Supersymmetry (14 page)

“I'm not going to kill it.” He turned back to Sandra. “Why can't the eagle instantaneously travel over here, to our ridge?”

“It can't fly that fast.”

“What if it was a really good flier?”

Sandra rolled her eyes. “It couldn't fly faster than the speed of light, so it still couldn't do it instantaneously.”

“Exactly. Alex, I think your sister's smarter than you.”

Alex stuck out her tongue.

“So, we could describe the places the eagle could theoretically fly with a sphere, expanding as time passes. In the first nanosecond, it could reach no more than about a foot in any direction, even flying at the speed of light. In two nanoseconds, two feet in any direction.”

“Okay, with you so far.”

“We call that a light cone, and I'd show you how we draw it if I had some paper.”

“Why doesn't that bother you?” Alex said.

Ryan turned, confused. “What? Not having paper?”

“No. You're afraid of taking the elevator, yet you crouch at the very edge of a cliff, and you don't blink an eye.”

Ryan glared at her. “I'm not
afraid
of taking the elevator. I just don't trust the people who built it. This cliff is a different matter. It's solid stone. It's not going anywhere.”

“If you say so.”

Ryan turned back to Sandra. “As I was saying, our expanding sphere image isn't quite accurate.”

“Why not?” Sandra asked.

“The planet,” Alex said.

“Two points for the ugly sister,” Ryan said.

Alex rolled her eyes. “Nice.”

“The point is, the sphere will be slightly deformed toward the Earth,” Ryan said. “Our speed-of-light eagle can fly farther toward the Earth than it can away from it.”

“Because of gravity?” Sandra asked dubiously.

“That's right. Earth's gravity isn't a pulling force, like a giant magnet attracting things toward itself. Gravity deforms space-time. Even a beam of light, which has no mass, will bend when it passes by a massive planet. So our speed-of-light eagle will actually travel farther if it flies toward the Earth than if it flies away from it, though by only the tiniest amount. Our sphere is deformed, but not noticeably. So, what would happen if we made the Earth more massive?”

“The sphere of possible places it could go would deform more,” Sandra said.

“Right.”

“Wait a minute, though. You're talking about the places the eagle could theoretically fly in a given amount of time. It could fly here, but not to China. But haven't we been breaking that law all day? Haven't we been teleporting to places outside our own light cone? Traveling faster than the speed of light?”

Ryan grinned. “Sort of. It's all part of the puzzle. One thing at a time: what if we put a black hole near the eagle? How would that affect its light cone?”

Sandra looked at Alex, but they were both looking at her, waiting. “I don't know,” she said. “It would deform the sphere even more, I guess.”

“That's right,” Ryan said. “In fact, it would deform the sphere so much that it couldn't fly away from the black hole at all. Even flying at the speed of light in the other direction, it would still end up traveling toward the hole. It wouldn't be able to escape the hole's gravity, any more than light itself can. Space-time is warped so badly that the bird is unavoidably sliding down the slope toward it. But let's keep going. What if we keep adding mass to the black hole?”

“The slope increases. The bird slides toward it faster.”

“Yes. And if we keep on going?”

“Um . . . faster still?”

“Eventually the slope becomes vertical. At that point, the bird isn't sliding toward the black hole; it arrives there instantly. What if we add even more mass?”

Sandra shrugged. “You're going to tell me, I bet.”

“Space-time becomes so warped that the slope is backward: the only solution to the equation is negative. Now, instead of a black hole, we call it a wormhole. Unlike the wormhole that connects my baby universe to ours, this one connects our universe in the present to a point in the past. The eagle is sucked through the wormhole and arrives before it left. Of course, it's been ripped apart into its constituent atoms, but besides that, it's fine.”

“What do you have against birds?” Alex asked.

“The point is, the topography of space-time allows time travel. Not for eagles or humans—the process would completely destroy us. But for single particles, yes. The NJSC, in fact, has successfully demonstrated time travel for Higgs singlets.”

“I know you're a genius and all, so you probably know what you're talking about,” Sandra said. “But there's a paradox here, right? If something goes back in time, there's always the possibility that it can interfere with its own creation. Like going back in time and killing my own grandfather. What if the Higgs singlets, traveling back in time, get in the way of the protons that were about to collide to create them? Or what if you use the singlets to send your past self a message, warning you not to perform the experiment in the first place?”

Alex spoke up. “The universe won't allow it.”

“The universe?”

“That's right.” She looked at Ryan. “May I?”

Ryan made a mock bow.

“All right,” Alex said. “I think we've exhausted the eagle analogy. Let's move on to billiard balls.”

Sandra crossed her hands in her lap and looked up with an attentive expression, as if in class.

“The problem you raise is called Polchinski's paradox,” Alex said. “Say you roll a billiard ball through a wormhole, so that it goes five seconds back in time.”

“Okay.”

“Only, you roll it through the wormhole at such an angle that it hits its earlier self, thus preventing itself from rolling into the wormhole in first place.”

“That's what I'm saying. It's a paradox.”

“And that's why it can't actually happen,” Alex said.

“
Can't
happen? Who says? Is there a referee that cries foul and takes you out of the game?”

“Not exactly. But the universe can't contradict itself. There's a natural law that says self-consistency is always conserved. If you roll the ball through the wormhole at its past self, then either it will miss entirely, or else it will deliver itself a glancing blow that will knock it into the wormhole at such an angle that it will give itself that glancing blow,” Alex said.

“You're kidding,” Sandra said. Then she made a connection in her mind, and without thinking, said, “It's called the Novikov self-consistency principle, isn't it?”

Ryan's surprise was obvious on his face. “You really did grow up with a physicist father, didn't you?”

Sandra shrugged, surprised herself. “I guess so.”

