Lec05-Feb03

Lec05-Feb03 - Quiz QuesDon#1 What happens during...

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Unformatted text preview: 2/4/10 Quiz QuesDon #1 What happens during the apparent retrograde moDon of a planet? Astro 109 Lecture 5: Greek and Renaissance Astronomy A.  The planet rises in the west and sets in the east. B.  The planet appears to move westward with respect to the stars. C.  The planet moves backward through the sky. D.  The planet moves backward in its orbit. E.  The planet moves far from the eclipDc. Feb. 3 Feb. 3 Quiz QuesDon #2 Quiz QuesDon #3 Copernicus showed that the farther a planet is from the Sun, A.  B.  C.  D.  E.  Kepler deduced that a planet’s orbit the longer its sidereal period. the shorter its synodic period. the more ellipDcal is its orbit. the brighter it appears in the sky. the larger it is. Feb. 3 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. Feb. 3 Geocentric model Key Concepts •  geocentric and heliocentric models •  retrograde moDon •  orbital geometry Feb. 3 Feb. 3 1 2/4/10 ★ Retrograde moDon: Mars Parallax Feb 2006 July 2005 Feb. 3 Feb. 3 Credit Tunc Tezel, hZp://antwrp.gsfc.nasa.gov/apod/ap060422.html ★ Ptolemy’s Almagest (c. 150 AD) •  MeDculous analysis of planetary data to determine sizes and rotaDon rates of epicycles and deferents •  But values were ad hoc – no clear reasons why they had those parDcular values Feb. 3 Feb. 3 ★ Heliocentric model Nicolaus Copernicus •  much beZer explanaDon of retrograde moDon (1473 ­1543) •  sensible arrangement of orbits •  clear paZern in orbital data Feb. 3 Feb. 3 2 2/4/10 ★ Arrangement of the orbits Discussion QuesDon Inferior planet A.  Mars is brightest during the period of retrograde moDon. B.  Mars is faintest during the period of retrograde moDon. C.  Mars is brightest when its angular size is smallest. D.  Mars varies in brightness but is always the same distance from Earth. E.  The changes in brightness are caused by dust storms on Mars. Feb. 3 Superior planet Mercury, Venus The apparent brightness of Mars changes quite noDceably as it moves around its orbit. Which of the following is true? Mars, Jupiter, Saturn Feb. 3 Orbital data •  Transform from synodic period (as viewed from Earth) to sidereal period. (See Box 4 ­1.) •  Use geometry to derive relaDve sizes of orbits. Copernicus and epicycles •  Like Ptolemy, Copernicus assumed circular orbits. •  So he sDll needed epicycles to explain the data. Sidereal period vs. distance from Sun 14 12 10 “In no other way do we find a wonderful commensurability and a sure harmonious [email protected] between the size of the orbit and the planet’s period.” – Copernicus 8 6 4 •  In pracDce, Copernicus’s heliocentric model was not that much simpler than Ptolemy’s geocentric model. (quoted by Owen Gingerich in The Book Nobody Read) 2 0 Feb. 3 0 1 2 3 4 5 6 Feb. 3 Discussion QuesDon Tycho Brahe (1546 ­1601) Tycho’s rejecDon of Copernicus was based primarily on •  1572, supernova A.  B.  C.  D.  E.  •  1577, comet •  rich measurements of star and planet posiDons Feb. 3 his belief in circular orbits his belief in ellipDcal orbits his faulty assumpDon that stars are nearby his respect for the teachings of Aristotle his hatred of Poland IF Earth moves AND stars are nearby THEN we see parallax. Feb. 3 3 2/4/10 EllipDcal orbits Johannes Kepler (1571 ­1630) Feb. 3 Feb. 3 Galileo Galilei Phases of Venus (1564 ­1642) Feb. 3 Can’t fit the data? Change your hypothesis! Feb. 3 Discussion QuesDon Ptolemaic model Which phase of Venus provides the strongest evidence that Venus orbits the Sun rather than Earth? A.  B.  C.  D.  Feb. 3 new crescent quarter gibbous Feb. 3 4 2/4/10 Copernican model Jupiter’s moons Feb. 3 Feb. 3 Sunspots Our Moon Feb. 3 Feb. 3 5 ...
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