Multiverse: fact or fiction?

Our universe is incredibly big, encompassing hundreds of billions of galaxies, each containing an unimaginably vast number of stars. But is our universe the only one?

Lately, the word ‘multiverse’ has become a part of the regular lingo in pop culture (mostly thanks to Marvel) and if you are like me, you’ll throw the term around like a pro — but do you really understand what a ‘multiverse’ is? Perhaps more pressingly, is it real – or does it reside within the murky shroud of ‘movie science’? Before you ask, yes, movie science is a thing: Own up, you’ve once tried to use the force to open an automatic door, haven’t you? If Star Wars isn’t your thing, perhaps you’ve flirted with the idea of building a Jurassic Park? Oh, wait…. this one might be more possible than I thought, at least in the sense that we could theoretically see woolly mammoths wandering about, again! (check this out:  Martinelli L, et al. Croat Med J. 2014;55:423-7)

The scientific concept of the ‘multiverse’ was first proposed by physicist, Hugh Everett, in the 1950s, after what could be described as one of the most world-changing college drinking sessions of all time (not including that time Tolkien conjured the Lord of the Rings in the pub). As the term suggests, the multiverse describes a hypothetical group of universes that together make up all that exists. For a long time, this concept of ‘parallel universes’, ‘alternative universes’ or ‘many worlds’ has been used in science fiction, enabling characters to jump between timelines and realities — remember when Will first entered the Upside Down in Stranger Things?

But how close is this to reality? In the words of cosmologist George Ellis, ‘the notion of parallel universes leapt out of the pages of fiction and into scientific journals in the 1990s’, with scientists proposing several multiverse theories, starring (hehe, see what I did there?) universes that are exact copies of our world or featuring branching, wibbly-wobbly timelines.

So, what are some of these multiverse theories – and why do they sound so familiar?

Parallel Universes: You X forever

In the simplest multiverse theory, scientists assume that space is infinite, meaning that our universe goes on forever. This sounds plausible, right? I mean, I swear I’ve seen at least a handful of excel spreadsheets that last forever – so an infinite universe can’t be that hard to imagine. But there are only so many ways that the finite number of building blocks that make up our universe can be arranged across that infinite space – meaning they must eventually be repeated.

Imagine building your dream world with a finite number of Lego blocks; how long do you think it will be until you need to repeat that blue and yellow house? If you’ve ever played Minecraft (I know, I know – it’s for kids, or whatever), you’ll know what I mean. So, according to this theory, somewhere ‘out there’ is your perfect doppelganger, who ate the same breakfast as you, who has the same job as you, and whose life events all mimic yours.

Sound familiar? According to this theory, Spiderman fighting alongside Spiderman and Spiderman, to defeat their shared Spidenemies could certainly happen.

Alternative universes: One of these things is not like the other

Another multiverse theory stems from the beginning of time or the ‘big bang’ — the event where the singularity, sometimes referred to as the primordial atom, exploded in all directions (much like that bag of popcorn I left in the microwave for far too long). To be more precise, the volume of the earth increased by ~1078 in a ridiculously short period of time – a process scientists termed, ‘cosmic inflation’. But while this process ended 13.8 billion years ago for our observable universe, scientists believe that inflation continues eternally in other corners of existence. So, as space continues to stretch, and inflation ends in one area, a new ‘bubble’ universe may form with its own physical laws of nature.

Thinking you have seen this before? Well, it is possible that when Dr Strange travels to an unfamiliar, psychedelic dimension to stop a bad guy from destroying our universe (argh, not again! At least this guy wasn’t purple…oh, wait…), he has just popped over to an alternative universe for a time-looped chat. You know, like those chats with telemarketers.

Many worlds interpretation: Every decision = a new reality

Other scientists ground their multiverse theory in quantum mechanics, whereby multiple states of existence of tiny particles, like electrons, are all possible, at the same time – captured in a ‘wave’ (or ‘timeline’, as Marvel would say). In the many worlds’ interpretation, the multiverse forms around you, with every decision causing a new ’branch’ in the infinite tree of existence. You can then view each branch as its own separate parallel universe, existing simultaneously alongside our world. So, next time you roll a die during a family-friendly game of Monopoly, you may roll a 1, but there are in fact 5 other ‘realities’ where you roll a 2, 3, 4, 5, and 6, and win the game! In this world, I am a medical writer, but in another, I like to think I am a universe-exploring traveller. But I do wonder, how many other versions of me are medical writers?

Clicking your fingers, trying to figure out why you recognise this theory? This theory forms the basis of Marvel’s Loki TV series, where the titular god of mischief changed his fate in Avengers Endgame and disrupted the timeline, inadvertently summoning agents that work to ‘prune’ the subsequent branches in the hopes of putting the brakes on all-out cosmic chaos.

So, back to the original question. The multiverse: is it fact or fiction? To date, the concept of the ‘multiverse’ remains a controversial and unproven scientific concept. Sorry folks, but the answer is (at least for now): fiction. Who knows what scientists will discover in the future? For now, we will have to settle for just the one observable universe and explore the hypothetical multiverse with Dr Strange and all his superhero friends.

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