“Well, you're right,” he said. “It's the only way the math works out. In fact, this specific case, with billiard balls, has been studied.”

Sandra raised an eyebrow. “People have been sending billiard balls back in time?”

“No, I mean mathematically. Echeverria and Klinkhammer set up a computer simulation with billions of variations. They showed empirically that, not only do most conditions have multiple solutions, but that there are
no
initial conditions for which no self-consistent solution exists. It's actually where my work started.” Ryan's excitement grew as he spoke. “The universe is a giant quantum computer, remember? It takes these complex consistency problems and solves them. It's doing it all the time.”

Sandra grew sober. “And the varcolac fits into that somehow, doesn't it?”

“It's a sentient manifestation of that quantum computer,” Alex said. “It's like an artificial intelligence, only on a vaster scale.”

“You're saying the varcolac
is
the universe?”

“No. Or at least, I don't think so. It's an intelligence born out of the quantum complexity of the universe. We don't even know if there are many of them, or only one. Or if that distinction even has meaning to a being like that.”

“And it can travel in time?”

“
I
can travel in time,” Ryan said. “At roughly the rate of one minute every minute.”

Sandra made a face. “At some other rate than the usual,” she clarified.

“No. Not travel, exactly, not like you're thinking. It wouldn't be able to send its intelligence back to a point in the past; that would be like rewinding the particle interactions of the universe. But could it send a Higgs singlet back in time on exactly the right trajectory to cause a chain reaction that destroys a baseball stadium? Yes. I think it might very well be able to do exactly that.”

Sandra felt suddenly tired and sad, overwhelmed by the conversation. It wasn't just a distracting intellectual exercise anymore. She spoke quietly. “Why? Why would it do such a thing?”

“I don't know,” Oronzi said. “Maybe your father would have found a way to stop it, and it could see that somehow.”

Alex stood up and stretched. “This is all a possible explanation, but how do we test it? How can we know if that's really what happened, or if it's just a wild fantasy?”

“We go back to the lab,” Oronzi said. “We pore through the logs, double-check the math, look for anomalies. See if we can find when such a thing might have happened.”

Sandra shook her head. “You two go. I need to be alone for a while.”

“Are you okay?” Alex asked.

Sandra smiled wanly. “Not exactly.” In truth, she wasn't okay at all. Her father was dead, and she had hardly even paused to let that truth sink in. Her mother was all alone, and instead of helping her when she needed them the most, they were worrying about murder charges and time-traveling quantum creatures. “Has anyone even told Claire? Or Sean?”

“I'm sure Mom called them.”

“There's going to have to be a funeral, you know. They'll arrest you, if they see you there.”

Alex shrugged. “That's all right. I don't need to go.”

“We could switch. We'll wear the same dress. I'll go into the bathroom with a GPS, then I can teleport out, and you—”

“No.” Alex took Sandra's shoulders. “You go. I don't want to see him like that.”

Sandra nodded. “All right.”

“I need to get back to the lab,” Ryan said. “If we're right about the varcolac changing the past, we need to understand how it works.”

“I'll come, too,” Alex said.

“Okay,” Sandra said. “I'll see you later then.”

“What are you going to do?”

“I'm going to walk down the mountain. I just need some time to think. Then I'll go find Mom.”

“Later, then.”

“Later. And Alex?”

Alex turned. “Yes?”

“It's not your fault.”

Alex made a tiny shrug, noncommittal, and frowned. “Thanks.”

Ryan and Alex made eye contact and then teleported away, leaving Sandra alone on the mountain. Sandra took the trail leading from the peak back down to the road. She was still wearing her police uniform, which attracted looks from the other hikers, but the slope was an easy one, and the walk pleasant. She soon settled into a comfortable pace. The pretty, wooded surroundings and the sound of birdsong increased her melancholy.

In truth, it was more than just her father's death that was bothering her. She was certain, quite certain, that she had never heard of the Novikov self-consistency principle, and yet she had come up with the name in an instant. She wanted to tell herself that she must have heard of it a long time ago, when she was a child, and it just came bubbling to the surface of her memory at that moment. But she knew that wasn't true.

It was Alex's memory. Her sister knew very well what the Novikov self-consistency principle was, and Sandra had accessed that knowledge as if it were her own. It was what had happened fifteen years ago to her father, shortly before he resolved into a single person, after having been split in two for months. It made her afraid that their probability wave, after all this time, was in danger of collapsing. Maybe the reason they had remained two individuals for so many years was because the varcolac was gone. Now that it was back, maybe they would resolve into one person again.

And what if they did? Who would Alessandra Kelley be? She and Alex were such different people now, with different skill sets, different desires, different relationships, different lives. Would either of them survive in any meaningful sense? Or would one personality dominate, and the other, for all practical purposes, die? Sandra was afraid that if it came down to strength of personality, there wouldn't be very much of her personality left.

She thought of her father, and his brief split before death. How awful for her mother, to have him home, to think him safe, and then to have him so suddenly gone. She ought to visit her. Sandra checked her phone and found the GPS log. She had made calls when in her old bedroom, and the data was still there. No one would be in her room.

On her eyejack system, she brought up the menu of quantum functions that Alex had copied for her. There was a professional-looking menu with a military feel and a tiny Lockheed Martin logo. The options were tagged with unfamiliar icons and words like State Spin, Diffract, Tunnel, Attraction, and Probable Split. The only one she was familiar with was Teleport, and it didn't seem very safe to experiment with the others. She accessed the teleport function, and her bedroom materialized around her.

She grinned. It was such a rush, doing that. She barely understood how it was possible. She didn't even have as much as a battery on her to provide the power. There was so much energy bound up in the basic structure of the universe. Technology like this would make primitive techniques like burning fuel a thing of the past. If they could learn how to tap it without calling murderous alien creatures out of the space between the atoms, that is.