Wikipedia:Reference desk/Archives/Science/2010 April 30

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April 30

Rust metal quickly.

I'm trying to make a chess set of nuts and bolts, and one side needs to be rusted. How would you rust steel quickly? There is a zinc coating that needs to be removed. I'm thinking of using a strong acid or base to remove it, and I'd prefer not go out and buy it, so are there any good household chemicals that react well with zinc? I can leave it in a safe area, so toxic gases shouldn't be much of a problem. As for rusting the steel, I know that salt water works, but are there any other factors I can manipulate to make it rust faster? Also, should I spritz the solution on or soak it in a bath? Cost is the main worry here, time isn't as important. KyuubiSeal (talk) 00:14, 30 April 2010 (UTC)

If you have some lye, it is a fairly strong base (NaOH) assuming it hasn't been diluted too much. If you have some (applied and pure) chemistry knowledge, you could try battery acid, but that is kind of very dangerous so don't mess with it unless you know what you're doing! The fastest way to oxidize something is to burn it, though the temperatures needed to burn steel probably are outside your price range. 76.229.165.96 (talk) 00:28, 30 April 2010 (UTC)

Dissolve some baking soda in water. Find a power supply (6-18V, do not go higher electrocution hazard). Attach all of your components to the positive electrode of the power supply. Use either stainless steel clips that would not be dissolved, or use junky ones. Attach any piece of metal to the negative electrode. Turn on the power supply. Hydrogen will be emmitted at the negative electrode. If the zinc plating is thick, you will see a white film coming off the positive electrode. After that, ferrous hydroxide (green rust) will be formed. If you let it sit it will be oxidized by air to ferric oxide (brown rust). Let it go for about 10-120 minutes (the higher the voltage, the shorter the time) and take it out. It will be rough and unshiny. If you keep it moist, it should rust in a couple of days. If you want it faster, you can place it in sodium hypochlorite solution to turn it brown. Keep it in there for a day. Remove it and it should be nice and rusty. --Chemicalinterest (talk) 00:30, 30 April 2010 (UTC)

BTW, battery acid isn't very dangerous. If you get some on your skin, you will feel a burning sensation. Quickly pour baking soda on it and wash it thoroughly in water. NaOH is not as dangerous unless it is concentrated (more than 10 molar). It won't dissolve zinc, though. --Chemicalinterest (talk) 00:31, 30 April 2010 (UTC)

So after it forms green rust, does it need to be in contact with air, or can it be left in a bucket of water? KyuubiSeal (talk) 00:39, 30 April 2010 (UTC)

Either. It just needs water vapor, which is present in small quantities in the air, and oxygen, which is present in small quantities in the water, to rust. You could leave it in salt water (probably the fastest), under moist cloths, or in humid air. --Chemicalinterest (talk) 00:47, 30 April 2010 (UTC)

I wonder if you could set up a basic Cathodic protection system and make the parts you want to rust into Sacrificial anodes? The article says they use zinc for sacrificial anodes on steel pipes.. No idea off the top of my head how you'd set it up, you'd need to work out how to attach the components and what kind of current and how to run it, but it might be a fun project if you are into that kind of thing. Vespine (talk) 00:59, 30 April 2010 (UTC)

Yes you could but it wouldn't rust much faster than ordinary corrosion. Ordinary iron contains areas of more stress, which are eaten away and function as anode, and areas of less stress, where oxygen is reduced and functions as cathode. --Chemicalinterest (talk) 11:17, 30 April 2010 (UTC)

Would there be any effects on the glue used to hold the pieces together? KyuubiSeal (talk) 01:49, 30 April 2010 (UTC)

If the glue is made to bond to metal, it might behave differently with the metal oxide. Just experiment on a few before making your set. --Chemicalinterest (talk) 11:17, 30 April 2010 (UTC)

I don't know about the zinc coating, but bleach is very effective at rusting iron and steel. Dragons flight (talk) 01:59, 30 April 2010 (UTC)

Bleach does sounds like a good idea, it is a strong oxidizer, such as Hydrogen peroxide. As for glue, you need a good electrical connection between the components so glue probably isn't the best solution, maybe clamping them between two pieces of steel would work, but the contact surfaces would probably not rust.. Thinking about it, might be more complicated then it is worth, I'd try the bleach idea first. ;) Vespine (talk) 02:17, 30 April 2010 (UTC)

3% hydrogen peroxide rusts too slow. Bleach, as I scientifically called it sodium hypochlorite, does rust iron (and zinc). --Chemicalinterest (talk) 11:17, 30 April 2010 (UTC)

If you want it to rust fast, spray it with water, then dry it on low heat in an oven (as close to, but under 212f). It'll fully rust in no time. I learned that the hard way when foolishly thinking I should quickly dry water from a brake rotor by heating it. To remove zinc I would just sand it. The hotter the metal the faster it rusts. Don't soak it in water - it needs lots of air. Just spray water on it. Ariel. (talk) 06:02, 30 April 2010 (UTC)

Another idea for you: Zinc likes to react with sulfur. Buy some sulfur at a [compounding] drug store (or online), sulfur is pretty cheap. Shake some sulfur all over the metal parts, add ... Actually I'm not sure what the next step would be. I would experiment with heating it, with and without water, and trying to ignite it with a blowtorch. I'm also not sure if the result will stick to the underlying metal. But it should be cheap to experiment. Ariel. (talk) 06:13, 30 April 2010 (UTC)

I tried it, but it didn't affect it. The iron tends to carry heat away too fast. --Chemicalinterest (talk) 11:17, 30 April 2010 (UTC)

right|thumb|Your call Death -what colour!

An easy to obtain acid that will dissolve off zinc and help it to go rusty, is commonly sold in stores as 'Spirit of Salt' better known as hydrochloric acid and used domestically for cleaning drains. When you are ready to make the pieces rusty, use a 10% solution of hydrochloric to remove your 'invisible' but greasy finger prints! That way, you will achieve a more even oxide coat in less time. As mentioned above: a moist warm atmosphere is excellent for rust formation. Be advised though: This form of natural rust is very loose. It will come of as soon as you start playing with them and may make the board feel gritty(you are not the first to think of rusty chest pieces). The acid in sweat and friction will make the metal edges shiny again. It might be better to oxidise the surface to form a Iron(II,III) oxide. This is much more durable. The colour can be adjusted from a grey to a nice black , through brown to a somewhat reddish tone. This coating is often used as a durable finish on military equipment. A professional sculpture would probably choose to send it away and get it done by a sub-contractor. As an example, here is one such firm in Canada.[1]. Another option, very attractive, (only not quite so durable) is Bluing which can be toned all the way down to black. Often used on guns, in order to avoid signalling to the enemy on sunny days “Hay, I 'm over here - hiding in the bushes!”. The bluing solution can be bought from your local gun emporium, for you to do at home. These sort of coating will make it a more practical chess set. After all, you never know who may come to be your opponent !--Aspro (talk) 09:06, 30 April 2010 (UTC)

Yes, if you heat it until it is red-hot, it will form iron(II,III) oxide. --Chemicalinterest (talk) 11:17, 30 April 2010 (UTC)

