1. MOTIONS OF EARTH
CHAPTER 20

2. ROTATION Time for a planet to make one spin on it’s axis
Equal to planet’s DAY
Which way does Earth rotate?
How fast?

4. Solar day- 24 hours Sidereal Day- 23h 56m 4.09s Compared to the sun
Compared to distant stars
True rotation

7. REVOLUTION Time for planet to revolve around it’s star (orbit) YEAR
Earth= days
Perihelion= closest to sun
Jan. 3
Aphelion= farthest from sun
July 4

9. Kepler’s Law (#2) Law of equal areas
Speed of planet’s revolution varies based on distance from sun
When fastest (month)?

12. Precession Movement in the direction of Earth’s axis
Today; axis points towards Polaris
In 12,000 years; axis points toward Vega
Period= 26,000 years

13. Precession

14. GALAXY MOTION ROTATION 230 million years for Milky Way to rotate
150 miles/sec

15. Galaxy expansion

16. That’s a lot of motion! Rotation Revolution Precession Galaxy rotation
Galaxyexpansion
I’M DIZZY!

17. MOON MOTIONS Revolves around Earth
Revolution= 29.5 days (from Earth’s view)
(sideral= 27.3 days)

18. Moon Perigee- moon closest to earth (super moon)
Apogee- moon farthest from earth

20. Moon Calendar

21. Ooops!