Edmond Halley

Edmond (or Edmund ) Halley (October 29th 1656, Haggerston, Borough of Hackney with London - January 14th 1742, Greenwich) is a astronomer and British engineer . Engineer and multi-field scientist, it is especially known to have the given first the periodicity of the Comet of 1682, which it fixed by calculation at approximately 76 years. At the time of the return of this comet in 1758, it was baptized of its name. It is one of the rare comets which bear another name that of their discoverer.

Biography

Childhood

The date of its birth is dubious: Halley believed for its part that it was about the October 29th 1656. He was born in the village from Hackney, small village of the surroundings of London, absorbed today by the capital. Of his/her mother we know only the name, Anne Halley, born Robinson. His/her father also prénommait Edmond, and it was a rich person soap and commercial of salts which had its fortune builds on the recent horrors of the bubonic plague, which had given to the Londoners the taste personal hygiene. This man was never afraid to devote all the money necessary to the education of his son, who very early appeared a boy curious and full with interest for science.

Of his childhood, one knows only few things, except what Halley himself agreed to confess: “ As of my more tender years, I devoted myself to the study of the Astronomie ”, writes it in his memories. “ to me a pleasure so large brought that it is impossible to explain it with which did not make this experiment. ”.

Without having any indirect evidence of it, it is however probable that Edmund Halley, hardly 10 years old, was brought to be interested in astronomy - and more particularly in comets - following the spectacular appearance in the London sky of two large comets of 1664 and 1665, that the popular superstition made responsible, for the first, of the great plague of London, and for the second, of large the fire which devastated the capital.

A few years later, Edmund Halley, always thanks to generosities and to the encouragement of his/her father, entered to the Saint-Paul school, one of best of all England, where the young man pointed out himself by his brilliant aptitudes. In 1672, it entered in Queen' S College of Oxford - where it will be pointed out in the same way -, but where it has misfortune to learn death from his mother a few months later, the October 24th 1672, little before its sixteenth birthday.

The March 10th 1675, Edmond Halley had boldness to write with the Astronomer Royal of England, John Flamsteed, to announce to him errors in the official tables of the positions of Jupiter and Saturn. Impressed by the capacities and especially the enthusiasm of the young man - whose calculations appeared right, but which knew in its letter to show all at the same time the respect due to its elder and the enthusiasm of its youth -, John Flamsteed will help it, the following year, to publish, at the nineteen years age, its first scientific article in the Philosophical Transactions , re-examined Royal Society of London, today still first learned society of the the United Kingdom.

Astronomer, scientist, engineer

Extremely on the recognition thus obtained by the scientific community, Halley decides to leave Oxford without passing his diploma, and that to embark for the island Sainte-Hélène, in order to draw up there the first southern sky chart . He is constant in this forwarding by Royal Society, which also succeeded in obtaining the support of the king Charles II. Its departure takes place for its blackjacks years, in November 1676. There will remain eighteen months there.

During these long months of observation, Halley not only will report in England the more precise chart which ever had been traced southern sky, but also several rich observations of lesson, of which in particular the influence of the Latitude over the period of the clocks with beam (due to a negligible difference of Centrifugal force on the level of the equator), and a census of Nébuleuse S never yet observed by Europeans. After the observation of a Transit of Mercury in front of the Sun, it published a talk on the method to be used to determine the distance Ground-Sun at the time of Venus a Transit, without alas on the occasion to proceed to it of alive sound.

Sailor except par, it studied, at the time of his voyages on board the Paramore , atmospheric circulation, the oceanic current , and establishes a detailed chart of the magnetic Déclinaison. He also designed the first weather chart , ancestor of that which is presented each evening on television. Impassioned Sea, he studied manners of many creatures watery, of which in particular the cuttlefish and the Esturgeon. He conceived even a method to preserve living the sail needle S, in order to sell them in full winter.

In contact with Isaac Newton, Halley wondered whether the attraction of a comet too passing close to the Earth could move the oceans until flooding continental areas: by this assumption, it was also one of the first to try to explain rationally the biblical Déluge . It was also the first to be wondered about the consequences of a collision of a comet with the Earth.

