Cyclic universe

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The cyclic universe was a theory that the universe existed in an infinite self-sustaining cycle of new universes which all began in Big Bangs resulting from the Big Crunches of the universe preceeding them. (PROSE: A Bell Ringing in an Empty Sky ^[+]Loading...["A Bell Ringing in an Empty Sky (short story)"])

The Seventh Doctor believed that his universe was part of such a cycle, with the Great Old Ones' universe being the universe which came before his. (PROSE: All-Consuming Fire ^[+]Loading...["All-Consuming Fire (novel)"]) However, one account suggested that the Time Lords' belief in a literal universe before their own was a misunderstanding of records of how the nature of their own universe had been fundamentally changed by the cross-temporal anchoring of the thread, with the denizens of the time before time being misconstrued as survivors of the "previous universe". (PROSE: Christmas on a Rational Planet ^[+]Loading...["Christmas on a Rational Planet (novel)"])

By one account, this model was unrealistic due to entropy. (PROSE: A Bell Ringing in an Empty Sky ^[+]Loading...["A Bell Ringing in an Empty Sky (short story)"])

A similar concept was the cycle of universal regeneration, which occurred on a different scale to universal lifetimes. (PROSE: The Coming of the Terraphiles ^[+]Loading...["The Coming of the Terraphiles (novel)"])