English astronomer, geophysicist, mathematician, meteorologist, and physicist, Sir Edmund Halley is best known for his discoveries surrounding Halley's Comet. How much do you know about this scientific giant?
Skywatchers in ages past trembled at the approach of a comet. Where superstition was widespread, any unusual object in the night sky could send a wave of terror through the population. Thought to be harbingers of disaster, comets were typically associated with the death of a king or a defeat in battle.
Superstition and fear had no grip on the character of Edmund Halley, who successfully plotted the orbit of the comet that bears his name. He was stimulated instead by scientific curiosity and a deep desire to extend the bounds of knowledge.
At the age of 20, Halley wrote: "I would very willingly do something to serve me generation."
For the next 66 years, he delighted in exploring the fields of astronomy and physics, navigation, natural science, and mathematics.
Born in Haggerston, near London, Halley was the son of a prosperous soap-boiler. The boy was fortunate to have a father who was able to give him a good education at St. Paul's School and Oxford University. The senior Halley also had sufficient interest and faith in his gifted son to provide the scientific apparatus the lad wanted as well as a generous allowance when he suddenly decided to leave Oxford before taking his degree.
Young Halley's eagerness to set off on a voyage to the distant South Atlantic island of St. Helena to chart the stars of the southern hemisphere would have seemed a foolish scheme to most fathers. But Edmund's patient parent apparently understood that his son's love of learning might not always allow him to follow conventional channels.
On hearing of Edmund Halley's desire to chart the southern stars, King Charles II ordered the East India Company to convey the 20-year-old astronomer, his companion, and their equipment on the next ship bound for St. Helena. It required a three-month voyage to span the distance that a jet flight can accomplish in a few hours today. After long days at sea, the youthful astronomers set up a temporary observatory on a mountain and were ready to begin charting the stars. The weather proved to be a frustrating obstacle. It rained, it was cloudy, and fog hovered around the volcanic isle.
Finally, after a full year, the young men were able to return to England with a chart of 341 stars that are not visible in the northern hemisphere. Letters from the King to Oxford University, giving a good account of Halley's learning in mathematics and astronomy, resulted in him being granted the degree of Master of Arts. At the age of 22 he was elected a Fellow of the Royal Society. Edmund Halley was on his way to being a friend of kings, an associate of the great scientists of the day.
Foreign travel often seemed to be on Halley's agenda. One year after the expedition to St. Helena, he was off to Danzig (now Gdansk, in Poland) where the renowned astronomer Hevelius had constructed some of the finest telescopes ever seen. Later, in 1680, he embarked on a Grand Tour of France and Italy. Along the way, he observed the Great Comet of 1680 and visited the Paris Observatory.
In Paris, Halley became interested in the vital statistics of the city. He drew up tables of age and mortality in a normal population. This pioneering work in statistics laid the foundation for the theory of annuities and life insurance. From his study of tables of births and deaths, Halley concluded:
"The Growth and Increase of Mankind is not so much stinted by anything in the Nature of the Species, as it is from the cautious difficulty most People make to adventure on the State of Marriage, from the Prospect of the Trouble and Charge of providing for a Family. He further observed that Celibacy ought to be discouraged, and those who have numerous Families of Children to be countenanced and encouraged..."
Soon after his return to England Halley himself decided to adventure into the State of Marriage. He and Mary Tooke were married in 1682, the same year that Halley spotted the comet that would eventually bear his name. The comet sped off into space but Mary remained close to her ingenious husband for the remaining 55 years of her life. The couple set up housekeeping at Islington and in time three children completed the family. Halley equipped a small private observatory and, among other projects, began working on the problem of longitude, a subject that would tantalize him as long as he lived.
After his generous father died in 1684, Halley began to feel the need for an increase in income. He accepted a salaried position as Clerk to the Royal Society and for a short time, he was Deputy Comptroller of the Chester Mint. He was commissioned to survey and chart the tidal currents of the English Channel. In 1702 and 1703 he took part in two diplomatic missions to Vienna and the Dalmatian coast where ports were being fortified to protect British men-of-war in the Adriatic. Halley so impressed the Holy Roman Emperor Leopold I that he gave the astronomer a diamond ring from his own finger and a letter of high commendation to take back to Queen Anne.
Royalty also touched Halley's life when Russia's Tsar Peter the Great visited England and made a point of calling on the eminent scientist. The Tsar asked Halley questions on many subjects and was well satisfied with the answers he received. He looked upon the genial astronomer as a friend and the story still persists of the high-spirited Tsar trundling Halley through a hedge in a wheelbarrow.
In 1698 Halley began an Atlantic voyage as the naval officer commanding a man-of-war. This was a rather special ship, built expressly for the special expedition, victualled for 12 months, and carrying a crew of 20 men. Captain Halley proved himself a competent seaman, noting the longitude and latitude of all ports visited and the variation in the compass in the South Atlantic. He did, however, find some of his crew uneasy and refractory. Returning to England, he dismissed his lieutenant, acquired several more seamen, and again set sail for the South Atlantic. There were icebergs in the lonely southern waters, fog and cold temperatures to be endured.
