What did Newton understand that was such a revolution? Can someone just... explain gravity to me? Let's start with a ...

Besides quantum theory, general relativity is one of two pillars of modern physics – our working theory of gravity and of the very large, of planets, galaxies and the universe as a whole.

The trouble boils down to gravity. It’s the only one of the four fundamental forces of nature described by general relativity, and the only one that quantum theory cannot address. Coming up with ...