1. Lecture 11 Moon Phases and Eclipses
Full Moon near Saturn
The Moon will be full on Sunday, 4/17/11 so on Saturday and Sunday night it will be near Saturn, which reached opposition last week and, like the full Moon, is on the opposite side of the sky as the Sun.
Instructor’s Notes: Demo Moon phases with moon globe, overhead

2. Except . . . In each phase of the Moon, how much of the Moon is
lit up by the Sun?
Half the Moon is always
lit by the Sun
Except . . .

3. When the Earth’s shadow hits the Moon we have a …….
Lunar Eclipse
ALWAYS a FULL MOON the night of a LUNAR Eclipse. (i.e. Moon is shadowed/eclipsed) (Earth is blocking the Sun’s light which produces a shadow on the Moon.)

4. Eclipses occur ONLY when the Moon crosses the plane of Earth’s orbit around the Sun AND ONLY during the NEW or FULL phases
Moon’s orbit is tilted about 5 degrees from the plane of the Earth & Sun.

5. Lunar Eclipse
When Earth blocks most of the sunlight from illuminating the Moons surface for several hours when in the full moon phase
The most recent total lunar eclipse was on December 21, The type and length of an eclipse depend upon the Moon’s location relative to its orbital nodes.
Unlike a solar eclipse, which can only be viewed from a certain relatively small area of the world, a lunar eclipse may be viewed from anywhere on the night side of the Earth. A lunar eclipse lasts for a few hours, whereas a total solar eclipse lasts for only a few minutes at any given place. In the middle the moon's surface appears red due to the only sunlight visible being refracted through the Earth's atmosphere on the edges of the earth in the sky, like a reddish sunset around the Earth illuminating the Moon’s surface.

6. When the Moon’s shadow hits the Earth, we have a ….
Solar Eclipse
NEW MOON when SOLAR ECLIPSE (Moon blocks Sun’s light producing a shadow on the Earth.)

7. Solar Eclipse Annular Eclipse Partial Eclipse Total Eclipse
An annular solar eclipse occurs when the Moon's apparent diameter is smaller than the Sun, causing the sun to look like an annulus (ring), blocking most of the Sun's light. An annular eclipse appears as a partial eclipse over a region thousands of kilometres wide.
A total eclipse occurs when the dark silhouette of the Moon completely obscures the intensely bright disk of the Sun, allowing the much fainter solar corona to be visible. During any one eclipse, totality only occurs at best in a narrow track on the surface of the Earth.
The last total eclipse was the solar eclipse of July 11, 2010; the next will be the total solar eclipse of November 13, The recent solar eclipse of January 15, 2010, was an annular eclipse; the next annular eclipse will occur on May 20, 2012.
The solar eclipse of January 15, 2010 was an annular eclipse of the Sun and lasted ~12 mins. The eclipse was visible as only a partial eclipse in much of Africa, Eastern Europe, the Middle East and Asia.

8. Eclipses occur ONLY when the Moon crosses the plane of Earth’s orbit around the Sun AND ONLY during the NEW or FULL phases
Remember that when the shadow falls on Earth it is a SOLAR ECLIPSE (always at NEW Moon) & when the shadow falls on the Moon it is a LUNAR ECLIPSE (always at FULL Moon).

9. Which positions cause which eclipses
When the ______ is in the _____ phase and is directly in line with the _____ and the ____ , you get a ______ eclipse?
Moon
full
Earth
Sun
lunar
When the ______ is in the _____ phase and is directly in line with the _____ and the ____ , you get a ______ eclipse?
Moon
new
Earth
Sun
solar

10. When the full Moon is rising in the East, what is the Sun always doing?
The Sun is always setting in the West.
Therefore the Sun and Moon are exactly ________ degrees apart…try a human animation if you are having difficulty visualizing this.
The only exception is …
180
…if there is a lunar eclipse, with the Moon crossing the line of nodes.

11. How are the motions and positions of Earth and the Sun connected to what happens on Earth?
Earth’s rotation on its axis determines the length of the day.
Earth’s orbit around the Sun determines the length of the year.
The tilt of Earth’s rotational axis with respect to the plane of Earth’s orbit causes the seasons.

12. The changing phases of the Moon originally inspired the concept of the month

13. Watch Movie at:

14. Moon Phase Names New Moon Waxing Crescent First Quarter Waxing Gibbous
Full Moon
Waning Gibbous
Third Quarter
Waning Crescent

15. The Causes of Moon Phases
Think to yourself about the answer to this question:
What causes the phases of the Moon?
Take out a piece of paper and quickly write out a brief answer.

16. How long does it take to complete the full cycle of Moon Phases?
About a day
About a week
About a month
About a year
None of the above
C: The Moon takes 27.3 days to orbit Earth, but the lunar phase cycle (from new Moon to new Moon) is 29.5 day which is what the question is asking about!
Check your answer with your partner!

17. Solar Period vs. Sidereal Period of the Moon
This image depicts the motion of the Moon around the Earth and the motion of the Earth (and Moon) around the Sun. Notice that numbers 1 and 9 are just New Moon.

18. Synodic (Solar) vs. Sidereal Period of the Moon
As it revolves around Earth, the Moon’s position in the sky changes with respect to the stars. In one sidereal month (27.3 days), the Moon completes one revolution (360 degrees) and returns to its starting point on the celestial sphere, having traced out a great circle in the sky.
The time required for the Moon to complete a full cycle of phases, one synodic month, is a little longer—about 29.5 days. This is the time for the Moon to go back to the same orientation relative to the Sun.
This link is a good reference, but realize you are not accountable for the sidereal year or the synodic year:
Note that Synodic contains an “so” think of this like “solar” since Synodic is measured relative to the Sun which leaves Sidereal as being measured relative to the stars.
Sidereal Period is days, Moon rotates to the purple line (which should be parallel to the leftmost red dotted line), 360 degrees; not back to New Moon - same phase as leftmost image
Synodic Period is days, Moon rotates to the orange line, more than 360 degrees; back to the same phase (new moon) as leftmost image.

