Thrice upon a Time (5 page)

Although they had been more or less prepared for what to expect, Murdoch and Lee were too stunned for the moment to say anything. Talking about this kind of thing in the car from Edinburgh was one thing; seeing it demonstrated was quite another.

"It works with computer-transmitted numbers too," Charles commented matter-of-factly after a few seconds. Murdoch continued to stare with disbelieving eyes at the sheet of paper in his hand.

Lee looked slowly up at Charles, his brows knotted in bemusement. His lips moved soundlessly for a second or two. Then he whispered, "That… that was printed before Doc even knew what you were going to ask him to do. This really isn't some kind of conjuring trick? Are you saying those characters were sent backward through time?"

"Aye. Sixty seconds, to be exact." Charles looked back at him impassively.

"They exist!" Murdoch breathed, finding his voice at last. "The tau waves that you've always predicted—they really do exist!"

"So it would appear," Charles agreed.

As Murdoch slumped back in the chair and began turning over in his mind what it all meant, Lee gazed with new respect at the array of equipment surrounding him. It didn't look particularly spectacular; in fact, as far as external appearances were concerned, it could have been any one of a hundred lab lash-ups that he had seen before in all kinds of places. And yet what he had just observed had shaken him more that anything he could remember in his twenty-eight years. Murdoch had told him enough about Charles's work for him to have a general idea of how the machine worked, but inwardly he had never believed that anything would come of it.

The influence that propagated through time originated with the annihilation of matter, that is, the conversion of mass into energy. The mass-energy equivalence relationship became nonlinear at high energy densities; under extreme conditions, less energy appeared for a given amount of mass than traditional theory said ought to. The hadron decay into quarks that Charles had mentioned had been the first instance to be noticed; at the high energy density prevailing inside the infinitesimally small volume of the interaction, less gluon binding energy had been measured than had been predicted. Where did the rest go? According to the theory developed by Charles and his colleagues, it had propagated away as tau waves and rematerialized as mass-energy at another instant in time. Because of the small scale of the events, the resulting time shifts had been of the minute order that Charles had described. But at higher energy densities they promised to be more.

Charles's machine achieved high energy densities by focusing an intense beam of positrons onto a magnetically confined concentration of electrons. It employed a laserlike pumping technique perfected in the USSR about fifteen years before to generate energetic gamma photons, which in turn bred electron-positron pairs. The positrons were channeled by tuned fields and directed at a confined, negative space-charge to produce the sustained annihilations that the process demanded. Unlike the giant particle accelerators, which were designed to produce a few isolated events but at enormous energies, this machine produced many events at moderate energies within a tiny volume of space; it was the energy
density
that mattered. That was why the machine didn't need to be as large as the whole Storbannon estate; it also explained why the discrepancies attributable to the tau waves had remained undetected through the earlier decades of particle physics.

The result of the annihilation process was a burst of conventional energy, which was absorbed by a cooling arrangement, and a pulse of tau radiation that would reappear in detectable form elsewhere along the time line. The energy of the gamma photons could be varied, enabling the point in the future or in the past at which the tau pulse would materialize to be adjusted with a high degree of precision. The machine therefore functioned more like a telephone than a radio; the sender could "aim" a pulse at a selected instant, in the past for example, but a receiver in the past, or future, had no means of "tuning in." A receiver could do nothing but wait for incoming calls.

Lee was unable to identify which of the cubicles and racks contained which components, but he would have ample time in the days ahead to become familiar with such details. For the time being he just wanted to know more about the basic principles.

"How is the character information modulated onto the positron beam?" he asked Charles. "Do you interrupt it somehow to get a serial code?"

"That would introduce too many complications, as you'll appreciate later on," Charles replied, shaking his head. "It sends one data-frame in parallel code. The beam is split forty-eight ways to give forty-eight simultaneous tau pulses. Thirty-six of them are used to encode six-bit characters, which is why we're restricted to a six-character message at the moment. The other twelve bits are for control and timing signals."

