A Closed Universe
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STScI
The Big Crunch
If there is enough matter in the Universe eventually gravitational
forces will stop its expansion. When this happens gravity will cause
the universe to reverse its direction and begin to collapse under its
own weight. This phase of the Universe's life is known as the Big
Crunch.
Eventually all of the matter in the Universe will collapse into a super dense state and possibly even collapse into an unimaginably massive black hole. Some theorize that the Universe could collapse into the same state that it began as and then blow up in another Big Bang. In this way the Universe would last forever but would continually go through these phases of expansion and contraction, Big Bang and Big Crunch and so on...
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