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Why The Multiverse Might Be A Reality

VO: Noah Baum WRITTEN BY: Nathan Sharp
We live in a universe, right? It's massive. It's expanding. But there's only one UNIverse... Right? Well, maybe not. The multiverse theory has long captured the imaginations of scientists and philosophers, but could it actually be true? Could there really be an infinite number of existences? And are we only seeing one of them? In this video, we find out.

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Why the Multiverse Might Be a Reality

While our universe is unfathomably large, it may not be the only one in existence. You’ve undoubtedly heard of the concept of the multiverse – a hypothetical, infinite collection of universes that all exist in tandem. Our universe is but one of many universes within a grander cosmic scale that contains countless others.

It may sound like the stuff of science fiction to you . . . and you may be right! The physics community is largely split over the idea. Skeptics argue that the concept is unscientific, as it can’t be empirically tested, and even that it undermines the credibility of the field of physics. Various eminent cosmologists, including Paul Davies, George Ellis, and David Gross vehemently deny the existence of a multiverse. However, other prominent experts, including Neil deGrasse Tyson and Stephen Hawking, have come out in favour of the idea.

It’s a debate that might never be resolved. But in this video, we’ll explore various theories for why the multiverse might be a reality.

One major theory that implies the existence of a multiverse is the bubble universe theory, otherwise known as eternal inflation. According to this theory, there have actually been many Big Bangs, rather than one. While universes are expanding throughout spacetime, other Big Bangs occur within them, giving birth to more universes. In other words, Big Bangs and their resulting universes are localized sections of spacetime, and there may exist numerous “bubbles,” or universes, within the cosmos. As each bubble expands and drifts apart, new bubbles are created in the empty space. Our universe began from the Big Bang, but the Big Bang was just one of thousands, perhaps millions, of Big Bangs. Our universe is a single bubble within a vast network of bubbles.

If that wasn’t cool enough, it’s also theorized that each specific bubble contains its own unique properties, physics, and physical possibilities. Perhaps in another universe, humans can fly. In another, we might be silicon rather than carbon based. The man who first introduced this idea, Paul Steinhardt, has since become a very vocal opponent however, declaring that since it can’t be tested, it can’t be considered a legitimate scientific theory.

Another theory is a little less outlandish and science fiction-y, but fascinating nevertheless. It’s called repeating universes, or the quilted multiverse, and basically postulates that if spacetime is infinite, there must be other, parallel universes out there due simply to probability. Given infinite time and space, all possible particle configurations will repeat themselves again and again, as there are only a finite number of configurations possible. Therefore, somewhere out there in the vastness of space, there must be identical worlds and even people. Assuming that spacetime is infinite, somewhere out there is another Earth, and another you.

Even with the proper equipment, we wouldn’t be able to detect these worlds or universes if they were far away enough. Nothing can travel faster than light, so objects farther away than the current speed of light simply cannot be detected. These worlds might be out there, but so far off that their light hasn’t reached us yet.

There’s another, perhaps even more bizarre theory called the brane multiverse, or brane cosmology. Now, bear with us here. Brane cosmology hypothesizes that our three-dimensional universe is a brane, or a dimension, on a larger, more expansive area called the bulk. The bulk is a space that contains infinite dimensions, and our three-dimensional universe is but one dimension of a vast, floating system of membranes within the bulk (hence the term “brane”). These membranes float within the bulk for infinite time, but once in a while they collide and explode in spectacular manner, giving rise to a big bang and creating another brane on the bulk. The reason for these collisions are hard to understand, but could be due either to gravity or to some type of attractive force within the bulk that we can’t currently comprehend.

This is similar to the bubble theory, as it also postulates that our own universe is one in a larger system of universes. Each big bang, or membrane collision, gives rise to a new universe, or a new membrane within the vast cosmic greatness.

But perhaps the most famous example of a multiverse, and the one familiar to most people, is the Many Worlds Theory. This theory goes by many names, including the relative state formulation, the Everett interpretation, or just simply the multiverse theory. In simple terms, this theory states that every action, and every decision, results in a split universe in which the opposite action or decision was made. For example, today you were deciding where to go for lunch, and you narrowed down your options to restaurant x and restaurant y. Today, you went to restaurant x, which means time itself split when you made that decision, and in another universe, you went to restaurant y. It sounds like nonsense, but believe it or not, there IS some science to back it up.

It all boils down to something called the double-slit experiment. In simple terms, this experiment measures a quantum object, which can be measured either as a wave or a particle. To explain why one object can be measured in more than one state, Hugh Everett hypothesized the many worlds theory. When a physicist measures a specific object, the universe splits itself into two – one universe where the object is measured as a particle, and one where it is measured as a wave. In universe A, the scientist observes the object as a particle. In universe B, the scientist observes it as a wave.

Now let’s assume that this rule carries over from quantum mechanics to everyday life. When one of two decisions or outcomes are made possible, the universe splits itself into two to accommodate both possible quantum results. In such a case, our life and history are not one constant line of decisions, but a branching tree of different lives. You may not be one person – you may be the result of a decision, and somewhere out there, living life unaware, is another version of you living out the opposite result.

The multiverse is certainly a tricky concept to articulate or study. While the idea of infinite universes sounds appealing, there exist many skeptics and outright disbelievers. That said, it’s still a possibility. It could be that we are living in one bubble amidst a sea of bubbles, the result of expansion and countless Big Bangs. It could be that out there, in the vast cosmic, particles continue to configure themselves in repetitive ways, resulting in numerous outcomes. It could be that our universe is but a membrane within infinite space with infinite dimensions called the bulk. Or it could be that the universe splits itself into two to accommodate different outcomes, resulting in infinite worlds.

Either way, there may be another you out there right now, wondering if there’s another them.

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