The multiverse (or meta-universe) is a hypothetical set of various possible universes including the universe which we live in. Together, these universes comprise everything that exists: the entirety of space, time, matter, energy and the physical laws and constants that describe them. The miscellaneous distinct universes within the multiverse are called the “parallel universes,” “other universes” or “alternative universes.”

And from:


Many-worlds implies that all possible alternate histories and futures are real, each representing an actual “world” (or “universe”). In layman's terms, the hypothesis states there is a very large, perhaps infinite, number of universes, and everything that could possibly have happened in our past, but did not, has occurred in the past of some other universe or universes.

I’m using those definitions/explanations here because they put into words my thoughts better than I could right now.

So, let’s say we take the above described concepts as real, with those as a jumping off point I am trying to create a place, some point in space/time, where two of the universes from that infinite bunch (ours and another) are blending into one another without either being destroyed. Imagine these two realities are caught in the same space/time but instead of annihilating one another they are “blending”, mixing, and creating something new, something that is a little of both.

My sci-fi explanation of this is that an alien race with the tech to warp space time was conducting an experiment that they hoped would take them to one of those other realities. Instead it mistakenly brought another reality closer to ours, but not fully, so there’s “blending” going on at this point of space/time.

I want my space explorer characters to achieve some kind of understanding of what might cause this to be possible. Any thoughts?

I realize that some hand waving will come into play, but I want to give readers something that at least sounds plausible. Maybe something that scientists are really theorizing(?).

EDIT: Just adding some food for thought:

A) Dark Matter cannot be observed except we know its there because of its gravitational effects. So isn't that kind've like another dimension existing right here within ours without any annihilation?

B) Neutrinos can pass through matter because they have little mass and no charge. Couldn't something similar apply here?

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    $\begingroup$ If diverging realities spawn at every decision point then converging realities should also occur whenever the position, speed and vector of every subatomic particle in one reality exactly matches those of a different reality, despite their differing historic events. I should have used this to argue with my history teachers whenever we agreed on current reality, but differed on the specific historical events which lead us to the current moment. Unfortunately, this kind of convergence isn't what you are looking for. You want to merge two distinct worlds while keeping their differences. $\endgroup$ – Henry Taylor Feb 12 '18 at 18:34
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    $\begingroup$ Ignoring the physics (which is "can't be done" territory), a blend like that would create chaos and effectively destroy anything passing through the interface - randomize it at a sub-atomic level. The closest concept to what you're discussing would be an [EPR bridge](*en.wikipedia.org/wiki/Wormhole) ("a wormhole") and I'd suggest you adopt the same sort of (unrealistic) ideas for your interface as wormhole stories do. $\endgroup$ – StephenG Feb 12 '18 at 18:34
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    $\begingroup$ @Len Draw a picture of a ship, tear the paper up into microscopic pieces and scatter the dust randomly. Do you still have a picture of a ship? $\endgroup$ – Muuski Feb 12 '18 at 19:33
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    $\begingroup$ Let me put it this way : everyone else seems perfectly willing to write about these things happening, so why not you ? From a physics point of view I'd consider it nonsense which has not prevented me e.g. enjoying Stargate Atlantis. The trick to suspension of disbelief is to not get hung up on the details and fire through them to the rest of the story. Greg Bear's "Eon" and follow-up novels are kinda in your ballpark, but he doesn't really do more than paint-with-a-very-big-stick in terms of the physics. Just don't say "magic" - it makes me grind my teeth. :-) $\endgroup$ – StephenG Feb 12 '18 at 19:34
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    $\begingroup$ There will always be complainers! @StephenG doesn't like "magic," but I have no problem with it. On the other hand, if you misuse Quantum Mechanic's Many Worlds Interpretation, I will scream =) MWI is very specific, very precise, solves some amazing problems, but it's definitely not what Holywood makes it out to be =) $\endgroup$ – Cort Ammon Feb 12 '18 at 19:51

10 Answers 10


Fundamentally, you're not going to get into the subatomic physics of the blend. In fact, it's almost certain that if you tried, you'd get the physics wrong (since there is no physical version of this).

Thus, what you need is something that feels right and is useful to the story. Bonus points for physics based and slightly unintuitive.

My recommendation would actually be to look at supercritical fluids. Add heat to a liquid, you can boil it into a gas. Refrigerate a gas, and you can turn it into a liquid. Increase the pressure, and this effect happens at a higher temperature. We can draw what is known as a phase transition curve showing this effect at different places.

