Pop Culture | Science
Everything Everywhere All at Once: The Science Behind the Multiverse
Please Feel Free to Blither Now…
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Everything Everywhere All at Once might not be the first movie about the multiverse ever made, but by now it has to count as the most critically successful one, with 264 awards, among them seven Oscars for Best Picture, Best Director, Best Actress, Best Supporting Actress, Best Supporting Actor, Best Screenplay, and Best Film Editing.
It really is a fantastic movie, and, amidst such a chaotic decade that seems to pivot on so many singular decisions and what-if questions, perhaps the multiverse’s time has come. The MCU has also tackled the concept, in a more muddled way that seems to reinvent itself with each entry (Loki is probably its most successful attempt so far), and Rick and Morty has taken what at first seemed to be a goofy parody of the multiverse and tied it into a more and more intricate philosophical knot with each season.
Before that, we had Jet Li’s The One, and the TV show Sliders, and Marvel’s assortment of Earths and the “Elseworlds” of DC, and Star Trek with its mirror universe, and, before any of them, Jorge Luis Borges’ classic 1941 short story “The Garden of Forking Paths,” which many consider to be the original multiverse story — although Murray Leinster’s “Sidewise in Time,” about an apocalyptic time crash that merges countless alternate timelines into a patchwork world, managed to beat it by just a few years.
To get an easy question out of the way first, how does Everything compare? I’d call it a Rick and Morty story without Rick or Morty, which is more of a compliment than it sounds. Some of the best R&M episodes are the ones that drag the rest of the family, Beth, Jerry, and Summer, into the duo’s universe-hopping exploits, and explore their strained relationships and reconciliations through that anarchic lens. EEAAO could easily be a story about those three characters having their own spinoff adventure, so if you like the idea of alternate timelines, absurdist comedy, and dysfunctional family drama, but can do without the abusive alcoholic mad scientist and his increasingly traumatized grandson, this is the movie for you.
But what is the multiverse? Is it time travel? Another dimension? A string of parallel universes? And does it have any merit in real life? It’s a concept so deeply embedded in science fiction these days, and so mixed up with other scientific ideas, that teasing out the core premise can be tricky. But what it really comes down to is how we look at the world around us.
The Whole Sort of General Mish Mash
The first step is untangling just what we actually mean when we talk about “the multiverse,” since there are all sorts of cosmological theories that describe something we could call a multiverse. We could talk about string vibrations, brane-worlds, Penrose diagrams, Einstein-Rosen bridges, and other physics models that predict a multitude of space-time structures. That rabbit hole’s not only very deep but very wide: choosing which ledge to jump over would take up a whole article in itself. But when stories like Everything Everywhere All at Once, Rick and Morty, or the MCU describe an infinite number of timelines that reflect all the different choices we made, what they’re describing is Hugh Everett’s many-worlds theory.
Quantum mechanics is weird. It’s accurate — our technology, from nuclear energy to transistors to experimental quantum computers, hinges on its fundamental principles — but it defies common sense. Nobel-prize-winning quantum physicist Richard Feynman once explained it this way:
“Do not keep saying to yourself, if you can possibly avoid it, ‘But how can it be like that?’ because you will get ‘down the drain’ into a blind alley from which nobody has yet escaped. Nobody knows how it can be like that.”
One of the strangest quantum concepts is “wavefunction collapse.” At the subatomic level, reality becomes a weather forecast. An electron in orbit around an atom has a very high probability of being in one spot, but a smaller probability of being somewhere else, a still smaller probability of being even further away, and so on. There’s a nonzero probability that it could be on the far side of the universe; the same goes for every particle and everything made of particles. Mass affects the calculations (a proton’s location is much more certain than an electron, and an atom more certain than a proton, and a human being even more) but the answer never stops being uncertain until the system’s measured by an observer, at which point all the probabilities “collapse” like scaffolding into one result.
Why does that happen? That would be one of those questions Feynman warned us about asking. The first answer scientists came up with was the “Copenhagen interpretation,” which is what’s been described: things are fuzzy until we look at them, and then they freeze into place. The dice roll around in a tumbler until we release them and get a result.
Everett’s many-worlds model offers another way of balancing the equations and talking about the universe. Its premise is that there really isn’t any “wavefunction collapse” at all. The system never truly loses its uncertainty; the universe is (say it with me) everything everywhere all at once, with an infinite multitude of ourselves riding the leading edge of each wavefront, blind to the rest, each one thinking it’s the “real” world. In a sense, the dice never get rolled: they’re just hanging in the air, and whether they say six or three or five depends on which angle we’re looking at them.
