Something occurred to me the other day when looking at pictures of the universe. This might be obvious to some, and probably should have been obvious to me, but I realised that the big bang describes the expansion of space, not matter. Because gravity causes matter to clump together, at some point in the younger universe matter must have been more widely and more evenly distributed. So why when we look at the sky do we see individual and unique pockets of matter? A pocket here, a pocket there, looooots of space in between. Why is there some hydrogen over here, some oxygen over there and no uniformity to the world we see around us? Wouldn't that suggest that space/matter was never uniform to begin with and that the big bang never occurred evenly everywhere at once? Surely there must have been some "events" which took place that caused regions of the universe to take on a unique identity, for instance one pair of particles interacting differently than another pair of particles, is there any indication as to what those events were? Perhaps random fluctuations?