but an object does not feel acceleration as it recedes from us in this way. Redshift due to expansion also allows an object to speed away from us faster than the speed of light, which is impossible with doppler shift. (Yeah, I read up on the redshift article :-P) EverGreg (talk) 19:32, 18 February 2010 (UTC)

This difference you are pointing out is just an illusion. All redshift derives from the same principle no matter whether it is a gravitational redshift, doppler redshift or cosmological expansion redshift. In fact those distinctions are not as relevant as they sound since what is a doppler redshift for an specific choice of coordinates will be a gravitational redshift for a different choice of coordinates and vice-versa. The cosmological expansion redshift is an artifact from our choice of coordinates. specifically our choice of using comoving coordinates. Dauto (talk) 20:49, 18 February 2010 (UTC)

You cannot do a Lorentz transformation such that an object is accelerating in one choice of coordinates but not in another. EverGreg (talk) 09:13, 19 February 2010 (UTC)

Yes, true but

• A) Lorentz transformations explain the bulk of the effect. See that[16] paper for an explanation on how to build an expanding universe without matter or cosmological constant.
• B) There is no reason to restrict yourself to Lorentz transformations - they do not hold any special status within General Relativity.

Dauto (talk) 15:21, 19 February 2010 (UTC)

All of this fancy color shift stuff only happens from the point of view of the observer at the source of the light. From the point of view of the photon - nothing whatever happens - it just keeps on going. If space is infinite (we're not 100% sure of that) then it'll keep going forever completely unchanged. If space is finite then perhaps it 'wraps around' and comes back towards you from the opposite direction - but it's still completely unchanged. Photons can't "degrade" over time because they are travelling at the speed of light - and for them, the whole of eternity passes by in zero time. If they don't hit something (which seems highly implausible), then nothing can change because for them, time isn't advancing at all. SteveBaker (talk) 15:43, 18 February 2010 (UTC)

If by "never encounters anything" you mean your beam of light misses large objects like stars, galaxies and space rocks, its fate will likely be extinction in the interstellar medium. --Sean 16:19, 18 February 2010 (UTC)

Perhaps its information content will be absorbed into the Omega point. Graeme Bartlett (talk) 03:24, 19 February 2010 (UTC)

OK, I know I'm an ignoranimus about physics, but the OP stated "it never encounters anything". If you observe it, hasn't it encountered something, namely your eyeball? ←Baseball Bugs ^{What's up, Doc?} carrots→ 05:40, 19 February 2010 (UTC)

Not sure, but I suspect all photons are only produced with a matching absorbtion elsewhere.114.75.18.3 (talk) 06:48, 19 February 2010 (UTC)

Not sure what that means. In any case, the earlier discussion seemed to be confusing photons with galaxies. Obviously, galaxies can produce gazillions of photons, and those photons can appear red or blue depending on whether the galaxy is approaching or receding. But talking about photons that way implies that photons are ejecting other photons that would be visible without seeing the original photon. Maybe I'm wrong, but I don't think it works that way. ←Baseball Bugs ^{What's up, Doc?} carrots→ 06:54, 19 February 2010 (UTC)

How much sodium in 1g of Baking powder?

How much sodium is there in 1g of baking powder, after it has been used to make a cake for example? Thanks 89.243.151.96 (talk) 14:50, 18 February 2010 (UTC)

this suggests that there are 520mg per teaspoon. (In that brand, anyway.) I don't know how many teaspoons are in a gram of baking powder, though. Sorry. APL (talk) 15:29, 18 February 2010 (UTC)

It says on your picture that 1/8 teaspoon = 0.6 grams, so about 1/5 teaspoon per gram. --Sean 16:24, 18 February 2010 (UTC)

Most baking powdersoda is "sodium hydrogen carbonate" which is NaHCO₃ - so there is one atom of sodium, one hydrogen, one carbon and three oxygen. You have to figure out the atomic weight of each atom - add them up and then you know the ratio of sodium to the rest of the elements. Then you can figure out the fraction of a gram that is sodium. According to List of elements: Roughly, Hydrogen is 1, Carbon is 12, Oxygen is 16 and Sodium is 23. So one molecule of this compound has a total atomic weight of 23+1+12+3x16 = 84. So for every 84 grams of baking soda, 23 grams is sodium which means that about 27.4% of this stuff is sodium. There is therefore 0.274g of sodium in every gram of sodium hydrogen carbonate - if your brand of baking powder mixes that with some other 'stuff' (which is possible, for example to stop it clumping) then the answer will be different - check on the ingredients list on the packet. SteveBaker (talk) 15:35, 18 February 2010 (UTC)

Steve, that's baking soda. Baking powder is different. -- Flyguy649 ^talk 15:50, 18 February 2010 (UTC)

