'Into the Spider-Verse': Parallel Universes Explained by Physicists

String theory is "ultimately be the tool" to explore the existence of parallel universes.

In the Marvel Comics multiverse, not all Peter Parkers are the same or even named Peter Parker. In Spider-Man: Into the Spider-Verse, the newest iteration of the radioactive-spider-fueled tale, various spider-people are brought together by a concept rooted in science but embellished in science fiction: parallel universes. Physicists tell Inverse that Marvel got at least a few things right.

Below are some spoilers for Into the Spider-Verse.

Stan Lee’s original Peter Parker exists in the Earth-616 universe, but Into the Spider-Verse, released Friday, predominantly deals with Earth-1610. This is the universe of Peter Parker and Miles Morales, both of whom have Spider-Man powers. When the villain Kingpin, who wants to access parallel universes to find alternative versions of his family, builds a particle accelerator to crack open reality, the spider-people from parallel universes are pulled into Earth-1610 — including the spider-pig Peter Porker, Spider-Gwen, and the jaded, slightly heavier Peter B. Parker.

Upon meeting the second Parker, Miles quickly puts together that he came from a parallel universe — mostly because he had just been studying Albert Einstein’s theory of general relativity at school.

Marika Taylor, Ph.D., head of applied mathematics and theoretical physicists at the University of Southhampton, tells Inverse that Einstein is a good place to start if Miles wants to understand parallel universes, but he (and audiences) should brush up on their string theory if they really want to make sense of these colliding worlds.

Various spider-people from the Multiverse.


Einstein Isn’t Enough

Parallel universes and wormholes show up in Einstein’s theory of relativity, explains Taylor, but his theory “captures only classical gravity, not quantum effects.” To build a real-life case for parallel universes, you need quantum physics and string theory, which would “ultimately be the tool to explore whether parallel universes can exist and be connected.”

String theory posits that all the elements of fundamental physics consist of one-dimensional strings, and there are at least 10 physical dimensions. We are acquainted with four dimensions: height, width, depth, and time. If there is a multiverse, including multiple universes in addition to our own, those 10+ dimensions must exist.

"The idea of parallel universes is probably more prominent in Marvel comics than it ever has been in string theory.

Princeton University’s Steven Gubser, Ph.D. a professor of physics and string theory reseracher, says that “the idea of parallel universes is probably more prominent in Marvel comics than it ever has been in string theory,” though admittedly many ideas in physics “rely on the idea of parallel universes or something like them.”

So, physicists accept parallel universes, sure, but even in the wildly theoretical world described by string theory, there are rules — and Into the Spider-Verse breaks a big one.

When in the 1950s, the American physicist Hugh Everett proposed a “many-worlds interpretation” of quantum mechanics, holding that there are many worlds that exist in parallel at the same space and time as our own, he included one key caveat. Those different worlds cannot interact once they branch away from one another, quite unlike the free-flowing movement of Spider-Man multiverse.

Spider-people from parallel dimensions, each with their own universe.


How String Theory Makes the Multiverse Possible

Ideas about the multiverse, explains Gruber, rely on the idea that, if there are extra dimensions, “there are undoubtedly a lot of possible ways to roll them up to get the four dimensions we observe.” In other words, some believe that the other dimensions we don’t see must be curled up in a way that enables them to be hidden. These “compactifications” result in universes with different physical laws.

“Thinking of others as parallel universes doesn’t seem wrong as long as we agree that we’re in our universe and we don’t interact with others,” Gubser says. “Once we start allowing cross-overs from one plant to another, it’s probably hard to write down physical theories that make sense and connect with what we know about the world experimentally.”

Kingpin’s Particle Accelerator Fail

Taylor agrees, pointing out that while it’s quite possible to find mathematical descriptions of parallel universes, “the real question is whether they can be connected in any way to ours.” Communication with those dimensions is harder to describe in a consistent mathematical way, and most likely cuts out the feasibility of using a particle accelerator to access them, like Kingpin does.

“In science fiction, it’s quite common for writers to use ‘wormholes’ to connect parallel universes, but it seems that wormholes would be impossible to create with ordinary matter and energy,” Taylor explains. “If they were created they would be very unstable. Pretty much anything falling into the wormhole could cause it to destabilize and collapse.”

While the movie raises the stakes by short-wiring some of the parallel universe spider-people, they certainly don’t combust before entering Earth-1610.

A diagram of what a wormhole might look like -- not the way to go!

Public Domain

Mostly “On Board”

When physicists think about ifferent universes being different as so far that they have contain different particle physics, they don’t professionally venture to think of them as real places with living beings. Although Taylor does say that “as a scientist, I find it very hard to believe that parallel worlds such as in The Flash or Spider-Man could ever be so very similar to ours and yet differ in tiny amounts!” Her best guess is that the differences in those worlds would be very different.

Which is a point for Peter Porker. At the end of the day, Gubser points out, connecting movie moments to real points of inquiry like string theory can make for some good story-telling bolstered by science.

“As long as we don’t confuse it with scientific inquiry,” Gubser says, “I’m on board for a great ride with all the spider-creatures the moviemakers want to bring forth!”

Interested in seeing Spider-Man: Into the Spider-Verse? Then watch our review below:

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