When the Marvel Cinematic Universe began playing with the notion of a multiverse, many of us were excited about the possibilities it opens up for the franchise. Just as many of us were a bit like, wait, what? If you’re a comic book fan, you will have already known about the role it plays in those well-thumbed pages. Just as the introduction of the concept of the multiverse was a convenient way of tying together continuities, stories, and characters on the pages of disparate publications and comic series, it also, of course, presents the same opportunity for the screen.
But more than that, welcoming in the multiverse spoils audiences in terms of storytelling and moving the franchise forward apace. We’ve all only recently had our brains boggled by the appearance of multiple versions of Loki from across parallel universes in his self-title Disney+ series, as well as the handful of Spider-Mans (Men?) that cropped up in Spider-Man: No Way Home. Not to mention the small (read subatomic) matter of the Quantum Realm — first introduced in Ant-Man and since expanded upon in other films — and the implications of that. Minds. Blown.
The thing is, though, the idea of the existence of a multiverse isn’t as far-fetched as you might think. In fact, it isn’t far-fetched at all. Which takes the MCU out of the realms of pure ridiculous-but-fun fantasy fare and into the area of science-fiction proper. Or science-fantasy fiction at any rate. Prominent physicists have been theorizing about the multiverse for donkey’s years and we’re closer than ever to proving its actuality. Indeed, plenty of major science brains are already convinced it’s real. It’s an extension of our knowledge of quantum mechanics and how the universe as we know it behaves and came to be.
The science within the MCU explaining what’s going on also has a good grounding in real-life physics, too. Well, some of it anyway. Following the release of Doctor Strange in the Multiverse of Madness, in which the titular sorcerer goes multiversal travelling in an effort to save his new companion-from-another-universe, America Chavez, we tracked down our own universe’s John Gribbin – prominent astrophysicist, science and science-fiction writer, and author of the book In Search of the Multiverse – to discuss multiversal theory and the science of the MCU. Prepare for some earth-shattering revelations.
There’s a Jane Austen Universe — But no Sentient Paint-Splash Universe
Let’s start from the point of accepting that the multiverse is a very real and sound theory in physics. Experiments that suggest its existence have been carried out, and important brains have theorized across the years about how multiple universes might have formed and what the associated characteristics are. Essentially, most are agreed that if it exists, then all possibilities exist, meaning that there are alternate versions within it of you and me. Some of these universes will be almost identical to our own; others vastly different.
So, with that in mind, we’ll jump in by looking first at the latest instalment in the MCU, Doctor Strange in the Multiverse of Madness — since that’s the film we’re all currently focused on.
In the movie, we’re swept along with Strange and Chavez through a string of alternate universes, some of which look like the main MCU universe as we know it – given the name Earth-616 in the film – and some of which look very different, seemingly in defiance of the laws of physics as we know them. There’s a universe in which everything is two-dimensional and cartoon-like; a universe where people and everything are made up of cubes, or blocks; and a universe filled with paint splotches sentient and otherwise, in which, according to Chavez in the film, it’s really difficult to eat anything.
If, in the multiverse, anything is possible, and some universes could have different balances of properties to ours, could these imagined worlds exist?
“Well,” says Gribbin, “the ones that are similar to ours [could]. Now, there are serious problems with things in two dimensions. Especially if you’re going to have living things because if you have a living thing, it would have to be a circle of some kind, and if it was going to try to eat anything, it would have to pop open and things would fall out. Things like everything being cubes, or everything being two-dimensional, I don’t think you could imagine that to work. The rule of thumb is that anything that’s allowed by the laws of physics is possible. There are serious scientists, in particular, David Deutsch, who is a top brain at Oxford, who says that, yes, the multiverse is real, and that anything that’s physically possible exists in some universe.
“So, in terms of fiction, there really is a Jane Austen universe where all the things that happen in Jane Austen [novels] really happen, because they’re all physically possible. But he would say there is not a Superman universe, because what Superman does is against the laws of physics, and so that’s not possible. And so somewhere between those areas, there’s the question of things that we think are impossible, but maybe they are possible — time travel, or levitation, or whatever.”
