In physical cosmology, the big crunch is one possible scenario for the ultimate fate of the universe, in which the metric expansion of space eventually reverses and the universe recollapses, ultimately ending as a black hole singularity.
Overview
If the gravitational attraction of all the matter within the observable horizon is high enough, the expansion of the universe eventually reverses. In the absence of a cosmological constant, this happens when the matter density exceeds the critical density. Because entropy continues to increase in the contracting phase, the contraction looks very different from the time reversal of the expansion. While the early universe was highly uniform, a contracting universe would become increasingly clumped. Eventually all matter would coalesce into black holes, which would then coalesce with each other; the unified black hole singularity is the big crunch singularity. (The big bang singularity, in contrast, does not resemble a black hole or white hole singularity.) Recent experimental evidence (namely the observation of distant supernovae as standard candles, and the well-resolved mapping of the cosmic microwave background) have shown that the expansion of the universe is not being slowed down by gravity but rather accelerating. However, since the nature of the dark energy that drives the acceleration is unknown, it is still possible that it might eventually reverse sign and cause a rapid collapse.[1]
In Fiction
In The Hitchhikers Guide to the Galaxy book series, a cosmic crunch is revealed to the the eventual fate of the universe when, while dining in a restaurant situated at the end of time, the main character, Arthur is pulled from his dinner where the end of the universe is the show, and says to his friend Ford Prefect who is pulling him away, "But I want to see it happen!" to which Ford responds, "I've seen it. It's just a Gnab Gib."
See also
External links
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