On 17 Aug 2001, at 16:17, An Metet wrote:
But, in the case described the two bodies start out at the same temperature. One radiates more energy towards the other one at that particular temperature. So, you would expect that one body would become hotter than the other.
The important fact that you seem to be unaware of is that the body that radiates faster also absorbs more (reflects less). A black plate will radiate faster than a white one, but the white plate is reflecting almost all the light that hits. Cavity radiation and blackbody radiation are used synonymously. George
From the hints you've dropped I see the general outline of the solution. The photons going between the two blocks of metal will "thermalize" and the volume between the two blocks will look like the inside of a cavity. The rate of energy transfer in each direction will then be the same.
In fact, if the two blocks were contained in a large thermos which perfectly reflected the photons, the same effect would occur. It would be like an inside out cavity. Each block would end up at the same temperature. (Perhaps slightly lower than the start temperature because it must take some energy to fill the space with thermalized photons.)