PH Earth Science The Earth-Moon System Planet Earth Earth is the third planet from the Sun. Earth rotates (spins) on its imaginary axis and revolves (circles) around the sun. Water occurs as a solid (ice), a liquid, or a gas (water vapor) Earth has one natural satellite , the moon.
The Earth-Moon System
- Satellite: Any object that revolves around another object
- Orbit: the curved path followed by a satellite (Earth is a satellite of the sun.)
Why do things orbit other things?
Animation of revolution and seasons
- most direct rays of the sun are focused at the equator
-Spring ~ March 21, Fall ~ September 21
Q: If ½ of the moon is always lit by the sun, why do we not always see it?
A: Because the lit side does not always face us!
click for animation
Phases of the Moon
New moonPhases of the moon
It is more important to know what causes the phases than it is to remember all the names!
August 11, 1999 Soissons, France
One of Jupiter’s moons causing a solar eclipse on Jupiter (notice the shadow).