I'm testing the baking soda bath with a few spare parts right now. I didn't have alligator clips, so I wrapped the copper wire around the screw. Hope the exposed copper doesn't affect it. Hydrogen is bubbling off the negative electrode, and the zinc coating disappeared, so it seems like it's working. Thank you! EDIT: It worked great! KyuubiSeal (talk) 22:40, 30 April 2010 (UTC) If the copper is underwater, blue green copper(II) hydroxide will be formed. If not, it will not have any affect. Do not run it too long or you will completely dissolve the entire screw. --Chemicalinterest (talk) 12:02, 3 May 2010 (UTC)

noble barrier

What is meant by a "noble" barrier, as in a coating to protect iron?--115.178.29.142 (talk) 00:51, 30 April 2010 (UTC)

"Unreactive" or "inert" (like the noble-gas elements). DMacks (talk) 00:57, 30 April 2010 (UTC)

There is a patent covering the idea here. Perhaps that would be of some help? SteveBaker (talk) 00:58, 30 April 2010 (UTC)

It is typically an unreactive oxide coating which prevents further corrosion, such as the one aluminum forms. Another term is passivation. --Chemicalinterest (talk) 01:00, 30 April 2010 (UTC)

Noble gases (like argon) by definition cannot form coatings on metals. Noble metals (like gold or platinum) could be used, though, but they would be prohibitively expensive (although gold coatings are sometimes used on electronic components). FWiW 76.103.104.108 (talk) 07:54, 30 April 2010 (UTC)

Passivation layer may be of interest. Nimur (talk) 15:25, 30 April 2010 (UTC)

Solar sail

How fast would a spaceship propelled by a solar sail go? --75.33.219.230 (talk) 01:34, 30 April 2010 (UTC)

If the sail was powered by a laser, in theory, it could come close to the speed of light. However, to do this, A sail several kilometers across and about 0.001 mm thick would be needed to push a probe the size of the lunar capsule, and micrometeorites would be a major problem. I don't think it's possible. --The High Fin Sperm Whale 02:23, 30 April 2010 (UTC)

Our solar sail article is pertinent, with the first proposal having been to use batteries of Earthbound lasers powered at gigawatt strength for years or decades. I must mention, as always, The Mote in God's Eye as a science fiction novel in which this occurs. Comet Tuttle (talk) 03:13, 30 April 2010 (UTC)

Spaceship propulsion

Would this method for propelling a spaceship work?

1. Uranium is fissioned, releasing energy to power the spaceship.
2. At the same time, an equal amount of anti-uranium is fissioned in a separate chamber, also releasing energy.
3. The two fission chambers are separated by a barrier with holes slightly smaller than a uranium atom. The uranium and anti-uranium atoms can't pass through, but the fission products can, and they annihilate with one another, releasing even more energy to power the spaceship.

In step 3, the same amount of energy is released as if that mass of antimatter had been annihilated immediately, but the preceding fission releases more energy. --75.33.219.230 (talk) 01:34, 30 April 2010 (UTC)

Energy is a conserved quantity. You can't convert a given amount of matter into energy in two different ways and get different amounts of energy. The amount of energy you get by fission will be lost when you collide the fission products, in comparison to colliding the original uranium and anti-uranium. Looie496 (talk) 01:49, 30 April 2010 (UTC)

(ec) I'll leave aside the obvious technical hurdles which prevent such an engine being built, and address what I presume is your central question — do you get more energy out of fissioning the uranium nuclei and then annihilating their fission products than you would from pre-fission annihilation? Instead of giving you the answer outright, I'll ask you a question of my own — Are the products of nuclear fission equal in mass to the original uranium nuclei? Answer that, and you'll be able to answer your question. TenOfAllTrades(talk) 01:54, 30 April 2010 (UTC)

(also ec seems we were on the same page) I'm not a physicist but I suspect that the energy you gain in your fission reaction (and hence the mass you lose) would be the same as the energy you lose by reducing the amount of mass in your matter/anti-matter annihilation. In other words, skip the fission and just annihilate the whole anti-uranium. That's just a guess ;) Vespine (talk) 01:55, 30 April 2010 (UTC)

There are two other points missed by the OP besides the obvious conservation of energy

• Uranium atoms are not smaller than their fission products
• The anti-uranium atoms would annihilate with the container walls.

Dauto (talk) 02:34, 30 April 2010 (UTC)

Ignoring all of the OTHER problems with this scenario, your second problem can be ameliorated with either magnetic or electric fields. For example, if the anti-uranium was ionized, electrically charged walls could repel the anti-uranium atoms... --Jayron32 02:46, 30 April 2010 (UTC)

U-235 + n -> U-236 -> Kr-92 + Ba-141 + 3n

Both sides have a total mass of 236 AMU, so where's the mass loss to correspond with the energy released? --75.33.219.230 (talk) 12:01, 30 April 2010 (UTC)

The AMU is not a sufficiently precise measure of mass here - see binding energy. Gandalf61 (talk) 13:58, 30 April 2010 (UTC)

As gandalf pointed out, you need to be more precise than that. For instance, the mass of Uranium-235 is M²³⁵U=235.0439299 u. Dauto (talk) 14:16, 30 April 2010 (UTC)

OK, here are the values you will need

• M²³⁵U=235.0439299 u
• M¹n=1.0086649156 u
• M⁹²Kr=91.926156 u
• M¹⁴¹Ba=140.914411 u

So, the masses of the left side of your equation add to 236.0526 u and the right side adds to 235.8666 u. Not exactly the same thing.

Dauto (talk) 14:31, 30 April 2010 (UTC)

Using E=mc², we can rearrange the equation to give us an energy-mass equivalence of 9.0 × 10¹³ J/g. Combine that with the value of 0.186 g/mole converted to energy (see above) we get a value of 1.7 x 10¹³ J/mol for the fission of Uranium. In scientific circles, that's what we call a "shitload of energy". --Jayron32 00:39, 1 May 2010 (UTC)

Or put in very basic terms, it's about 200 MeV per atom per fission. Which is enough energy to disturb, say, a bit of dust. Which is pretty impressive for a single atom—I did the mass comparison at some point, and it's along the lines of an ant kicking an ocean liner and having it tip a bit. --Mr.98 (talk) 13:00, 1 May 2010 (UTC)

chrome plating

is there a way to tell if the layer underneath chrome plating is nickel or brass? —Preceding unsigned comment added by Tom12350 (talk • contribs) 02:19, April 30, 2010

Try using a magnet, nickel is magnetic, brass is not. If you have the tools to do it, you can also try measuring the density of the metal. Ariel. (talk) 06:54, 30 April 2010 (UTC)

would the chrome plating interfere with the magnet? —Preceding unsigned comment added by Tom12350 (talk • contribs) 03:29, April 30, 2010

No, chrome is non-magnetic (not under normal conditions, anyway). FWiW 76.103.104.108 (talk) 07:56, 30 April 2010 (UTC)

does it have to be any special type of magnet? —Preceding unsigned comment added by Tom12350 (talk • contribs) 06:44, April 30, 2010