One of the best explanations of the many-worlds theory I’ve read comes from Douglas Adams’ Hitchhiker’s Guide to the Galaxy series. Here’s how Mostly Harmless describes the Whole Sort of General Mish Mash:
The first thing to realize about parallel universes, the Guide says, is they are not parallel.
It is also important to realize that they are not, strictly speaking, universes either, but it is easiest if you don’t try to realize that until a little later, after you’ve realized that everything you’ve realized up to that moment is not true.
The reason they are not universes is that any given universe is not actually a thing as such, but is just a way of looking at what is technically known as the WSOGMM, or Whole Sort of General Mish Mash. The Whole Sort of General Mish Mash doesn’t actually exist either, but is just the sum total of all the different ways there would be of looking at it if it did.
The reason they are not parallel is the same reason that the sea is not parallel. It doesn’t mean anything. You can slice the Whole Sort of General Mish Mash any way you like and you will generally come up with something that someone will call home.
Please feel free to blither now.
There’s an experiment in quantum physics, the double-slit experiment, which takes on dizzying implications with this model. The test itself is easy enough to set up and was originally done with visible light. Just take a coherent light source, put a screen with two parallel slits between it and a photosensitive plate, and switch the light on. You’ll see an interference pattern of light and dark bands on the screen. Photons has wave properties and those waves interfere with each other. Simple enough.
Replace the light with electrons, replace the photosensitive screen with a photoelectric sensor, and you get the same sort of interference pattern. Electrons also have wave properties — those weather-forecast probabilities we talked about before — and they interfere with each other. But, and here’s where it gets weird, that only happens if you don’t measure the electrons when they’re being fired at the slit. If you do measure them, the pattern vanishes and there are just two bull’s-eye marks, one for each slit.
So what’s going on when we don’t measure them and we see that pattern? The Copenhagen interpretation says their wavefunctions interfered with one another just like light, canceling each other out here and there, resulting in alternating probable and improbable locations on the screen. But the many-worlds interpretation says that those wavefunctions never collapse and what we’re seeing in the interference pattern is an overlap of all the electron’s possibilities, a cross-section of the multiverse. When we measure them and erase the interference pattern, what really happens is that we also split at that point: we can’t see the wave pattern anymore because now we’re part of it, smeared out along its length.
And that isn’t just happening by magic when we do that one specific test. It’s happening all the time, every moment, everything that could go this way or that, every decision that we make. We can’t see the interference pattern of our own lives because we’re inside that pattern, spread among all the nonzero possibilities that describe us. That’s the usual sci-fi idea of the multiverse in a nutshell: everything that could possibly exist does exist, complete with a version of us that exists within it. They aren’t “universes,” per se, just one universe that can be seen from countless angles.
Is there any way to detect these other lives, to turn them from a theoretical construct into a physical reality? Everett privately suggested one method to his friends, but he almost certainly never tried it himself, and I wouldn’t recommend it either. That method is known as quantum suicide.
Gaze Upon Quantum Immortality!
In an electron interference pattern, some of the probabilities cancel out to zero and others are magnified into near-certainty, creating the alternating dark and light bands. On a larger scale — say, a human life — that would mean some outcomes reach dead ends and others don’t. That makes sense. We’re alive in some timelines and nonexistent in others; either we’ve died or we were never born in the first place. But the electrons in the double-slit experiment aren’t just passively recording all the outcomes: the pattern comes from those outcomes interacting with each other. Can we interact with our alternate lives in the same way? Can we eliminate them?
In theory, according to Everett, maybe. But don’t try this trick at home.
Since every possible outcome is an actuality somewhere, that would also be true of life-or-death outcomes. Specifically, it would be true for a game of Russian Roulette, with a one-in-six chance of death. Load one bullet into the revolver chamber, spin it, pull the trigger. Crudely speaking, there is now one timeline where the bullet fired and five where it didn’t.
Spin it again, pull the trigger again. Once again, crudely speaking (the real math is very complicated and subject to a great deal of debate since it involves quantum calculations), there are five timelines where we lived and one where we died. Spin it again, pull the trigger again, and…
More and more timelines where we died would accumulate, but there would always be one timeline where the gun simply doesn’t fire, no matter how many times we try. It would never strictly be “impossible” that we’re still alive, just very, very improbable. But if we keep at it, then that one survivor timeline would have more and more evidence that there are other timelines out there, alternate selves who keep taking the bullet.
