Deep Storm

"I'm not sure. I never stopped to consider."

And then-suddenly-Crane understood. And as he did, he felt an almost physically overwhelming mix of triumph and fear.

"Oh, no," he breathed.

"What is it?"

"The Waste Isolation Pilot Plant? Ocotillo Mountain? That's what we're sitting on top of."

Hui turned pale. "You don't mean-"

"That's exactly what I mean. All this time, we've been positing some benevolent, paternal race that's planted some wondrous technology deep in the earth for mankind to discover when we've become sufficiently advanced to appreciate it. But that's not it at all. The truth is the Earth has been used as a dumping ground for weapons or toxic waste-unimaginably dangerous toxic waste, too, given how advanced your friends from Cygnus Major are."

"That's what Asher was trying to tell you?"

"It's got to be-there's no other answer. That thing encased below the Moho, the thing Spartan is digging toward right now? It's a time bomb."

He paused a moment, thinking fast now. "That medical conference I mentioned? Finding a place to dump nuclear garbage is only part of the problem. The real problem is that the stuff is going to stay radioactive for longer than recorded history. How are we going to warn somebody, ten thousand years in the future, that they'd better stay away from Carlsbad or Ocotillo Mountain? Civilization as we know it will have been transformed utterly. So the Department of Energy is seeding the sites with what they're calling 'passive institutional controls.'"

"Warning markers."

"Exactly. Not just one kind, either, but a wide variety-pictures, symbols, text. To tell our descendants the site has been isolated and sealed off for good reason. There were rumors of active controls, as well."

"But how can you be sure what's below us is dangerous?"

"Don't you see? Those sentinels we uncovered as we've dug-they're 'institutional controls,' too, in their own way. And those signals they're sending out are warnings."

"They're just mathematical expressions."

"But think what kind of expressions they are. They're impossible. When Asher first decrypted the message and thought he'd gotten it wrong, you know what he said? 'Division by zero is forbidden by all the laws of the universe.' And that's the key word: forbidden. Every single expression those sentinals are transmitting-zero to the power of zero, the others-they're all forbidden."

"Because whoever did this couldn't use a warning that was language based."

"Precisely. Only mathematical formulas are universal." He shook his head. "And to think of Flyte, and his talk of irrational numbers. He was more right than he knew. I think."

"Who?"

He gave a soft laugh. "Never mind."

Hui thought for a moment. "Why did they start with just one expression-and then begin broadcasting thousands?"

Crane shrugged. "Maybe they thought that division by zero was the simplest, most basic-that's why it was so pervasive. Maybe my touch triggered new behavior in the sentinel. Or maybe the fact that we hadn't stopped digging convinced the devices that we hadn't taken the hint-that we needed supplements."

He turned abruptly, took a step toward the door. All of a sudden, a sense of terrible urgency filled him: with every new minute, the digging brought them closer to an unthinkable oblivion.

"Where are you going?" Hui asked.

"You're looking at one guy who finally has taken the hint."

"What about me? Where should I go?"

"Stay here. It's as safe as anywhere-probably safer, because it's already been searched." He took her hand again, gave it a reassuring squeeze. "I'll be back for you-soon."

She took a deep breath. "Okay. Maybe I'll take another look at that initial transmission. The one Dr. Asher didn't translate."

"Excellent idea," Crane smiled. Then he stepped up to the lab door, paused to listen, and quickly slipped out into the corridor.

44

Admiral Spartan stood silently, looking at Crane. They were standing in a quiet corner of the observation chamber, and the only light came from the long window overlooking the Drilling Complex. The light was not sufficient to betray the expression on the admiral's face.

Crane glanced at the technicians and engineers, sitting at their monitoring stations. Then he looked down into the hangar. A crew of workers was prepping one of the remaining two Marbles for its descent. Even from this vantage point, there seemed to be a palpable excitement in the air: it seemed they were now just days, perhaps hours, from reaching the Moho, and any of the next few trips could be the breakthrough dive.

He returned his gaze to Spartan.

The admiral seemed to rouse himself from deep contemplation. He clasped his hands behind his back. "Let me get this straight. All the mysterious illnesses, the psychological problems, are the result of a signal?"

"It's the same digital signal the sentinels first transmitted via light waves. Except this other signal is transmitted in some way our technology can't pick up. And it triggers a highly abnormal spiking of theta waves in the brain. See, the brain works on electricity," Crane explained. "When that electricity misfires, it affects the autonomous nervous system. That in turn can cause nausea, visual field defects, arrhythmia-all the neurological deficits we've been seeing. It can also affect the frontal lobe of the brain. And that in turn accounts for the problems with memory and concentration, changes in character, even psychotic episodes."

"How can we counteract it? Negate its effects?"

"The signal? We can't even track it. The only solution is to avoid it. Stop the dig, get people to the surface, away from the source."

Spartan gave a dismissive shake of his head. "And this signal is transmitting a mathematical expression."

"Asher decoded several signals. All mathematical expressions, all impossible."

"You're saying they're a warning of some kind."

"The expressions are all forbidden by universal law. What better way to signal danger, when language isn't an option?"

"What better way, Doctor? Something more articulate. More direct."

Crane thought he heard skepticism in Spartan's tone. "Whoever planted these objects beneath the Moho-whoever created the sentinels-is clearly far, far more advanced than we are. Who's to say they aren't transmitting signals that are, as you say, more articulate-but we just aren't smart enough yet to intercept them?"

Spartan pursed his lips. "And we're the proud owners of an interstellar toxic dump. Or, perhaps, a cache of doomsday weapons from some distant arms race."

Crane didn't answer. The silence lengthened. Over his shoulder, he could hear the distant murmur of conversation, the clicking of keyboards.

At last, Spartan exhaled slowly. "I'm sorry, Doctor, but it all sounds very circumstantial to me. In fact, I have to wonder whether your own theta waves aren't begi

"No, not us. They couldn't care less about us-the violence of the original burial event proves that. We're insects to them. The civilization that did this probably comes from an environment of methane and sulfuric acid. Oxygen and nitrogen may even be toxic to them. They're not concerned about us; to them the Earth is a useless planet, and we're too primitive to deserve consideration. It's only a freakish chance we discovered their message in the first place. They're concerned about civilizations far more advanced. They're warning them to stay away from Earth."

Spartan did not reply.

After a moment, Crane sighed. "You're right. It is circumstantial. There's no way to conclusively prove what's down there without penetrating the Moho. But that's like saying a grenade is circumstantial until you pull the pin."