The Newtonian approach was unable to explain where gravitational potential energy came from, but even so remains an exceptionally good approximation for most everyday situations. It is not, however, able to properly describe the planet Mercury s orbit. Our modern understanding of how gravity operates comes from Relativity Theory and shows us why Mercury s orbit is unusual. Click here for the details.
Funny things happen under extreme gravity.
Although we think of gravity as being a weak force, if the mass is large enough the effect can be impressive. In a neutron star matter is compressed so much that atoms are compressed themselves are compressed into a minuscule fraction of their normal volume. With black holes gravity is so massive that light cannot escape. Click here for details. The farther we see out into the universe, the greater the light we see is shifted towards the red.