The sun and planets in the solar system are used to help propel and guide spacecraft to their ultimate destinations. These bodies provide "gravity assists," commonly called "slingshot" trajectories, ...
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.
In our introduction to general relativity, we explain how this theory developed, plus how it explains the motion of the planets, the history and expansion of the universe and the physics of black ...