Baking powder says "Most commercially-available baking powders are made up of an alkaline component (typically baking soda), one or more acid salts, and an inert starch". So I guess we need to account for the other stuff too. SteveBaker (talk) 17:22, 18 February 2010 (UTC)

(EC)It would depend on the brand. In addition to the sodium bicarbonate (baking soda) and acid, like cream of tartar, baking powders contain various amounts of cornstarch. The acids used seem mostly not to contain sodium. So the answer is in how much baking soda is in baking powder. While this article gives some suggestions on how to make your own baking powder, it uses teaspoon measurements (not weight) for the ingredients. That article gives ratios ranging from 1 1/4:1 to 2:1 cream of tartar:baking soda. You should be able to figure out a rough answer by using the densities of each reagent. -- Flyguy649 ^talk 15:42, 18 February 2010 (UTC)

(edit conflict) Baking powder will certainly be mixed with other stuff; that's what makes it different from baking soda. Most baking powder is sodium hydrogen carbonate as well as an acid, like cream of tartar or monocalcium phosphate. They also typically contain an inert filler, like cornstarch. Look on the ingredient label, for both the serving size (hopefully they give a value in grams) and the amount of sodium per serving. Divide the second by the first to find grams sodium (or probably milligrams sodium) per gram powder. Buddy431 (talk) 15:49, 18 February 2010 (UTC)

This particular brand, for example, appears to contain 65 mg of sodium per 0.6 g serving, which is 108 mg sodium per gram baking powder. Buddy431 (talk) 15:53, 18 February 2010 (UTC)

The brand in my kitchen (Magic baking powder)has 45 mg of sodium per 0.6g (1/8 tsp) serving or 75 mg per gram of baking powder. This plus Buddy431's contribution above shows that there is a huge variation by brand. -- Flyguy649 ^talk 15:59, 18 February 2010 (UTC)

Yes and given all this, I think it's clear that unless the OP provides the precise brand and name of baking powder, we can't answer the question. It would surely be easier for the OP to just look on the label which is probably on his/her product anyway Nil Einne (talk) 16:38, 18 February 2010 (UTC)

File:refraction.jpg

what should be the minimum distance of the sun from the horizon so as to enable the observer to see it's image? —Preceding unsigned comment added by 117.201.65.74 (talk) 16:37, 18 February 2010 (UTC)

I converted your header into a proper subject header with the image as a link Nil Einne (talk) 16:38, 18 February 2010 (UTC)

Even only a part of the Sun need be above the sea horizon for its image to be visible. Cuddlyable3 (talk) 16:47, 19 February 2010 (UTC)

Monarch Butterflies

Where do Monarch butterflies go in the winter? —Preceding unsigned comment added by Dredfern (talk • contribs) 17:10, 18 February 2010 (UTC)

They migrate. "The most famous Lepidopteran migration is that of the Monarch butterfly which migrates from southern Canada to wintering sites in central Mexico. In late winter/early spring, the adult monarchs leave the Transvolcanic mountain range in Mexico for a more northern climate. Mating occurs and the females begin seeking out milkweed to lay their eggs, usually first in northern Mexico and southern Texas. The caterpillars hatch and develop into adults that move north, where more offspring can go as far as Central Canada until next migratory cycle." --Mr.98 (talk) 17:19, 18 February 2010 (UTC)

Addiction

Hi,

I'm very worried. In fact I think I'm addicted. It's a highly dangerous drug; an overdose can lead to death and the substance constitutes 98% of all cancer cells. So, should I be going to Waterholics Anonymous? —Preceding unsigned comment added by 86.150.210.228 (talk) 18:04, 18 February 2010 (UTC)

It's not as funny if you call it water. Try Dihydrogen monoxide - that sounds really scary. --Tango (talk) 18:06, 18 February 2010 (UTC)

Oh my God, you're not inhaling it, are you? AlexHOUSE (talk) 18:54, 18 February 2010 (UTC)

Think this is bad? I'm far more concerned about oxygen being a mutagen. Regards, --—Cyclonenim | Chat  21:39, 18 February 2010 (UTC)

Ah, but the antidote is red wine - have enough of that, and you won't be concerned at all! --Tango (talk) 23:05, 18 February 2010 (UTC)

I hate wine. I'm f**ked, but I guess I could just start on those vitamins... Regards, --—Cyclonenim | Chat  23:52, 18 February 2010 (UTC)

Bear in mind the kind you take intravenously is usually cut with salt. AlmostReadytoFly (talk) 09:57, 19 February 2010 (UTC)

waters not a drug —Preceding unsigned comment added by 67.246.254.35 (talk) 05:56, 19 February 2010 (UTC)

Fish reproduce in it (as per W.C. Fields). ←Baseball Bugs ^{What's up, Doc?} carrots→ 06:34, 19 February 2010 (UTC)