About 700 miles east of Brazil, Halley reached the tiny uninhabited volcanic island of Trinidad. Taking possession of the island in the name of the English Sovereign, he left a few goats, hogs, Guiney Hens I carried them from St Helena, and The Union Flag flying. Several times the scientist and crew were mistaken for pirates. On the Grand Banks of Newfoundland, a fishing vessel from Maine fired four or five shots through the rigging.
His sea-faring experiences must have left their mark. Astronomer John Flamsteed, writing to mathematician Abraham Sharp in 1703, noted that Mr. Halley...now talks, swears, and drinks brandy like a sea captain. Early in the next year, Halley exchanged his captain's uniform for the gown of a professor of geometry at Oxford. Continuing to be active in the Royal Society, any vestiges of the sea captain did not prevent him from presenting papers on a great variety of subjects.
In 1716 two weeks after a young English nobleman, the Earl of Derwentwater was beheaded for high treason, a brilliant display of northern lights was seen over England. The two events were popularly linked and the marvelous flares of colour, usually seen only in high northern latitudes, were called Lord Derwentwater's Lights. We may not know Edmund Halley's impression of the unlucky Jacobite lord but we do know that he searched for a scientific explanation for the display of northern lights. He speculated that the cause might be water vapour or magnetism, but he definitely didn't subscribe to the notion of Lord Derwentwater's supernatural influence.
When the eclipse of the sun occurred over southern England in 1715, Halley predicted the track of the shadow where there would be sudden darkness wherein Starrs will be visible. In the summer of 1716, Venus remained visible in daylight and the learned Professor Halley explained the phenomenon publically to prevent the Superstition of the unskillful Vulgar.
If a friend passed along a problem to Halley he could be confident that the scientist would use every means to arrive at a solution. Take, for example, the question posed by John Houghton, also a Fellow of the Royal Society: how can one arrive at a reasonable estimate of the total acreage of England and Wales considering the irregular shape of the land surface?
Halley attacked the problem in an unconventional way. He found the most accurate map available, cut carefully around each bay and inlet until he held a paper outline of the land area of England and Wales. He weighed this map, the cut out a circle for the central part of England. Finding the acreage of a known circle would not be a difficult task. He weighed the paper circle and compared it with the weight of the full map. His estimate of the total acreage of England and Wales was amazingly close to today's figure.
On 26th May 1697, Halley carefully studied the mercury in his barometer on the summit of Snowdon, the highest mountain in southern Britain. Later the same day he took a reading at the foot of the mountain. On the following day, he observed the pressure at sea level. Using a formula based on the variation in readings he determined the height of the mountain.
Rainbows and evaporation, meteors, and classical studies all captured Halley's attention. As early as 1688 he showed an interest in the problem of supplying air to divers. He wrote a paper on The Art of Living Under Water and described his own experiences:
"I myself have been One or Five who have [stayed] together at the Bottom, in Nine or Ten Fathoms Water, for above an hour and a half at a time, without any sort of ill consequence. A practical man, he proposed to raise sunken ships by using air-filled barrels. He formed a company for salvaging wrecks and in 1691 was engaged in actual underwater operations."
Halley had many friends; among them was the great mathematician Isaac Newton. The Principia, Newton's brilliant work on gravity and mechanics, might never have been published except for the unselfish devotion of Edmund Halley. Not only did he help Newton collect astronomical data, but he undertook to supervise and pay for the printing.
Though encouraging Newton to publish his monumental work may be Halley's most lasting contribution, many people know him simply as the comet man. After collecting and analyzing cometary observations from the past, Halley was able to predict that the 1682 comet would reappear in 1758. He knew that he would not be alive to see the apparition and he did not hope for personal fame if his prediction proved correct. He did hope that posterity will not refuse to acknowledge that this was first discovered by an Englishman. Indeed the comet was sighted - on Christmas Day 1758. At approximately 76-year intervals, in 1835 and 1910, it made return visits.
After England's first Astronomer Royal, John Flamsteed, died in 1719, Edmund Halley was appointed to the position. He found the Royal Observatory on Greenwich Hill quite bare of all instruments and moveable items as these had all belonged to Flamsteed and had been removed by his executor. With a grant of £500 Halley purchased equipment and for the next 22 years, until his death at the age of 85, the energetic astronomer recorded his observations.
Until a year before his death, Halley made a weekly trip to London by river for a gathering of friends Child's Coffee-House before going on to a meeting of the Royal Society. The years were beginning to take their toll. One contemporary remembered that Dr. Halley never ate anything but fish, for he had no teeth. He suffered partial paralysis of his right hand. When death finally came, the old Astronomer Royal was seated in his chair at the Greenwich Observatory.
* Originally published in June 2006.