by Timothy Zahn
For a long moment the only sound in the room was the hum of the terminal in the corner... and the hazy buzzing of Garwood's words spinning over and over in Davidson's brain. "You what?" he whispered at last.
Garwood's shoulders heaved fractionally. "Sounds impossible, doesn't it? But it's true. And it's because of that..." he broke off, reached over to flick one of the loose cigarettes a few inches further away from him.
"Dr. Garwood—" Davidson licked dry lips, tried again. "Doctor, that doesn't make any sense. Why should a... a time machine—?" He faltered, his tongue balking at even suggesting such a ridiculous thing.
"Make things disintegrate?" Garwood sighed. "Saunders didn't believe it, either, not even after I explained what my paper really said."
The shock was slowly fading from Davidson's brain. "So what did it say?" he demanded.
"That the uncertainty factor in quantum mechanics didn't necessarily arise from the observer/universe interaction," Garwood said. "At least not in the usual sense. What I found was a set of self-consistent equations that showed the same effect would arise from the universe allowing for the possibility of time travel."
"And these equations of yours are the ones you recited to me when you wrecked my car and gun?"
Garwood shook his head. "No, those came later. Those were the equations that actually show how time travel is possible." His fingers moved restlessly, worrying at another of the cigarettes. "You know, Major, it would be almost funny if it weren't so deadly serious. Even after Backdrop started to fall apart around us Saunders refused to admit the possibility that it was our research that was causing it. That trying to build a time travel from my equations was by its very nature a self-defeating exercise."
"A long time ago," Davidson said slowly, "on that car ride from Springfield, you called it subconscious democracy. That cigarettes disintegrated in your hand because some people didn't like smoking."
Garwood nodded. "It happens to cigarettes, plastics—"
"How? How can peoples' opinions affect the universe that way?"
Garwood sighed. "Look. Quantum mechanics says that everything around us is made up of atoms, each of which is a sort of cloudy particle with a very high mathematical probability of staying where it's supposed to. In particular, it's the atom's electron cloud that shows the most mathematical fuzziness; and it's the electron clouds that interact with each other to form molecules."
Davidson nodded; that much he remembered from college physics.
"Okay. Now, you told me once that you hated being hooked by cigarettes, right? Suppose you had the chance—right now—to wipe out the tobacco industry and force yourself out of that addiction? Would you do it?"
"With North Carolina's economy on the line?" Davidson retorted. "Of course not."
Garwood lips compressed. "You're more ethical than most," he acknowledged. "A lot of the 'not-me' generation wouldn't even bother to consider that particular consequence. Of course, it's a moot question anyway—we both know the industry is too well established for anyone to get rid of it now.
"But what if you could wipe it out in, say, 1750?"
Davidson opened his mouth... closed it again. Slowly, it was starting to become clear... "All right," he said at last. "Let's say I'd like to do that. What then?"
Garwood picked up one of the cigarettes. "Remember what I said about atoms—the atoms in this cigarette are only probably there. Think of it as a given atom being in its proper place ninety-nine point nine nine nine nine percent of the time and somewhere else the rest of it. Of course, it's never gone long enough to really affect the atomic bonds, which is why the whole cigarette normally holds together.
"But now I know how to make a time machine; and you want to eliminate the tobacco industry in 1750. If I build my machine, and if you get hold of it, and if you succeed in stamping out smoking, then this cigarette would never have been made and all of its atoms would be somewhere else."
Davidson's mouth seemed abnormally dry. "That's a lot of ifs," he managed.
"True, and that's probably why the cigarette doesn't simply disappear. But if enough of the electron clouds are affected—if they start being gone long enough to strain their bonds with the other atoms—then eventually the cigarette will fall apart." He held out his palm toward Davidson.
Davidson looked at the cigarette, kept his hands where they were. "I've seen the demo before, thanks."
Garwood nodded soberly. "It's scary, isn't it?"
"Yeah," Davidson admitted. "And all because I don't like smoking?"