"So the sequence that Doc keyed in was stored first, then transmitted all in one block."

"That is correct," Charles said.

Lee nodded slowly and rubbed his chin while he looked at the equipment again. The shock was wearing off, and he was beginning to think more coherently. "So what's its… its range?" he asked. "How far back can it send?"

"That's determined by three factors," Charles answered. "The magnitude of the pulse sent, the sensitivity of the receiving detector, and the absolute velocity of the Earth through space. You see, the tau pulse reappears as detectable energy at the same point in space as it was generated. Theoretically the profile of the reappearing energy wave forms a spherical surface that expands at light-speed about that point with increasing distances back along the timeline. After one second back in time it would occupy a volume one hundred and eighty-six thousand miles in radius, after two seconds one of twice that radius, and so on."

"It can't be," Lee protested. "The machine's not big enough to pack that much power. How could one pulse from it fill a volume that big?"

"Ah, I only said that was theoretically," Charles reminded him. "That's the mathematical limit. Inside that volume, the intensity falls off exponentially from the center-point. The signal exists everywhere inside that expanding volume. However, to receive it, the receiver can only be up to a certain distance from the center of the wave pattern, depending on how sensitive it is."

"So that's where the velocity of the Earth comes into it," Lee said. "The Earth will have moved between the time of sending and the time of receiving. You can only send as far back as corresponds to moving the receiver to its limit of sensitivity."

"Exactly," Charles confirmed. "According to the data from Doppler shifting of big-bang background radiation, the Earth moves about twenty-one million miles in a day. The detectors in the machine will operate reliably up to approximately one hundred and forty-five thousand miles from the center-point of the wave pattern produced by the level of tau pulse that this machine sends. If you work that out, it gives you a range of just about ten minutes."

Lee shook his head in wonder and stared at the characters still preserved on the screen in front of Murdoch. "So how long have you had it working now?" he asked.

"Only since two days ago," Charles told him. "I got it to work for the first time the day before I called Murdoch. Even Ted Cartland hasn't seen it yet. I called him a few minutes before I called you, Murdoch, but he's stuck in Manchester and won't be able to get away until tomorrow morning." Charles cackled wheezily. "The poor fellow was becoming frantic when I talked to him again, earlier today."

Murdoch was only half listening. He was still staring at the console, mentally replaying each step of the demonstration that Charles had given. The question going through his mind was obvious. Finally he looked up at Charles. "When you set this machine up a few minutes ago, you got the hardcopy first. Then you started up a program that would time-out after sixty seconds and send back whatever I typed in. Is that right?"

"Yes," Charles said simply.

Murdoch thought for a moment longer. "Okay. Let's ask the hundred-thousand-dollar question: What would have happened if I'd simply decided not to key in anything at all after the sixty seconds? What would have happened to the characters that were already on this sheet? How could they have gotten there?"

Charles nodded as If he had been waiting for Murdoch or Lee to ask that, and moved forward to reinitiate the system. Then he stepped back. "Try it and see," he invited.

Murdoch looked at the hardcopy slot expectantly and waited. Behind him, Lee moved closer and watched intently.

Nothing happened.

Murdoch's face knitted into a puzzled frown. After a while he looked up at Charles, but there was no surprise in Charles's expression. They waited.

"I don't believe this," Lee murmured at last. "It's no different than last time. Surely an intention inside somebody's head can't make any difference to what the machine does. That's for ESP freaks."

"Wait," Charles told them.

They waited.

Suddenly the slot ejected a sheet of paper. Lee leaped forward and snatched it up.

"It says MURDOC," he announced.

"When was it sent?" Murdoch demanded.

Lee checked the time printed on the sheet and glanced at the time-of-day readout on the console. "It's still set up for sixty seconds," he said. The countdown display had appeared at the top of the screen to confirm his words.

"Right," Murdoch declared. "We'll just see." He sat back in the chair and folded his arms in determination. Clearly he had no intention of doing anything when the zero arrived. Charles watched, but said nothing. The final seconds ticked by; Murdoch and Lee became visibly tense. Then the zero appeared.

