1	The Origin of Modern Astronomy
2	Ancient Greek Astronomy Models were generally wrong because they were based on wrong “first principles”, believed to be “obvious” and not questioned:
3	Ancient Greek Astronomers Aristotle (384 – 322 B.C.), major authority of philosophy until the late middle ages: Universe can be divided in 2 parts:
4	Aristotle’s Universe: Earth’s Shape Aristotle knew the Earth was round: Shadow of Earth during lunar eclipse Changing height of Polaris and celestial pole as you moved south Eratosthenes measured size of Earth to better than 20% ~200 BC, Greek living in Alexandria Egypt Observed that Sun was overhead at Syene on summer solstice Sun was 7^o to the south of zenith at Alexandria Circumference of Earth must be 360/7 times distance from Syene to Alexandria
5	Issues of Ancient Astronomy (I)
6	Issues of Ancient Astronomy (II)
7
8	The Copernican Revolution
9	Copernicus’ new (and correct) explanation for retrograde motion of the planets:
10	Tycho Brahe (1546 – 1601)
11	A Quadrant designed by Brahe
12
13
14	Eccentricities of Ellipses
15	Eccentricities of planetary orbits
16
17	Kepler’s Laws, #3 1619 Publishes third law, showing that there is a relationship orbital period and semi-major axis: Exact relationship is P² µ a³ . Outer planets orbit more slowly than inner ones Example: Earth P = 365 days, a = 1.00 AU. Mars p = 687 days, a = 1.524 AU Orbital Period of some asteroid with a = 9 AU ?
18
19	Major discoveries of Galileo (I): Moons of Jupiter (4 Galilean moons)
20	Major discoveries of Galileo (II):
21	Major discoveries of Galileo (III):
22	Galileo and the “Dialog” Written as a debate between 3 people Salviati Copernican advocate – (really Galileo) Sagredo Intelligent but uninformed Simplicio Aristotelian philosopher – not very bright Hoped to avoid earlier ruling by not directly advocating Copernican model Actually made things worse by convincing accusers they were “Simplicio” 1633 Inquisition condemns him for violating 1616 order Something like modern “contempt of court” ruling Proceeding not a re-argument of Copernican vs. Aristotelian debate But forced to recant, admitting “errors” Sentenced to life imprisonment –actually “house arrest” Dies in 1642 Pope John Paul II finally makes some amends 350 years later.
23	Historical Overview
24	Isaac Newton (1643 - 1727) Building on the results of Galileo and Kepler
25	The Universal Law of Gravity Any two bodies are attracting each other through gravitation, with a force proportional to the product of their masses and inversely proportional to the square of their distance:
26	Understanding Orbital Motion The universal law of gravity allows us to understand orbital motion of planets and moons:
27	Orbital Motion (II)
28	Circular Orbits: Limiting case of an ellipse. Centripetal acceleration (v²/r) caused by Gravity Period found by Kepler’s 3^rd Law just comes from this Given P and a (and G) we can find the mass of a planet or star
29	Orbital Motion (III): Geosynchronous Orbits
30	The Tides
31	Spring and Neap Tides
32	Acceleration of the Moon’s Orbital Motion
33	People and Contributions Nicolaus Copernicus 1473 - 1543 Heliocentric model Explanation of retrograde motion Tycho Brahe 1546 - 1601 Observations of changes in sky Accurate planet positions Johannes Kepler 1571 – 1630 Mathematical description of planetary orbits Galileo Galilei 1564 – 1642 Observations using telescope supporting Copernican model Isaac Newton 1642 – 1727 Physics to explain Kepler’s orbits