Some theorists propose that the universe expands and contracts in endless cycles.
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It's an appealing concept because it removes the need for a state called a singularity that corresponds to "beginning of time" in other models.
It's an appealing concept because it removes the need for a state called a singularity that corresponds to "beginning of time" in other models.
The research shows that the latest version of this theory introduces a new problem.
Cyclic universes described under this model must have a beginning.
The epic story of cosmic inflation is a competing theory about the origins of the universe.
Under this model, the early universe was characterized by a period of rapid expansion from a singularity, followed by the superhot Big Bang.
This forged the primordial elements that went on to make galaxies and stars and planets, and the atoms in our bodies and all other living things.
Cosmic inflation focuses on what happens during and after the age of rapid expansion and doesn't explain what came before that.
A truly cyclic universe would circumvent these problems, so, these bouncing models raise their own array of untenable questions.