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Thread: absolute zero

  1. #1 absolute zero 
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    Does a state of absolute zero actually exist?
    Whether it does or not what happens to quarks and electrons? I imagine that an electron falls into the nucleus, but are the quarks still held by the strong force?


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  3. #2 Re: absolute zero 
    Forum Ph.D. Leszek Luchowski's Avatar
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    Quote Originally Posted by greymatt
    I imagine that an electron falls into the nucleus
    No it does not. It stays in its orbit.

    But this brings me to a funny question: what is the temperature of a single atom drifting through the vacuum of space?


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  4. #3  
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    Yes. It is possible.
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    temperature of a single atom in space is 3K. Temperature is the average amount of kinetic energy so the temperature of space is going to be the average amount of kinetic energy of the atoms occupying it.
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  6. #5 Re: absolute zero 
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    Quote Originally Posted by greymatt
    Does a state of absolute zero actually exist?
    Whether it does or not what happens to quarks and electrons? I imagine that an electron falls into the nucleus, but are the quarks still held by the strong force?
    It depends on what you mean by "exist". It is a clearly defined state of a an ensemble of particles. It is also not accessible. You can't get there from here --
    the third law of thermodynamics.

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

    http://en.wikipedia.org/wiki/Third_l...thermodynamics
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  7. #6  
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    Quote Originally Posted by Nevyn
    temperature of a single atom in space is 3K. Temperature is the average amount of kinetic energy so the temperature of space is going to be the average amount of kinetic energy of the atoms occupying it.
    It's fine to talk about the average temperature of particles in space, but I'm not sure it's meaningful to talk about the temperature of a single free atom. I guess you could look at the relative velocity of the atom and see what temperature that velocity would correspond to if you had a collection of similar atoms that were all going that fast, but I'm not sure that would really count as it having a "temperature".
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  8. #7  
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    Quote Originally Posted by Scifor Refugee
    Quote Originally Posted by Nevyn
    temperature of a single atom in space is 3K. Temperature is the average amount of kinetic energy so the temperature of space is going to be the average amount of kinetic energy of the atoms occupying it.
    It's fine to talk about the average temperature of particles in space, but I'm not sure it's meaningful to talk about the temperature of a single free atom. I guess you could look at the relative velocity of the atom and see what temperature that velocity would correspond to if you had a collection of similar atoms that were all going that fast, but I'm not sure that would really count as it having a "temperature".
    Yeh thats what I was going to put at first, but then I thought that it's only the mean so that if you draw a distribution curve the most probable amount of kinetic energy that a molecule has is going to be at the middle which is why it's an average. If you take the average energy you can still convert into a temperature with
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  9. #8  
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    Quote Originally Posted by Scifor Refugee
    Quote Originally Posted by Nevyn
    temperature of a single atom in space is 3K. Temperature is the average amount of kinetic energy so the temperature of space is going to be the average amount of kinetic energy of the atoms occupying it.
    It's fine to talk about the average temperature of particles in space, but I'm not sure it's meaningful to talk about the temperature of a single free atom. I guess you could look at the relative velocity of the atom and see what temperature that velocity would correspond to if you had a collection of similar atoms that were all going that fast, but I'm not sure that would really count as it having a "temperature".
    Don't single particles vibrate on their own and is the frequency not indicative of the temperature of that particle?
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  10. #9  
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    Quote Originally Posted by KALSTER
    Quote Originally Posted by Scifor Refugee
    Quote Originally Posted by Nevyn
    temperature of a single atom in space is 3K. Temperature is the average amount of kinetic energy so the temperature of space is going to be the average amount of kinetic energy of the atoms occupying it.
    It's fine to talk about the average temperature of particles in space, but I'm not sure it's meaningful to talk about the temperature of a single free atom. I guess you could look at the relative velocity of the atom and see what temperature that velocity would correspond to if you had a collection of similar atoms that were all going that fast, but I'm not sure that would really count as it having a "temperature".
    Don't single particles vibrate on their own and is the frequency not indicative of the temperature of that particle?
    Temperature is the reflection of the kinetic energy of translation of molecules. The "vibrational" modes contribute to internal energy but not to temperature.

