A 'Post-It Note' for the next 10,000 years

DEEP TIME: HOW HUMANITY COMMUNICATES ACROSS MILLENNIA By Gregory Benford Bard 225 pp., $20

Last week's list taped on the fridge is confusing. Old notes from college are baffling. Chaucer hardly seems like English. And what's the point of those statues on Easter Island? If past forms of communication are any guide, it won't be easy to leave a message for the next few thousand years.

Gregory Benford, a physicist at the University of California, is also a renowned science-fiction author. In this engaging and readable book, his first work of popular nonfiction, Benford recounts four personal experiences with sending messages to future generations.

"Ten Thousand Years of Solitude" is an unnerving account of his service on an advisory panel to the Department of Energy regarding the siting of the Waste Isolation Pilot Plant, outside Carlsbad, N.M. The plan is to store up to 800,000 barrels of radioactive waste in salt caves a half-mile below the desert.

Congress specified that the site should remain undisturbed for the next 10,000 years, until the level of radiation decays to undetectable levels.

The problem is how to identify the site as dangerous to future societies for a period longer than the historic record of humanity. The implication is clear that the hazards of our nuclear technology are likely to outlive our civilization by a considerable margin.

The second essay, "Vaults in Vacuum," takes an even longer view. NASA's Cassini mission is planned to arrive at the planet Saturn in 2004. Shortly afterward, the Huygens lander will separate and descend to the surface of the moon Titan, where it will likely sink beneath the frozen methane oceans of the moon.

Benford and several colleagues suggested to the spacecraft's designers that a small diamond disk be attached, bearing a message to any future discoverers.

The problem of designing a message that would communicate with alien intelligences, or our own descendants in the far future, provides an interesting take on the assumptions we make about ourselves.

In an ironic debacle, infighting among the designers of the message resulted in NASA deciding to drop the idea. Instead, the spacecraft was sent off with a plaque containing the autographs of 600,000 random signatories - the electronic equivalent of "Kilroy was here."

The most important message to our descendants is our care for what we have received from the past. A best guess at the historical rate of extinctions is about one species a decade; the current rate exceeds 5,000 species a year, a loss unrivaled in the historic record.

"Library of Life" is Benford's plan for preserving the diversity of life by freezing samples of animal and plant life, storing them in giant flasks of liquid nitrogen.

"The coming wave of extinctions may be our most lasting, important heritage," he writes, "far surpassing our gilded monuments or abstract plaques on spacecraft, for the vast loss will be felt throughout humanity in a world truncated and diminished, perhaps irretrievably."

Finally, in "Stewards of the Earth," Benford describes a plan to reduce the accumulation of greenhouse gases by adding droplets of sulfuric acid to the atmosphere over oceans. As a physicist, it is not surprising that he is willing to consider technological fixes to social problems.

In the final analysis, the importance of this book is that Benford is not an alarmist. He genuinely believes science can help find solutions. At the same time, the magnitude of these problems can seem overwhelming. It is critical to believe that the future can still be saved, but only if we do not give up on it.

*Frederick Pratter is a freelance writer in Missoula, Mont.