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Every Planet’s Temperature Fits on One Line of Algebra
Balance sunlight in against infrared out and Earth comes back 33 degrees too cold — the gap is the greenhouse effect.
A planet hanging in space is, thermodynamically, a very simple object. It has exactly two ways to trade energy with the rest of the universe: it soaks up starlight on the side that faces its star, and it glows thermal infrared from its whole surface, in every direction, all the time. Nothing else counts. Radioactivity in the core, tides, the slow leak of heat left over from formation — for a planet like Earth these are rounding errors against the flood of sunlight arriving and the flood of infrared leaving. Strip a world down to those two transactions, insist that they balance, and something remarkable falls out: a single line of algebra that predicts the equilibrium temperature of any planet in the solar system, and of any planet around any star, from nothing but its distance from that star and how shiny it is.
The claim sounds too cheap to be true. A planet’s climate is the product of oceans and jet streams and ice caps and volcanic chemistry, a system so tangled that forecasting next week’s weather taxes the largest computers ever built. And here is a promise to price the whole thing with two numbers and a fourth root. The honest…
