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mong¡¡a¡¡score¡¡or¡¡so¡¡of¡¡incorrect¡¡ones£»¡¡Kepler¡¡was¡¡able¡¡to¡¡demonstrate¡¡to¡¡his¡¡own¡¡satisfaction¡¡and¡¡to¡¡that¡¡of¡¡subsequent¡¡observers¡£¡¡Stated¡¡in¡¡a¡¡few¡¡words£»¡¡these¡¡theories£»¡¡which¡¡have¡¡come¡¡to¡¡bear¡¡the¡¡name¡¡of¡¡Kepler's¡¡Laws£»¡¡are¡¡the¡¡following£º¡¡1¡£¡¡That¡¡the¡¡planetary¡¡orbits¡¡are¡¡not¡¡circular£»¡¡but¡¡elliptical£»¡¡the¡¡sun¡¡occupying¡¡one¡¡focus¡¡of¡¡the¡¡ellipses¡£¡¡2¡£¡¡That¡¡the¡¡speed¡¡of¡¡planetary¡¡motion¡¡varies¡¡in¡¡different¡¡parts¡¡of¡¡the¡¡orbit¡¡in¡¡such¡¡a¡¡way¡¡that¡¡an¡¡imaginary¡¡line¡¡drawn¡¡from¡¡the¡¡sun¡¡to¡¡the¡¡planetthat¡¡is¡¡to¡¡say£»¡¡the¡¡radius¡¡vector¡¡of¡¡the¡¡planet's¡¡orbitalways¡¡sweeps¡¡the¡¡same¡¡area¡¡in¡¡a¡¡given¡¡time¡£

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GALILEO¡¡GALILEI¡¡While¡¡Kepler¡¡was¡¡solving¡¡these¡¡riddles¡¡of¡¡planetary¡¡motion£»¡¡there¡¡was¡¡an¡¡even¡¡more¡¡famous¡¡man¡¡in¡¡Italy¡¡whose¡¡championship¡¡of¡¡the¡¡Copernican¡¡doctrine¡¡was¡¡destined¡¡to¡¡give¡¡the¡¡greatest¡¡possible¡¡publicity¡¡to¡¡the¡¡new¡¡ideas¡£¡¡This¡¡was¡¡Galileo¡¡Galilei£»¡¡one¡¡of¡¡the¡¡most¡¡extraordinary¡¡scientific¡¡observers¡¡of¡¡any¡¡age¡£¡¡Galileo¡¡was¡¡born¡¡at¡¡Pisa£»¡¡on¡¡the¡¡18th¡¡of¡¡February¡¡£¨old¡¡style£©£»¡¡1564¡£¡¡The¡¡day¡¡of¡¡his¡¡birth¡¡is¡¡doubly¡¡memorable£»¡¡since¡¡on¡¡the¡¡same¡¡day¡¡the¡¡greatest¡¡Italian¡¡of¡¡the¡¡preceding¡¡epoch£»¡¡Michael¡¡Angelo£»¡¡breathed¡¡his¡¡last¡£¡¡Persons¡¡fond¡¡of¡¡symbolism¡¡have¡¡found¡¡in¡¡the¡¡coincidence¡¡a¡¡forecast¡¡of¡¡the¡¡transit¡¡from¡¡the¡¡artistic¡¡to¡¡the¡¡scientific¡¡epoch¡¡of¡¡the¡¡later¡¡Renaissance¡£¡¡Galileo¡¡came¡¡of¡¡an¡¡impoverished¡¡noble¡¡family¡£¡¡He¡¡was¡¡educated¡¡for¡¡the¡¡profession¡¡of¡¡medicine£»¡¡but¡¡did¡¡not¡¡progress¡¡far¡¡before¡¡his¡¡natural¡¡proclivities¡¡directed¡¡him¡¡towards¡¡the¡¡physical¡¡sciences¡£¡¡Meeting¡¡with¡¡opposition¡¡in¡¡Pisa£»¡¡he¡¡early¡¡accepted¡¡a¡¡call¡¡to¡¡the¡¡chair¡¡of¡¡natural¡¡philosophy¡¡in¡¡the