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21 Cards in this Set
- Front
- Back
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astronomy
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the science that studies the universe. This deals with the properties of objects in space and the laws under which the universe operates
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geocentric
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describes the concept of an Earth-centered universe. The greeks believed that Earth was a sphere that stayed motionless at the center of the universe.
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heliocentric
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describes the concept of an Earth-centered universe. The Greeks believed that Earth was a sphere that stayed motionless at the center of the universe.
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retrograde motion
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the apparent westward motion of the planets with respect to the stars
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astronomical unit
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the average distance from Earth to the sun; 1.5x10^8, or 150 million Kilometers.
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ellipse
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An oval-shaped path that Kepler discovered who had a good mathematical mind
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rotation
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the turning, or spinning of a body on its axis. This is one of the two main motions of Earth. The main result from this is day and night.
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revolution
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the motion of a body, such as a planet or moon, along a path around some point in space. For example, Earth revolves around the sun, and the moon revolves around Earth.
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precession
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the slight movement, over a period of 26,000 years of Earth's axis. This is the third and very slow movement of Earth.
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perihelion
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Earth is closet to the sun, about 147 million kilometers away. This occurs about January 3 each year.
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aphelion
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Earth is farthest from the sun, about 152 million kilometers away. This occurs about July 4.
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perigee
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when the moon is closest to Earth or an artificial satelite
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apogee
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when the moon is farthest from Earth. The motions of the Earth-moon system constantly change the relative positions of the sun, Earth, and moon.
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phases of the moon
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a change in the amount of the moon that appears lit. The cycle soon begins again with the reappearance of the crescent moon.
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solar eclipse
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an eclipse of the sun. This occurs when the moon moves in a line directly between Earth and the sun, casting a shadow on Earth.
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lunar eclipse
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an eclipse of the moon. This occurs when the moon passes through earth's shadow.
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crater
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the most obvious features of the lunar surface. They are round depressions in the surface of the moon. Most were produced by the impact of rapidly moving debris.
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ray
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splash marks that radiate outward for hundreds of kilometers.
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mare
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the dark, relatively smooth area on the moon's surface. This is visible and one thought the be seas.
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rille
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long channels that look somewhat similar to valleys or trenches. They are associated with lunar maria.
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lunar regolith
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soil-like layer that is composed of igneous rocks, glass beads, and fine lunar dust.
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