It tried to measure the size of the Atome, but without success. Spirit curious about all, it also studied the Roman history and the mechanisms of Horlogerie. Lastly, and it is undoubtedly it for which it was most known of alive sound, it designed and manufactured the first Diving bell. “ Thanks to this means, wrote it, I left 3 men during one hour three quarters under ten water pitch-stirrers, without the least disadvantage for them, and in a freedom to act as perfect as if they had been with the free air. ”. This invention functioned so that it founded a company of recovery of the goods of the ships shipwrecked men.

Of his own consent, Halley tasted rather regularly with the Opium, but without however falling into a physical or psychic dependence.

Edmund Halley and comets

Comets at the time of Edmund Halley

Pythagore was one of the rare scientists of its time to put forth the assumption that the comets were not only of nature identical to that of the Planet S (i.e. a celestial body moving), but which they had a clean Orbite:
“ Some of the Italians called Pythagoriciens says that the comet is one of planets, but that it appears only with very long intervals and only rises very little above the horizon. ” (Aristote, meteorology, Delivers I, chapter VI)
Although that is not clearly expressed, this opinion contains in germ the periodic idea of return of comets, celestial stars by nature.

Aristote, for its part, purely saw in comets of the atmospheric phenomena (“sublunary”), because the sky - constituted of the “ sphere of fixed stars ” - was declared like “ fixed and immutable ” in its system of the world. This design aristotelician of the universe will perdura several centuries, until Tycho Brahé calls it in question at the time of the observation of the Supernova of 1572: obviously, contrary to the assertion of Aristote and the Church, the skies were not immutable. The fatal blow was carried to this design of the world 5 years later, during the appearance of large comet of 1577, which remained visible during long months, making it possible Brahé to erect scaffolding with his/her colleagues the most various assumptions on these new celestial bodies.

However, if the Church were seen obliged to recognize the “planetary” nature of comets, their raison d'être, it, was not called into question: the comets were always regarded as divine signs, heralding generally the ire of the Creator. For this reason, the comets were to thus be unforeseeable phenomena, as could the being any divine message justified in answer to any human action.

For this reason also, one thus considered that, “ by nature ”, the orbit of comets was to be parabolic - assumption formulated by Johannes Hevelius as of the XVIIe century -, each comet carrying out one and single passage around the Sun. This theory was put up to the observations with the time: indeed, in the vicinity of the internal solar system (thus from the point of view of a terrestrial observer), it is very difficult to differentiate an ellipse very lengthened from the end of a parabola. However the precision of the instruments of the time was insufficient to be able to differentiate two so close orbits. The parabolic orbit of comets was thus the standard when the young person Edmund Halley started to observe the sky…

The challenge of the scientist

The first “official” observation of a comet by Halley is that which it did in 1680 - that one even which inspired with Pierre Bayle his " Thought on the comet " -, on a boat which crossed the Manche to bring it in France. It is Jean-Dominique Cassini, discoverer of the division of the Saturn's rings, which cordially accommodated it with the royal observatory of Paris, and which will switch the young man on the assumption of a periodic return of comets:
“ Mr Cassini made me the favor entrust its statements of comet whereas I prepared to leave the city; in addition to the observations which it carried out at the date of the March 18th (1681), it subjected a theory to me on its movement, namely that the comet is that one even which appeared in Tycho in the year 1577, that its revolution describes a large circle in which the Earth is included/understood. ”
Cassini had indeed noticed that three comets came from the same part of the sky with speed similar: if the paternity of the assumption of a periodic return of comets returns in Cassini, it is Halley who will take the subject sufficiently in heart to try to validate it scientifically. But, although the subject seems to impassion the young man, they are only ten years later that it will be harnessed with his demonstration.

In 1682, it observes the not very spectacular comet which was to bear its name later, but leaves of them only some notes in its notebook of observation. Its meeting with Isaac Newton, in August 1684, seems to revive the scientific heat of Halley, who had somewhat sunk in the routine after his meeting and his marriage with Mary Tooke near which - all testimonys agree on this point - he will live a idylle sincere and impassioned during nearly fifty-five years. The two scientists dedicate a major friendship, and it is together that it will nourish their passion for comets. Thus, taking again point-to-point the already made observations, and being based on work of Newton on the law of Gravitation, they will show that the comets were to have the same orbits as planets. When the major work of Newton in 1687 appears, Principia - undoubtedly one of the scientific works most remarkable of the 17th century - Halley writes as a foreword a vibrating homage to the genius of Newton.

