“What we’ve done,” said Pickett into his recorder, when at last he had time to think of the audience he had never expected to speak to again, “is to build a computer out of human beings instead of electronic circuits. It’s a few thousand times slower, can’t handle many digits, and gets tired easily—but it’s doing the job. Not the whole job of navigating to Earth—that’s far too complicated—but the simpler one of giving us an orbit that will bring us back into radio range. Once we’ve escaped from the electrical interference around us, we can radio our position and the big computers on Earth can tell us what to do next.

“We’ve already broken away from the comet and are no longer heading out of the solar system. Our new orbit checks with the calculations, to the accuracy that can be expected. We’re still inside the comet’s tail, but the nucleus is a million miles away and we won’t see those ammonia icebergs again. They’re racing on towards the stars into the freezing night between the suns, while we are coming home…

“Hello, Earth… hello, Earth! This is Challenger calling, Challenger calling. Signal back as soon as you receive us—we’d like you to check our arithmetic—before we work our fingers to the bone!”