Short Biography Of Edmund Halley
Edmond Halley is primarily famous nowadays for the periodic comet named after him. However, he had a wide range of scientific interests and held posts varying from sea captain to Astronomer Royal. His contribution to astronomy was considerable, but he was largely overshadowed by his contemporary, Sir Isaac Newton.
Halley was born on 08 November 1656 into a financially secure home at Haggerston, just outside London. He went to school at Saint Pauls, and then went on to Queen's College, Oxford where he developed an interest in astronomy. At the age of 20, half way through his university degree and influenced by John Flamsteed's Star Catalogue of the Northern Skies, he decided to catalogue stars in the southern hemisphere. Halley and a friend set off in November 1676 to sail to St. Helena (an island in the South Atlantic) with free passage granted by the King via the East India Company. During Halley's stay in St Helena, he observed a transit of Mercury on 07 November 1677 and catalogued the positions of some 360 stars. He returned to England in May 1678 and the following year had his observations published as the Catalogus Stellarum Australium, containing detailed positions of 341 stars. The Catalogus received wide acclaim: not only was it the first catalogue of the southern hemisphere stars but also the first mapping of stars compiled using a telescope. It established Halley's scientific reputation, prompted Oxford University to award him an honorary degree, and the Royal Society to elect him a Fellow.
In 1679 Halley suggested that observations of a transit of Mercury or Venus across the Sun's disk could be used to estimate the distance of the Sun and from it the scale of the entire solar system. Halley calculated the dates of the next two transits of Venus, in 1761 and 1769. Although he died before the first of these dates, astronomers across much of the world observed the two transits.
In 1684 Halley had an extensive dialogue with Sir Isaac Newton on the laws of planetary motion. In 1685, he was elected Clerk to the Royal Society and started editing its journal, Philosophical Transactions. He asked the Royal Society to finance publication of Newton's work on gravity, the Principia, but it refused, as it had just financed the publication of a book which was not selling very well, by Francis Willoughby, entitled The History of Fishes. (In fact the Royal Society owed Halley fifty pounds salary but could not afford to pay him so instead sent him fifty copies of The History of Fishes. Halley was renowned for having a strong sense of humour but whether he saw the joke in this matter is uncertain!) As Halley could not get persuade the Royal Society to finance publication of the Principia, he did so himself. The work was published in 1687, and became the most famous scientific book of all time.
During his term as Clerk, Halley investigated many diverse subjects including differences between the orbits of Jupiter and Saturn and the slow secular acceleration of the mean motion of the Moon. In 1686, he published an account for mariners of the trade winds and monsoons. He also investigated the salinity of the oceans and was able to estimate fairly accurately the age of the Earth by measuring the rate at which salinity increased.
At this time, there was considerable interest in finding a quick and reliable way of determining longitude at sea. Halley proposed a method based on variations in the Earth's magnetic field. He contacted the Admiralty, which took a great interest in the proposal and commissioned him to the rank of captain, giving him a small ship, the Paramour, for his research. Halley's first voyage in the Paramour began in November 1698 at Portsmouth, but was cut short by a mutiny. His second trip, completed in mid-1700, was more rewarding, and covered the Atlantic as far south as the Falkland Islands. He also discovered that the Aurora Borealis was related to the Earth's magnetic field.
He also did much work in the field of geometry and in 1704 became Savilian Professor of Geometry at Oxford.
Halley was one of the first astronomers to apply Newton's laws of motion to comets. In 1705 he published Synopsis Astronomia Cometicae which listed observations of 24 bright comets that had appeared between 1397 and 1698. It also articulated his theory that the comets of 1456, 1531, 1607 and 1682 were the same, and that the comet in question would appear again in 1758. As Halley knew that he would not be alive to see the return of the comet, he wrote in his diary: If the Comet should return according to my prediction, about the year 1758, impartial posterity will not refuse to acknowledge that this was discovered by an Englishman. The comet was first seen again on Christmas Day 1758 and it was given the name Halley's Comet in recognition of his outstanding work in astronomy. It indeed returns every 76 years.
During 1718, Halley observed Sirius, Aldebaran and Arcturus and compared their positions in the sky with Ptolomey's Star Atlas;
noticing that the positions did not agree, he thus discovered the phenomenon of stellar proper motion.
The highlight of Halley's career was his appointment to the post of Astronomer Royal in 1719, at the age of 64, succeeding Flamsteed. Halley occupied the post for 20 years. From as early as 1684, he had observed regular deviations of the Moon from its predicted motion and, as Astronomer Royal he continued this work. He observed the Moon through one entire saros cycle of eighteen years. Although he died before he could analyse fully his observations, they proved to be of great value to later astronomers in calculating the complex nature of the lunar orbit. The results of his observations were published in 1749 and included tables of the Moon and planets which he had prepared as far back as 1719.
Halley died at the age of 86 in January 1742.