On the contrary, you could very broadly define water as a drug. It can alter bodily functions. If you're dehydrated, it's a drug which can relieve symptoms. Regards, --—Cyclonenim | Chat  11:28, 19 February 2010 (UTC)

Water intoxication is real. DMacks (talk) 11:38, 19 February 2010 (UTC)

Twin Cities

What is the most twin city to New Bedford, MA in Europe, geographically and climate-wise? Note I am not referring to sister cities. --Reticuli88 (talk) 18:49, 18 February 2010 (UTC)

The article about New Bedford does not give any info about its climate. I'm not sure if places having the same Hardiness zone would feel as if they had the same climate from a human point of view, since the seasonal daylight, summer temperatures, and rainfall may differ. What hardiness zone is it please? 92.24.96.55 (talk) 22:21, 18 February 2010 (UTC)

I think it is 6a. --Reticuli88 (talk) 22:51, 18 February 2010 (UTC)

Assuming New Bedford has a Hardiness Zone of 6 and a Heat Zone of 4, then the places listed in Europe with the same figures are Bratislava Slovakia, and Vienna Austria. They are both inland. Kaliningrad in Russia is more coastal, but it is only heat zone 2 and I think its latitude is higher so the seasonal daylight will be different. Do not know about the rainfall. 89.240.61.50 (talk) 23:51, 18 February 2010 (UTC)

Of course there is nothing close to a perfect match, but in terms of setting, population, and climate my choice would be La Rochelle, France. Looie496 (talk) 00:33, 19 February 2010 (UTC)

The climate would be much warmer in the winter than it would be in New Bedford, and probably cooler in summer. I assumed that the "geographical" similarity specified by the OP did not include population. 78.146.181.195 (talk) 00:49, 19 February 2010 (UTC)

Thanks everyone. Just wanted to know if I traveled to Europe today from New Bedford, MA, what city would seem like I never left MA - meaning the landscape (hills n such) and weather-wise. --Reticuli88 (talk) 13:20, 19 February 2010 (UTC)

WAG here, but maybe Sheffield? --TammyMoet (talk) 15:14, 19 February 2010 (UTC)

No, that would be one of the least similar places in all of Europe. 78.147.225.78 (talk) 20:36, 19 February 2010 (UTC)

If you are willing to accept somewhere with a warmer winter and a cooler summer then you have much more choice. With this in mind, if you want to limit yourself to Britain, then Nairn in Scotland would be a possibility, but with a smaller population. Inverness has a similar population. But even in Scotland, the urbanisation of the surrounding area is probably going to be much more than I expect it is around New Bedford. 78.147.225.78 (talk) 20:43, 19 February 2010 (UTC)

It's really unlikely that you'll find a place with similar weather in Europe. New Bedford has that vast continental landmass off to the west and only ocean to the east. Nowhere in Europe has that much continental mass behind it and such as there is tends to be to the east - not to the west. All of that results in very different climates in Europe and the USA. Also, the prevailing ocean currents are quite different. New Bedford gets the gulf stream bringing warm water up from the south. There isn't an equivalent thing in Europe. SteveBaker (talk) 01:01, 20 February 2010 (UTC)

Freezing Point Depression and Boiling Point Elevation

After reading one of the above posts I came across this picture. I understand what the unbroken segments of the lines are. But how can one understand the dashed segments of the lines? For example on the right hand side of where the black "solid" line crosses the dark blue "Liquid (pure solution)" line? •• Fly by Night (talk) 22:55, 18 February 2010 (UTC)

It appears that the dashed lines are merely the continuation of the trends for the chemical potential versus temperature. That is, if the solid didn't melt at its melting point, its chemical potential vs. temperature curve would follow the dashed black line. I guess that the dashed lines are just in there to make the intersections more clear. Buddy431 (talk) 04:49, 19 February 2010 (UTC)

February 19

Altered taste buds after toothbrushing

Why does milk and orange juice taste so terrible after brushing? --70.167.58.6 (talk) 02:56, 19 February 2010 (UTC)

The Sodium lauryl sulfate in the toothpaste supresses the "sweetness" sensors in your tongue and decomposes phospholipids which normally inhibit your "sour" tastebuds. Net result, the usually sweet and subtly tart orange flavor becomes totally unsweet and super-sour. I don't know why milk would taste bad - I wasn't really aware that it did...but if you're right then it's probably the same kind of reason. SteveBaker (talk) 03:08, 19 February 2010 (UTC)

You can buy toothpaste without the Sodium laureth sulfate foaming agent. EDIT, Sodium lauryl sulfate is different to Sodium laureth sulfate and probably not found in many toothpastes... 188.221.55.165 (talk) 13:38, 19 February 2010 (UTC)

