Britannica Sources used in this answer

How did Einstein’s theory of general relativity explain Mercury’s orbit?

Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.

Messenger: Mercury — Mercury Mercury as seen by the Messenger probe, January 14, 2008. This image shows half of the hemisphere missed by Mariner 10 in 1974–75 and was snapped by Messenger's Wide Angle Camera when it was about 27,000 km (17,000 miles) from the planet.

Albert Einstein’s general theory of relativity explained the orbit of Mercury by redefining the nature of gravity.12

While Isaac Newton’s law of universal gravitation successfully accounted for most of the precession of Mercury’s perihelion—the point in its orbit closest to the Sun—there remained a small, unexplained discrepancy of approximately 43 arc seconds per century. In the 19th century, this led some astronomers to hypothesize the existence of an undiscovered planet, often called Vulcan, orbiting closer to the Sun to account for the perturbation.13452

Einstein’s 1915 theory replaced the Newtonian view of gravity as a force acting across space with the concept of mass causing a curvature in the fabric of space-time. By applying this framework, Einstein was able to calculate the shift in Mercury’s perihelion from first principles, precisely predicting the observed motion without the need for additional, hypothetical planets. This success served as a critical observational verification of general relativity.2513