19. Right now our Moon is just…
The Moon travels CCW (as seen from the N. pole) as it orbits the Earth over a month. (i.e. from West to East)
On a daily basis the Moon appears to travel opposite the Earth’s rotation (Earth goes West to East, CCW as viewed from North) and thus the Moon appears to go from East to West, similar to the Sun’s daily motion and Celestial Sphere’s (apparent) motion.

20. What phase is our Moon in right now? Just a day past First Quarter
Discuss light fills in from the right-ish side.
Lunar Calendar
The Moon travels CCW (as seen from the N. pole) as it orbits the Earth over a month. (i.e. from West to East)
On a daily basis the Moon appears to travel opposite the Earth’s rotation (Earth goes West to East, CCW as viewed from North) and thus the Moon appears to go from East to West, similar to the Sun’s daily motion and Celestial Sphere’s (apparent) motion.

22. Let’s Watch some Moon Phase Animations!
Pay attention to where the Moon, Sun and Earth are located and how the Moon appears from Earth at each of these positions.
Look at how much of the Moon is illuminated when at each position.
Look at which side of the Moon is illuminated when at each position.

23. Animation ZOOM IN
moonphase.html
Prepare for Human Animation! Get volunteers! Look at tidal locking.
Discuss plane of Moon’s orbit and angle.
The plane of orbit of the Moon about Earth is inclined at an angle of 5 degrees.

24. What is a monthly cycle & what is a daily cycle
What is a monthly cycle & what is a daily cycle? Label the daily times and how the Moon phases are broken up over time. Name the phases of the Moon that are shown. Discuss rising and setting.
Maybe discuss how the Moon is locked into orbit with same face toward Earth at all times. The moon is tidally locked with the earth. Show with moon mountains what it would look like if Moon never rotated about its own axis and had changing faces toward Earth. Use finger to show how same face of Moon toward Earth means the Moon rotates about its own axis once for each cycle of Moon phases (~30 days).

25. Although the Moon is always ½ lit by the Sun, we see different amounts of the lit portion from Earth depending on where the Moon is located in its month-long orbit.
DEMO. of how light illuminates half of Moon. NOTE that each of the eight phases shown here would have that moon’s phase directly overhead at the indicated time. E.g. The 1st quarter moon would be overhead at 6 pm, the Waxing Gibbous would be overhead at 9 pm, the full Moon would be overhead at midnight, etc. Assume the Earth is rotating to move the observer from one time to the next.

26. 1) How many phases shown in the picture will the Moon go through in one day?
2) How long does it take the Moon to complete one orbit? How many of the phases will the Moon have gone through in this time?
3) How long does it take the Earth to complete one rotation? How far will the Moon have moved?
4) How much of the Moons total surface is illuminated when it is in the New Phase? Full Phase?
5) How much of the illuminated surface of the Moon is visible from Earth when it is in the First Quarter Phase, Full Phase?
6) What time is it when the Waxing Gibbous Phase is highest in the sky, Rising? Setting? What phase will it be in one week later….see next slide for answer. SKIP RED PORTION.
ONE 2) ~30 days; it will have gone through all of the phases (the typical 8 phases and all in between) 3) 24 hours; 360 degrees/30 days = ~12 degrees/day
4) Half of the Moon is always illuminated 5) Half of the illuminated surface is visible in 1st quarter phase. All of the illum. surface is visible when the moon is in the Full Phase. 6) Highest in the sky about 9 pm; rising ~3 pm; setting ~3 am; One week later it will be in the Waning Gibbous phase.
Tell them that a fist with thumb on top of pointer finger is about 10 degrees wide across all fingers and that the scoop of the Big Dipper is also about 10 degrees.
[NOTE: Celestial Sphere appears to move 360 degrees in 24 hours as Earth rotates once. This means that 360 degrees/24 hours = 15 degrees per hour for the stars (and approximately for the planets) to appear to move relative to Earth.]

27. A Moon Phase is highest in the sky at 9 pm today
A Moon Phase is highest in the sky at 9 pm today. What phase will the Moon have in three weeks after today?
At 9 pm today and highest in the sky it will be Waxing Gibbous and three weeks later it will be Waxing Crescent (move CCW since it is MONTHLY, realizing that every other phase shown is one week, thus from D to F is one week, from F to H is the second week and from H to B is the third week).

28. Lecture Tutorial: Cause Moon Phases
Work with a partner!
Read the instructions and questions carefully.
Discuss the concepts and your answers with one another. Take time to understand it now!!!!
Come to a consensus answer you both agree on.
If you get stuck or are not sure of your answer, ask another group.
If you get really stuck or don’t understand what the Lecture Tutorial is asking, ask one of us for help.
Moon phases is 3 pages, thus ~15 mins to 24 mins.

29. Discuss here the scale, how large Earth is versus how large the moon is by comparison, the Moon has approximately 1/4 Earth's diameter . This explains how the light can curve or diffract around the Earth to reach the Moon when it is a full Moon.

30. A few more resources you might enjoy!
Animations:
more complex demo.
Useful information and tables as covered in class:
Gives information on the different moon phases and the times of day when they are visible.