Exploring the multiverse

Many cosmologists believe that our universe is just one within a wider ‘multiverse’. Many complex types of multiverse are possible – for instance, a theory called eternal inflation argues that just as our universe arose from one tiny region within the original Big Bang and was then blown up by a sudden event called inflation, the raw material of the Big Bang is still out there, giving rise to new universes with the potential for very different physical parameters to ours.

Another is closer to science fiction’s ‘parallel’ universes, and is rooted in quantum mechanics, the bizarre branch of physics that governs particles on a subatomic scale, within which events always carry a degree of uncertainty. There are many ways of handling this uncertainty, but according to one unusual idea, the ‘manyworlds interpretation’, every possible outcome of a quantum event occurs, but each one happens in its own distinct universe. In this sense, ours may be just one among a truly infinite number within which things happen to have played out a certain way.