Flexi Says: The shape of the universe is still being researched and debated by astronomers. The universe may be closed in on itself like a sphere, or it may be open like a flat sheet that extends infinitely in all directions. If the actual density of the universe is greater than the critical density, which is the square of the Hubble constant and is used to measure the expansion rate of the universe, then the universe contains enough mass to stop its expansion eventually. In this case, the universe is closed and finite, though it has no end and has a spherical shape. However, if the actual density of the universe is equal to the critical density, which is also as per the measurements performed by scientists, then the universe is considered flat and infinite in size.
