The observable universe is not necessarily the whole universe
The observable universe is the region from which signals have had time to reach us during cosmic history. Its boundary is a limit on available information, not a known physical wall. Space may continue beyond it, and observers elsewhere would have observable regions centred on their own locations.
Go deeper
A horizon set by cosmic history
The universe has a finite age, and signals travel at finite speed. These facts limit the region from which information could have reached us.
Cosmic expansion makes the geometry more subtle than drawing a sphere whose radius is simply the universe's age multiplied by light speed. Distances have changed while light has travelled.
An observational boundary does not establish an edge to all space. It separates what can contribute information to our observations from what lies beyond that historical reach.
- Our location defines our observable region.
- A distant observer has a differently centred region.
- Unobservable does not mean nonexistent.
The total universe could be much larger than the region we can observe. Its full extent is not determined simply by measuring the boundary of our observable portion.