1. Goal: To understand the moon as we view it.
Objectives:
To learn about the Phases of the moon.
To understand eclipses
To see the surface of the moon.
To know the make up of the moon.

2. Phases of the moon
Every 29.5 days the moon goes through a cycle that you see on the right.
There are 8 phases.
Phase 0/8 – new moon (bottom right)
Phase 1 – waxing crescent (top row)
waxing = light is growing
Phase 2 – first quarter (far left of 2nd row)
Phase 3 – waxing gibbous – 3rd row
Phase 4 – full moon – first of row 4
Phase 5 – waning gibbous (rest of row 4)
waning = light is shrinking
Phase 6 – 3rd quarter (2nd + 3rd of row 5)
Phase 7 – waning crescent (first 3 of bottom row)

3. How many days of sunlight per lunar month does the far side of the moon (sometimes called the “dark side”) get?
A) 0 days
B) ~ 1 day
C) ~ 7.4 days
D) ~ 14.7 days
E) ~ 3.7 days

4. How many days of sunlight per lunar month does the far side of the moon (sometimes called the “dark side”) get?
D) ~ 14.7 days – same as the near side
The far side gets just as much sunlight as the near side.
We just never see the far side because it is “tidally” locked to the earth (i.e. the rotational period is equal to the orbital period).
Therefore we only see one of the sides of the moon.

7.
We shall now examine why the phases are created.
They are a combination of the moons orbit around the earth with the fact that only the side facing the sun is lit.

8. Elongation of the moon
The elongation of the moon is the angle made by the sun to the earth to the moon.
Each phase is based on the elongation, and lasts for 45 degrees.
So, the new moon (Phase # 0 or 8) starts at 0 degrees, and ends at 45 degrees.
The Waxing Crescent (phase #1) would start at 45 degrees and end at 90 degrees.

9. Phases vs rise and set times of the moon
Therefore, each phases will rise and set at a different time of day.
If you remember back to the beginning of the semester when we looked at the motions of stars we learned that the earth rotates 15 degrees per hour.
Therefore for every 15 degrees that the sun leads ahead of the moon, it will take 1 hour for the earth to rotate from when the sun rises to when the moon will rise after it.

10. If the moon has an elongation of 150 degrees (waxing gibbous), and the sun rises at 6 AM, about what time will the moon rise? HINT: earth rotates 15 degrees per hour
A) 6 AM
B) 11 AM
C) 4 PM
D) 6 PM
E) 11 PM

11. If the moon has an elongation of 150 degrees (waxing gibbous), and the sun rises at 6 AM, about what time will the moon rise?
C) 4 PM
Which is 150/15 = 10 hours after the sun rises. 6 AM + 10 hours = 4 PM
What time will the moon set (hint, how many hours per day is the sun up?)?

12. If the moon has an elongation of 150 degrees (waxing gibbous), and the sun rises at 6 AM, about what time will the moon rise?
C) 4 PM
Which is 150/15 = 10 hours after the sun rises.
What time will the moon set?
4 AM – 12 hours later.
(also good to note that every night the moon rises and sets about 50 minutes later)

13. What path does the moon make in the sky?
A) It makes a circle along the ecliptic plane.
B) It makes a circle along the celestial equator.
C) It does not make a circle.
D) None of these.

14. The Moon’s orbit
The moon’s orbit is offset from the ecliptic by 5 degrees.
So, most of the time when it is in front of or behind the earth, it does not fall directly in line with the sun (for example in the new moon it would pass directly above or below the sun).
There are 2 places in the orbit called the “nodes” where the plane of the moon’s orbit intersect with the ecliptic plane.
When these intersect at either the new moon or full moon….

15. Lunar Eclipse
At the full moon, if it lines up onto the node, will be eclipsed.
This happens twice per year (with less than half of the earth being able to witness it – which means you can witness about 1 lunar eclipse every 1-2 years on average).
There are 3 types of lunar eclipses.

17. This why the moon turns red during a total lunar eclipse.
Next lunar eclipses viewable from N. America will be 6 AM, October 8th, 2014 (yes that is a week from tomorrow!), April 4, 2015, and Sept 28, 2015

18. Solar Eclipse
Similarly, the moon can block the sun when it lines up correctly in the new moon.
However, since the moon is much smaller than the earth, the shadow is much smaller, and only a small part of the earth is cast in the moon’s shadow.
While there are still 2 eclipses per year, the main effect is limited to smaller areas, so to view them from a specific city is far more rare.
Next solar eclipse viewable from the lower 48 U.S. states will be August 21, 2017 (might want to head to Kentucky that day)
There are also 3 types of solar eclipses.

19. Partial eclipse:
The moon only covers up part of the sun.
Annular eclipse:
Since the moon’s orbit is ELLIPTICAL, in some portions of the orbit it will appear smaller.
If the angular size of the moon is less than the sun, it will create a dark circle on the sun, but NOT entirely cover up the sun.

20. Annular Eclipse vs Total Eclipse

22. Dark areas = lunar mare (seas)
Light areas are the Lunar Highlands.
The moon is dotted by numerous caters.

23. Mare vs highlands
Notice the mare have a few craters, but not nearly as many as the highlands.
Meanwhile the highlands are covered with them.
The mare are only 4.0 billion years old.
The early solar system was known as the era of heavy bombardment – where debris was everywhere, so impacts occurred in great numbers.
By the time the mare formed, the bombardment had ended.

24. Surface of the moon:
Why are there so many craters down to such small sizes, and why do they remain today?

25. No water or atmosphere!
No water means no erosion. So, craters stay until covered up by landslides or future craters.
No atmosphere (or at best a few particles of one) means single atoms can hit the moon. Therefore there are craters even down to the microscopic level.
These are challenges we will be faced with if we ever colonize the moon.

26. Earth viewed from the moon!
The earth would have phases also.
However, since the moon rotates at the same rate it orbits, the earth would stay centered on 1 spot in the sky.
Even at night,
you would see the
earth (in fact, you
would have a full
earth during the
night, and new
earth during the day

27. Conclusion
Moon has phases which are determined by the moon’s position in its orbit around the earth.
The moon has some interesting surface conditions.
The moon formed due to a Mars sized object colliding with the earth.
There will be many challenges when colonizing the moon.