admit the cost is too high, and the two reach an agreement and continue their plotting. The critical moment comes when the Emergents attempt to provoke a nuclear war on the Spider home-world in order to seize power. The conspirators subvert the Emergents' systems and put their plans in action, but so do a small group of Spiders who have become aware of the humans and have been working in secret for years to subvert their Focused as well. Together, the two sides successfully defeat the ruling class of the Emergents. The combined Emergent/Qeng Ho fleet now negotiates with the Spider civilization as a trading partner. Pham announces his plans to free all of the Focused in the entire Emergent civilization, and, if he survives that, to go to the Galactic Center to find the source of the OnOff star and the strange technology remnants that have clearly traveled with it. Elements Interstellar culture The book discusses some of the problems of trying to maintain an interstellar trading culture without access to superluminal travel or to superluminal communication. Time-measurement details provide an interesting concept in the book: the Qeng Ho measure time primarily in terms of seconds, since the notion of days, months, and years has no usefulness between various star-systems. The timekeeping system uses terms such as kiloseconds and megaseconds. The Qeng Ho's computer and timekeeping systems feature the advent of "programmer archaeologists": the Qeng Ho are packrats of computer programs and systems, retaining them over millennia, even as far back to the era of Unix programs (as implied by one passage mentioning that the fundamental time-keeping system is the Unix epoch): This massive accumulation of data implies that almost any useful program one could want already exists in the Qeng Ho fleet library, hence the need for computer archaeologists to dig up needed programs, work around their peculiarities and bugs, and assemble them into useful constructs. Time The Qeng Ho and other spacers in this series use kiloseconds (roughly 17 minutes), megaseconds (roughly 11.6 days), and gigaseconds (roughly 32 years) as units of time. Localizers With this work, Vinge introduces "localizers" to his set of science-fiction concepts. Localizers are tiny devices which can contain a simple processor, sensors, and short-range communications. Vinge explores how intelligent control can use mesh networking of these devices in ways quite different from those of traditional computer networks. Relation to A Fire Upon