"Deep time" was a termed coined by John McPhee in his book Basin and Range and was used to describe geological time scales. Gregory Benford uses it to describe time scales much longer than a human lifespan. Benford's emphasis is on communication between humans separated by hundreds, thousands, and potentially millions of years. Most of the books reviewed here have been related to the search for extraterrestrial intelligence (SETI) or the study of life in the Universe. Why consider this book? One reason for reviewing this book is that any transmissions from ETs may come to us from deep time. Another consideration is that, if we cannot decode the messages sent down to us by our deep ancestors or send down messages to our deep descendants, what hope to we have of decoding messages from another species entirely?
Deep Time consists of an Introduction and four nearly independent parts. Although this reviewer read the book in a linear fashion, he suspects that one could read the Introduction and then read the four parts in any order. For that reason this review will not proceed in a linear fashion through the book.
In the Introduction Benford both sets the stage of deep time and illustrates how difficult the problem of communicating through it is. Consider the simple act of making a time capsule (or as they were known initially "time bomb" :). First, what does one use to fill a time capsule? Will our grandchildren (or their grandchildren) be interested in a Wonderbra or a "Not Too Young to Polka" videocassette (both of which have been included in at least one time capsule)? If so, it will be presumably only because they view these articles as interesting relics of life for Everyman or Everywoman in the Twentieth Century. Second, having decided what to store, how is it stored safely away from the elements yet not forgotten? Benford cites a number of examples of time capsules prepared, buried, and then quickly forgotten---and then there are those capsules whose contents are stolen even before they are buried. Sending a message through time is difficult.
Part III of Deep Time considers the shortest expanse of time through which Benford suggests sending a message---roughly 100 years. Benford motivates Part III by likening the reader to a scribe in the Library of Alexandria as it began to burn. What to save? Benford's proposal---which is essentially what Part III is---concerns not books but genetic codes. He argues that the human-induced extinction event underway constitutes one, possibly unintentional, deep-time message. He proposes that we should attempt to supplement our first deep-time message with a second one, a DNA library of species, so as to preserve a small record of the Earth's disappearing biodiversity. He acknowledges that this may be viewed as a drastic step, hence his comparison to a scribe attempting to save manuscripts from the Library of Alexandria while it is burning. His hope is that, at best, improvements in biotechnology will enable the various species to be "resurrected" from the samples preserved; at worst, our descendants will at least have some specimens for their museums that would illustrate the former biodiversity of the planet. Clearly Benford has put a lot of thought into his proposal; he includes even an estimate of the cost of how little it would cost to deep-freeze specimens for a century. Of course having written the Introduction, Benford must also be sober as to the possibilities that this biological time capsule (or capsules) would not survive a century.
Neither Benford not the reviewer are experts in biotechnology, so the reviewer is unable to say much about the technical details of Benford's proposal. In fairness, the reviewer expects that Benford does not know if what he proposes is possible but probably would argue that it is better than doing nothing. However, the reviewer is mindful of one of Stephen Jay Gould's criticisms of the movie "Jurassic Park": A animal is more than its DNA. Even with a large DNA library of extinct species (i.e., deep-frozen specimens), will the biotechnicians of the Twenty-Second Century be capable of restoring the species? If they are, of course, the DNA library should be named Benford's Ark.
Part IV contains a deep-time message to an uncertain time in the future, but probably between a century and a millennium (though potentially much longer): In all likelihood, humans are at least partially responsible for altering the global climate. Benford is not unique in pointing out that we humans are conducting a global experiment (though he was writing at a time when the evidence was considerably less abundant than it is today). He is forceful and persuasive in arguing, however, that now is the time to begin conducting experiments that may allow us to slow or mitigate the effects of global climate change. This reviewer had been unpersuaded by arguments of others to conduct these experiments. Perhaps because Benford is a physicist, he described various mitigation schemes as experiments themselves, this reviewer is far more willing to consider them. Previously, this reviewer had considered such mitigation schemes as too risky to implement. If they are considered as experiments themselves, though, it is worth investigating them though. If that was Benford's purpose in writing Part IV, then he has convinced at least one reader.
Part I is perhaps the most fun in the entire book. Benford was part of a panel assembled to recommend ways to keep the Waste Isolation Pilot Project from causing any fatalities. The WIPP is a project testing how to store radiative waste. One of the mandates placed on it by the US Congress was that it should cause no fatalities from the radioactive materials stored within it for as long as those materials are potentially hazardous. In practice this means that once the WIPP is filled and sealed, there must be no unauthorized or unintentional intrusion into it for 10,000 years. In order to place this 10-millennia duration in context, remember that the US Congress itself is only 0.2 millennia old. Ten thousand years ago humanity consisted of little more than small tribes of hunters and gathers. Predicting human technological capabilities over the next ten millennia is impossible, and the US Congressional mandate is unlikely to be met. That did not prevent Benford and his fellow panel members from considering possible ways in which the WIPP might be violated and ways to try to prevent this from happening. It is considering these various possibilities that make this portion of the book so much fun. One of the reviewers few criticisms of this book is that Part I perhaps should been placed later in the book. the other three parts of the book consider fairly sober subjects. A bit of lighter reading in their midst could have been welcome.
Part II deals with the transmission of messages either to our distant ancestors or to entirely other species in the deep future, and specifically with the case of putting plaques on spacecraft. The most famous of these are the plaques on the Pioneer spacecrafts and the Voyager interstellar record. Benford reviewer these briefly but his focus is on the Cassini-Huygens mission. This mission is currently in its cruise phase to Saturn, having passed by Jupiter in 2000 December as part of a gravity assist maneuver. At Saturn, the Huygens probe will detach from the Cassini spacecraft and drop into the atmosphere of Saturn's moon Titan. (Titan is of such interest because it is the only moon in the solar system with a thick atmosphere, and it may represent an analog of the early Earth.)
On Cassini there is a small bare spot. Benford proposed that a small diamond disk be attached to Cassini carrying information about the species that designed it in case that Cassini is ever found, either by our descendants or by visitors to our solar system. (Once this proposal was made, some thought was given to including such a marker on Huygens as well.) Benford describes both what he envisioned attaching to Cassini and, just as importantly, why. Benford is understanding, if highly critical, of recent efforts to put lists of names on spacecraft. Thus he describes at length, perhaps excessive length, why various choices were made; perhaps future editions of the book need not contain such detailed expositions of various choices, for example of the Golden Mean. Benford worked closely with the noted artist Jon Lomberg and Carolyn Porco, a principal investigator on one of Cassini's instruments on a memorial disk. Ultimately, however, the spacecraft was launched without the Lomberg-Benford disk. This is an interesting, if depressing, reminder that scientists can have human faults. One might hope nonetheless that future spacecraft will contain possibly decipherable messages rather than little more than legalized graffiti.
In summary while Deep Time contains a small number of minor weaknesses, it is overall a provocative, fascinating book. It is recommended highly for anyone interested in the general problem of communication between intelligent species.
(Postscript: One of Benford's comments about deep-time messages is how flimsy most of our media are. Rare is the piece of paper, eight-track cassette, or CD-ROM that survives for more than a few tens of years. This review is being written in perhaps the most flimsy medium available. After reading Deep Time, I read How the Irish Saved Civilization by Thomas Cahill. In it Cahill describes how Irish monks helped preserve Western civilization by copying ancient manuscripts. Regarding his art, though, one monk wrote "Sad it is, little parti-colored white book, for a day will surely come when someone will say over your page: 'The hand that wrote this is no more.'" This reviewer wonders if anyone will have cause to wonder the same regarding his works.)