A common model used to illustrate this is to imagine yourself a two dimensional creature living on the surface of an inflating sphere (or balloon). The big bang is represented by the sphere beginning to inflate from an isolated point at time t=0. As time passes, the sphere swells. This represents the empirically observed fact that the universe is expanding!

The expansion of the universe was discovered by Edwin Hubble (the namesake of the Hubble space telescope) in the 1920's. He observed that the farther away a galaxy is, the faster it is receding from us. In our model, this is reflected by the fact that as the sphere inflates, any two points will get farther and farther away from each other, and the father apart two points are, the faster apart they move.

Goto Section 2.