Open universe

Definition

An open universe is a cosmological model where the universe will expand forever without recontracting. It implies that the curvature of space is negatively curved, resembling a saddle shape.

5 Must Know Facts For Your Next Test

1. An open universe has a total density less than the critical density required to halt expansion.
2. In an open universe, the geometry of space is hyperbolic or negatively curved.
3. Open universes predict that galaxies will continue to move away from each other indefinitely.
4. The concept of an open universe arises from solutions to Einstein's field equations in general relativity.
5. Observations of cosmic microwave background radiation and galaxy distributions help determine whether our universe is open.

Review Questions

• What distinguishes an open universe from a closed or flat universe in terms of density?
• How does the geometry of space in an open universe differ from other models?
• Why would galaxies continue to move away from each other indefinitely in an open universe?

Related terms

closed_universe: A cosmological model where the universe will eventually stop expanding and begin contracting, with positively curved space.

flat_universe: A cosmological model where the universe's expansion slows but never quite stops, with zero curvature.

cosmic_microwave_background_radiation: The thermal radiation left over from the Big Bang, providing key evidence for different cosmological models.