Edmond Halley

Lore & Background

Halley was born in Haggerston in Middlesex. His father, Edmond Halley Sr., was a wealthy soap-maker in London. Halley studied at St Paul's School, where he was elected captain of the school in 1671. In July 1673, he entered The Queen's College, Oxford, taking a twenty-four-foot (7.3 m) long telescope with him. While still an undergraduate, Halley published papers on the Solar System and sunspots. In March 1675, he wrote to John Flamsteed, the first Astronomer Royal, pointing out errors in published tables of Jupiter and Saturn and in some of Tycho Brahe's star positions. In 1676, Flamsteed helped Halley publish his first paper, on planetary orbits, in Philosophical Transactions of the Royal Society. Influenced by Flamsteed's project to catalogue northern stars, Halley proposed to do the same for the southern sky. King Charles II supported the expedition. Halley sailed to Saint Helena in late 1676 and established an observatory with a large sextant with telescopic sights. Over the following year, he made observations for the first telescopic catalogue of the southern sky and observed a transit of Mercury. Focusing on the Mercury transit, Halley recognised that observations of planetary solar parallax, especially during a transit of Venus, could be used to determine trigonometrically the distances between Earth, Venus and the Sun. Halley returned to England in May 1678. Oxford would not allow him to return because he had violated residency requirements, but he appealed to Charles II, who signed a letter requesting that Halley be unconditionally awarded his Master of Arts degree, which the college granted on 3 December 1678. Just a few days before, Halley had been elected as a fellow of the Royal Society, at the age of 22. In 1679, he published Catalogus Stellarum Australium, which includes his map and descriptions of 341 stars. In mid-1679, Halley went to Danzig (Gdańsk) on behalf of the society to help resolve a dispute about astronomer Johannes Hevelius' observations; Halley stayed with Hevelius and found his observations quite precise. In September 1682, Halley carried out a series of observations of what became known as Halley's Comet. In early 1686, Halley was elected to the Royal Society's new position of secretary. Also in 1686, Halley published a paper and chart on trade winds and monsoons from his Helenian expedition, identifying solar heating as the cause of atmospheric motions and establishing the relationship between barometric pressure and height above sea level. In August 1684, Halley went to Cambridge to discuss Kepler's laws with Isaac Newton, finding that Newton had solved the problem without publishing. Halley recognised the importance of Newton's work and returned to Cambridge to arrange its publication, which became Philosophiæ Naturalis Principia Mathematica, published at Halley's expense in 1687. From observations Halley made in September 1682, he used Newton's law of universal gravitation to compute the periodicity of Halley's Comet in his 1705 Synopsis of the Astronomy of Comets. It was named after him upon its predicted return in 1758, which he did not live to see. Beginning in 1698, Halley made sailing expeditions and made observations on the conditions of terrestrial magnetism. In 1718, he discovered the proper motion of the fixed stars.

Reader's Guide

Halley's significance lies in his application of Newtonian physics to celestial mechanics, most famously in predicting the return of the comet that bears his name. His work on the transit of Venus laid the groundwork for measuring the distances between Earth, Venus, and the Sun. As Astronomer Royal, he advanced the study of stellar positions and proper motions. His expeditions and charts of trade winds and monsoons contributed to meteorology and information visualization. Halley also built an early diving bell, demonstrating it in the River Thames at 60 feet (18 m) for over an hour and a half, and proposed a hollow Earth model to explain anomalous compass readings. His legacy endures in the periodic comet and his foundational role in linking observation with mathematical theory.

Did You Know?

• Halley took a twenty-four-foot (7.3 m) long telescope with him when he entered The Queen's College, Oxford in July 1673.
• Halley was elected a fellow of the Royal Society at the age of 22, just a few days before being granted his Master of Arts degree on 3 December 1678.
• Halley built a diving bell and demonstrated it in the River Thames at 60 feet (18 m), remaining there for over an hour and a half.
• Halley published an article on life annuities in 1693 based on Breslau statistics, which strongly influenced the development of actuarial science.
• In 1718, Halley discovered the proper motion of the fixed stars.

