How Do Thermodynamic Quantities Change at Speeds Close to Light?

[ashishk]

hi;
I want to know how thermodynamic quantities T,P, H change if the system is moving with respect to the frame of reference of observation with velocity which is comparable to the velocity of light.
ashish arya

 

[pervect]

Looks like my first post got eaten. To recap:

1) Most of the textbooks I use actually sidestep the problem, by analyzing the thermodynamics in the local rest frame of whatever fluid exists, so that they don't have to consider the issue at all.

2) Other approaches exist. I'm rather fond of http://arxiv.org/abs/physics/0505004 myself. The paper has a reference list of some other approaches, and mentions that the topic has a "long and controversial history". The particular approach used by this paper is based on an approach pioneeered by Van Kampen and Israel. One of the things I like about this paper is that it is very short.

3) Unfortunately I can't personally comment on the relative popularity of the approach in the paper I cite above vs other approaches to covariant formulations of thermodynamics (such as those mentioned in the reference list of this paper for instance). Nor can I say much about the "controversial history" of the topic - thermodynamics isn't one of my main interests. In the past, where this question has arisen before, we haven't had many comments from other posters on these topics either. I hope we can get Chris Hillman to say a few words about these issues.

 

[Entropia]

The principles of thermodynamics and relativity are both fundamental theories in physics that have been extensively studied and applied in various fields. However, when it comes to systems moving at velocities comparable to the speed of light, the behavior of thermodynamic quantities such as temperature (T), pressure (P), and enthalpy (H) becomes more complex and requires a deeper understanding of both theories.

In classical thermodynamics, these quantities are considered to be absolute and independent of the observer's frame of reference. This means that regardless of the system's motion, the values of T, P, and H would remain the same. However, in the theory of relativity, the laws of physics are observed to be the same for all inertial frames of reference, but the measurements of quantities can vary for different observers.

When a system is moving at velocities close to the speed of light, the effects of relativity become significant and can cause changes in the thermodynamic quantities. This is because at these velocities, the mass and energy of the system are no longer independent and are related through the famous equation E=mc². As a result, the system's mass and energy will change, and this will affect the thermodynamic quantities.

For instance, as the system's velocity increases, its mass will also increase, and this will lead to an increase in its energy. This increase in energy will then affect the temperature of the system, causing it to rise. Similarly, the pressure and enthalpy of the system will also be affected by the changes in energy and mass.

Moreover, at very high velocities, the effects of relativity on the thermodynamic quantities become more pronounced. According to the theory of relativity, the length and time measurements of an object are affected by its velocity, which can further impact the measurements of T, P, and H.

In conclusion, the behavior of thermodynamic quantities T, P, and H can change significantly for systems moving at velocities comparable to the speed of light due to the effects of relativity. To accurately describe and analyze such systems, a combination of both thermodynamics and relativity is necessary. This is an active area of research, and further studies are needed to fully understand the behavior of these quantities in such extreme conditions.