1. Agenda Seasons Calendars Read unit 8 for Thursday

2. Why do we have seasons? A. Earth’s distance from the Sun varies B. The tilt of Earth’s axis C. None of the above

3. Closest (perihelion) 91,000,000 miles Furthest (aphelion) 95,000,000 miles Jan 3 Jul 7 Variation of our distance to the Sun

4. Would you rather drive 717 miles?

5. Or 688 miles? At 75 mph, this trip would be 23 minutes shorter

6. Closest (perihelion) 91,000,000 miles Furthest (aphelion) 95,000,000 miles Variation of our distance to the Sun This variation in distance is really tiny!

7. When is Earth closest to the Sun (perihelion)? A. June 21 B. January 3 C. July 4 D. August 15 E. March 26 Farthest from Sun (aphelion)

8. What does Earth’s rotation axis do as we orbit the Sun? A. Always points outward B. Always points inward C. Points in a constant direction

9. What about our tilt? We are always tilted at 23° with respect to our revolution

10. Northern hemisphere SummerWinter

11. Opposite seasons for Southern hemisphere

12. Giant marine life discovered in Antarctica’s Ross Sea Associated Press March 21, 2008 late summer / early fall What season is it right now in Antarctica? A. Winter B. Spring C. Summer D. Fall

13. Our tilt remains the same

14. First day of Winter (Northern Hemisphere!) Winter solstice (December 22)

15. First day of Spring Sunlight shines directly into the board Spring (vernal) equinox March 20

16. First day of Summer Summer solstice (June 20)

17. First day of Fall Sunlight shines directly out of the board Autumn equinox Sept 22

18. Summers are warm because: The Sun is higher in the sky Days are longer

19. Path of the Sun wikipedia

20. Jupiter has a tilt of 3 degrees. Does it exhibit seasons? A. Yes B. No C. Cannot conclude

21. Calendars What use are calendars? Why have them?

22. What calendar do we use here? A. Julian B. Gregorian C. Hebrew D. World Calendar E. None of the above

23. Calendars of the world Islamic – Lunar. New month starts on crescent moon Chinese – Lunar and solar. New month starts on new moon

24. Mayan calendar

25. Calendars of the world Hebrew – lunar and solar: a leap month is inserted ~ every 3 years Julian: solar with 365.25 days in one year.  Every fourth year is a leap year.  (off by 11 minutes per year)

26. Gregorian calendar 365.2425 days In 1582, skipped from Oct. 4 to Oct. 14 Leap day inserted every 4 years British empire did not switch until 1752  Sept. 2 was followed by Sept. 14 in 1752

27. Stonehenge!

28. Chaco canyon

29. In class drawing In your notebook draw our orbit around the Sun

30. Label the following points First day of each season Longest day and shortest day Your birthday Perihelion, aphelion

31. Another drawing… Pretend you are facing South Label East and West Draw the path of the Sun through the sky on:  December 21 (winter solstice)  June 21 (summer solstice)  The equinoxes E W

32. In your own words Describe why the Earth has seasons (include angle of the Sun, length of days)

33. Discuss your answers With your group

34. If you took a picture of the Sun daily (same time and location) What shape would it trace out? This is called the Analemma.  What direction are we facing?  Where is summer solstice in this picture?  Where is winter solstice?