1. Insolation Insolation = Incoming Solar Radiation Insolation In = Heat Out

2. Factors 1.Angle of insolation - direct (high angle) or indirect (low angle). Latitude has greatest effect on angle. 1.Type of Surface: light or dark, rough or smooth 2.Length of Daylight: longer days in summer

3. Angle of Insolation

6. Seasons Earth’s axis tilts 23.5 0 Seasons result from this tilt. Distance to the Sun DOES NOT MATTER! In fact, Earth is closest to the Sun in our winter.

8. Seasons

9. Equinox Equinox = when the sun is directly over the equator. Day and night are equal = 12 hours long Sun rises due East, sets due West Vernal (spring) Equinox = March 20 Autumnal (fall) Equinox = Sept. 22

10. Solstice Solstice = sun stop Summer Solstice ( 6/21) = Sun is directly over 23.5 0 N (Tropic of Cancer) = most daylight Winter Solstice (12/21) = Sun is directly over 23.5 0 S (Tropic of Capricorn) = least daylight

12. Rotation Daily Motion = stars and planets rise in the East and set in the West. Why? Earth rotates counterclockwise at 15 o / hr. Evidence: - Foucault’s Pendulum - Coriolis Effect – all winds move rightward in the northern hemisphere

14. Length of Day How long is a day? Is it 24 hours or 23 hrs. 56 minutes? Sidereal Day = actual time it takes to rotate 360 0 (23h 56m). But, earth revolves around sun 1 0 in a day. So, it takes an additional 4 minutes to complete turn. Solar Day = Noon to Noon = Time it takes to rotate 361 0 (24h).

16. Revolution Earth revolves around Sun 1 o / day. Also counterclockwise. Evidence: Seasons. Constellations change during year.