Vocabulary Chapter 22

Astronomy

• The scientific study of the universe

Geocentric

• Describes the concept of an Earth centered universe

Heliocentric

• Describes the view that the sun is at the center of the solar system

Retrograde Motion

• the apparent westward motion of the plants with respect to the stars

Ellipse

Rotation

• The spinning of a body, such as Earth, about its axis

Revolution

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

Precession

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

Perihelion

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

Aphelion

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

Perigee

• The point at which the moon is closest to Earth

Apogee

• The point where the moon is farthest from Earth