I have 2 questions

[Money]

1. why is it impossible to reach zero kelvin

cant experiments be done on a enclosed area

or something like that and eventually put it at absolute zero

and if someone was frozen at absloute zero

could they go through time then be warmed up enough

to live like in movies ???

 

2. if matter cannot be created or destroyed and energy is matter

when molecules collide and destory one another and photons are

emitted isnt energy created ??? or anytime something emits photons

isnt that energy being created ???

[BenTheMan]

Hmm. On 1 I think quantum fluctuations keep the temperature above zero.

 

For 2, energy isn't created---it's just changed form. Think of potential energy being changed into kinetic energy. There is some energy due to the rest mass of the particles (E=mc^2) that gets turned into high energy photons.

[314159]

You asked about whether someone could be frozen and then warmed up enough to live, which is the idea of cryogenics. The idea is that you cool someone enough that any rot or decay ceases, so you don't need to get right down to absolute zero, just 'pretty cold'.

 

The trouble, at present, is that if you try that, all the water in your cells turns to ice, and ice takes up more space than water, so your cells burst as you get frozen. All the people in cryogenic chambers around the world are massively damaged on a cellular level, and you'd have to do quite a repir job to put them back together.

It may be possible in the future to carry out reanimation from a frozen body. There's a frog (or it may be a toad, I forget) that can be fully frozen in winter, and come back to life when it thaws. It does this as it has a high sugar content in its cells which stops the water in them freezing and killing it when it's in its frozen state.

 

In answer to pt 2, as was said, this energy is already there in other forms. matter and energy are essentially the same thing, and energy can be stored in more ways than just a photon. For example, energy may be lost by an electron in an atom, causing a photon to be emitted. Energy is conserved, as it's changed from one form to another. moleculescolliding don't destroy one another, but even if you had a particle collide with its anti-particle, the photon energy coming out would just be the energy that was earlier present in the form of mass, seeing as energy and mass are basically the same thing.

[ultma]

You asked about whether someone could be frozen and then warmed up enough to live, which is the idea of cryogenics. The idea is that you cool someone enough that any rot or decay ceases, so you don't need to get right down to absolute zero, just 'pretty cold'.

 

The trouble, at present, is that if you try that, all the water in your cells turns to ice, and ice takes up more space than water, so your cells burst as you get frozen. All the people in cryogenic chambers around the world are massively damaged on a cellular level, and you'd have to do quite a repir job to put them back together.

It may be possible in the future to carry out reanimation from a frozen body. There's a frog (or it may be a toad, I forget) that can be fully frozen in winter, and come back to life when it thaws. It does this as it has a high sugar content in its cells which stops the water in them freezing and killing it when it's in its frozen state.

 

It has to do with the shapes of solid water with the frog the sugar makes the solid more smooth and rounded, and in humans it becomes sharp and spikey.

[swansont]

Any sample you have will always be exchanging energy with its surroundings, which spontaneously goes from hot to cold, so even classically you can't get to absolute zero.

[Money]

iight thanx but why is it impoosible to reach absolute zero

[J.C.MacSwell]

Any sample you have will always be exchanging energy with its surroundings, which spontaneously goes from hot to cold, so even classically you can't get to absolute zero.

 

Wouldn't you have an infinitesimal chance of a shot at it classically? (Or perhaps Maxwells Demon could create it, by slowing all heat energy to zero, not using a gate but a paddle and expelling the energy outside the system)

[Klaynos]

iight thanx but why is it impoosible to reach absolute zero

 

I think posts 2 and 5 answered that.

 

RE quantum fluctuations, they are also known as vacuum fluctuations:

 

http://en.wikipedia.org/wiki/Quantum_fluctuation

[swansont]

Wouldn't you have an infinitesimal chance of a shot at it classically? (Or perhaps Maxwells Demon could create it, by slowing all heat energy to zero, not using a gate but a paddle and expelling the energy outside the system)

 

How would you keep the paddle from radiating?

[314159]

Seeing as maxwell's demon is just an idealised construct in the first place, I think we can assume his paddle doesn't radiate; it's a perfect reflector that emits nothing. He's not physically possible anyway.

 

It's an interesting question, why we can't reach zero K, and the reason I didn't answer earlier is that I don't really understand the reasons we can't. For example, if quantum fluctuations cause random changes in heat energy, surely at some point, in a cold environment, that random change in energy would change the temperature to zero?

[J.C.MacSwell]

Seeing as maxwell's demon is just an idealised construct in the first place, I think we can assume his paddle doesn't radiate; it's a perfect reflector that emits nothing. He's not physically possible anyway.

 

It's an interesting question, why we can't reach zero K, and the reason I didn't answer earlier is that I don't really understand the reasons we can't. For example, if quantum fluctuations cause random changes in heat energy, surely at some point, in a cold environment, that random change in energy would change the temperature to zero?

 

Classically I think this is correct, although "some point", for a minutely small sample could be billions upon billions of years (?).

 

Non classically if our sample reached (not sure if it could) exactly zero K, we could not know where in the Universe it is.

