20091016

Astronomy midterm question: telling "Moon-time"

Astronomy 210 Midterm 1, Fall Semester 2009
Cuesta College, San Luis Obispo, CA

[20 points.] Shown at right is an excerpt from a comic strip (Wizard of Id, Brant Parker and Johnny Hart, Creators Syndicate, June 28, 2009). Given the phase of the moon shown here, discuss a plausible time at night for the events depicted in this comic strip, using a diagram showing the positions of the sun, moon, and Earth.

Solution and grading rubric:
  • p = 20/20:
    Correct. Identifies the phase as waning crescent, which is highest overhead at 9 AM (rising at 3 AM, and setting at 3 PM), using a diagram of the sun, moon, and Earth. May choose anytime between 3 AM to 6 AM (sunrise) as being a plausible time at night for the events depicted in the comic strip.
  • r = 16/20:
    Nearly correct (explanation weak, unclear or only nearly complete); includes extraneous/tangential information; or has minor errors. May include 9 AM or any time after sunrise, or diagram has minor inconsistencies/errors.
  • t = 12/20:
    Contains right ideas, but discussion is unclear/incomplete or contains major errors. Problems with either diagram, phase, or time.
  • 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.
  • y = 2/20:
    Irrelevant discussion/effectively blank.
  • z = 0/20:
    Blank.
Grading distribution:
Section 70158
p: 15 students
r: 13 students
t: 7 students
v: 19 students
x: 0 students
y: 0 students
z: 0 students

A sample "p" response (from student 4614):

A sample "r" response (from 1623), who at least finds it strange that it is apparently dark outside:

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