Penrose has a crazy theory where he considers what the universe looks like after the heat-death. After all the blackholes evaporate and photons are the only thing left.
Since photons travel at the speed of light, neither distance nor time are measurable. All that remains is the relative angular concentration of photons. If you imagine the universe as a sphere, the relative concentration of photons represents the pattern on the surface of the sphere.
However there's no longer any way to determine that sphere's size nor whether it is expanding, contracting or even the existence of time itself.
The crazy thing is how close this is to the early universe. You start with the cosmic microwave background pattern and that's basically also exactly what you end up with: a pattern/projection of photons where space and time basically become meaningless or cease to exist.