That makes me wonder... on a similar topic... Is there a toothpaste that enhances taste of "healthy" food? For example, they could throw some miracle fruit juice in the toothpaste. -- kainaw™ 04:21, 19 February 2010 (UTC)

You're supposed to brush after you eat, not vice-versa. APL (talk) 05:51, 19 February 2010 (UTC)

That supposes the purpose is to remove food particles. Ew. I brush before breakfast to remove the layer of plaque that builds up overnight, so the sugars in my breakfast have nothing to stick to. If I were brushing after eating, I would wait half an hour to allow my mouth pH to return to normal, as otherwise the teeth are softer and you can end up (over cumulative brushings over the course the years) thinning them, gradually brushing off the hard layer. Since I don't have half an hour to spare after breakfast, and the thought of brushing bits of food out in the froth makes me gag, I brush before eating. 86.182.38.255 (talk) 15:56, 19 February 2010 (UTC)

Hmm... That's pretty complicated. I had no idea that by skipping breakfast I was saving myself so much mental effort. APL (talk) 18:17, 19 February 2010 (UTC)

We're on the Science desk, and you think that's complicated? Maybe I should have just said "You're supposed to brush before you eat, not vice-versa." as if I had access to some ultimate truth, then left people to suppose that it is only cultural with no advantages or disadvantages either way. 86.176.185.157 (talk) 12:40, 20 February 2010 (UTC)

Toothpaste that enhances the taste of "healthy" food is called mayonnaise. --Dr Dima (talk) 10:06, 19 February 2010 (UTC)

Whether teeth are brushed before or after breakfast depends primarily on a cultural difference. And not eating breakfast simply makes one fat. ~AH1^(TCU) 00:01, 20 February 2010 (UTC)

In concert with Steve's response above, orange juice contains sugars as well as naringin, a bitter component of the peel and other parts of the orange. After sodium lauryl sulfate (essentially a detergent) destroys one's sweet-detecting taste cells, the only taste of the orange juice that can be detected is the bitter naringin. DRosenbach ^{(Talk | Contribs)} 13:56, 19 February 2010 (UTC)

"destroys" is a rather strong term for what this detergent does. It doesn't damage the cells - it merely inhibits them in some way. If it destroyed them it would be days to weeks before you'd get your sweet taste sense back rather than tens of minutes. SteveBaker (talk) 00:57, 20 February 2010 (UTC)

Integrating Partition Functions

When computing the partition function or doing other such calculations in statistical thermodynamics, one needs to sum (integrate) over all the possible microstates. How do you determine the appropriate variable over which to do the integration? An example to clarify: if one of the degrees of freedom of your system is a rotation around a molecule's bond, one possibility is to integrate over the dihedral angle. However, that degree of freedom can be quantified by any number of other equivalent formulations (e.g. something based on, say, the dot-product of the normal of the plane containing atoms A-B-C and that containing B-C-D). How can we tell what's the appropriate variable to use in the integration, and what is the property of that measure that makes it the appropriate one to use? -- 174.21.247.23 (talk) 04:20, 19 February 2010 (UTC)

For the outcome, it doesn't matter which representation you choose; all of them are quevalent by definition. Of course, choosing a different representation can make the integral easier to solve. But there no general rules which one to choose. --baszoetekouw (talk) 10:05, 19 February 2010 (UTC)

I believe it does matter which one you choose. I'll give an example: You have two different way to parametrize a single degree of freedom, x and α, related by the expression α = x², each of which varies between 0 and 1. Say your energy function is E = (1 - x²)/β = (1 - α)/β. The two different formulations for the partition function give

$Z(x)=\int _{0}^{1}\!e^{-\beta E(x)}\,dx=\int _{0}^{1}\!e^{-(1-x^{2})}\,dx\approx 0.538,$

$Z(\alpha )=\int _{0}^{1}\!e^{-\beta E(\alpha )}\,d\alpha =\int _{0}^{1}\!e^{-(1-\alpha )}\,d\alpha \approx 0.632,$

So in this case (and I believe most other cases, especially when the two are not linearly related) the two formulations do not give equivalent results. My question was, how do I know which formulation is the correct one to use? That is, which is the "natural" variable over which to do the integration, and how do we know which one it is? -- 174.21.247.23 (talk) 16:41, 19 February 2010 (UTC)

In general, the correct way of looking at the problem is actually:

$Z(x)=\int \!e^{-\beta E(x)}\rho (x)\,dx$

Where ρ(x) is the density of states in the neighborhood of x. For many practical problems, we tend to engineer the variable of integration such that ρ(x) = 1. In a sense that gives you a preferred choice for the variable of integration, but it is not a required choice. In particular, one can change as in a regular integration be realizing that ${\rho (x) \over \rho (\alpha )}={\partial \alpha \over \partial x}$.

