January 25, 2008

January 25, 2008 - Apparent motion of sun o Picture o Only...

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January 25, 2008 What is precession? o The gradual change of the earth’s axis in space Why do stars rise and set? o Earth rotates west to east so stars appear to circle from east to west Proof of earth spinning o Newton’s first law Objects in motion tend to stay in motion o Pendulum swinging wants to stay swinging in the same direction Even if the earth moves underneath it o See window at the base of Gamow tower More proof of the earth spinning o Messenger spacecraft took pictures of it What the sun? What causes the sun to rise and set? o Same as the stars, earth spinning o Everything that happens on a daily basis is because of earth’s rotation
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Unformatted text preview: Apparent motion of sun o Picture o Only at equinox does the sun rise exactly in the east and exactly in the west Visibility of stars o Pictures o Polar stars that are circumpolar never set or rise (in the north and south) depending on your latitude Circumpolar motions o Circumpolar stars: Stars that never set Move counter clockwise around north celestial pole Our view from boulder (on earth) o Stars near the north celestial pole are circumpolar and never set o We cannot see stars near the south celestial pole o All other stars (and sun, moon, planets) rise in the east and set in the west...
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