Lecture 5 The Heliocentric Model of the Universe, Exercises of Art

Download Lecture 5 The Heliocentric Model of the Universe and more Exercises Art in PDF only on Docsity! 1 Lecture 5 The Heliocentric Model of the Universe January 3b, 2014 2 Aristarchus (310-230 BC) • Proposed Earth orbited the Sun. • More easily explained retrograde motion. • Animation 5 Parallax • The greater the distance, the smaller the parallax angle • The greater the baseline (distance from A to B), the greater the parallax angle. )( angleparallax (km) baseline 3.57 (km) distance (km) distance (km) baseline 3.57 )( angleparallax    or Distance Baseline 6 Distance and the Parallax-Second • A parsec is the distance that corresponds to one arc second of parallax when the baseline is 1 astronomical unit • 1.00 AU = 1.50×108 km   8 13 12 baseline (km) 1.00 pc 57.3 parallax angle ( ) 1.50 10 km 57.3 1 3600 ° 1 ly 3.09 10 km 9.46 10 km 1.00 pc 3.26 ly            7 A star shows a parallax angle of 0.10 arcsec when the Earth moves one AU. What is the distance to the star? 1 .0 0 pc 3 .2 6 pc 1 0 pc 0 .1 0 pc 0% 0%0%0% 0 of 5 A. 1.00 pc B. 3.26 pc C. 10 pc D. 0.10 pc 120 10 Nicholas Copernicus (1473-1543) • Heliocentric (sun centered) model of the Solar System. • De Revolutionibus Orbium Coelestium (1543) • Knew about work of Aristarchus 12 S S J V M E M Celestial Sphere • Heliocentric Model = Sun at center • Planets orbit the Sun • Moon orbits the Earth. • Circular orbits Basic Heliocentric View 13 Accuracy • NOTE: The heliocentric model did NOT predict positions better than the geocentric model – But it was simple. • Occam’s Razor: If choosing between competing theories that are all similarly accurate, choose the simplest one. 16 Observations of Venus • Venus has phases similar to the moon. • The apparent size of Venus changes with the phase. 17 Question • What would you expect to see if Venus orbited the Earth? • How does Galileo’s observation support the heliocentric model? 18 Geocentric Model of Venus 21 Tycho Brahe (1546-1601) • Supported geocentric model • Pre-dates invention of telescope • Observed supernova (1592) • Believed stars unchanging – “New” star must be near Earth 23 Tycho’s Supernova • Tried to measure distance to supernova using parallax. • No parallax observed – Why? – Supernova much more distant that originally thought. • Heavens are NOT unchanging 24 Tycho’s Observations • He was given an island for observatory by King of Denmark – “Uraniborg” • He designed state-of-the-art instruments to observe sky (all naked eye observations). • He made detailed observations of planetary and stellar positions. – His positions accurate up to 1 arcminute (1/60 of a degree) Planetary Configurations Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. _- Conjunction . SIU -alels conjunction 3 Inferior conjunction / Opposition Figure E1.9 28 Transit of Mercury Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Sunspots Courtesy of Dominique Dierick Figure E1.10 Greatest elongations of Mercury and Venus Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Mercury Venus Za Zan A re we 4 au Piety ZOOM Vas _ eA ~ Observer ai OO Sun below western horizon View from Space View from Earth Figure E1.11