Version Control

by Dexter Palmer

  Desks had been placed throughout the room so that a person sitting at one of them could face the looming central column. There was also a scattered collection of mismatched chairs: a knockoff Aeron whose base was held together with duct tape; an old recliner that had stuffing poking through a rent in its cushion; a folding chair that would have been more appropriate at a poolside. Almost every square inch of the desk surfaces was covered with laptop computers and stacks of papers; more cords led from the laptops, making for more of a mess.

  In a space near the central metal chamber that had been cleared of cords and debris, Alicia Merrill sat on the floor along with a bespectacled graduate student, the two of them huddled over an eight-legged robot whose brightly colored gears could be seen inside its translucent plastic body. Near them was an MP3 player plugged into a pair of speakers; from it came some hip-hop song that Kate figured was a little before Alicia’s time, and definitely before her own. Kate bent over to look at the player’s screen, whose scrolling message proclaimed that she was listening to ALICIA’S NEW JILL SWING MIX!!! PEBBLES! TYLER COLLINS! JODY WATLEY!

  “We take turns picking the music for the lab,” Carson said. “Philip doesn’t want us wearing headphones: too isolating. Today it’s Alicia’s turn to play DJ.”

  “That’s Michel’le,” Alicia said, presumably to Kate, though she still stared intently at the conglomeration of brightly colored gears that made up the guts of the robot spider. “ ‘No More Lies’ was her biggest hit.”

  “She sounds great,” Kate said.

  “That squeaky speaking voice isn’t a gimmick,” Alicia said indifferently. “She really talks like that.” Then she extracted a snapped belt from the robot’s interior and said to the graduate student, “Randall, we’ve made significant advances in the field of physics since the days of Isaac Newton, discoveries about which you appear to be unaware. Later on I’ll recommend some texts for you to look through.”

  “So what’s the robot for?” Kate asked Carson hastily, even though she still remembered the TV segment from Rebecca’s party a few weeks ago: Randall looked uncomfortable, and she figured she could spare him a further tongue-lashing if she changed the subject.

  “That’s Arachne. We send her into the causality violation device. In a perfect world, where everything worked as it should, the area in there would basically join two sections of spacetime that would normally be non-contiguous. To us, with our limited ability to observe objects and events, it just looks like a big tube, but the space inside there is, I guess you could say, connected to a point in spacetime that’s about eight years earlier than now, in the place where this lab used to be, back then.”

  She looked up at the giant cylinder that seemed to be emitting a subsonic hum, something she felt in her chest rather than heard. “That must have been a hell of a thing to pack up and move.”

  Alicia snorted. Kate turned to look at her, but she was busy dismantling Arachne with a screwdriver, and seemed to be suppressing a laugh.

  “Let’s see, how to say this,” Carson said, and Kate felt a slight bit of shame as she heard him try and fail to stifle a sigh. At least he wasn’t completely condescending. “Part of the problem we have here, the PR problem—you saw some of this in that TV program—is that what most people think they know about time travel—”

  “Don’t call it time travel!” Alicia said. “If Philip hears you, he’ll disembowel you and make you clean up the mess.”

  “—they learned from science fiction,” Carson continued. “And most of the time science fiction makes this kind of thing look really easy. You jump in your phone booth that’s larger on the inside than it is on the outside, you pull some levers, and you’re back in the 1840s or wherever. But in real life, connecting two naturally non-contiguous points in spacetime such that a corporeal object can move from one to the other is extremely difficult! And it’s not really moving through time that’s the problem: moving through space is the problem.”

  With Kate following, Carson went over to a desk and cleared a small space off of it, consolidating two stacks of papers into one large pile. “You ever watch hockey?” he said. “Okay. You’re on the ice, and you want to shoot the puck to your teammate. But the other guy is moving, right? So you can’t just shoot the puck to where the guy is: you shoot the puck to where he’s going to be in a couple of seconds. It’s instinctive, but what you’re doing is making a calculation about the other player’s path through spacetime, and then shooting the puck such that its path through spacetime will intersect that of the player. If you shoot at where the player is at the moment you take the shot, you’ll miss, because you forgot to think about the path the player would take through space as time passed. Got it?”

  “I think you just explained to me why I sucked at soccer in middle school,” Kate said. “I was always like: Hey, I’m trying to kick the ball to you! Stand still for a second!”

  “Okay. Now, the calculation you have to make to send an object backward in time is similar to the instinctive one that a hockey player makes before he shoots the puck to his teammate, except that it’s a whole lot more complicated. Also, you have to make the calculation—obviously—in reverse.” From a dingy coffee cup filled with writing implements, Carson removed two ballpoint pens and, holding one in each hand, stood them up on the desk, side by side. “Let’s say you have a time machine. It’s like this little thing that you carry around in your pocket. And it’ll let you go back in time by, I don’t know, two hours. So you want to use it to go back to the same place you’re standing right now, but two hours earlier. It shouldn’t be that hard, right? Two hours is nothing.

