Why does the Moon change?
Have you looked at the sky and seen the Moon? Have you noticed that the Moon changes shape, and that sometimes it can't be seen at all? We call the changing of the moon phases (pronounced "fay-ziz"), and each phase (pronounced "faze") has a name.
The Moon travels around the Earth
The Moon travels around the Earth in a circle called an orbit. It takes the moon almost 28 days to go one time around the Earth. (At the same time, both the Earth and the Moon travel around the Sun. It takes one year for the Earth to go all the way around the sun. But that is another story.)
The Sun always lights up (illuminates) half of the Moon (or the Earth, for that matter). But as the Moon orbits the Earth, we don't always see the half that's lit up. We only see the lighted half of the Moon when the Moon is full.
Here is a drawing of the Moon moving around the Earth.
The Moon's phases
Each shape that the Moon takes during its orbit (also called a Lunar Cycle - cycle means "once around") has a name. We have names for when the moon is getting brighter and getting darker. Here is a list of Moon words and their meanings:
|Full Moon||The Moon is at its brightest|
|Gibbous Moon||The Moon is less than full, but more than one quarter.|
|Quarter Moon||The Moon is showing half of full (half of one-half is one quarter).|
|Crescent Moon||The Moon is less than a Quarter Moon, and looks like a "C"|
|New Moon||The Moon is at its darkest. You can't see it at all!|
|Waxing Moon||The Moon is getting brighter.|
|Waning Moon||The Moon is getting darker.|
This page is intended for children to read themselves. Additional resources on the internet are listed below.
- Educators Guide to Moon Phases -- a very good page on an excellent science site with a hands-on moon phase project/experiment for your child to do.
- US Navy Astronomical Applications Department -- A great site with tons of astronomical information and explanations. This moon page has a really nice animation of the moon.
- Witchvox.com's moon page