Phase diagram

Here we can see a phase diagram. You can see that, at reasonable temperatures and pressures, if you have a liquid and increase it's temperature, you can make it a gas. But what about that funny point marked "critical point?" This is where something funny happens. If you heat a liquid past this point, its molecules have so much energy that the structure assumptions we get to make about how bonds form in liquids just don't work. It's not a liquid. However, it's still too dense and there's too much intermolecular interactions to be treated as a gas.

At this point, we have a "supercritical fluid." It's a phase of matter all its own. It's not a liquid. It's not a gas. It's something else with some hybrid behaviors from both. Weird behaviors. Ever wonder how they make decaffeinated coffee? They raise the pressure on some CO2 until it goes supercritical, then pass it through the beans. I mean that: through. Supercritical CO2 can pass right through the solid coffee beans. It then acts as a solvent to pick up all the caffeine molecules, and passes right out.

You can add whatever quantum verbage you like. You can talk about resonance or interference, but if you really get into it, those concepts are hard for a reader to grasp. They're hard enough for a writer to grasp. However, the nature of supercritical fluids, and how they aren't just a summation of liquids and gases, is much easier to grasp.

It also creates room for a natural drama. As the temperature and pressure fall towards the critical point, the material is going to act more liquid like or more gas like, depending on how they fall. There's a natural winner-takes-all feel to this process that is easy to take and weave into some plot. While this supercritical quantum flux foam might be supporting both realities now, as it cools, it may begin to take on aspects of one reality or the other. That should be terrifying.

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    $\begingroup$ Well... You know what they say, if you boil an aquarium you get a fish soup, but if you refrigerate a fish soup you don't get an aquarium :-P $\endgroup$ – ChatterOne Feb 13 '18 at 11:47
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    $\begingroup$ Instead of supercritical fluids... supercritical realities?! But in this analogy what would be the equivalent of the heat needed to boil it past the critical point? $\endgroup$ – Len Feb 13 '18 at 19:00
  • $\begingroup$ @Len As far as we understand it, nothing causes realities to come together like you want. Thus, whatever it is that brings them together is going to be substantial. It's going to have to do some pretty spectacular things putting the universe(s) in a highly unstable state. A little energy for the analogy of heat should be a cakewalk for it. $\endgroup$ – Cort Ammon Feb 13 '18 at 20:03
  • $\begingroup$ I'm not so sure. There are numerous occasions where I have set something down, spent hours looking for it, only to find it precisely where I thought I left it. My working hypotheses is that the keys and I (keys are the most common item) went into different realities, then came back. $\endgroup$ – Sherwood Botsford Feb 15 '18 at 21:07

It seems like you're trying to bend the rules on causality, or rather you're trying to blend two points that have no common cause into one.

Paraphrasing the definition of causality: an effect cannot occur from a cause not in it's past light cone, and cannot cause an effect outside it's future light cone. A light cone is essentially the cone of all possible paths that a photon can take through spacetime. In other words, a light cone represents all possible effects that a cause can have, because the effect cannot reach outside of the cone without traveling faster than the photon/faster than light.

I don't have enough physics doctorates to go into the math on why what you want is physically possible or impossible. However, I can roughly describe what would need to be possible for what you want to happen:

Imagine you are looking at the light cone of an event coming toward you, i.e. you are looking at the base of the cone which looks like a circle. If the event that made that cone could have produced a different effect, i.e. created a different universe, and was also coming at you, then the two cones would look like a Venn diagram.

The common parts of each universe are in the overlapping center of the two cones and are already 'blended' because they came from the same event. The edges, however, are the differences between the two universes and are what you want to blend together in your weird non-causality world. Therefore, the sci-fi alien hand-waving-the-non-fun physics explanation for blending two universes is simply blending two non-overlapping light cones into one, thus bending the rules of causality. Essentially, things just need to happen without any event causing them to happen.

  • $\begingroup$ More like the two cones diverged from the same causal point and then re-merged later on. So that some changes that happened in the one are not reflected in the other. The weird alien hand wave tech makes them re-merge in this one point in space time. $\endgroup$ – Len Feb 12 '18 at 21:48

Note: Quantum anything is odd. Don't take my word as law. Look to the comments and to other answers for reasons why this is impossible. I'm simply here to describe a possible course of action.

Let's look at the base idea: Two universes diverge at a single point, and the differences ripple out at the speed of light.

Slice through a Minkowski diagram of my life

Suddenly, these two universes are literally overlapping. The base volumes of space randomly flips between the two universes as they merge. For most of the observable universe, nothing would be wrong. Since each universe has the same contents, randomly flipping between them shows no difference.

The issue comes in when you're less than $c*\Delta t$ from the event. In this case, you're inside the light cone, and are affected by the merger.

