Based on the context and the answer, generate a question. 

Context: The volume of space in which these bits of matter could be found would increase as time went by . Is this a good analogy for the expansion of the universe ? The fact that we say the universe started with the " big bang " would seem to suggest it . But in fact , no , that is not a good analogy . That is not what we mean when we say the universe is expanding .

Answer:

Astronomy



What may I have been studying ?