Tom12350, please sign your posts with ~~~~. Just a regular magnet, a stronger one is better I guess. Flexible fridge magnets are pretty weak. Ariel. (talk) 11:48, 30 April 2010 (UTC)

If it is something you do not care about ruining, squirt some concentrated hydrochloric acid on it. If it is nickel, it will slowly fizz hydrogen gas and form a green-blue solution. If it is brass, it will barely fizz at all. --Chemicalinterest (talk) 11:19, 30 April 2010 (UTC)

Even through the chrome coating? Ariel. (talk) 11:48, 30 April 2010 (UTC)

No. --Chemicalinterest (talk) 14:03, 30 April 2010 (UTC)

this item has some greenish rust on it does that tell if it is nickel or brass? —Preceding unsigned comment added by Tom12350 (talk • contribs) 12:18, 30 April 2010 (UTC)

The greenish rust could be patina, not ferrous hydroxide. It would be a copper-containing alloy such as brass, copper, or bronze. Ferrous hydroxide would spontaneously oxidize to brown ferric oxide. --Chemicalinterest (talk) 14:03, 30 April 2010 (UTC)

How to remember names?

I could easily identify people's faces but it's hard for me to remember their names. Any tips on improving name recall?--121.54.2.188 (talk) 07:56, 30 April 2010 (UTC)

Saying their name out-loud whilst looking at them helps. E.g. if someone says "Hello i'm Trevor" you say "Hi trevor" whilst looking at them (similarly if you use their name to start with when referring to them it helps). 194.221.133.226 (talk) 08:15, 30 April 2010 (UTC)

Those that attended the Open University will all know of Tony Buzan. He gave really good advice on how to study effectivly. See Speed Memory – Remembering names and face. Chapter 9 page 59 [2].--Aspro (talk) 09:57, 30 April 2010 (UTC)

How do you learn best? Reading? Hearing? Doing? Whichever it is, do that with the name. Are you good at songs? Make a small ditty out of the name. Or imagine a dance. Or write it down. Or repeat it to yourself a few times. Whichever works best for you. What kinds of things are you good at remembering? Lets say you are good at remembering trees, then in your mind 'link' a kind of tree with the face and then the name. Just think of all three at once. Then you'll see the face, think of the tree, and then think of the name. Ariel. (talk) 11:49, 30 April 2010 (UTC)

I know a teacher, he is amazing with names. I don't know if that's because he's a teacher or that helped him to become a teacher. --Kvasir (talk) 18:35, 30 April 2010 (UTC)

I'm a teacher. I am terrible with names. So it isn't necessarily a related skill. --Jayron32 00:46, 1 May 2010 (UTC)

One thing that works for me is to associate the person with somebody you know who has the same name. Stanstaple (talk) 19:56, 4 May 2010 (UTC)

amines and hydroxide ions

I have reacted amines with hydroxide-sensitive electrophiles quite a few times now, most of the time due to solubility reasons I used an aprotic organic solvent anyway. But funny enough I haven't really thought of this ... if I had water-soluble reactants, if I dissolved bunch of amine (say a good Nu: like a secondary or primary amine) into water with my electrophile (not terribly sensitive to neutral water but sensitive to OH- on paper), would amine or hydroxide have the preference in adding to my electrophile? (Let's say, use a Michael acceptor as a convenient example.) John Riemann Soong (talk) 12:47, 30 April 2010 (UTC)

Can you provide any links where I can understand your terminology? --Chemicalinterest (talk) 16:42, 30 April 2010 (UTC)

Updated! John Riemann Soong (talk) 16:34, 2 May 2010 (UTC)

Our article on ammonium hydroxide notes that only 0.4% of a 1M solution of ammonia in water is in the form of [NH₄]⁺ + [OH]⁻. If this is also the case in the reactions you've been doing, then the concentration of free amine will far exceed that of hydroxide, so [OH]⁻ is unlikely to compete effectively with your intended nucleophile, the amine.

Am I right?

Ben (talk) 12:09, 2 May 2010 (UTC)

Hmm, thanks. Which is a better nucleophile, OH- or NH3? I think OH- is a little better overall, right? Will the comparative effectiveness depend on the mechanism (SN1 versus SN2, etc.)? What about Michael addition? John Riemann Soong (talk) 16:34, 2 May 2010 (UTC)

See nucleophilicity for some quantitative nucleophilicity scales. The rate of reaction of nucleophile and electrophile depends on the identity of both. Hydroxide will react faster with some electrophiles, ammonia (or amines) with others.

Hydroxide should be better at S_N1 than S_N2 because it is a hard nucleophile. NH₃ is (I think) borderline hard/soft, so should be OK at both. Both are bases, hydroxide being the stronger base, so you might get elimination reactions competing with nucleophilic substitution. For example, in S_N1 reactions, the carbocation can undergo E1 elimination to an alkene instead of accepting a nucleophile.

As you probably know, Michael addition favours soft nucleophiles because Michael acceptors are soft electrophiles, dominated by HOMO-LUMO interactions more than electrostatic interactions — basic HSAB theory. S_N2 also prefers soft nucleophiles because the carbon-leaving group σ* orbital is a soft electrophilic centre. I believe S_N1 works with almost any nucleophile, hard or soft, because most carbocations are very strong electrophiles. Where the nucleophile is soft enough and the electrophile can do both, S_N1 and S_N2 will compete.

Ben (talk) 18:38, 3 May 2010 (UTC)

magnetic question

If nickel is magnetic, why is a US 5 cent coin, made of 75% nickel, 25% copper not magnetic? Googlemeister (talk) 14:08, 30 April 2010 (UTC)

An alloy is not "pieces of one metal and pieces of another", but rather a single material with its own material properties not necessarily preserving all electronic and physical properties of each component. Our ferromagnetism article talks about the magnetic issue. DMacks (talk) 14:28, 30 April 2010 (UTC)

You have it backward, it's 75% copper, 25% nickel. Ariel. (talk) 14:28, 30 April 2010 (UTC)

Yes, rare earth metals aren't ferromagnetic, but alloys of them are. --Chemicalinterest (talk) 14:38, 30 April 2010 (UTC)

Neither nickel nor copper are rare earth elements. Every alloy has its own properties; it is invalid to say that "alloys of rare earth metals are ferromagnetic", because it depends on the particular alloy. Every part of you answer is wrong, Chemicalinterest. Please do not make things up before posting them to the reference desk. Nimur (talk) 15:28, 30 April 2010 (UTC)

I did not say that copper and nickel are rare earth metals. I was using that as an example that alloys are sometimes magnetic while the individual metals are not magnetic (or vice versa). Sorry if I confused anyone. --Chemicalinterest (talk) 16:27, 30 April 2010 (UTC)

Samarium-cobalt magnets are very strong, while samarium is nonmagnetic at normal temperatures and cobalt is much weaker. --Chemicalinterest (talk) 16:35, 30 April 2010 (UTC)

If you start adding copper to cobalt, that will start losing its magnetism as well. The copper electron will upset its magnetic moment, just as in nickel.--Aspro (talk) 19:09, 30 April 2010 (UTC)

Why the "niger" in Sciurus niger ?

Hello all,

Not sure if it should go here or on the language desk, but...

