Copernicus, Kepler, Galileo, Newton
Steven Dutch, Natural and Applied Sciences,
University of Wisconsin - Green Bay
- Thomas Aquinas reconciles Aristotelian Philosophy with
- King Alfonso the Wise of Castile publishes Alfonsine tables,
based on Ptolemaic System, late 1200's.
- Concept of "Law of Nature" arises from medieval theology and
- Motion thought to be perfectly circular in heavens, rectilinear
- Printing invented 1457.
- Michelangelo, 1475-1564.
- Luther, 1483-1546.
- Protestant Reformation begins ca. 1520.
- Shakespeare 1564-1616.
- Age of Exploration, Colonization.
- Supernovae, 1572, 1604 shook idea of heavens as unchanging.
- Planets appear to reverse motions at times.
- Ptolemy explained motions in terms of orbits (epicycles) carried on a larger orbit (deferent).
- Epicycle 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!
- System began to seem cumbersome and inelegant.
- System inaccurate. Alfonsine tables out of date by 1500.
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
- Copernicus replaced epicycles with orbital motion of Earth.
- Less accurate than Ptolemaic system but conceptually simpler.
- Published as De Revolutionibus Orbium Coelestium (on the Revolutions of the Heavenly Spheres) 1542.
- Little immediate hostility. Earlier speculations on moving earth had been decreed heretical, hence moving earth idea could be lightly dismissed.
- One of most vigorous critics was Martin Luther.
Galileo's most original contributions to science were in
mechanics: he helped clarify concepts of acceleration, velocity, and
Galileo's effect on Astronomy
- Galileo did not invent the telescope (known since at least 1590).
- One of the first to use a telescope on the heavens. Found observational
evidence against traditional views.
- Craters on moon
- Phases of Venus
- Satellites of Jupiter
- 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.
Kepler (1572-1630), Brahe (1546-1601)
Kepler was a medieval mystic.
- One of the last of the "scientific astrologers."
- Attempted to explain spacing of planet orbits by reference to Platonic solids.
- Kepler was reluctant to abandon perfectly circular motion (but despite his mystic tendencies, he did when the evidence required it).
- Kepler found many numerological relationships among the planets, of which "Kepler's Laws" are the three that have proven to have a physical basis.
- Kepler's concept of the Sun as center of solar system may have had a
Need for observational data.
- Copernican theory based on same observational data as Ptolemaic, hence no more accurate.
- Kepler turned to Brahe, who had the most advanced observational data.
- Orbits are elliptical, Sun at one focus, nothing at other.
- Radius vector sweeps out equal areas in equal times.
- Square of period proportional to cube of distance.
Kepler and Galileo
- Galileo and Kepler corresponded.
- Galileo defended Copernican astronomy but never wrote about Kepler's model.
- Galileo may have been repelled by Kepler's mysticism.
- Moral: even the best and most innovative workers can sometimes fail to recognize a major advance.
Experiments on dispersion, nature of color, wave nature of light
Development of Calculus, 1665-1666
- Built on Galileo and others' concepts of instantaneous motion.
- Built on method of infinitesimals of Kepler (1616) and Cavalieri (1635).
- Priority conflict with Liebniz.
- Built in part on Kepler's concept of Sun as center of solar system,
- planets move faster near Sun.
- Inverse-square law.
- Once law known, can use calculus to drive Kepler's Laws.
- Unification Kepler's Laws; showed their common basis.
- Priority conflict with Hooke.
Priority conflicts (Hooke, Liebniz)
- 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.
Why was the Copernican Revolution so pivotal?
- Chance (science had to start somehow)
- Intellectually respectable pursuit, suitable for elite
- Don't get hands dirty
- Problem literally of cosmic significance
- Big problems tend to attract the best minds
- Opportunity to observe laws of nature in "pure" form
- Gravity and momentum 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,
- Often vigorous counter-responses published by others.
- Martin Mersenne (1588-1648), 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 arise in mid-1600's
Journals first published late 1600's (about 100 by 1800, nearly 50,000 now).
- By ca. 1700 books had become so specialized that publishers often
- refused to print them.
- Abstract journals (summaries) appear about 1840 (about 3000 now).
- About 6,000,000 scientific articles published annually now, worldwide.
- Information content (no. of journals, etc.) has doubled about every 15 years since 1700.
- Most of history's scientists are alive now, most knowledge gained in
- living memory. Same has been true since about 1700.
- Approaching saturation of resources?
Many early scientists were amateurs. Every science was founded by somebody not formally trained in it.
- Few opportunities for scientific employment
- Some scientists supported by occupations that allowed leisure.
- government sinecures (jobs with no responsibilities)
- independent wealth
- royal patronage
- Present forms of support very recent in origin
- corporate research
- government grant
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Created 20 May 1997
Last Update 24 January 1998
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