Over the course of five seasons, the Netflix series Stranger Things traces the lives of a loosely connected group of teenagers and their families in a quiet, fictional town in Indiana. Their ordinary routines are repeatedly shattered after a secretive government laboratory accidentally opens the door to a terrifying other realm, allowing strange creatures to spill into their world and wreak havoc.
The show’s monsters, supernatural villains, and telekinetic children are, of course, products of imagination. Yet the central idea driving the story — the existence of a parallel universe — is rooted in a genuine scientific debate. This concept, which sits at the heart of the series as it approaches its final chapter later this year, has occupied physicists’ minds for more than seven decades.
While Stranger Things clearly leans more toward fantasy than hard science, it frequently references real physical principles. Electromagnetism is used to explain malfunctioning compasses and magnets that inexplicably fall from refrigerators. In one memorable moment from the third season, the characters even rely on Planck’s constant as part of their effort to seal a gateway to the alternate realm known as the Upside Down, though the show quietly uses a value that would not have been standard during its 1980s setting.
Among all the scientific ideas mentioned, the most significant is the “many-worlds interpretation” of quantum mechanics. When several young characters suspect their missing friend may be trapped in the Upside Down, they ask their science teacher whether traveling there might be possible. His reply references Hugh Everett’s many-worlds theory, bringing a real and controversial scientific idea into the storyline.
Everett, an American physicist, introduced this interpretation in the 1950s while grappling with what is known as the measurement problem in quantum physics. At the quantum level, particles can appear to exist in multiple states at the same time — for example, an electron may occupy two positions simultaneously — until it is measured. Once observed, the particle seems to settle into a single, definite state.
The traditional explanation for this phenomenon, called the Copenhagen interpretation, suggests that before measurement, a particle exists in a cloud of probabilities. Observation causes this uncertainty to collapse into one outcome. Everett proposed a more radical solution: all possible outcomes actually occur. When a measurement is made, the universe itself splits, with each result unfolding in a separate branch of reality. According to this view, reality constantly divides, creating countless parallel universes.
This idea has remained deeply controversial. Many physicists find it difficult to accept because, if these parallel worlds cannot influence one another, there is no clear way to test whether they truly exist. Jorge Pullin, a theoretical physicist at Louisiana State University, notes that the lack of experimental verification makes many worlds an uncomfortable proposition for scientists who rely on falsifiable theories.
Others, however, argue that the many-worlds interpretation is appealing precisely because of its simplicity. Sean Carroll, a theoretical physicist at Johns Hopkins University who has also advised science-fiction films, considers it one of the most coherent explanations of quantum mechanics. In his view, it matches experimental data without requiring additional assumptions. A recent survey published by Nature suggests that many worlds is now the third most popular interpretation among quantum physicists.
Still, real-world physics offers no support for the kind of nightmare landscape portrayed in Stranger Things. If parallel universes exist, they would likely look almost identical to our own. Differences would arise only from tiny changes at the subatomic level. As Carroll explains, these universes would follow the same physical laws and contain versions of the same people, rather than monstrous creatures and apocalyptic skies.
Even if a dark mirror world like the Upside Down were possible, current physics rules out any practical way for humans to travel between universes. In the show, characters routinely move between worlds through portals hidden in trees, lakes, and even school walls, often returning with little more than injuries and slime. At one point, a powerful machine built by the Soviet Union forcibly opens a gateway as well.
Such scenarios remain firmly in the realm of fiction. According to Carroll, interactions between different branches of reality are essentially impossible, let alone the idea of a person stepping from one universe into another. Pullin agrees that portals of the kind shown in the series are not compatible with established physics.
A small number of researchers have speculated about limited interactions between worlds. David Deutsch of the University of Oxford has suggested that quantum computers may owe their extraordinary power to calculations being carried out in parallel across multiple universes. Even so, this kind of interaction would be restricted to quantum particles, not human beings or towering monsters.
Although Stranger Things does not strictly follow the rules of theoretical physics, it joins a long list of films and television series that use parallel universes as a storytelling device. Movies like Spider-Man: Into the Spider-Verse and Doctor Strange in the Multiverse of Madness explore how multiple realities complicate heroic lives, while films and series such as Sliding Doors and Dark Matter imagine how small choices could lead to entirely different futures.
Ultimately, as Pullin points out, popular culture’s fascination with parallel worlds depends on stretching scientific ideas beyond their limits. If the theories were followed exactly, the result might be intellectually interesting, but far less entertaining.
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