For a tongue-in-cheek but accurate and mind-bending demonstration of this thought experiment, check out “A Quantum Suicide,” an episode of the fictional TV show Night Springs from the video game Alan Wake…
As the YouTube comments were quick to point out, there’s another timeline out there where Dr. Colvin’s machine didn’t get unplugged and he survived. Was that other unseen timeline the “real” timeline all along and we were just watching one of the “fake” ones where he died? How do we define the “real” reality anyhow? Every version of Colvin would share the same past right up until the pivotal moment, so wouldn’t it make more sense to say that the one who’s alive is always real by virtue of being alive? And if so, what role does his machine play? If it reduces the odds of the gun firing to virtually zero, then the sci-fi premise is a red herring: he could accomplish the same thing by jamming the gun or unloading it (the timeline would still be split along that decision or by something else going wrong).
Putting aside the unpleasant prospect of playing Russian Roulette in the hope that some alternate version of us will keep winning, is there any evidence that this sort of thing has happened by chance? People sometimes do make it through incredible odds time and again. There are people who have been struck by lightning more than once and emerged unharmed each time. People have survived multiple plane crashes.
Tsutomu Yamaguchi, for instance, is famous for barely surviving the Hiroshima bomb, returning to his home in Nagasaki, and then surviving that atomic bomb too. If the many-worlds interpretation of quantum physics is accurate, it’s easy to think that the version of Tsutomu Yamaguchi in our timeline is the one who won the multiverse roulette (insofar as enduring two atomic bombs in a row could be called winning).
But we don’t need a multiverse to explain people beating incredible odds: probability theory already covers that. And there’s no point where an unlikely event could only be explained by the multiverse. It could always be described as a merely unlikely coincidence, and the math would work out exactly the same way. That’s one reason why the many-worlds theory has become a curiosity and inspiration for science fiction rather than a mainstream physics model. It’s a reframing of physics, but it doesn’t offer any advantages over less drastic interpretations of quantum mechanics. Everything it predicts can be predicted without a multiverse.
Infinity All the Way Down
Practical issues aside, the concept does make for great sci-fi stories that allow us to explore the human condition, the choices we make, how we define ourselves, and our connection to the world. But doing so requires ignoring some of the more bewildering aspects of an infinite multiverse, aspects that would reduce any attempt at a coherent story to rubble if we included them. The sci-fi multiverse is infinite, but not too infinite.
In most such stories, there’s one particular universe where multiverse travel was discovered, a “prime” reality that becomes a point of reference for the others. EEAAO has its alphaverse where the conflict first started, Rick and Morty has Rick Prime, and Loki has its Sacred Timeline.
But if every single instance of quantum uncertainty is a timeline in itself, then there wouldn’t just be one prime universe and inventor: there would be an infinity of them. One of them discovered verse jumping while drinking a cup of tea, the other coffee, and another one skipped breakfast. And in that reality, it was discovered by this person, and, in another one, by that person, and, in this next one, everything’s the same except this one molecule of a radioactive isotope on Mars decayed, and, in this other one, it was a different atom… and so on. It’s infinity all the way down.
Stephen Hawking once argued that the strongest evidence we have that time travel is a physical impossibility is that we haven’t been overrun by tourists from the future. After all, once it’s invented, people from that point on in the future can travel to any time period, so every moment in the past should already contain every time traveler who’ll ever visit it.
The same logic can be applied to the multiverse. If there’s even one person out there who can invent multiverse travel, then there are an infinite number of versions of that person and of that invention. If it’s possible right now, then there would also be timelines where it was possible long before now (say, a timeline where the Industrial Revolution happened in ancient Greece, or the Neanderthals came out on top, or the dinosaurs had opposable thumbs), and infinite permutations of those timelines.
If everything possible exists, then no matter how hard we look for the prime mover, all we’d ever keep finding are more variations. And with an infinity of such timeline-hopping variations out there, we probably would have already seen such visitors by now. Those events would, in themselves, also be uncertain and subject to many-world splits, but there are infinite variations to choose from, and all it takes is just one of those variants to call a press conference and make a dramatic announcement. If we say “maybe they’ve decided not to do that,” there’s still going to be an infinite subset who did decide to do that. It’s infinity all the way down.
Everything breaks down into nonsense when it’s measured against the scale of the multiverse — and it might not even be an infinite multiverse. Since the observable universe has finite mass and a finite size (perhaps not a finite true size, but the observable universe is what’s relevant in this case), there are really only so many configurations possible. But the number of potential worlds would still be staggering, more than enough to encompass every outcome we’ve imagined and many more that we haven’t.
Still, given that we haven’t already been invaded by hordes of Ricks fighting against armies of Jobu Tupaki and legions of Gabriel Yulaws, the multiverse would seem to just be a useful storytelling trope, a fascinating way of considering the way our world works and how our lives fit into it rather than a practical issue that we’ll ever have to worry about.
That’s how it seems for now. But in some nearby timeline, perhaps another version of you is getting ready to test out their latest invention…
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