On Mon, 11 Oct 2010 07:51:19 -0700 (PDT), Rick Cavallaro
wrote:

If we're still imagining the air cloud to be a shell with nothing in
the middle (i.e. the place where the earth is missing), objects would
not sink to the middle of that void. There's no gravity inside a
uniform shell of any thickness.

But wouldn't the stuff outside the shell move down, er, midpointwards, under the
influinece of gravity, and then continue on to the middle, i.e. the shell fill
up eventually?

Thomas Prufer