Does Quantum Physics PROVE Parallel Universes Are Real?

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Does Quantum Physics PROVE Parallel Universes Are Real?</h4>

Parallel universes are an increasingly popular topic in science fiction, with a lot of modern media using quantum mechanics as a route to explore them. But, in reality does quantum physics actually predict parallel universes? And if so, is there any definite way to prove this through the mathematics of the quantum realm? 

This is Unveiled, and today we’re answering the extraordinary question; does quantum physics PROVE parallel universes are real? 

The many-worlds interpretation of quantum mechanics is a relatively new concept, but the general idea of parallel universes is much older. To some degree, the notion of an infinite multiverse was first hypothesized by ancient Greek atomists, over two and a half millennia ago. These old-time philosophers believed our world to be the accidental result of completely random collisions between atoms in a vacuum. These random collisions then in turn, they said, caused an infinite number of other worlds and universes… which led to the most primitive theory of a multiverse. These philosophies were still a long way from our contemporary view on how parallel universes should work, mostly because the scientific method hadn’t been developed yet - i.e. testing your claims mathematically and experimentally. An Arabic invention, it wouldn’t arrive until the 11th century.

Of course, the scientific method is now widely practiced. So, unlike the Greeks of old, today we can actually test the legitimacy of any multiverse hypothesis. And, before we get into the world of the very small, it’s important to note that ideas on the multiverse aren't solely a product of quantum physics. Multiple universes are predicted in other fields, too, such as in cosmology - where it’s a contentious product of cosmic inflation. As there’s no such thing as a unanimously agreed upon theory to explain the inflation of the universe… there are gaps to be filled. And, based on models originally proposed by the theoretical physicist Alan Guth, in 1980, there now exists a range of inflationary theories, with a fair few needing a multiverse to work. For the most part, advocates believe the inflation of the universe to be eternal. However, it’s also thought that there are small pockets where inflation halts, as well. These pockets lead to bubbles on a truly massive scale. And these bubbles can then safely contain an entire universe, such as our own. It’s a claim that’s by no means universally accepted, though. And a great deal of cosmologists, such as Stephen Hawking, believe it to be unscientific. One of the last papers published by Professor Hawking was on this topic., and it suggested that cosmic inflation need not lead to an infinite multiverse. 

So, moving to another field, and string theory also predicts a multiverse, although a different type. In general, string theory is the proposal that the most fundamental object in the universe is a string, and the frequency it vibrates at determines its particle type. In other words, reality as we know it - at the bottom-most base layer possible - is built of vibrating strings. For it to work mathematically, certain types of string theory require at least 11 dimensions. And, one potential explanation for this is that our four-dimensional universe - everything we see and know - is localized on a 4D object, called a ‘D3-brane’. Which is then thought to be floating in a higher-dimensional region; a space that’s believed to contain a multitude of other branes, all with different dimensions and properties. In some tellings, this higher-dimensional realm is known as the bulk. For the purposes of a multiverse, though, all these other (predicted) branes could all contain universes of their own. Ours is simply rendered along our own brane, while countless others exist elsewhere. Again, though, string theory is far from being universally accepted. Or experimentally verified. And some believe it will never even be possible to prove that string theory is correct.

And so, let’s head back to quantum physics, which does of course play a vital role in cosmology and string theory, from the off. However quantum mechanics itself also predicts its own multiverse. For the most part, we’re back dealing in the Many Worlds Interpretation, but it’s far from a smooth course. First, let’s look at how we arrived at Many Worlds.

The quantum multiverse theory comes from many of the most fundamental ideas in the field, although applying them to mean “multiple universes” wasn’t always immediately obvious. Many of the key ideas were formally established in the 1920s. One, called ‘superposition’, was actually first discovered a while before; in Thomas Young’s double slit experiment, in 1801. This is probably the most commonly taught experiment in the history of physics, yet it’s one that we still don’t fully understand. What we do know is that it proved light can be modeled as both a wave and a particle, an idea we’ve since labeled wave-particle duality. 

The experiment involved firing photons through two parallel slits towards a screen, and then observing which path the particle took. As it turned out, the photons would go through both slits simultaneously, creating a pattern of light and dark fringes. Confusingly, it was (and is) the act of observing the particles that determines what slit they pass through. Thus, we cannot say the location of these fringe patterns until we observe them. And, before this observation, the outgoing photons are peculiarly assumed to be in a superposition of all spots on the screen. It’s heavy stuff, but what it ultimately means is that, at its most fundamental, light can be more than one thing at once.

Little did Young know back then, but this realization could well be considered the very first indication of the multiverse; the very first step taken along a path to an infinity of parallel universes. Clearly, such unknowability isn’t what common sense would expect, and it defies our understanding of classical mechanics. So, the double-slit and all that followed led to a lot of hair pulling. The math was by all accounts correct, but how? The fact is that the quest for an answer is still ongoing. 

Nevertheless, as Young’s experiment shows, we simply can’t predict the results of quantum experiments with complete certainty. And, it’s this which led to the proposal of the Many Worlds Interpretation. In short, it claims that (at the quantum level) all possible outcomes result in new universes.

The theory was first pitched in 1957 by the American physicist Dr Hugh Everett, who believed that our reality is constantly splitting into a superposition of endless other realities. The neverending quantum splits are the key. As naturally they just keep going and going, and going. Ultimately, inevitably, they should lead to a multiverse of unfathomable size, with parallel universes existing upon branches upon branches upon branches of an infinite-dimensional space - otherwise known as a Hilbert space. Within this immense structure, every single possible state exists simultaneously in parallel. And again, for those who claim it to be true, the only evidence we need can be traced back to the double-slit experiment.

Finally, though, all of this clearly has some serious implications about the nature of time. In this world, our world, here and now, the true power of time will hopefully be explored in the future. However, for now we can see that if there were a quantum multiverse, then it may well be that within its infinite nature time (as we know it) falls apart. Yes, it’s a fundamental driver for how we understand reality, but we are but one tiny strand in an unknowable wide web. Does time work the same way across it all? Or only here? Or only in some parts, but not others? The problem with infinity is that it should mean that anything’s possible… and perhaps even that time is irrelevant. 

The disappointing news is that, currently, there are no clear ways to test for a multiverse. The scientific method relies on being able to experimentally test a hypothesis, and without a means to do so a theory can’t really progress beyond speculation. It’s why, at this stage, many scientists are inclined to dismiss the question of a multiverse entirely. 

Nevertheless, it’s a question that’s not going away. For some, it just makes too much sense to deny. And, at the very least, it’ll continue to underpin alt theories, science fiction, and fierce, potentially world-changing debate.