Pym Particle Science
There are plenty of “top brains” who do believe time travel could be possible – it’s just a question of proving it. And we certainly don’t know everything yet about quantum physics and the universe, let alone multiverse, so there’s plenty more to discover. Indeed, when the Higgs particle was discovered in 2012, it was a breakthrough, adding a hugely important missing piece to the scientific puzzle that is known as the standard model of physics – though Gribbin does say there are still some “tiny, tiny differences that aren’t quite right”.
But just as the Higgs boson affects the mass of other particles when it interacts with them, so does Ant-Man’s Pym Particle – a (fictional) discovery by Hank Pym in the MCU who harnessed its properties to alter the size and mass of objects and living beings. How accurate is this, according to the scientific knowledge we have today?
“That’s not completely bonkers,” says Gribbin. WTAF. “One of the most important discoveries ever in physics, [found] in the past 10 years or so, is the Higgs particle. And this is a manifestation of a quantum field. Like light is a field and photons are the particles of the light, of the electromagnetic field. There’s thought to be this field called the Higgs field which sort of fills the whole universe. And the particle that corresponds to that is the Higgs boson or Higgs particle. And this particle is what gives other particles mass. You can think of it as an electron or something sort of ‘swallows’ the Higgs particle. And that’s why an electron has got the mass it has — it’s to do with how it interacts with the field.
“So if you were inventing a way to change mass, the new particle you come up with would be a new kind of Higgs particle. And so it would give things different mass. If you could create a field that was like the Higgs field, but produced a particle with a different mass to the Higgs particle, then that would interact with your electrons and protons and atoms, and give them different mass. So that’s one of the better, really good, scientific excuses for what’s going on [in these movies] in a seemingly impossible way. It’s better than, you know, a shrinking ray that you just shoot and they get smaller.”
Andrew Garfield and String Theory
One of the theories that exists about the multiverse says that because of the way particles like electrons and photons, which are found within atoms, behave, all possibilities exist. Experiments have shown that when presented with a choice, these subatomic particles take all options – it’s only us observing them that seems to ‘force’ them into one state or another.
In Spider-Man: No Way Home, Andrew Garfield’s Peter Parker remarks on discovering that he’s been transported to another universe that it proves String Theory correct. Now, String Theory is the idea that the smallest ‘building block’ of reality is not an atom, an electron, or a quark, but a ‘string’, or rubber band-type thing, that vibrates and interacts with other strings. What does Gribbin make of this assertion?
“I think where they’re coming from is that one of the aspects of string theory is that there is a kind of multiverse where there’s a plane of possibilities. All the dimensions, and [all] possibilities exist,” says Gribbin. “There’s a cosmic landscape, and all the possibilities exist in the landscape. So, in terms of having them interact with each other, some would be close by, like two cities near each other, and some will be far away across the ocean in the cosmic landscape. And so you could imagine that the universe of one set of Spider-Man characters and the universe of another set of Spider-Man characters are both in the cosmic landscape and that somehow, one lot of them has travelled across the landscape and to the other place. That is very, very loosely fitting in with String Theory. It doesn’t prove that String Theory is correct, but for entertainment purposes, in a movie, it’s a good line and it’s not that far wrong.”
The Gap Junction
Okay, so going back to Multiverse of Madness then and this idea of the Gap Junction. According to the movie, this is the space that exists between universes which Strange and other characters are able to visit. Is there any kind of theory about a similar space existing in physics? Perhaps not one with doorways and hidden magic books and so on…
“There are things that sort of touch on it,” says Gribbin. “I’m reminded of the His Dark Materials trilogy, where there’s the Subtle Knife that can cut holes in the fabric of space and get through from one universe to another, and there you kind of have this idea of a gap. When I was writing about the science in the Dark Materials stories, and of course, in real science, [I touched on the fact that] we have this idea that there’s the smallest possible distance in quantum physics, so that just as things are made of atoms, that space itself is made of kind of bits of space.”