[314159]

Ah, now I feel stupid. Of course the uncertainty principle would mean that particles known to have zero velocity would have a competely unknown location...

[swansont]

Seeing as maxwell's demon is just an idealised construct in the first place, I think we can assume his paddle doesn't radiate; it's a perfect reflector that emits nothing. He's not physically possible anyway.

 

Sure, once you posit a physically impossible situation, you can posit an infinite number of them; it becomes science fiction at that point. But idealized and impossible are not the same thing. Maxwell's demon has valid scientific criticisms that show that such a being would not violate the 2nd law of thermodynamics (it would do work or its own entropy would increase) and as such, is not an impossible construct even if it is idealized. So if we limit ourselves to a mechanism that is not impossible, then the paddle would necessarily radiate, since it would not be at 0 K, and this would limit the temperature of the sample.

 

All without invoking quantum mechanics.

[J.C.MacSwell]

Sure, once you posit a physically impossible situation, you can posit an infinite number of them; it becomes science fiction at that point. But idealized and impossible are not the same thing. Maxwell's demon has valid scientific criticisms that show that such a being would not violate the 2nd law of thermodynamics (it would do work or its own entropy would increase) and as such, is not an impossible construct even if it is idealized. So if we limit ourselves to a mechanism that is not impossible, then the paddle would necessarily radiate, since it would not be at 0 K, and this would limit the temperature of the sample.

 

All without invoking quantum mechanics.

 

If the Paddle was simply a neutron would it radiate? Not sure if it could have a temperature but it would certainly accelerate during the process. I may have asked you this before but have forgotten. I think the answer was yes, due to its positive and negative parts even though it is neutral, somewhat similarly to an atom.

 

The only refutation of the Demon (beyond the obvious you have stated) that I have heard is a quantum one with regard to the Demon's uncertainties in the knowledge of the particles and the gate (now paddle in this case)

 

One other point is that classically if you could start out with some part of a system at absolute zero it would not remain that way very long, the system would move to a different state. Since classical mechanics is reversible, this should prove (assuming classical mechanics) that absolute zero could be achieved. The "different state" could move to the original in theory, no matter how unlikely.

[swansont]

No, a single particle does not have a temperature. Neutrons have a magnetic moment, and should radiate.

 

"Some part of the system" at 0 implies non-equilibrium, and temperature isn't really valid under that condition. Classically, individual particles could be at rest in the system, but temperature is a collective, steady-state property. You can have negative temperatures (T<0 solution to equations of excited state distributions) when you have a population inversion, i.e. not in equilibrium.

[J.C.MacSwell]

No, a single particle does not have a temperature. Neutrons have a magnetic moment, and should radiate.

 

"Some part of the system" at 0 implies non-equilibrium, and temperature isn't really valid under that condition. Classically, individual particles could be at rest in the system, but temperature is a collective, steady-state property. You can have negative temperatures (T<0 solution to equations of excited state distributions) when you have a population inversion, i.e. not in equilibrium.

 

If the system was my house including everything in it, I still have a temperature, yet I am not in equilibrium with the rest of the system.

 

Conservation of energy would be broken if a closed system could reach 0 Kelvin, but I cannot see how a definable isolated part of the system could not reach 0 K in classical theory, however statistically unlikely.

[swansont]

If the system was my house including everything in it, I still have a temperature, yet I am not in equilibrium with the rest of the system.

 

Conservation of energy would be broken if a closed system could reach 0 Kelvin, but I cannot see how a definable isolated part of the system could not reach 0 K in classical theory, however statistically unlikely.

 

Yes, that's true, but it would not make sense to talk of the temperature of the house system.

 

Even if, for sake of argument, some classical atoms had zero KE, they would not remain in that state — they would interact with other atoms and be bombarded with radiation.

[J.C.MacSwell]

Yes, that's true, but it would not make sense to talk of the temperature of the house system.

 

Even if, for sake of argument, some classical atoms had zero KE, they would not remain in that state — they would interact with other atoms and be bombarded with radiation.

 

Just getting their is unlikely enough, for anything approaching a recognizable amount of something (or even a small fraction of that) but classically this remote (read extremely absurdly remote) possibility still exists, and it's relatively simple to prove it.

[foodchain]

Just getting their is unlikely enough, for anything approaching a recognizable amount of something (or even a small fraction of that) but classically this remote (read extremely absurdly remote) possibility still exists, and it's relatively simple to prove it.

 

So if you had a particle that you could get to absolute zero, I don’t think you would ever be able to observe it really. What I mean is a majority of these posts basically go on about absolute zero is hard to obtain due to environmental factors, such as the earth being warmed by the sun for example. Another aspect is if you could create and environment in which absolute zero could be reached, could a observer ever exist in such a state to observe such, as in a living observer.

 

I like to read up on BEC a lot, as its interesting to me bluntly. They can get within a few millionths or billionths of a degree within absolute zero, I think the billionths actually, but then the atom for instance, or matter takes on strange properties and in some cases has imploded with large amounts of mass leaving no trace.

 

WIki of course has a really neat article on it like most anything.