Utopia

“How the devil can we abort after the diversion?” Kresh demanded.

“As you know, the whole body of the comet has been rigged with explosive charges, intended to break the comet up into the desired number of fragments just before impact.”

“What of it?”

“Virtually all of those explosive charges have been damped down, or directionalized in one way or another, mostly by means of shaped forcefields. The plan is for these controlled charges to be set off one at a time in a very carefully planned sequence, so as to limit undesired fragmentation and lateral spread. By shutting down all the damping and directionalization, and by detonating all of the explosives in a different order, and much more rapidly, it should be possible to disintegrate the entire comet, reducing it to a cloud of rubble.”

“But the whole cloud of rubble will still be headed right for the planet,” Kresh objected. “It will all hit the planet, in a whole series of uncontrolled impacts.”

“That is not quite correct, Governor. If the blasts are done in the right way, and far enough before the impact, the explosion will give the vast majority of the material a large enough lateral velocity that it will miss the planet completely. Our model shows that, even in a worst case scenario, over ninety percent of the comet debris will miss the planet and continue on in its orbit about the sun. Of the ten percent or so of the debris that does strike the planet, ninety percent will strike in areas already slated for evacuation, or in the open waters of the Southern Ocean.

“That still leaves something like one percent of the comet coming down in uncontrolled impacts,” Kresh said.

“And some areas will experience a brief period of increased danger,” Dee replied. “Small pieces of debris will fall all over the planet, for about 32 hours after detonation-however, the impact danger for most inhabited regions will be on the order of one strike per hundred square kilometers. Persons in most areas would be in more danger of being struck by lightning in a storm than by being hit a piece of comet debris.”

“But some areas will be more trouble,” Kresh suggested.

“Yes, sir. The closer one gets to the initial target area, the higher the concentration of impacts. However, all the persons in such areas are to have taken shelter as a precaution in any event. If those plans are followed, I would estimate something on the order of one impact per square kilometer in the populated areas of maximum danger-and most of those strikes corning from objects massing under one kilogram.”

Kresh thought for a moment. “How late?” he asked. “What’s the last possible moment you could detonate the comet?”

“In order to stay within the parameters I have described, I would have to perform the explosion no later than ninety-two minutes, fifteen seconds before the scheduled impact.”

“Not bad, Dee,” said Kresh. “Not at all bad.”

Fredda and Soggdon were both listening in on their own headphones, alarmed looks on their faces. Fredda signaled him to cut the mike with an urgent throat-cutting gesture. Soggdon nodded and made the same gesture.

“Just a moment, Dee,” Kresh said. “I want to think about this for a minute. I’ll be right back.”

“Very good, sir,” Dee said.

Kresh cut his mike and took his headset off. “What’s the problem?” he asked. “Why does that idea worry you two so much? I have to admit it sounds pretty damned tempting to me. It gives us a lot more room to maneuver.”

“That’s not the point,” Fredda said. “That’s a robot talking. A robot casually talking about dropping thousands meteorites on the planet at random!”

“But even with fifty thousand-a hundred thousand meteorites-the odds against significant danger to a human being are-”

“Tremendous,” said Donald. Only a First Law imperative could have made him dare to interrupt the planetary governor. “They are unacceptably high. And I would venture to add that any sane Three-Law robot would endeavor to protect a human in danger of being struck by lightning. That level of danger is not negligible.”

“Not to a robot it isn’t,” Fredda agreed. “Or at least it shouldn’t be. To a human, yes, but not a robot.”

“Hold it,” said Kresh. “You’re upset because Dee isn’t overreacting to danger?”

“No,” said Fredda. “I’m upset because this makes me question Dee’s sanity. A robot would have to be on the verge of becoming completely unbalanced to even suggest something that might cause widespread, uncontrolled danger to humans.”

Kresh looked toward Soggdon. “Your opinion, Doctor?”

“I’m afraid I’d have to agree with Dr. Leving,” she said. “But what I find troubling is that all our reading and indicators show Dee’s level of First Law stress has been well within normal range right along. She ought to be flirting with the maximum tolerance levels, given the operations she’s dealing with. And yet, if anything, her readings are a little in the low range.”

“Maybe you ought to have a little talk with her about it,” Kresh suggested.