“Classical probability theory would exclude human expectation from the result,” said Mr. Chowdry in a quiet voice, “but Expectation-Influenced Probability Theory postulates that the observer can and will affect the outcome of events purely by the weight of his own expectations. If enough people believe that HR-6984 will miss, then the eventline will bend to ensure that it does. Similarly, if we all believe that we’re going to die in a fiery cataclysmic event, we shall.”

I stared at him for a moment. The notion seemed . . . well, counterintuitive.

“I know the eventline can be changed,” I said, “but I always thought our intervention was limited to things we could physically alter due to choice and free will—not a chunk of rock the size of the Isle of Wight traveling through space at forty-two thousand miles per hour.”

Mr. Chowdry thought for a moment. “Take your brother Joffy and the Church of the Global Standard Deity as a case in point. For the past thousand years, the existence or nonexistence of God has bobbled around the thirty-two percent mark, given the multitude faith dilution. Once all the major religions were joined together the likelihood of His existence jumped to over eighty percent—and what happened?”

“He revealed Himself,” I said in a quiet voice.

“Right,” said Chowdry, “and once the atheists were on board, He began all this smiting. Without faith He is nothing. But with faith He is everything, and in this context ‘everything’ means real, dangerous, vengeful—and unknowable.”

“Is this proven?” I asked.

“Not at all, “replied Chowdry. “Expectation-Influenced Probability Theory is right on the edge of accepted mathematics. You should get over to the stage if you want to hear your daughter talk.”

I thanked Mr. Chowdry for his candor and walked away. If I had understood it correctly, the asteroid wouldn’t hit if we didn’t think it would. The trouble was, we thought very much that it would. To turn around the 81 percent, we needed something to change people’s minds—like some sort of proof or, failing that, doubt.

I pushed these thoughts to the back of my mind and headed toward the stage, where I could see Landen standing at the side with Tuesday, chewing her nails. Most of the five hundred seats had now been filled, and those unlucky enough to have been having a quick sandwich or a pee or something were standing at the back.

“You made it, Mum!” said Tuesday, giving me a joyfully nervous hug. “But where’s Jenny? Dad said she’d be with you.” I thought quickly. “She’s with Gran and Polly.”

“They said they wouldn’t be here.”

“They changed their mind. I was just talking to Mr. Chowdry about Expectation-Influenced Probability Theory. Does that make any sense to you?”