By definition, each set of allowed quantum numbers will contribute exactly one term to the partition function sum. In general, this means one can find the ρ(x) = 1 formulation by starting with an explicit sum (or often a multiple sum, with one sum for each quantum number), and then when one extends it into the continuum limit the integrand for ρ(x) = 1 will have the same form as your summand. I'd suggest that a large part of the problem you are having in deciding how to do the integration is that you probably haven't figured out how your system is quantized. Being able to enumerate the quantum states is a necessary precondition to writing out a partition function. Dragons flight (talk) 18:12, 19 February 2010 (UTC)

How does one go about the quantum to classical conversion for complex systems such as large molecules? Going back to my original example of a rotation around a bond, is there a straight-forward way of determining how ρ(x) is constructed? "Enumerating quantum states" is all well and good for something like ethane, but for larger systems like erythromycin (or erythropoietin) it begins to break down. -- 174.21.247.23 (talk) 04:48, 20 February 2010 (UTC)

transformers

i was reading about transformers and came to know that it can easily defy ohm's law ie "V is directly proportional to I". i have a QUESTION what will happen if a appliances is rated to be used at 220V, and let us assume it needs 10A-- is given 220V and 5A? will it work perfectly or just slowly? since no appliance is rated abot current i am unable to conclude any thing. { we got a source of 110V and 10A, using a step up transformer we get 220V and 5A } <<<a request please dont start asking ur questions in this page, many a times it had happened to me, my question is interrupted by someone else>>>--Myownid420 (talk) 07:40, 19 February 2010 (UTC)

You'll blow a fuse. The current-rating on an appliance says how much current it takes at the given voltage. That is, if you push with a certain force (voltage), that's how much/rapidly the electricity flows (current) through its inner workings (consider Ohm's Law for the fixed resistance of the appliance). Your circuit is pushing with a certain force, which will cause that amount of current to flow. But your circuit is limited to supplying less than that. So either there is not enough energy in the appliance for it to do [whatever], and the failure will depend on how it uses the energy, or else your circuit will try to keep up with the flow the appliance is using, and overheat. Current output is a maximum-available, not a constant amount--as you draw more on the transformer secondary, the primary draws more from the mains. If you do not connect the secondary to anything, the primary is drawing nearly zero, not "the rated supply current". DMacks (talk) 08:08, 19 February 2010 (UTC)

Usually the voltage V and power P in watts are specified for a mains appliance. Given these two it is unnecessary to specify the current I in amps because I=P/V. The supply is just a voltage, such as 220V or 110V. The current depends (mostly) on the resistance R of the appliance. Here Ohm's law I=V/R is useful. With one proviso, any appliance rated for 220V can be connected to any 220V supply and any appliance rated for 110V can be connected to any 110V supply. The proviso is that the supply is able to deliver the current the appliance demands because if not, something in the supply will burn up, hopefully just a fuse. Your step-up transformer will work if it has high enough power rating (watts) for the appliance. Thank you for your question which was clearly written. Sometimes we need to ask questions to help us give better answers. Cuddlyable3 (talk) 16:21, 19 February 2010 (UTC)

Transformers are generally given a primary and secondary voltage rating and an amp or voltampere rating on the secondary side. They have some internal impedance to the flow of electricity,so if no current flows to the load, the secondary voltage may be higher than nominal. If more than the specified current is drawn out, the secondary voltage may drop lower than specified. How much current is drawn out of the secondary is up to the connected load, not to the transformer. It is not a pump of electricity. Under a very high load or a dead short, the current flow would be limited mostly by the transformer impedance (and to a slight extent by the impedance of the source feeding the primary) and the transformer might overheat and fail if a primary or secondary fuse or breaker did not blow. The primary fusing often is just to protect against a short in the transformer, and would let the transformer continue feeding a short on the secondary for a long time. I have seen 12kv primary, 480v secondary transformers continue to feed an arcing short on the secondary for over a half hour, providing enough energy to incinerate a metal enclosed switchgear. Edison (talk) 03:18, 20 February 2010 (UTC)

washingg labware

how is labware like beakers washed when it had strong acids like 100 % hydrofluoric acid —Preceding unsigned comment added by 67.246.254.35 (talk) 11:14, 19 February 2010 (UTC)

also eye dropers —Preceding unsigned comment added by 67.246.254.35 (talk) 11:20, 19 February 2010 (UTC)

A glass beaker would not contain 100% hydrofluoric acid for at least two reasons. DMacks (talk) 11:36, 19 February 2010 (UTC)

At least, not for long! One of my lecturers used a dilute HF solution when he was washing out all his glassware as an undergrad back in the day just to get the stubborn marks off. I don't think you could get away with that now. Also, for 67: I can't see why you'd use any special procedures; several water rinses then a squirt of acetone would probably do it. Brammers (talk) 14:24, 19 February 2010 (UTC) (Edited 14:26, 19 February 2010 (UTC))

No, first you have to safely neutralize the remaining HF. HF is only handled in fume hoods nowadays but you would wash it 3 times with dilute basic solution and store that in a waste acid container. Then you would wash with polar and nonpolar solvents and scrubbrush depending on what you were cleaning and store that rinsate in a organic (or solvent) waste container. Then you would wash with water (which rinsate may need to be stored in an aqueous waste container). Finally (at least in my college research lab) a 24-hour bath in dilute acid, followed by a 24-hour bath in dilute base, then overnight in a drying oven and you're done. Unless you are doing anayltical chemistry where you may then need to wash it three times in triple distilled dionized water before drying it. (Ah, the memories of washing dishes. The only time I have ever needed to use a fire extinguisher.) 75.41.110.200 (talk) 15:26, 19 February 2010 (UTC)

If you have an acid-waste container, then put your acid waste in it and let the waste-collection folks handle that. Few quick rinses with then water, and you're done. Well you were done long ago, because the HF (which cannot be made 100% in a beaker) would have dissolved the glass away. If poured out promptly, the HF would have merely etched the glass to become fluorosilicic acid, one of the fluorinating agents used in public water supplies. Repeated acid and base washes are waaaay overkill unless you actually need something that really clean. And anyway unless you use deionized water you're still going to bake out a bunch of ions and get an unpredictably-reactive glass surface, but for many purposes, it doesn't matter--triple-water-rinse and it's clean enough for non-analytical/non-biochemical purposes. Organic chemists just use a squirt of acetone and say "good enough":) A totally impossible scenario without detail/context, no way to know "how clean" the glass needs to be. DMacks (talk) 18:38, 19 February 2010 (UTC)

Ah right, thanks for the insight. The organic labs are the only ones where we have to wash our own glassware, so I'd assumed the acetone squirt was standard practice. Brammers (talk) 01:35, 20 February 2010 (UTC)

I loved lab sinks with a ring of Litmus paper around the drain. Edison (talk) 03:20, 20 February 2010 (UTC)

Apollo Missions

I think I have a decent grasp of most of the stages involved in the Apollo missions. However what I don't get is how NASA was so confident they could dock the orbiter and the lander AFTER the surface mission. To properly dock two untested components (how could they really test docking in lunar orbit?) seems like a major challenge. How did they know they wouldn't be stuck with two vehicles in non-intersecting orbits? TheFutureAwaits (talk) 11:59, 19 February 2010 (UTC)

Well, it's mostly just "docking in orbit" -- "docking in lunar orbit" adds no particular degree of difficulty. NASA had already done considerable work in Earth orbit to verify rendezvous launches (see Gemini 6 and Gemini 7) as well as Apollo CM/LM docking tests (see Apollo 9 and Apollo 10, the latter conducting lunar orbit operations). So, the vehicles weren't untested, and they'd verified that they could do the math to avoid non-intersecting orbits. — Lomn 12:32, 19 February 2010 (UTC)

By the time of Apollo 11, it was fully tested because Apollo 10 had done exactly the same thing, just without having actually set down on the moon inbetween. I guess Apollo 10 were taking a bit of a risk, but the Apollo programme accepted a significantly higher level of risk than modern space programmes. --Tango (talk) 12:34, 19 February 2010 (UTC)

Apollo 9 tested the lunar module in Earth orbit, flying more than 100 miles from the command module before separating from the descent stage and returning to dock. I assume that they limited the delta-V so that had the lunar module failed at any point, the command module could have caught up with it for docking. So, while these missions did take big steps, it was not done all in a single step. 58.147.58.28 (talk) 13:47, 19 February 2010 (UTC)

I have always assumed that NASA had planned for the contingency of the loss of the descent crew, either due to a crash of the LEM during descent or a failure of the ascent module, but I've never heard it specifically said that the command module pilot would have been able to execute the return to Earth single handed. (I suppose that it was done in Shane Johnson's Christian science fiction novel Ice, but I don't recall him discussing the logistics of the return.) 58.147.58.28 (talk) 13:47, 19 February 2010 (UTC)

Yes, the CM pilot could have returned home on his own. I can't find a reference for that at the moment, but I do remember reading it. I don't know quite how it would work, perhaps ground control would do some of the work remotely. --Tango (talk) 14:24, 19 February 2010 (UTC)

Considering that they had a planned presidential speech in case Neil Armstrong and Edwin Aldrin died [17], I expect they would have had a detailed procedure to bring Collins back. 75.41.110.200 (talk) 15:12, 19 February 2010 (UTC)

Cause of Menopause

Does meno pause happen because of running out of eggs in the avaries, or is there something else that causes it. In that case. are there eggs left over? —Preceding unsigned comment added by 79.76.254.35 (talk) 13:53, 19 February 2010 (UTC)

There are millions of eggs, so that's not the problem. This seems to indicate that you are correct (check out the last paragraph)...but biology class has always taught that this is not true. It's a reflection of lowered hormone production, specifically estrogen and progesterone. You can check out the article on menopause for more information. DRosenbach ^{(Talk | Contribs)} 13:58, 19 February 2010 (UTC)

Running out of eggs in aviaries usually results in a lack of birds! --TammyMoet (talk) 15:12, 19 February 2010 (UTC)

Simply put. The eggs in the women cycle not only contains the gonades, but they also end up producing hormones, (which explains the hormonal variation, most of the time a single at a time, the same one which migrate waiting to be fecunded). That's controled by the putiary gland. During menopause there are no eggs left. That's quite different than the production of androgenes by the testicules and that's why male adropause is more gradual. -RobertMel (talk) 17:14, 19 February 2010 (UTC)

This question is tantamount to asking why people age or die. It's a long story! Vranak (talk) 17:31, 19 February 2010 (UTC)

No actualy, it is not. Menopause is due to no eggs left to produce female hormones and the surrenals conversion of DHEA does not suffice to replace that loss. It's really that simple. -RobertMel (talk) 17:35, 19 February 2010 (UTC)

Symptoms of a higher-level process. Vranak (talk) 19:07, 19 February 2010 (UTC)

Menopause simply means the cessation of menstruation as there is no eggs left which will be answering to LH and FSH. It's really not that long as a story, really. Menopause can be induced by simply removing the ovaries, because you get rid of the eggs all at once. What it means to be old? The question is much more complex. -RobertMel (talk) 19:31, 19 February 2010 (UTC)

~Shakes head~ I think we are at loggerheads here. Vranak (talk) 04:08, 20 February 2010 (UTC)

Im still not clear of the answer to my question. Can someone simplify the answers? —Preceding unsigned comment added by 79.76.244.151 (talk) 10:56, 20 February 2010 (UTC)

Are kale stems edible?

All my kale was infested by Whitefly, they only spared the stems. Are they edible, and would they need special treatment before eating? 95.115.163.171 (talk) 14:17, 19 February 2010 (UTC)

I'm pretty sure I've eaten kale stems. It's just a variety of cabbage. --Tango (talk) 14:26, 19 February 2010 (UTC)

Yes: raw or boiled. Bit woody either way if the plants are too old. A related question if anyone knows is whether Vitamin K is uniformed distributed between stalk and leaves for plants such as this, or broccoli. Anyone know? I happen to be very fond of the crudity made from the centre of a broccoli stalk and have to watch Vitamin K intake. --BozMo talk 18:14, 19 February 2010 (UTC)

Sorry to be picky, but I think it's crudité 86.4.186.107 (talk) 19:12, 19 February 2010 (UTC)

Crudity means crudeness. --Tango (talk) 20:59, 19 February 2010 (UTC)

If the stem is edible and spared by pests, is there any cultivar with thick and not-so-woody stems? 95.115.163.171 (talk) 22:46, 19 February 2010 (UTC)

H₂O a covalent compound

why ionic compounds dissolve in covalent compound water(H₂O)? how does a covalent compound sugar(C₆H₁₂O₆)dissolves in water and not a oil?is it necessary for all ionic compounds to be soluble in water. —Preceding unsigned comment added by Myownid420 (talk • contribs) 16:27, 19 February 2010 (UTC)

The bond in H₂O is a polar covalent bond which means it can be considered partially ionic. Read ionic bond#Ionic versus covalent bonds for a brief explanation. It is the polarity of the compound that matters when figuring out whether it is water soluble or not. Dauto (talk) 16:41, 19 February 2010 (UTC)

Rings around Earth

This video was very interesting however I wonder if earth would be different or possible for life to happen on earth if it had this. Does it matter what the rings would be made of or the size? --Reticuli88 (talk) 16:54, 19 February 2010 (UTC)

Not an answer but a further question: how do we go about building those way cool rings? Maybe even temporary ones, say, from water ice that will deorbit in a few decades -- how many kg of water? Launch cost in USD? (Yeah yeah, astronomers will complain about light pollution; we'll just ignore you.) 88.112.56.9 (talk) 17:21, 19 February 2010 (UTC)

To answer the cost question, a general estimate is that it costs $10,000/lb (roughly $20,000/kg) to get something into LEO. It would likely take many, many thousands or millions of tons of material in order to crate planetary rings. The more spectacular, the more material you probably need. So I estimate cost on a bare minimum guess of $2 trillion for a measly 100,000 tons of material. Keep in mind that is only 100,000 cubic meters of ice (approximately) so it would be spread pretty thin. Also, the people who have satellites might not like you if you did this. Googlemeister (talk) 17:40, 19 February 2010 (UTC)

