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Halley, Edmond

comets age astronomer map

[ha lee, haw lee] (1656–1742) English astronomer and physicist: made numerous contributions to astronomy and geophysics.

Son of a wealthy businessman, Halley was an experienced observer as a schoolboy before he entered Oxford in 1673. He became a remarkable and prolific scientist, who made important discoveries in many fields. He was also highly likable and even good-looking. He made his name as an astronomer by travelling at the age of 20 to St Helena, where he remained for 2 years to produce the first accurate catalogue of stars in the southern sky (also the first telescopically determined star survey), which was published in 1679. His interest in comets was kindled by the great comet of 1682, which prompted him to compute the orbits of 24 known comets; noting that the orbits of comets seen in 1456, 1531, 1607 and 1682 were very similar, he deduced that they were the same body and predicted its return in 1758. (It is now known by his name.) It was the first correct prediction of its kind and demonstrated conclusively that comets were celestial bodies and not a meteorological phenomenon, as had sometimes been believed. Halley’s map of his predicted path of the solar eclipse of 1715. His object in part was to curb superstitious fears: his predictions proved to be accurate.

He was a keen explorer and commanded small naval ships (not very competently) in expeditions, including one in the Southern Ocean in which he failed to discover Antarctica and nearly lost his ship.

His other astronomical discoveries were numerous: in 1695 he proposed the secular acceleration of the Moon; in 1718 he observed the proper motion of the stars after observing Sirius, Procyon and Arcturus; he was the first to suggest that nebulae were clouds of interstellar gas in which formation processes were occurring. He succeeded as Astronomer Royal in 1720 at the age of 63 and commenced a programme of observation of the 19-year lunar cycle, a task that he completed successfully and which confirmed the secular acceleration of the Moon. Halley’s celebrated friendship with enabled him to persuade Newton to publish his Principia through the Royal Society, of which Halley was clerk and editor. When the Society was unable to finance the book Halley paid for its printing himself.

If his interests within astronomy were broad, so were his achievements in other branches of science. In 1686 he published the first map of the winds on the Earth’s surface and formulated a relationship between height and air pressure; between 1687 and 1694 he studied the evaporation and salinity of lakes and drew conclusions about the age of the Earth; between 1698 and 1702 he conducted surveys of terrestrial magnetism and of the tides and coasts of the English Channel; in 1715 he correctly proposed that the salt in the sea came from river-borne land deposits. He realized that the aurora borealis was magnetic in origin, constructed the first mortality tables, improved understanding of the optics of rainbows and estimated the size of the atom. He devised, and personally used, the first diving bell. If Halley was fortunate in his talents, wealth and personality, he certainly made good use of his assets.

Halpin, James - Overview, Personal Life, Career Details, Chronology: James Halpin, Social and Economic Impact [next] [back] Hall, Sharlot (1870–1942) - Local History

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