sea diving bell。 hewrote authoritatively on magnetism； tides； and the motions of the planets； and fondly on theeffects of opium。 he invented the weather map and actuarial table； proposed methods forworking out the age of the earth and its distance from the sun； even devised a practicalmethod for keeping fish fresh out of season。 the one thing he didn鈥檛 do； interestingly enough；was discover the et that bears his name。 he merely recognized that the et he saw in1682 was the same one that had been seen by others in 1456； 1531； and 1607。 it didn鈥檛bee halley鈥檚 et until 1758； some sixteen years after his death。
for all his achievements； however； halley鈥檚 greatest contribution to human knowledge maysimply have been to take part in a modest scientific wager with two other worthies of his day：
robert hooke； who is perhaps best remembered now as the first person to describe a cell； andthe great and stately sir christopher wren； who was actually an astronomer first and architectsecond； though that is not often generally remembered now。 in 1683； halley； hooke； andwren were dining in london when the conversation turned to the motions of celestial objects。
it was known that planets were inclined to orbit in a particular kind of oval known as anellipse鈥斺�渁 very specific and precise curve；鈥潯o quote richard feynman鈥攂ut it wasn鈥檛understood why。 wren generously offered a prize worth forty shillings （equivalent to a coupleof weeks鈥櫋ay） to whichever of the men could provide a solution。
hooke； who was well known for taking credit for ideas that weren鈥檛 necessarily his own；claimed that he had solved the problem already but declined now to share it on the interestingand inventive grounds that it would rob others of the satisfaction of discovering the answer forthemselves。 he would instead 鈥渃onceal it for some time； that others might know how to valueit。鈥潯f he thought any more on the matter； he left no evidence of it。 halley； however； becameconsumed with finding the answer； to the point that the following year he traveled tocambridge and boldly called upon the university鈥檚 lucasian professor of mathematics； isaacnewton； in the hope that he could help。
newton was a decidedly odd figure鈥攂rilliant beyond measure； but solitary； joyless； pricklyto the point of paranoia； famously distracted （upon swinging his feet out of bed in the morninghe would reportedly sometimes sit for hours； immobilized by the sudden rush of thoughts tohis head）； and capable of the most riveting strangeness。 he built his own laboratory； the firstat cambridge； but then engaged in the most bizarre experiments。 once he inserted a bodkin鈥攁 long needle of the sort used for sewing leather鈥攊nto his eye socket and rubbed it around鈥渂etwixt my eye and the bone as near to ＇the＇ backside of my eye as i could鈥潯ust to see whatwould happen。 what happened； miraculously； was nothing鈥攁t least nothing lasting。 onanother occasion； he stared at the sun for as long as he could bear； to determine what effect itwould have upon his vision。 again he escaped lasting damage； though he had to spend somedays in a darkened room before his eyes forgave him。
set atop these odd beliefs and quirky traits； however； was the mind of a supreme genius鈥攖hough even when working in conventional channels he often showed a tendency topeculiarity。 as a student； frustrated by the limitations of conventional mathematics； heinvented an entirely new form； the calculus； but then told no one about it for twenty…sevenyears。 in like manner； he did work in optics that transformed our understanding of light andlaid the foundation for the science of spectroscopy； and again chose not to share the results forthree decades。
for all his brilliance； real science accounted for only a part of his interests。 at least half hisworking life was given over to alchemy and wayward religious pursuits。 these were not meredabblings but wholehearted devotions。 he was a secret adherent of a dangerously hereticalsect called arianism； whose principal tenet was the belief that there had been no holy trinity（slightly ironic since newton鈥檚 college at cambridge was trinity）。 he spent endless hoursstudying the floor plan of the lost temple of king solomon in jerusalem （teaching himselfhebrew in the process； the better to scan original texts） in the belief that it held mathematicalclues to the dates of the second ing of christ and the end of the world。 his attachment toalchemy was no less ardent。 in 1936； the economist john maynard keynes bought a trunk ofnewton鈥檚 papers at auction and discovered with astonishment that they were overwhelminglypreoccupied not with optics or planetary motions； but with a single…minded quest to turn basemetals into precious ones。 an analysis of a strand of newton鈥檚 hair in the 1970s found itcontained mercury鈥攁n element of interest to alchemists； hatters； and thermometer…makersbut almost no one else鈥攁t a concentration some forty times the natural level。 it is perhapslittle wonder that he had trouble remembering to rise in the morning。
quite what halley expected to get from him when he made his unannounced visit in august1684 we can only guess。 but thanks to the later account of a newton confidant； abrahamdemoivre； we do have a record of one of science鈥檚 most historic encounters：
in 1684 drhalley came to visit at cambridge ＇and＇ after they had some timetogether the drasked him what he thought the curve would be that would bedescribed by the planets supposing the force of attraction toward the sun to bereciprocal to the square of their distance from it。
this was a reference to a piece of mathematics known as the inverse square law； which halleywas convinced lay at the heart of the explanation； though he wasn鈥檛 sure exactly how。
srisaac replied immediately that it would be an ＇ellipse＇。 the doctor； struck withjoy & amazement； asked him how he knew it。 鈥榳hy；鈥櫋aith he； 鈥榠 have calculatedit；鈥櫋hereupon drhalley asked him for his calculation without farther delay；srisaac looked among his papers but could not find it。
this was astounding鈥攍ike someone saying he had found a cure for cancer but couldn鈥檛remember where he had put the formula。 pressed by halley； newton agreed to redo thecalculations and produce a paper。 he did as promised； but then did much more。 he retired fortwo years of intensive reflection and scribbling； and at length produced his masterwork： thephilosophiae naturalis principia mathematica or mathematical principles of naturalphilosophy； better known as the principia 。
once in a great while； a few times in history； a human mind produces an observation soacute and unexpected that people can鈥檛 quite decide which is the more amazing鈥攖he fact orthe thinking of it。 principia was one of those moments。 it made newton instantly famous。 for the rest of his life he would be draped with plaudits and honors； being； among much else；the first person in britain knighted for scientific achievement。 even the great germanmathematician gottfried von leibniz； with whom newton had a long； bitter fight over priorityfor the invention of the calculus； thought his contributions to mathematics equal to all theaccumulated work that had preceded him。 鈥渘earer the gods no mortal may approach；鈥潯rotehalley in a sentiment that was endlessly echoed by his contemporaries and by many otherssince。
although the principia has been called 鈥渙ne of the most inaccessible books ever written鈥�
（newton intentionally made it difficult so that he wouldn鈥檛 be pestered by mathematical鈥渟matterers；鈥潯s he called them）； it was a beacon to those who could follow it。 it not onlyexplained mathematically the orbits of heavenly bodies； but also identified the attractive forcethat got them moving in the first place鈥攇ravity。 suddenly every motion in the universe madesense。
at principia 鈥檚 heart were newton鈥檚 three laws of motion （which state； very baldly； that athing moves in the direction in which it is pushed； that it will keep moving in a straight lineuntil some other force acts to slow or deflect it； and that every action has an opposite andequal reaction） and his universal law of gravitation。 this states that every object in theuniverse exerts a tug