Gribbin says that you can imagine that there would be a gap of sorts between bits of space. “And if there is a universe like ours, in particular, that would be in some sense ‘next door’ — that’s the expression that people usually use — in order to get from our universe to the universe next door, that there could be a quantum-sized gap in between. Once you start thinking about that, then you say, ‘Well, you know, if you’re talking about people who can be flattened two-dimensional, they could squeeze into the gap. And so, it opens up this whole sort of can of ideas, I guess, rather than a can of worms.”
Quantum Tunnel = Wormhole?
Another theory about the multiverse is that alternate universes are created by and situated within black holes. In his book, Gribbin writes about thinking of space like the curved surface of a balloon, and then imagining little blisters forming in the surface of that balloon. The ‘tether’ that keeps the blister attached to the surface is the wormhole, its mouth the black hole. The wormhole is the gateway to the new ‘baby universe’. Is this a bit like the MCU’s quantum tunnel, which they enter in order to cross into the quantum realm and access alternate timelines?
“That’s really very sound physics going by the standards of these kinds of stories,” says Gribbin. “It’s a serious idea that our universe is connected to other universes as, in effect, bubbles which are joined on through wormholes that you can think of as being black holes in our universe, and that, equally, our universe was formed from a black hole collapsing in another one.”
Gribbin recommends a novel called Cosm by Gregory Benford as a scientifically sound story that explores this if you’re keen for further reading.
“He’s got particle physicists working in a lab like the one at CERN, or somewhere like that. And they do an experiment, and they make a tiny, tiny quantum black hole. And then, through some various trickery, they’re able to look through this tiny quantum black hole. On the other side, there is a separate universe. [Benford] is a proper physicist himself. So all of that idea of the quantum realm, and connecting with wormholes, is very much right on the edge of mainstream real physics. Just over the edge, maybe. Close to the edge.”
Branched Timelines
Visiting the Quantum Realm was critical to the Avengers’ plan to enable them to travel back in time. We think of time as linear, with a past comprised of events that have happened and which are now memories and a future that is yet to happen. But quantum physics theorists posit that time, as a dimension like the dimensions of space, could exist all at once – just as, for example, New Zealand exists spatially like London, even though we are not in it and not experiencing it.
In Avengers: Endgame, we saw the heroes visit specific past points in the timeline in order to enact the one in 14,000,605 eventualities foreseen by Doctor Strange in which they defeat Thanos. As they put their plan into action, the act of visiting the past created new timelines, or universes – one of which branched off into the Disney+ series Loki, which we’ll get to shortly. So this idea of branched timelines… does that hold much sway in the physics world?
“The oldest idea, I think, in science fiction for alternate universes is this idea of branching off and that if you go back and try to change history, you can’t, because otherwise you wouldn’t exist,” says Gribbin. “The idea is very soundly established in science fiction that if you go back in the past, and you change the past, you’re creating another universe. And then when you go forward in time, you’ll find you’re in a universe where you were never born, or whatever. But that doesn’t matter, because you were born in the other one, and slid down and back up the other side. In your universe, you have just disappeared.
“This is closely related to an idea that all the alternative universes exist, and they’re all the same up to a certain point. Then, one of them changes, or many of them change, and you get a variety. I used to have great trouble explaining this to people in terms of fungibility. But now everybody knows fungible tokens. So the idea is that [for] every possible quantum universe that things are going on like in our universe, there’s all the possible universes sort of side by side exactly the same. So, they’re fungible. And then at some point, something happens in one universe. And it then becomes distinct from all the others. So it carries on.”
Gribbin explains that it would therefore look like branching – but it isn’t really. Think about Schrödinger’s Cat.
