From what I have gathered, M-theory states that there are 11 dimensions. We live in 4 of these dimensions, and I believe the common understanding is that the 7 other dimensions are incredibly small. At the time of the Big Bang, these 3 dimensions expanded along with the universe while the others remained small. My question is this: Why did these other dimensions remain small? Also, if these dimensions had never expanded, does this mean that they would be found at the "center" of the universe?