Wheels within Wheels ----- Wed, Jan 25, 2006
I. Satellite census
-- hierarchy of orbits in the universe
-- meaning of satellite
-- revolution vs. rotation
-- conjunction, opposition, and quadrature
-- "retrograde" motion (merely an illusion due to Earth's motion,
like the apparent backward motion of a car you are passing
on the highway)
-- solar system census:
Mercury
Venus
Earth
Mars
Ceres, Vesta, and the asteroid belt
Jupiter
Saturn
Uranus
Neptune
Pluto
comets
II. History of discovery of solar-system orbits
-- example of scientific method
- observation, model, better observation, better model, etc.
=> explanation
-- observations of planets : ancients
- strange patterns: "wandering stars"
-- first rigorous model: Ptolemy (~100)
- Earth at center of all orbits, complicated cycles and "equants"
-- competing model: Copernicus (~1540)
- Sun at center ("heliocentric"), much simpler orbits
-- better observations: Tycho (~1600)
- still before telescopes, Tycho was adept with "naked eye"
-- better model: Kepler (~1610)
- orbits are ellipses, Sun at one focus ("Kepler's laws")
-- still better observations: Galileo (~1610)
- used telescope, saw phases of Venus, moons around Jupiter
-- explanation: Newton (1687)
- "Newton's laws" of gravitation, motion -- revolution in mechanics