“The Multiverse is a concept about which we know frighteningly little.”
Doctor Strange, 2021
The Concept of the Multiverse
What if there’s another timeline where the Philippines immediately closed its borders after the first reported COVID-19 case? Could we have avoided this 3-year economic crisis that affected every sector in our country? Since the 1980s, the possibility of having parallel universes has been one of the most controversial topics in Science. The multiverse theory suggests that an infinite number of universes, including the one we are constantly experiencing, compromises everything that exists. The present universe is just a small part of a larger universe that extends beyond the limits of our observations.
Different Levels of Multiverse
The multiverse is a matter of debate within the physics community. Physicists question whether the multiverse exists and if it is worthy of scientific inquiry. Stephen Hawking, Max Tegmark, and Alan Guth. Physicist Max Tegmark distinguished four levels of the multiverse into a hierarchy, where each multiverse progressively diversifies at increasing levels.
Level I: Regions Beyond Cosmic Horizon
The most straightforward scenario that the majority of cosmologists accept. Here, it is assumed that space is infinite and contains matter at the same distribution as we see in our observable universe. Because there is an infinite amount of space in the universe, there may be another portion of the universe where a duplicate of our world exists.
Level II: Universes with Different Physical Constants
Under the rules of inflation theory, the multiverse consists of an infinite number of universes with different spacetime dimensionality and physical constants. As the domain of space stretch endlessly, some regions of space may stop stretching and form distinct bubbles. Perhaps when Dr. Strange traveled into an unfamiliar psychedelic universe, he had popped into one of the Level II multiverses.
Level III: The Many Worlds of Quantum Physics
The many-worlds interpretation theory implies that the multiverse forms around you as certain observations cannot be predicted with probability. As a result, a different universe is created for every possible outcome of a certain event. For example, all six possible ways a die lands on a number correspond to six different universes.
Level IV: Ultimate Ensemble
The final level considers that all real universes are governed by different mathematical equations. Parallel universes in level IV have their own mathematical structure in laws of physics, cosmological properties, or quantum states. Other universes exist outside of time and space, making it hard to visualize them. This opens the whole realm of possibility.
Scientific Theories of the Multiverse
Cosmic Inflation
As we know, the universe with a bang. But Alan Guth, a physicist from the Massachusetts Institute of Technology, questioned “What was is that banged?”
The theory can be regarded as a “prequel” to the Big Bang— where the universe had gone through an extremely rapid expansion in less than a trillionth of a second. Consequently, this leads us to the possibility of “eternal expansion”, which generates multiple pocket universes continuously. This idea narrates that inflation never completely stops. Universes are formed in places where inflation stops.
Big Bang Theory
The Big Bang Theory is the leading explanation of how our universe began. According to this theory, the entire universe was once an infinitely small singularity condensed by immense denseness and heat.
Suddenly, a massive explosion began that ballooned the universe faster than the speed of light— this period is believed to be cosmic inflation. When inflation had stopped, the big bang took place. The “reheating” of the universe, which occurred from the flood and radiation of the explosion, gave birth to the particles, atoms, stars, and galaxies we know today.
Our observable universe is one of the many regions where inflation ended, along with unobservable universes beyond ours. This suggests that infinite regions of the universe, having different space-times, expanded at different rates.
So, Do Parallel Universes Exist?
Although the multiverse theory has a few scientific grounds to support it, there are still skeptical Physicists who believe that the concept of multiple universes does not make sense. Physicist Paul Davies, a director from Arizona State University, critiqued that the theory is based on assumed conditions that scientists haven’t proved yet.
“The multiverse is often used to solve the mysteries of existence by assuming that there are an infinite number of universes. Everything is out there somewhere, so that’s the end of the story.”
Davies, 2015
At the end of the day, the multiverse theory is just a theory. Scientists have yet to come up with a way to test these theories to prove the existence of parallel universes. If the universe is based on how far the observer can see and measure, then the results will depend on the ability of observers to model and count them. In this way, there is much freedom where random inferences can be derived.
We haven’t really figured it out yet… so it’s up to you to decide whether to believe or reject that our universe is part of something much bigger than what we know.
References
Kuhn, R.L. (2015, December 24). Confronting the Multiverse: What ‘Infinite Universes’ Would Mean. Space.com. https://www.space.com/31465-is-our-universe-just-one-of-many-in-a-multiverse.html
Setter, P. (2021, December 15). How real is the multiverse?. Space.com. https://www.livescience.com/how-real-is-the-multiverse
Tegmark, M. (2003, January 23). Parallel Universes [PDF]. Cambridge University Press. https://space.mit.edu/home/tegmark/multiverse.pdf
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