Edmond Halley English astronomer, geophysicist, mathematician, meteorologist, and physicist

Edmond Halley figures in the early history of the Royal Society, an English astronomer, geophysicist, mathematician, meteorologist, and physicist, known for the comet named after him, whose periodicity he accurately calculated.

In 1676, Halley visited the south Atlantic island of Saint Helena and set up an observatory with a large sextant with telescopic sights to catalog star catalog of the southern hemisphere and visit astronomers in France and Italy. While there he observed a transit of Mercury across the Sun and realized that a similar transit of Venus could be used to determine the absolute size of the Solar System.  In 1679, Halley published the results from his observations on St. Helena as Catalogus Stellarum Australium which included details of 341 southern stars. 

In September 1682 he carried out a series of observations of what became known as Halley’s Comet, though his name became associated with it because of his work on its orbit and predicting its return in 1758. This phase culminates in the publication of Newton’s Principia (1687), In 1698, Halley was given command of the Paramour, a 52 feet (16 m) pink (sailing ship), so that he could carry out investigations in the South Atlantic into the laws governing the variation of the compass. On 19th August 1698, he took command of the ship and, in November 1698, sailed on what was the first purely scientific voyage by an English naval vessel. Unfortunately, problems of insubordination arose over questions of Halley’s competence to command a vessel. Halley returned the ship to England to bring charges against his officers in July 1699. He accomplished this task in a second Atlantic voyage which lasted until 6thSeptember 1700 and extended from 52 degrees north to 52 degrees south. The results were published in General Chart of the Variation of the Compass (1701). 

Subsequently, he is sent to the Adriatic Sea (1703) to survey various potential naval bases for the English Navy. He also conducts a survey of tides in the English Channel (1701), following an earlier survey of the approaches to the Thames (1689) and Professor of Geometry at Oxford University in 1704.

In 1705, applying historical astronomy methods, he published Synopsis Astronomia Cometicae, which stated his belief that the comet sightings of 1456, 1531, 1607, and 1682 Halley used Newton’s laws to determine the gravitational effects of Jupiter and Saturn upon passing comets. This enabled him to show that the comet we now know as Halley’s comet follows an elliptical orbit. This was the first comet determined to be periodic. From records of its appearance in 1531, 1607, and 1682, Halley surmised that it returns every 76 years and predicted its next appearance in 1758.

Halley’s comet was spotted on Christmas day, 1758. Johann Georg Palitzsch, a German farmer and amateur astronomer, became the first person to witness the return of, what would become known as, Halley’s Comet.

Halley’s comet is the only short-period comet (i.e. comet that completes an orbit in under 200 years) that is visible with the naked eye.  It has featured in astronomical reports since at least 240 BC. it wasn’t until 1705 that it was recognized as the same object.  That year, the English astronomer Edmund Halley determined the periodicity of the comet, writing about it in his Synopsis Astronomia Cometicae

Confirmation of the period of Halley’s comet marked the first time any non-planetary object was shown to orbit the Sun. Comets had been an enigma in Galileo’s generation, often regarded as more consistent with the system of Tycho than with Copernicus (see the Controversy over the Comets exhibit in Bizzell Memorial Library).  But after Halley they were regarded as a striking confirmation of the Newtonian “system of the world.”

In 1716, Halley suggested a high-precision measurement of the distance between the Earth and the Sun by timing the transit of Venus. In doing so, he was following the method described by James Gregory in Optica Promota (in which the design of the Gregorian telescope is also described). 

In 1718 he discovered the proper motion of the “fixed” stars by comparing his astrometric measurements with those given in Ptolemy’s Almagest. Arcturus and Sirius were two noted to have moved significantly, the latter having progressed 30 arc minutes (about the diameter of the moon) southwards in 1800 years.

  (1720), Halley takes his place as Astronomer Royal at the Royal Greenwich Observatory. 

Government funded and mandated trips around the Atlantic mark the start of scientific endeavors funded by the government. Prior to these great programmes of observation such as those by Tycho Brahe and Johann Hevelius are essentially the enthusiasms of wealthy amateurs they die with their masters. For problems such as the determination of longitude, there is a need for extended programmes of observation whose results are available to all. These additions to contemporary star maps earned him comparison with Tycho Brahe: e.g. “the southern Tycho” as described by Flamsteed.