Cycles of the Sun

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 (1st 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 (1st 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 (1st 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 (1st 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:http://www.shsu.edu/%7Echm_tgc/sounds/flashfiles/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_of_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&Itemid=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.jpg • http://en.wikipedia.org/wiki/Summer_Solstice