Over time I did actually manage to assemble theories to support large parts of what happened with dreamwalking. I gave Jenna some dumbed-down (that is, not for physics majors) versions of a few relevant concepts and then in one of our dreamwalks together in World of Dreams I went over the theories with her.

“I actually have a good explanation now for a lot of what we do and experience. There are still gaps, but some of your ideas helped before, and I hope you can help me again.”

“I’m all ears,” Jenna replied.

Theory 1: We live in a branching multiverse. Certain events cause a universe to branch into two universes (both part of the multiverse) which are alike except for details of that event, but the differences gradually spread due to interactions of the parts of those universes which differ with other parts of each universe.

“I shared with you the branching multiverse theory, which is one of several unproven theories, thought to be unprovable, which other scientists have proposed to explain what might exist outside the universe. But I know it’s true because I have visited some of these other universes, ones that follow the history of our universe up to a point and then diverge.”

“Right. You told me the very first place you dreamwalked was like that. Go on.”

Theory 2: Dreamwalking is based on quantum entanglement.

“When we dreamwalk, we interact with other places far from here, instantaneously. If that’s on the other side of the Earth, at the speed of light through the Earth’s core, that’s about 1/20th of a millisecond each way. We might not notice that lag. But we dreamwalk into other universes. How far away would that be? We don’t even have a way to get there, apart from dreamwalking. This is perhaps the weakest part of this whole argument, but the only kind of mechanism science offers that can possibly communicate in this way is one involving quantum entanglement.”

“The thing where a particle has two possible states, but a distant particle is correlated with it, so when one particle is forced into a state, the other instantaneously assumes the corresponding state?”

“Yes, that is what I mean, Jenna.”

“I don’t have a better explanation. I’ll take this one for granted. What’s next?”

Theory 3: The event which causes one universe to branch is the breaking of quantum entanglement.

“While you have this idea in mind about pairs of particles which can have either of two correlated states, which resolve instantaneously, in cases like the physics experiments where the particle could go either way but it is forced to go only one of the two ways, I propose that what really happens when entanglement breaks is that the universe splits into two universes, one in which the particles have one set of values and one in which they have the other.”

“It’s an interesting thought.”

“I tested this by watching, from my select-a-dreamwalk state, one of the researchers running one of these entanglement experiments, and specifically how many worlds he existed in. Even before the experiment started, he already existed in thousands of universes, but while the experiment was running this number fluctuated wildly, increasing more than it decreased. The fact that the number of universes containing the researcher did not simply double for every entanglement break shows that there is something else going on, but the fact that it changed wildly while the experiment was running and much more slowly when the experiment was not running shows that it was related to the experiment.”

“Neat! So it was like a meta-experiment?”

“You could say that. Though it was something nobody else could confirm.”

“Right. You mentioned that’s why you were sharing it with me in detail.”

Theory 4: Free will is powered by entanglement, specifically, a power our brains have over entanglement.

“For millennia, people have debated what free will actually is, in modern times crossing from philosophy into the fields of biology, chemistry, psychology, and others; basically into everything I studied. With a multiverse with branching powered by the loss of entanglement, the only thing that makes sense is that our brains possess the power to manipulate entanglement, and decisions and their impact upon the world happen by means of whether particles within our brains do or do not stay entangled.”

“Wow, that’s a big one. But I can see how it follows from your other assumption about entanglement-breaking being the pivotal event that separates two universes.”

Theory 5: Matter in our multiverse is heavily entangled to the extent that any macroscopic clump of matter contains particles entangled with other particles in every other macroscopic clump of matter.

“This follows directly from theory 2 and my own observations. I can dreamwalk into any person in any of these worlds, apart from a limited few who have developed a way to shield themselves, so I must possess particles entangled with them all.”

“Right.”

“Now this has a big consequence. It must be the case that entanglement doesn’t only happen in the way physicists set up experiments, which I call experimental entanglement. In fact, every time two particles interact it imposes certain limits, certain combinations of properties those particles may not have, leaving certain other allowed combinations, and resulting in the particles becoming entangled. This entanglement may leave multiple allowed combinations of properties, not only two, so it may take multiple future interactions before entanglement fully breaks. The brain uses particles entangled in this way and not just those from experimental entanglement, which are quite rare and only exist in modern times.”

“Of course.”

Theory 6: When a universe splits, particles within it become entangled with their other-universe equivalents.

“Another consequence of theory 2. I can dreamwalk into other-universe people as easily as ones in this universe. But particles from our universe do not interact directly with particles in other universes, so that entanglement must be set up at the time the universes split.”

