How much additional reality is there in this book? Are such wonders and nightmares as relativistic bombs, the cloning of founding prophets, VR addiction, the dominance of hydrothermal life over the Earth, antimatter-propelled starships, and attack from interstellar space, real possibilities? Yes and no, as follows:

1. Relativistic bombs. They violate no known laws, but they require vast amounts of energy for acceleration—which is in fact available. The concept of the R-bomb originated as an unanticipated offshoot of the Valkyrie brainstorming sessions (an informal “thought experiment” begun by Charles Pellegrino and Brookhaven National Laboratory physicist James Powell in 1984 and continuing into the present). Early Valkyrie designs required the development of the smallest hydrogen bombs (antihydrogen-triggered) ever conceived—smaller, in fact, than an amoeba. By firing sixty of these per second in a magnetic field, it became possible to imagine accelerating a spaceship up to ninety-two percent lightspeed—which is a nice speed to be traveling at, because anyone aboard will be aging at only one-third the rate of stay-at-home observers on Earth. (The bomblet approach is currently being abandoned in favor of a simpler, more efficient engine design: stay tuned.)

The realization, by early 1985, that interstellar flight did not present any insurmountable technological barriers and would in fact (assuming civilization could hold itself together) become reality by 2050, raised questions that had never been asked before, perhaps because the whole idea of relativistic spaceflight had always seemed like pure science fiction. One of these questions was: What if we strike a planet with a mass equivalent to a small space station at ninety-two percent lightspeed, or even thirty percent? This led to the concept of relativistic cluster bombs and a reexamination of Fermi’s paradox, and to the nicknaming of Powell and Pellegrino as “the Pablo Picasso and Salvador Dali of nukes.” (They have yet to figure out which one is supposed to be Picasso.)

2. The Valkyrie brainstorming sessions and their implications for alien contacts as suggested by the relativistic bomb problem—reality. For dramatic reasons we have taken some liberties with the chronology and for obvious reasons some of the names have been changed, but the actual matters arising (as presented in the ill-fated Ed Bishop’s file, which allows readers to look over the scientist’s shoulders, somewhat like flies on a wall) are so fascinating and chilling in their own right that we have had no real need to exaggerate them in any way.

Ed Bishop is also real. He in fact introduced the authors of this novel to each other at the Rensselaer Polytechnic Institute in 1988.

“George, you’ve got to meet Charles Pellegrino,” Bishop said to Zebrowski over the phone as part of convincing him to come to RPI’s science fiction convention, Genericon IV.

“Charles who?” Zebrowski answered.

“You’ll like him. He’s interested in everything! A real polymath—works in half a dozen sciences at once, and he writes, too!”

Yeah, yeah, yeah, Zebrowski thought to himself. But Ed Bishop was right. Within hours of meeting, Pellegrino and Zebrowski had plotted a short story, “Oh, Miranda!”, which became the cover story for The Magazine of Fantasy & Science Fiction in September, 1991. And the great Bob Eggleton did the cover painting. By the time that story was published, they were already at work on The Killing Star. They wrote their outline, Zebrowski came up with the title, then discovered that Pellegrino had once published a science article with the same title! It was a sign. We hope Ed Bishop appreciates our extrapolation of his life into the next century.