“But these are tiny explosions,” Leclerc said, looking over her shoulder.
Judy nodded. “Schooner was 35 kilotons, Sedan a tenth of a megaton. But I agree, mostly like Jangle or Teapot they were just a kiloton or two. You don’t want the neighbours screaming when you set off your A-bombs.”
“Can you do a least squares fit?” McNally asked.
“It’s been done.” She clicked again, and a graph appeared on the screen. Shafer got there first: “So, if we believe the fit, a one-megaton surface bomb excavates a crater six or seven hundred metres across. The crater could be as big as Nemesis. We’d shatter it.”
“Maybe, maybe not,” Sacheverell said.
“Let’s run with a megaton for a while,” Webb proposed.
“It is not enough to know the size of the crater,” Leclerc pointed out. “We need also to know its depth before we know the volume excavated.”
Back to the table. A red-painted fingernail traced along a row. “Jangle S was a surface burst. It had a depth about half its diameter.”
Sacheverell said, “These bomb craters were made in terrestrial gravity. How can we trust these results on Nemesis?”
Leclerc was scribbling on the back of an envelope. “Shall we ignore details like gravity? If we extrapolate Judy’s figures we find we could excavate maybe fifty million tons of Nemesis with a megaton bomb.”
“We can also get at it from the crushing strength of rock,” Webb said, “Assuming Nemesis is made of rock. If it takes 5 × 108 ergs to crush a gramme of medium-strength rock, and a megaton is 4 × 1022 ergs, Willy’s bomb has the energy to excavate eighty million tons.”
Shafer frowned. “Once again making a hole as big as the asteroid. Meaning we probably break it into thousands of fragments, and shower America with super-Hiroshimas.”
“Now hold on,” said Sacheverell. He sat down next to Judy and rapidly typed in an instruction. A coal-dark, pitted surface filled his screen. “I’m into JPL and this is Mathilde, a near-Earth asteroid. It has a crater practically its own size and it held.”
“Okay, say for now that we blast a hole in its side and Nemesis stays in one piece. Would it hit or miss?” Noordhof wanted to know.
“We still need to know the speed of the ejecta,” McNally said.
“So let’s work it out. How fast do your nuclear explosions take place, Judy?” Shafer asked.
“The energy release is over in about a hundredth of a microsecond. It comes out as an X-ray pulse. Ground heating is complete in less than a microsecond. The trouble is, it gets so hot in that microsecond that the ground just reradiates most of the energy back. Only about five per cent goes into making a crater.”
Shafer said, “We hit Nemesis with a one-megaton bomb. It stays intact. A twentieth of the energy goes kinetic. So use 1/2mv2 and believe André’s fifty million tons of ejecta to get at v.” He scribbled rapidly and Webb let him get on with it. The physicist turned back from the board. “The debris recoils at a hundred metres a second.”
“In all directions,” Webb reminded him.
Shafer nodded his agreement. “The horizontal components of motion just cancel. The actual orbit shifting is done by the vertical velocity component, which will be fifty metres a second. Are you still with us, Jim lad?”
NASA’s Chief Administrator said, “You’re telling me that if I deliver a one-megaton bomb I can blast about five per cent of the asteroid’s mass into space at 50 m/s. Times 3,600 gives me 180 kilometres an hour. So how fast does Nemesis recoil?”
Sacheverell said, “That’s high school stuff. From momentum conversation Nemesis itself is deflected at five per cent of fifty metres a second. Two metres a second.”
“Now hold on,” McNally said. “You’ve just told me we need thirty metres a second.”
Noordhof said, “Hit Nemesis a week before impact and you fail by a factor of fifteen to deflect it with a bomb. It looks like we need to catch this asteroid at least six months or a year out, Willy.”
Leclerc raised his hands in a Gallic gesture. “But for all we know it is only weeks out, maybe even days.”
Sacheverell said, “The Colonel’s right. We need an early warning.”
Shafer shook his head in disagreement. “We need ten or twenty years to map out the near-Earth environment down to the Baby Bears.”
Noordhof’s voice was beginning to border on desperation. “Are you listening? You have to find Nemesis a year out. Your own figures say so.”
“Mark, how do we know it won’t come in next week or next month?”
Noordhof rubbed a hand over his face. “This is bad news.”
Webb rubbed off the equations and scribbled some more on the blackboard. He came back and sat down heavily at the conference table, puffing out his cheeks. “It gets worse.”
Inquisition: the Witnesses
“Are you comfortable, Fra Vincenzo?” the secretary asked.
Vincenzo encompassed the room with a wave of the arm. “I have rarely seen greater luxury outside the Palace of His Serenissimo.”
The secretary smiled. “Better than the cells of the Sant’ Angelo. I suspect they are showing deference to your age.”
“I suspect your own hand in the matter, sir. Not only do I have this fine apartment in the Holy Office itself, I am allowed access to a wonderful library downstairs. If I need to, I may call on the wisdom of St. Thomas Aquinas, Scotus and other great scholars in preparing my Apologia.”
The secretary lounged back on a sofa. “So. They tell me you had a rough journey.”
“I contracted a fever. We had to put up for three weeks in Orvieto. They say I almost died, but I remember little of it.”
“The Altezza is of course concerned for you. He is also anxious that your works should not be lost.”
Unexpectedly, the old monk burst into laughter. “And faced with a choice between my life and my works, which is it to be? No, do not answer, my son. Ferdinand’s love of his library is known to all. And he is right. Human life is ephemeral, but my work — it may be of little consequence, but it will surely outlast these bones by many centuries. To be read and studied by men yet unborn. Can there be a closer approach to immortality on this Earth?”
“I fear they may end up on the Index.”
“I have another fear. Something I fear more than death.” Vincenzo poured a glass of red wine for his distinguished guest, and one for himself. His hand was unsteady. “And that is the torture. I do not believe I could withstand the strappado.”
There was a moment’s silence. The Medici secretary sipped the wine, and changed the subject. “All Florence is talking about your forthcoming trial. The students of Pisa set fire to the Inquisitor General’s carriage with the Inquisitor still inside. There was fighting at the University of Bologna between supporters and detractors of the new cosmology. The authorities called in the mercenaries.”
“That is bad news for freedom of thought.”
“And worse news for you, Vincenzo. The Church may feel that it has to make an example.”
“Is there no place in Europe where a thinking man can be safe? They say that Calvin even set aside Geneva’s laws to have Servetus burned alive. Bruno met the same fate in this city forty years ago.”
“And you repeat not only the Copernican heresies, but also those of Bruno. What a foolish old man you are, Vincenzo Vincenzi.” The secretary stood up. “I will be at the Villa Medici in the Pincio for a few weeks. I have asked His Holiness to bring you to trial within days if possible. You have the right to an advocatus, which the Duke will pay for. I have made enquiries. You will be defended by a man of good family. He is young, but already well spoken of amongst the business community of Rome.” He turned at the door. “If you fear the torture, Vincenzo, put yourself in his hands.”