¡¡University¡¡of¡¡Padua£»¡¡and¡¡later¡¡in¡¡life¡¡he¡¡made¡¡his¡¡home¡¡at¡¡Florence¡£¡¡The¡¡mechanical¡¡and¡¡physical¡¡discoveries¡¡of¡¡Galileo¡¡will¡¡claim¡¡our¡¡attention¡¡in¡¡another¡¡chapter¡£¡¡Our¡¡present¡¡concern¡¡is¡¡with¡¡his¡¡contribution¡¡to¡¡the¡¡Copernican¡¡theory¡£¡¡Galileo¡¡himself¡¡records¡¡in¡¡a¡¡letter¡¡to¡¡Kepler¡¡that¡¡he¡¡became¡¡a¡¡convert¡¡to¡¡this¡¡theory¡¡at¡¡an¡¡early¡¡day¡£¡¡He¡¡was¡¡not¡¡enabled£»¡¡however£»¡¡to¡¡make¡¡any¡¡marked¡¡contribution¡¡to¡¡the¡¡subject£»¡¡beyond¡¡the¡¡influence¡¡of¡¡his¡¡general¡¡teachings£»¡¡until¡¡about¡¡the¡¡year¡¡1610¡£¡¡The¡¡brilliant¡¡contributions¡¡which¡¡he¡¡made¡¡were¡¡due¡¡largely¡¡to¡¡a¡¡single¡¡discoverynamely£»¡¡that¡¡of¡¡the¡¡telescope¡£¡¡Hitherto¡¡the¡¡astronomical¡¡observations¡¡had¡¡been¡¡made¡¡with¡¡the¡¡unaided¡¡eye¡£¡¡Glass¡¡lenses¡¡had¡¡been¡¡known¡¡since¡¡the¡¡thirteenth¡¡century£»¡¡but£»¡¡until¡¡now£»¡¡no¡¡one¡¡had¡¡thought¡¡of¡¡their¡¡possible¡¡use¡¡as¡¡aids¡¡to¡¡distant¡¡vision¡£¡¡The¡¡question¡¡of¡¡priority¡¡of¡¡discovery¡¡has¡¡never¡¡been¡¡settled¡£¡¡It¡¡is¡¡admitted£»¡¡however£»¡¡that¡¡the¡¡chief¡¡honors¡¡belong¡¡to¡¡the¡¡opticians¡¡of¡¡the¡¡Netherlands¡£¡¡As¡¡early¡¡as¡¡the¡¡year¡¡1590¡¡the¡¡Dutch¡¡optician¡¡Zacharias¡¡Jensen¡¡placed¡¡a¡¡concave¡¡and¡¡a¡¡convex¡¡lens¡¡respectively¡¡at¡¡the¡¡ends¡¡of¡¡a¡¡tube¡¡about¡¡eighteen¡¡inches¡¡long£»¡¡and¡¡used¡¡this¡¡instrument¡¡for¡¡the¡¡purpose¡¡of¡¡magnifying¡¡small¡¡objectsproducing£»¡¡in¡¡short£»¡¡a¡¡crude¡¡microscope¡£¡¡Some¡¡years¡¡later£»¡¡Johannes¡¡Lippershey£»¡¡of¡¡whom¡¡not¡¡much¡¡is¡¡known¡¡except¡¡that¡¡he¡¡died¡¡in¡¡1619£»¡¡experimented¡¡with¡¡a¡¡somewhat¡¡similar¡¡combination¡¡of¡¡lenses£»¡¡and¡¡made¡¡the¡¡startling¡¡observation¡¡that¡¡the¡¡weather¡­vane¡¡on¡¡a¡¡distant¡¡church¡­steeple¡¡seemed¡¡to¡¡be¡¡brought¡¡much¡¡nearer¡¡when¡¡viewed¡¡through¡¡the¡¡lens¡£¡¡The¡¡combination¡¡of¡¡lenses¡¡he¡¡employed¡¡is¡¡that¡¡still¡¡used¡¡in¡¡the¡¡construction¡¡of¡¡ope

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