Finity

by John Barnes

  She squeezed my testicles, hard, and I nearly vomited as I yelped in pain. Laughing as if it were Christmas, she stretched out beside me.

  Strangely enough—how could I sleep next to someone who so terrified me?—it wasn’t long before I fell sound asleep. When she shook me awake, we had just fifteen minutes to get down to the meeting. I didn’t look at her and I asked her to leave the room while I dressed. She laughed at me again, and I really didn’t like the sound of it this time. It was even more frightening, and even less Helen.

  * * * *

  Iphwin began his talk obliquely; he said, “I have spent a very long time thinking about how I was going to present this to all of you, and I’m not altogether sure, even now, that I have picked the right way to do it. I know you must be curious about who I am, how I came to know the things I am going to explain to you, and how and why I have undertaken the project that I am asking you all to join—but I am going to deliberately not gratify your curiosity for the moment, because my explanation will make a great deal more sense if I first give you some basis for understanding it. I hope that I am making myself completely obscure?”

  “You are,” I said, since no one else spoke.

  “Well, good, then my sense of how the human mind responds is not completely wrong. I hope I can make matters clearer, later, but for right now it is probably appropriate that they be obscure. To begin with, then—your surmises, Lyle, Helen, and some of you others, about the Many Worlds Interpretation and some of the other questions, have been largely correct. People, information, and objects did indeed begin, a few decades ago, to cross over between different worlds, as you call them—or timelines, or histories, or event sequences, depending on whose terms you prefer to use—and this does account for discrepancies in your memories, for the occasional outright violations of causality you have noticed, and even for the new cultural norm of people avoiding any sort of discussion of the past, even of their own personal past.

  “Has any of you figured out when these things happen, or what triggers them?”

  There was a long silence, and Iphwin said, “You couldn’t be expected to, of course—for one thing, the experience itself is sometimes mildly disorienting, particularly if you’re crossing between event sequences which are extremely different, as has happened to several of you in the course of your lives. Well, I can now fill you in—or I suppose if I can’t, I’m about to find out.

  “People cross over when they talk on the phone, when they get on-line, and when they ride in a robot-piloted vehicle.”

  I felt like I had just gotten an electric shock right up my spine; suddenly everything was clear. “That’s why!” I said. “They’re all driven by quantum computing devices!”

  Everyone turned and stared and I remembered that I was the only person with any physics background in the room. “Er—” I said.

  “You’re exactly right, Lyle,” Iphwin said, “that’s what’s going on. And the odd part is, that isn’t really a problem. It’s merely the reason why the real problem has gone undetected till now. But I’m getting ahead of myself—perhaps I should just launch in, and if we can get the occasional assist from Professors Peripart and Perdita, we can put the whole story together quickly.”

  Iphwin’s lecture and the questions after it ran till midnight; he provided us with plates of sandwiches, pastries, fruit, coffee, tea, and juice, and gave us a bathroom break punctually on every hour, so we endured it well enough physically, but some of us had hoarse voices from arguing by the end, and almost all of us had brains that hurt. But he kept producing evidence, and what he told us fit the facts. Eventually we bought it, perhaps because it was such a relief to feel like we understood what was going on.

  There were indeed many worlds—in fact there was every possible world. Perpendicular to time, and to our familiar spatial dimensions, there were five spacelike dimensions Iphwin called “possibility,” and each event sequence had a unique five-dimensional address within those dimensions. “Suppose there was just one thing in the universe, and all it could do was to be somewhere—and there was just one spatial dimension,” Iphwin said, trying to get it across to our less mathematical members. “The one spatial dimension would be a line, right? Imagine it as a road, if you want. The one object is a car, and every time it passes through any given place, it’s an event. Now, you could make a picture of the universe as a graph, with the horizontal being the position on the road, and the vertical being the time. On that graph a vertical line would mean the car just stayed in one place, and the more horizontal the line got, the faster the car would be moving. A big curve like the letter S would be somebody driving back and forth. Every point on that line would be an event. Does that make sense so far?”

  “It’s been a long time since I had to take algebra,” the Colonel grumbled.

  “I can promise you that they haven’t improved it any, either,” Terri said. “All right, so then if you have one dimension of possibility, it’s like stacking all the possible graphs there can be, one on top of the other, with the most similar ones closest. Right?”

  Iphwin seemed startled. “You have talent.”

  “I spend all my time in school. I’m used to lectures. And besides, you said a world or a timeline could be called an ‘event sequence,’ right? Well, then obviously a line of events, like what you’re describing on the graph, is an event sequence. And time only runs one way, and you said there’s just one car on the road, so if there was just one world it would have just one line. If there are many worlds, then you have one graph for every possible way a car could go back and forth on the road. That’s all.”

  “And it’s right,” Iphwin said. “Those of you who are confused should consult with Terri from now on.”

