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Edmund Halley 1656-1742 His life Halley was born in a soap-maker family in Haggerston, England, in 1656 (four years before the Restoration of Charles II). Since he was a child he showed his interest in Maths. Education Halley attended St. Paul’s School in London, then he went to Queen’s College (Oxford), and in that period he was introduced into the Royal Greenwich Observatory. After some travels around the world with the East India Company, in 1678 he was elected a fellow of the Royal Society and, with the intercession of the King, was granted the M.A. degree from Oxford University. First works In 1684 he helped Newton in the development of the theory of gravitation; he therefore tried to solve the problem of the planetary motion with Robert Hook and Sir Christopher Wren. Mathematics Edmond greatly improved the theory of equations in algebra, the doctrine of logarithms and the property of sections of a cone. While a professor at Oxford Edmond published important editions of the work of Apollonius of Pega and of other ancient geometricians. Mathematics helped him also in his astronomical studies. Travelling abroad After some sea voyages undertaken for purely scientific purposes (first in History!!), it was Halley who published the first meteorological chart in 1686 using an isometrically representation. He also introduced a rudimentary working model of a magnetic compass. After his voyages… When he returned he published some studies about winds and monsoons, and he also identified the cause of atmospheric motions: the solar heating Some strange studies! In 1691, Halley built a diving bell, a device in which the atmosphere was replenished by way of weighted barrels of air sent down from the surface. And with it he and 5 companions dived to 60feet in the Thames for one and a half hour. Statistics Edmund Halley, in 1693, was the first to employ correct mathematical methods to calculate a life table (invented by John Graunt), but he first became interested in the vital statistics in Paris around 1680. He used vital statistics collected by Caspar Neumann of Breslau (“Reflexionen über Leben und Tod bey denen in Breslau Geborenen und Gestorbenen”). How can we calculate a life table??? A life table is easy to calculate if the mortality rates are known for each year of age. Starting with an arbitrary large number, say 1,000, of newborn, the number surviving to age one year can be estimated from the mortality rate in the first year of life. Then the number surviving to the age two years can be estimated using the mortality rate in the second year of life, and so on. Halley’s work in statistics was the first step towards the theory of annuities, life insurance and the actuarial profession, in fact he was the first to mathematically and statistically rigorously calculate premiums for a life insurance policy. But what’s an actuary??? Actuaries mathematically evaluate the likelihood of events and quantify the contingent outcomes in order to minimize losses, both emotional and financial, associated with uncertain undesirable events. Voyages and magnetism Between 1698-1700 Halley was commissioned as a naval captain and he actually commanded a Royal Navy manof-war, the Paramour, making two prolonged and eventful ocean voyages. After that he pubblished the first magnetic charts of the Atlantic and Pacific Ocean The Halley’s Astronomy Continuing his pioneering work in observational astronomy, Halley published in 1705 A Synopsis of the Astronomy of Comets, in which he described the parabolic orbits of 24 comets that had been observed from 1337 to 1698. He showed that the three historic comets of 1531, 1607, and 1682 were so similar in characteristics that they must have been successive returns of the same visitant—now known as Halley’s Comet— and accurately predicted its return in 1758. The Halley’s Comet! Other studies of Astronomy Halley predicted with considerable accuracy the path of totality of the solar eclipse visible over England in 1715. After a long and careful study he was the first to realise in 1693 that the Moon's mean motion had a secular acceleration. An apparent gradual acceleration of the Moon's motion in its orbit, as measured relative to mean solar time. He was the first to predict extraterrestrial nature of the precursors of meteors. He was the first to suggest that observations of transits of Venus could be used to measure the distance of the Sun. Against Greek’s astronomy In 1718 he discovered the Proper motion of the "fixed" stars by comparing his astrometric measurements with those given in Ptolemy's Almagest, so he offered the first proof of motions of starsby showing that they had moved since Ptolemy’s time Relation between proper motion and velocity components of an object. At emission, the object was at distance d from the Sun, and moved at angular rate μ radians/s, that is, μ = vt / d with vt = velocity transverse to line of sight from the Sun. (The diagram illustrates an angle μ swept out in unit time at tangential velocity vt.) The last years Halley succeeded John Flamsteed in 1720 as Astronomer Royal, a position Halley held until his death in 1742 at the age of 85. Halley was buried in the graveyard of the old church of St. Margaret (now ruined). THE END