November 9, 2010
Want to stay on top of all the space news? Follow @universetoday on Twitter The celestial sphere is an imaginary sphere that surrounds the Earth and acts like the Earth, but has an arbitrarily large radius. It has the same center, axis, and rotation as the Earth. It is used in astronomy and navigation. Conceptually, [...]
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December 7, 2009
A celestial globe is a physical model of what was called by ancient astronomers the celestial sphere. These astronomers Ptolemy among them thought that the universe only included the sun, moon, earth, and the stars visible in the night sky. For this reason the assumed that the universe was a sphere with the Earth as [...]
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