Wednesday, January 14, 2009

January 14: Edmond Halley

Edmond Halley 
November 8, 1656 - January 14, 1742 

Edmond Halley was a British astronomer, geophysicist, mathematician, meteoroligist and physicist. 

One problem that attracted his attention was the proof of Kepler's laws of planetary motion. In August 1684 he went to Cambridge to discuss this with Isaac Newton, only to find that Newton had solved the problem but published nothing. Halley convinced him to write the Principia Mathematica Philosophiae Naturalis (1687), which was published at Halley's expense.

Edmond Halley is perhaps best known for Halley's Comet, which was the first comet to be recognized as periodic. Perceiving that the observed characteristics of a comet of 1682 were nearly the same as those of two comets which had appeared in 1531 (observed by Petrus Apianus) and 1607 (observed by Johannes Kepler), Halley concluded that all three comets were in fact the same object returning every 76 years. After a rough estimate of the perturbations the comet would sustain from the attraction of the planets, he predicted its return for 1758. Halley's prediction of the comet's return proved to be correct. Halley himself did not live to see the comet's return, having died in 1742.

The Moon crater Halley and a crater on Mars are named in his honor.

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