"Oh, it's not just you," Garwood sighed. He turned his hand over, dropping the cigarette onto the table, where it burst into a little puddle of powder. "You could be president of Philip Morris and the same thing would happen. Remember that if a time machine is built from my equations, literally everyone from now until the end of time has access to the 1750 tobacco crop. And to the start of the computer age; and the inception of the credit card; and the invention of plastic." He rubbed his forehead wearily. "This list goes on and on. Maybe forever."
Davidson nodded, his stomach feeling strangely hollow. A walking time bomb, he'd called Garwood. A time bomb. No wonder everyone at Backdrop had been so quick to latch onto that particular epithet. "What about my car?" he asked. "Surely no one seriously wants to go back to the horse and buggy."
"Probably not," Garwood shook his head. "But the internal combustion engine is both more complicated and less efficient than several alternatives that were stamped out early in the century. If you could go back and nurture the steam engine, for instance—"
"Which is why the engine seemed to be trying to flow into a new shape, instead of just falling apart?" Davidson frowned. "It was starting to change into a steam engine?"
Garwood shrugged. "Possibly. I really don't know for sure why engines behave the way they do."
Almost unwillingly, Davidson reached out to touch what was left of the cigarette. "Why you?" he asked. "If your time machine is built, then everything in the world ought to be equally fair game. So why don't things disintegrate in my hands, too?"
"Again, I don't know for sure. I suspect the probability shifts cluster around me because I'm the only one who knows how to make the machine." Garwood seemed to brace himself. "But you're right. If the machine is actually made, then it's all out of my hands... and I can't see any reason why the effect wouldn't then mushroom into something worldwide."
A brief mental image flashed through Davidson's mind: a black vision of the whole of advanced technology falling to pieces, rapidly followed by society itself. If a superpower war of suspicion didn't end things even quicker... "My God," he murmured. "You can't let that happen, Doctor."
Garwood locked eyes with him. "I agree. At the moment, though, you have more power over that than I do."
For a long minute Davidson returned the other's gaze, torn by indecision. He could do it—he could simply let Garwood walk. It would mean his career, possibly, but the stakes here made such considerations trivial. Another possibility occurred briefly to him... "Why did you need the computer?" he asked Garwood. "What were you trying to do?"
"Find a solution to my equations that would allow for a safer form of time travel," Garwood said. "Something that would allow us to observe events, perhaps, without interacting with them."
"Did you have any luck?"
"No. But I'm not ready to give up the search, either. If you let me go, I'll keep at it."
Davidson clenched his jaw tightly enough to hurt. "I know that, Doctor," he said quietly. "But you'll have to continue your search at Backdrop."
Garwood sighed. "I should have known you wouldn't buck your orders," he said bitterly.
"And leave you out here, threatening a community of innocent bystanders?" Davidson retorted, feeling oddly stung by the accusation. "I have a working conscience, Doctor, but I also have a working brain. Backdrop is still the safest place for you to be, and you're going back there. End of argument." Abruptly, he got to his feet. "Come on. I'll have some of my people p
ack up your stuff and bring it to Backdrop behind us."
Reluctantly, Garwood also stood up. "Can I at least ask a favor?"
"Shoot."
"Can we drive instead of flying? I'm still afraid of what influence I might have on a plane's engines."
"If you can sit this close to that terminal without killing it, the engines should be perfectly safe," Davidson told him.
"Under the circumstances, 'should' is hardly adequate—"
"You're arguing in circles," Davidson pointed out. "If you get killed in a plane crash, how is anyone going to use your equations to build a time machine?"
Garwood blinked, then frowned. "Well... maybe I wouldn't actually die in the wreck."
"All right, fine," Davidson snapped, suddenly tired of the whole debate. "We'll put an impact bomb under your seat to make sure you'll die if we crash. Okay?"
