This makes sense, but then again my question is motivated by the astronomical example, which still seems mysterious. Naively the various arguments and theorems

This makes sense, but then again my question is motivated by the astronomical example, which still seems mysterious. Naively the various arguments and theorems about thermal equilibrium (at least macroscopic equilibrium as you point out) would seem to apply to the situation of 10^24 bodies bouncing around and interacting gravitationally (with some feedback mechanisms into other modes)… basically like a box of billiard balls interacting mostly electromagnetically. Yet there is no “gravitational temperature” that allows one to predict the expected speed of a rock of a certain mass floating in the solar system. (Whereas knowing the temperature of a gas in a box gives good statistical information about the speed of a molecule of a certain mass in the box.) Incidentally I’ve put some version of this question to four different physicists and gotten four different replies! (“Chaos” being one of these :) )