Why do we have seasons?

1. https://www.youtube.com/watch?v=b25g4nZTHvM Why do we have seasons? http://www.youtube.com/watch?v=HlvQ1fVMqNA

2. What Causes the Seasons? http://www.youtube.com/watch?v=q4_-R1vnJyw • The earth’s orbit – revolution around the Sun- - is inclined 23.5 degrees from the horizontal plain, is the cause for the change in seasons https://www.youtube.com/watch?v=l64YwNl1wr0

3. Earth’s rotation • The Earth rotates on its axis (imaginary vertical line around which Earth spins) every 23 hours & 54 minutes. • Varying amounts of sunlight create seasons • The Earth’s AXIS is the most important reason we have seasons http://www.youtube.com/watch?v=lkWyM-M8o0c

4. Earth’s revolution • It takes the Earth 365 days (or rotations) to travel or revolve around the Sun once. • This is called a year. The Earth ROTATES daily The Earth REVOLVES around the Sun

5. Earth’s Orbit • The Earth’s orbit around the sun is NOT a perfect circle. • It is an ellipse. • Seasons are not caused by how close the Earth is to the sun. • The Earth is closest to the sun around January 3 and farthest away from the sun around July 4. Ellipse

6. Why is it colder in winter, and warmer in summer? Summer – • Rays hit Earth at a steep angle • Earth leans toward the Sun in summer • Hemisphere tilted toward the Sun Winter • Rays hit at a shallow angle • Rays are more spread out minimizing energy to Earth • Less daylight and longer nights https://www.youtube.com/watch?v=Pgq0LThW7QA&feature=share

7. Solstices • Solstices occur twice a year, when the tilt of the Earth's axis is oriented directly towards or away from the Sun, causing the Sun to appear to reach its northernmost and southernmost extremes. • Winter solstice is the shortest day of the year- December 21st • The Summer Solstice is the longest day of the year - June 21 https://www.youtube.com/watch?v=FmCJqykN2J0

8. Equinoxes • A day lasts 12 hours and a night lasts 12 hours at all latitudes. • Equinox literally means "equal night". • Sunlight strikes the earth most directly at the equator. • This occurs twice a year. • Spring (vernal)– March 21 • Fall (autumnal) – September21

9. Summer is warmer than winter (in each hemisphere) because the Sun's rays hit the Earth at a more direct angle during summer than during winter

10. Winter – Indirect sunlight Summer – Direct sunlight

11. Seasons…in a nut shell

12. ReviewLook closely at where the Sun is hitting the Earth during each season: FALL WINTER SUMMER SPRING http://www.youtube.com/watch?v=knK87GoNyGo

17. Finish notes paper https://www.youtube.com/watch?v=82p-DYgGFjI