Exploring the Infinite: A Beginner’s Guide to the Multiverse
The multiverse is a concept about which we know frighteningly little…
The Multiverse Hypothesis
In the past decade, scientists, especially cosmologists, have been considering the idea that our universe is not the only one in existence, that there could be an infinite number of universes- an entire multiverse beyond the confines of what we see. While this idea may seem ludicrous or straight out of science fiction, the very fact that it is a point of contention in the scientific community has transformed it from a bizarre idea to a hypothesis that is not only a consequence of some of our biggest theories, but one that could also hold answers to key questions about our very existence.
The multiverse hypothesis at its core is the idea that our universe is part of a larger, perhaps infinite group of universes that have different features.
Multiverse Level 1
A level 1 multiverse is essentially an extension of our universe and is expected to have the same laws of physics and physical constants that govern our reality. There exists a rough estimate of the distance of the next closest universe from ours. A distance of 10 to the power 10 to the power 115 meters has been proposed! (Tegmark,M. (2003)) Most cosmologists have accepted this type of multiverse since it is a consequence of cosmological inflation. (which states that our early universe underwent an exponential expansion in a very small amount of time during its birth) (Ellis, G. F. R. (2011))
Multiverse Level 2
A Level 2 Multiverse is one that could be governed by different physical laws, possess different properties, and maybe even different dimensions. It is imagined to be a hypothetical field with an infinite number of ‘bubble’ universes having an infinite number of variations to the point where even another version of you may exist. (Tegmark, M. (2003))
Multiverse Level 3 and beyond
But it doesn’t stop there! Some scientists have even proposed models for level 3 and 4 multiverses that would be created as a result of quantum mechanics, working on the theory that certain observations cannot be predicted with certainty and so anything that can happen, does happen. Picture rolling a dice and getting a 3. The chances of that happening are 1 in 6. But in a level 4 multiverse, all those other 5 outcomes that didn’t happen in your reality happen in other ‘branched’ ones thereby creating several universes or ‘splits’ because of one outcome.
Why are we so interested in the idea of a multiverse? One particular reason is that a multiverse could hold an explanation for a key question about the nature of our existence- why does our universe have fundamental constants that are exactly fine-tuned for our existence? For example, why is the composition of dark matter in our universe just right for the formation of galaxies? Any higher, and our galaxy would be pulled apart. Any lower, and it would collapse.
According to the multiverse hypothesis, there are an infinite number of universes, and so it is only fair to assume that we just happen to be in the one where life exists and where the odds are in our favour.
While the multiverse may sound like an interesting theory that could explain some big questions, there is the problem of proof.
Science is fundamentally based on evidence and data. Since we can see only a small part of our ever-expanding universe, we can’t say with any certainty that a multiverse exists, but we also can’t prove otherwise.
Is getting proof possible?
However, there may be a way to get indirect proof, through the Cosmic Microwave Background Radiation. The CMBR is the electromagnetic radiation that has been left behind as a result of the Big Bang. Mapping it forms a sort of blueprint that is used to study the birth and origins of the universe. Cosmologists have proposed that it might be possible to find collisions of other ‘bubble universes’ with our own by studying the CMBR, since we are in a constant state of expansion.(Kleban et al., 2013)
Another test that could lend more credence to the multiverse theory would be studying the shape and topology of our universe; does it fold in on itself or extend on forever? The theories are potentially endless.
Whether you consider the multiverse a possibility or not, it is a fascinating concept to ponder over and has led to some very interesting questions about the very nature of our existence. It gives a whole new meaning to the question, “Are we alone?”.
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References
Tegmark, M. (2003). Parallel Universes. Scientific American, 288(5), 40–51. http://www.jstor.org/stable/26060282
Ellis, G. F. R. (2011). DOES THE MULTIVERSE REALLY EXIST? Scientific American, 305(2), 38–43. http://www.jstor.org/stable/26002750
Kleban, M., Levi, T., & Sigurdson, K. (2013). Observing the multiverse with cosmic wakes. Physical Review D, 87(4). https://doi.org/10.1103/physrevd.87.041301
Alexander Vilenkin, M. (2021). The Case for Parallel Universes. Scientific American. Retrieved 7 October 2021, from https://www.scientificamerican.com/article/multiverse-the-case-for-parallel-universe/.
Betz, E. (2020). Is the multiverse theory science fiction or science fact?. Astronomy.com. Retrieved 7 October 2021, from https://astronomy.com/news/2020/12/is-the-multiverse-theory-science-fiction-or-science-fact.
Carr, B., & Ellis, G. (2008). Universe or multiverse?. Astronomy & Geophysics, 49(2), 2.29–2.33. https://doi.org/10.1111/j.1468-4004.2008.49229.x
