Book Review: Kinematic Self-Replicating Machines, by Robert A. Freitas Jr. and Ralph C. Merkle, Landes Bioscience, Texas, 2004

Self-replication is the process by which an object or structure makes a copy of itself. Over the last century, research in artificial self-replication has progressed along two major tracks: 1) cellular or computational selfreplication, which investigates the issue from a purely informational point of view (most notably using the cellular automata model), and 2) kinematic self-replication, which investigates self-replication in the context of physical machinery that can make copies of itself by using kinematic operations on physical matter, i.e., movement of materials through physical space in the physical world. Both tracks were pioneered by John von Neumann in the late 1940s [2]. The book by Freitas Jr. and Merkle deals mainly with kinematic self-replication, although it also provides an excellent review of the informational track. Perhaps the first thing that struck me mind as I opened this wonderful volume was the prodigious number of references: 3278! (I repeat: three thousand, two-hundred, and seventy-eight.) If this were the book’s only virtue, it would still be worth owning. Happily, the book exhibits many other merits. As I began the read I was quite delighted to note that the authors had elected a none-too-formal style of writing, rendering the reading a joy rather than a pain. Aside from the clearly explained technical issues the book contains numerous anecdotal sidelines, both within the text, and—most notably—in the footnotes. Caveat lector: Ignore the footnotes at your own peril! For example, Chapter 2 briefly biosketches von Neumann, with foot-