For decades, the dominant narrative of our universe has been one of a singular beginning and an inevitable, cold end. We are told the cosmos began with the Big Bang and will eventually dissipate into a state of maximum entropy. Yet, there remains a persistent, more rhythmic alternative: cyclic cosmology. This "Big Bounce" hypothesis suggests that the universe does not simply vanish, but rather collapses back in on itself before triggering a new expansion.
The theory has historically struggled to gain mainstream traction. Critics pointed to the second law of thermodynamics, arguing that entropy would accumulate with each cycle, eventually making a "bounce" impossible. Furthermore, the discovery of dark energy and the accelerating expansion of the universe seemed to suggest a one-way trip toward the void, leaving little room for a cosmic crunch.
However, theoretical physics is rarely settled. New models are emerging that attempt to reconcile a cyclic history with our current observations, treating the Big Bang not as a definitive starting point but as a transition phase. There is a poetic symmetry in the fact that the theory of cosmic cycles is itself experiencing a resurgence, proving that in physics, as in the stars, old ideas have a habit of returning to the light.
With reporting from New Scientist.
Source · New Scientist
