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 clearly 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.