Caption: An animation illustrating the Big Crunch: the end fate of a certain class of Friedmann equation models which class does NOT apply to the observable universe in any sense according to our current observations.

This animation can't be taken very literally---it just gives a cartoon of the Big Crunch.

There is NO way to extrapolate the Friedmann equation models through a Big Crunch without extra hypotheses. But many have made such hypotheses and have theorized a cyclic universe evolving through cycles each consisting of a Big Bang, an expansion phase, a maximum phase, a contracting phase, and a Big Crunch. The ekpyrotic universe is cyclic universe model favored by at present.

Of course, in mythological cosmology and philosophical cosmology, many people have speculated on cyclic universes. The Stoic philosophers (c.300 BCE--300 CE) of Greco-Roman Antiquity (c.800 BCE--c.500 CE) are notable examples (Wikipedia: Stoic physics).

Immanuel Kant (1724--1804) in his book Universal Natural History and Theory of the Heavens (1755) gave a dynamical sketch of the galaxy formation and evolution in the framework of Newtonian physics, but only qualitatively (see Stephen Toulmin (1922--2009), June Goodfield (1927--), The Discovery of Time, 1965, p. 130--135). However, Kant went beyond Newtonian physics and pictured a cyclic universe where there was a cycle of conflagrations and rebirths of the universe. It seems likely that Kant for his cyclic universe was reaching far back to stoic physics.

Credit/Permission: User:Rogilbert, 2006 / Public domain.
Image link: Wikipedia: File:Big_Crunch.gif.
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File: Cosmology file: big_crunch.html.