Edmond Halley (1656-1742)
Credit: Public domain.
Edmond (or Edmund) Halley was an English scientist who is best known for predicting the orbit of the comet that was later named after him. Though he is remembered foremost as an astronomer, he also made significant discoveries in the fields of geophysics, mathematics, meteorology and physics.
Halley — the traditional pronunciation of the name usually rhymes with valley — was born Nov. 8, 1656, in Haggerston, Shoreditch, London, England. His father was a prosperous soapmaker and property owner. Halley was tutored privately at home before entering St. Paul's School, where he excelled in mathematics and astronomy.
Halley entered Queen's College, Oxford, in 1673, when he was 17 years old. He brought with him a fine collection of astronomical instruments purchased by his father. While still an undergrad, he became a protégée of John Flamsteed, the Astronomer Royal. Halley made important observations at Oxford, including an occultation of Mars by the moon, and published papers on the solar system and on sunspots.
Halley gave up his studies in 1676 and sailed to St. Helena in the South Atlantic. While there he catalogued 341 stars in the Southern Hemisphere and discovered a star cluster in Centaurus. He also made the first observation of a transit of Mercury and realized that a similar transit of Venus could be used to measure the size of the solar system. During the voyage, he also improved the sextant, and made observations about the ocean and the atmosphere.
Halley published his star catalog in 1678; it established his reputation as an astronomer. King Charles II decreed that Oxford grant Halley a Master of Arts degree. Halley was also elected a fellow of the Royal Society. At the age of 22, he was among the youngest members.
For the next few years, Halley traveled and made observations. He observed a comet in Paris in 1680 and worked with Giovanni Cassini to determine its orbit. In 1684, Halley, with fellow Royal Society members Christopher Wren and Robert Hooke, visited Isaac Newton to discuss theories of planetary motion. Newton showed them his calculations. Halley persuaded Newton to expand his studies and allow him to edit the work. Halley paid all the expenses, corrected the proofs himself, and brought "Philosophiae Naturalis Principia Mathematica" ("Mathematical Principles of Natural Philosophy," often referred to as the "Principia") to print in 1687.
Halley continued to work for the Royal Society in a number of endeavors. He edited "Philosophical Transactions," published some of the world's first actuarial tables, and published a map of the world that showed the prevailing winds over the oceans — the first meteorological chart. In 1698, he commanded a British naval ship on a scientific expedition. On two voyages, Halley took compass measurements in the South Atlantic and determined accurate longitudes and latitudes of his ports of call. He also studied the variation between Magnetic North and True North. After the second voyage, he published a map showing isoclines, or points of equal value of deviation.
In 1704, Halley was appointed the Savilian Professor of Geometry at Oxford. Continuing his work in observational astronomy, Halley published "A Synopsis of the Astronomy of Comets" in 1705. In this work, he showed that comet sightings of 1456, 1531, 1607 and 1682 were so similar that they must have been the same comet returning. He predicted that it would return in 1758. [Photos: Halley's Comet Through History]
In 1716, Halley devised a method for observing transits of Venus across the disk of the sun in order to determine the distance of Earth from the sun. He also proposed two types of diving bells for exploring underwater. In 1718, by comparing star positions with data recorded by the Greek philosopher Ptolemy, he deduced the motion of stars.
In 1720, Halley succeeded Flamsteed as Astronomer Royal. He continued to make observations, such as timing the transits of the moon across the meridian, which he hoped would eventually be useful in determining longitude at sea.
Halley died Jan. 14, 1742, in Greenwich, England. He did not survive to see the return of what later was named Halley's Comet, on Christmas Day in 1758.
"Nearer the gods no mortal may approach."
— Preface, "Philosophiae Naturalis Principia Mathematica," referring to Isaac Newton
"In the year 1456 … a Comet was seen passing Retrograde between the Earth and the sun… Hence I dare venture to foretell, that it will return again in the year 1758."
— "A Synopsis of the Astronomy of Comets" (1705)
"This sight ... is by far the noblest astronomy affords.”
— “De Visibili Conjunctione Inferiorum Planetarum cum Sole, Dissertatio Astronomica.” Philosophical Transactions of the Royal Society 17 (1691): 519
“I earnestly wish them all imaginable success; in the first place that they may not, by the unseasonable obscurity of a cloudy sky, be deprived of this most desirable sight; and then, that having ascertained with more exactness the magnitudes of the planetary orbits, it may redound to their eternal fame and glory.”
— "A New Method of Determining the Parallax of the Sun." Philosophical Transactions, Vol. XXIX (1716)