Anomalies in scientific data can sometimes lead to a richer understanding of the underlying principles involved. Einstein was able to explain the difference between the Newtonian description of Mercury's orbit and subsequent observations by applying his developing theory of General Relativity. Add the curvature of spacetime to the Newtonian picture and the problem of a tiny discrepancy in Mercury's perihelion precession can be resolved. This anomaly briefly changed our view of the Solar System. Originally, the astronomer Urbain Le Verrier had thought it could be explained by the presence of another planet -- Vulcan -- closer than Mercury to the Sun, but reported sightings of Vulcan were found to be spurious. Einstein's work solved the precession problem. In a letter to his close friend Michele Angelo Besso, Einstein would write: "In these last months I had great success in my work. Generally covariant gravitation equations. Perihelion motions explained quantitatively… you will...