What is spacetime curvature?

In Einstein’s general relativity, gravity is not a force acting at a distance in the Newtonian sense. Instead, mass and energy bend the fabric of spacetime, and objects follow the curved paths, or geodesics, created by that geometry. This is why planets orbit the Sun and why light bends near massive bodies. The theory was confirmed by observations such as the 1919 eclipse measurement of starlight deflection and later by studies of gravitational lensing and GPS timing corrections. Spacetime curvature is central to modern astrophysics, from black holes to gravitational waves.