The Rick and Morty Every-Universe Fallacy
If anything can happen, would that really imply that everything does happen?
Popular multiverse stories often turn “every possible outcome occurs” into “anything we can imagine exists somewhere”, but those two are not the same. An infinite collection of universes can still exclude those that are not internally consistent.
An earlier version of this article was published in Cubed on May 2, 2022.
The idea of parallel universes, that one could travel among and find anything you can imagine, seems to now be showing up in a lot of fiction. The Marvel Cinematic Universe has evolved into a multiverse of different realities. The movie Everything Everywhere All at Once explores the idea in a way that is both comical and philosophical. The series Dark Matter also explores the multiverse concept, while Stuart Fails to Save the Universe, the recent spinoff from The Big Bang Theory, follows several familiar characters as they travel across realities to save their universe. Each uses some version of the idea that anything we can imagine is true in some alternate universe, and this article explores that common premise.
Rick and Morty’s cartoon metaphysics
Rick and Morty is a witty science fiction cartoon series that finds much of its humor by exploring the metaphysical implications of scientific theories. The episodes are fun and entertaining with plenty of dark humor, and although the stories sometimes get a bit absurd, they are at least vaguely plausible and consistent with the show’s sort-of-scientific premises. The show’s effort at consistency keeps it interesting and also invites analysis and critique of that consistency. In this case, I examine what I’ll call the show’s Every-Universe theory.
(To be clear, I don’t see pointing out something that I disagree with as an attack on the show or its creators. I’m a huge fan and I wrote this because the show got me thinking about something that I’d like to share.)
If you’ve never watched the series then the relevant context is that Rick Sanchez is an eccentric, brilliant scientist who has built a device allowing him and his grandson, Morty, to move between parallel universes. The premise is that there are infinitely many parallel universes and, therefore, that anything you can think of must exist somewhere among them.
Early on in the series this idea is used as the ultimate way of fixing things that go horribly wrong. When one of Rick’s inventions inadvertently turns everyone on Earth into blob-like monsters from a horror film, the solution is to find another universe where a) Rick did not screw up and turn everyone into monsters, and b) where Rick and Morty have just been killed in an accident. The Rick and Morty that turned everyone into monsters just pick up and move to this very convenient alternate universe that has a place for them. They bury their alternate selves’ bodies in the backyard, and carry on in their place as if nothing happened.
A multitude of parallel universes
This infinite multiverse idea ends up getting used a lot in the series. At one point Rick ends up in a universe exactly like ours, except that everyone is a Nazi fascist, implying that in that universe Hitler was not defeated in WWII or something along those lines. Nazis are evil, things go badly, and Rick ends up in another universe where people are still Nazi fascists, but instead of being humans like us, they are giant talking shrimp people. It sounds silly, but remember the premise is that there are an infinite number of parallel universes, so for any crazy thing you come up with, no matter how bizarre, then according to that theory there must be an alternate universe where that crazy thing is true and normal.
This idea that every imaginable universe exists is a fun trope for the show, but I don’t think the show’s interpretation is consistent with its own multiverse premise. In the popular many-worlds interpretation, when a quantum event has several possible outcomes, all of those physically possible outcomes occur in different universes that branch off for each possibility. That principle suggests that every physically possible outcome occurs somewhere, but it does not imply that every universe anyone can imagine must exist. For a particular something to exist in some parallel universe, there needs to be some possible path through time where that other universe starts with its Big Bang and then, following whatever the laws of physics are in that universe, the things that could happen do happen, and that universe ends up in a configuration which includes that particular something. In other words, there must be some series of events that could take place that would lead to a universe being as imagined.¹
Consider the example from the show of having a parallel Earth that is just like ours, but everyone is a Nazi. In that universe, I don’t think I’d have been born, so how would there be a parallel me? My mother is Iraqi and she moved to the US in the 1960s to escape the Arab Socialist Baʿath Party that was taking over Iraq. It is hard to imagine that Nazis would allow a non-Aryan Iraqi to immigrate and then go to law school. Furthermore, the reason my mother came to the US instead of some other country is because her sister, my aunt, got married and was living in the US. However, my uncle, in addition to being a warm and jovial person who I miss, was Jewish. A universe exactly like this one, except for the one single difference being that our parallel selves are all Nazis, is internally inconsistent.
Preserving universal consistency
If just one single difference would lead to inconsistency, then maybe we can start making some additional changes to restore consistency. Perhaps my uncle in that parallel universe was not Jewish, or maybe the alternate universe Nazis were more humane than the monsters in our universe and didn’t murder millions of people. For any objection to the consistency of an imagined universe, it seems we can always change something else and make the problem go away.
However, notice that each time we change something to fix one inconsistency, we typically end up introducing more inconsistencies which then need to be fixed. We cannot just change one thing, we would have to change a lot of things to make our imagined alternate universe internally consistent. In fact, by the time we would be finished fixing all the inconsistencies it would be hard to recognize any parallels. You might have a universe where the evil Nazis won WWII, but it would be very different from ours in many, many ways.
As an example that is perhaps more clear because it does not involve the fun, but confusing, concept of alternate selves, imagine a world very much like ours except that people walk on their hands, not their feet. Sure, it’s possible that in some other parallel universes primates would evolve to walk upright on their front rather than their rear legs, but evolution in that universe would continue to go in a different direction than ours. Those “humans” would not evolve to look like us. Their “arms” would be developed for walking and their “legs” would be developed for holding and manipulating things. There would also need to be some reason why literally having their heads between their legs was a better evolutionary strategy than having them up top where they could see things. I’d also imagine that their digestive and circulatory systems would need to have evolved very differently from ours. All of those differences would in turn create more differences in their biology, society, and pretty much everything. We can imagine whatever crazy things we like, but a universe with those crazy things can only exist if it is self-consistent.
