Cuesta College, San Luis Obispo, CA
[20 points.] Consider the following comment:
"The Universe has as many different centers as there are living beings in it. Each of us is a center of the Universe..."Discuss why observers in different galaxies would each think that they are the center of expansion for the universe. Explain using Hubble's law.
—Aleksander Isaevich Solzhenitsyn, The Gulag Archipelago: 1918-1956, Harper & Row Publishers, 1985, p. 3.
Solution and grading rubric:
- p = 20/20:
Correct. Explains how Hubble's law (recession velocity is proportional to distance) corresponds to the expansion of space between galaxies, such that each galaxy seems to be center of expansion as observed from their position. May use analogies as not-like-an-explosion, raisin bread, enlargement of between-spaces, etc.
- 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. Typically Hubble's law discussion is missing or problematic.
- v = 8/20:
Limited relevant discussion of supporting evidence of at least some merit, but in an inconsistent or unclear manner.
- 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:
p: 16 students
r: 11 students
t: 20 students
v: 4 students
x: 0 students
y: 0 students
z: 0 students
A sample "p" response (from student 8260):
Another sample "p" response (from student 1989):
A sample "t" response (from student 1781), with no explicit discussion of Hubble's law, but still capturing the essence of the relativeness of galaxies receding from all observers::
A sample "v" response (from student 2522), appealing to a version of the Copernican principle: