"It doesn't matter," said Rothman. "Avery was probably warned to mend his ways. I was. Or maybe he couldn't face the truth. I'm sure he's been much happier, the last few months, believing I'm crazy. Anyway, I don't blame him any more. Maybe my math will soon speak for itself. For your benefit--" he turned to Avery--"I may point out that the errors you said you found affect only the _velocity_ of the wave of disintegration. So what if that isn't quite right? The proof that the reaction will be self-sustaining is independent of that." Avery was white with rage. "The proof, as you called it, that the reaction will be self-sustaining and will consume the entire substance of the Earth doesn't make sense, either. You used D as an operator where it should have been a constant. That's what finally made them certain that you were insane." There was a rap at the door and Joe poked his head in. "Lunch, Professors! Twelve o'clock, high noon, like they say. How about some turkey sandwiches?" MacPherson began to sweat; the thought of food made him feel sick. Was it possible, he wondered, that in spite of everything, he was not quite sure? He looked at Neill and Avery, but they had turned their heads away. "We won't bother with lunch, Joe," said Rothman. "Must be a pretty good game if you won't even knock off to eat," said Joe. "Well, will you at least mark your menu for tomorrow?" "For tomorrow? Tomorrow isn't going to come, you know." "Nuts," muttered Joe as he closed and locked the door. "Pure nuts." Avery cleared his throat, and his voice was thin. "Look here, Rothman! If the Universe were composed of matter as unstable as you claim, it would have ceased to exist long ago. Somewhere, somehow, in the infinity of chance events since the creation of the Earth, something would have occurred to start the self-sustaining chain reaction, and all matter would have been annihilated." "Are you trying to prove something to yourself?" asked Rothman. "Surely you don't equate infinity with a mere four billion years. That's a finite time--long enough for the more dangerous radioactives to disappear completely, of course, but not long enough for all possible chance events to have taken place. Anyway, I never have asserted that the reaction would reach from Earth to the other planets, or even to the Moon. The Universe, including the Solar System, will still go on. But our old Earth is going up like a pile of magnesium powder mixed with potassium chlorate when you drop a lighted match on it." * * * * *