4. Revolution of the Spheres

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The `revolution' described in this week's lecture is a revolution of ideas. Copernicus started the revolution by recognizing the Earth as one of several similar planets, but he still used laws of planetary motion different from the laws applicable to motion on Earth. Newton completed the revolution by showing that planetary motion and terrestrial motion obey exactly the same laws. Between these two are Kepler, who wrote down the first correct laws of planetary motion, and Galileo, who found observational evidence for the Copernican system and clarified the nature of motion on Earth.



    Ch. 3-1 Copernicus devised the first comprehensive heliocentric cosmology
    Ch. 3-2 Tycho Brahe made astronomical observations that disproved ancient ideas about the heavens
    Ch. 3 KEPLER'S AND NEWTON'S LAWS (p. 60)
    Ch. 3-3 Kepler's laws describe orbital shapes, changing speeds, and the lengths of planetary years
    Ch. 3-4 Galileo's discoveries strongly supported a heliocentric cosmology
    Ch. 3-5 Newton formulated three laws that describe fundamental properties of physical reality
    Ch. 3-6 Newton's description of gravity accounts for Kepler's laws
    Ch. 4-8 Gravitational forces produce the tides and keep the same side of the Moon always facing the Earth

Web Resources:

Further Reading: Not part of this course, but highly recommended summer reading:

Homework 4: Planetary Positions, due 9/25.

Quiz 4: Kepler's Laws, given 9/20.

Joshua E. Barnes (barnes@ifa.hawaii.edu)

Last modified: September 21, 2001