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Unformatted text preview: 2/1/11 Quiz QuesGon #1 How did Ptolemy explain the observed retrograde moGon of Mars? Astro 109 Lecture 5: Greek and Renaissance Astronomy Feb. 1 A. Mars occasionally reverses the direcGon of its orbital moGon. B. Earth occasionally reverses the direcGon of its orbital moGon. C. Earth's faster orbital speed allows it to overtake and pass Mars. D. Mars moves on an epicycle. E. Copernicus had no explanaGon of Mars's retrograde moGon. Feb. 1 Quiz QuesGon #2 How did Copernicus explain the observed retrograde moGon of Mars? A. Mars occasionally reverses the direcGon of its orbital moGon. B. Earth occasionally reverses the direcGon of its orbital moGon. C. Earth's faster orbital speed allows it to overtake and pass Mars. D. Mars moves on an epicycle. E. Copernicus had no explanaGon of Mars's retrograde moGon. Feb. 1 Feb. 1 Quiz QuesGon #3 Kepler deduced that a planet's orbit A. B. C. D. E. is a circle with the Sun at the center. is a circle offset from the Sun. is an ellipse with the Sun at the center. is an ellipse with the Sun at one focus. is a hyperbola. Key Concepts what the Greeks knew geocentric and heliocentric models retrograde moGon orbital geometry Greeks knew Earth is round Shape of shadow during lunar eclipse Sky varies with laGtude Ships disappear over the horizon Feb. 1 Feb. 1 1 2/1/11 Eratosthenes Eratosthenes and the size of Earth Feb. 1 hWp://scienceblogs.com/startswithabang/2009/06/carnival_of_space_108_solsGce.php Feb. 1 hWp://www.wired.com/science/discoveries/news/2008/06/dayintech_0619 Aristarchus and the scale of the solar system Retrograde moGon: Mars hWp://www.astronomy.ohio-state.edu/~pogge/Ast161/Unit3/greek.html Feb. 1 Feb. 1 2003 Retrograde moGon: Mars Geocentric model "Epicycles" Feb 2006 July 2005 Credit Tunc Tezel, hWp://antwrp.gsfc.nasa.gov/apod/ap060422.html Feb. 1 Feb. 1 2 2/1/11 Heliocentric model Discussion QuesGon Most Greeks rejected the heliocentric model of the solar system because A. they thought planets had to follow perfect geometric shapes such as circles. B. the angle between any pair of stars varies month by month. C. they thought Aristotle was more clever than Aristarchus. D. they could not detect stellar parallax. E. it was not part of their religious beliefs. Feb. 1 cf. Aristarchus, c. 260 BC Feb. 1 Parallax Ptolemy's Almagest (c. 150 AD) MeGculous analysis of planetary data to determine sizes and rotaGon rates of epicycles and deferents But values were ad hoc no clear reasons why they had those parGcular values Feb. 1 Feb. 1 Nicolas Copernicus (1473-1543) Heliocentric model much beWer explanaGon of retrograde moGon sensible arrangement of orbits clear paWern in orbital data Feb. 1 Feb. 1 3 2/1/11 Arrangement of orbits Inferior planet Superior planet Orbital data Transform from synodic period (as viewed from Earth) to sidereal period (relaGve to stars). Use geometry to derive relaGve sizes of orbits. Sidereal period vs. distance from Sun 14 12 10 8 6 4 2 "In no other way do
we find a wonderful commensurability and a sure harmonious connec7on between the size of the orbit and the planet's period." Copernicus (quoted by Owen Gingerich in The Book Nobody Read) Mercury, Venus Feb. 1 Mars, Jupiter, Saturn Feb. 1 0 0 1 2 3 4 5 6 Discussion QuesGon How did Copernicus and Galileo deal with the problem of stellar parallax? A. They ignored the problem. B. They observed parallax. C. They said that the heliocentric model does not predict any parallax. D. They asserted that stars are too far away to show percepGble parallax. E. They blamed faulty observaGons. Copernicus and epicycles Like Ptolemy, Copernicus assumed circular orbits. Copernicus sGll needed epicycles to explain observaGons in detail. In pracGce, Copernicus's heliocentric model was not that much simpler than Ptolemy's geocentric model. Feb. 1 Feb. 1 Tycho Brahe (1546-1601) Johannes Kepler (1571-1630) 1572, supernova 1577, comet rich measurements of star and planet posiGons Feb. 1 Feb. 1 4 2/1/11 EllipGcal orbits Galileo Galilei (1564-1642) Can't fit the data? Change your hypothesis! Feb. 1 Feb. 1 hWp://scienceblogs.com/startswithabang/2010/09/geocentrism_was_galileo_wrong.php Discussion QuesGon Which phase of Venus provides the strongest evidence that Venus orbits the Sun rather than Earth? A. B. C. D. new crescent quarter full Phases of... hWp://www.nj.com/south/index.ssf/2009/02/venus_will_be_brightest_next_w.html Feb. 1 Feb. 1 Feb. 1 Feb. 1 5 2/1/11 Discussion QuesGon As seen from Earth, which of the following objects does not show a crescent phase? A. B. C. D. E. Mercury Venus the Moon Jupiter none of the above--all of these objects show crescent phases as seen from Earth Jupiter's moons Feb. 1 Feb. 1 Discussion QuesGon Galileo discovered four moons orbiGng Jupiter. Why was this important? A. It allowed Galileo to figure out where comets come from. B. It was the first measurement of highly ellipGcal orbits in the solar system. C. It showed that the Earth is not the only center of rotaGonal moGon in the solar system. D. It proved that planets must revolve about the Sun. E. It allowed the first determinaGon of the size of the solar system. Feb. 1 Feb. 1 Our Moon Sunspots Feb. 1 6 ...
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This note was uploaded on 03/24/2011 for the course PHYS 123 taught by Professor Wenkstern during the Spring '08 term at Rutgers.
- Spring '08