Astronomy midterm question: low west sunset Venus?

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

Consider the following excerpt regarding viewing Venus just after sunset:

"The stars were just now appearing, but to the west, a single point of light glowed brighter than any other. Langdon smiled when he saw it. It was Venus."
--Dan Brown, The Da Vinci Code: A Novel, Random House, New York, NY, 2003, p. 589.

Discuss whether this is plausible or implausible. Support your answer using a diagram showing the positions of the sun, Venus, and Earth.

Solution and grading rubric:

• p = 20/20:
  Correct. Discusses the plausibility of this scenario by drawing a diagram with Venus' orbit closer in to the sun than Earth's orbit, making it possible for an observer at sunset to observe Venus low on the west horizon.
  
• r = 16/20:
  Nearly correct (explanation weak, unclear or only nearly complete); includes extraneous/tangential information; or has minor errors. Draws Venus in the correct position in its orbit relative to Earth such that it would be seen just after sunset, but concludes that this would be implausible.
  
• t = 12/20:
  Contains right ideas, but discussion is unclear/incomplete or contains major errors. Argues plausibility or implausibility based on drawing Venus in its orbit relative to Earth such that it would be visible in the east horizon at sunrise, or is transiting the sun.
  
• v = 8/20:
  Limited relevant discussion of supporting evidence of at least some merit, but in an inconsistent or unclear manner. Draws a problematic diagram with Venus' orbit larger than Earth's orbit, or in a geocentric orbit around Earth.
  
• x = 4/20:
  Implementation/application of ideas, but credit given for effort rather than merit. Incomplete/inconclusive diagram, or argument based on retrograde/prograde motion.
  
• y = 2/20:
  Irrelevant discussion/effectively blank.
  
• z = 0/20:
  Blank.
  

Grading distribution:
Section 70158
p: 17 students
r: 5 students
t: 16 students
v: 11 students
x: 3 students
y: 2 students
z: 0 students

A sample "p" response (from student 1234):
A sample "r" response (from student 2388), with an incorrect conclusion, despite a correct diagram:
A sample "t" response (from student 7873), depicting Venus low in east horizon at sunrise:
A sample "v" response (from student 1781), using a geocentric model with phase/timing/horizon inconsistencies: