* Thermal Equilibrium: Two bodies are in thermal equilibrium when they have the same temperature. Temperature is a measure of the average kinetic energy of the particles within a system.
* Inertial Frames: Inertial frames of reference are those where an object at rest remains at rest, and an object in motion continues in motion at a constant velocity unless acted upon by a force.
* Relativity: The laws of physics are the same in all inertial frames. This includes the laws of thermodynamics, which govern the flow of heat and the concept of temperature.
Therefore, if two bodies have the same average kinetic energy in one inertial frame, they will also have the same average kinetic energy in all other inertial frames. This means their temperatures will be the same, and they will remain in thermal equilibrium.
Important Note: This applies to inertial frames. If you're considering non-inertial frames (like rotating or accelerating frames), the situation becomes more complex. In those cases, the concept of temperature and thermal equilibrium can be affected by the forces involved.