Jenna nodded and I went on.

Theory 7: Entangled particles can pass entanglement to other entangled particles.

“This is another more subtle consequence of theory 2. I have a connection to essentially every person on Earth. We know that particles in Earth’s atmosphere circulate and recirculate, but they don’t do so fast enough. A little story is relevant here.”

“Do tell.”

“It’s been said that with every breath, we breathe in atoms from Julius Caesar’s dying breath.”

“Is that really true?”

“It’s arguably true. There are an astronomical number of particles in any macroscopic amount of matter. The ideal gas law tells us that in ordinary conditions in Earth’s atmosphere, one mole of gas occupies about 23 liters. A mole is a way of measuring the number of particles; it’s defined by the number of atoms needed to make up the atomic weight in grams. A mole contains about 6x10²³ particles. That’s 600 thousand million million million particles. A breath is only a couple liters, not 23, so divide that number by ten to get about 6x10²² particles in a breath. The entirety of Earth’s atmosphere contains about 3x10¹⁷ moles of gas. We can again say each mole represents about ten breaths, so that’s 3x10¹⁸ breaths. Some of that gas is up in the upper atmosphere and isn’t breathable, but that doesn’t matter for these calculations. It all circulates, and over the thousands of years since Caesar walked the Earth, we can assume it has evenly mixed throughout the entire atmosphere. But when you divide those numbers, that makes about 20000 particles from Caesar’s last breath in every breath of gas on Earth. And those atoms don’t all stay in the atmosphere; organisms breathe them in, and incorporate some of them into their bodies, which may become part of the land when they die, but enough of them stay in circulation to make the saying still true.”

Jenna nodded again.

“The problem is this thing called diffusion. It takes time to mix. There has been plenty of time since Julius Caesar’s era, but it takes years for air to mix across the Earth. The jet stream helps, but only so much. And not all the air that goes into my lungs is going to do anything to become entangled with me. I did some calculations and determined I would need more than 50 years to expect to have particles that reacted in my lungs reach 99.9% of other people on Earth, and react in their lungs. (And I think my coverage in terms of who I can dreamwalk into on Earth is even more than that.) I used the air because it circulates far more than any other matter that has a chance to get directly entangled with me. The circulation through water and the food chain is so much less it essentially doesn’t contribute. Since I’m still not close to 50 years old, nor are many of the people I can see as choices to dreamwalk into, it must be the case that entanglement doesn’t require direct interaction with my body. The reasonable choice is transferred entanglement.”

“OK. How is it transferred?”

“Suppose particles A and B are entangled until particle B interacts with particle C. If C is free in a certain way, perhaps because it is entangled with D, it may happen that A and B cease to be entangled, and B adopts a specific state, but A becomes entangled with C instead. It’s possible this causes C to cease being entangled with D, but it’s also possible that you instead get a more complex entanglement of the three particles (A, C, and D) with more possible combinations of states. But in either case, even though A never encountered C, it’s now entangled with it. This allows entanglement to spread quickly enough through the atmosphere to match my observations.”

“But you can’t prove there’s not some other way the entanglement happens?”

“Maybe the mechanism is different, but even so, the result is the same. The result isn’t critical, anyway; this is really just a side-effect of theory 5.”

Theory 8: Fictional worlds exist via the mass entanglement of the same ideas across many people’s brains.

Before I could even comment, Jenna interjected, “Right, we can dreamwalk into fictional worlds.”

“Fictional worlds exist in some sense, because we can dreamwalk into them, but they don’t work in the same way as real ones. They can’t. For one thing, we can simply make them up, in ways we can’t with real worlds. This theory is a way to try to explain their existence, in a way that I could prove, at least partially.”

“Oh, I want to hear this proof.”

“The fictional worlds we dreamwalk into are well known ones that at least a hundred thousand people are familiar with. Is there a limit? Is there a minimum number of people who need to know about a fictional world to make it real in this sense?”

“Good idea! So you tested it?”

“Yes. First off, I wrote a story about 20 pages long describing a unique fictional world with some unique characters which nobody else has seen. I could not dreamwalk into my characters even though I knew them very well as a result of having written the story. And then I shared it with you. It was that one from three weeks ago, that we discussed a while after you had a chance to read it.”

“Well now I know why you wrote the story.”

“Even after that, I couldn’t dreamwalk there. So I tried to make a list of stories I knew from books, TV shows, random reading on the Internet, etc. which weren’t especially well known. Where they were commercially published I tried to get some estimate of readership. I tried to visit about 100 of these. Most of the commercially published ones which were at least well known enough to have articles in Wikipedia that weren’t just stubs, and even some of the stubs were reachable, but some of the pretty obscure ones weren’t.”

