In 1929, the astronomer Hubble observed that all the stars and galaxies were speeding away from us, so our universe is expanding everywhere. But if so, why is light from just after the big bang still all around us today, as cosmic microwave background? If the early light exploded outwards, why is it still all around us, instead of at the edge of the universe? Current physics doesn’t say, but space as the surface of an expanding bubble explains it (2.2.5).

A hypersphere surface has three dimensions like our space but also has no edges, like a balloon surface. It follows that our space is expanding everywhere at once, not just at an edge. Yet the surface of a bubble expanding thins out, while our space doesn’t seem to have changed in billions of years. This implies that we are on the inside of a bubble expanding into a larger bulk, not the outside of a stand-alone balloon (Figure 2.11). The surface of a bubble expanding in a liquid doesn’t thin out because its surface comes from the bulk around it, not itself. That surface also expands with no center or edge, so any waves vibrating on it will wrap around to end up everywhere. This explains why light from long ago is still all around us, as cosmic microwave radiation. It also answers questions like:
- What is space expanding into? It is expanding into the bulk around it.
- Does our universe end? No, a bubble surface has no end.
- Where is space expanding? Everywhere, just as a bubble surface expands everywhere at once.
- What creates new space? The bulk that contains the bubble creates new space.
- Are we expanding too? No, objects on a bubble surface don’t expand as the bubble does.
If space is a bubble surface that acts like a three-dimensional screen, it is homogenous but not continuous, expanding but not exploding, never-ending but not infinite, and curved not flat. Instead of objects being particles in space, they are expected to be waves on space. The next chapter explains light as waves on the surface of space, and the chapter after that derives matter from light.