Suddenly, the basic units of matter are flitting in and out of existence. Affected by the diverging causalities, atoms that would have been in one place are in another place, leaving gross problems occurring all across the light cone. These interactions effect more change, leading to a slurry of the two universes that is completely uninhabitable by standard physics.

You can't outrun the growing bubble of problems. You don't even know it exists. It is literally the fastest growing bubble of death that could possibly exist. By the time you know it exists, it is upon you. The only recourse is FTL, with its own host of problems.

Inside the problems bubble, though, things begin to settle out. It's still a slurry of probabilities, but with the two universes interacting at the level of the basic forces acting on matter, they eventually resonate into alignment, becoming effectively one universe again.

Unfortunately, there's still a giant front of death expanding across the universe as the two universes reconcile their differences.

Now, this isn't even remotely possible. We have no real systems that could 'un-collapse' a quantum waveform, and the base tenets of many worlds exclude this scenario.

  • $\begingroup$ You're a genius! Even though you're saying that it cant work (right?) that actually still helps with my story, because in it the reason why the aliens hope to escape this reality is that a large wave of destruction is coming towards them! I'm not kidding! This is great. So that wave of death you describe, where/when would it be emanating from? $\endgroup$ – Len Feb 12 '18 at 19:27
  • $\begingroup$ Look at Giter's explanation of light cones. Basically, it's the fact that information from an event (and the reactions therein) can only propagate at the speed of light. Unfortunately, this isn't very conducive to plot, as nothing can go faster than the speed of light. When you learn about it, you can't send information to someone outside the effect because to get the information to them, it would have to go faster than the effect, and it CAN'T. $\endgroup$ – Jakob Lovern Feb 12 '18 at 19:34
  • $\begingroup$ The wave of death is caused by differing causality. Basically, in one reality, you drop a fork, and in the second, you don't. Via butterfly effect, dropping your fork causes the sun to explode. These unknowable chain reactions move things in space, causing dissimilarities between the two universes. $\endgroup$ – Jakob Lovern Feb 12 '18 at 19:39

I don't really understand causality. Jakob Lovern seems to be suggesting that when it blends, the same matter can't be in two different places possibly causing massive damage(who really knows and I'm not sure I understood his point). Giter seems to suggest that you just need to focuse on differences because the things that are the same can already be considered blended, how you blend the differences, having both, part-n-part or only one is up to you.

I wanted suggest a different route where the nothing is blended, everything becomes duplicated (kinda) instead .

You can consider this idea is that many universe share the same space and are only seperated by a fragile glass that prevents them from affecting each other. Once the aliens make a hole in the glass, the matter of the two universes start to affect each other through gravity, this puts even more stress on it until the cracks go from the epicenter to all throughout the universe(This could happen fast or slow and the barrier near the center is probably long gone by the time the cracks reaches the edge). This would probably destroy the structures in the majority of the universe but there is possible that some galaxies might not be too affected as they werent aligned with anything on the otherside.

Ofcourse as the only survivors would probably be in the places nothing interesting was happening, it might not be the best story setting but I still had to say it. Another reason I like this idea is that it could show that the big bang could have expanded into to each dimension at the same time and not that it existed in both dimension, which could show that the big crunch is only likely to happen if more dimmensional barriers are broken, as one dimension will have more mass.


I'd suggest dropping multiverse and accomplishing your task through another mechanism entirely.

The interactions between particles are governed by the fundamental forces. (Gravity, EM, Weak, and Strong are to our knowledge what's going on at room temperature.) The influence of the fundamental forces is goverened by coupling constants, like the electron's charge. Without the coupling, the forces don't do anything.

So, let's say that all along there has been an entire other universe (overlayed on the same space), with an extra set of forces, and an orthogonal set of charges. Their positive and negative would look neutral to our electromagnetic force, and our positive and negative would look neutral to theirs (extend this to the other forces). We'd be like a ghost to them, and they a ghost to us. Something happens that causes the charges to start changing: suddenly, a block of matter from our universe acquires their kind of charge and looses our kind of charge. Somewhere else, it happens in the other direction. A naive observer would think that the chunks were "teleporting," between realities, but they wouldn't have to move at all.

Extra work: what happens if the matter ends up with both universe's associated charges? Neither?

(If neither, it would all fly apart as the bits and pieces would have thermal and degenerate energy, but wouldn't exert confining forces on each other any longer!)

