some cool ideas in here. pretty good writing too. kept me engaged and interested throughout, and I learned a decent amount about some neat ideas and concepts. ( )

Deep Time: How Humanity Communicates Across Millennia is Gregory Benford's four-part meditation on lengthy periods that are essentially unimaginable for humans. But "meditation" may not be the right word. Benford has encountered deep time in his professional life as a scientist; each of the four parts of his book describes one of those encounters. The ideas in the book should probably induce a meditative consideration of our place in the universe, but Benford writes more journalistically than analytically, searchingly, or meditatively.

The first part is a relatively open-ended exploration of how to communicate danger to people in the far future who are unfortunate enough to find the places where we have buried radioactive materials. Benford writes about his time as one of several experts, appointed by the government, to work on this problem. It sounds like they enjoyed the opportunity to play with farfetched ideas. But since none of them had been implemented when Benford wrote his book (and to my knowledge remain unused), the main effect of this part is to tickle the mind of the reader with a perspective shift. "Deep time" not only starts to mean something, but inspires by suggesting, if only by implication, that humanity is on the cusp of an epic adventure across generations.

In part two, Benford heads for outer space. Once again, he finds himself on a panel of experts, this time trying to communicate not just across deep time, but with unknown extraterrestrials—through a disc that was intended to fly on the Cassini spacecraft. Like the first part, the subject here is evocative. There are problems at both ends of this communication: what should we say? and who are we saying it to, anyway? They're good questions, which deserve a book of their own. Unfortunately, the story bogs down in politics and begins to read like little more than a revenge against Carolyn Porco, whose antics (according to Benford) made all their efforts for naught.

Part three stays in deep time, but only marginally, and leaves behind the problem of communication. Worse, Benford appears to be continuing the sour-grapes theme that ruined part two. Now he is reviving a proposal he wrote in 1992, for the cryogenic preservation of life in the face of decreasing biodiversity. He twice observes that two major journals rejected his paper and admits that his views are unpopular and idiosyncratic. But that makes a bad impression in this book. It feels as though, needing more material on the "deep time" issue, he is just padding the book with a popularization of his old proposal. When he suggests that there is no reason to worry about actually retrieving information from the cryogenic storage system he proposes, since humans of the future will likely have better technology than we have, one is compelled to question the whole enterprise. If human development and progress will continue to hum along invariably, providing fantastic new technological tools for studying life, even as biodiversity plummets, then cryogenic storage of lifeforms, just for the sake of biodiversity itself, seems more than a little pointless. Using cryogenic storage as a method for "communication" across "deep time" suggests a societal discontinuity, caused in part by the ecological crisis of losing biodiversity; but if the method only works by assuming not just continuity, but technological progress, something does not add up.

The final part of the book is an improvement over the middle parts. Here Benford addresses climate change and suggests, though without using the word (since it probably hadn't been invented yet), that we have entered an anthropocene age. Our activities here will change the earth for a long, long time—maybe forever. Here the "communication" theme is only half-revived. Benford suggests that our most obvious "communication" to the future will be these permanent, or quasi-permanent changes, which are mostly inadvertent. He gets into geoengineering a little, which might suggest "communication" across "deep time," but not really; if we only use geoengineering to preserve the climate that we like, it seems unlikely that the "message" in the deep future will mean much. Moreover, if knowledge about the past is based on examining artifacts of change in the environment, it seems disingenuous to say that knowledge was the result of "communication," especially when the environmental artifacts are the result of our dunderheaded inadvertence. Even so, the chapter includes some interesting ideas about mitigating carbon emissions, few of which seem likely to be used, since human political systems have a hard time addressing anything but human conflicts.

Deep Time is not a bad book, but it could have been much better, mostly by leaving out the second half, removing the muckraking from part two, and greatly expanding the ideas explored in the first half. But since those other parts are there, one might improve the experience offered by this book by reading it in conjunction with Nicholas Basbanes' A Splendor of Letters: The Permanence of Books in an Impermanent World and Alan Weisman's The World Without Us. Basbanes focuses on the problem of communication over long time periods, while Weisman gets into the ways that humans have changed the earth. ( )

This unique book by physicist and science fiction author Gregory Benford examines human communication over long periods of time both retrospectively and prospectively. Benford begins by considering the longevity of structures and belief systems created by human beings over the millennia. The next sections of this book seek to apply any conclusions to real-life problems: marking nuclear waste, communicating with aliens, creating a library of genotypes and phenotypes of at-risk species, and preserving the planet.

The section I found most interesting was a government-sponsored project investigating how to minimize the risks of future generations unburying our nuclear waste over the next ten thousand years, raising the practical question of how to communicate over such a long period of time. Because we cannot expect current languages to continue to be understood, proposals include iconography and art, some of which is pictured (grainily) in the book.

I recommend this book to people interested in exploring how to think beyond our normal boundaries of time, space, and humanity, not that definitive answers are (or can be) provided. ( )