Big Crunch

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An animation of the supposed behaviour of a Big Crunch




The exact details of the events that would take place before the final collapse dependent on the length of both the expansion phase as well as the previous contraction phase; the longer both lasted, the more events expected to take place in an ever-expanding universe would happen; nonetheless it's expected that the contraction phase would not immediately be noticed by hypothetical observers because of the delay caused by the speed of light, that the temperature of the Cosmic microwave background would rise during contraction symmetrically compared to the previous expansion phase, and that the events that took place during the Big Bang would take in opposite order.[3] For a contracting Universe similar to ours in composition it's expected that superclusters would merge among themselves followed by galaxy clusters and later galaxies. By the time stars were so close together that collisions among them were frequent, the temperature of the cosmic microwave background would have increased so much that stars would be unable to expel their internal heat, slowly cooking until they exploded leaving behind a hot and highly heterogeneus gas, whose atoms would break down in their constituent subatomic particles because of the increasing temperature, that would be absorbed by the already coalescing black holes before the Big Crunch itself.[3]

The Hubble Constant measures the current state of expansion in the universe, and the strength of the gravitational force depends on the density and pressure of matter in the universe, or in other words, the critical density of the universe. If the density of the universe is greater than the critical density, then the strength of the gravitational force will stop the universe from expanding and the universe will collapse back on itself[2]—assuming that there is no repulsive force such as a cosmological constant. Conversely, if the density of the universe is less than the critical density, the universe will continue to expand and the gravitational pull will not be enough to stop the universe from expanding. This scenario would result in the Big Freeze, where the universe cools as it expands and reaches a state of entropy.[4] One theory proposes that the universe could collapse to the state where it began and then initiate another Big Bang,[2] so in this way the universe would last forever, but would pass through phases of expansion (Big Bang) and contraction (Big Crunch).[5] Another scenario results in a flat universe which occurs when the critical density is just right. In this state the universe would always be slowing down, and eventually come to a stop in an interminable amount of time. Although, it is now understood that the critical density has been measured and determined to be a flat universe.[6]


See also[edit]


  3. ^ a b Davies, Paul (January 9, 1997). The Last Three Minutes: Conjectures About The Ultimate Fate Of The Universe. Basic Books. ISBN 978-0-465-03851-0. 
  5. ^ Jennifer Bergman, The Big Crunch, Windows to the Universe (2003)
  6. ^ Fraser Cain (2013-10-17), How Will The Universe End?, retrieved 2016-06-13 
  8. ^ McSween, Stephen A. "Dark Energy and the Red Shift in a Contracting Universe." [1]