  “But look what happened between the time you want to go back to and the time where you are. First,” and Carson moved the pen in his left hand away from the one in his right, “the earth rotated on its axis. And the earth also moved in its orbit around the sun. And that orbit isn’t a clean ellipse, like you see in diagrams in middle-school science books: there are chaotic variables that influence that movement, so even though the earth is never actually going to fly away from the sun or anything like that, there’s a relatively small but still important random element in the path it takes.” Carson dragged the pen across the desk again in another direction, jittering it as he did so. “And in the meantime the Milky Way drifted away from the center of the galaxy.” He moved the pen again. “And the universe continued to expand, as it has since the Big Bang.” He moved it again, this time completely off the desk. “So if you tried to go backward in time without making the proper corrections to account for your relative movement through space, you’d be lucky if you could glimpse earth from deep space in the few seconds before you suffocated.”

  “Jesus,” Kate said.

  “The calculations are extraordinarily difficult. And this contributes to the sharp limits on what we can do. A lot of fanciful scenarios from science-fiction stories are right out. We’ll never be able to send a human being back in time to Hitler’s bunker in 1945, or the Texas Book Depository in 1963, because the data that would tell us how the earth moved through space between then and now is lost to time, and can’t be reconstructed. But what we were able to do—or at least what we believe we may have done, if only we can get this thing to work properly—is construct a wormhole, a discontinuity in spacetime. It has one fixed end and one moving end, like so.” Again, Carson held the two pens up on the desk in his hands, and began to pull one slowly away from the other. “One end of the wormhole is fixed at the point in spacetime we call Point Zero, the point where we first started constructing the causality violation device; the other end of the wormhole is in our present, and travels along with us as we move through space and grow older. And the thing that makes all of this work is a mechanism we installed in the device eight years ago at its conception, called the Planck-Wheeler clock. You can see it there.” Carson pointed up to a featureless black sphere mounted in the side of the column, about halfway up its side. “Philip’s research into gravitational wave detection in
the early years of the century indirectly led to its design—he doesn’t like to talk about that period of his career for some reason, but even if the research into causality violation turns out to be a dead end, his name will be in the history books for his contribution to the Planck-Wheeler clock alone.”

  “So what’s the clock do?” Kate asked. She was trying not to let on that her head was starting to swim a little, especially since Alicia, who was still fiddling around with her robot, seemed to have an attitude problem with those who didn’t get all this stuff. God forbid that someone shouldn’t take to this like a duck to water.

  “The Planck-Wheeler clock measures its own movement through space and time relative to the point in spacetime when it was activated. It accounts for the earth’s orbit, the universe’s expansion, and everything else. And it’s remarkably precise: the unit of time it uses is the period it takes for a light wave to move its own length. Basically, it keeps our computers informed about where both ends of the wormhole are.”

  “So why can you only go back to this point in spacetime you call Point Zero?” Kate said. “It looks to me like if you have this clock that’s been doing all these measurements since you started, then you’ve got all the data: it’s not like if you tried to go back to the Kennedy assassination, like you said earlier. Shouldn’t you be able to go back to any point in time you wanted after you turned the thing on?”

  “That’s a good question,” Carson said, and Kate sensed that his comment was meant as much for Alicia as for her. “The thing is that a wormhole isn’t like an interstate highway, with a bunch of different entrances and exits along a line. It’s more like a roller coaster or a tunnel, though analogies to familiar three-dimensional objects are obviously going to be inadequate in this case. And to be honest, the thing has weird properties: we have theories about what we’ve got here, but we’re not entirely sure.

  “We’re almost completely certain that any object that enters the causality violation device can only exit at either end of the wormhole—the fixed end that’s in the past, and the moving end that’s in our present. We can’t send an object to where the moving end of the wormhole once was at a point in the past, or where it’ll end up in the future. There’s also a restriction placed on us by the law of conservation of mass and energy. If an object enters the wormhole at our end, it has to come right back to the point in spacetime from which it left: otherwise, the amount of mass in the universe wouldn’t remain constant. You can cheat the law temporarily—for a certain, rather unusual definition of the word ‘temporarily’—but you can’t cheat it permanently. Though the nice thing about the way the device works is that when we perform runs like this, we get the results literally instantaneously.”

  “Even if the results are null,” Alicia cut in, “again and again and again.” She’d finished repairing Arachne and replaced her plastic shell. “Carson, we’re just about ready for run 328.”

  “Isn’t Philip going to be here for this?” Kate asked.

  “Not this one,” said Carson. “He only watches the runs every once in a while: most of the time he stays in his office while they’re happening. I asked him about it once: he said that the odds of any given run being successful were so low at this point that his time was better spent doing research; and even if a given run did work, we wouldn’t actually see the causality violation happen, because from our point of view there’d be nothing to see. We’d only be able to observe the result. And there was no real value to getting the result as soon as you could: the news would be the same fifteen minutes later. Keep in mind that we’re talking about the same guy who claims not to understand why you’d spend three hours watching a football game when you could just check the score online as soon as it was over.

  “Of course, this doesn’t mean that his loyal underlings don’t have to execute every run and observe it firsthand. In the lab we’ve gotten used to Philip’s philosophical arguments possessing a certain…expediency.”

