How Do Thermodynamic Quantities Change at Speeds Close to Light?

In summary, the conversation discusses the issue of how thermodynamic quantities change when the system is moving at a velocity comparable to the speed of light. Textbooks often avoid this problem by analyzing in the local rest frame, but other approaches exist. A recommended paper by Van Kampen and Israel presents a short but controversial history of this topic. However, the speaker is unable to comment on the popularity of this approach or the topic in general, and hopes for input from others.
  • #1
ashishk
1
0
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
 
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  • #2
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.
 
  • #3


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.
 

Related to How Do Thermodynamic Quantities Change at Speeds Close to Light?

1. What is the relationship between thermodynamics and relativity?

Thermodynamics and relativity are two fundamental theories in physics that describe different aspects of the universe. Thermodynamics deals with the study of energy and its transformations, while relativity explains the relationship between space and time. However, both theories are interconnected as Einstein's theory of relativity has been applied to explain the behavior of energy in thermodynamic systems.

2. How does relativity affect thermodynamic processes?

Relativity plays a significant role in thermodynamics by introducing the concept of space-time, which states that time and space are relative and can vary depending on the observer's frame of reference. This concept is crucial in understanding the behavior of energy in extreme conditions, such as near black holes, where the effects of relativity are more pronounced.

3. Can thermodynamics be explained using relativity?

While relativity has been successfully applied to explain thermodynamic processes in extreme conditions, it cannot fully explain all aspects of thermodynamics. Thermodynamics is a macroscopic theory that deals with the overall behavior of a system, while relativity is a microscopic theory that explains the behavior of particles at the atomic and subatomic level. Both theories are essential in understanding the universe.

4. What is the role of thermodynamics in the theory of relativity?

Thermodynamics plays a crucial role in the development of the theory of relativity. It provides a framework for understanding the behavior of energy and matter, which is a fundamental concept in relativity. Additionally, thermodynamics has been used to validate some of the predictions made by the theory of relativity, such as the existence of black holes.

5. How does the second law of thermodynamics relate to the theory of relativity?

The second law of thermodynamics states that the total entropy of a closed system will never decrease over time. This law is consistent with the theory of relativity, which predicts that the universe is always moving towards a state of maximum disorder or entropy. This relationship between the two theories has been used to explain the behavior of energy in the expanding universe and the existence of cosmic microwave background radiation.

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