1. What do you already know? The sun has the following effects on earth:
Heats the earth’s surface & atmosphere
Influences winds & water cycle.
Lights half of the earth’s surface at a time.

2. ROTATION
The spinning of Earth on its axis that causes day and night to occur

3. AXIS
The imaginary line extending from the North Pole to the South Pole going through the center of Earth, which is the center of
Earth’s rotation

4. ROTATION 24 HOURS
One complete spin/rotation takes 24 hrs

5. North Pole always faces Polaris, the North Star

6. 23.5 DEGREES
The slant of Earth’s axis, which is 23.5° from vertical

7. NUMBER OF HOURS OF DAYLIGHT Depends on location on Earth
The number of hours of daylight received each day depends on the latitude.
The equator receives about 12 hours of daylight all year long

8. DAYLIGHT HOURS

9. The earth’s tilt on its axis remains constant throughout the year.

10. Seasons
As the Earth revolves around the Sun, the tilt sometimes points toward the Sun, sometimes away from the Sun, and sometimes neither away nor toward the Sun

11. Seasons: Summer (Northern Hemisphere
Position of the Earth is such that the northern hemisphere is tilted toward the Sun
Summer Solstice (1st day of summer)
Sun at highest point (over Tropic of Cancer)
Most hours of sunlight (longest day)
About June 21

13. Seasons: Winter (Northern Hemisphere)
Position of the Earth is such that the northern hemisphere is tilted away from the Sun
Winter Solstice (1st day of winter)
Sun at lowest point (over Tropic of Capricorn)
Fewest hours of sunlight (shortest day)
About December 21

15. Seasons: Spring (Northern Hemisphere)
Position of the Earth is such that the northern hemisphere is tilted neither towards nor away from the Sun
Vernal Equinox (1st day of spring)
About 12 hours of sunlight
About March 21

19. Summing Up:
Winter - Earth tilted away from Sun, fewer hours of sunlight, less direct sunlight (insolation)
Spring – Earth neither tilted away nor toward the Sun, equal hours of daylight and night
Summer – Earth tilted toward the Sun, more hours of daylight, more direct sunlight (insolation)
Fall - Spring – Earth neither tilted away nor toward the Sun, equal hours of daylight and night

20. Watch this animation: http://www. shsu