The film “Everything Everywhere All at Once” won the Oscar in 2023. For those who haven’t seen it, the movie is based on the multiverse concept – the idea of the existence of parallel dimensions that may resemble our reality but differ in some way. Without revealing the plot, its main theme revolves around the notion that a small change can significantly alter a person’s life and even the entire universe.
Take a simple example: have you ever wondered how your life could have turned out if you had gathered the courage to talk to that girl you were deeply in love with back in school? Perhaps everything would have worked out. With increased self-confidence resulting from success, you might have achieved great heights in your career. Small things can have a big impact.
The recent film is a vivid example of the influence of the multiverse in cinema, and it’s not the only one. The film and television industry has embraced this concept as a way to refresh existing franchises, most notably in the Marvel universe and recent “Star Trek” films. While it’s entertaining, it also raises questions. Is the idea of the multiverse scientifically valid?
Answering this question is challenging because the definition of the multiverse is somewhat elusive, encompassing various interpretations.
Infinity and Inflation Although there are numerous ideas about multiverses, to understand those taken most seriously by scientists, it’s best to start with the different types popularized by theoretical physicist Max Tegmark, who identified four of them.
The first type proposed by Tegmark is based on the idea that space is extremely vast – possibly infinite. While the observable universe appears as a sphere centered on Earth with a diameter of about 92 billion light-years, this is only the part of the universe we can see. If the cosmos is much larger, there could be an incredible diversity of worlds in other regions of space where other stars and planets have formed. If the cosmos is infinite, there might be a region that is a carbon copy of our own.
Perhaps even more intriguing is the possibility of a space fragment that is identical to ours, except in that place, you had the audacity to ask that girl out on a date. These diverse realities represent the first type of Tegmarkian multiverses and are the least likely, relying on the infinite size of space.
The second type of multiverse relies on Inflationary Theory, a prominent physical theory that emerged in the 1980s to explain certain features of our universe – for example, why space looks the same in every direction and why space doesn’t seem to curve back on itself.
In essence, inflationary theory suggests that shortly after the universe’s formation, there might have been a very brief period when it expanded faster than the speed of light. This explains why space appears flat because if you take any shape, no matter how curved, and expand it enough, it will look flat. This physical reality also allows flat-Earth proponents to claim the Earth is flat despite being spherical – visually, the curvature is negligible. Inflation also explains why the universe appears so homogeneous, no matter where you look. If you take a small patch of space where everything is the same and rapidly expand it, the increased space will also look the same.
Although inflation hasn’t been conclusively proven, the scientific community recognizes its plausibility.
Multiplicity of Multiverses
The third type of Tegmark’s multiverse arises from the laws of quantum mechanics. In traditional quantum mechanics, statistical laws govern the universe. Everything is possible until we make a measurement. The most well-known example is Schrödinger’s cat, a scenario in which it is considered that the cat inside a box with a radioactive element, a vial of poison, and a Geiger counter that will break the vial if the element decays. Common sense tells us there can only be two outcomes: the cat is either alive or dead, even if we don’t know which. But standard quantum mechanics says the cat is simultaneously alive and dead until you open the box and check.
However, there is a version of quantum mechanics according to which, when you peek into the box, you actually create two versions of reality: one in which the cat is alive and another in which it is dead. This is called the Many-Worlds Interpretation.
Although this interpretation of the laws of quantum mechanics is not universally accepted, it is gaining more supporters among scientists. According to this version, the multiverse is in constant development, where each decision leads to the emergence of another universe. A slightly different version suggests that all versions of reality exist simultaneously. When faced with decision points, we simply choose which reality to branch into. It is undoubtedly an interesting hypothesis that captivates many philosophy students.
The fourth type of Tegmark’s multiverse is a universe where, essentially, everything is different. In the first three types of multiverses, the fundamental laws of physics are the same, but some parameters may have different values – for example, gravity might be slightly stronger in one universe and weaker in another. However, in the fourth type of multiverse, it is assumed that the laws of physics in other universes may be completely different. Perhaps cause and effect differ. Perhaps these universes have a different number of dimensions, as in Edwin Abbott’s book “Flatland”. If we consider the possibility of entirely different physical laws, it is difficult to imagine all possible variations of fourth-type multiverses.
It should be noted that when considering the idea of a multiverse, one must be cautious with the term. In different theories, “multiverse” means different things, and not all theories have relevance to reality. Multiverses may be real, but before taking this idea seriously, it is necessary to specify exactly which multiverse is being discussed.
