By Glenn Wolfrom


The following is an excerpt from a longer article that appeared in the New Jersey Science Teachers’ Association BULLETIN, Vol. 28, No. 1, September, 1983.  Mr. Wolfrom is a member of the Science Department at Rancocas Valley Regional High School in Mount Holly, New Jersey.


          About the year 1680 Edmond Halley began investigating comets.  We still need to learn a lot about comets and in Halley’s day very little was known.  Comets were thought to travel in straight lines and no one knew that they returned periodically.  Halley traveled to Paris in the Fall of 1682 and on November 26, at 6:30 a.m. he observed a comet.


          Halley was a supporter of Newton and had financed the publication that was to be so important in the world of Physics, “The Pricipia”. Halley recognized that Newton’s law of gravitation could be applied not only to the orbits of planets, but to comets as well.  It was on this basis and armed also with the royal astronomer’s (Flamsteed) calculations of the path of the 1682 comet that Halley made his important contribution to comet studies.  “Now, many things lead me to believe that the comet of the year 1531, observed by Apian, is the same as that which, in the year 1607, was described by Kepler and Longomontauus, and which I saw myself, at its return, in 1682.”


          Halley delayed until 1705 before predicting the comet’s next return that he calculated to be in 1758.  Halley quelled his audaciousness by cautioning that any forecast was very uncertain.


          There was a good deal of skepticism and some detractors pointed out that since Halley was 49 years old, he would have to reach the age of 102 to see the comet return.  Halley died in 1742 at the age of eighty-six.


          As the year 1758 approached the French mathematician, Alexis Claude Clairaut, decided to more accurately compute the perihelion date for the comet.  Clairaut enlisted the aid of Joseph Lalande and Mme. Jean Anmdre Lepaute to compute this problem.


          For six months these dedicated mathematicians computed from morning till night, often even at meals, realizing that the comet was coming ever closer.  Lalande contracted an illness from this work that he said affected him for the rest of his life.  He was 25 and lived for another half-century until 1807. 


On November 14, 1758, Clairaut announced the time of perihelion passage to the Academy of Science:  April 13, 1759.  On Christmas day, 1758, a farmer near Dresden sighted the comet.  It’s interesting, I think, that Newton had been born on Christmas day, 1642.  The perihelion date was on March 12, 1759.  Clairaut’s prediction was a month off, which is not at all bad considering the crude data he had to work with.  From this time on the comet would be known as Halley’s Comet.


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