  “And those of you who want to be confused can consult with me,” Paula Rey said. “So the whole point of the graphs and the road and so forth is that it’s a very simplified version? In the imaginary world there’s one object, one dimension of space, one dimension of time, and one dimension of possibility, right? And in our real world you’re saying we have some huge number of objects, three dimensions of space, one of time, and five of possibility?”

  “That’s it exactly. You’re not as confused as you think you are. It’s just that what I’m telling you is pretty big. Now, one of the implications of this is that in the dimensions of possibility there can be an infinite number of worlds next door. A point can have an infinite number of neighboring points, and that’s in two dimensions; a line can have an infinite number of neighboring lines, in three; and so forth. By extension, an event, which is a four-dimensional thing, can have an infinite number of immediate neighbors in the five dimensions of possibility. And those are just the ones at zero distance.

  “Now it turns out that if you cross over into another event sequence, you’re more likely to cross over to a nearby one than to a far one. In fact, every second that you’re on the phone, you’re bouncing from one world to another constantly. It’s just that most of the time, you bounce between worlds that are so similar that you can’t tell the difference. For example, maybe in one world you have a few more atoms of calcium in one of your teeth—or maybe the buttons on your clothes are six microns larger. Or maybe you bounce to a world where all the way across town, a man is washing his car instead of reading the paper.

  “But every so often you take a bigger bounce, and you’re in a world where your history is noticeably different. That’s what happened, for example, to Helen Perdita when she was a teenager, or to Paula and Jesús more recently.”

  “Why should it happen when we’re on the phone?” Roger said. “Why not while we’re bathing or flossing our teeth or asleep? And didn’t you say it also happens while we’re on-line or while we’re in a robot-driven vehicle?”

  “All of the above and a few others,” Iphwin agreed. “Perhaps Lyle has gotten it all figured out now, since he’s had time? He’s more experienced at lecturing than I am, and since the idea is new to him, maybe he can explain it more cle
arly than I can—the idea is at the core of my being, you might say, so I’m apt to assume too much when I explain it.”

  I harrumphed and collected my thoughts. I began by telling them about Schrödinger’s cat, and the whole problem of how to interpret a distribution of quantum states when you project it upward into the macro world. Then I found myself explaining something that tends to make people nervous, and therefore is rarely publicized by the big communications companies.

  “Maybe seventy or eighty years ago,” I explained, “people doing brain research got interested in the problem of how the brain could possibly be storing as much sheer raw information as it seemed to. Once they started to get some idea of how things were coded into individual brain cells—basically as linked sets of physical impressions—it just didn’t seem like there could be enough room in the human head for all of that. Since we didn’t have room for the brains to do it with, how were we remembering so much?

  “Well, the answer turned out to be, we weren’t. You remember someone’s face as, maybe, an impression of one eyebrow, half the lower lip, part of the nose, and an eye. When you recall their face later, what your brain does—faster than anyone could sense in real time—is to reconstruct the picture, filling in all the details. It’s easy for the brain to do because faces are symmetrical, some kinds of features tend to go with each other, and so forth. The mind has a fast little interpreter that fills in the rest of the picture.”

  “That’s why most pro actors can get up on a part fast, in terms of knowing roughly what they do when,” Kelly said, “but getting from knowing your part to knowing exact words is a pain in the ass that takes forever. You can learn a few markers almost instantly, but to get the whole thing perfect you’ve got to have many more markers, and then get the feel of the text, so that what you construct between the markers is always right.”

  “Exactly. Well, that was kind of interesting, as a piece of brain research, and it helped to explain little things like the way you’ll sometimes mistake a stranger for an old friend you haven’t seen in a while, or the way people will begin to remember something different from what happened if you repeat a story to them often enough—they start to fill in bridging material that includes some of what you tell them. But the most important application came later, in communications. It was a solution to the bandwidth problem.”

  Among questions and interruptions, I sketched out the basic concepts for them. Imagine an old-fashioned Morse code transmitter, sending dots and dashes; it has a bandwidth of one. That is, either the wire has current flowing through it, or it doesn’t. Now, since no Morse signal has more than four dots or dashes, theoretically if you had four wires, you could send each character all at once, instead of sequentially, and send four times as fast. That’s a bandwidth of four. The amount of information that can pass a given point in a given time is speed times bandwidth—and since by the turn of the twenty-first century, bandwidths were running into millions and speeds to megahertz, trillions of bits per second were traveling through each junction in the system.

  It still wasn’t fast enough for some purposes, and most especially not for one commercially very important one. The human senses as a whole have a bandwidth that runs into many trillions, and you need to be able to simulate all the senses all at once in real time to produce effective virtual reality. And you want to produce that really effective virtual reality because human beings seem to have a nearly unlimited demand for being made happy and taken care of all the time—we’re all big babies on some level, I suppose—and anyone who can deliver that cheaply enough can probably collect the whole wealth of the human race eventually; even now there are people, especially people born rich in some of the advanced nations in some of the world lines, who spend more years hooked up than not. So one way or another, they were going to get that bandwidth, or figure out a way to put a great deal more through the bandwidth they had.