How will the water de-orbit? --Reticuli88 (talk) 19:09, 19 February 2010 (UTC)

There's still plenty of atmospheric drag in low Earth orbit, and ice chunks have no fuel to counteract that. — Lomn 20:01, 19 February 2010 (UTC)

To answer the original question. The rings would have no ill effect whatsoever for life on earth. Dauto (talk) 20:51, 19 February 2010 (UTC)

I don't know about that - the shadow the rings cast across the planet could have some effect. It wouldn't prevent life from forming, but it might be a little different (in the appropriate region, anyway). --Tango (talk) 20:57, 19 February 2010 (UTC)

The amount of light blocked by the rings is negligible. Dauto (talk) 21:42, 19 February 2010 (UTC)

OK, our rings of saturn page says 5 to 12% gets blocked so not completely negligible but too small to cause any direct ill effect. Dauto (talk) 22:26, 19 February 2010 (UTC)

That's just the C ring (and is unreferenced), which is described as "faint". Presumably the darker rings block more. --Tango (talk) 22:44, 19 February 2010 (UTC)

Dauto, your claims in this thread are really sloppy. Can you provide references for your extravagant claims that there would be "no ill effect whatsoever" and "too small to cause any direct ill effect"? You're aware, aren't you, about possible tipping points, and that any weather system is so chaotic that you can't possibly predict the consequences of changes? 63.164.47.229 (talk) 23:12, 19 February 2010 (UTC)

Yeah, but who said anything about no changes? I said there would be no ill effect. Earth might become cooler by several degrees due to the rings and life would adapt the same it adapted to the last several glacial maxima. Note that the question is about whether life on earth would be possible at all. Dauto (talk) 23:40, 19 February 2010 (UTC)

That life would eventually adapt is a given - but if the rings formed quickly enough then there might not be time for that. Assuming Saturn's rings for a model (not necessarily a valid thing - but let's go with it), the rings block sunlight for half of the year and enhance it for the other half. That results in hotter summers and cooler winters. How much that blocking might be is tough to guess - because we don't have a solid description of how thick or how wide these rings are. Judging by the density of the shadow cast by the Saturnian ring system, it's certainly not negligable. We could certainly imagine more pronounced weather at the edges of the ring shadow where the temperature contrasts are strongest. The complexity of the changes caused by such rings are hard to unravel. So I'm sure Dauto's statement is too strong. This is a "Don't know" kind of a question.

It's worth mentioning that according to the Giant impact hypothesis the Earth did once have rings - shortly after the Mars-sized object sometimes known as "Theia" smacked into the young Earth there would have been some pretty impressive rings - much of which eventually formed the Moon - with the remainder falling back to Earth eventually. SteveBaker (talk) 00:50, 20 February 2010 (UTC)

I stand by what I said. I few rings around the earth wouldn't prevent life on earth. Life survived more extreme events in the past such as the K-T event. Dauto (talk) 01:11, 20 February 2010 (UTC)

But you went way further than that, and claimed there would be no ill effect whatsoever, which you could not possibly predict or know for sure. Being a little less sure of yourself in such answers would suit you. 63.164.47.229 (talk) 01:50, 20 February 2010 (UTC)

Rings in orbit really wouldn't hurt life on earth. They might make a few things a little different but still suitable for life. Hence no ill effect. Dauto (talk) 02:38, 20 February 2010 (UTC)

Butterfly effect. Too chaotic to predict what changes would occur, good or ill. Ks0stm ^(T•C•G) 03:08, 20 February 2010 (UTC)

The butterfly effect doesn't make it impossible to make predictions. For instance, I predict that six months from now it will be warmer in New York City than it is today. Dauto (talk) 03:17, 20 February 2010 (UTC)

Always radioactive?

Are all chemical compounds of radioactive chemical elements radioactive? --88.76.18.70 (talk) 16:56, 19 February 2010 (UTC)

Simply put, chemical compounds concerns the electrons, radioactivity concerns the nucleus of the atom. So no matter the lenght of the chemical compound, as long as it contains radioactive elements, it is radioactive. -RobertMel (talk) 17:06, 19 February 2010 (UTC)

Are there any radioactive chemical compounds which don't contain any radioactive atoms? --88.76.18.70 (talk) 18:08, 19 February 2010 (UTC)

No. -- Flyguy649 ^talk 18:10, 19 February 2010 (UTC)

I think the variations on what you are looking for in a single type of atom are called isotopes. ~AH1^(TCU) 23:41, 19 February 2010 (UTC)