A single explosion may not be the universe’s origin story anymore. A growing body of theoretical work suggests that the Big Bang could mark only the latest phase in a repeating cycle of expansion, collapse and rebirth, a framework known as cyclic cosmology or the Big Bounce scenario.
In these models, space first expands, then slows, reverses and contracts into an ultra-dense state that precedes a new burst of expansion. Instead of a singular beginning, the cosmos moves through recurring epochs, with each contraction potentially smoothing out irregularities and diluting accumulated entropy, the thermodynamic measure of disorder that usually points time in a single direction.
To make such cycles mathematically viable, physicists modify general relativity with exotic fields or quantum gravity effects that prevent a final catastrophic crunch. Some proposals invoke a bounce driven by negative pressure components in spacetime, while others use loop quantum cosmology to replace the classical singularity with a finite, high-curvature regime.
The idea competes with the standard inflationary picture, which explains the observable universe’s remarkable uniformity through a brief burst of accelerated expansion. Cyclic models must reproduce the same precise spectrum of density fluctuations in the cosmic microwave background and offer testable predictions that go beyond inflation’s successes. For now, the observable sky remains a sparse archive from which to infer whether this universe is a first draft or only the latest turn in a much older cycle.