  One song on Alicia’s stereo ended and another began. “This is SWV,” she announced. “SWV stands for Sisters With Voices.” She’d placed the robot spider on a desk, where Randall was fastening an LCD digital clock to its body with a pair of plastic zip ties.

  “For all the equipment we’ve got here,” Carson continued, “the conception of the experiment is actually pretty simple. We’ve strapped an atomic clock to this robot—well, it’s not really an atomic clock in and of itself, but it receives a signal from a real atomic clock located in Boulder, Colorado: it’s the official time clock for the United States.”

  “Have you ever sent a person in there instead of a robot?” Kate asked. The idea dawned on her by the time her question was halfway finished: “I want to look in there!” Her right foot was already taking an eager step toward the device, as if of its own accord.

  Alicia looked up from the robot. “Are you a physicist?”

  Kate stopped and turned; she meant to inject a note of sarcasm into her response, but even in her own ears her voice sounded too much like pleading. “Well, no, but—”

  “Then stay away from the causality violation device, please. Physicists touch. Tourists look.”

  Kate quickly cued up a couple of sharp-tongued retorts—oh, she had something in mind to say that would age the woman three months when she heard it—but when she saw Alicia’s steely, unblinking squint, what actually came out of her mouth was a whiny, “Well, I just wanted to see what it was like in there.”

  Alicia’s silent return to her robot was somehow more damning than anything she could have actually said. Kate glanced at Randall, who suddenly became deeply interested in the zip ties that attached the clock to the robot, making sure they were extra tight.

  “Kate,” Carson said softly after a few moments, in a tone that Kate found irritatingly conciliatory, “the thing is that it doesn’t actually look like much of anything in there. Because even though our instruments say the thing is working, at least most of the time, direct observation indicates that it isn’t. You’d think that if you were to enter an area that for all practical purposes exists at two different points in spacetime, you’d see some kind of effect, like some trippy lights, or a doubled image, or something. Or at least you’d think that you could close the door to the chamber in the present and open it again to look out on the past. But nothing happens. Philip’s been in there; Alicia’s been in there; I’ve been in there. Some of the people from DAPAS who are paying for these shenanigans have been in there. We’ve never seen anything interesting. You go in the chamber; you close the door; it’s dark; you open the door and see the same thing you saw before. It’s about as exciting as entering a dressing room in a department store.” He tentatively placed a hand on Kate’s shoulder, a gesture she found hard to read. “Sorry to be so anticlimactic.

  “Now. The robot, with the clock attached. We send it into the causality violation chamber, which is set—or should be—so that within it, time’s arrow is pointing toward the past end of the wormhole. It leaves the chamber and exists in the past for an hour; then it returns under its own power. Its reentry into the chamber trips a mechanism that should make time’s arrow within the wormhole point toward us, here in the present. When it comes out again, its clock should show that an hour has elapsed, even though to us it’ll look as if no time has passed at all. And we should receive confirmation of our firsthand observations when Arachne’s clock has to re-sync with the clock in Boulder. Simple enough.”

  Meanwhile, Randall had swiveled open the door to the causality violation chamber, and Alicia had placed the robot on the floor before it. “Beginning run 328,” she said, as the graduate student began to type figures into a spreadsheet on his laptop. “The time display on the robot’s clock is fifteen eighteen and thirty seconds.”

  “Sync with the U.S. time clock is exact,” Randall said.

  “This is all very exciting,” Kate said.

  “I’m glad you think so,” said Alicia. “Sending it in.”

  She flipped a swit
ch on Arachne’s spine, and the robot jerked to life as the colorful gears inside her transparent plastic shell began to turn. With the nervous jitteriness of a bride walking down the aisle, the robot marched toward the causality violation chamber, bearing the clock on her back. Even though Carson had said that the interior of the chamber was nothing special, when Kate looked inside it she thought that it looked too dark, as if some smoky malevolence out of a fantasy novel were living in there, swallowing all the light that fell on it.

  Arachne disappeared into the blackness of the chamber, and the door slammed shut behind her.

  “Now the rest is automatic,” Carson said. “By the time I started speaking this sentence it had already happened. If everything worked correctly—and there’s always a chance that it did, however small—our computers interfaced with the Planck-Wheeler clock to open up the past end of the wormhole; the robot exited the causality violation chamber into the past, where it spent an hour; then it reentered the chamber and returned to the present.”

  “Chamber door’s opening,” Alicia said.

  Arachne emerged from the chamber, stumbled forward on her legs, and came to a stop.

  Alicia checked the time on the robot’s clock. “The time reads sixteen nineteen and fifteen seconds.”

  Randall dutifully typed the figures into his laptop. “Sync with the U.S. time clock is still exact,” he said. “Sixteen nineteen fifteen.”

  “And that’s run 328! Good night, folks: you don’t have to go home, but you can’t stay here.”

  “That’s it?!” Kate said incredulously. “How is that even an experiment? Nothing happened! The robot went in and came out and that was it! That’s like nothing!”

  “They’re so cute when they’re young,” Alicia said, picking up Arachne and carrying her away, cradling her as if she were a newborn child.