ACKNOWLEDGMENTS

For information, advice, and much else, I owe thanks to Karen Anderson (as always), Victor Fernandez-Davila, editor Robert Gleason, the late Kenneth Gray, G. David Nordley, and Aharon Sheer. Special thanks are due Robert L. Forward and Sidney Coleman. The idea of a nuclear "time machine" is the former's. An idea of the latter's suggested the concept behind the zero-zero drive to me; he kindly sent me a copy of his paper, but it turns out that my speculation is quite unlike his real-science thought and may even contradict it.

The lines of verse quoted in Chapter III are from The Book of Songs, translated by Arthur Waley copyright © 1937, renewed 1965 by Arthur Waley, by permission of the publisher, Grove/Atlantic, Inc.

The lines of verse by Jorge Luis Borges and their English translation by Richard Howett and Cesar Rennart quoted in Chapter IX are from Selected Poems 1923-1967 by Jorge Luis Borges, edited by Norman Thomas di Giovanni, copyright 1968, 1969, 1970, 1971, 1972 by Emece Editores, S.A., and Norman Thomas di Giovanni, by permission of the publisher, Bantam Doubleday Dell.

The lines of verse by Rudyard Kipling quoted in Chapter XVII are in the public domain.CHAPTER XXI first appeared in a different form as "Ghetto" in The Magazine of Fantasy and Science Fiction, May 1954, copyright © by Fantasy House, Inc., renewed 1982 by Poul Anderson. The lines from the ballad "Jerry Clawson" quoted in it are copyright by the author, Gordon R. Dickson, and used by his permission.CHAPTER XVII first appeared in a slightly different form as "The Tale of the Cat" in Analog Science Fiction and Fact, February 1998, copyright © 1998 by Poul Anderson No person here named is in any way responsible for any mistakes or other flaws in this book.