It is thus at the 39 years age that Halley attacked the problem which later was going to ensure its larger claim to fame to him. For that, he undertook to count all the cometary passages of a recent and remote past. He in that was helped by the chance, his century being by a whim of nature more provided out of comets than the previous centuries. Its investigation made it go up until testimonys of Pline Old the or Sénèque. It recomputed the orbits of 24 comets having carried out a passage to the Périhélie between 1337 and 1698. It was a titanic task, meticulous person and long-term. He managed at the end of several years to isolate three passages having taken place in 1531, 1607 and 1682.

Although the correspondence seemed perfect between these data, Halley worried about the light differences, which could not be explained only by inaccuracies of measurement. Moreover, the interval varied of more than one year. Halley formulated the assumption that an unspecified force, still unexplained, was responsible for such variations, but could not convince itself some, for lack of rigorous scientific explanation. Opening some in Newton, this one suggested to him calculating the possible gravitational disturbances between its comet and other comets. Some calculations showed him the falseness of this assumption, but this one is enough sufficiently to overheat to him the spirit so that he undertook to calculate the disturbances caused by Jupiter and by Saturn (then last known planet of the Solar system). Calculations then showed an almost perfect correlation between its theory and the passages observed.

Extremely of these results, it published in 1705 the results of its work in a work entitled Synopsis of the astronomy of the comets , and in which it made prophecy - entirely scientific - return of its comet for Christmas 1758. Halley knew thus, by writing this study, which he would never see of sound living the confirmation of these calculations, the next passage having to be carried out the year of its 102 years.

He died on January 14th, 1742, after having seen dying his wife 4 years earlier, and his son in the same year.

Posthumous triumph

When Halley had predicted the return of comet for 1758, its prophecy hardly raised enthusiasm: indeed, this one was located more than one half-century in the future. And when Halley died in 1742, the obituaries lengthily insisted on its maritime forwardings, its discoveries and on the diving bell of which he was the inventor, and overlooked its cometary forecast, which fell into the lapse of memory.

However, in 1757, a French mathematician, Alexis Clairaut, made the decision to take again calculations of Halley so, by improving the precision of calculations, to more finely predict the date of return of comet. The times were short, calculations having to be remade before the reappearance of this one, in order to cross short to any charge of fraud. Calculations of gravitational interaction of comet with the Earth, Jupiter and Saturne were colossal for the weak time it had, a little more than one year. the mathematician Nicole-Queen Cattle shed of Brière Lepaute. Indeed, the prejudices of the time made that a woman, even of good birth, perfect education, of great scientific rigor, was entitled never to the consideration which a man could have drawn from the same talents. The historical retraction of the name of Mrs Lepaute also mainly due to Clairaut, which a woman jealous of the merit of Mrs Lepaute removed any mention of its name in order to “ like, pretentious but is deprived of some knowledge that it was. She managed to make make this injustice by a judicious but weak scientist, whom she had subjugated ”, according to the testimony of Lalande.

After months of calculations, the team of the three astronomers " officiels" in November 1758 announced that the comet would carry out its passage to the perihelion the April 13rd 1759. The world astronomical community - questioning for a part among it the prediction of Halley, always not seeing anything coming for Christmas 1758 - thus went back to feverishly scanning the sky. A few weeks later, the comet appeared at the exact place where had predicted it Halley, and reached its perihelion the March 13rd 1759, exactly a month before the date fixed by Lepaute, Lalande and Clairaut.

Three years before its death, E. Halley indicated: " If the return envisaged by us for year 1758 is carried out, the impartial posterity will not refuse to recognize that it was an English who announced it for the first time. " This wish was largely exaucé, since the community of the astronomers decided following this posthumous success, to give the name of Halley to this comet.

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