Let me take the oportunity to use this post for which
it was orignally intended twake:

If a closed universe is expanding there is no edge.
Instead the space inbetween the galaxies is stretching.
What is interesting is that in cosmology the light
transversing this space is also stretched. It gets
longer and less energetic. This redshift is how we
determine their distances.

If there is no boundary the universe can be seen to
be the surface of a hypersphere.