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the scientific study of the universe; it includes the observation and interpretation of celestial bodies and phenomena


describes the concept of an Earth-centered universe


describes the view that the sun is at the center of the solar system

retrograde motion

the apparent westward motion of the planets with respect to the stars


an oval

astronomical unit (AU)

average distane from Earth to the sun; 1.5 X 10 to the 8th power, or 150 million kilometers


the spinning of a body, such as Earth, about its axis.


the motion of one body about another, as Earth about the sun


a slow motion of Earth's axis that traces out a cone over a period of 26,000 years


the point in the orbit of a planet where it is closest to the sun.


the place in the orbit of a planet where the planet is farthest from the sun


point of moon's orbit when it is nearest the earth


the point farthest from the earth

phases of the moon

the progression of changes in the moons appearance during the month.

solar eclipse

an eclipse of the sun; a solar eclipse occurs when the moon moves in a line directly between Earth and the sun, casting a shadow on Earth.

lunar eclipse

an eclipse of the moon: a lunar eclipse occurs when the moon passes through Earth's shadow


the depression at the summit of a volcano or that which is produced by a meterite impact


any of a system of bright elongated streaks, sometimes associated with a crater on the moon


(plural maria) the latin name for the smooth areas of the moon formerly thought to be seas


long channel associated with lunar maria; A rille looks similar to a valley or trench

lunar regolith

a thin, gray layer on the surface of the moon, consisting a loosley compacted material beluieved to have been formed by repeated impacts of meteorites

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