1. SEASONSSEASONS Chapter 3

2. SEASONS on EARTH Earth’s orbit is elliptical with a 3% variation in Earth-Sun distance Is this the cause of the seasons?

3. EARTH’S ELLIPTICAL ORBIT Sun AphelionPerihelion A B C D

4. SEASONS on EARTH l Seasons arise on Earth because the spin axis of Earth is TILTED with respect to the ECLIPTIC (the apparent path of the Sun on the Celestial Sphere, or the plane of Earth’s orbit around the Sun) l Seasons DO NOT arise because of changes in Earth-Sun distances. (Earth is closest to Sun early in January)

5. SEASONS on EARTH l Seasons arise on Earth because the spin axis of Earth is TILTED with respect to the ECLIPTIC (the apparent path of the Sun on the Celestial Sphere, or the plane of Earth’s orbit around the Sun) l Seasons DO NOT arise because of changes in Earth-Sun distances. (Earth is closest to Sun early in January)

6. SEASONS on EARTH l Seasons arise on Earth because the spin axis of Earth is TILTED with respect to the ECLIPTIC (the apparent path of the Sun on the Celestial Sphere, or the plane of Earth’s orbit around the Sun) l Seasons DO NOT arise because of changes in Earth-Sun distances. (Earth is closest to Sun early in January)

7. VARIATION in the SUN’S RAYS

8. FLASHCARDFLASHCARD WHAT WOULD THE SEASONS BE LIKE ON EARTH IF THE EARTH’S AXIS WAS NOT TILTED WITH RESPECT TO THE ECLIPTIC? A) The seasons would be the same as they are now. B) The seasons would be switched. Fall would be spring and spring would be fall. C) There would be no seasons D) Earth’s axis HAS to be tilted so the question is silly.

9. SEASONS on EARTH l

10. Sun's motion defines the seasons

11. SEASONAL PATHS of the SUN

12. SUMMER SOLSTICE

13. WINTER SOLSTICE

14. FLASHCARDFLASHCARD WHERE DO YOU HAVE TO BE ON EARTH TO SEE THE SUN DIRECTLY OVERHEAD AT SOME TIME DURING THE YEAR? A) On the equator. B) At one of the poles. C) At one of the tropics. D) At any point between the tropics.

15. FLASHCARDFLASHCARD IF YOU ARE AT SOME POINT BETWEEN THE TROPICS, HOW MANY TIMES DURING THE YEAR WILL THE SUN BE OVERHEAD? A) Once. B) Twice. C) Three times. D) Four times.

16. FLASHCARDFLASHCARD FROM VANCOUVER (LATITUDE 49 DEGREES NORTH), AT NOON HOW MANY DEGREES ABOVE THE SOUTHERN HORIZON IS THE SUN ON THE WINTER SOLSTICE? A) 18 degrees. B) 23.5 degrees. C) 41 degrees. D) 49 degrees.

17. FLASHCARDFLASHCARD FROM VANCOUVER (49 DEGREES NORTH), HOW HIGH ABOVE THE HORIZON DOES THE SUN GET AT THE SUMMER SOLSTICE? A) 64 degrees. B) 49 degrees. C) 41 degrees. D) 23.5 degrees.

18. PLANETARY INCLINATIONS Planet Inclination Equator to Orbit Seasons? Mercury0 degreesNo Venus177.4 degreesYes retrograde Earth23.5 degreesYes Mars25.2 degreesYes (like Earth) Jupiter3 degreesYes Saturn27 degreesYes Uranus97.9 degreesYes (strange) Neptune29.6 degreesYes Pluto122 degreesYes retrograde

19. URANUS’ ORBIT