Axis An invisible line that goes through the center of a thing, like the Earth, which spins around this line.

Equator An imaginary line around the middle of the Earth, dividing it into the Northern Hemisphere and the Southern Hemisphere.

Full Moon The phase in which the whole face of the moon is lit up and looks like a complete circle in the night sky.

Gravity The force of attraction between masses

Hemisphere  Half of the Earth, either the northern or the southern part (for this lesson). 

Lunar Eclipse  What occurs when Earth comes between the sun and the moon, casting a shadow on the moon.

New Moon The phase in which the moon is invisible, because its dark side is facing Earth.

Revolution The movement of a planet (such as Earth) or moon around another object (such as the sun) in space.

Rotation When an object spins around an imaginary line, such as Earth spinning around its axis.

Seasons Different times of the year with distinct weather patterns, caused by Earth’s tilt as it revolves around the sun.

Solar Eclipse When the moon comes between the sun and the Earth, casting a small shadow on the Earth.

Tide The water level in the ocean at any given time. High tides are at their highest, and low tides are at their lowest, when there is a full moon.