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Science Behind the Fiction: What's the reality behind multiverses and alternate realities?

Contributed by
Nov 7, 2018

In 1962, Philip K. Dick published The Man in the High Castle, a novel that went on to win the Hugo Award for Best Novel the following year. It tells the story of an alternate history in which the Axis powers won World War II.

Now a live-action series produced by Amazon, The Man in the High Castle takes the notion of alternate realities a step further with its own, in-world novel entitled The Grasshopper Lies Heavy, which outlines a second alternate history wherein Germany and Japan did not win the war, bringing the whole thing full circle.

While Dick was known for pioneering and expertly exploring interesting science-fiction plots, he can't take credit for introducing readers of fiction to the idea of parallel worlds.

Parallel universes were explored in fiction as early as the mid-17th century. The Blazing World, a novel by the Duchess of Newcastle, Margaret Cavendish, tells the story of a woman who passes through a portal and into another world. A smattering of stories was told between Cavendish's novel and Dick's, but the idea of the multiverse as a storytelling element really took off in the 20th century.

There are, at current, too many examples to count within the confines of this column but authors and filmmakers have continued to stretch the limits of the types of tales that can be told within this sub-genre. It's an impressive feat considering the possibilities are seemingly limitless.

2001's Donnie Darko was a sleeper hit that has since achieved cult status and involves the consequences of unintentionally creating a pocket universe. Marvel and DC lean heavily on the conceit that their characters exist within a vast collection of interrelated universes, both to tell some incredible stories and as a reset button when narratives become too convoluted. Even the Teenage Mutant Ninja Turtles franchise revealed in Turtles Forever that every incarnation of the heroes in a half shell exists in their own distinct but connected worlds.

On the small screen, Stranger Things, The Twilight Zone, Star Trek, Futurama, and Doctor Who have all used alternate realities to great effect. And who could forget Sliders, the mid-'90s Jerry O'Connell vehicle that relied solely, for its central premise, on the many worlds hypothesis?

What makes the idea of the multiverse special is that it's unique among sci-fi tropes in its acceptance from the general population and some factions of the scientific community as a potentially factual reality. But is that confidence deserved? Is there a good reason to emphasize the reality in alternate realities?


While the idea of alternate realities and distinct, separate universes has existed in fiction for centuries, it has existed as a legitimate scientific hypothesis for almost as long.

In 1705, Isaac Newton wrote in Opticks, "And since Space is divisible in infinitum, and Matter is not necessarily in all places, it may be also allow'd that God is able to create Particles of Matter of several Sizes and Figures, and in several Proportions to Space, and perhaps of different Densities and Forces, and thereby to vary the Laws of Nature, and make Worlds of several sorts in several Parts of the Universe. At least, I see nothing of Contradiction in all this."

It's important at this point to pause briefly and discuss the various uses of the word "universe." The original meaning of the word referred to all of existence and it seems this is the way Newton is using it here.

The word "multiverse" implies separate places — universes each — existing apart from one another within a larger existence. In this way, use of the word "universe" refers not to all that there is, but to all that there is in our particular pocket of reality.

In more modern times, the possibility of multiple universes has enjoyed varying degrees of popularity among the scientific community, and rightly so.

The scientific method hinges on a few fundamental principles. You likely learned about some of them as a kid, right before you built a paper mache volcano, as is the birthright of children everywhere. Namely, the scientific method requires ideas to be submitted to experimentation, observation, and verification.

For this reason, the idea of a multiverse rubs some members of the scientific community the wrong way. Multiverse theory is, by definition, unfalsifiable and outside the realm of experimentation. It flies in the face of the scientific method and therefore, some would argue, should be left to the realm of philosophy, not science.

That being said, the case for the multiverse is not solely within the province of fantasy.


The notion of the multiverse is inextricably tied to the origin of our own home turf. For years, physicists were puzzled by the seemingly uniform temperature and smoothness of the universe.

Everywhere we looked, we found temperatures and distribution of matter were the same across the board (aside from minor variances), over vast distances of space. This didn't make sense when bumped up against our understanding of reality. Given the distances involved and the amount of time elapsed, it wasn't possible for such distant areas to be causally connected.

Then, in 1980, astrophysicist Alan Guth proposed the idea of cosmic inflation, a sort of negative gravity that pushes objects apart.

This rapid expansion, much faster than the typical expansion of space-time, can account for the uniformity of temperature and matter distribution. But in order for our universe to exist, it had to have stopped pretty quickly — less than a second after the Big Bang.

Guth suggested that the period of rapid expansion must end because the false vacuum required for its effects is unstable. The idea of the multiverse arises from taking this same model a step further.

Think of the cosmic expansion as radioactive matter in a state of decay. There's a certain probability that any one atom might decay at any given time but not all of it will at once. What some proponents of the multiverse hypothesis suggest is that one segment of the reality experienced a decay of that early false vacuum and became the visible universe.

That rapid expansion may still be going on elsewhere, decaying over time and creating a separate instance of reality each time with potentially different physical laws. Because of the nature of this kind of expansion, it can go on infinitely, popping out new universes as it does.

It's difficult for us to conceive of a universe that behaves in a fundamentally different way from ours. After all, things operate the way they do because they must, right?

Enter String theory. It postulates that all of reality, from the very big to the very small, arises from the vibrations of one-dimensional "strings" trillions of times smaller than a proton.

String theory is, as yet, unproven, but the math involved offers compelling explanatory powers implying, at the very least, that it may be on to something. Taking it to its limits allows for various sorts of physical laws to arise, not all of which would result in a universe we would recognize.

Leonard Susskind, one of the originators of string theory said, while discussing the topic with Closer to Truth, "What string theory brings to it is something about the number of possibilities. It's not just A and B, it's not just A through Z. But the number of possible kinds of universes, the number of possibilities that are inherent in the equations are numbers that are far, far bigger than the number of atoms in the universe. The number 10^500 gets bandied about. Not 10^500 different universes, but 10^500 types of them, each one being repeated over and over again."


Let's push our skepticism to the side and imagine, for a moment, that one or more of the multiverse hypotheses is true — whether that means the space within our own pocket universe is infinite, or it is finite but one of the countless bubbles in a vaster cosmic foam. One thing would be for certain.

The domain of reality would be limitless and unbounded. The opportunities for physical scenarios to play themselves out would literally know no bounds.

The acceptance of such a universe requires the acceptance of the idea that anything that is not prohibited by the laws of nature must exist. Moreover, it must exist not just once but an infinite number of times, such is the nature of infinities.

This means that because you exist, an infinite number of yous exist throughout the vast cosmic expansion — infinite yous identical to you at this moment and infinite yous with only slight variations. And the scale of variation must carry on along the spectrum covering every possible variation of you and the life you might have lived under every possible set of circumstances.

It means that the nightmare world of Philip K. Dick's Man in the High Tower would exist somewhere out there, beyond the reach of our telescopes.

It is even true that, provided this view of the universe is correct, there are versions of you living your life, exactly as you are, but five minutes behind or 50 years in the future. There are infinite versions of you who are dead and an equally infinite number who are alive and always will be so long as reality itself exists.

There's something comforting in knowing you are infinite. But, as is perhaps appropriate of the infinite, there is also something discomfiting about this idea. It niggles at the notion of personal identity and of free will.

But there's an upside.

There are also infinite versions of you who are, right now, laughing, experiencing joy, falling in love, and eating nachos.

Although, that also means that while infinite versions of me are eating not just nachos but the very best plate of nachos that have ever been made, those versions of me are not me.

And that makes me mad. Those are my nachos.

The Man in the High Castle Season 3 is now available on Amazon.

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