I was wondering why the scientific name of the Eastern Fox Squirrel is Sciurus Niger. Niger, both in Latin and in scientific nomenclature usage, has to do with the color black (cf. Niger_(disambiguation)#Species). But the Eastern Fox Squirrel is in fact not black at all, with the exception of some melanistic individuals, as with black panthers). So... why does their scientific name translate as "black squirrels" ?

Thanks, --Alþykkr (talk) 15:55, 30 April 2010 (UTC)

Some names are misnomers. -- Wavelength (talk) 16:26, 30 April 2010 (UTC)

Rattus rattus

This is the sort of question that is bound to come up again. The Type specimen ( the poor critter that ended up picked in a jar and sits on the shelf of some institution) which was used to first describe the species was – black!. As simple as that. Thinking you might not believe such an answer here is a PDF describing Sciurus niger niger.[3] Likewise if you look at the very broad range of Rattus rattus you can probably guess how that came to be the first type specimen as well.--Aspro (talk) 16:43, 30 April 2010 (UTC)

Thanks to you both. Aspro, I had thought of that, but somehow I thought that before naming a species and establishing a "type", you'd take more of a sample than just one individual. Oh well, guess hard sciences are not that hard. --Alþykkr (talk) 17:02, 30 April 2010 (UTC)

I imagine Charles Darwin and others look for a good 'typical' specimen but it's 'that' unique individual, the actual critter in the jar that is the reference specimen that zoologist always return to for comparison. I don't know if anyone can elaborate further on that? If they can, I'll add it to the WP article.--Aspro (talk) 17:13, 30 April 2010 (UTC)

In the 19th century it was pretty much the goal to find the "first" one and get it designated the holotype. Often this led to disputes and later redefinitions (if I recall Harvard has a triceratops skull that they claimed was a holotype, and Yale later proved it was just a variation on an already-identified species—which results in the skull being worth less, having less prestige, etc.). I don't know if that is the case here, but it is not uncommon in that particular era of taxonomy (I don't know if it still is or not, but I would imagine that things like DNA bar coding would make this a bit more unambiguous). --Mr.98 (talk) 02:39, 1 May 2010 (UTC)

transformer

when a transformer is on load its starting current is 12 times of its full load current called inrush current.then what is the starting current of a no load transformer and how. —Preceding unsigned comment added by Dvutukuri (talk • contribs) 16:34, 30 April 2010 (UTC)

The amount of current that passes through the coils of a no load transformer? None on the secondary side. --Chemicalinterest (talk) 16:37, 30 April 2010 (UTC)

Yeah this question is pretty bizarre even by our standards. A transformer typically will inrush some multiple of it's stated max current, like you said (and depending on the transformer's design). If there is no load then ipso facto there is no current on the output, and the input will only draw current according to the inrush characteristics as you already described. --Jmeden2000 (talk) 17:54, 30 April 2010 (UTC)

Per "Protective Relaying" by Blackburn and Domin, page 292-294 if a power utility transformer has no load on the secondary side, then the current drawn by the primary side is called the "exciting current" and its steady state value is typically 2% to 5% of the rated full load current. The transformer core of an unenergized transformer which has previously been energized may have residual flux, either positive or negative. Depending on this residual flux, the point in the voltage waveform at which the winding is energized, and the transformer design, an unloaded transformer might draw little more than the normal exciting current, or it might draw 8 to 30 times the full load current. It is not always 12 times as the OP stated. It may take 10 cycles to one minute for the inrush current on energizing to decay to the steady state exciting current value. In the case of high inrush, the transformer may make a large "Bong!" sound which decreases over a second or so, with dust flying off it. There may be a noticeable voltage dip if it is a very large utility transformer. Protective differential relays may see it as in internal transformer fault and trip the breaker, unless they are properly set to discount harmonic currents. This in itself is pretty "exciting" for those tasked with getting it in service. Edison (talk) 20:39, 30 April 2010 (UTC)

Expansion of the universe

Has it ever been hypothesized that the expansion of the universe is within each subatomic particles' growth from one instant to the next. in other words if you compared an object with mass = X at time = t to that same object with mass = X at time = t + y, it could actually be mass = 2X at time = t (in the past)? —Preceding unsigned comment added by 165.212.189.187 (talk) 16:57, 30 April 2010 (UTC)

No, it hasn't been hypothesized, since it doesn't make sense. If the mass at time t is X, then the mass at time t is X. It can't both be X and 2X (unless it is massless). --Tango (talk) 17:30, 30 April 2010 (UTC)

No let me rephrase: the mass of an object at two different times is two different masses: if you could go back in time and compare the future object to the past object. In other words we are all expanding through spacetime at the exact same rate so relative to each other we are not expanding but relative to our past selves we are. —Preceding unsigned comment added by 165.212.189.187 (talk) 17:45, 30 April 2010 (UTC)

The expansion isn't a mystery that needs to be solved, at least not in the sense you're talking about. It's already perfectly well modeled by general relativity. The idea that physical constants (like masses) might have been different in the past has been tested experimentally in various ways (by looking for variation in atomic spectral lines, for example). The experiments rule out anything more than a minuscule variation in physical constants over the age of the universe. -- BenRG (talk) 18:51, 30 April 2010 (UTC)

Isnt' General relativity is being put to the test everyday with quantum physics?Why couldn't those spectral lines be expanding also? A miniscule variation times all the atoms in the universe equals what ??? And BTW - What, pray tell, exactly is the sense that I am talking about? —Preceding unsigned comment added by 165.212.189.187 (talk) 19:13, 30 April 2010 (UTC)

General relativity makes very good predictions about this on large scales and quantum mechanics makes very good predictions about small scales. It is only when the two situations merge (eg. a large amount of mass in a very small space, like in a black hole or at the big bang) that our theories are inadequate and the expansion of the universe isn't purely within the realms of general relativity. I'm afraid you aren't making any sense at all. --Tango (talk) 21:29, 30 April 2010 (UTC)

I don't recall where I saw it, but there was a comic where a character postulated that he and everything in the universe was about to double in size. The next panels don't show any difference since all the reference points expand as well. If this is the situation the OP is asking about, then it would be an absurd and unfalsifiable proposal that doesn't seem to explain anything. — Ƶ§œš¹ _{[aɪm ˈfɹ̠ˤʷɛ̃ɾ̃ˡi]} 21:51, 30 April 2010 (UTC)

It's not a mystery in the sense that we already have a good model. There's always the mystery of "why that model?", but that's different from having no working model in the first place. "Why couldn't those spectral lines be expanding also?" Well, they could, but it turns out (experimentally) that they aren't. I'm talking about spectral lines of distant astronomical objects here, where the light has been in flight for a long time. -- BenRG (talk) 21:50, 30 April 2010 (UTC)

Doesn't seem to explain anything except why the universe is "expanding" . and do spectral lines have mass? Tango says that when the two situations merge that current theories are inadequate and then says that I! don't make any sense?! for all we know those "two situations" are not only merged all around us but completely inseperable! 98.221.254.154 (talk) 04:13, 2 May 2010 (UTC)kgb

