Bubbles, Voids, and Walls

Abstract

One of the predictions of the big bang model is that the universe is smooth. Yet we know that it’s not perfectly smooth. The galaxies in our region of space are not distributed uniformly. If you could get far enough away and look at them, however, they should appear to be uniformly distributed, in other words, smooth. It’s like looking at the sand on a beach. Up close it’s easy to see that there are individual grains. If you move back a little, though, you can no longer see the grains, but you still see the mounds and nonuniformities in the surface. If you move back far enough, though, the beach appears perfectly uniform. According to the big bang theory, we should have a similar situation in the case of the universe; in other words, if you viewed it on a very large scale, it should appear uniform.