“People talk about the Schrödinger’s Cat experiment where this cat is shut in a room and either dies, or it doesn’t die. And usually, if people talk about this as at the moment where the cat either dies [or lives], the two universes split apart. What is a much better way of thinking of it is that there’s always two universes with two cats. And in one of the universes, the cat dies, and in the other one, it lives. So if you actually do the experiment, and you open the door to look and see if the cat’s alive, you’re not actually splitting the universe, all you are doing is finding out which one you personally are living in.”
Gribbin continues, “I think that relates to a lot of these ideas; that all the possibilities are out there. And when we think we’re changing them – we, or the characters in the story, or whatever — all that’s really happening is that you’re selecting which one you’re in. And that gets around a lot of problems, like, the basic one: E equals MC squared. If you’re splitting a universe, you’ve got a lot of energy involved in making a lot of mass — even to make one copy of one person. So if you’re not actually splitting anything, you’re not making a new universe. That’s a lot easier to handle.”
Is Doctor Strange Basically a Quantum Computer?
Got it. We think. But let’s go back to Doctor Strange for a moment and that moment when he sorts through all the possible outcomes of the battle against Thanos. Would Gribbin say that’s the sorcerer’s brain acting almost like a quantum computer recording data from alternate universes? Wait a minute: rewind. What is a quantum computer exactly? Well, if all these fungible universes were splitting, a quantum computer would be able to gather the data that proves it.
“You could, in principle, develop a quantum computer, which is one that operates on quantum principles,” says Gribbin. “So it is actually sort of thinks, if you made it intelligent, in a different way from what we would think. The idea is that you could have an experiment where the computer was doing something involving something like an electron that goes two ways through an experiment, okay? [For a more detailed explanation of this experiment, check out Gribbin’s book, In Search of the Multiverse] Does it go through ‘A’? Or does it go through ‘B’? Some versions of quantum theory say that it does both simultaneously, and then it comes back on the other side and turns back into one electron. If you had a quantum computer that was doing the experiment inside itself, so to speak, then you could come up to the experiment, the computer would do the experiment, and you come out the other side, and you could ask it, ‘Did you feel yourself splitting into two?’”
If there is a multiverse, the computer would tell you that it felt itself split in two, which, says Gribbin, you could interpret as being two parallel universes interacting with each other.
“Looking down the line, the way things are going with quantum computing, in ten years, maybe, people will be able to do that experiment. And … if you’re doing an experiment, what it really means is that there’s all these — I don’t really like the term, but it’s the one that’s used –‘parallel universes’ very similar to one another. And you’d have to imagine that in all these universes, there are scientists either identical to us or very similar to us doing the same experiment with their own quantum computer. And all the quantum computers are saying on the other side to their own scientists, ‘I felt myself splitting in two,’ well, then the next stage is to try and get the quantum computers to talk to each other, and pass information to the universe next door.”
Doctor Strange’s magical mental processing is “an extreme version” of this, suggests Gribbin.
Alligator Loki
Speaking of brains, as we have been, leads us to the concept of alternate selves. Starting with Loki, which explored this idea in some depth, Gribbin says there’s every possibility that there’s a universe in which our roles are reversed – in which he’s the curious Film and TV journalist and I’m the physics expert. But what I want to know is whether it would be possible for an alligator version of myself to exist in another universe, just like Loki’s scaly counterpart.
“I would be inclined to say not in terms of physics and biology and so on,” says Gribbin, carefully selecting language so as to never completely rule anything out, it seems. “At least it sounds like it’s a living, breathing animal, which is more plausible than being a two-dimensional cartoon-type character. So I think we’ll put that in the realms of fantasy. But enjoyable fantasy.”
Glad he’s qualified that – because nothing pleased me more about the Loki series than Alligator Loki. Though Gribbin has all but dismissed the concept as scientifically possible, having read his book in which the physicist broaches a theory in which the multiverse was made by a, or plural, advanced beings, he also offers this as an explanation for the concept of a god or gods. Which in turn made me think of some cultures’ belief in reincarnation, and the possibility of being reincarnated as animals. If the concept of a god can be explained by science, then perhaps reincarnation as an animal can be too.
