Abstract

Urbain Le Verrier became famous by discovering Neptune from its effect on the orbit of Uranus. He turned his attention to Mercury, publishing a preliminary paper in 1841 and a definitive paper in 1859 on the Theory of Mercury. He discovered an unexplained shift in the perihelion of Mercury, which he attributed to the presence of a small unknown planet he called Vulcan, which was never found. The results were corrected in 1895 by Simon Newcomb, who increased the anomalous shift by about 10% but offered no new explanation for it. Albert Einstein, at the end of his 1916 paper on General Relativity, derived a specific solution for the perihelion shift which exactly matched the discrepancy. Dating from the 1947 Clemence review paper, that explanation and precise value have remained to the present time, being completely accepted by theoretical physicists as absolutely true.

The highly technical 1859 Le Verrier paper was written in French, and astronomers and theorists have gone on from the study of the Solar System to the study of the Universe. The partial translation given here throws light on Le Verrier's analysis and thought processes, and points out that the masses he used for Earth and Mercury are quite different from present day values, possibly leading to a different fit to the old data. A 1924 paper by a professor of Celestial Mechanics critiques both the Einstein and the Le Verrier analyses, and a 1993 paper gives a different and better fit to some of Le Verrier's data. Nonetheless, the effect of errors in planet masses seems to give new condition equations that do not change the perihelion discrepancy by a large amount. The question now is whether or not the excess shift of the perihelion of Mercury has been properly explained in terms of General Relativity, or if there are other reasons for the observations, such as effects from a comet, or the asteroid belt, etc.