So the universe is expanding because the universe is expanding? If the space between atoms is expanding and it's unobservable, then it's something different from the expansion of the universe that we can observe. — Ƶ§œš¹ _{[aɪm ˈfɹ̠ˤʷɛ̃ɾ̃ˡi]} 19:20, 4 May 2010 (UTC)

Not the space between atoms, the space INSIDE atoms, between subatomic particles, especially the electron cloud and the nucleus, and empty space itself. we can only observe it on the largest scales. Like when you put a marshmallow in a vacuum canister and it expands. That is whats happening to us and everything else at the same time. like the tidal force of the big bang pulling us in all directions equally.

increase the likelihood of having dreams

I asked a question here about dream recall, and someone suggested that eating lobsters would "increase the likelihood of having dreams". Is this true? What chemicals or substances do lobsters contain that might induce dreams? I must add I have no intention of ever eating lobsters myself because I'm a vegetarian. 82.43.89.71 (talk) 18:15, 30 April 2010 (UTC)

Seems like strange advice. I think that with a good night's sleep the likelihood of having dreams is pretty near 1 anyway. (REM Sleep is certainly almost 100% likely.) It's question of whether or not you remember them. (This usually requires waking up before it ends.) APL (talk) 18:46, 30 April 2010 (UTC)

Some foods, like lobster and cheese-an-onion sandwiches for supper, are 'reported' to give some people nightmares, but there is no proof of this -that I know of. Drugs on the other hand can, so its possible that a meal could send someone's brain messenger chemicals up dramatical. Antidepressants such as SSRI's can definitely give people nightmares and bright vivid dreams, as can St Johns Wort. Generally, I would say that if someone can't remember their dreams, then that is an indication that their brains are working normally. I get the very strong impression at times, from people who can remember their dreams in great detail, that their half way to being loopy – but that's just my impression and not a diagnosis of anyone. --Aspro (talk) 18:54, 30 April 2010 (UTC)

Did you mean to type THEY'RE half way to being loopy ? Cuddlyable3 (talk) 18:50, 1 May 2010 (UTC)

You can get advice about anything here. Sometimes it's worth exactly what we charge. alteripse (talk) 20:59, 30 April 2010 (UTC)

Well, theoretically very heavy meals can put you into a quick, deep sleep (think Thanksgiving - it's the amount of food and alcohol). This is an absurd stretch, but since eating lobster requires more energy than the average meal (cutting, cracking, etc.) and everything is essentially dripped in butter, then I suppose one could make the argument that it's more likely to knock you out than your average other meal. Especially since, lobster being (somewhat of) a delicacy, other things like wine and desert are probably being served as well. ~ Amory (u • t • c) 00:34, 1 May 2010 (UTC)

Quite possibly tryptophan. Cheese contains this, and some page I found on the internet [4] ranks a lot of crustaceans highly for tryptophan content. It ought to just make you relaxed, though, rather than inspire nightmares, as mentioned at Cheese#Effect_on_sleep. There is also cheese syndrome, mentioned at List of foods containing tyramine, and the whole cheese/dimethyltryptamine incompatibility thing, but I guess that has no bearing on lobster. Unless it's fermented lobster. 86.21.204.137 (talk) 11:33, 1 May 2010 (UTC)

It's nothing to do with diet. This probably falls under original research but I once did a course relating to dreams. It seems everyone dreams but many people don't remember them. The thing to do is write down anything you remember, even vague impressions, as soon as you wake up. After a few weeks you will be amazed how much detail you are writing down. It worked for me anyway.--Shantavira|^{feed me} 11:45, 1 May 2010 (UTC)

Jeez - what a lot of terrible answers have been given here! The idea that what you eat causes dreams is pure old-wifes-tale. How about we offer an actual scientific answer with some value to it instead of propagating bullshit?

Vivid dreams happen during REM sleep. As you will notice if you read that article, there has been considerable research into the subject - and not ONE of the linked articles describe evidence for food-related issues with REM sleep. So let's stop talking crap about lobster, onions, tryprophan and cheese - that's complete nonsense.

When you sleep for long enough to achieve REM sleep, you will dream - that's how it works. Typically, you'll enter REM sleep a few times each night - for a total of maybe an hour and a half. However, you won't remember those dreams unless you happen to wake up during REM. So of the half dozen ~15 minute dreams you have every night - you are unlikely to remember most of them. So the only way to remember more dreams (or to even know that they happened) is to somehow be awoken during REM sleep.

However, that's not easy to achieve - if you had something or someone wake you up frequently - you might never enter REM sleep (which would ultimately be bad for your health - people have become mentally deranged from prolonged lack of REM sleep). If you had something wake you up just once at a random time during the night, then the odds are about one in five that it would wake you during REM and produce a dream that you could remember. What you'd really need is someone (or some cunning machine) look for the 'rapid eye movement' that characterizes REM sleep and to wake you up maybe 10 minutes after it starts. However, if you have an alarm clock set to wake you in the morning before you'd naturally wake up by yourself - then that has just as much chance of waking you during REM than at any other time. But because you only spend 20% in REM - waking up with an alarm clock has about a one-in-five chance of waking you in the middle of a dream. But even if you do wake in the middle of a dream - the memory of it usually fades within minutes, so you need to keep a 'dream diary' and make a point of writing down as much of the dream as you can remember, the moment you wake up. So you are almost certainly having several dreams per night - and waking up with the memory of a dream once or twice a week - but simply failing to retain them in long-term memory. SteveBaker (talk) 15:17, 1 May 2010 (UTC)

Tryptophan does send you to sleep, which is a necessary prerequisite for having a dream. My answer may have been terrible and nonsense, but I don't think it was terrible in bold and italics, or complete nonsense. Perhaps lobster gained a reputation by making people more likely to have plesant naps and daydreams at the dinner table, or causing their minds to wander more in the early stages of sleep, possibly followed by waking up again due to indigestion from all the rich food. 86.21.204.137 (talk) 16:10, 1 May 2010 (UTC)

Great - so your advice for dreaming more is to sleep more. Profound. Thanks. Please, at least read REM sleep before you answer any more. SteveBaker (talk) 19:07, 1 May 2010 (UTC)

Your answer was technically correct if you define dreams narrowly, mine was about lobster and I suggested a psychoactive substance in it, and I was quite pleased with myself until you started implying that I'm Mystic Meg or something. I know what REM sleep is. Stop being insulting. 86.21.204.137 (talk) 20:05, 1 May 2010 (UTC)

External stimuli are definitely misinterpreted in dream scenarios. This is dramatised in countless movies where a character is woken out of a dream by a touch or a sound. Indigestion following something one ate the previous evening can also affect one's dream content, usually unpleasantly. This is common experience. BTW SteveBaker, old wives can be reliable sources. Cuddlyable3 (talk) 19:03, 1 May 2010 (UTC)

When old wives write for peer-reviewed scientific journals or other WP:RS...yes. Otherwise, not so much so. SteveBaker (talk) 19:10, 1 May 2010 (UTC)

Would Marie Curie fit the bill? 67.170.215.166 (talk) 05:36, 2 May 2010 (UTC)

