Earth Science- Chapter 22

Front 1

Astronomy

Back 1

the science that studies the universe

Front 2

Geocentric

Back 2

model that the Greeks believed in. they thought the Earth stayed motionless at the center of the universe and the sun, moon and planets revolved around it.

Front 3

Heliocentric

Back 3

in this model, Earth and other planets revolve around the sun.

Front 4

Retrograde motion

Back 4

planets move usually move eastward among the stars. but every so often, they stop and reverse direction, then go back to moving eastward.

Front 5

Ellipse

Back 5

orbit in an oval shape

Front 6

Astronomical unit (AU)

Back 6

average distance between Earth and the sun (about 150 million kilometers)

Front 7

Rotation

Back 7

spinning of a body on its axis

Front 8

Revolution

Back 8

motion of a body along a path around a point in space (ex: Earth revolves around the sun)

Front 9

Precession

Back 9

very slow, slight movement of Earth's axis over 26,000 years

Front 10

Perihelion

Back 10

when the Earth is closest to the sun during its revolution (occurs about January 3 each year)

Front 11

Aphelion

Back 11

when the Earth is farthest from the sun during its revolution (occurs about July 4 each year)

Front 12

Perigee

Back 12

when the moon is closest to Earth during its revolution

Front 13

Apogee

Back 13

when the moon is farthest from Earth during its revolution

Front 14

Phases of the moon

Back 14

monthly change in the amount of the moon that appears lit

Front 15

Solar eclipse

Back 15

when the moon moves in a line directly between Earth and the sun and casts a dark shadow on Earth

Front 16

Lunar eclipse

Back 16

when the moon moves within Earth's shadow

Front 17

Crater

Back 17

round depressions in the surface of the moon. made by impact of moving debris.

Front 18

Ray

Back 18

bright streaks that radiate from a crater on the moon

Front 19

Mare

Back 19

smooth areas of the moon that used to be seas.

Front 20

Rille

Back 20

channel like valleys or trenches on the moon. may be from ancient lava flows

Front 21

Lunar regolith

Back 21

soil-like layer on the moon, made of igneous rocks, glass beads and fine lunar dust. (over 3 meters thick)