1. Earth and Space Science
13.3 The Effects of Planetary Motion

2. Earth’s Rotation The Earth rotates (spins) on an axis.
It takes 24 hours to do one rotation around its axis.
This motion causes most stars, sun and moon to appear to rise in the east and set in the west.
The Earth’s axis is an imaginary line that connects the North Pole to the South Pole.

3. Earth’s Rotation

4. Revolution The planets revolve around the Sun in paths called orbits.
The orbits of most planets are nearly circular, with the Sun at the center of each orbit.
The period of time for one revolution around the sun is called one orbital period.

5. Earth’s Revolution
It takes Earth one year (365 days) to travel and revolve in a circle around the sun.
This allows us to see different stars and constellations during different seasons.
The angle of the Earth’s axis and the Earth’s Revolution causes the different seasons.

6. Earth’s Seasons Earth rotates at a tilt of 23.5.
During our summer months, the northern hemisphere is tilted toward the Sun.

7. The Earth’s Seasons

8. Seasons http://www.youtube.com/watch?v=WLRA87TKXLM&feature=related
Seasons Video

9. Homework
Read pg
Answer # 1 – 5 on pg. 405