In contrast to my usual practice, this time I'm putting the blog entry's image at the bottom of the page. Pretty wild and crazy of me, eh? Resuming discussion of the same law we discussed yesterday. As a historical observation, it has its name because Jozef Stefan inferred it from experimental evidence in 1879, five years before Ludwig Boltzmann derived it in theoretical fashion. The law is of considerable importance to certain contemporary issues, because the Earth itself, including its atmosphere, can be considered for purposes of prediction as a "gray box" of the sort I discussed in the last post. If we know how much radiation the earth is receiving from the sun, and we know how much of that energy is reflected away, vis-à-vis how much is absorbed, we should be able to say something about the heat of this box, this planetary system, as a whole. The International Panel on Climate Change says that 30% of the sun's energy is reflected away, the remainder is...