Physics 202: Introduction to Astronomy – Lecture 3
Carsten Denker
Physics DepartmentCenter for Solar–Terrestrial
Research
January 25, 2006 Center 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, 2006 Center 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, 2006 Center for Solar-Terrestrial Research
Epicycle and Deferent
January 25, 2006 Center for Solar-Terrestrial Research
Mercury transit on 15 November 1999
January 25, 2006 Center for Solar-Terrestrial Research
Venus Transit 8 June 2004
January 25, 2006 Center 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, 2006 Center for Solar-Terrestrial Research
Phases of Venus in 2004
January 25, 2006 Center 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, 2006 Center for Solar-Terrestrial Research
Galileo Galilei (1564 – 1642)First telescopic observations of the Sun!
January 25, 2006 Center for Solar-Terrestrial Research
Retrograde Motion of Planets
January 25, 2006 Center for Solar-Terrestrial Research
Retrograde Motion of Mars in 2003
January 25, 2006 Center for Solar-Terrestrial Research