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How does general relativity explain gravity?

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Portrait of Albert Einstein in a suit and tie, looking slightly to the side with a neutral expression. — Albert Einstein Albert Einstein developed the special and general theory of relativity, which recast gravity as a bending in space-time.

In general relativity, Albert Einstein redefined gravity not as a force, as Isaac Newton had proposed, but as a geometric phenomenon arising from the curvature of space-time.12

This theory posits that massive objects, such as stars or planets, deform the fabric of space-time, creating a curvature similar to a heavy weight placed on a rubber sheet. Rather than being pulled by an invisible force, objects and light follow the shortest natural paths through this curved geometry, known as geodesics. As physicist John Wheeler famously summarized, "matter tells space-time how to curve, and space-time tells matter how to move".13

This framework is governed by the Einstein field equations, which relate the distribution of mass and energy to the geometry of space-time. The theory has been confirmed through various observations, including the deflection of starlight, the orbit of Mercury, gravitational time dilation, and the detection of gravitational waves.342