“So that proved it.”

“Or at least supported it. But there was a second category of works that couldn’t be dreamwalked into that didn’t fit the criteria of being known by many people. Some further research showed that it has to be developed to a certain degree. For instance, even though that Far Side comic where the kid going into the gifted school tries to push a door labeled ‘pull’ is known by many more people than some of the works I dreamwalked into, I couldn’t dreamwalk there, because we know absolutely nothing else about the place.”

“OK, so well known and developed enough to be a meaningful place.”

“I even realized I already had evidence to support the theory. Hiroshi couldn’t dreamwalk into World of Dreams until he was able to start selling it to real players. This was the same thing; the fictional world didn’t have its own reality until enough players were thinking about it.”

Jenna laughed. “Right there under your nose.”

“There’s one more thing of note. We can’t dreamwalk into the major characters in fictional worlds, the ones everyone knows, because controlling their actions would require overriding the entangled memories of the many people who know the place. But it’s possible to dreamwalk into minor characters, the kind of people who show up in stories whenever a one-time character is needed, or in video games, player characters, whose actions necessarily vary from one game session or one player character to another.”

“That makes sense.”

Theory 9: Fictional worlds are subworlds of the worlds which created them. They don’t split on their own, but do so when their parent worlds do.

“If fictional worlds didn’t split when their parent worlds did, then we’d have people from different universes interacting in the same fictional world, and events from other real worlds influencing our fictional ones, in ways that don’t happen in actuality. I’ve seen some of the major events that happened in some of our near parallel universes, and the differences it caused in some of their fictional worlds as compared to the counterparts we have.”

“You have shown me some of those.”

“Indeed. And if fictional worlds split at times when their parent worlds didn’t, we’d have fracturing of the worlds.”

“But doesn’t that actually happen sometimes? Like when somebody goes and makes a major retcon to established work, people still remember the old version.”

“Yes, it does. But the fictional world doesn’t split because of the kind of quantum interactions within the world that cause universes to branch within the multiverse, but because of outside influence on the people whose minds support it.”

“Fair enough.”

“Oh, but I can show you. They aren't always even called the same thing, for instance Pigwarts isn't always called Pigwarts, but it's easy to find them across a vast swath of other worlds. I even found one crazy world where the author never revealed within the books that the head of Pigwarts was gay, but announced it on the Internet after the books were finished.”

“What? Why do such a thing?”

“The books were already too long and it got cut as an inessential element, apparently. On that Earth, in the mainstream dreamwalkable version of the world he was a closeted gay all through the series, but he never dated any other major character, or those characters died taking the secret with them, and nobody at the school knows. There are gay and lesbian kids at the school you can dreamwalk into, though, and they're out and accepted. But the announcement also sparked fan fiction authors to write a bunch of completely gayer-than-gay versions, some of which are popular enough you can dreamwalk into them. There's one where being gay or lesbian is mainstream within the magical world, they use magic to have kids, and the one straight couple at the school causes a controversy.”

Jenna doubled over laughing.

“Take me there sometime. I am not sure we could manage to have a real date there, but I'd love to see it."

“OK. Here's my next theory.”

Theory 10: The alternate versions of a person I can see when selecting dreamwalk targets are those who are strongly entangled with one another.

“This makes sense given that I see people from Earth in other worlds that are very similar to it and diverged more recently. When a universe branches, corresponding particles in the different universes become entangled. But not all of them, and some of them do not stay entangled over time, leading to the people no longer being recognized as the same after enough time has allowed enough differences to build up. Now that said, I think that in most cases I can still see those people; they just aren’t recognized by the weird interface in my head as the same person.”

“Yeah, I still don’t have that interface.”

“Hiroshi didn’t either. But now we’re at the brainstorming point. I’ve got a corollary to that last theory, but I am unsure how to explain it.”

Theory 11: Dreamwalkers are not entangled with their selves from other universes at all.

“This seems to be true, since I have never been able to see other instances of me, Hiroshi, or you. But it also can’t be the case that we don’t exist at all in other universes. It would cause too much of a cataclysm when universes split.”

“I agree. So where are our other selves?”

“Well I had an idea.”

Theory 11A: Dreamwalkers other selves are entangled with one another, but not with the dreamwalker. They lose the ability to dreamwalk, forget that dreamwalking ever existed, and whatever consequences of dreamwalking exist in their lives simply become mysteries to them.

“Ugh, really?” Jenna interjected.