  • $\begingroup$ I'm loving this answer... So what the alien hand wave tech is doing is shifting the coupling constants from ours to theirs intermittently? $\endgroup$ – Len Feb 13 '18 at 18:32
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    $\begingroup$ Yes. There is no experimentally supported theory that explains how the couplings and charges/flavors/colors are set, so you could write anything you wanted without contradicting present-day physics. $\endgroup$ – Display Name Feb 13 '18 at 19:32
  • $\begingroup$ Wait.. isn't this kinda like the 'out of phase' trope? Only instead its like two phases. Though you could argue that different universes actually run on different wavelengths. I think that in some stories you can tell people apart on what wavelength they are. $\endgroup$ – Necessity Feb 13 '18 at 23:58
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    $\begingroup$ The effect is similar, but bear in mind that phase and wavelength both have meanings in physics that couldn't be farther from what was intended. $\endgroup$ – Display Name Feb 14 '18 at 1:20
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    $\begingroup$ Neutrinos couple weakly (in both senses of the word: through the weak force, and also they don't couple that much in the first place.) So, yes, they are quite similar: just take the couplings that are already very low for them and bring them all the way to zero for the ghost universe's matter. $\endgroup$ – Display Name Feb 16 '18 at 21:45

Large wormhole?

People use think of wormholes as giant doors, but in general relativity, there more like a place that two points in the universe, or even two different separate universes, are "glued" together.

In fact, if a wormhole was large enough, you may not even notice is it there (besides all the exotic matter in it, but there will probably be exotic matter outside it as well).

So, if you are near the wormhole, some directions naturally "lead" into the other universe. This might lead to blending if someone has blenders in the wormhole.

If you just want to connect to different points in time, any Closed timelike curve (of which wormholes are just one variety), would work. They allow the future to be near the past in a wide variety of ways.


The multiple universes are just different simulations. A programming error, or CPU overload could break down the separation

memory leak or space leak: https://en.wikipedia.org/wiki/Memory_leak

Also, it allows use of exploits that would allow travel to other universes

  • $\begingroup$ I do like this answer, but I was hoping for something that would happen IRL instead of as a computer simulation. But thank you. $\endgroup$ – Len Feb 20 '18 at 20:55

Imagine multiple more-or-less parallel tunnels in a cave system, or through a mountain.  The tunnels aren’t perfectly straight; they meander enough that sometimes two of them come very close together.

  • If the wall between them gets down to 1 cm in thickness, it may be possible for the occupants of one tunnel to hear sounds from the other.
  • If quartz and/or other transparent / translucent rock are present, it may be possible for the occupants of one tunnel to see events in the other.
  • There could be a hole in wall, allowing matter to move between the tunnels.

Do this in a handwavium mine, and you’ve got parallel universes.

You should look at the “Apprentice Adept” series by Piers Anthony.  It takes place in two parallel universes that have limited points of contact / overlap.  He doesn’t explain how this came to be;

  • it’s treated as a feature of the multiverse that has always existed.
  • magic works in one of the universes, so there’s not a lot of technical exposition.

But he does explore the concept of inter-universe contact.


Mirror matter: https://en.wikipedia.org/wiki/Mirror_matter

This is NOT anti-matter. But another set of particles that effectively only interact gravitationally with our visible universe. One of the serious proposals for the missing mass problem.

See also John Cramer's novel "Twistor"
It's only a ho-hum novel, and will remind you of the pulps of the 40's. But Cramer is a working physicist.

Finally getting back to the parallel universe, take a gander at 'renormalization' in particular. Start here:


The idea is that for any given quantum interaction there are a multitude of "it could have happened this way" and the actual outcome is the superposition of all the other possibilities.

So your parallel universes are constantly in the process of spliting and merging. The length of time it takes to merge is a matter of both balance and scale.

This has some explaining power: The car keys that are on the kitchen counter but weren't there 10 minutes ago are the merge of two universes. Some of the times that your memory of an event is totally different from someone else's memory is the result of merging.

It also gives you a neat response to one problem of multi-universes: If everything is possible, what is the point of making a good choice? Yes, you need more hand-wavium to make it work.


Imagine the universe as Einstein's trampoline, with each universe being its own trampoline.

Go to a point on your trampoline where it's just like the trampoline of your target destination - probably (but not always) a really long way from a gravity well, where both trampolines are almost flat. If there were two identical solar systems, you might be able to do it in a gravity well.

Blast off a shitload of energy. Like, infinite heat levels of energy, where the rules of physics start to get really weird. You can punch a hole through your trampoline and their trampoline. You can even cauterizing the edges to keep it open.

Now you can travel between universes.

  • $\begingroup$ 2 issues... A) a shitload of energy sounds like as big a problem as the one we're trying to solve, and B) if you punch a hole and cauterize it to keep it open (a wormhole I assume?) wouldn't matter from each reality seep into the other, and thus annihilation? $\endgroup$ – Len Feb 13 '18 at 18:28

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