Have you ever wondered if there is another you somewhere in the universe? How about an infinite number of people like you, whose lives are almost exactly like yours – or what your life could have been, if you had done this thing differently?
Welcome to the multiverse, often imagined as a collection of parallel universes filled with replicas of us.
Scientists have been debating the idea of the multiverse for nearly 70 years, long before Hollywood began connecting universes through magical portals.
The concept is at the heart of some of this year’s highest-profile films, including the sci-fi adventure Everything everywhere all at onceand the new Marvel superhero movie, Doctor Strange in the Multiverse of Madness.
As far-fetched as these big-screen depictions may be, the question of whether the multiverse exists — and if so, in what form — continues to polarize scientists.
Possible, or science fiction?
As Doctor Strange himself says in the upcoming film: “The Multiverse is a concept we know awfully little about.”
While some scientists think it’s possible on some level, others say the idea is pure science fiction.
“Here’s the thing with the multiverse: it makes for a great story…but at this point there’s no evidence,” said Adam Frank, professor of astrophysics at the University of Rochester in New York.
Franc, despite his skepticism, helped shape this story on the big screen. He was scientific consultant for the 2016 edition strange doctor film in which the Marvel Cinematic Universe first explored the concept of the multiverse, beyond the pages of its comic books.
In this role, Frank offered advice on how physics and philosophy could mingle with the mind-bending magic of the film. The key, he says, isn’t scientific precision — it’s that the Marvel Multiverse has its own set of rules that it sticks to.
“I don’t mind if my science fiction plays with ideas that are a bit whimsical or even wrong. Their job is to tell me a good story,” Frank told CBC News.
WATCH | Doctor Strange (2016) explores the multiverse:
Scientists, on the other hand, need evidence—which they currently don’t have, he says, for the existence of the multiverse.
“It’s so far from any part of experimentally validated science.”
The many theories of the multiverse
The idea of the multiverse is rooted not only in physics and astronomy, but also in philosophy, with ancient greek philosophers contemplating the idea of infinite worlds.
The modern pop culture fantasy about the multiverse stems from American physicist Hugh Everett’s “many worlds” theory, who in the 1950s proposed that each action causes the universe to split into several different versions of itself — one for each possible result of the action.
“What would have happened if that car accident hadn’t happened, or if something else had happened? explains Professor Katie Mack, a theoretical astrophysicist at North Carolina State University. She describes Everett’s theory as “very appealing” to us as humans.
“The idea that just because bad luck has happened to us in our past doesn’t mean that every version of us in every possible universe has had that… It’s unclear to what extent physics supports any of these ideas, but it’s still an exciting thing to think about.”
Of many proposed forms the multiverse could takeEverett’s “many worlds” are among the fanciest.
Another theory suggests that when the Big Bang happened about 13.8 billion years ago, it could have created other universes, or “bubbles”, which could collide with our own.
Matthew Johnson, assistant professor of physics at York University and associate faculty member at the Perimeter Institute for Theoretical Physics, has examined this theory at length.
About a decade ago, he and a group of colleagues set out in search of scientific evidence, only to return empty-handed.
“You could actually go out and search the skies for evidence that we’re living in one of these bubbles and it’s collided with another one. And we went out and we looked for that, and we didn’t. haven’t found,” Johnson mentioned.
“The sad thing is that we’re probably not going to put together new experimental evidence that will do much better than what we already have.”
The late astrophysicist Stephen Hawking took a different approach in his final research work in 2018, in which he and co-author Thomas Hertog proposed a new mathematical framework that theorized a finite, rather than infinite, number of other universes.
Hawking previously said he was “never a fan of the multiverse” due to the inability to test theories about it. He never had the opportunity to further test his own theory, dying days after submitting the paper, although Hertog said he planned to continue his research.
A universe so big it must contain duplicates
Another theory has broader, though far from universal, support among scientists: the idea that the universe is so huge and that there are only a limited number of possible configurations, so at at some point, there must be duplicates.
“The universe would have to be really, really, really, really big for that to happen — and that’s envisioned in some pretty outlandish theories,” Johnson said.
The idea was explored, much to the delight of Spider Man fans, when three Peter Parkers – played by Tobey Maguire, Andrew Garfield and Tom Holland – crossed paths last year Spider-Man: No Coming Home.
Unfortunately for real-life earthlings, arranging an encounter with multiverse versions of ourselves is (currently, at least) scientifically impossible.
“We don’t know how to create a traversable wormhole, which is a wormhole that you could walk into and then go somewhere and come out of,” Johnson said.
He adds that it would be extremely dangerous for life to imitate the art while attempting to cross the multiverse.
“Usually what happens is the wormholes collapse into a singularity and then it’s game over.”