Ask Ethan: Can someone possibly see the edge of spacetime?

In our Universe, in all directions and in all locations, there’s simply more “stuff” that space is full of everywhere we look. On the largest scales of all, the richest galaxy clusters and the sparsest cosmic voids average away, leaving us with a Universe that’s isotropic, homogeneous, and almost perfectly uniform. The oldest light in the Universe, the cosmic microwave background radiation, is a…