Closed universe

Noun
1. (cosmology) a universe in which there is sufficient matter to halt the expansion that began with the big bang and to cause the universe to collapse again; the visible matter is only 10 percent of the matter required for closure but there may be large amounts of dark matter
(hypernym) universe, existence, creation, world, cosmos, macrocosm
(classification) cosmology, cosmogony, cosmogeny

Any model of the universe in which the ratio of the mean density of the universe to the critical density is greater than one. Our universe is observed to be expanding. However, the expansion is slowed by the gravity of the matter within it. If there is enough matter for the expansion to be halted and then reversed, the universe will collapse and a big crunch will be brought about. Observations suggest that the luminous matter in the universe, for example, stars and galaxies, provide only ten per cent of the material needed to make the mean density of the universe equal to the critical density. Inflationary cosmology demands that the density is equal to the critical density. So, for this theory to be correct, there must be vast amounts of dark matter making up the missing mass.