Download Astronomy: Eclipses, Moon Phases, and Early Observations and more Study notes Astronomy in PDF only on Docsity! 1 1 2 Astronomy Phys 181-701 3 “That’s no moon…That’s a space station!” Obi Wan Kenobi – STARWARS “The sun, with all those planets revolving around it and dependent on it, can still ripen a bunch of grapes as if it had nothing else in the universe to do.” Galileo Galilei 4 ASTRONOMY The study of matter and energy in our Universe and its evolution over time. 5 Early Observations The Sun and Moon 6 ECLIPSES GREEK ~ ekleipsis Abandonment •580’s B.C. Herodotus reports that a war between the Lydians and the Medes was ended by a solar eclipse that took both armies by surprise during a battle. •1504 Christopher Columbus convinced Jamaicans to aid him by threatening that the Christian god would swallow the sun in anger, and event which then proceeded, right on schedule. 2 7 SHADOWS Shadows 8 9 10 11 12 Eclipse Facts 1. Moon and sun have roughly the same angular size. 2. Lunar eclipses last about 1 h 45 min (total). 3. Moon’s umbral shadow on the Earth is no wider than 167 mi…Thus solar eclipses last no more than 7 min 30 sec. 4. Total eclipses occur every 18 yr 11 days. 5. On the average, a given location may witness a lunar eclipse nearly every year and a partial solar eclipse nearly every other year, but a total solar eclipse only about once every four centuries.
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6 31 Size of the earth Eratosthenes 240 B.C. Estimating the size of the Earth 32 The Motion of the Planets Around the Sun 33 Plato ~ 400 B.C. Motion of the planets in the sky Must be explained. Models must have these features: 1. Must be mathematical 2. Must explain observations 3. Must be based on the perfection of circles 4. Must obey Aristotelian Physics Ancient Astronomers 34 Aristotle Aristotelian Physics An object will not move unless some influence causes its motion. Conversely, the absence of such an influence would render an object motionless. 35 The consequence of the Aristotelian view is that the Earth can not be in motion because the influence producing such motion would be felt. His chemistry was just as bad… 36 Stellar Parallax Sought but not observed until 1838 7 37 Aristarchus Aristarchus: Relative Distances and Sizes of the Moon and the Sun ~ 220 B.C. 38 Ptolemy Ptolemy 150 A.D. 39 40 41 42 Retrograde Motion
