[AaronBrown]

CallMeIshmael and Alan3 have defined the two extremes. The resolution depends on how you define "strategy." Alan3's orbiting non-equibria could be defined as a strategy, in which case a Nash equilibrium should exist, or the orbits could be defined as constantly changing strategies with no equilibrium. Is the solar system in equilibrium because the orbits are stable (maybe, anyway) or in constant nonequilibrium as gravity battles momentum?

As a practical matter, the important thing is how to do calculations. If you want to know where the Earth will be in a month, you just trace its orbit (that is, you treat the solar system as in equilibrium). If you want to know where the Earth will be in a second or a million years, you have to simulate all the bodies in the solar system (that is, you treat it as something constantly changing).