Earth-Moon system #1

This movie highlights the dynamic of the Earth - Moon system. You can use it to illustrate the moon phases (~28 days) and its synchronous orbit.
Note that the side of the Moon facing the Earth is always the same one. We say that its orbit is synchronous.
Note that everything is not to scale in this animation. See the animation “Eclipses” to observe those phenomena.

Click on {pause} to stop the movie and show the Moon the way we see it from the Earth.

• To illustrate the synchronous orbit of the moon and to explain why we always see the same side.
• To understand the cycle of the moon’s phases.
• To illustrate the Earth / Moon system dynamic. 
• To distinguish between revolution and rotation.

The moon’s orbit is tilted 5° relative to the Earth-Sun orbital plane (the ecliptic) which it intersects at  2 points called « nodes ». Our satellite can pass above or below the plane of the ecliptic, which explains why a sun or moon eclipse does not occur every month. Since the moon takes as long to revolve around itself as it does to complete its orbit around the Earth, it always presents the same face to us. These two motions are synchronized by the tidal forces exerted by the Earth. The same forces make the Earth’s rotation slow down and are causing the moon to move away from us very slowly.
For a few days before and after a new moon we can see « Earthshine » when the dark part of the moon appears to be dimly lit by the Earth.