1. Seasons What do your students think causes the seasons? http://nix.ksc.nasa.gov/info By the Lunar and Planetary Institute For use in teacher workshops

2. True color images June December March September http://www.nasa.gov/vision/earth/features/blue_marble.html

3. What Causes Earth’s Seasons? Earth’s axis is tilted 23.5 degrees – it always points in the same direction (Polaris, the North Star) as we orbit our Sun once a year This tilt causes the hemispheres to alternate in the amount of our Sun’s light and heat they receive through the year http://www.lpi.usra.edu/education/skytellers/seasons/about.shtml

4. More daylight hours, more direct sunlight Northern Hemisphere Summer http://www.lpi.usra.edu/education/skytellers/seasons/about.shtml

5. Earth’s orbit is almost a perfect circle Earth is CLOSEST to our Sun (91 million miles) in winter—January 3 Earth is farthest from on our Sun (94 million miles) in summer –July 4

6. Height of Sun for USA Winter: The Sun rises in the southeast, stays low in the sky, and sets in the southwest. Spring: The Sun rises due east, moves higher in the sky than in winter, and sets due west. Summer: The Sun rises in the northeast, travels high (near zenith), and sets in the northwest. Fall: The Sun rises due east, travels to a medium-height in the sky, and sets due west.

7. Daylight Hours Across the Globe Time is indicated as number of hours (h) Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec 10.5 h 11 h 12 h 12.5 h 13 h 14 h 14.5 h 14 h 12.5 h 12.5 h 11 h 11.5 h 14.5 h 13.5 h 13.5 h 12.5 h 11 h 11 h 11 h 11.5 h 11.5 h 12.5 h 14 h 14.5 h 12 h 12 h 12 h 12 h 12 h 12 h 17.5 h 15.5 h 13.5 h 11.5 h 10 h 8.5 h 8.5 h 9.5 h 11.5 h 13 h 15 h 16.5 h 5 h 7 h 10 h 13.5 h 17.5 h 21.5 h 22 h 18 h 15.5 h 11.5 h 8.5 h 5.5 h 12 h 12 h 12 h 12 h 13 h 13 h 12 h 12 h 12 h 12 h 12 h 12 h 15 h 14 h 13.5 h 12.5 h 11.5 h 10 h 10.5 h 11 h 11.5 h 12.5 h 14 h 14 h 9 h 10 h 11 h 13.5 h 15 h 17 h 16.5 h 15.5 h 13.5 h 11.5 h 10.5 h 9.5 h 24 h 24 h 19 h 14.5 h 0 h 0 h 0 h 0 h 7 h 15 h 24 h 24 h Miami Brisbane Nairobi Punta Arenas Nome Singapore Cape Town Seattle Vostok http://www.lpi.usra.edu/education/skytellers/seasons/activities/light.shtml

8. Seasons on Other Planets In some cases, the changing distances from the Sun will affect the seasons. In others, the axial tilt will make a huge difference!

9. Seasons on Planets Planet Axial Tilt Eccent. OrbitPerihelion Aphelion Mercury 0° 0.21 88 days 28 mill. Miles 43 mill. miles Venus 177° 0.01 224 days Earth23° 0.02 365 days 91 mill. miles 94 mill. miles Mars 25° 0.09 686 days 129 mill. miles 155 mill. miles Jupiter 3° 0.05 12 years Saturn 27° 0.06 30 years Uranus 98° 0.05 84 years Neptune 30° 0.01 165 years

10. Mars’ Orbit and Seasons At summer solstice, Mars is 153 million miles from the Sun At autumnal equinox, Mars is 134 million miles from the Sun At winter solstice, Mars is 128 million miles from the Sun At vernal equinox, Mars is 145 million miles from the Sun Original images from http://photojournal.jpl.nasa.gov/index.html