About Ensemble Average for gas molecules(classical mechanics regime)

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Ensemble averages in classical mechanics relate macroscopic fluid variables to the averages of microscopic gas molecule variables. When time averages equal spatial averages, the system is considered ergodic. The discussion raises the question of whether different microscopic variables with the same average, such as center of mass and momentum, can represent the same macroscopic state. It emphasizes that while microstates are unique configurations, multiple microstates can correspond to the same macrostate if they share the same ensemble averages. This relationship is crucial for understanding entropy and thermodynamic principles.
Noh-hoon Lee
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I have some question about Ensemble Average.

The macroscopic variable of fluid is average of microscopic variable of gas molecule.

And if time average is same with spatial average I know as it called edgodic.

My question is that if two different microscopic variables which have same average value, like center of mass, momentum, translational energy, (angular momentum has some error but it is very small so I ignore it.(it is acceptable error))

Does it can be seen as a same state for macroscopic view?
 
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Every microstate is unique configuration of particle states and. In pursuit of thermodynamics, we say that there are many different microstates for the same macrostate, so long as they have the same ensemble averages. The number of microstates for a given macrostate determines its entropy, and from there, all the rest of thermodynamics can follow.


Noh-hoon Lee said:
I have some question about Ensemble Average.

The macroscopic variable of fluid is average of microscopic variable of gas molecule.

And if time average is same with spatial average I know as it called edgodic.

My question is that if two different microscopic variables which have same average value, like center of mass, momentum, translational energy, (angular momentum has some error but it is very small so I ignore it.(it is acceptable error))

Does it can be seen as a same state for macroscopic view?
 
thank you for your reply :) It's really helpful
 
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