1. Ch 9 Earth in Space Reason for our Seasons

2. Earth’s Rotation : spin on its axis! Axis is an imaginary line running from N to S pole. The axis is tilted 23.5 deg As the Earth moves around the Sun, the axis always stays pointing in the same direction. Earth rotates a little more than every 24 hours. Rotation causes day and night Sun appears to Rise in the East and Set in the West The Earth rotates counter clockwise.

3. The # of hrs of daylight received each day depends on the latitude. The # of hrs of daylight received each day depends on the latitude. The equator receives about 12 hrs of daylight all year long The equator receives about 12 hrs of daylight all year long The hemisphere that is tilted toward the Sun gets more hours of daylight than the hemisphere tilted away from the Sun  warmer temperatures The hemisphere that is tilted toward the Sun gets more hours of daylight than the hemisphere tilted away from the Sun  warmer temperatures Latitudes closest to the equator have less change in hours of daylight Latitudes closest to the equator have less change in hours of daylight Latitudes further from the equator have more dramatic changes in hours of daylight Latitudes further from the equator have more dramatic changes in hours of daylight

5. “Rotation” Drawing Box

6. Revolution: Earth moves around the sun One revolution takes 365 ¼ days or one year Earth’s tilt & position causes seasons Oval: shape of the Earth’s path, orbit around the Sun.

7. Revolution (drawing box)

8. The Earth during one full year as you would see it if you looked straight at it from the Sun.

9. Use for “Season” drawing box Positions of Earth around the Sun throughout the year Drawing Box

10. Season are different for everyone on the planet. We don’t experience the same thing at the same time.

11. First day of Spring Vernal Equinox ~ March 21 st (equal day and night) The length of day equals the length of night worldwide http://www.mrdowling.com/images/601seasons.jpg

12. First day of Summer Summer Solstice ~ June 21 st Northern Hemisphere Longer days than nights http://www.mrdowling.com/images/601seasons.jpg

13. First day of Autumn Autumnal Equinox ~ Sept 22 nd (equal day and night) The length of day equals the length of night worldwide. http://www.mrdowling.com/images/601seasons.jpg

14. First day of Winter Winter Solstice ~ Dec 21 st or 22 nd Northern Hemisphere Days shorter than night. http://www.mrdowling.com/images/601seasons.jpg

15. In summary… http://www.shsu.edu/%7Echm_tgc/sounds/flashfiles/earth.swf

16. REVIEW: What is the difference between rotation and revolution? What causes our seasons? http://www.shsu.edu/%7Echm_tgc/sounds/flashfiles/earth.swf