Is There an Edge to the Universe?
The phrase “edge of the universe” sounds intuitive. Cosmology makes it much less straightforward.
An edge would be a boundary beyond which the universe simply stops. Current cosmological models do not require such a boundary. The universe could be spatially infinite, or it could be finite yet have no edge—similar in concept to how Earth’s surface has finite area but no boundary line you can fall off.
The observable universe
There is, however, a limit to what we can observe. Light has travelled for a finite amount of time, and cosmic expansion affects which regions can ever send signals that reach us. This creates an observable universe: the region from which information is accessible to us in principle.
A horizon is not a wall
A cosmological horizon is a limit on information, not a physical barrier. Objects beyond a particular horizon are not necessarily absent. They may simply be unreachable by signals under the universe’s expansion history.
What lies beyond?
That depends on the global geometry and topology of the cosmos. Observations are consistent with a universe that is very close to spatially flat on large scales, but “flat” does not by itself answer whether the universe is finite or infinite.
The useful distinction
The important distinction is between “the universe” and “the part of the universe we can observe.” The latter is necessarily limited by light travel time, cosmic expansion and the information available to our instruments.
So the universe may have horizons for us without having an edge in the everyday sense. The boundary is often a boundary of knowledge and communication, not a boundary in space.