"The earth isn't going to run out of heat"<br>Entropy would say otherwise,(reply>), I literally corrected him out loud "any time soon",(reply>), @jetison333 Congrats, you just discovered the basic idea of "global warming",(reply>), @TMad LegionSoul For all intents and purposes, we can be said to be in equilibrium.  Recent warming of the atmosphere vs true equilibrium is negligible in terms of energy.  Not quite sure if you're confused or trying to be pedantic to the point of being obnoxious.,(reply>), By the time the earth's cooling becomes a problem, humanity will be LONG gone. So will the earth as a matter of fact. Current estimates predict the earth's core won't be completely cooled for 91 BILLION years. In contrast, the sun will have expanded into a red giant, engulfed the earth, then died out, in only around 5 billion.,(reply>), 3 fold material conditions: creation maintenance destruction. Infinitely.