哥白尼,开普勒,伽利略,牛顿简介课件.ppt

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1、Copernicus, Kepler, Galileo, Newton How did we Discover the Earth is Round? Traditional: as a ship sails away, the hull diasppears below the horizon before the sails Problem: ancient ships were so tiny they would be mere specks on the horizon. More likely: someone on a ship saw the land come into vi

2、ew How did we Discover the Earth is Round? Other possibilities: storm clouds with bases below the horizon Why is there a horizon at all? Why cant we just see forever? Contrary to myth, the knowledge of a round earth was never, NEVER forgotten during the Middle Ages Constellations and Culture A Myth

3、in the Autumn Sky A Portion of the Northern Sky The Northern Cross The Traditional ConstellationWhy Didnt the Ancients Picture this as a Cross? The Southern Cross A Star Map Western Constellations Chinese Constellations The Inca “Dark Constellations” Copernicus: Precursory events Thomas Aquinas reco

4、nciles Aristotelian Philosophy with Christianity. King Alfonso the Wise of Castile publishes Alfonsine tables, based on Ptolemaic System, late 1 2 0 0 s. Concept of Law of Nature arises from medieval theology and philosophy. Ideal motion thought to be perfectly circular in heavens, rectilinear on ea

5、rth. Immediate Setting Printing invented 1 4 5 7 . Michelangelo, 1 4 7 5 -1 5 6 4 . Luther, 1 4 8 3 -1 5 4 6 . Protestant Reformation begins ca. 1 5 2 0 . Shakespeare 1 5 6 4 -1 6 1 6 . Age of Exploration, Colonization. Supernovae, 1 5 7 2 , 1 6 0 4 shook idea of heavens as unchanging. Ptolemaic Sys

6、tem Planets appear to reverse motions at times. Ptolemy explained motions in terms of orbits (epicycles) carried on a larger orbit (deferent). Ptolemaic System Epicycle deferent ratios were very close to modern values of planet/earth orbit ratios. System worked very well. Contrary to popular myths,

7、Ptolemys system was not overly cumbersome, and it accounted for subtleties like the uneven motion of the Sun It is not Ptolemys fault he did such a good job that it took 1 5 0 0 years to improve on him! How Ptolemy Dealt With Unequal Speeds Why this was a hot topic Alfonso the Wise of Castile publis

8、hed tables based on Ptolemy, 1 2 0 0 s Tables were out of date by 1 5 0 0 System began to seem cumbersome and inelegant Need for calendar reform Gregorian Calendar, 1 5 8 2 System was beginning to seem clumsy Nicolaus Copernicus 1 4 7 3 -1 5 4 3 First known modern person to propose the Earth circles

9、 the Sun Not known how he arrived at the idea Died just as theory was published Not much story to tell Luther; “this fool wants to overturn the whole science of astronomy” Possible clues to Copernican idea Epicycle motions for Venus and Mercury opposite other planets. Epicycle for Suns motion appear

10、ed in schemes for all other planets. References to now-lost ideas of Aristarchus of Samos Johannes Kepler 1 5 7 1 -1 6 3 0 A thoroughgoing medieval mystic Left detailed accounts of his reasoning Generally a much more interesting story than Copernicus The Platonic Solids Keplers Nested Spheres How Di

11、d Kepler Know the Spacing? The Kepler Solids The Poinsot Solids Strange Start - Good Finish Kepler started off with mystical ideas, and ended up correctly describing the motions of the planets. How can this be? Science often proceeds by a process of successive approximation Make an assumption See ho

12、w it fits reality, Modify it (junk it if necessary) and try again. After a few iterations of successive approximation you can be very far from your starting point, Even fairly strange initial assumptions can lead to correct results. Successive Approximation differs profoundly from circular reasoning

13、, In circular reasoning, you start off with an assumption, Accept, reject, or modify observations to fit the assumption, Then use the results as proof of the assumption. People who engage in circular reasoning almost never scrap or modify their initial hypothesis The whole point of circular reasonin

14、g is to justify the initial hypothesis at all costs. Keplers Laws Planets travel around the Sun in elliptical orbits with the Sun at one focus. A line from the planet to the Sun sweeps out equal areas in equal times. The square of a planets period in years and its distance cubed are proportional. Ho

15、w Did Kepler Do It? One Mars year (6 8 7 days) = 2 Earth years (7 3 0 days) minus 4 3 days After 6 8 7 days, Mars is in the same place in its orbit, but Earth is not Mars appears to be in a different location in the sky How Did Kepler Do It? Tycho Brahe 1 5 4 6 -1 6 0 1 Tycho really did live the out

