1. Cycles of the Sun Length of Days & Nights Seasons

2. Length of Days & Nights The Earth rotates on its axis A complete rotation takes a little over 24 hours (1 day) One side of the Earth is always facing the Sun

3. Length of Days & Nights The side of the Earth facing the Sun has day The side of the earth facing away from the Sun has night

5. As the Earth Rotates… The side of the Earth in the sunlight spins away and becomes night The side of the Earth in the dark spins toward the Sun and becomes day

7. Changing Length of Day & Day 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. Changing Length of Day & Day The hemisphere that is tilted toward the Sun gets more hours of daylight that the hemisphere tilted away from the Sun 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

10. Seasons The Earth is tilted on its axis

11. Seasons The tilt does not change – it always remains pointed in the same direction

13. 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

15. Seasons The hemisphere that is tilted toward the Sun has summer –Longer days (more hours of sunlight) –Warmer weather

16. Seasons The hemisphere that is tilted away from the Sun has winter –Shorter days (less hours of sunlight) –Cooler weather

17. Seasons When the Earth is positioned so that the tilt is neither towards nor away from the Sun, we have Spring and Fall –Moderate temperatures –Days and nights of similar length

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

21. Seasons: Fall (Northern Hemisphere) Position of the Earth is such that the northern hemisphere is tilted neither towards nor away from the Sun Autumnal Equinox (1 st day of fall) –About 12 hours of sunlight –About September 22

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

25. 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 (1 st day of spring) –About 12 hours of sunlight –About March 21

27. Energy from the Sun (Insolation)

29. 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

30. Watch this animation: Watch this animation: http://www.shsu.edu/%7Echm_tgc/sounds/fl ashfiles/earth.swf http://www.shsu.edu/%7Echm_tgc/sounds/fl ashfiles/earth.swf

31. Works Cited http://www.wrh.noaa.gov/hnx/newslet/spring03/dryjanuaries.htm http://www.nasa.gov/worldbook/wbkids/k_dayandnight.html http://www.lpi.usra.edu/education/skytellers/day_night/activities/cycle_o f_light.shtmlhttp://www.lpi.usra.edu/education/skytellers/day_night/activities/cycle_o f_light.shtml http://www.nps.gov/lacl/graphics/sun_earth2.jpg http://www.learner.org/jnorth/images/imageshtml/earth-tilt.gif http://costa-rica- guide.com/travel/index.php?option=com_content&task=view&id=365&It emid=604&limit=1&limitstart=4http://costa-rica- guide.com/travel/index.php?option=com_content&task=view&id=365&It emid=604&limit=1&limitstart=4 http://www.windows.ucar.edu/tour/link=/earth/climate/cli_seasons.html http://www.worldbook.com/features/seasons/assets/tilt4.gif http://www.springboardmagazine.com/SpringImages/seasons.gif http://www.nmm.ac.uk/upload/img/latitude.gif http://www.astro.virginia.edu/class/oconnell/astr121/im/hours-of- daylight-v-date.jpghttp://www.astro.virginia.edu/class/oconnell/astr121/im/hours-of- daylight-v-date.jpg http://en.wikipedia.org/wiki/Summer_Solstice