1. Announcements:
Assignment for Monday: read chapter 4 of text
No quiz on Monday. However, we will start class with two very simple questions from Chapter 4. Anyone who read the chapter should be able to answer these questions.
Look for news on Thursday about Kepler - homework extra credit if you write a one paragraph summary of what you learned

2. Chapter 3
Cycles of the Moon

3. New Moon

4. Waxing Crescent

5. 1st Quarter

6. Waxing Gibbous

7. Full Moon

8. Waning Gibbous

9. 3rd/Last Quarter

10. Waning Crescent

11. All Together

12. The diagram below shows Earth and the Sun as well as five different positions for the Moon. Which position of the Moon best corresponds with the phase of the Moon shown in the figure to the right? 1 5
Earth
Sun 2 4 3
Not to Scale

13. Review: Phases of the Moon
If the moon reaches full phase on May 6, it is at _____ phase on May 17.
new
waxing crescent
waxing gibbous
waning gibbous
waning crescent

14. The third quarter phase moon rises at about:
Review: Phases of the Moon
The third quarter phase moon rises at about:
sunrise.
noon.
sunset.
midnight.
There is no way to predict the time that a particular phase rises.

15. The Moon’s Orbit
The Earth exerts tidal forces on the moon’s rocky interior.
→ It is rotating with the same period around its axis as it is orbiting Earth (tidally locked).
→ We always see the same side of the moon facing Earth.

16. An astronaut on the Moon would see the Sun rising
a. every 24 hours
b. every week
c. every month
d. never
An astronaut on the Moon would see the Earth rising
a. every 24 hours
b. every week
c. every month
d. never

17. Moon’s Orbit: 12% variation over one lap!
VERY EXAGGERATED
Apogee: farthest from Earth
Perigee: closest to Earth

18. The Moon’s Orbit
Moon’s orbit about Earth is not perfectly circular. The consequence is that the Moon gets slightly larger and smaller in the sky. The change is only about 12%!

19. Inclination of Moon’s Orbit
Inclination of orbital plane relative to the ecliptic is 5.14 degrees.
= ~10 moon diameters

20. Lunar Eclipses
Earth casts its shadow out into space as it orbits the Sun. The Moon is eclipsed when it passes in the Earth’s shadow. Earth’s shadow is larger than Moon.

21. A total lunar eclipse can last up to 1 hour and 40 min.
Lunar Eclipses
A total lunar eclipse can last up to 1 hour and 40 min.
During a total eclipse, the moon has a faint, red glow, reflecting sun light scattered in Earth’s atmosphere.

23. Total Lunar Eclipse of 2/20/08
Visible across the Americas, Europe and Africa
Totality lasts nearly an hour
Distinctive “red glow”

24. Of the six total lunar eclipses listed in this table, which two definitely cannot be observed by someone under clear skies located in Greenwich, England?
Feb 21, 2008 and June 15, 2011
Dec. 21, 2010 and December 10, 2011
Dec 10, 2011 and Oct. 8, 2014
Feb. 21, 2008 and June 15, 2011

25. Solar Eclipses
Moon’s shadow is small. Sun is eclipsed for observers within the Moon’s shadow.
Typical speed: 1000 MPH
Size of Shadow: 100 miles

26. Solar Eclipse Geometry
So….. What phase of the Moon must it be to have a solar eclipse?

27. Observing a Solar Eclipse

28. Observing a Solar Eclipse
Total Solar Eclipse
March 29, 2006, Side, Turkey

29. Observing a Solar Eclipse
Annular Eclipse
May 30, 1984

30. Observing a Solar Eclipse
March 29, 2006
Adrasan, Turkey
Digital Mosaic
Totality: about 4 minutes

31. 2006 Total Solar Eclipse

32. 360 Sunset During the Eclipse

33. Solar Eclipse Seen from Space

34. …. And another

35. How Often Do They Occur
Moon’s orbit “precesses” (wobbles) so that the node moves Eastward about 20 degrees per year
Sun crosses node about every 173 days
When Sun is near the node, it is “eclipse season” and solar and lunar eclipse occur two weeks apart
About two node crossings per year

36. Ecliptic and Moon’s Orbit Offset by 5
35 days for possible overlap. (It takes the Sun 35 days to travel this far across the sky Only about 3 days for Moon to cover the same angle.)

37. Frequency of Lunar vs. Solar Eclipses
It is much more probable that you will see a Lunar eclipse only because significantly more people on Earth can see it at the same time.
Lunar eclipses are not more frequent than solar eclipses.

38. We can see total solar eclipses because:
the linear diameters of the sun and the moon are almost equal.
the distances to the sun and the moon are about the same.
the angular diameters of the sun and the moon are almost equal.
total solar eclipses would be visible on any planet with a moon.
the moon always shows the same face to the Earth.

39. Observing a Solar Eclipse
A total lunar eclipse lasts much longer than a total solar eclipse. Why?