well the question I have is about black bodies and it says that we have one black body (nonreflecting) at temperature Tu and another black body at temperature T1 (they are parallel and in a vacuum.) The energy flux between them is (Tu^4 - T1^4)*Stefan-Boltzman's constant and the question wants to know if I place a third plate and allow it to come to steady state temperature what temperature will the middle plate be at and to also show that the flux is exactly half). The temperature part is easy I think. The temperature of the middle plate should be the average of the two plates. That's the only way I could think of finding this new temperature given how little we know about the problem. The problem I have though is how would I show that the "net energy flux density" is cut in half. Especially since I'm not really sure what it is in the first place (my book kind of glosses over how to find it and what it is.) Thanks in advance for any help.