Column 1
an attractive force that exists between all objects that have mass.
gravity
the imaginary line that divides Earth into the Northern and Southern Hemispheres
equator
the large, dark, flat areas on the Moon.
maria
the lit part of the Moon or a planet that can be seen from Earth.
phase
the path an object follows as it moves around another object.
Orbit
the spin of an object around its axis.
rotation
when Earth's rotation axis is tilted neither toward nor away from the Sun.
equinox
when Earth's rotation axis is tilted directly toward or away from the Sun.
solstice
phases of the Moon during which more of the Moon’s near side is lit each night.
waxing phase
the orbit of one object around another object.
revolution
the line around which an object rotates
rotation axis
an occurrence during which the Moon's shadow appears on Earth's surface.
solar eclipse
an occurrence during which the Moon moves into Earth's shadow.
lunar eclipse
phases of the Moon during which less of the Moon’s near side is lit each night.
waning phase
the central, darker part of a shadow where light is totally blocked.
umbra
the amount of energy that passes through a square meter of space in one second
intensity
the periodic rise and fall of the ocean’s surface caused by the gravitational force between Earth and the Moon, and Earth and the Sun.
ocean tide
the periodic rise and fall of the ocean’s surface caused by the gravitational force between Earth and the Moon, and Earth and the Sun.
daily tide
when the ocean's surface reaches its highest point.
high tide
the lighter part of a shadow where light is partially blocked.
penumbra
when the ocean's surface reaches its lowest point.
low tide
the difference in water height between a high tide and a low tide.
tidal range
the largest tidal range that occurs when the Sun, Earth, and the Moon form a straight line.
spring tide
the lowest tidal range that occurs when the Sun, Earth, and the Moon form a right angle.
neap tide