By: Nathan Simpson
The concept of alternate universes may seem like a science fiction, but it is a very real concept. In fact, it is a genuine hypothetical solution to some real-world problems. The fledgling idea of the “multiverse” has been around for only a decade or so, but it could be true that we are just one of many universes each with its own set of physical laws.
What is the “multiverse”?
The word multiverse is quite a general term because its definition can vary depending on the context in which it is used. The most famous example of the multiverse lies in the Many-Worlds interpretation of quantum mechanics proposed by Hugh Everett in 1957 which states that there are many worlds which exist in parallel in spacetime with our own, and what we observe is just one of many possible results of reality. This allows for the removing of all randomness from physics because every possible outcome of every possible event would happen – though not necessarily in the same universe.
Swedish-American cosmologist Max Tegmark has created a taxonomy to classify the types of multiverse. It is arranged using a levels system, such that each level builds on the understanding of the previous one. There are 4 levels to date which are summarised below:
Level 1: This is a relatively simple model that simply states there are many, possibly infinite volumes, or bubbles, like our observable universe. Each of these bubbles occupy space and have the same set of physical laws and constants. That would mean there are an infinite number universes exactly like ours, and hence an infinite number of yous reading this article right now!
Level 2: This type of multiverse is a set of universes much like in Level 1, but the laws and physical constants are different, i.e. pi could be 200 and E=mc etc. In fact, due to the theory of chaotic inflation and the fact that the multiverse is expanding, there are regions in this space that would stop expanding and form bubble universes just like the ones in Level 1, a bit like bubbles being trapped in soap. The number of universes formed in this way has been calculated – which is an incredible feat – to be 1010^10,000,000.
Level 3: Now, this is where things get really interesting. Here, we are reacquainted with the Many-Worlds theory from earlier. The only dissimilarity between Level 3 and Level 1 is where the alternate outcomes to different events occur. In Level 1, they occurred in the same 3D space, just very, very far away. However, in the mysterious world of a quantum mechanical multiverse of Level 3, these events happen in an infinite dimensional space on something called a quantum branch (search for “Hilbert Space” if you want to try and get your head around it).
Level 4: If the concept of infinite dimensions wasn’t complicated or mind-boggling enough for you; have no fear, Tegmark is here to solve that. Tegmark himself termed Level 4 of the Multiverse system to be the Ultimate Ensemble, and for very good reasons: it contains within it the set of all mathematically possible universes, such that it is impossible to generalise further to a Level 5.
Even though you now have a general idea of what a multiverse is (or could be), the idea that they could be possible, real explanations for the world we live in might still be a faraway concept. If you’re still skeptical, don’t worry! The validity of the multiverse as an actual scientific idea is a hot topic in the scientific community, with many reputable physicists in opposition to the idea. The argument against the multiverse theory as a valid scientific idea stems from the fact that it directly contradicts the scientific method, as it has no testable elements to it or outcomes we can predict.
On the other hand, there is serious scientific research trying to prove the theory right. You might have recently seen headlines along the lines of “Scientists Claim Proof of Alternate Universes”. These articles stem from the work of Ranga-Ram Chary, who claims that he has found an anomaly whilst looking at the cosmic background radiation, or the afterglow of the big bang. He says could be attributed to a collision with another universe that has a baryon to proton ratio about 65 times larger than that of our universe. However, he also states that there is a 30% chance this could be attributed to noise fluctuations, so there isn’t anything to conclude as of yet besides news agencies are capable of creating very suggestive headlines.
Professor Jeff Forshaw of the University of Manchester, who has written about quantum mechanics and the multiverse, had this to say:
“The world could have features about it that we can’t prove. It may be that we can’t do experiments to ascertain this or that about the universe. In the case of the multiverse, it hasn’t been proven that there isn’t some sort of decent experimental evidence that would demonstrate that we are living in a multiverse, so there’s no mathematical proof that we can’t make some observations at some point in the future that demonstrates we are living in a multiverse. In that sense, it remains an interesting idea. It doesn’t have to be testable at the moment. I would make a stronger statement and say that even if you can’t prove that there is no possibility to do an experiment so that an idea can be proven to be true or false, that idea could still be the case. There could be things that we will never be able to prove about the universe that are true.”
There is much research to be done in the field of multiverse theory. Whether it is true and provable, true and not provable or not true at all, rest assured: if it is true, there are infinitely many people researching it at this instant, and if not, then why bother?