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How did general relativity explain Mercury’s changing perihelion?

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Brian Greene sits in a living room, holding a pen, with handwritten equations m = E/c^2 and E = mc^2 on a whiteboard beside him, highlighting c^2 as the speed of light. — relativity Brian Greene kicking off his *Your Daily Equation* video series with Albert Einstein's famous equation E = mc².

General relativity explains the changing perihelion of Mercury by redefining the nature of gravity. While Isaac Newton’s classical mechanics successfully accounted for most of the planet's orbital precession through the gravitational influence of other planets, a small residual discrepancy of 43 arc seconds per century remained unexplained.123

In 1915, Albert Einstein demonstrated that this movement was not caused by an undiscovered planet, as previously hypothesized, but by the geometry of space-time itself. According to the general theory of relativity, gravity is not a force acting across space, but rather the result of mass causing a curvature in the fabric of space-time.24

Because Mercury orbits very close to the Sun, it moves through this warped space-time, which causes its orbit to precess at a rate that Newtonian physics could not predict. Einstein’s precise calculation of this effect from first principles provided a major observational verification of his theory, marking a significant departure from and refinement of Newtonian gravitational theory.254