The condition in which there is sufficient matter in the universe to halt the expansion driven by the Big Bang and cause eventual recollapse. The amount of visible matter is only a tenth of the total required for closure, but there may be large quantities of dark matter.
- ‘While a flat universe can extend indefinitely in all directions, the closed universe is finite.’
- ‘Wait a few billion years for the newly closed universe to stop its expansion, collapse to a singularity, and - Presto! - give birth to a brand new, energy-rich universe, to do with as you please.’
- ‘Assuming the Big Bang model, a closed universe would eventually collapse back onto itself, if there was enough dark matter.’
- ‘Also, analysis of Type Ia supernovae shows that the universe's expansion rate is not slowing enough for a closed universe. It seems like there is only 40-80% of the required matter to cause a ‘big crunch’.’