Astronomy 161 -- Autumn 2007 In-Class Quiz 2 Study Guide Unit 3: The Revolutions of the Heavenly Orbs ------------------------------------ Aristotelian World View Assumptions (uniform circular motion, fixed unmoving earth) Early Geocentric Systems Eudoxus, Pythagoras, Aristotle Epicyclic Systems Hipparchus & Ptolemy Early Heliocentric System Aristarchus of Samos Ptolemaic Geocentric System Epicycles Equants Preserving Appearances - esp. retrograde motion & change in brightness of superior planets at opposition. Problems: complex, no way to measure planetary distances Copernicus Motivations & Assumptions (disliked equant, wanted to restore uniform circular motion) Copernican Heliocentric System Sun at the center Earth rotates on its axis every 24 hours Earth orbits (revolves) around the sun once a year His use of epicycles and why he used them. Successes: a) explains superior & inferior planets b) explains retrograde motion c) gives a geometric way to measure planetary distances Problems: (a) moving earth (b) stellar parallaxes Tycho Brahe: his observations & their significance Johannes Kepler: his theoretical work & its significance Kepler's Three Laws of Planetary Motion First Law Second (Equal Areas) Law Third (Harmonic) Law Galileo's telescope observations & their significance The Moon Sunspots Phases of Venus Moons of Jupiter Isaac Newton: work and its significance Laws of Motion First Law (Law of Inertia) Second Law (F=ma) Third Law (Action & Reaction) Unit 4: Gravitation, Light, & Matter ---------------------------- Newtonian Gravity Inverse-Square Law Force Dependence of the gravitational force on masses and distance of the two bodies. Newton's Generalized forms of Kepler's Laws Shapes of Orbits Orbit about the Center of Mass Circular and Escape Velocity Measuring Masses with Newton's form of Kepler's 3rd Law Tides Basic causes of gravitational tides Earth Tides caused by the Sun and Moon Tidal Locking Tidal Evolution of the Moon's Orbit and Earth's Rotation Lunar Recession Increasing Length of the Day Gravity in the Solar System Gravitational Interactions among objects Lagrange Points The discovery of Neptune Slingshot orbits Orbital Resonances (Galilean Moons, Pluto)