If we look at the sky on a fine night—preferably from a ship at sea or a place deep in the countryside, not from among the bright lights of a town—we seem to see the inside of a dark bowl, studded with points of light. You and I, living in the twentieth century A.D., know that this is an illusion. There is no bowl, and the stars are at different distances from us: some a few light-years away, others many hundreds. But the illusion is strong: Chinese, Greek, Arab, and medieval European astronomers all treated the stars as lying on a sphere around the earth.
KeywordsFull Moon Winter Solstice Celestial Pole Synodic Period Celestial Equator
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