Thrice upon a Time (29 page)

"Murdoch, what's the matter?" Anne's voice came suddenly from the doorway. She sounded worried. Murdoch looked up slowly and turned his head toward her, but his eyes seemed to be staring straight through.

"Sit down, Anne," he said in a dull, heavy voice. "I guess it's time I told you about what else has been happening at Burghead."

"There isn't any way they can be stopped," Murdoch said wearily. "At least, assuming these calculations are correct. We didn't spend time double-checking everything, and we had to make a few assumptions that might be suspect, but right now that's the way it looks."

"You can't be absolutely certain, then," Anne said. She had recovered somewhat from the impact of Murdoch's revelation, although her face was still pale and her voice shaky.

"No," Murdoch admitted. "Not absolutely." His tone said that he was convinced in his own mind nevertheless. A silence descended. Murdoch returned his attention to the curves and numbers that he had been manipulating on the main screen of the machine's console throughout the hour or so that he and Anne had been talking. At intervals he had lapsed into long periods of staring silently and thoughtfully at the displays, but so far he had not told Anne anything of the idea that was beginning to form in his mind.

Anne sat back in her chair with a long, despairing sigh, and tried again to grasp the enormity of what Murdoch had told her. The whole history of the human species was nothing but the tail-end of the saga of the birth and shaping of the Earth itself. Even the story of life was but the final page to be added to the book that had been written so far. It was as if the whole, intricate, billions-of-years-long process had been simply preparation for the story that would begin when mankind at last appeared upon the stage. And now, with the first few lines of the opening act barely completed, the story would never be told. All that would be left to mark that it had ever begun would be a knot of deformed spacetime orbiting the sun.

She looked at Murdoch, still working silently and intently at the console, not knowing what to make of the strange change that she had sensed coming over him in the course of the last hour. An hour ago he had been resigned to the hopelessness of everything; now his mood seemed determined and purposeful. Anne sensed that it was not a time to press him with questions. She waited.

At last Murdoch sat back in the chair and stared for a long time at the data being displayed on the main screen. Then, without turning his head to look at her, he asked, "Anne, can you program one of these computers?"

Anne's forehead creased in bewilderment. "I've worked with DEC 22/40s and 435," she replied. "Software-wise they're the same as a 30. Why?" Murdoch did not answer directly. Instead he swiveled his chair around to face where she was sitting. There was a strange, distant look in his eyes, one that Anne had never seen before.

"There's no way that a black hole can be destroyed once it's grown large enough to be stable," he said. "From that point on, nothing you do can get rid of it."

Anne shrugged. "I know. So there's nothing anybody can do to change things now."

"There is," Murdoch said. "The phrase I used was:
' ... from that point on ... ' "
For a few seconds Anne was completely mystified. Then her expression changed slowly to one of disbelief. She gasped, and moved her eyes involuntarily from Murdoch to the machine beside him.

Murdoch nodded. "Exactly!" he told her. "There is something we can do. We can change what happened
before those damn holes were ever created in the first place!"
 

Anne shook her head as she tried to understand what Murdoch was saying. After everything he had said in the last hour, this was too much.

"It's the o
nly
way," Murdoch said. "Nothing else could make any difference now."

"The machine?" she whispered. "You think we could use the machine to change what's happened?"

"Why not?"

"But… but to do that, you'd have to have the reactor tests stopped right at the beginning."

"Yes."

Anne rested her face in her hands while she reached through her mind for something she might have missed. At last she looked up. "But how?" she asked. "The machine only has a range of one day."

"I know."

"The tests were run in January. How can we possibly do anything that will change that?" Anne protested.

"By using the machine as a
relay,"
Murdoch said.

Anne sank back and waved her hand in front of her face. "I don't know what you're talking about, Murdoch. What are you talking about?"

"The machine that's here today can send a message back to itself yesterday," Murdoch said. "That one could relay the same message back to the machine that existed the day before that. It could chain back like that for as far as we wanted it to go." Anne's mind began spinning. She stared from Murdoch to the machine and back again, but could find nothing wrong with what he had said. In fact it now seemed obvious.

Murdoch started speaking again, this time more rapidly and with a note of urgency in his voice. "To get in all the information needed about the black holes, we'd have to send a succession of screens full of data that would all arrive in sequence and remain imprinted on the restructured timeline. That means they'd have to be sent simultaneously in supertime from a series of points along the timeline we're on now. Fortunately we know from the shortening-loop tests how to set up a transmission-control program that will accomplish that.

"Another snag is that the machines that exist on the present timeline yesterday and the days before all the way back to January don't have a program in them that will read in an incoming message and retransmit it back down the line. So what we need to do is set up a bootstrap: a set of machine instructions that can be sent on ahead as the first signal to read in the main program. Then the whole package will copy itself all the way through in one-day jumps to January. All we can do after that is hope to God that somebody back there takes notice of it."

Anne's expression had been changing while Murdoch was talking. His scheme was feasible, she realized. In terms of technique, it was identical to the method of down-line-loading used for sending a program out to another part of a computer network and starting it running in a remote machine; the only difference was that, in the case that Murdoch had described, the program would be bootstrapped through a time-link rather than over a conventional optical cable or a laser beam.

