Halley , Edmond

(1656–1742) British astronomer and physicist

Edmond (or Edmund) Halley was the son of a wealthy London merchant. He was educated at St. Paul's School, London, and at Oxford University. He left Oxford without a degree in 1676, but having already published his first scientific paper in thePhilosophical Transactions of the Royal Society on the theory of planetary orbits. Halley's scientific work and his life covered an enormous range. He started his active scientific career by spending two years on St. Helena mapping the southern skies. In 1679 he published Catalogus stellarum australium (Catalog of the Southern Stars) the first catalog of telescopically determined star positions. On his return he traveled extensively in Europe meeting such leading astronomers as Johannes Hevelius and Giovanni Cassini.

Halley now began his enormous contribution to just about all branches of physics and astronomy. He prepared extensive maps showing magnetic variation, winds, and tides. In atmospheric physics he formulated the mathematical law relating height and pressure (1686), making many advances in barometric design. He carried out important studies on evaporation and the salinity of lakes (1687–1694), which allowed him to draw conclusions about the age of the Earth. He used Newtonian mathematical techniques to improve and augment Descartes's work on the optics of the rainbow (1697–1721). He almost incidentally constructed mortality tables, estimated the acreage of England and the size of the atom, improved the design of the diving bell, and published numerous articles on natural history and classical studies.

These were sidelines compared to his work in astronomy and to the help he provided Newton. It is owing to Halley that Newton'sPrincipia was published in the complete form we know it today. He pressed Newton to publish it, paid for the cost himself, saw it through the press, and even contributed some Latin verses in honor of the author. In 1695 he proposed the secular acceleration of the Moon, in 1718 he discovered the proper motion of the stars, but above all in his Astronomiae cometicae synopsis(1705; A Synopsis of the Astronomy of Comets) he laid the foundations of modern cometary study. His grasp of the geometry of cometary orbits allowed him to identify the comet (now known as Halley's comet) of 1531 with those of 1607 and 1682, and confidently to predict its return in 1758 – long after his death.

He held an equally varied and bewildering set of appointments. From 1696 until 1698 he was deputy controller of the mint at Chester. From 1698 to 1700 he actually commanded a Royal Navy man-of-war, the Paramour, making prolonged and eventful ocean voyages. In 1702 and in 1703 he made two diplomatic missions to Vienna. In 1703 he was elected to the Savillian Chair of Geometry at Oxford, and in 1720 he succeeded John Flamsteed as Astronomer Royal. He held this post until his death, making observations of nearly 1500 lunar meriodional transits and the full 18-year period of the Moon.