16、rageous lifestyle shown in the video Really did have a gold nosepiece. He died the way he lived. He was hitting up some noble personage for patronage and support and, fearing that somebody else might upstage him, refused to leave to go to the bathroom. He developed a bladder infection and died. A Ne

17、at Coincidence thats Too Neat Rosenkranz and Guldenstern are DeadWho were they? Hamlet Hamlets Uncle has: Murdered his father Married his mother Usurped Hamlets Crown Hamlet is Depressed How Much does Hamlet Know? Enter Rosenkranz and Guldenstern Hamlet is supposed to take place in late Viking times

18、 (ca. 1 0 0 0 A.D.) Rosenkranz and Guldenstern are student friends of Hamlets from the University at Wittenberg Which doesnt exist yet Recruited by Hamlets uncle to console (spy on) him. Exit Rosenkranz and Guldenstern The king sends the trio to England with a sealed letter instructing the king of E

19、ngland (a relative) to kill Hamlet Hamlet switches letters on his ex-friends Hamlet has it out with the king Bodies all over the stage, curtain falls See you at the cast party What does this have to do with the planets? Tycho had published a widely-sold book Modest chap that he was, he included a po

20、rtrait and 1 6 crests showing his lineage over four generations Tycho was Danish His estate was right across the strait from Elsinore Castle Tycho and Shakespeare Guess what two of the names on the crests are Tycho and Shakespeare had a mutual acquaintance Clearly this was an inside joke for audienc

21、es in the know So Whos Galileo (1 5 6 4 -1 6 4 2 )? Galileo did not invent the telescope (known since at least 1 5 9 0 ). One of the first to use a telescope on the heavens. Found observational evidence that challenged traditional views. Craters on moon Phases of Venus Satellites of Jupiter Galileo

22、Others independently used telescopes on celestial objects at nearly the same time. Galileo had the best publicity. Main impact: An aggressive popularizer of Copernican viewpoint and satirist of Aristotelian physics. Very much like a 1 7 th century Carl Sagan Kepler and Galileo Galileo and Kepler cor

23、responded. Galileo defended Copernican astronomy but never wrote about Keplers model. Galileo may have been repelled by Keplers mysticism. Moral: even the best and most innovative workers can sometimes fail to recognize a major advance. Why was the Copernican Revolution so pivotal? Chance (science h

24、ad to start somehow) Intellectually respectable pursuit, suitable for elite Dont get hands dirty Problem literally of cosmic significance Big problems tend to attract the best minds Why was the Copernican Revolution so pivotal? Opportunity to observe laws of nature in pure form Gravity and momentum

25、are the only laws at work Uncomplicated by friction, air resistance, etc. In a sense, the ancients were right; the heavens are more harmonious than Earth. The Scientific Establishment Earliest means of communication, privately published books, pamphlets, letters. Often vigorous counter-responses pub

26、lished by others. Martin Mersenne (1 5 8 8 -1 6 4 8 ), French mathematician, copied and distributed letters, acted as clearing-house. Nicknamed Post-Box of Europe. Good analogy to informal Internet discussion networks today. Scientific Societies and Journals First in mid-1 6 0 0 s Journals first pub

27、lished late 1 6 0 0 s (about 1 0 0 by 1 8 0 0 , nearly 5 0 ,0 0 0 now). By ca. 1 7 0 0 books had become so specialized that publishers often refused to print them. About 6 ,0 0 0 ,0 0 0 scientific articles published annually now, worldwide. Scientific Societies and Journals Information content has d

28、oubled about every 1 5 years since 1 7 0 0 . Most of historys scientists are alive now, most knowledge gained in living memory Same has been true since about 1 7 0 0 . Approaching saturation of resources? Scientific Support Many early scientists were amateurs. Every science was founded by somebody n

29、ot formally trained in it. Few opportunities for scientific employment until 1 9 th century physicians engineers Scientific Support Many early scientists supported by occupations that allowed leisure. clergy government sinecures (jobs with no responsibilities) independent wealth royal patronage Pres

30、ent forms of support very recent in origin corporate research government grant Priority conflicts Newton had disputes with Robert Hooke about discovery of gravity, and Liebniz over the invention of Calculus Have occurred since earliest days of science even when workers were few. Major problems attract many workers, most attention: challenge, prestige Solutions often emerge simultaneously from many sources.