Originally Posted by mib
Take the Moon, for example. It is phase-locked with the Earth -- we never see "the dark side" (it is not really always dark, of course). Why does not the same thing happen with the Earth with respect to the sun?
Tidal locking is a consequence of distance, the bodies' masses, and time. Although the moon is much smaller than the sun, its closer proximity means it exerts a greater tidal influence overall (about 2.5x greater, as far as I remember), so the moon has been locked to the earth first.