1. Seasons

2. Seasons happen because of Earth’s tilt on its axis AND revolution around the Sun. Axis- imaginary line drawn from the north to the south pole. Rotation- the spinning of the earth on its axis. 1 rotation on its axis =24 hours

3. Revolution- the movement of the earth around the sun. Takes Earth 1 year to make one revolution. Orbit- the path the earth takes around the sun.

4. 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. When our part of Earth (Northern Hemisphere) is tilted TOWARD the sun, we are having summer. The NH is getting the Sun’s direct rays. In summer, days are long, nights are short. When our part of Earth (Northern Hemisphere) is tilted AWAY from the sun, we are having winter. The NH is getting LESS direct rays from the sun (weak). Days are short, nights are long. http://www.lpi.usra.edu/education/skytellers/seasons/about.shtml

6. Winter Solstice Winter Solstice- (December 21 or 22) The sun shines on the Tropic of Capricorn. The sun shines on the Tropic of Capricorn. The shortest day of the year will occur on Dec. 21 or 22. The shortest day of the year will occur on Dec. 21 or 22. After Dec. 21 or 22 the days will begin to get longer After Dec. 21 or 22 the days will begin to get longer

7. Vernal Equinox Vernal Equinox- (March 20-21) Sun shines directly on the equator. Sun shines directly on the equator. Equal hours of daylight and darkness. Equal hours of daylight and darkness.

8. Summer Solstice Summer Solstice- (June 20-21) Sun Shines directly on the Tropic of Cancer. Sun Shines directly on the Tropic of Cancer. Longest day of the year will be June 20 or 21. Longest day of the year will be June 20 or 21. After June 20/21 the days will begin getting shorter. After June 20/21 the days will begin getting shorter.

9. Autumnal Equinox Autumnal Equinox- (September 22 or 23) Sun shines directly on the Equator. Sun shines directly on the Equator. Equal hours of daylight and darkness. Equal hours of daylight and darkness.

10. Effect of different angles of sun: Summer solstice=rays are more concentrated Winter solstice = rays are less concentrated, spread out Summer solstice = hot weather on the way. Winter solstice = cooler weather.

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