Thermal equilibrium versus pressures

1. Feb 7, 2009

intervoxel

Is it possible for a closed system in thermal equilibrium possess two regions with different pressures supposing such regions had the same pressure in the past?

2. Feb 7, 2009

Mapes

It's required by atomic theory and thermodynamics. "Pressure" is just the average force per unit area from the bombardment of vast numbers of atoms; thus, random fluctuations are inevitable. Two regions of equal pressure at one instant can hardly avoid having different pressures at the next instant, due to atomic motion. The larger the system, however, the smaller the deviations from the average value. On the human scale, these deviations are essentially unmeasurable.

3. Feb 7, 2009

atyy

Does the question require that the system was in thermal equilibrium when it consisted of a single region of uniform pressure?

4. Feb 7, 2009

intervoxel

No, it is supposed they had different temperatures in the past.