Oddly enough, the best answer I can come up with is to get depressed. Antidepressants actually have the opposite effect: they reduce the amount of REM sleep, sometimes to the point of eliminating it altogether. There is a lot of evidence that many people with severe depression have altered sleep patterns that cause them to miss slow-wave sleep and go into the dream state much earlier at night that healthy people do. I doubt that this is the sort of solution the OP was looking for, but it's the only one that comes to me. Looie496 (talk) 23:21, 1 May 2010 (UTC)

Question about gun-type fission weapon

According to gun-type fission weapon the bomb fires U-235 at another U-235 target, and then that achieves critical mass, and fission occurs due to neutrons splitting the atom. Ok, but where are the neutrons coming from? ScienceApe (talk) 19:33, 30 April 2010 (UTC)

Uranium (as with all radioactive elements) is intrinsically unstable and spontaneously undergoes nuclear decay (fission in the case of uranium). So there are constantly neutrons being produced by this natural process. And some of them happen to hit other atoms nearby, causing them to decay. But many/most of them escape without causing anything from happening. In a critical mass, there are enough fissionable atoms nearby that the neutrons from one fission event hit several others rather than generally not hitting anything. The result is an exponential increase in the rate of reaction rather than a constant slow reaction. The "Little Boy" section of the gun-design article you were reading has all this information and more. DMacks (talk) 19:50, 30 April 2010 (UTC)

U-235 and U-238 undergo spontaneous fission with a low probability and this produces a few neutrons (as well as ambient neutrons from other sources like cosmic rays). According to Gun-type fission weapon, the 20% U-238 in Little Boy had 70 spontaneous fission events per second. Once a supercritical mass is assembled, any of these events could trigger a detonation. Dragons flight (talk) 20:00, 30 April 2010 (UTC)

Spontaneous fission is far too unreliable. It was on the article once but I think people are removing things. Around the tops of the uranium pieces were polonium and beryllium rings. When the uranium comes together, the polonium and beryllium are physically intermixed and emit neutrons of about the right energy to initiate a chain reaction and at the right time. There is about a two microsecond window for this to happen.--Aspro (talk) 20:09, 30 April 2010 (UTC)

You could rely on spontaneous fission alone, and Gun-type fission weapon says "An initiator is not strictly necessary for an effective gun design". But in practice Little Boy did use an initiator (that article says "Initiators were only added to Little Boy late in its design), as do implosion bombs. Modulated neutron initiator is the relevant article. -- Finlay McWalter • Talk 20:11, 30 April 2010 (UTC)

In the case of Little Boy, the 20% U-238 in the uranium had 70 spontaneous fissions per second. With the fissional material in a supercritical state, each gave a large probability of detonation: each fission creates on average 2.52 neutrons, which each have a probability of more than 1:2.52 of creating another fission. During the 1.35 ms of supercriticality prior to full assembly, there was a 10% probability of a fission, with somewhat less probability of pre-detonation. Think about it, the figures are naff! They might as well have trained a chimp to bang two lumps together with his hands and it would have been just as 'efective'. This is Wikipedia after all.--Aspro (talk) 20:27, 30 April 2010 (UTC)

I don't know what that means, but see demon core. Comet Tuttle (talk) 22:21, 30 April 2010 (UTC)

If you combined two lumps of the right amount of U-235 in, say, a bucket, you'd definitely get a reaction. But the difference between something carefully controlled and something haphazard would be significant. The first is probably in the neighborhood of 500 tons of TNT (which is still a pretty big explosion by human standards!), whereas the latter is in the neighborhood of 15,000 tons of TNT. If you are really good about controlling it (as they would be in later weapons) you can get more yield from the same amount of material (say, 40kt out of the same original amount), or use less material for the same yield (e.g. you get a "Little Boy" sized explosion out of something that can fit into an artillery shell). --Mr.98 (talk) 23:45, 30 April 2010 (UTC)

Yes, they wanted an overwhelming number of neutrons. The problem is not that a fission reaction would not begin (it would) but that the result would have been a fizzle (if you don't get a very good reaction started, it will blow itself apart before it is really destructive). So they used initiators. Not strictly necessary, but for a totally untested weapon, they provided a pretty good measure of certainty that you'd not only get a reaction, but a big one. --Mr.98 (talk) 23:42, 30 April 2010 (UTC)

the thermodynamics of an ideal air conditioner

Say the temperature of the environment around the exhaust port is at some absolute temperature T3 (it is a heat sink and remains at a constant temperature). You start with room some temperature T2 and cool it to T1.

Under standard atmospheric pressure (constant P and V) of regular old air in the room, how much free energy per mole of air molecules (on average) do I need to expend to effect this temperature change, as a function of the three given temperatures T1, T2 and T3? How would I begin to attack this problem? What thermodynamic relationships should I use?

Some assumptions: heat capacity of air is mostly constant with temperature, especially at the range we're considering (cooling from say, 310K to 290K). And I am curious about the two cases: initial room temperature starts BELOW exhaust temperature, initial room temp == exhaust temp, initial temp > exhaust temp. Btw, the exhaust temp is just the temperature of the heat sink, assume perfect/instaneous heat dissipation from the exhaust to the "outside" so it's not like we have to worry about energy expenditure on fans. And obviously exhaust temperature is always higher than final room temperature (or else the air conditioner would have no purpose -- we'd just go outside!). And of course, assume no heat/mass transfer between the room and the "outside" other than through the air conditioner exhaust.

I'm just curious say, when an air conditioner operates at 1000W, how much of that is used to perform thermodynamic work and how much of that is lost through inefficiency of the machine. How much is also lost due to the inefficiency of the room (on average, assuming a shut door and closed windows)? Rough proportions, of course. John Riemann Soong (talk) 19:52, 30 April 2010 (UTC)

Wikipedia has an article on heat pumps Heat_pump#Efficiency --Aspro (talk) 20:18, 30 April 2010 (UTC)

This seems to be based on the COP definition though. Which is sort of weird. Is there any relation I can get where I can solve for free energy? John Riemann Soong (talk) 22:00, 30 April 2010 (UTC)

Gun with balloon

Attach an inflated balloon to the muzzle of a pistol. Let's say the balloon has a diameter of 20 cm and will burst when its diameter reaches 30 cm. If you shoot the gun, would the balloon be pierced by the bullet or would it burst before that because of the expanding gases from the exploding gun powder? --InfoCan (talk) 20:24, 30 April 2010 (UTC)

After the bullet comes out, the air comes out at the same speed. Probably both will happen at the same time because the bullet and the air are travelling at the same speed. --Chemicalinterest (talk) 20:33, 30 April 2010 (UTC)

The gases will actually decelerate much faster than the bullet will because of fluid drag and turbulence. Furthermore, I am not sure the volume of the expended gases would be enough to pop the balloon by itself. A 20-30 cm diameter increase would represent 1.33*(3.14)*(15*15*15 - 10*10*10) = 522 cc increase, or roughly 1/2 a liter. At STP, this would be .522/22.4 = .0233 mol of expended gas. Even owing to the increase in volume due to the temperature of gas, I am not sure that that much gas is released by the cartridge in the conflagration that expells the bullet. I think its the bullet, and not the gas, that would burst the balloon. If the balloon were exactly at the breaking point, then maybe the gas would break it first. But given the parameters above, I doubt the gas would break the balloon before the bullet would. --Jayron32 21:10, 30 April 2010 (UTC)

