The stars are spherical. So are the planets. Galaxies are seemingly circular on a flat plane. Atoms are spherical, and so are cells within our bodies. The orbits are circular, and if the universe expanded in all directions equally from a singularity, then the universe itself must be spherical...
As I've research M Theory, I've read that in the 11th dimensional framework, gravity is leaking into the 11th dimension, losing its strength. The 11th dimension is said to be where parallel universes coexist, so that would imply that gravity is leaking out and being shared between universes...