General Relativity

General relativity is Einstein's description of gravity, not as a force pulling objects together, but as the geometry of spacetime itself bending around mass and energy. A planet does not orbit a star because something tugs on it; it follows the straightest possible path through a spacetime the star has curved. The theory has survived over a century of increasingly precise tests, from the bending of starlight during a solar eclipse to the direct detection of gravitational waves from colliding black holes a century after they were first predicted. It is also the framework that makes black holes, the expansion of the universe, and the slowing of time near massive objects not just possible but mathematically necessary. This page collects Astrinova's reporting on the field, from its foundational ideas to the experiments still testing its limits today.