Closed universe

Definition

A closed universe is a cosmological model where the universe is finite and will eventually stop expanding, leading to a contraction or 'Big Crunch.' It implies that the geometry of the universe is positively curved, like the surface of a sphere.

5 Must Know Facts For Your Next Test

1. In a closed universe, the total mass-energy density exceeds the critical density.
2. The geometry of a closed universe is spherical, meaning parallel lines will eventually converge.
3. A closed universe will stop expanding and begin contracting due to gravitational forces overcoming the expansion momentum.
4. The fate of a closed universe is often described as ending in a 'Big Crunch,' where all matter collapses into a singular point.
5. Observations and measurements of cosmic microwave background radiation are crucial in determining whether our universe could be closed.

Review Questions

• What happens to the expansion of a closed universe over time?
• How does the geometry of a closed universe differ from an open or flat universe?
• What critical factor determines whether a universe can be classified as closed?

Related terms

Big Bang Theory:

The prevailing cosmological model explaining the origin of the observable universe from an initial singularity approximately 13.8 billion years ago.

Critical Density:

The specific value of mass-energy density needed for the universe to have zero curvature, serving as a threshold between open and closed universes.

Open Universe:

A cosmological model where the universe will expand forever because its mass-energy density is less than the critical density, resulting in negative curvature.