Scientists Search the Big Bang’s Afterglow for Signs of Colliding Parallel Universes

Some researchers now suggest our universe might be just one bubble in an infinite multiverse. This idea has moved from science fiction to serious theory: cosmic inflation and quantum physics allow scenarios of many universes. If true, it could explain why nature's constants seem so finely tuned, we would exist in one of the rare life-friendly bubbles. Scientists are searching for any signature of other universes, though evidence remains elusive.

Cosmic inflation and bubble universes

According to newsletters, the inflation, ultra-fast growth after the Big Bang, may create a series of bubble-like universes. The inflation will never stop, in this model; rather, each region that ends its inflation will form a new, individual cosmos, called a bubble. The number of new, distinct worlds that exist in this fashion could be infinite, each of them possibly having its unique laws of physics (electrons might, for example, be heavier in another cosmos).

This model might account for fine-tuning of various cosmic parameters by postulating that we happen to call home a relatively seldom fine-tuned cosmos, a part of a larger bubble ensemble. Scientists do look for signs of bubble collisions, imprinted in cosmic microwave background radiation; so far, none have been detected.

Quantum worlds and testing

A second idea is the quantum "Many-Worlds" interpretation. Here, every quantum event with multiple outcomes gives rise to branching realities. As a result, there would be countless parallel universes in which all possible histories occur. According to one physicist, these versions “never will know about each other”, making the idea essentially untestable.

Indeed, by definition, other universes would lie forever beyond our observational reach, and critics warn that without testable predictions the multiverse may stray into metaphysics.