“Well, I said it was an idea. But I agree I don’t like it because it still seems to impose massive changes on any world that branches off one with a dreamwalker. I tried to test it, by going into various other worlds and looking up you and me by normal means rather than through the thing in my head. I found us, sometimes. We were never together, though, and it was clear that my counterparts in those worlds had never dreamwalked, not at all. World of Dreams didn’t exist in most of them, but I found it in some, which was something I wasn’t able to do before with Hiroshi. However, I didn’t find worlds that had branched off from our world more recently, where I’d been playing World of Dreams and gotten together with you. So I think that’s not it. And I hope you can come up with something better.”

We brainstormed various ideas for a bit, and then Jenna proposed a new idea.

Theory 11B: Dreamwalkers have counterparts who dreamwalk, but dreamwalkers may not dreamwalk into the home world of another dreamwalker, unless the dreamwalker also originates from that world.

“Interesting, Jenna. So there may be millions of us out there, none of us able to visit the home worlds of any of the others, and I can’t see them because I can’t dreamwalk into anybody within those worlds.”

“Wouldn’t this, however, conflict with the researcher you mentioned?” Jenna asked.

“Oh, the particle physicist I mentioned back when we were discussing theory 3? Actually, no,” I confirmed. “I hunted around different universes to find one where a quantum entanglement experiment was happening just then. It wasn’t in our world. If we find one happening in our world, maybe we can check what happens when someone does it here. If the theory is right, we shouldn’t notice any difference when the experiment is happening versus when it is not happening, because the copies produced will all be in worlds I can’t see.”

“Unless the experiment is also happening in worlds without you but with this same physicist,” Jenna pointed out.

“Sure. I’d have to check that. But, oh, it also explains my family members!”

“What?”

“They also only exist in a single copy, but their other copies are in the worlds with the other versions of me.”

Jenna agreed, “That makes sense. Is there some place you dreamwalked that your other selves would have visited also?”

I didn’t have to think long to come up with my answer, “Tommy.”

“Your first accidental dreamwalk?”

“Yeah, or the real world containing it, since he finished the game a long time ago. We communicated by me inhabiting Tommy’s body and exchanging notes. I can just go look and see if I was ever there since the last time I visited.”

“Go ahead,” Jenna told me.

I got out of game-Sarah, and went to Tommy. Although he and Becky now lived elsewhere, together, they’d saved all the paper we’d exchanged notes on, now yellowed, tacked up on the wall, ending with Tommy’s last “Thanks, Sarah” note. There were no notations within the two stacks of paper that I didn’t remember writing or Tommy or Becky writing in response to me. I put Tommy back to bed and returned to game-Sarah.

“Nope. There was no evidence anyone else had ever visited Tommy.”

“What if you all had visited him at the same time?”

“What, all of us in his head at once? I’m sure I would have noticed, even if we were trying to do the same thing. No, wait! We would have caused Tommy’s world to branch, each instance of me occupying a different one of Tommy’s, doing the same or similar things. And I never looked for other instances of Tommy’s world, just followed my way back to the one I knew. Hang on.”

I went into the dream selector, and sure enough, there were over three million Tommys. Back to game-Sarah.

“Yes, Jenna, that’s it! There are over three million Tommys in different versions of his world, way more than I ever saw of another person. That probably means there are three million mes that visited him just now. Well, maybe not all of us at this exact moment, since we didn’t necessarily stay in sync. But we’ve done so.”

“What if I visited Tommy? What would happen?”

“I don’t know. Something good to try.”

I explained Tommy’s world to Jenna in the way I’d help direct her to other worlds when we didn’t dreamwalk together, and she took off, returning about 5 minutes later.

“Can’t say I noticed anything interesting there,” she said upon returning.

“We’ve dreamwalked together when I let you follow my trail. Let’s try that and see if you see the same thing. You can go into Becky, who should be in the same room with him.”

“There wasn’t anybody when I was there.”

“Huh. I guess you did visit a different Tommy.”

Moments later we were both there, me in Tommy and Jenna in Becky.

Jenna said, “Yes, this is totally different. Tommy was in a different, smaller room.”

I described Tommy’s room in his house with his parents and Jenna confirmed it.

“The Tommy you visited never got out of his parents’ house. Part of my interaction with Tommy got him together with Becky, who lived next door to him. Your Tommy probably never dated her. But now I realize that I didn’t help ‘Tommy’ per se, but the version of Tommy I created when I entered his world.”

I showed Jenna papers on the wall and recounted my experiences in this world. Then I left them a short note before we left this world.

