Copernicus, Kepler, Galileo, Newton

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·Shakespeare 1564-1616.

·Age of Exploration, Colonization.

·Supernovae, 1572, 1604 shook idea of heavens as unchanging.

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·Ptolemaic SystemPlanets appear to reverse motions at times.

·Ptolemy explained motions in terms of orbits (epicycles) carried on a larger orbit (deferent).

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·Ptolemaic SystemEpicycle deferent ratios were very close to modern values of planet/earth orbit ratios. System worked very well.

·Contrary to popular myths, Ptolemy's system was not overly cumbersome, and it accounted for subtleties like the uneven motion of the Sun

·It is not Ptolemy's fault he did such a good job that it took 1500 years to improve on him!

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How Ptolemy Dealt With Unequal Speeds

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Why this was a hot topic Alfonso the Wise of Castile published tables based on Ptolemy, 1200’s

Tables were out of date by 1500

System began to seem cumbersome and inelegant

Need for calendar reform

Gregorian Calendar, 1582

System was beginning to seem clumsy

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Nicolaus Copernicus 1473-1543 First known modern person to propose the Earth circles 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”

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Possible clues to Copernican idea

Epicycle motions for Venus and Mercury opposite other planets.

·Epicycle for Sun's motion appeared in schemes for all other planets.

·References to now-lost ideas of Aristarchus of Samos

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Johannes Kepler 1571-1630 A thoroughgoing medieval mystic

Left detailed accounts of his reasoning

Generally a much more interesting story than Copernicus

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The Platonic Solids

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Kepler’s Nested Spheres

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How Did Kepler Know the Spacing?

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The Kepler Solids

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