Advertisement Upgrade to remove ads

Rotation

The spinning of a body around its own axis

Revolution

The movement of one body around another in an orbit

ecliptic

The imaginary plane formed by the earth's orbit around the sun of the plane formed by the apparent motion of the sun through the sky

phases

The visible changes that the moon goes through in every lunar month, caused by the changing angle of illumination from the sun. New, crescent,quarter, gibbous and full.

waxing moon

The period in the moon's monthly cycle after the new moon and before the full moon. During this period, the lighted portion of the moon's surface is increasing.

waning moon

The period in the moon's monthly cycle after the new moon and before the full moon. During this period the lighted portion of the moon's surface is decreasing.

synodic month

The moon completes its entire cycle of phases (new moon to new moon) in a 29 1/2 day month.

sidereal month

The moon completes one revolution around the earth in a 27 1/3 day month.

perigee

The point in the moon's orbit when it is closest to the earth.

apogee

The point in the moon's orbit when it is farthest from the earth.

umbra

The darker cone-shaped core of a shadow, surrounded by a lighter penumbral shadow.

penumbra

The lighter part of a shadow.

lunar eclipse

An eclipse creased by the earth coming between the sun and the moon, Lunar eclipses always happen during the full moon phase. The moon passes into earth's umbra.

solar eclipse

An eclipse caused when the moon comes directly between the earth and the sun, temporarily blocking our sun's disk in the sky. Always happens during the new moon phase. Moon's umbra reaches earth's surface.

annular eclipse

Ring eclipse. A solar eclipse when the moon is at apogee. The apparent diameter of the moon is not large enough to completely obscure the sun, so a ring of light is left uncovered around the dark circle produced by the moon.

tides

The cyclical movement of bodies of water on earth caused by the gravitational pull of the earth, moon and sun.

spring tide

The highest tides in a lunar month, occurring near new and full moon phases, when the earth, sun and moon are aligned.

neap tide

The lowest high tide of the lunar month, occurring near the first and last quarter moon phases.

Please allow access to your computer’s microphone to use Voice Recording.

Having trouble? Click here for help.

We can’t access your microphone!

Click the icon above to update your browser permissions above and try again

Example:

Reload the page to try again!

Reload

Press Cmd-0 to reset your zoom

Press Ctrl-0 to reset your zoom

It looks like your browser might be zoomed in or out. Your browser needs to be zoomed to a normal size to record audio.

Please upgrade Flash or install Chrome
to use Voice Recording.

For more help, see our troubleshooting page.

Your microphone is muted

For help fixing this issue, see this FAQ.

Star this term

You can study starred terms together

NEW! Voice Recording

Create Set