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Stefan-Boltzmann Law, Part II

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 absorbed. It makes intuitive sense to suppose that the content of the atmosphere changes that percentage. Given certain atmospheric changes, the earth will absorb more of the radiation and absorb it.

Until a couple of years ago this sort of thing was known as the "greenhouse effect." But people who believe that most of us are inadequately alarmed about such matters recently stopped using the term, because they figure a "greenhouse" sounds like a nice comfortable and beautiful place to live, so the term frames the discussion in a skewed way.
Don't look for some sweeping conclusion here. I've already made my views on global warning known on this blog and elsewhere. 
I simply wanted to clarify for myself what this Stefan-Boltzmann reference was all about, in case that impressive term swims within my ken again.


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