1. Welcome back! Grab a handout Review revolution, check calculations
Discuss Earth’s 3rd Motion
By the end of the hour you should be able to accurately describe the 3 distinct motions of the earth and identify their periods

2. Earth’s 3rd Motion Precession The wobbling of the Earth’s Axis
As a result of the wobble what will change?
Period is about 26,000 years.
In 26,000 years what will be the North Star?

4. https://en.wikipedia.org/wiki/Axial_precession

7. So why does the Earth precess?
Tidal forces from the moon and sun (and Jupiter to a small degree)
Basically the ocean water rubbing against the ocean basins due to tides, creates friction and the friction slows the Earth’s rotation down.

10. Assignment
Earth’s Motion book Questions (1-11)