The condition in which there is sufficient matter in the universe to halt the expansion driven by the Big Bang and cause eventual re-collapse.
- ‘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’.’
We take a look at several popular, though confusing, punctuation marks.