In 1863, in “ON THE CONCENTRATION OF RAYS OF HEAT AND LIGHT, AND ON THE LIMITS OF ITS ACTION”, Clausius wrote in the conclusion:
To harmonize the effects of ordinary radiation, without concentration, with the principle that heat cannot of itself pass from a colder to a warmer body, it is necessary to assume that the intensity of emission from any body depends not only upon its own constitution and its temperature, but also upon the nature of the surrounding medium ; in fact the intensities of emission of one and the same body in different media must be inversely proportional to the squares of the velocities with which rays are therein propagated, or, in other words, directly proportional to the squares of the coefficients of refraction for these media.
[pdf accessible here]
In my searching of and reading about blackbody radiation, I haven’t come across this in modern resources.
Did this end up being true? If not then what disproved it and how was the second law of thermodynamics preserved - ie where did Clausius go wrong in his reasoning?
