B. autumnal equinox. D. meridian crossing. Aristotle and Ptolemy held that the center of the universe is A. Earth. D. the Sun. During the year, the Sun appears to move alternately northward and southward on the celestial sphere.
Retrograde motion is A. the changing of the Earth's speed as the Earth moves around the Sun.
B. changing of the apparent speed of the Sun across the sky during the year. D. motion of a planet as it approaches the north celestial sphere. D. cool star. The constellations of the zodiac all lie A. along the meridian. B. near the zenith.