NOVA Black Hole Apocalypse Astronomy Practice Test

Gravity is the idea that shapes everything from planetary orbits to the light that travels across the cosmos, and for a long time, people wrestled with what gravity actually is and how it works. Newton showed gravity as a force that pulls masses together, which fits everyday scales but leaves open why such a force exists and how it operates in extreme situations. The big shift comes with general relativity, which reframes gravity as the curvature of spacetime caused by mass and energy. Objects move along these curved paths, and light bends and time runs differently because of this geometry. This deeper view explained many phenomena and turned gravity from a mysterious force into a predictable, geometric property of spacetime. So, according to Levin, the fundamental question of how gravity works stood as one of the greatest mysteries for a long time.