"I think you've got something, Murdoch," she whispered, nodding slowly at last. "It could just work, couldn't it… " Her voice rose to a normal level. "It might work. We'll have to put it to Charles and Ted when they get back. I'm sure that—" She broke off as she saw the look on Murdoch's face. Her face became puzzled. "Why not? Surely we've got to tell them about it."

Murdoch half turned and gestured toward the screen on the console. "We can't wait for them to get back," he said. "We don't have any time."

Anne was nonplussed. "What do you mean? I thought you said there was no immediate hazard."

"There isn't," Murdoch said. "But it's got nothing to do with that. We've only got something like twelve hours left in which we can use the machine. If we don't do it in that time, we'll never be able to do it at all." Anne threw out her hands and shook her head in noncomprehension.

"I've been monitoring the noise background here," Murdoch explained. "There are something like two million black holes down there, consuming mass and radiating tau waves all the time. The machine is picking up the radiation from a few days ahead of now as background noise." He took a deep breath. His voice was sounding hoarse. "The holes are getting bigger, and the noise is getting stronger. If my estimates are right, somewhere around twelve hours from now it'll be strong enough to swamp the signal. The machine will be unusable… permanently. After that it will only be able to get worse."

"You're not suggesting that
we
do this right now… without any reference to anybody," Anne said in a shocked voice. "That's unthinkable, surely."

"We don't have any choice," Murdoch pointed out. "We
have
to do it now, or do it never. If the machine is going to get us all out of this mess, it has to be inside the next twelve hours. We don't have time to convene any committees."

"But, Murdoch, you're talking about changing the whole timeline back to January," Anne protested. "All kinds of people's lives could be affected in ways you can't even imagine. How can we go tinkering with something like that? We've no way of telling what the consequences might be."

"You're right," Murdoch agreed. "But we know what the consequences of the alternative will be."

"We
don't
know… not for certain. You said yourself that the results of the analysis might be wrong."

"They might, but it could take years to verify every detail of the theory rigorously," Murdoch said. "We haven't got years, Anne; we've got twelve hours."

"How sure can you be about that?"

Murdoch shrugged. "It's an estimate. I could be wrong about that too, but that's the way it looks right now. You want to just wait around, do nothing, and find out that way?"

Anne fell silent and thought about the things Murdoch had said. Murdoch watched and read from the changing look in her eyes that she was coming around to accept the irrefutable logic of the situation confronting them. It was as he had said: They had no choice.

"Very well," Anne said eventually in a resigned voice. "What do you want me to do?"

At once Murdoch's manner became more brisk. "I'll need you to write the retransmit program and the bootstrap," he said. "The references you'll need are all over there. I'll use Grandpa's latest calculations and the information that Elizabeth brought on the reactor design to put together a message. I'll keep it short and to the point."

"How long have we got?" Anne asked.

"It's four-fifteen now. The background interference could build up faster than I estimated. I think that to play safe, we ought to aim at being ready to go by noon. What do you think?"

"We should make it okay. That kind of programming is really quite straightforward."

"Just remember that it will have to run right first time," Murdoch said. "If that means you have to take longer, take longer."

Murdoch got up and began rummaging through the notebooks and papers lying on the desk. Anne sat down at the console and activated the machine's program-development system. "I'll have to get some things from the study," Murdoch said, and turned for the door. "I'll be back down in a minute."

"Are we still going out for dinner tonight?" Anne called after him. He stopped for a moment and frowned, unable to decide whether or not she realized what she had said, or if she was being serious. Finally he shook his head, ignored the question, and walked out into the corridor.

By five-thirty Murdoch had explained in detail what he wanted the program to do, and Anne had flow-charted an interpretation that he had agreed should work. She began coding the routine, and he commenced selecting the items of information to go into the message. They worked mainly in silence, each fighting off the fatigue of the hours immediately preceding dawn. Maxwell burrowed into a pile of discarded printout and went to sleep.

At seven-thirty-five Anne ran a test of the program by using a separate area of the computer's memory to simulate the machine that would be functioning as the receiver. She found an error and began tracing it back through the coding that she had generated. Murdoch completed the message and loaded it into the computer ready to be accessed and transmitted by Anne's program. He went to make some coffee while she worked on.

Eight-fifteen. Anne had fixed the error but then had found another one. Murdoch ran an analysis of the background interference and found that it was building up faster than he had estimated. He revised the deadline to ten A.M. instead of noon.

While Anne was tracing the second error, Murdoch checked back through the machine's log to find a good point in the past at which to aim the message. Obviously the recipients should have as much time as possible to grasp the significance of the message and take appropriate action, which meant that the message ought to be sent back as far as possible. The farthest back it could be sent was to the time at which Cartland had increased the message capacity of the machine and extended its range to twenty-four hours; Anne's program would not work correctly with the ten-minute range and the six-character limit that the machine had possessed prior to then.

To get that far back, the message would have to be "hopped" through the two-day period in which the machine had been temporarily disabled by interference coming back from the Burghead tests in January. Luckily the tests had not involved continuous operation of the reactors for the thirty-six hours they had run, but had included several gaps of an hour or two at a time, which were caused by the engineers shutting down the reactors to assess intermediate results and alter the test parameters. The interference pattern obtained at Storbannon had corresponding gaps, during which the machine had been operable. Anne's program would cause the message to materialize in, and be retransmitted from, one of those gaps.