Whereas Newton imagined gravity as a force that acts across space, Einstein’s equations cast gravity as a property that belongs to space. In Newton’s physics, space was passive, a vessel for a mysterious force between masses. In Einstein’s physics, space was active, collaborating with matter to produce what we perceive as gravity’s effects. The Princeton physicist John Archibald Wheeler offered possibly the pithiest description of this co-dependence: “Matter tells space how to curve. Space tells matter how to move.”
