1. Assign. #1 distributed Friday Sep. 15. Due in your lab section slot, by 5 PM Sep 23. Office hours Mon, Thurs, and Friday this week. See Web page. Lab 1 will be due between Sep. 25 - 28. The motion of the Moon ANNOUNCEMENTS

2. The Moon, Our Constant Companion Why do we see phases of the Moon? What conditions are necessary for an eclipse? Why were eclipses difficult for ancient peoples to predict ? Our goals for learning: Note: the Chpt. 2 Moon tutorial on masteringastronomy.com is useful!

3. Animations Ecliptic Plane Orbit of Moon

4. Why do we see the same face? Rotation period = orbital period What do you see if you're standing on the Moon looking at Earth?

5. Animations Causes of lunar phases

6. Lunar Motion Phases of the Moon’s 29.5 day cycle (is that synodic or sidereal???) new Crescent first quarter gibbous full gibbous last quarter crescent Waxing Waning

7. The lunar phases Notice that the size seems to change. Why? Notice that it 'wobbles' a bit. Why?

8. The lunar phases Notice that the size seems to change. Why? Moon is not at a constant distance. Notice that it 'wobbles' a bit. Why? Because the orbital speed is not exactly constant Called 'librations'

9. Why do we see phases? Half the Moon illuminated by Sun and half dark We see some combination of the bright and dark faces

10. Preliminaries: Local Solar time Interactive applet at mastering astronomy.com

11. Phases of the Moon. An example: the waxing crescent From the publisher's web site.

12. Rising/setting times of the Moon Depending on the phase of the Moon it always rises and sets at the same (rough) local solar time. This is due to simple geometry of the illumination by the Sun. See Fig 2.21 of Cosmic Perspective. NOTE: The times above neglect the Earth's tilt!

13. Animations Phases of the Moon Rise/set time vs phase Handout given in class

14. Q: You see a quarter moon rising after drinking in the Pit. What time is it? A) 9 PM B) Midnight C) 3 AM D) 6 AM Bonus : First or Third quarter?

15. Eclipses : Puzzles for ancient astronomers/astrologers The Earth & Moon cast shadows. When either passes through the other’s shadow, we have an eclipse. Why don’t we have an eclipse every full & new Moon? Eclipses twice a month?

16. The Moon's orbit is inclined. Moon not necessarily in the ecliptic when it comes `into line' with the Sun

17. Animations Moon's orbit tilt Eclipse Seasons... How rare are eclipses

18. Eclipse Predictions Eclipses recur in the approx. 18 yr, 11 1/3 day saros cycle But even then, eclipse location and type (e.g., partial, total) may vary. Why?

19. Lunar Eclipses (way out of scale) From the publisher's web site.

20. Lunar Eclipse Sequence Is time going L to R or R to L ?????

21. Lunar eclipse geometry

22. Solar eclipse geometries Total Partial Annular

23. Does time go from right to left or left to right here? Time-lapse photo taken in northern Europe

24. Solar Eclipses Animation