Lecture 4

Lecture 4 - accounted for retrograde motion-Wrote first...

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10/6/09 Geocentric model – earth-centered universe Heliocentric model – sun-centered universe (Modern view: there is no center of universe) Two Reasons Greeks thought Earth was round… 1) Bow of the ship in ocean 2) Lunar eclipse – Earth’s shadow is round Aristotle – 350 BC - “Heavenly Spheres” 1) Earth a. Earth b. Water c. Air d. Fire 2) Planets a. Moon b. Mercury c. Venus d. Sun e. Mars f. Jupiter g. Saturn 3) Outer Spheres a. Fixed Stars b. “Primum mobile” – prime mover to move other spheres every 24 hours c. Crystalline – explained precession 49,000 d. Heaven – “Empryean” Retrograde motion – planets’ short period of westward motion in the sky Ptolemy – tweaked Aristotle’s model, produced first complete model of the universe, added epicycles - Epicycles – smaller loops attached to heavenly spheres
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Unformatted text preview: accounted for retrograde motion-Wrote first text on astronomy “The Amalgamest”-His model stood for almost 1,500 years Copernicus – (1500 AD) first to put forth heliocentric model (based on logic instead of arguments)-Wrote “On the Revolutions of the Heavenly Spheres” OR “The Revolution” 1) 2) Stars are very far away from the Sun with respect to the planets 3) Daily motion of stars/sun could be Earth’s rotation about its axis every 24 hours 4) Explained sun’s path through zodiac by Earth’s yearly orbit about the Sun 5) Retrograde motion explained by planets’ differing orbital distances and speeds to the sun...
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