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Temperature and observer velocity

  1. Apr 16, 2005 #1
    Some investigators, including Einstein and Planck, have found expressions relating temperature and the velocity of an observer . ¿ How is it possible if temperature is a thermodynamic property independent of trajectory and time?
     
  2. jcsd
  3. Apr 17, 2005 #2

    James R

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    Which expressions are you referring to?
     
  4. Apr 17, 2005 #3

    dextercioby

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    U haven't read Tolman's book,have you ? I've reccomended it to you in another thread on a similar topic...

    Please read that book first...

    Daniel.
     
  5. Apr 27, 2005 #4
    Dear dextercioby, I have read Tolman´s book . Tolman suggest that T=To[Square root(1-U2/C2)]. However, ¿ How is it possible that temperature depends on the observer velocity if temperature is a thermodynamic property ?. By definition, a thermodynamic property only depends on the state of the system and it is independent of velocity.
     
  6. Apr 27, 2005 #5

    James R

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    I don't think temperature is frame dependent. A fast cold brick is still a cold brick. It doesn't heat up just because it is going fast.
     
  7. Apr 27, 2005 #6
    I agree with you, but the equation presented in Tolman´s book suggests that temperature decreases for a frame moving at a certain velocity. When velocity tends to the velocity of light, the temperature is zero, according to above mentioned equation. Although, I am not sure, Einstein and Planck derived a similar equation, too. ¿What do you think, about it?
     
  8. Apr 28, 2005 #7

    marcus

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    suppose the brick is glowing dull red, if observed at rest

    and now suppose the brick is approaching you at 3/5 speed of light.

    wouldnt the thermal glow from the brick be doppler shifted?

    so wouldnt the light coming to you from the brick seem a lot hotter?

    But do we call the brick hotter because the thermal glow from it is hotter? I suppose it comes down to definitions of what is something's temperature, operationally------how do you plan to measure it etc.

    I would not try to respond to anyone who didnt have a URL to some source and an exact page reference so that one could easily see exactly what he was talking about

    it depends, IMO, on context so he has to provide a link to something definite online, some definite paragraph or sentence on some webpage.
     
    Last edited: Apr 28, 2005
  9. Apr 28, 2005 #8

    James R

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    I'd like to see the derivation of the equation by Einstein and/or Planck before commenting further.
     
  10. Apr 28, 2005 #9

    dx

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    Just a thought here, since some of the moleculus of a body could be moving in the direction opposite to the direction of motion of the body, the relative velocities would cancel out to some extent and would appear to you at a lesser temperature. Is that right?
     
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