In 1859, the brilliant scientist Urbain LeVerrier discovered that the planet Mercury has a wobble, that its orbit shifts over time. His explanation was that there had to be an unseen planet circling even closer to the sun. He called the planet Vulcan. Supported by the theories of Sir Isaac Newton, the finest astronomers of their generation began to seek out Vulcan and at least a dozen reports of discovery were filed. There was only one problem. Vulcan does not exist - and was never there. The real explanation was only revealed when a young Albert Einstein came up with a theory of gravity that also happened to prove that Mercury's orbit could indeed be explained - not by Newton's theories but by Einstein's own theory of general relativity. THE HUNT FOR VULCAN is a scientific detective tale at the intersection of theory, measurement, and belief; and a reflection on a bizarre period in which the power of conformity led very smart people to literally see a planet that wasn't there.