“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?”