The Saint Helena Odyssey

In the late summer of 1676, a twenty-year-old Halley sailed to the South Atlantic island of Saint Helena, carrying a large sextant fitted with telescopic sights. There he erected a small observatory and spent the following year cataloguing stars in the southern celestial hemisphere — a region virtually uncharted by European astronomers. His catalogue, published in 1679 as Catalogus Stellarum Australium, described 341 stars and included a map of the southern sky. During his stay he witnessed a transit of Mercury across the Sun, an event that sparked a crucial insight: observing a planet's parallax during a solar transit could reveal the true distances between Earth, Venus, and the Sun. Upon returning to England in May 1678, Halley found Oxford refusing to readmit him, citing his violation of residency rules. He appealed to King Charles II, who signed a letter demanding the college award his Master of Arts degree unconditionally. It was granted on 3 December 1678, mere days after Halley had been elected a Fellow of the Royal Society at the remarkable age of twenty-two.

The Comet and the Principia

Two of Halley's most consequential contributions to science were inextricably linked. In September 1682, he made a series of observations of a bright comet. By 1681, Giovanni Domenico Cassini had suggested to him that comets followed orbital paths, and Halley applied Newton's law of universal gravitation to compute the comet's periodicity. His 1705 work, the Synopsis of the Astronomy of Comets, predicted its return in 1758 — a prediction that proved correct, though Halley himself did not live to witness it. The comet was named in his honour upon that return. The Newton connection ran deeper still. In August 1684, Halley travelled to Cambridge to press Newton about proving Kepler's laws of planetary motion. Newton, who had already solved the problem but not published it, promised to send his calculations. Halley recognised the extraordinary significance of the work and returned to Cambridge to arrange its publication. Newton, rather than releasing the short treatise, expanded it into the monumental Philosophiæ Naturalis Principia Mathematica, published in 1687 with Halley's encouragement and financial support.

Charting Winds, Magnetism, and Starlight

Beyond the heavens, Halley turned his analytical mind to the atmosphere and the Earth's magnetic field. In 1686 he published a paper and chart on trade winds and monsoons, identifying solar heating as the driving force behind atmospheric motion and establishing the relationship between barometric pressure and altitude above sea level. The symbols he devised to represent trailing winds remain in use on modern weather charts, making his work a foundational piece of information visualisation. Beginning in 1698, he undertook sailing expeditions to study terrestrial magnetism under varying conditions. His most celebrated astronomical discovery came in 1718, when he identified the proper motion of what had long been called 'fixed stars,' demonstrating that even the most distant points of light in the sky were not truly stationary. By 1720 he had succeeded John Flamsteed as the second Astronomer Royal in Britain, a position that capped a career spanning nearly five decades of observation, calculation, and publication.

A Life Forged in Haggerston

Edmond Halley was born on 8 November 1656 in Haggerston, Middlesex, the son of a wealthy Derbyshire-born soap-maker in London. His early aptitude for mathematics was evident at St Paul's School, where he also developed a passion for astronomy and was elected school captain in 1671. The following year his mother, Anne, died. In July 1673 he entered The Queen's College, Oxford, bringing with him a twenty-four-foot telescope that his father had apparently financed. Still an undergraduate, he published papers on the Solar System and sunspots. In March 1675 he wrote to John Flamsteed, the first Astronomer Royal, pointing out errors in the leading published tables for Jupiter and Saturn and in some of Tycho Brahe's star positions. That correspondence set in motion a chain of events — his first publication, the Saint Helena expedition, and his election to the Royal Society at twenty-two. In 1679 he also travelled to Danzig on the Society's behalf to verify the observations of astronomer Johannes Hevelius, whose instruments lacked telescopic sights. Halley stayed with Hevelius, checked his work, and found it to be quite precise.