Comets in Motion

Abstract

We all know the story of Newton and Halley. Thanks to his discovery of the phenomenon of gravity and the formulation of its effects in the form of mathematical laws, Newton was able to demonstrate that comets obeyed the same universal law as every other physical object in the universe. Much of this work was based upon the motion through the sky of a very spectacular comet that appeared during the latter part of 1680 (Fig. 2.1). In the process, he was able to show that the bright comet that had graced the morning skies during November and early December of 1680 was actually the same as the even more magnificent apparition that emerged from the evening twilight just prior to Christmas. He also correctly demonstrated that this comet had passed unusually close to the Sun around mid-month.