Here's my idea: In order for the expanding air to break the balloon, it must first expand from where it is formed (the gunpowder) out to the edge of the balloon. Is it reasonable to assume that the wavefront of the expanding air spreads at the speed of sound? If so, and the bullet moves faster than the speed of sound then it will pierce the balloon before the balloon even feels the force of the expanding air. Thoughts??24.150.18.30 (talk) 02:07, 1 May 2010 (UTC)

Most pistols fire subsonic ammunition (that's a lousy redirect: our ammo article doesn't even talk about subsonic/supersonic bullets. Our cartridge article at least mentions the terms, but only in passing). So the shock wave would hit the rubber first. Would the shock wave to enough to pop a balloon? I have no idea. Buddy431 (talk) 04:57, 1 May 2010 (UTC)

That's because most pistol ammunition actually is supersonic; subsonic ammunition is used in situations where you need less damage potential or you want it to be quieter if the gun itself has a suppressor. The other thing I would point out is that while conventionally you would think that a shock wave in air would travel at the speed of sound, don't forget that the pressure behind the wave is significantly high thus essentially raising the speed of sound for air at that pressure. Given enough pressure the shock wave can easily travel much faster than the speed of sound at sea level. So, to venture a conclusion to the question, there are several variables such as the tension in the balloon (i.e. how much pressure already exists inside it) and the type of bullet and length of gun barrel being used. In most cases I bet that the bullet would puncture the balloon first. --Jmeden2000 (talk) 14:46, 1 May 2010 (UTC)

When the bullet emerges from the muzzle, it is riding in front of a jet of gas molecules produced from the explosion. So the answer to the question lies partly in how quickly the new gas molecules randomize their trajectories and distribute themselves evenly inside the ballon, so as to be able to push the wall of the balloon rather than the back of the bullet. --InfoCan (talk) 04:51, 2 May 2010 (UTC)

Telescope

If we could look far as a billion years light from Earth then why couldn't us look inside in the other planets so we could figure out aliens exist or not. Another question, as i knew if we look at the planet 5 years light ago from Earth what we saw is what happened on the planet 5 years ago not at current time right? Have we prove it?75.168.119.109 (talk) 22:58, 30 April 2010 (UTC)

1. Yes, we can use our telescopes to look at exoplanets circling other stars and try to figure out whether there are advanced alien races living there, probably by looking for a surprisingly large amount of electromagnetic energy coming from the planet (as in the movie Contact). Unfortunately, our telescopes aren't able to resolve sharp detail at many light years' distance, so most exoplanets we have detected so far have been gas giants like Jupiter, which can't sustain life as we know it. As we invent better telescopes, we'll be able to detect smaller and smaller planets around other stars, which may help.

2. That's correct; as our speed of light article discusses, light does not travel instantaneously, but moves at a speed of exactly 299,792,458 meters per second. The term "light year" means "the distance that light travels in a vacuum in 1 year", so, yes, when we look at a star that's 5 light years away from us, we are seeing light that was emitted 5 years ago. The star might have exploded 2 years ago and we're still not going to be able to see that it exploded for another 3 years.

3. Yes, the speed of light has been measured; see speed of light. Comet Tuttle (talk) 23:26, 30 April 2010 (UTC)

Nice answer! But can we look at inside the planets, like look at it's surface? If there are aliens in there, could we see them? Or we only could see the outside of the planets.

It is kind off weird. If we discovered some aliens but they are billion years light from us that's mean those aliens we saw were exist billion years ago, that shows it is hopeless to contact aliens because what we saw is not what actually happening. How far we could look into space, how many billion years light could we look at now? Why don't we invent a big telescope to look at 14 billions years light from us then we could see what happen 14 billion years ago. We may see BIG BANG.75.168.119.109 (talk) 23:53, 30 April 2010 (UTC)

In theory we could see a planet's surface, if we had a powerful enough telescope. However, such a planet probably would not have the atmospheric gases (such as water vapour) Earth does, and would be unlikely to support life. A larger telescope does not necessarily mean more powerful. Furthermore your final assertion assumes that the Big Bang occurred 14 billion light years away, which would put Earth at the edge of the Universe. Intelligentsium 00:01, 1 May 2010 (UTC)

We do not have telescopes powerful enough to show the surface of any exoplanets. But see betelgeuse to see a picture of the surface of a star. Note that betelgeuse is just a few light-years away and still we can barely distinguish any of its surface features at all. The idea of seeing a civilization billions of years away is completely hopeless. The Hubble telescope has allowed us to see pictures of galaxies many billions of years into the past and learn a lot about the beginnings of the universe. Unfortunately, it is not possible to see the big bang because the young universe was opaque. Dauto (talk) 00:13, 1 May 2010 (UTC)

Part of the problem is that light tends to spread out from a source. So, not only do objects which are farther away take longer for the light to reach us; we receive less light from those objects. Now, imagine bouncing a tiny portion of that light off a dark object and trying to catch THAT. Astronomical distances are huge, and relative to stars, planets are pretty small, and in order to support life, planets need to be a considerable distance from stars. In order to improve the resolution of a telescope, you need to collect more photons of light; well, with some of these exoplanets, we may only receive a total of a few photons at a time; far too few to resolve anything. In other words, even if we could catch EVERY photon of light hitting the earth from those planets (a telescope with infinite resolution, lets say) we still could not resolve the surface of the planet to any accuracy. --Jayron32 00:26, 1 May 2010 (UTC)

Most of our telescopes cannot resolve the Apollo landers on the Moon. I doubt that any would be able to resolve surface detail on exoplanets, let alone aliens. ~AH1^(TCU) 01:44, 1 May 2010 (UTC)

We just recently were able to directly see any exoplanet, at all, with any telescope. That's Fomalhaut b. Fomalhaut b is pretty much right in our faces, in star terms, at only 25 light years away. It's a gas giant, probably about the same size as Jupiter, though it's further away from its star than Neptune: that is, it's hard to imagine an alien civilization developing there. However, even with probably the best visible light telescope in the world for this sort of thing (Hubble), it appears to take up about four pixels in the photograph, and no surface detail whatsoever is visible. Now, our resolving power is certainly going to get better with new telescopes; if the Advanced Technology Large-Aperture Space Telescope ever gets built and launched, we might actually get some differentiation across the surface of very near and very large exoplanets. But even that probably couldn't even see a rocky planet closer to its star, let alone resolve surface detail. In short, we aren't going to detect an alien civilization anytime soon by seeing their cities from Earth, regardless of whether they're on the surface of underground. Buddy431 (talk) 04:50, 1 May 2010 (UTC)

I understand the question to be: since we have all kinds of tremendously powerful telescopes, can we look literally inside the planets in our own solar system? That is to say, under the surface of Mars? And I don't know, but I think not. 86.21.204.137 (talk) 11:59, 1 May 2010 (UTC)

Short answer: Yes, we can see below the surface of Mars.

