The putative end-state of a closed Friedmann universe (i.e. one in which the density exceeds the critical density). Such a universe expands from an initial Big Bang, reaches a maximum radius, and then collapses to a Big Crunch, where the density of matter becomes infinite. After a Big Crunch, there could be another phase of expansion and collapse, leading to an oscillating universe.
Subjects: Astronomy and Astrophysics.