1. Earth, Moon, Sun System
Chapter 19

2. Revolution Vs. Rotation
Earth rotates (spins) on its axis. One rotation per 24 hours
This is day and night.
Earth revolves around the Sun. One revolution happens every 365 1/4 days.
This one year.

3. Revolution vs. Rotation contd.
Moon revolves around Earth in 27.3 days.
Since it also takes about 27 days for the moon to rotate on its axis, we only see one side of the moon.

4. The Moon brain check
How much of the moon is always lit by the sun, even though we can’t always see it?

5. Where did the Moon come from?
Theory: The moon was once a part of Earth. A large object, pulled by Earth’s gravity, knocked it off. It began to orbit the Earth.
The moon is about 1/3 to 1/4 the diameter of the Earth.

6. Moon’s phases phases are caused by the revolution of the moon.
phase we see depends on how much of the lit part we see.
Moon takes days to revolve around Earth. That is how many days it takes to cycle through the phases.

7. Moon’s phases

8. Eclipses
lunar eclipse -when Earth is between the moon and sun. During a full moon.
solar eclipse-when the moon gets between the Earth and the sun. (During a new moon)
Demo.

9. Eclipses
A total eclipse happens when the moon or Earth blocks all of the light from the sun.
Umbra- darkest part of the shadow.
Penumbra-largest part of shadow.

10. Why don’t we have an eclipse every month?

11. Tides Tides caused by gravity of Moon and Sun
Spring tide happens at full and new moon. Earth, Moon, Sun lined up-higher highs and lower low tides
Neap tide happens at first and third quarter-Earth, Moon, Sun at right angles: tidal range is lower

12. Spring Tide and Neap Tide