Unless you’ve been living in a parallel dimension, you’ve probably noticed the idea of the multiverse is so hot right now.
The latest Doctor Strange movie is the most obvious example, with the concept getting an explicit shout-out in its title (Multiverse of Madness), but it’s become more and more common across the Marvel Cinematic Universe (including in the first Doctor Strange movie) in recent times.
Last year’s Spiderman: No Way Home deployed the multiverse concept as a way to unite three big-name actors who had played the character on the big screen, with Tobey Maguire and Andrew Garfield teaming up with Tom Holland to save the world.
But the Marvel machine doesn’t have a monopoly on the idea that there are multiple universes in which other versions of ourselves might lead lives that are both similar to and distinct from our own.
This year’s indie hit Everything Everywhere All At Once mines the concept for laughs, action and genuine philosophical probing. The French art-house film Little mom borrows from the concept without fanfare or explanation in a gentle story about two young girls who meet in a forest and discover they have an uncommon bond. The Apple TV+ crime thriller The Shining Girls doesn’t mention it once across its eight episodes, but the idea of a multiplicity of selves following different paths to different outcomes inhabits its every frame.
“We’re certainly having a moment right now,” says Tom Taylor, a Melbourne-based comic-book writer who has worked extensively for Marvel and DC, and whose animated series The Deep has just notched its fourth season on Netflix. “People really respond because anything can happen, the storytelling has so many possibilities.”
In a typical Marvel movie, he says, you know the superhero will be OK in the end. “But in a multiverse story you never know what to expect. The character trajectories are endless and unexpected. We’re taken out of our comfort zone by a multiverse, and that’s exciting for an audience and for a writer.”
At its most basic level, says Geraint Lewis, professor of astrophysics at the University of Sydney, the idea is simply “that our universe is just one space in this larger space, which we call the multiverse”.
In this simple model, the other universes operate exactly like ours: light travels at the same speed, gravity behaves the same way, atoms bond in the way they do in our universe. But there are also competing theories of the multiverse, including a belief that those other universes might be governed by laws of physics that are not the same as those that apply in ours.
Lewis says that in one iteration of this theory there could be an infinite number of universes, most of them sterile places incapable of supporting life. “We don’t have any robust evidence of this,” he adds, but it does serve a useful function in theoretical physics. “It helps explain why our universe has the characteristics it does. Without it, we’re left with questions that have us scratching our head.”
In effect, the idea of a multiverse not governed by a uniform set of physical laws allows for a scientific solution to the biggest puzzle of all. “If there is not a multiverse we are left with the question of why this universe was created with the laws of physics that allow for life to exist,” Lewis says. The multiverse, in essence, presents as “a scientific alternative to the God question”.
Tamara Davis, professor of astrophysics at the University of Queensland, says the idea that there is more than one universe is “pretty widely accepted” among scientists these days. The possibility that those universes may be governed by different laws to ours also inhabits “a reasonably solid plane of belief, even though we don’t know and can’t prove if it does or does not exist”.
Where science and science-fiction (or speculative fiction) part ways, says Davis, is in the realm of parallel worlds, the idea that “the same event, the same person, but with slight variations, can exist in different worlds”.
This is the stuff we’re seeing play out on our screens right now, and it owes much to what Davis calls “one of the logical but wild extrapolations of quantum physics – that anything that could have happened has happened.
“The many-worlds theory says any time there’s a 50-50 chance of anything and there is a bifurcation, both outcomes did occur, and you just found yourself on one of those paths, but an alternative you continued on the other path.”
Everything Everywhere All At Once is a perfect example of this on screen, with its heroine Evelyn (Michelle Yeoh) tapping into the many lives she has lived in other universes in order to overcome a force that threatens to destroy her own.
But while it’s useful for storytelling, Davis says this conception of the multiverse is not especially popular among scientists. “It’s an extremely wasteful theory because every interaction an atom has with another atom creates an entirely different universe.”
Ultimately, what underpins the idea of the multiverse is mathematics as much as science. It depends, says Lewis, on a model that “churns out infinite universes and somewhere the conditions for life eventually emerge. It’s a game of chance – like the idea that lots of monkeys bashing away at keyboards will ultimately produce the works of Shakespeare. In theory it could, but it takes a lot of monkeys, and a lot of keyboards.”
But how are we supposed to get from one universe to another? Typically, the answer is a wormhole, portal, incursion, or some other mechanism that brings the ostensibly parallel existences into proximity.
Is there any support for this notion in science? Well, yes and no.
“Wormholes between universes are hypothetical structures, so they are a possibility,” says Lewis. It is possible to devise mathematical models that support the notion that wormholes could exist within the general theory of relativity, but to make the models work “we need ‘exotic’ matter to curve and bend spacetime … and we simply don’t know if we can find and engineer such exotic matter into the correct concentration and distribution to make a wormhole a theoretical reality.”
In other words, he concludes, “they might exist in the mathematics, but not physically exist in the universe”.
So, how much of this fictional version of the multiverse is supported by the science?
“Science?” asks Tom Taylor quizzically. “We fake a lot of things, but you try to get the science close enough.”
He has called on friends with specialist knowledge – “engineers and, literally, a rocket scientist” – to work out if a proposed plot point in one of his comic books to rob the planet of electricity made sense (it did, more or less) , but in the end the multiverse, on screen and off, is rather more fiction than science.
“Multiverse theory is a theory,” Taylor says. “You can explore it, it’s fun to hypothesize and extrapolate. But I’m just there for the ride.”
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