Astronomy midterm question: big bang not like an explosion?

Astronomy 210 Midterm 2, fall semester 2010
Cuesta College, San Luis Obispo, CA

[20 points.] Consider the following statement regarding the big bang:

"The big bang did not explode into space like a bomb exploding..."
--Sujoy Desai, Uniphase: A Solution to Albert Einstein's "The Unified Field Theory," iUniverse, Bloomington, IN, 2003, p. 10.

Discuss why this statement is correct, and how you know this. Explain using observations and evidence related to the Hubble law.

Solution and grading rubric:

• p = 20/20:
  Correct. Hubble's law is that the recession velocity of galaxies is proportional to distance, evidence is that there is a greater redshift of absorption lines for distant galaxies compared to nearby galaxies. This is in opposition to an explosion, where the velocity of particles is inversely proportional to the distance from the center of the explosion. (Or may use Hubble's law to argue that there is no unique center to the expansion of space, in opposition to an explosion, which does have a unique center.)
  
• r = 16/20:
  Nearly correct (explanation weak, unclear or only nearly complete); includes extraneous/tangential information; or has minor errors. Discusses how Hubble's law expansion is not like an explosion, but does not explicitly discuss absorption line redshift evidence for Hubble's law.
  
• t = 12/20:
  Contains right ideas, but discussion is unclear/incomplete or contains major errors. Describes how an explosion is not like the actual expansion of the universe, but Hubble's law discussion is problematic or incomplete.
  
• v = 8/20:
  Limited relevant discussion of supporting evidence of at least some merit, but in an inconsistent or unclear manner. Discussion based on evidence of the earlier stages in the history of the universe, with little or no substantive discussion of Hubble's law.
  
• 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: 8 students
r: 14 students
t: 7 students
v: 7 students
x: 9 students
y: 0 students
z: 1 student

A sample "p" response (from student 1122):
Another sample "p" response (from student 1021):
A sample "x" response (from student 4146):
A sample "x" response (from student 4130), tossing in a "bing bang [sic]" reference:
A sample "x" response (from student 7183), with a personal message: