Download The Copernican Revolution: From Ptolemy's Model to Kepler's Laws and more Study Guides, Projects, Research Astronomy in PDF only on Docsity! 1 1 2 Phys 181-701 Astronomy 3 “The danger to which the success of revolutions is most exposed, is that of attempting them before the principles on which they proceed, and the advantages to result from them, are sufficiently seen and understood.” Thomas Paine - American Revolutionary “Anyone in a free society where the laws are unjust has an obligation to break the law.” Henry David Thoreau - American Philosopher 4 (rěv΄ə-lōō’shən)) 1. n A drastic and far-reaching change in ways of thinking and behaving. 2. n Orbital motion about a point, the planetary revolution about the sun. 5 The Copernican Revolution 1473 - 1542 6 Problems with Ptolemy There are problems with the Ptolemaic Model The solar system according to the Ptolemaic Model from 100 A.D. to 1500 2 7 Features Features… •Deferent Circles •Epicycles on the Deferents •Inferior planets are never more than 47º from the sun •Retrograde motion of mars is explained 8 • As the precision of astronomical measurements grew the need for adjustments to the model called for additional epicycles. • In 1252 King Alfonso X of Castile funded a 10 year project by Arab and Jewish astronomers to calculate extensive tables. • Calculations became horrendously complicated and even Alfonso suggested that the model should by simpler if it was to have any truth in it. 9 “Multiplicity ought not be posited without necessity.” William Occam – English Scholar - 1340 “Keep it simple, stupid.” Anonymous 20th Century Philosopher This principle is known as Occam’s Razor… 10 Copernican Theory… The motions of the planets would be more easily explained if the sun were at the center. 11 DeRevolutionibus, 1543… “Venus and Mercury revolve around the sun and cannot go nearer or further from it than the circles of their orbits permit…If, acting upon this supposition, we connect Saturn, Jupiter and Mars with the same center, keeping in mind the greater extent of their orbits…we cannot fail to see the explanation of the regular order of their motions. This proves sufficiently that their center belongs to the sun…” 12 Going Further… “The extent of the universe…is so great that…[the earth] disappears when compared to the sphere of the fixed stars.” “Although this may appear incomprehensible and contrary to the opinion of many, I shall, if God wills, make it clearer than the sun, at least to those who are not ignorant of mathematics.” 5 25 Working late on this lecture, the clock strikes midnight… And the hands line up. A little while later… And they aren’t lined up at all. I notice that they line up again sometime around 1:05 am. Is there some sort of a math rule that can predict when the hands will align? 26 A little scratch work and some calculations… Big deal… 27 Time period of mars If I use the hands of the clock as an analogy for th m tion of the planets… 28 Radius of mars’ orbit 29 Measurement 30 IMPORTANT • Occam’s Razor • Copernicus • Law of Ellipses • Law of Areas • Harmonic Law 6 31 EndNEXT TIME: Newton’s Law of Universal Gravitation
