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waltz_of_planets ch 2

waltz_of_planets ch 2 - Gravitation and the Waltz of the...

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1 Gravitation and the Waltz of the Planets From Ancient to modern astronomy Geocentric view Heliocentric view Kepler’s laws of planetary motion Gravity • Newton’s laws of motion Columbia Launch: October 18,1993 Columbia’s crew: STS 93 The Greeks tried to EXPLAIN and UNDERSTAND, not just PREDICT . To them, the universe was the basically solar system -the Sun, Earth, Moon and 5 planets known at that time. They observed that: - over the course of a night, the stars slid smoothly across the sky. - over the course of a month, the moon moved smoothly in the sky relative to the stars. - over a course of a year, the Sun progressed along the ecliptic. - 5 other bodies known to them were Mercury, Venus, Mars, Jupiter and Saturn. Planetes- “ wanderer ”----> do not behave in as regular and predictable manner. They seem to speed up and slow down and appear to loop back and forth relative to stars. Sometimes they stop. Sometimes their brightness change. Prograde Prograde motion: Eastward (forward or direct) Retrograde Retrograde motion: Westward (backward) The Geocentric View (Greek Astronomy) The Path of Mars (2009-2010) He gave PROOFS that the Earth was SPHERICAL: objects all fell towards its center perpendicular to ground sphere. noted shadows cast on moon during eclipse were always round. Earth - at the CENTER of Universe - is heaviest thing around therefore it shouldn't move. The Sun and the Moon revolve with uniform motion around a circle with Earth at its center. This simple model could not account for the variation in planetary brightness and their retrograde motion. . Each planet was taken to move uniformly around a small circle, called an epicycle , whose center moved uniformly around Earth on a second and larger circle, known as the deferent . Greek philosopher Aristotle - (384-322 B.C.) :
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2 He worked in Alexandria a city in Egypt , from 127--151 A.D. As a geographer, he is the first known to have used latitude and longitude on earth. His astronomy book, ( mu epsilon gamma iota sigma tau nu ) -- megiste— or “The Greatest” is usually known by its Arabic name Almagest .
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