Physics 202: Introduction to Astronomy – Lecture 3 Carsten Denker Physics Department Center for Solar–Terrestrial Research

January 25, 2006Center for Solar-Terrestrial Research Chapter 1.2 – 1.3  Planetary motion  Retrograde motion  Geocentric model  Aristotle  Epicycle  Deferent  Ptolemaic model  Aristarchus of Samos  Heliocentric model  Copernican revolution  Modern Astronomy  The Scientific Method Theory Predictions Observations  Galilean moons  Venus phases  Sunspots

January 25, 2006Center for Solar-Terrestrial Research Ancient Greek  Physical (geocentric) model of the cosmos by Aristotle (384 – 322 BC)  Mathematical model of planetary motion by Ptolemy (100 – 170), terrestrial/celestial sphere, basic elements: earth, water air, and fire/quintessence The Aristotelian cosmos. The Earth sits motionless at the center of the universe, and the outer sphere, the Primum Mobile, is assumed to undergo a full revolution in 24 hours.

January 25, 2006Center for Solar-Terrestrial Research Epicycle and Deferent

January 25, 2006Center for Solar-Terrestrial Research Mercury transit on 15 November 1999

January 25, 2006Center for Solar-Terrestrial Research Venus Transit 8 June 2004

January 25, 2006Center for Solar-Terrestrial Research The Phases of Venus  Why did Plato propose that all heavenly motion was uniform and circular?  How do the epicycles of Mercury and Venus differ from those of Mars, Jupiter, and Saturn?

January 25, 2006Center for Solar-Terrestrial Research Phases of Venus in 2004

January 25, 2006Center for Solar-Terrestrial Research Nicholas Copernicus (1473–1543)  De Revolutionibus Orbium Coelestum in 1543  Heliocentric planetary model: The Sun is at the center of all planetary motions, except for the Moon which orbits Earth. Under this arrangement the orbital speed of planets decreases steadily outwards, and the outer sphere of fixed stars is truly motionless. In Copernicus' original model the Earth has three motions: a daily 24-hr axial rotation, a yearly orbital motion about the Sun, and a third motion, somewhat related to precession which Copernicus thought necessary to properly reproduce ancient observations.

January 25, 2006Center for Solar-Terrestrial Research Galileo Galilei (1564 – 1642) First telescopic observations of the Sun!

January 25, 2006Center for Solar-Terrestrial Research Retrograde Motion of Planets

January 25, 2006Center for Solar-Terrestrial Research Retrograde Motion of Mars in 2003

January 25, 2006Center for Solar-Terrestrial Research