View source for Perihelion Precession of Mercury

The '''perihelion precession of Mercury''' is the slow rotation of the planet's elliptical orbit within its own plane. After every known Newtonian effect is subtracted, a residual advance of about 43 arcseconds per century remains &mdash; the single most-cited empirical test in the relativity literature, and on this wiki.

==The standard account==

Mercury's perihelion advances by roughly 5,600 arcseconds per century as measured against the equinox. About 5,025 of that is an artefact of the precession of Earth's equinoxes; a further 530 or so comes from the gravitational pull of the other planets, chiefly Venus, Jupiter and Earth. Urbain Le Verrier found in 1859 that a residue remained unaccounted for, and proposed an intra-Mercurial planet, Vulcan, to explain it. Simon Newcomb's more careful reduction in 1882 put the residue at about 43 arcseconds per century, and Vulcan was never found.

In November 1915 Einstein derived from [[General Relativity]] an additional precession of 43 arcseconds per century for Mercury, with no adjustable parameter. The agreement was immediate and exact, and it was the first success of the theory. The same formula gives much smaller but now-measured advances for Venus, Earth and the asteroid Icarus, and far larger ones for binary pulsars, where periastron advance is measured to high precision.

==Gerber's 1898 derivation==

A genuine and awkward historical fact, well documented on this wiki, is that [[Paul Gerber]] obtained the same numerical coefficient seventeen years earlier. Gerber's 1898 paper in the ''Zeitschrift für Mathematik und Physik'', expanded in 1902 and republished posthumously in 1917 as a challenge to Einstein, assumed only that gravitational action propagates at a finite speed and derived a retarded potential whose perihelion term matches the observed anomaly when that speed is set equal to ''c''. Gerber treated the numerical coincidence as evidence that gravity and light share a medium. The English translation held here is [[The Propagation of Gravity (English Translation)]], rendered by [[Walter Rella]].

The dispute is over whether the derivation is sound. Gerber's critics &mdash; Seeliger in 1917 and von Laue among them &mdash; argued that his modified potential does not follow from any consistent field theory, that the retardation argument as he framed it does not actually yield his potential, and that his scheme gives the wrong answer for the deflection of starlight. Defenders respond that the perihelion coefficient is not the sort of number one obtains by accident. Priority claims of this kind are collected here in [[Anticipations of Einstein in the General Theory of Relativity]] and, more polemically, in [[Christopher Jon Bjerknes]]'s [[Albert Einstein: The Incorrigible Plagiarist]]. That Gerber got the number first is not in doubt; that his reasoning was valid is.

==On this wiki==

The 43 arcseconds are the benchmark that alternative gravity theories here are expected to reproduce.

* [[Joseph J Smulsky]] models solar rotation as a compound body and computes orbital-element drifts for all planets from Newtonian integration alone in [[Gravitation, Field and Rotation of Mercury Perihelion]].
* [[Thierry De Mees]] attributes the advance to gravitomagnetic effects from the galaxy in [[Mercury's Perihelion Advance is Caused by Our Milky Way]], applying the Maxwell analogy for [[Gravitomagnetism]].
* [[Thomas E Phipps]] argued for a special-relativistic account in [[Mercury's Precession According to Special Relativity]] (''American Journal of Physics'', 1986).
* [[Michael Anteski]] gives an aether reading in [[Ether Theory and the Asymmetrical Apogee in Mercury's Perihelion]]; [[Joe Alexander Nahhas]] claims a classical formula in [[Perihelion precession period 400 years old formula found in hiding ending relativity]].
* [[Ricardo Carezani]]'s [[Autodynamics]] and other frameworks in [[:Category:Gravity]] address the same target.

==See also==

* [[General Relativity]]
* [[Gravity]]
* [[Paul Gerber]]
* [[Gravitomagnetism]]
* [[Albert Einstein]]
* [[Aether]]

[[Category:Gravity]]
[[Category:Relativity]]
[[Category:Astronomy]]