The position at which I eventually arrived was something like this:

Outside; greater density of matter leading to greater gravitational attraction.

Inside; lower density of matter leading to lower gravitational attraction.

Matter tends to move from area of lower attraction to area of higher attraction, so dense areas will become more dense, while less dense areas become even less dense.

With increasing density outside, relative to inside, outward motion will accelerate.

Posts so far suggest that reaction to this will be mixed.

There never was nothing.