TO LARRY AND MARILYN NIVEN

ACKNOWLEDGMENTS

For advice, information, suggestions, encouragement, and much else I am indebted to Karen Anderson (first and foremost as always), Gregory Benford, CJ. Cherryh, Larry J. Friesen, Robert Gleason, Alan Jeffery, Mike Resnick, and S.M. Stirling. They are not responsible for any errors or other infelicities that remain in this book, but without them there would have been many more.

It is clear that I have also drawn on the thoughts of Freeman Dyson, Hans Moravec, Roger Penrose, Gunther S. Stent, and Frank J. Tipler, Again, nothing bad is their fault, the more so since I have often contradicted this or that in their writings. For that matter, some of their own ideas disagree with each other. All are immensely interesting and reach for the very heart of truth.