We considered theory 11B partially confirmed, and it would be more completely confirmed when we found someone doing one of those entanglement experiments in our world.

Jenna came up with one more theory after that.

Theory 12: Dreamwalkers can enter the fictional worlds belonging to real universes that they have access to.

“That makes a lot of sense. I have dreamwalked into Tommy’s world and a number of others, and I have dreamwalked into games from some of those worlds as well. Is it strictly true? Hard to prove. I have some other hard-to-prove ones.”

“I’m all ears,” Jenna replied.

Theory 13: Characters in fictional worlds cannot actually dreamwalk.

“What have we been doing in World of Dreams, then?” Jenna asked.

“It’s a detailed simulation, which Hiroshi designed and refined over many years to reflect his knowledge about dreamwalking, but most of it is only a simulation.”

“Which parts are real?”

“Shielding, for one. In Hiroshi’s records were details of how he developed shielding only after he started selling the game and was able to dreamwalk into characters there. He was able to figure out, with a lot of trial and error, how to set up a character’s mind so that he could not dreamwalk into it, and he made dreamwalking within the game respect the same limits. And he was able to figure out how to do it in the real world by learning what a shield looked like when he dreamwalked into a game character and managed to set up the same sort of blocking state in that character.”

“OK. Anything else?” Jenna asked.

“The part about learning to induce sleep and dream states. This is actually a thing in the real world that predates World of Dreams, but is obviously relevant. And dreamwalk detection, another thing Hiroshi was able to have game characters do initially based on his own dreamwalks into the game. Everything else is designed so that when you dreamwalk into a game character, it will behave the same way it does for a dreamwalker in the real world, to the limit of Hiroshi’s knowledge, but those characters aren’t actually dreamwalking. They would fracture the game world in ways that don’t actually happen if they did really dreamwalk into the other game characters.”

Theory 14: Dreamwalkers can bring items with them into or out of their dreams. This is catalyzed by their entanglement with the target. If the items are transported between real-world locations or into a fictional world, their existence in the real world supports their continued existence. Items can also be transported out of fictional worlds and into the real world, but these items are unstable, and only continue to exist while they remain close to the dreamwalker. Otherwise, their connection to their origin is lost and the objects fade back to their world of origin.

We knew well the phenomenon of transporting items with us in an out of dreams. We didn’t have a solid explanation for why it was even possible, but this was a statement of our observations.

Theory 15: Just as certain states of subatomic particles admit exactly two particles with opposite spins, a world admits exactly two dreamwalkers at any one time.

This was easy to disprove if we ever found a third on Earth, but difficult if not impossible to definitively prove. We’d have to understand more about the actual entanglements of dreamwalkers.

We also discussed how it was a consequence of these theories that characters in World of Dreams couldn’t actually dreamwalk into the real world, and their dreamwalking into other characters within their own world was simulated. Real dreamwalks from these characters would have caused branches in the universe which conflicted with the theories.

---

Jenna and I returned to read Tommy and Becky’s response the following night, and it was a long one. They told us a lot about their life, which was good to catch up on. They were also confused and thought I’d permanently taken over the body of some man in order to marry Jenna, so in my reply I explained how we have same-sex marriage on our world, and we live together in our original bodies, both women.

We found one of those entanglement experiments happening on our Earth a couple weeks later, which gave me plenty of time to scout around for other possible worlds I could access where the man running the experiment existed. The experiment wasn’t running at the same time on any of those worlds, and indeed it didn’t affect the number of worlds he was in that I could reach. The new universes that sprouted out of this were all hidden to me. This provided the final confirmation for theory 11B.

I arranged another meeting with Jenna in World of Dreams to discuss the results.

“I’m glad you were able to confirm my theory, Sarah. But what’s the next step?” Jenna asked.

“Probably for me to keep looking for ways to confirm theories 12 through 15. Together with 11B, they would mean we basically have nothing to worry about; no malicious dreamwalker from elsewhere can invade our world, and no other one can arise while we both live here. It also means we can’t sneak information from the other worlds most like ours, making certain ways of using our ability to gain power or profit more difficult or impossible. I think there are still plenty of ways to do that which work, but just like Hiroshi, I’m not really interested in exploiting that aspect.”

“Hey, what if we write our own world to dreamwalk into?”

“That’s a great idea, Jenna. Let’s devote one night a week to brainstorming ideas for what kind of world we want until we agree on something.”

So we did that, and I kept looking for other dreamwalkers and ways to prove our loose ends. I never found them, but after a few years we published a novel. The book wasn’t a great success, but got enough readership to establish a world we subsequently visited about once a week.

The End