The Multiverse Theory and Cats
The multiverse theory - the notion that many worlds exist in parallel at the same time and space as our own1 - has certainly intrigued many individuals, including some of the authors of this book. Whether it be Marvel or DC, the multiverse theory has become increasingly popular in fictional realities. In physics, this theory is referred to as the Many-Worlds Interpretation (MWI) and is one of the interpretations used to make sense of what is happening in quantum physics.2 To understand this theory better, let’s ask ourselves, what even is quantum physics?
Quantum physics deals with the study of matter and energy at its most fundamental level (electrons, protons, and the likes), examining the behaviours and properties of very small objects. This is more difficult to do and detect in larger objects, which has resulted in a misunderstanding that quantum phenomena are otherworldly and not a part of our daily lives.3 Quantum physics is inherently strange because it runs against our everyday understanding of the world. Simply put, the rules in quantum physics don’t appear to resemble the way we describe routine events and actions.
Let’s take another glance at the multiverse or MWI and try to understand what is really happening. Pretend that there is an experiment happening involving a cat in a box. At the time that you are about to open the box, you know that the cat will either be alive or dead, but once you lift the lid, the box will reveal only one of these outcomes. Advocates of the multiverse theory argue that at the moment the measurement is made (in this case, when you lift the lid), reality fractures into two copies of itself, one where we experience outcome X (which would be that the cat is alive), and another where we experience outcome Y (which would be that the cat is dead). However, right until the lid is lifted, physicists propose that the cat is both alive and dead at the same time.
What does this mean? It means that until the box is opened, there were always two worlds that were identical to one another until the moment when the act of removing the lid determined the cat’s fate. This famous paradoxical thought experiment is known as Schrödinger's Cat. 4 Keep in mind that this theory does not apply to actions we do not see, but rather to things which we are observing. Anytime an individual makes an observation and one of many possible actions happen, it can be explained by quantum choices (the choices made by quantum physics like when the box lid came off and revealed a dead cat or alive cat). 5 Similarly to the cat, small particles in the universe split into different versions of themselves when faced with a quantum choice. Up until a particular point in time (the present) there is no difference in our personal experience of our subjective reality.
So… Do parallel universes really exist? Remember that unlike fictional realities in the Marvel Cinematic Universe, there is no timekeeper or magician keeping us in order and watching over all the worlds… and we may never truly know what is the truth but it does answer many problems and unexplained behaviours in physics. 6
Vaidman, Lev. “Many-Worlds Interpretation of Quantum Mechanics.” Stanford Encyclopedia of Philosophy, August 5, 2021. https://plato.stanford.edu/entries/qm-manyworlds/.
Vaidman, “Quantum Mechanics”.
“What Is Quantum Physics?” Caltech Science Exchange. Accessed September 18, 2023. https://scienceexchange.caltech.edu/topics/quantum-science-explained/quantum-physics#:~:text=Quantum%20physics%20is%20the%20study,us%2C%20acting%20on%20every%20scale.
Albert, David, and Barry Loewer. “Tails of Schrödinger’s Cat.” Essay. In Perspectives on Quantum Reality, edited by Rob Clifton, 81–92. Dordrecht: Springer, 1996.
Vaidman, Lev. “Why the Many-Worlds Interpretation?” Quantum Reports 4, no. 3 (2022): 264–71. https://doi.org/10.3390/quantum4030018.
Vaidman, “Many-Words,” 264-71.