Interesting point. If you use a standard frame in which to measure accelerations (say the average position of all the visible stars), then the acceleration toward the Earth does not depend on the mass of the falling object, at least so long as Newton's gravity is a decent approximation.
However, as you point out, there's another acceleration going on- the small acceleration of the Earth toward the elephant. That means that, even ignoring air resistance, the Earth and elephant would collide a little sooner than the Earth and feather would. In that sense (basically measuring accelerations relative to the Earth), the elephant falls faster.
Mike W.
(published on 10/22/2007)