Multiverse of Madness: Dreams and Dreamwalking
But let’s move on. Back to Multiverse of Madness, if you please. In that film, we learn that dreaming is considered a window into the lives of our alternate selves. Strange and Scarlet Witch are also able, using the powers of the Darkhold, to ‘dreamwalk’, transporting their consciousnesses into the bodies of their alternate selves in alternate universes. Is there any theory around the possibility of communicating with our alternate selves in the multiverse in real life?
“This is a very old idea again in — I don’t know if you’d call it philosophy, or science, or whatever — that what we dream about could be real in some way,” says Gribbin. “It’s something that people speculate about, but there is no hard scientific evidence. But if you imagine that there is a universe that’s just like ours, except that I’m interviewing you, and you’re the one who knows all about the multiverse, our counterparts would be very similar. And it’s suggested, in some sense, in tune with one another. And this does relate to ideas in quantum physics, like entanglement.”
Entanglement?
“It’s proven science that when two things interact at the atomic level — things like electrons or photons — once they’ve interacted, they then split far, far apart. Somehow, they’re still in touch with each other; they’re entangled. And what happens to one of them, even if it’s on the other side of the universe, will affect what’s happening to the one that’s here. And so they’re now part of the same thing, as it were. So you can think that if you’re going to accept the reality of the multiverse, and that there are copies — for want of a better word — of you and me, then our copies would be entangled with us. And that our experiences, especially in things like dreams [could be linked to this idea]. I’ve not seen any evidence for genuine precognition and things like that, but if you did have evidence for precognition that could be linked to this as well. They’re way out on a limb; they’re sort of leftfield ideas but they’re not completely bonkers.”
A Good Way to Think About the Multiverse
Finally, where does John Gribbin himself sit in the great multiverse debate? Is there a theory he believes more readily than others?
“I am always wary about that word ‘belief’,” says Gribbin, speaking like a true scientist. “You’re always ready for something new to come along and change things. But my favorite [explanation] is a bit off the wall, even compared with some of [the events in the MCU we’ve discussed today], but there is an idea that every possible quantum state of everything exists. And that each bit is like a time capsule, which has got memories of the past and doesn’t know anything about the future. And so that what we think of us as ourselves having a continuous lifetime is actually a load of quantum states. And in each quantum state, there’s a memory of all the other quantum states that are numbered, lower down, and there’s no memory of the ones that are further up.”
He explains further, “The analogy is like with a book. If you took a book and you tore out all the pages and threw them up in the air, so they landed at random, every page would have some information about the earlier numbered pages, and then there’d be a numbered sequence but they would no longer be in a book, they would just exist.”
Gribbin says this is the idea that he finds most fun. “I think it solves a lot of problems like the big one, what is time? Why do we perceive time moving? When, if it is another dimension, why? Why don’t we see it in the same way as other dimensions? So that’s a fairly extreme physicist’s idea of how things might be. But I do feel that there should be more than one universe; that the multiverse ideas [have weight] and as [Andrew Garfield’s Spider-Man] says, string theory predicts it. Some kind of multiverse I think is likely. More likely than not.”
If, like us, your mind is also blown by the contents of this article, and you want to learn more about the multiverse and its theories in real life, read John Gribbin’s book In Search of the Multiverse.
John Gribbin is a Senior Research Fellow in Astronomy at the University of Sussex in the UK and has taught the course, Our Place in the Cosmos. He writes books for a living.
From the website of the University of Sussex: One of the first students at Sussex, John also studied in Cambridge and has worked on the journals Nature and New Scientist. From 1975 to 1978 he was a member of the Science Policy Research Unit. He now writes books about science, and is best known for In Search of Schrödinger’s Cat. His book, Computing With Quantum Cats, provides the background to work on quantum computing, in which Sussex is a world leader.
For more from John Gribbin, check out his website.
Check out our interview with Danny Elfman, composer of the Doctor Strange in the Multiverse of Madness score, below.
