## 20101021

### Astronomy midterm question: implausible moonrise?

Astronomy 210 Midterm 1, Fall Semester 2010
Cuesta College, San Luis Obispo, CA

[20 points.] Consider the following excerpt describing the rising of a crescent moon:
The sun sank and the world was wreathed in shadows. But not for long, for see, in the east there is a glow...and at last the full bow of the crescent moon peeps above the plain...
--H. Rider Haggard, King Solomon's Mines: A Novel, Longmans, Green and Co., 1901, pp. 114-115.
Decide whether seeing a crescent moon rising soon after sunset is plausible or implausible. Support your answer using a diagram showing the positions of the sun, moon, Earth, and an observer.

• p = 20/20:
Correct. Waning crescent moon rises at 3 AM (also the waxing crescent moon rises at 9 AM), so it cannot rise (in the east) soon after sunset, as it will already be in the west part of the sky. May instead discuss that a waning gibbous moon (or full moon) would rise soon after sunset.
• r = 16/20:
Nearly correct (explanation weak, unclear or only nearly complete); includes extraneous/tangential information; or has minor errors.
• t = 12/20:
Contains right ideas, but discussion is unclear/incomplete or contains major errors. Problems with either diagram, phase, or time, but at least attempts to argue implausibility based on restrictions on when moon phase is visible or not visible.
• v = 8/20:
Limited relevant discussion of supporting evidence of at least some merit, but in an inconsistent or unclear manner. Problems with diagram, phase, and time.
• x = 4/20:
Implementation/application of ideas, but credit given for effort rather than merit. Explanation based on eclipses, solstices, etc.
• y = 2/20:
Irrelevant discussion/effectively blank.
• z = 0/20:
Blank.
Section 70158
p: 19 students
r: 4 students
t: 8 students
v: 7 students
x: 7 students
y: 2 students
z: 0 students

A sample "p" response (from student 7734):

Another sample "p" response (from student 1986):