Edmond Halley

Edmond Halley (1656-1742), British astronomer, who first calculated the orbit of a comet. He was born in London and educated at the University of Oxford. Halley was intrigued by the theories of the British physicist Sir Isaac Newton and encouraged him to write his famous Philosophiae Naturalis Principia Mathematica (Mathematical Principles of Natural Philosophy, known as the Principia), which Halley then published in 1687 at his own expense. Halley was made Astronomer Royal in 1721 and began an 18-year study of the complete revolution of the Moon through its ascending and descending nodes.

Halley’s most important scientific treatise was Astronomiae Cometicae Synopsis (Synopsis on Cometary Astronomy), begun in 1682 and published in 1705. In this work, Halley applied Newton’s laws of motion (see Mechanics) to all available data on comets and then mathematically demonstrated that comets move in elliptic orbits around the Sun. His accurate prediction of the return in 1758 of a comet (now known as Halley’s Comet) validated his theory that comets are part of the solar system.