It is common knowledge that the idea of a multiverse serves as one of the most prominent prompts for science fiction and has been for years and years, having inspired countless comic books, novels, and movies. However, what may come to a surprise to some is that the multiverse that we see in science fiction is actually derived from genuine scientific concepts, all residing in the field on quantum mechanics.
The catalyst that initiated the mass obsession with the idea of parallel universe’s was Schrödinger’s cat, the infamous paradoxical thought experiment. Erwin Schrödinger proposed the following: Consider a box, in which is placed a cat and sealed bottle of poison gas, along with another, smaller box that contains one single radioactive isotope. The radioactive element has a half-life of on hour, which means, according to quantum mechanics, that after one hour, there is a fifty-fifty chance that it will have decayed. A by-product of this nuclear decay is the emission of an alpha particles (otherwise known as a helium nucleus), and the bottle of poison is arranged to break open if struck by this particle (The Physics of Superheroes). Given this information, it becomes clear that there is an equal chance of the cat being dead or alive at the end of the hour; however, as the state of the cat is unknown until the box is lifted, the cat can be considered to be both dead and alive.
Now, Schrödinger’s cat itself did not serve a hypothesis for multiple universes, rather, the hypothesis for parallel universes was developed by one man’s interpretation of Schrödinger’s cat. Hugh Everett, an American physicist, agreed that Schrödinger’s cat would be both a dead and alive simultaneously; however, his explanation differed. In 1957, Everett suggested that the fates of Schrödinger’s cat would be simultaneous – in parallel universes. In one universe, the cat would survive, while in the other, the cat would die.
Furthermore, Everett proposed that every quantum interaction, and every interaction, for that matter, has multiple outcomes, varying depending on the universe. Let us suppose that this is true. For example*, imagine that a woman is debating or whether or not she wants to go swimming. She, after careful consideration, decides to go. Imagine if an accident happens, causing her to drown, thus killing her. Perhaps in an alternate universe, she decides not to go swimming, thus continuing to live. In one of these universes, this Jane Doe would be dead, and in the other, she would be alive. This idea can be applied to any action, interaction, of decision made by everyone and everything. This would mean that there are an infinite number of universes, each with slight differences to major differences, all based on the outcomes of events as small as, well, even what time we wake up on a given day, what parking space we choose, or even what shoes we decide to wear.
Now, this hypothesis sounds, yes, like science fiction. However, physicists do not just pull things like this out of a hat. Believe it or not, and, well, much to the dismay of many, hypotheses like these are all based on mathematics. For instance, Schrödinger’s cat was simply a teaching tool that Schrödinger used to illustrate how some people were misinterpreting the quantum theory (WTAMU). The exact principle that Schrödinger wished to better explain is known as the wave function, a combination of all the possible wave functions that exist. A wave function for a particle says that there is some probability that a particle can be in any allowed position, but one cannot necessarily say its particular position without observing it. If one puts an electron around the nucleus, it can have any of the allowed states or positions, unless it is observed and its position is learned (National Geographic). Parallels are clearly visible between Schrödinger’s cat experiment and this explanation of the wave function, such that the cat represents an electron that’s place cannot be predicted or known until it is visibly looked upon.
Now that the basis of the Many-Worlds Interpretation has been established, a closer look at the theory itself is required. While this theory is essentially a creation of Hugh Everett’s, the term “Many-Worlds Interpretation” was not coined until years later, during the publication of The Many-Worlds Interpretation of Quantum Mechanics, a book by physicists Bryce Dewitt and Neill Graham. The Many-Worlds Interpretation of Quantum Mechanics ultimately popularized the theory to the general public around the 1970s, however, many science fiction fanatics had been drawn to it many years earlier.
Today, the concept of parallel universes and, subsequently, a multiverse, frequents the minds of many and is apparent in many works of fiction, ultimately becoming a staple in popular culture. However, as previously mentioned, theories such as the Many-Worlds Interpretation are not necessarily dreamt up; they are genuine scientific concepts. Generally speaking, there have been few additions to the Many-Worlds Interpretation in recent years, but the theory has still persisted, gaining worldwide recognition and avid believers. While the idea of a multiverse is a bit radical and has been criticized by actual physicists, its existence is a possibility, and that is enough.
* Although many of these interactions may be insignificant, and not influence much, I will use an example of a decision that could change someone’s life
Baird, Christopher S. “What Did Schrodinger’s Experiment Prove?” 30 July, 2013, WTAMU, https://wtamu.edu/~cbaird/sq/2013/07/30/what-did-Schrödingers-cat-experiment- prove/#:~:text=%22Schrödinger’s%20Cat%22%20was%20not%20a,did%20not%20scient ifically%20prove%20anything.&text=Schrödinger%20constructed%20his%20imaginary% 20experiment,not%20match%20the%20real%20world. Accessed: 2 May 2021.
Kakalios, James. “The Physics of Superheroes.” New York: Gotham Books, 2006. Print.
Kramer, Melody. “The Physics behind Schrödinger’s Cat Paradox”. 10 Feb. 2021, National Geographic, www.nationalgeographic.com/science/article/130812-physics-schrodinger-erwin-google-doodle-cat-paradox-science. Accessed: 2 May 2021.