Lucifer's Hammer - Larry Niven [40]
"No, no, stay and hear this," Sharps said. "Let me introduce Dr. Dan Forrester. His job title is computer programmer. His degrees say Ph.D. in astronomy; around here we usually call him our sane genius."
Mark was muttering behind Harvey. "If they call him a genius in this outfit … "
Harvey nodded. He'd thought of that too.
"Dan's been doing more recasts of Hamner-Brown's orbit. He's also working on the optimum launch date for our Apollo, given the limited amount of equipment we can take, and the limited amount of consumables—"
"Consumables?" Harvey asked.
"Food. Water. Air. They take mass. We can only put up so much mass, and so we trade consumables for instruments. But consumables mean time in orbit. So Dan's working on the problem: Is it better to launch earlier, with less equipment, so they can stay longer but get less information—"
"Not information," Forrester said. His voice was apologetic. "Sorry to interrupt—"
"No, tell us what you mean," Harvey said.
"We're trying to maximize information," Forester said. "So the problem is, do we get more information by having more data about a shorter time, or less data about a longer time."
"Oh." Harvey nodded. "So what have you got on Hamner-Brown? How far away at its closest point?"
"Zero," Forrester said. He didn't crack a smile.
"Uh—you mean it's coming down our throats?"
"I doubt it." Now he smiled. "Zero within the limits of prediction. Which is a good half-million miles error."
Harvey relaxed. So, he noticed, did everyone in the room, including Charlene. They took Forrester seriously here. He turned to Sharps. "Tell us, what would happen if the comet did hit us? Suppose we got unlucky."
"You mean the head? The nucleus? Because it looks as if we might actually pass through the outer coma. Which is nothing more than gas."
"No, I mean the head. What happens? The end of the world?"
"Oh, no. Nothing like that. Probably the end of civilization."
There was silence in the room for a moment. Then for another. "But," Harvey said, his voice puzzled, "Dr. Sharps, you told me that a comet, even the head, is largely foamy ice with rocks in it. And even the ice is frozen gases. That doesn't sound dangerous." In fact, Harvey thought, I asked to get it on the record.
"Several heads," Dan Forrester said. "At least it looks that way. I think it's beginning to calve already. And if it does it now, it will do it later. Probably. Maybe."
"So it's even less dangerous," Harvey said.
Sharps wasn't listening to Harvey. He rolled his eyes toward the ceiling. "Calving already?"
Forrester's grin widened. "Ook ook."
Then he noticed Harvey Randall again. "You asked about danger," he said. "Let's look at it. We have several masses, largely the same material that boils off to form the coma and the tail: fine dust, foamy frozen gases, with pockets where the really volatile stuff has been long gone, and maybe a few rocks embedded in there. Hey—" Randall looked up at Forrester.
Forrester was grinning his cherubic smile. "That's probably why it's so bright already. Some of the gases are interacting. Think what we'll see when they really get to boiling near the Sun! Ook ook."
Sharps was getting that thoughtful, lost look again. Harvey said quickly, "Dr. Sharps—"
"Oh. Yes, certainly. What happens if it hits? Which it won't. Well, what makes the nucleus dangerous is that it's big, and it's coming fast. Enormous energies."
"Because of the rocks?" Harvey asked. Rocks he could understand. "How big are those rocks?"
"Not very," Forrester said. "But that's theory—"
"Right." Sharps was aware of the camera again. "That's why we need the probe. We don't know. But I'd guess the rocks are small, from the size of a baseball to the size of a small hill."
Harvey felt relief. That couldn't be dangerous. A small hill?
"But of course that doesn't matter," Sharps said. "They'll be embedded in the frozen gases and water ice. It would all hit as several solid masses. Not as a lot of little chunks."
Harvey paused to think that over. This film would take careful editing. "It still