  As it turns out, you can simulate reality fast enough to do vivid VR, but getting signal into and out of the brain requires enormous bandwidth, and thus though a VR simulator could deliver enough signal to produce a vivid reality for one person or a few people, a single long-distance VR call would theoretically have required more bandwidth than the whole United States had used for radio, phone, and telegraph to get through the Second World War. Though there was an enormous market for VR worlds that could be shared as real, living, breathing experiences, to provide for that market would seem to require the construction of enormous facilities to provide enough bandwidth for all that signals traffic.

  There was another enormous demand for bandwidth lurking in the wings too. Self-piloting vehicles would work best if every car on the road could share information with every other car. You wanted a car that could think and look fast enough to figure out that a ball rolling into the street was apt to be pursued by a child, or to dodge around—and alert every other car to—a board with nails lying on the pavement. Once again, bandwidth needed was just much, much bigger than the bandwidth that could even conceivably be made available.

  Computer speed depends in part upon internal bandwidth— because the size of the chunks of data moving around inside the computer determines how fast the computer can rearrange information, and therefore “think.” Since VR communication had to move through the computer anyway, putting it through a faster system was highly desirable, and the fastest systems of all, by the mid-twenty-first century, were quantum computers—systems that took advantage of the peculiarity of quantum physics that a single object could behave as if it were in a distribution of several mutually exclusive states all at once. In effect, you could solve the problem of the dead cat and the problem of the live cat simultaneously, and each bit in the computer’s memory and each operation in its registers could be in parallel with itself; a single machine could be made to act like many thousands all at once, with a tremendous gain in speed.

  But massively parallel processing had another use—it was exactly how computer engineers had been able to simulate many human brain functions. The ability to construct a face for recognition, or fill in the lacunae in a partial text, or smooth out a partially degraded hologram from fragments required the massive and fast parallelism that only the quantum computer could provide. The quantum computer, then, made real-time VR communication possible, for it made it possible to transmit a small fraction of the needed information for the simulation, and from that information to construct a full simulation at the other end.

  But the uncertainty principle limited the user’s control of the information; you couldn’t know which state any of the quantum processors was “really” in without preventing the parallel processing you needed. If you bought into the Copenhagen Interpretation, this was no problem; you simply treated it as a computational trick that allowed you to get away with sending less information than the other side received. Likewise, in the Aphysical Interpretation, the problem was no problem—it was as if you had two ponds, with a stick in each one, and the two sticks connected by a string: a wave in one would make a wave in the other, and multiple and complex wave patterns went through because the stick could move in multiple and complex ways.

  But in the Many Worlds Interpretation, what you were doing was solving the problem by using all of the neighboring worlds plus your own—and the uncertainty principle would not let you know which answer was going to which address. Those who thought about it at all, in those terms—my friends and I, in grad school, had often argued about it over beer—had always assumed that the solution must be that in a quantum computer network, there must be a great many “cosmic wrong numbers”—i.e. messages that went to the wrong universe. That always led us to argue that we had found a reason the Many Worlds Interpretation could not be the right one—because the uncertainty principle, applied to the addressing problem, seemed to say that you couldn’t know whether or not a number was wrong, and thus all those “wrong numbers” would violate it.

  We had never considered that Nature might solve the problem by not allowi
ng anyone on the receiving end of a message to know what universe he was in. And yet that solution now seemed exactly the sort of thing you might expect of Nature in her better moods. Whoever was receiving the message would exist in a suspended state, like Schrödinger’s cat, for as long as they were on the line; unlike the cat, they would not be half alive and half dead, but fractionally in many different worlds. Hanging up or briefly disconnecting—and the line-sharing protocols in any modern network guaranteed brief disconnects many times per second— was exactly the equivalent of opening the box and collapsing the probability distribution onto a singular state—living or dead for the cat, some universe or other for you.

  Once the wide-band quantum network had come into use for VR, everything else had been piggybacked onto it, because it had so much room for everything else—transportation signals, fax, television, telephone, and all the rest. Whenever you went on-line in the quantum communication system, you oscillated through many of the possible system states, many times per second. This was true whether you were a person, a bale of hay, or an e-mail message.

  “So,” I concluded, at the end of it all, four sandwiches, six cups of coffee, and too many arguments and diagrams to count later, “basically we’ve been reshuffling all the worlds at a faster and faster rate, and as each big family of event sequences gets VR and quantum computing, the number that we can interchange with has increased polyfold. By now nobody is in the world they began in. Mostly the worlds are enough alike so that people adapt, though I’m sure there are more street crazies and mental patients than there used to be in most worlds, and many of them probably spend all of their time trying to tell anyone who will listen that something is terribly wrong.”