Garwood's face reddened, and for a second Davidson thought he would explode with anger of his own. But he didn't. "I see," he said stiffly. "Very well, then, let's find a phone booth and see what Saunders says. You will accept suggestions from Saunders, won't you?"
Davidson gritted his teeth. "Never mind. You want to sit in a car for fourteen hours, fine. Let's go; we'll radio Chanute from the car and have them call in the change of schedule to Backdrop. And arrange for a quiet escort."
V
"I hope you realize," Garwood said heavily, "that by bringing me back you're putting everyone in Backdrop at risk."
Saunders raised polite eyebrows. Polite, stupidly unconcerned eyebrows. "Perhaps," he said. "But at least here we understand what's going on and can take the appropriate precautions. Unlike the nation at large, I may add, which you've just spent nearly four months putting at similar risk. Under the circumstances, I'm sure you'd agree that one of our concerns now has to be to keep you as isolated from the rest of the country as possible." He shrugged. "And as long as you have to be here anyway, you might as well keep busy."
"Oh, of course," Garwood snorted. "I might as well help Backdrop to fall apart that much soo—"
He broke off as a muffled cracking sound drifted into the room. "More of the plaster going," Saunders identified it off-handedly. "Nice to hear again after so long."
Garwood felt like hitting the man. "Damn it all, Saunders," he snarled. "Why won't you listen to reason? A working time machine cannot be made. The very fact that Backdrop is falling apart around me—"
"Proves that the machine can be made," Saunders cut him off. "If you'd stop thinking emotionally for a minute and track through the logic you'd realize that." Abruptly, all the vaguely amused patience vanished from his face, and his eyes hardened as they bored into Garwood's with an unexpected intensity. "Don't you understand?" he continued quietly. "When you left, the probability-shift damage to Backdrop dropped off to near zero. Now that you're back, the destruction is on the increase again."
"Which is my point—"
"No; which is my point," Saunders snapped. "The probability-shift effect cannot exist if a working time machine isn't possible."
"And yet that same effect precludes the manufacture of any such machine," Garwood pointed out. "As I've explained to you at least a hundred times."
"Perhaps. But perhaps not. Even given that the concept of time-travel generates circular arguments in the first place, has it occurred to you that a working time machine might actually prove to be a stabilizing factor?"
Garwood frowned. "You mean that if we have the theoretical capability of going back and correcting all these alterations of history then the wild fluctuations will subside of their own accord?"
"Something like that," Saunders nodded. "I did some preliminary mathematics on that question while you were gone and it looks promising. Of course, we won't know for sure until I have all the equations to work with."
"And what if you're wrong?" Garwood countered. "What if a working time machine would simply destabilize things further?"
A flicker of Saunders's old innocent expression crossed the man's face. "Why, then, we won't be able to make one, will we? The components will fall apart faster than we can replace them."
"In which event, we're back to the probability-shift effect being a circular paradox," Garwood sighed. "If it prevents us from building a time machine, there's no time travel. If there's no time travel, there's no change in probabilities and hence no probability-shift effect."
"As I said, time travel tends to generate paradoxes like that." Saunders pursed his lips. "There's one other possibility that's occurred to me, though. The man who brought you back from Champaign—Major Davidson—said in his report that you'd been trying to find an alternative solution to the time travel equations. Any luck?"
Garwood shook his head. "All I found was blind alleys."
"Maybe you just didn't get to look long enough."
Garwood eyed him. "Meaning...?"
"Meaning that one other possible explanation of the probability-shift effect is that there is indeed another set of solutions. A set that will let us build the machine and still be able to go back and change things."
Garwood sighed. "Saunders... don't you see that all you're doing is just making things worse? Isn't it bad enough that things fall apart around me?—do you want to see it happening on a global scale? Stabilization be damned: a time machine—a real, functional time machine—would be the worst instrument of destruction ever created. Ever created."
"All I know," Saunders said softly, "is that anything the universe allows us to do will eventually be done. If we don't build the machine, someone else will. Someone who might not hesitate to use it for the mass destruction you're so worried about."