Long answer: It depends on how you define the word "telescope" - but if you think of it as a thing for capturing visible light - then "No" - the solid surface of the planet is opaque to visible light - and you can't see more than a millimeter or two into that kind of object even with a super-bright light source and super-sensitive detector. But if you think more in terms of "radio telescope" and widen your definition of "telescope" to "a thing for capturing electromagnetic radiation" - then you could look at ground penetrating radar as a kind of "telescope"...and we have certainly scanned the surface of Mars with ground penetrating radar (see SHARAD and MARSIS). People don't normally describe these things as "telescopes" because they have to emit the radio waves and read back the reflection from the sub-surface layers of the planet. But this is how we examine the subsurface layers and "look inside" both Earth - and other planets. Obviously though, we can't do that with exoplanets because we have no way to get close enough. SteveBaker (talk) 14:44, 1 May 2010 (UTC)

That's mean our telescope is not advance enough. I think the important thing now is to developed an advance telescope to search for living thing. We only need to see them and take a picture of them. It is easier to contact them than to see them. How many years light could we look from Earth now?75.168.119.109 (talk) 05:38, 2 May 2010 (UTC)

I still don't understand why we could not see the big bang if we could look at 14 billion years light away from Earth, which is the time big bang occurred?75.168.119.109 (talk) 05:44, 2 May 2010 (UTC)

We can't see the big bang because the young universe was hot and dense which made it opaque. So, we cannot see all the way back to the big bang because there is no light coming to us from that far back since it was opaque. That's the same reason why we cannot see the center of the sun. The sun is hot and dense which makes it opaque, therefore there is no light coming to us from the center of the sun. Dauto (talk) 16:48, 2 May 2010 (UTC)

Habeñero pepper safety

Could a healthy person with no underlying medical conditions be hurt by eating an excess of Habeñero peppers? If so, what would be the safe limit for eating them? MMS2013 23:23, 30 April 2010 (UTC)

Capsaicin#Effects_of_dietary_consumption, perhaps. 90.195.179.138 (talk) 23:30, 30 April 2010 (UTC)

Also see Chili pepper#Possible health risks and precautions. Comet Tuttle (talk) 23:32, 30 April 2010 (UTC)

I strongly recommend reading this: http://www.habanero-hamburger.com/index.shtml - it's the website of a recently closed pub in San Mateo who regularly served Habanero Hamburgers - one pepper, lightly grilled, in a regular burger. There are some very detailed - vivid - literally "gut-wrenching" - descriptions about the consequences of eating one of these burgers (and one especially detailed blow-by-blow account here). The consensus is that if you can eat it in 60 seconds and no more than 5 bites - you'll get it down, then be in horrible pain for the next 12 to 20 hours as the stuff makes it's way through your digestive system...and there are many descriptions of "the ring of fire" and "exit wounds"! Having said that, there are people who have eaten them on as many as 20 separate occasions - and others who simply couldn't manage more than a single bite of the stuff. Our local NPR radio station interviewed the owner of the pub just before it closed - he said that he made people sign a waiver and present a doctor's note to prove they had no heart conditions before he would serve them - and despite that had several occasions when people had to be rushed to hospital before finishing their meals! There are a few people who ate two of them at one sitting. So, healthy people can certainly survive eating a couple of these toxic veggies - but it is most certainly not recommended. SteveBaker (talk) 02:10, 1 May 2010 (UTC)

I wonder if Johnny Cash had visited that place when he wrote his hit song "Ring of Fire"... ;-) 76.103.104.108 (talk) 02:27, 1 May 2010 (UTC)

(edit conflict) In college, I had a Hindi-Malaysian roomate who could literally eat them like strawberries. He'd comment that they were very hot, but not unbearably so. I managed to eat one, but didn't relish the experience. Oddly enough, I like the flavor of Habeneros a lot, so long as they are used right. Used sparingly, I find that they have a good "sweet" flavor under the heat, not unlike a Tabasco pepper, I like them better than the milder, but more common, Jalepenos, which I find to be bitter and grassy flavored. --Jayron32 02:39, 1 May 2010 (UTC)

Yes, habaneros are very tasty. I have built up a certain tolerance to the heat, and I agree that they have a lot of flavor beyond the heat. I like to use them to start a tomato sauce (sautee them along with the garlic, before putting in the tomatoes and wine), or sliced thinly on a toasted sandwich of sharp cheddar, black olives, maybe some tomato and avocado. Or I sautee them in the butter that I then use to fry an omelette.

I had to threaten my local supermarket that I'd stop shopping there if they stopped carrying them. They tell me that not many other customers buy them, which seems strange to me — it's not like I'm in the middle of Iowa or something.

There's a pepper I like even better, the Scotch bonnet. I can't find it around here anywhere. It was easily available when I lived in Texas and in Canada. --Trovatore (talk) 09:21, 1 May 2010 (UTC)

An aside here — the pepper's name is simply habanero, no eñe. It means "from Havana" (Havana is La Habana in Spanish; again, no eñe). This is one of my mild peeve spellings, though it doesn't bother me quite as much as latté, which is an error of a similar provenance. --Trovatore (talk) 02:15, 1 May 2010 (UTC)

Just to take the question literal: For most people, "hurt" starts at microscopic amounts of a habanero. "Injured" is much further down that path.... --Stephan Schulz (talk) 09:56, 1 May 2010 (UTC)

I have searched without avail for a BBC news article I read maybe two years ago in which a man died from eating ludicrously hot chilli peppers. What I remember is that they were served to him by a man who grew his own, and either it was a for a dare or there was a mix-up over hotness (perhaps both). What might have happened, of course, is that he turned out to have an allergy; but then you wouldn't think he'd be eating chilli peppers at all. If anybody can find this article, I'd be very grateful, since it's the kind of question that comes up in conversation often. 86.21.204.137 (talk) 12:29, 1 May 2010 (UTC)

If you frequently eat very spicy food, you become insensitive to it. But then normal food will become tasteless. I know someone who cannot eat normal food like bread anymore because of this. Count Iblis (talk) 15:29, 1 May 2010 (UTC)

This is not my experience. I still enjoy non-hot food. It's true that I don't get much satisfaction out of food that's supposed to be hot, but isn't; that strikes me as different from what you're talking about.

My supposition is that the tolerance is specific to the heat-inducing chemical, capsaicin. I can't see any reason that tolerance would reduce your sensitivity to other tastes. --Trovatore (talk) 17:52, 1 May 2010 (UTC)

The stories of people eating these things without the resulting pain reported by others often derives from the fact that there is a huge range of hotness in the same species of pepper. In particular, here in Texas you can buy specially bred 'mild habaneros' that - while still pretty spicy compared to a jalapeno - don't have the gut-wrenching effects of the habaneros at the top end of the scale, yet retain the interesting flavor. I've eaten those - and they don't compare with "the real thing". Our habanero article says that growth environment and and other factors can also have a large effect on the heat of the pepper. The San Mateo pub I linked to above used only Panamanian Habaneros - which are the most notorious kind. SteveBaker (talk) 16:28, 1 May 2010 (UTC)