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General relativity explains the small part of Mercury’s perihelion advance that Newtonian calculations leave unexplained: about 43 arcseconds per century. The planets’ gravitational effects account for most of the orbit’s total precession; the Sun’s effect on spacetime accounts for the remaining historical discrepancy.
What is Mercury’s perihelion, and what does it mean for it to advance?
Perihelion is the point in Mercury’s orbit closest to the Sun. Mercury travels on an ellipse, and its perihelion advances when the orientation of that ellipse gradually shifts. The orbit does not simply repeat in exactly the same direction each time around the Sun.
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Why does Mercury’s orbit precess?
There are two important contributions to the advance. The other planets exert gravitational forces on Mercury, perturbing its orbit and explaining most of the precession. General relativity adds a smaller contribution because the Sun’s mass curves spacetime, changing the path Mercury follows. The relativistic contribution is not the whole observed rotation of the orbit.
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1Fix the driver behind crashes, sound loss and screen glitches2Clear out junk files and repair common Windows errors3Scan for outdated or missing drivers - takes under a minute| Contribution | Cause | Approximate advance per century | What it explains |
|---|---|---|---|
| Planetary perturbations | Gravitational influence of other planets | About 531 arcseconds per century (OpenStax); approximately 531.63 arcseconds per Julian century in a NASA MESSENGER analysis | Most of Mercury’s total perihelion precession |
| Relativistic contribution | The Sun’s effect on spacetime geometry, described by general relativity | About 43 arcseconds per century (NASA); approximately 42.98 arcseconds per Julian century in a NASA MESSENGER analysis | The residual not explained by the Newtonian planetary calculation |
These figures are approximate and come from sources that state their units slightly differently: the MESSENGER analysis reports values per Julian century. They describe distinct contributions, not interchangeable measures of the same part of the motion. OpenStax Astronomy 2e gives the rounded comparison; NASA’s Planetary Geodesy Data Archive and the 2018 MESSENGER analysis in Nature Communications report the more precise figures.
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How does general relativity produce the extra advance?
In Newtonian gravity, Mercury’s motion is calculated under the Sun’s attraction and the perturbations from other planets. That accounts for most of the measured precession, but leaves a small, systematic residual. General relativity describes gravity in terms of spacetime geometry: the Sun’s mass curves spacetime, and Mercury’s orbit through that curved geometry receives an additional advance.
This is an effect of general relativity, not a special-relativistic correction. Stanford’s Gravity Probe B FAQ distinguishes the two theories. NASA likewise describes the Sun’s role as warping spacetime in its account of tracking Mercury.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Was Mercury’s anomaly discovered after Einstein’s theory?
No. The unexplained advance was a problem in celestial mechanics before general relativity provided its explanation. That made Mercury’s orbit an important early test of Einstein’s theory; the anomaly was not a motion first observed after the theory was proposed. NASA’s Mercury facts resource describes the relativistic explanation without requiring an extra planet, while the National Academies’ account of the history discusses the earlier problem.
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