Garwood shook his head tiredly. The discussion was finally turning, as he'd known it eventually would, onto ail-too familiar territory: the question of whether or not the fruits of Backdrop's labor would be used responsibly by the politicians who would inherit it. "We've gone round and round on this one," he sighed, getting to his feet. "Neither of us is likely to change the other's mind this time, either. So if you don't mind, it's been a long drive and I'd like to get some rest."
"Fine." Saunders stood, too. "Tomorrow is soon enough to get back to work."
In the distance, the sound of more cracking plaster underlined his last word. "And if I refuse?" Garwood asked.
"You won't."
"Suppose I do?" Garwood persisted.
Saunders smiled lopsidedly and waved a hand in an all-encompassing gesture. "You talk too contemptuously about the not-me' generation to adopt their philosophy. You won't turn your back on a problem this serious... especially given that it's a problem partially of your own creation."
For a long moment Garwood considered arguing the latter point. It had been Saunders, after all, who'd pushed Backdrop into existence and then dragged him into it.
But on the other hand, it wasn't Saunders who knew how to build the damn time machine.
Wordlessly, he turned his back on the other and headed for the door. "Rest well," Saunders called after him.
—
His office, when he arrived there the next morning, was almost unrecognizable.
Two pieces of brand-new equipment had been shoehorned into the already cramped space, for starters; a terminal with what turned out to be a direct line to the Minneapolis Cray HI supercomputer lab, and an expensive optical scanner that seemed set up to read typewritten equations directly onto the line. So Saunders is capable of learning, Garwood thought sardonically, careful not to touch either instrument as he gave them a brief examination. The electronic blackboard that had fallen apart shortly before he left Backdrop was gone, replaced by an old-fashioned chalk-on-slate type, and his steel-and-plastic chair had been replaced by a steel-and-wood one. Even his desk looked somehow different, though it took him a long minute to realize why.
All the piles of papers had been changed.
Silently, he mouthed a curse. He hadn't expected the papers to remain untouched—Saunders would certainly have ransacked his desk in hopes of
finding the rest of his time-travel equations—but he hadn't expected everything to get so thoroughly shuffled in the process. Clearly, Saunders had gone about his task with a will and to hell with neatness; just as clearly, it was going to take most of the day to put things back where he could find them again. With a sigh, he sank gingerly into his new chair and started restacking.
It was two hours later, and he was not quite halfway through the task, when there was a knock on the door. "Come in, Saunders," he called.
It wasn't Saunders. "Hello, Dr. Garwood," Major Davidson nodded, throwing a glance around the room. "You busy?"
"Not especially." Garwood looked up at him. "Checking to make sure I'm still here?"
Davidson shrugged fractionally, his gaze steady on Garwood. "Not really. I believe Colonel Bidwell has been able to plug the hole you got out by the last time."
"I'm not surprised." The look in Davidson's eyes was becoming just the least bit unnerving. "May I ask why you're here, then?"
Davidson pursed his lips. "The random destruction has started up again since we got in last night."
"This surprises you?"
Davidson opened his mouth; closed it. Tried again. "I'd... rather hoped you weren't so clearly the pivotal point of the effect."
"I thought we'd discussed all that back in Champaign," Garwood reminded him. "I'm the only one who knows how to build the machine, so of course the probability-shift effect centers around me."
Davidson's eyes flicked to the computer terminal/optical scanner setup. "And Saunders wants you to let him in on the secret."
"Naturally. I don't intend to, of course."
"And if he doesn't give you that choice?"
"Meaning...?"
"Meaning he tried once to use hypnosis to get your equations out of me. With you, the method would probably work."
Garwood's mouth felt dry. "He knows better than to try something that blatant," he said. Even to himself the words didn't sound very convincing.
"I hope so. But if he doesn't... I trust you'll always remember that there's at least one other person in Backdrop who recognizes the danger your knowledge poses."
