Fig2_6 Mercury precession

Fig2_6 Mercury precession

Fig. 2.6 . Instead of always tracing out the same ellipse, the orbit of Mercury pivots around the focus occupied by the Sun. The point of closest approach to the Sun, the perihelion, is slowly rotating ahead of the point predicted by Newton's theory of gravitation. This was at first explained by the gravitational tug of an unknown planet called Vulcan that was supposed to revolve about the Sun inside Mercury’s orbit, but we now know that Vulcan does not exist. The German physicist Albert Einstein (1879-1955) explained Mercury's anomalous motion in 1915 by inventing a new theory of gravity in which the Sun's curvature of nearby space makes the planet move in a slowly revolving ellipse.

Copyright 2010, Professor Kenneth R. Lang, Tufts University