1. Lecture 4
ASTR 111 – Section 002

2. Terms Apogee/Perigee Subtend Parsec, light-year, AU Parallax
While you are waiting for class to start, try to define these terms
Apogee/Perigee
Subtend
Parsec, light-year, AU
Parallax
Solar and Sidereal time
Small angle formula
Ecliptic
Zenith
Tropic of Cancer, Capricorn, Artic and Antarctic Circle
Equinox, Solstice
Zodiac
Accuracy, Precision, and Bias

3. First Exam
Slated for 9/29
Based on lecture notes, problems worked in lecture, and quizzes.
Approximately 50 questions
In the Testing and Tutoring Center (using Blackboard system).

4. Tuesday September 15th Class is canceled.
Quiz is still due at 9 am on the 15th.
I will be available via .

5. Outline Quiz Discussion Rotation – review generally
The Seasons – review generally
The Moon in its orbit
Math review

6. Quiz Discussion

8. Outline Quiz Discussion Rotation – review generally
The Seasons – review generally
The Moon in its orbit
Math review

9. Rotation

10. Outline Quiz Discussion Rotation – review generally
The Seasons – review generally
The Moon in its orbit
Math review

11. The Seasons

12. Outline Quiz Discussion Rotation – review generally
The Seasons – review generally
The Moon in its orbit
Math review

13. From http://www.dslreports.com/forum/remark,16822681
Uses color saturation
The Moon in its orbit

14. Eventually we want to be able to explain …

15. A simple model Moon executes circular orbit
Moon orbit is in Earth’s ecliptic plane

17. Looking down on North Pole
NO! You would need to see through Earth!
Can you “see” white ball if you are at Equator?

18. What is wrong with this picture?

19. Looking down on North Pole
Can you “see” white ball if you are at Equator?

20. Looking down on North Pole
If you walk around along the equator, where will you be able to see the white ball?

21. Looking down on North Pole
Can you “see” white ball if you are at Equator? NO! You would need to see through Earth!

22. Looking down on North Pole
Can you “see” white ball if you are at Equator? NO! You would need to see through Earth!
NO!

23. Looking down on North Pole
Closer to scale

24. Draw a diagram that explains when you will first be able to see the first quarter moon if you live on the equator.
Stated another way, at what time will you see the 1st quarter moon rise from Earth?

26. Fill in the dark and light parts of the Moon for A-D (from this perspective)
From the perspective of someone on Earth what position of A-E best fits the Moon view in the lower-left-hand corner?
In the blank boxes below, sketch how the Moon would appear from Earth from the four Moon positions that you did not choose for Question 2. Label each box with a letter. A E
Sun’s rays
Earth D B C
View of Moon from Earth at one of the
positions (A-E) above.

27. Shade in the part of the Moon that is not illuminated by the sun when it is at positions F-I.
Which Moon position (F-I) best corresponds with the Moon phase shown in the lower-left corner?
How much of the Moon’s surface is illuminated by the sun during this phase?
How much of the Moon’s illuminated surface is visible from Earth for this phase of the Moon? G
Sun’s rays F H
Earth I
View of Moon from Earth from one of the positions (F-I) above.

28. A simple model Moon executes circular orbit
Moon orbit is in Earth’s ecliptic plane

29. Model can explain the phases of the Moon
The phases of the Moon occur because light from the Moon is actually reflected sunlight
As the relative positions of the Earth, the Moon, and the Sun change, we see more or less of the illuminated half of the Moon.

30. What does the Earth look like from the Moon at
Full Moon
New Moon
First Quarter
Third Quarter

32. What are 2 observations simple model does not predict?

33. What are 2 observations simple model does not predict?
Why there are not eclipses every month
Why there are “annular” and “total” eclipses

34. Eclipses occur only when the Sun and Moon are both on the line of nodes

36. What are 2 observations simple model does not predict?
Why there are not eclipses every month
Why there are “annular” and “total” eclipses of the sun

37. Solar eclipses can be either total, partial, or annular, depending on the alignment of the Sun, Earth, and Moon

40. Eventually we want to be able to explain …

41. Lunar eclipses can be either total, partial, or penumbral, depending on the alignment of the Sun, Earth, and Moon

42. Question
If you were looking at Earth from the side of the Moon that faces Earth, what would you see during
A total lunar eclipse?
A total solar eclipse?

43. The Moon’s rotation always keeps the same face toward the Earth due to synchronous rotation

44. Time and the Moon
Two types of months are used in describing the motion of the Moon.
With respect to the stars, the Moon completes one orbit around the Earth in a sidereal month, averaging days.
The Moon completes one cycle of phases (one orbit around the Earth with respect to the Sun) in a synodic month, averaging days.

46. sidereal month, averaging 27.32 days.
sidereal day – 23 hr 56 min
synodic (lunar) month, averaging days.
solar day – 24 hr

47. Question
On a certain date the Moon is in the direction of the constellation Gemini as seen from Earth. When will the Moon next be in the direction of Gemini?
One year later?
days later?
One sidereal month later?
One synodic month later?

48. Outline Quiz Discussion Rotation – review generally
The Seasons – review generally
The Moon in its orbit
Math review