Temperature and observer velocity

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Discussion Overview

The discussion revolves around the relationship between temperature and the velocity of an observer, questioning how temperature, a thermodynamic property, can be influenced by the observer's motion. The scope includes theoretical considerations and interpretations of expressions from notable physicists like Einstein and Planck, as well as references to Tolman's work.

Discussion Character

  • Debate/contested
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • Some participants reference expressions from Einstein and Planck that relate temperature to observer velocity, questioning the validity of these relationships given that temperature is traditionally viewed as independent of trajectory and time.
  • One participant cites Tolman's equation, T=To[Square root(1-U2/C2)], and expresses confusion about how temperature can depend on observer velocity if it is a thermodynamic property.
  • Another participant argues that temperature is not frame dependent, using the example of a fast cold brick that does not change its temperature simply due to its speed.
  • There is a discussion about the implications of Doppler shifting on the perceived temperature of an object, suggesting that the thermal glow of a moving object may appear hotter due to relativistic effects, raising questions about the definitions of temperature.
  • One participant expresses a desire to see the derivation of the equations by Einstein and Planck before further commenting on the topic.
  • A thought is presented regarding the relative motion of molecules within a body potentially leading to a perceived lower temperature due to opposing velocities.

Areas of Agreement / Disagreement

Participants generally disagree on the relationship between temperature and observer velocity, with multiple competing views presented. There is no consensus on whether temperature is frame dependent or how to interpret the equations cited.

Contextual Notes

Participants reference specific equations and concepts from theoretical physics without resolving the underlying assumptions or definitions of temperature in different frames of reference.

Iraides Belandria
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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?
 
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Which expressions are you referring to?
 
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.
 
dextercioby said:
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.

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.
 
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.
 
James R said:
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.

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?
 
James R said:
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.

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 wouldn't 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:
I'd like to see the derivation of the equation by Einstein and/or Planck before commenting further.
 
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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