20091019

Astronomy midterm question: telling "moon-time"

Astronomy 210 Midterm 1, fall semester 2009
Cuesta College, San Luis Obispo, CA

Shown at right is an excerpt from a comic strip (Baby Blues, Rick Kirkman and Jerry Scott, King Features Syndicate, August 2, 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:
    Correct. Identifies the phase as waxing gibbous, which is highest overhead at 9 PM (rising at 3 PM, and setting at 3 AM), using a diagram of the sun, moon, and Earth. May choose 9 PM, or anytime between sunset (6 PM) to 3 AM as being a plausible time for the events depicted in the comic strip.
  • r:
    Nearly correct (explanation weak, unclear or only nearly complete); includes extraneous/tangential information; or has minor errors. May include 3 PM in a range of plausible times, or diagram has minor inconsistencies/errors.
  • t:
    Contains right ideas, but discussion is unclear/incomplete or contains major errors. Problems with either diagram, phase, or time.
  • v:
    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:
    Implementation/application of ideas, but credit given for effort rather than merit.
  • y:
    Irrelevant discussion/effectively blank.
  • z:
    Blank.
Grading distribution:
Section 70160
p: 18 students
r: 2 students
t: 6 students
v: 12 students
x: 1 student
y: 2 students
z: 1 student

A sample "p" response (from student 1022), with a plausible range of times at night:
Another sample "p" response (from student ), with one chosen plausible time at night:
A sample "r" response (from student ), with daylight hours (3 PM-6 PM) included in the range of plausible times at night:
A sample "t" response (from student 5413), with the correct phase and a plausible time at night, but with a problematic diagram:

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