I have designed this simple thought experiment that seems to contradict 2nd law of thermodynamics. Could you please find a mistake in my reasoning?
Fixed box with reflective (white) walls ________ ___________ | | | | | | | | | |_______ | __________| ^ This part is free to move horizontally and is black on the left and white on the right side
In the right half of the box we don't have any photons since box is completely white inside and the moving part is white on its right side. The left part however is filled with bouncing photons as they are emitted by the left side of the movable wall which is black.
According to my reasoning the moving part should move to the right because of the radiation pressure. Photons will lose energy due to doppler effect.
Since every part of the device is at the same temperature movement of the wall inside would contradict 2nd rule of thermodynamics.
Whole device is in the vacuum box which in turn is placed on a table in a laboratory.