A river metaphor of time
So how can there be an infinite number of parallel universes that despite being infinite still excludes the inconsistent ones? The answer is that you can have an infinite number of things without having all the things. For example, “all the positive counting numbers” is an infinite set of numbers, and “all the positive counting numbers, except those less than 5” is also an infinite set of numbers, but it leaves out 1, 2, 3, and 4. Another example is “all the positive counting numbers that are divisible by 10”, that is also an infinite set. Not only is it an infinite set, but the set of things it leaves out is infinite as well.² So being infinite does not necessarily mean including everything.
To see how this idea of exclusive infinities could apply to these hypothetical universes, imagine a shallow river that is infinitely wide. If you dropped a leaf into the water then it would follow some path with the water flow. Drop it in a different place and it would follow a different path, a different streamline. Because the river is infinitely wide there are infinitely many different streamlines.³
Now, imagine dumping a giant rock into the river. The rock is much bigger than the river is deep, so it sits there and the water needs to go around it. All the obstructed streamlines now bend around the rock and then come back together behind it. The river is still infinitely wide. There are still an infinite number of streamlines, but now none of them go where the rock is. Next, imagine that the rock is so big that it actually splits the river. Instead of coming back together behind the rock, the two flows split apart and go off in different directions.
Let’s also free this river from gravity. In addition to being infinitely wide, it is also infinitely deep and it flows through space like an infinite floating tube of water. If we thought of the original river as a two-dimensional flow on a surface, now we have a three-dimensional flow in space. Infinitely wide and infinitely deep, each streamline path flowing with the water is a metaphorical timeline for one out of an infinite number of possible universes. Each river starts at its respective Big Bang and flows on until the end of time.
We can still have rocks, or whatever we want to call them, that block off areas where no water can go. In fact, we can still split our stream into pieces and those pieces might go off in different directions or weave around each other like an infinite bunch of metaphorical hoses. They always flow forward, in the direction of time, but they can split, twist around each other, maybe even merge. Even with an infinite number of hoses there may be gaps or large volumes where no hose goes. Those regions are outside the flows.
If you imagine that every point in this metaphorical space represents some possible configuration of all the atoms that make up the universe, then we can see that some configurations can be reached by following a path through the flow, while other configurations are unreachable because they are outside the flow. The volume of the flow is infinite, the extent of the flow is infinite, but it still does not necessarily include everything. If there is no path of possibilities that leads to a particular configuration then it is outside the flow.
This is one way we could visualize a multiverse of alternate possibilities, except that it would be far more complicated than tubular flows in three dimensions. Even for a simplified universe based only on particle positions, this “river” would exist in a number of dimensions proportional to the maximum number of particles in the universe. The important point for the metaphor is simply that physically reachable states occupy only a constrained subset of a vast state space of possibilities.
Closing time
So here we are: We can imagine a multiverse that creates branch universes for all possible outcomes. This multiverse would have an infinite set of possible universes, but impossible things are still impossible.
Of course, Rick and Morty is a cartoon and this every-possibility-exists idea is not the only scientific aspect of the show that one might disagree with. Regardless, that’s not a flaw in the show as it does not present itself as an educational resource. The show is meant to be entertaining and if every possibility exists in the Rick and Morty multiverse, then it gives the writers artistic license to explore the impossible. If the writers stuck with only the stuff that is actually possible then I think the show might lose some part of what makes it so much fun. Imagining the idea that absolutely anything is possible is sort of appealing somehow.
Footnotes:
[1] One loose interpretation of quantum mechanics might imply that there is an incredibly tiny, but non-zero, chance that all the particles in our universe would just spontaneously rearrange themselves into any envisioned configuration. Even if that interpretation were correct, an unstable, inconsistent configuration would immediately diverge away from the envisioned state as time moved forward and chaos would quickly ensue. We could start making changes to reconcile any inconsistencies, but by the time we would be finished fixing them all, it would be hard to recognize any parallels to what was originally envisioned.
[2] Infinities are not all the same, which can be confusing. The number of positive integers is obviously infinite and the number of positive integers divisible by 10 (e.g. 10, 20, 30, …) is likewise infinite. One might think that there are one-tenth as many positive integers divisible by 10 as there are positive integers, but every positive integer can be paired with exactly one multiple of 10: 1 with 10, 2 with 20, 11 with 110 and so on. In the mathematical sense, the two sets therefore have the same size. This kind of infinity is called Aleph Null (ℵ0), or less formally referred to as “countably infinite”.
[3] In fact, because the river is continuous, the number of possible streamlines is not just countably infinite, it is uncountably infinite. Intuitively, the concept of “an infinite number of things” is distinct from “an infinitely wide river”. There are uncountably many possible streamlines, just as there are uncountably many points along a line. Georg Cantor developed the theory of different infinities. Initially, he was attacked by other mathematicians who found his ideas confusing and upsetting, but eventually his work was recognized as a profound and important contribution. David Hilbert famously said: “No one shall expel us from the paradise that Cantor has created.”
About Me: James F. O’Brien is a Professor of Computer Science at the University of California, Berkeley. His research interests include computer graphics, computer animation, artificial intelligence, simulations of physical systems, human perception, rendering, image synthesis, machine learning, virtual reality, digital privacy, and the forensic analysis of images and video.
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