And that was that. The paper with its printed record remained in Lee's hand, and time marched on past the deadline regardless. Two faces jerked round toward Charles, demanding an explanation.

"I don't know," Charles said quietly. "I don't know who sent that, or where from, either." The other two gaped at him incredulously. They were too confused for a moment to say anything. Charles stepped forward again and used the touchboard to bring up a color display on the screen. It showed a horizontal line across the bottom, annotated with numbers like the X-axis of a graph with zero at the center; above the line, the main area of the screen was divided vertically into three broad bands: a central white one separating two of gray.

"This is a graphical representation of the machine's window of range," Charles explained. "The horizontal axis is time, with the present instant corresponding to the zero in the middle. The white zone is twenty minutes wide; that's the window of the machine's current range, extending ten minutes forward and back. The gray areas on either side are the edges of the future and the past lying outside the ten-minute range."

To the left of center inside the white area, they could see a short red bar standing up from the scale at the point denoted by -6 —six minutes into the past, and a similar, but dotted, red bar at -5 minutes. There was a second pair of bars, this time blue; the solid one was at -11/2 minutes, the dotted one at -1/2 minute.

"Those two solid lines represent signals that the machine has received and logged," Charles explained. "The red one at minus six minutes is the random sequence of characters that Murdoch sent back a little while ago. Some of the control bits sent with every signal denote the time of transmission, so the computer can plot on the display when the signal was sent, which it does by adding a dotted line of matching color in the appropriate place. You can see that the dotted red line is a minute ahead of the solid one in time. If you watch closely, you should just be able to make out that the whole pattern is creeping slowly to the left as time advances. Thus the zero in the center always corresponds to the current instant." Charles paused and took a long breath, as if he were being forced to say something that he didn't really believe. He raised his arm and pointed at the second, blue pair of bars. "The solid blue line, now at minus two minutes, represents the reception of the signal that Lee read out two minutes ago. And the corresponding dotted line"—he pointed with his finger—"is the machine's reconstruction of where it was sent from—a point in time that is now one minute behind where we are right now." He stopped speaking and waited for the protests that he knew would come.

"That's crazy!" Murdoch exclaimed. "I didn't send anything one minute ago. You were both watching me. Nobody sent anything one minute ago. There has to be something screwy with the system. How could— What the… ?" He sat forward abruptly and stared wide-eyed at the screen. A solid green bar had appeared right on the zero-point of the scale, indicating that another signal had been received at that very instant. At the same time a dotted green bar had appeared sixty seconds ahead of it—sixty seconds in the future. The hardcopy slot disgorged another sheet.

"It says 'CRAZY,' " Lee told them in a bewildered voice. "What in hell's going on?"

A solid yellow bar appeared at zero to the right of the green one, which had already moved a few seconds leftward into the past. Its dotted yellow companion was well over to the right of the white area, denoting that something had come in from about eight minutes in the future. Charles touched a pad to deactivate the hardcopy unit.

"We can look at what the signals actually say later," he said. "I don't think it matters all that much for now." It was almost as if he knew what was going to happen next. The display suddenly went wild. Bars of every shade and color added themselves at the zero-point as fast as the ones already there could shuffle out of the way, producing a solid, rectangular, rainbow spectrum that steadily extended itself relentlessly toward the left. At the same time the right-hand half of the white area, representing the future ten minutes of the machine's range, filled haphazardly with matching dotted bars to complete each pair.

Murdoch slumped back in the chair, shaking his head as his mind abandoned the struggle of trying to find reason in what his eyes told him was happening. The solid bars merged into a block of color that grew until it covered the full ten minutes of the past. By that time the isolated red and blue bars with which the whole thing had begun had been pushed out of the white area completely, and were now standing alone in the left-hand gray zone, beyond the ten minutes of the machine's range; almost twenty minutes had elapsed since Charles's initial demonstration.