Deep Time: How Humanity Communicates Across Millennia

  • Gregory Benford
Avon: 1999.225pp $20
From there to here: our desire to leave a marker for the future existed back in ancient Egypt. Credit: CORBIS/ ROGER RESSMEYER

To transfer information at some point in time to a period that could be later by millennia is not an easy proposition, but such transfers have a long history. Think of the pyramids and the various structures that are known as the Seven Wonders of the World. Apart from the Cheops pyramid in Giza, Egypt, most did not survive as long as their creators had hoped. But the point is that the ancient structures that did survive serve a useful purpose: they furnish us with a guide to the sort of life lived many centuries ago. And, of course, they gave reigning emperors some assurance that they would be comfortable in their afterlife. The cave paintings in the Lascaux cave, on the other hand, may represent art for arts sake, or may also have had a magical purpose. We just do not know.

In the present era, it is not the wish for comfort in the hereafter, or the desire to exercise a religious impulse, that causes us to signal to the future. Our motivation is scientific fervour. The 1977 Voyager missions to the outer planets, for example, contained a phonograph record of the shouts and songs of humanity (plus instructions on how to use it). This reminds one of the 1971 Pioneer mission, which carried a plaque showing two nude humans greeting the infinite with a wave. Far more complicated ideas had also been considered by the scientists of the various space agencies. For example, the finders of a payload would have been able to date a launch to within a million years or so had it provided a current view of the Andromeda galaxy. The reason? The galaxies rotate, though rather slowly, and the observed rotation would have revealed roughly how much time had passed.

Gregory Benford notes that the 1997 Pathfinder spacecraft deposited the names of members of the Planetary Society on Mars — probably not essential information for future cosmic travellers. Indeed, as Benford says, “ as a projection of pure vanity, it resembles the International Star Registry, which sells people certificates stating what stars have been named after them”.

“Deep time”, a period of the order of a millennium or so introduced by the author, is also relevant for those who wish to save our biological diversity. Benford relates how he wrote a paper in 1992 in which he proposed to take representatives of all threatened species and suspend them in liquid nitrogen for the indefinite future. This paper was rejected by Science and Nature, but eventually caused considerable discussion after its publication in the Proceedings of the National Academy of Sciences. The idea is to go beyond “the piecemeal strategies of seed banks, of germ plasma”, to make up an, admittedly incomplete, collection of threatened species. There is a full discussion of this suggestion in a chapter called “The library of life”. The problem of showing precisely where radioactive waste is buried is discussed in a chapter entitled “Ten thousand years of solitude”. The markers should presumably survive thousands of years, but there is a case also, as pointed out by the author, for not marking them at all, so as to prevent future theft.

Deep Time offers an unusual combination of ideas that give food for thought, even though some seem rather far-fetched. In a future edition, Benford might improve the organization of the text, for example by giving a table of dates and other details of the satellite launchings that are discussed. Also, a list of markers — ‘headstones’ — actually used to indicate burial sites of radioactive waste would help. Further, the authors colleague Frank Drake, who is mentioned repeatedly, is presumably connected with the well-known equation that gives a rough estimate of the number of advanced civilizations in a galaxy. This might be pointed out.

Benford is a professor of physics at the University of California at Irvine and helped to design the message that flew on the 1997 Cassini mission to Saturn. He has also worked on the long-term marking of US nuclear-waste sites. So the book is worth reading for its insiders account of the design of markers that tell the story of humanity, and of the Earth, for the benefit of future cosmic travellers. It is also useful for the details it gives of the plans to keep alive our biodiversity, and for its discussion of the storage of nuclear waste.