Physics Zone Lesson: Phases of the Moon
| SUN |
This animation shows the moon in orbit around the barycenter (red dot) of the Earth-Moon system as the Earth rotates on its axis. If the Sun is located off the top of the page, notice how the top half of the moon is always illuminated. However, as the Moon orbits the Earth, notice that the illuminated side of the moon can not always be seen from the Earth. Usually we only see a portion of it. We describe the changing view of the Moon from Earth as the phases of the Moon. The complete cycle takes 29.5 days. The sliding scale in the upper corner of the animation shows the phase we would see when the moon is where it is shown in the animation. (use the play and pause buttons on the animation above)
The diagram below shows the same as the animation above, but is easier to take notes on.
|
1  New
Moon |
2  New
Crescent waxing |
3 
First Quarter waxing |
4  New
Gibbous waxing |
5  Full
Moon |
6  Old
Gibbous waning |
7 
Last Quarter waning |
8  Old
Crescent waning |
Lunar
face as viewed from Earth Waxing is just a term used to describe that the Moon's "face" is increasing or growing, where waning means its face is decreasing.
See the current phase of the moon.
