## 20180310

### Astronomy midterm question: Venus setting at sunset, then eventually rising at sunrise?

Astronomy 210 Midterm 1, spring semester 2018
Cuesta College, San Luis Obispo, CA

The following explanation was given on an online discussion board[*]:
Say Venus is setting in the west right after sunset. After a few months, Venus will have moved faster in its orbit than Earth such that Venus will next be visible in the east just before sunrise.
Discuss why this answer is correct for an observer in San Luis Obispo, CA, and how you know this. Support your answer using diagrams showing the positions of the sun, Venus, Earth, and an observer on Earth.

[*] answers.yahoo.com/question/index?qid=20180302021141AAdHysp.

Solution and grading rubric:
• p:
Complete diagram and reasoning includes the following explanations for an observer on Earth looking at Saturn:
1. Venus's position in its orbit around the sun is "behind" Earth's position in its orbit around the sun such that the observer on Earth at sunset is able to see Venus setting in the west; and
2. a few months later, Venus has "caught up and pulled ahead" of Earth, such that the observer on Earth at sunrise is able to see Venus rising in the east.
• r:
Nearly correct (explanation weak, unclear or only nearly complete); includes extraneous/tangential information; or has minor errors. Draws both diagrams: one correct, the other with slight errors.
• t:
PContains right ideas, but discussion is unclear/incomplete or contains major errors. Draws both diagrams with errors; or has one diagram correct, the other missing/problematic.
• v:
Limited relevant discussion of supporting evidence of at least some merit, but in an inconsistent or unclear manner. Some attempt at one diagram, with errors; the other is missing or effectively missing.
• x:
Implementation/application of ideas, but credit given for effort rather than merit.
• y:
Irrelevant discussion/effectively blank.
• z:
Blank.
Grading distribution:
Section 30676
Exam code: midterm01sNuB
p: 23 students
r: 4 students
t: 5 students
v: 4 student
x: 9 students
y: 0 students
z: 0 students

A sample "p" response (from student 2000):