Are there an infinite number of parallel universes? Or do we exist within one of a finite number, where things are quite similar to our own?
That’s the question at the heart of a paper published last week in the Journal of High Energy Physics, as a collaboration between Stephen Hawking (before his death in March) and Belgian physicist Thomas Hertog. So what’s it say? From the abstract:
“…we conjecture that the exit from eternal inflation does not produce an infinite fractal-like multiverse, but is finite and reasonably smooth.”
The paper is actually a continuation, or perhaps a rebuttal, of a previous work by Hawking called the No-Boundary Proposal, which suggested the multiverse was like a fractal – infinite, and therefore housing infinite parallel universes. The problem, however, was that this theory of infinite possibilities could never be tested, or tell us much about our own universe, rendering it mostly pointless.
That’s why Hawking and Hertog set to work figuring out a model that could be tested, leading them to a potential multiverse with fewer parallel universes. A finite number.
In the above video, uploaded on April 29 by the European Research Council, Thomas Hertog discusses the theory, and how these things might be tested.
If you head over to read the new study itself, well, it’s all a bit complicated. According to LiveScience, the paper has been floating around in some form since July 2017, and actually uses something called a “toy model,” a kind of deliberately simplistic model (relatively speaking) used to study something without making things overly complicated, or to fill in gaps. In this case, that gap would be quantum gravity.
The study has its detractors, and the general idea of a smaller number of more predictable universes isn’t a new one, but it’s always interesting to hear scientists talk about the possibility of alternate worlds.
Knowing very little about the actual science behind them, myself (outside of science fiction and, say, John Titor), I’ve always been fond of the idea of a smaller number of parallel worlds rather than an infinite sea of constantly branching possibilities.
Something like the Many-worlds interpretation, in which each and every observation or decision creates an entirely new universe, has always seemed a bit messy to me.
But, hey, the universe can do what it wants.