Edmund Halley FRS, Astronomer Royal Edmund (also spelled Edmond) Halley was born on 8 November 1656 in Haggerston, Shoreditch, near London. He was educated at St. Paul’s School in London and entered at Queen’s College, Oxford in 1673. While at Oxford, he was introduced to John Flamsteed, who, in 1676, had been appointed the first Astronomer Royal by King Charles II. Halley began working with Flamsteed, assisting him with observations at the Royal Observatory and at Oxford. During this time, he studied Flamsteed’s use of the telescope to create an accurate catalogue of northern stars. This so inspired Halley that he proposed to create a similar catalogue for stars in the southern hemisphere. After acquiring patronage from King Charles II (who also provided a letter to the East India Company compelling them to provide passage for Halley), he sailed from Oxford to the island of St Helena in November of 1676. In this southernmost territory under British rule, he constructed an observatory. Despite uncooperative weather, he was able to record the celestial longitudes and latitudes of 341 stars, observe the transit of Mercury across the sun, and notate that certain stars had become fainter since the time of previous observations in antiquity (the period in which ancient Greece and ancient Rome flourished). Halley published his southern star catalogue in 1678. This established his reputation as an astronomer and was the first published work containing telescopically determined locations of southern stars. In that same year, Halley was elected a fellow of the Royal Society. He became part of a group of scientists who met regularly to discuss their work. This group formed the core of what would become the Royal Society and included Christopher Wren, Sir Isaac Newton and Robert Hooke.[1] Halley is also well known for his role in the publication of Sir Isaac Newton’s Philosophiae Naturalis Principia Mathematica. Halley first visited Newton in Cambridge in 1684. At that time, Newton, Halley, and his fellow Royal Society members Robert Hooke and Sir Christopher Wren were all individually attempting to find an explanation for planetary motion around the sun. Their competition with one another promoted lively discussion and certainly contributed to Newton’s development of the theory of gravitation. Newton claimed that he had solved the problem of planetary motion by identifying the orbit as an ellipse. Unfortunately, however, he had mislaid the calculations he had made to prove his theory. Halley actively encouraged Newton to expand his studies on celestial mechanics, which would be published as his Principia (mentioned above), and the Royal Society even decided that ‘Mr. Halley undertake the business of looking after it and printing it at his own charge’. As caretaker of the Principia project, Halley consulted Newton throughout, edited the text, wrote a verse in Latin for the preface, and, in 1687, delivered the manuscript to the printers. In 1686, Halley produced his map of the world, showing prevailing winds over oceans; this was the first meteorological chart to be published. He is also credited with one of the first attempts to analyse demographic data, which he presented in ‘life tables’ and used to investigate relations between mortality and age (specifically for the population of Breslau Germany). In 1693, these findings were published in the Royal Society’s journal, Philosophical Transactions. This work influenced the development of actuarial tables for life insurance premiums. From 1698 to 1700, on what was the first sea voyage undertaken exclusively for scientific purposes, Halley commanded HMS Paramore Pink. This small ship, known as a pink, sailed the South Atlantic in an endeavor to determine accurate latitudes and longitudes for ports. Halley’s studies on this journey led to publication of the first magnetic charts of the Atlantic Ocean (and some of the Pacific) in 1701. Unfortunately, it soon became clear that compass declination varied from year to year, and his method of determining longitude was insufficiently reliable. Despite opposition from Flamsteed, Halley was appointed Savilian Professor of Geometry at Oxford in 1704, and in 1705 he published A Synopsis of the Astronomy of Comets. This work describes the parabolic orbits of 24 comets as observed from 1337 to 1698, and shows the successive returns of the same comet in 1531, 1607 and 1682. He then accurately predicted the comet’s return in 1758. This comet is now famously known as Halley’s Comet. Flamsteed had still yet to publish his meticulously produced maps of the heavens. Halley exacerbated his somewhat fraught relationship with the Astronomer Royal when he and Newton got a hold of most of Flamsteed’s data from the Royal Observatory and in 1712 published their own pirated edition of his star catalogue in 1712.[2] Enraged, Flamsteed duly burned 300 of the 400 copies printed.[3] In 1716, Halley predicted the transit of Venus across the sun. This, in turn, helped him to accurately determine the distance from the earth to the sun (see below). In 1718 he also accurately predicted the ‘proper motion’ of two stars, Sirius and Arcturus, whose positions relative to those of their neighbours had shifted over time. In 1720, Halley succeeded Flamsteed as the second Astronomer Royal, taking up the post at Greenwich, where he observed the transits of the moon across the meridian and continued to work on the problem of determining longitude at sea. Around 1730 the ambitious Yorkshire clockmaker John Harrison travelled to London and presented his ideas for a ‘sea clock’ to Halley, the then Astronomer Royal. In her book Longitude, Dava Sobel explains that despite favouring an astronomical approach to the problem of determining longitude at sea (as did other members of the Board of Longitude), Halley ‘kept and open mind’ and Rather than march Harrison into the lion’s den, Halley sent him to see the well-known watchmaker George Graham. “Honest” George Graham, as he was later called, would be the best judge of the sea clock Harrison proposed to build. This was a fortuitous meeting. Graham, a highly respected watch- and clockmaker, became Harrison’s patron after spending just one day with him.[4] Harrison would go on to solve the problem of determining at sea with his sea clock, H4, in 1764, some 34 years later. Halley also predicted that transits of Venus would occur in 1761 and 1769. He urged those who would be observing the event to record the fullest details from different locations around the globe, because the data generated would enable astronomers to calculate the true distance between the earth and the sun. To do this, a first-class regulator clock, a telescope fitted with a micrometre, and a tent to protect these instruments from inclement weather were needed. In 1738, clockmaker John Ellicott was elected Fellow of the Royal Society, and in 1760 he produced regulator clocks which were used by astronomers to track the transit of Venus in 1761. Edmund Halley died 14 January 1742, in Greenwich. End Notes [1] Sobel 2011, 31–32. [2] Prince George of Denmark famously funded the pirated publication of Flamsteed’s unfinished star catalogue. [3] Sobel 2007, 59-60. [4] Sobel 2011, 76–77. Reference Sobel, D. 2011. Longitude: The true story of a lone genius who solved the greatest scientific problem of his time. London: Harper Perrennial. Image Credit John Faber the Younger, ca. 1695–1756, Netherlandish, active in Britain, Edmund Halley, 1722, Mezzotint on moderately thick, slightly textured, cream, laid paper, Yale Center for British Art, Paul Mellon Collection, B1977.14.9978
