1-14-2008 Lecture 5 - It ran contrary to their sense. If...

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Lunar Eclipse Eclipses recur in the approximate 18 yrs 11-1/3 days ( Saros Cycle) Eclipse location and type may vary. 2.6 The Ancient Mystery of the Planets Planets known in Ancient Times Mercury – difficult to see, always close to Sun in sky Venus – very bright when visible, morning and evening “star” Mars – noticeably red Jupiter – very bright Saturn – moderately bright Retrograde motion: Like the Sun, planets usually appear to move eastward relative to the stars. But as we pass them by in our orbit, they move west relative to the stars for a few weeks or months. Noticeable over many nights; on a single night, a planet rises in east and sets in west. Apparent retrograde motion is hard to explain if you think that Earth is the center of the universe. Why did the ancient Greeks reject the notion that the Earth orbits the Sun?
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Unformatted text preview: It ran contrary to their sense. If the Earth rotated, then there should be a great wind as we moved through the air. Greeks knew that we should see stellar parallax if we orbited the Sun but they could not detect it. Parallax Angle Apparent shift of a stars position due to the Earths orbiting of the Sun The nearest stars are much farther away than the Greeks thought. So the parallax angles of the star are so small, that you need a telescope to observe them. Possible reasons why stellar parallax was undetectable: 1. Stars are so far away that stellar parallax is too small for naked eye to notice. 2. Earth does not orbit Sun; it is the center of the universe....
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This note was uploaded on 11/28/2011 for the course ASTRO 101 taught by Professor Hartmann,bergin during the Winter '08 term at University of Michigan.

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