    Temperature of a system is basically a statistical concept, as is thermodynamics. So, while you mght justifiably define the temperature of a single particle as its kinetic energy, you can't relate that to the usual thermodynamics ideas regarding temperature. Note also the clear dependence of the kinetic energy on reference frame.
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  11. #10  
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    Quote Originally Posted by DrRocket
    Note also the clear dependence of the kinetic energy on reference frame.
    Precisely the reason why I thought the question was worth asking.
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  12. #11  
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    Quote Originally Posted by Leszek Luchowski
    Quote Originally Posted by DrRocket
    Note also the clear dependence of the kinetic energy on reference frame.
    Precisely the reason why I thought the question was worth asking.
    Actually the answer demonstrates why that particular question is not very meaningful.

    We have a perfectly good notion of the kinetic energy of a particle. The only compelling reason for the concept of "temperature" is the extreme difficulty in determining and describing the state of each and every particle in a large collection of interacting particles -- basically the fact that the n-body problem is not solvable for n>1. But it is possible to treat a large number of interacting particles statistically, and the average kinetic energy is called "temperature" (within a constant multiple). The study of the statisical behavior of large numbers of particles is calle thermodynamics. Temperature is one state variable used in that discipline.

    There is no particular point in discussing "temperature" of a single particle. The statistics are decidedly uninteresting. You don't need statistical methods and in particular the machinery of thermodynamics is not applicable.
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    Would it be fair to suggest that the particles need to be moving back and forth in order to count as heat? I mean that statistically, there has to be about as many particles moving North as there are South, over a given length of time.

    If all of the particles in a system are all moving in the same direction, I don't think we would call that "heat".
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  14. #13  
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    Quote Originally Posted by kojax
    Would it be fair to suggest that the particles need to be moving back and forth in order to count as heat? I mean that statistically, there has to be about as many particles moving North as there are South, over a given length of time.

    If all of the particles in a system are all moving in the same direction, I don't think we would call that "heat".
    You need to be quite careful about what you call heat and what you call temperature.

    That is one reason that in the thermodynamics of gas dynamics one distinguishes between static temperature (the temperature that you would measure moving along with the flow) and stagnation temperature ( the temperature that would be measured if the flow velocity were reduced to zero isentropically).

    Temperature is quite simply the kinetic energy of translation of molecules and it is dependent on your reference frame as reflected in the difference between static temperature and stagnation temperature. And that difference is precisely due to the energy of molecuesl "all moving in the same direction".

    And you are correct, you don't call that heat. Heat is a different thing entirely. Heat includes internal energy that is not kinetic energy of translation, but involves other modes as well.
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  15. #14  
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    Quote Originally Posted by KALSTER
    Don't single particles vibrate on their own and is the frequency not indicative of the temperature of that particle?
    No, a single free particle won't necessarily have a frequency. It has to be confined in some way (perhaps in a box).
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  16. #15  
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    Quote Originally Posted by Scifor Refugee
    Quote Originally Posted by KALSTER
    Don't single particles vibrate on their own and is the frequency not indicative of the temperature of that particle?
    No, a single free particle won't necessarily have a frequency. It has to be confined in some way (perhaps in a box).
    The frequency of a particle, constrained or not, is described by the deBroglie equation, which relates frequency to energy and wavelength to momentum.

    http://en.wikipedia.org/wiki/Matter_wave
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  17. #16 Re: absolute zero 
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    Is there really a vacuum in space?
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  18. #17 Re: absolute zero 
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    Quote Originally Posted by greymatt
    Is there really a vacuum in space?
    It depends on what you mean by a vacuum.

    Deep space has a near vacuum that is far nearing to "nothing" than anything that can be produced in an earth-bound laboratory. It is not perfect, but it is quite close.

    Quantum field theory shows that a vacuum actually has energy, in the form of a zoo of virtual particles that wink in and out of existence very quickly. So a vacuum is more complicated than simply "nothingn".
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  19. #18  
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    good question, for anything to be in any form of motion it must have energy, for an atom to have energy it must have heat
    therefore in absolute zero conditions all the components of an atom would stop moving

    that said electromagnetic forces do not require heat to work (as far as I know) so the electrons wouldn't collpase into the nucleus, rather it would hover above it (like you can make one magnet hover in the air over a second)



    As far as I know Absolute zero is a purely man made state, since Space itself is not absolute zero any natural enviroment at Absolute Zero would actually be warmed by space
    Space would be Absolute Zero were it not for the 3 degrees of heat left over from the big bang (yup it was BIG )
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  20. #19  
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    Can any atomic particle be a virtual particle? Do virtual particles provide a hint that all atoms are really loops of time? I'm thinking of Mark Hadley here, although I don't understand the theory.
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