Copyright © 1983, by David Brin. All rights reserved. No duplication or resale without permission.

The following article was first published in the 1980s in Analog Magazine as a popular adaptation of the much deeper and more scholarly 'classic' review of the field -- The Great Silence -- which appeared in the Quarterly Journal of Royal Astronomical Society, fall 1983, v.24, pp 283-309, which is also available on this site.

In the early 1960s, while the world was entranced by the spectacle of human beings hurled into "outer space" in rocket ships, a series of philosophical earthquakes shook the sedate field of astronomy. Just when the skies were beginning to seem known and familiar, all at once things changed. Stellar astronomers suddenly faced unsettling data from new classes of objects called "quasars" and "radio galaxies." There were disturbing theories about so-called "black holes." Even those who had long studied planets now found their comfortable domains invaded by geologists and meteorologists, who weren't at all shy about moving into the new territory.

It was no coincidence that all of this happened just as the Space Race was getting under way. New instruments and techniques often lead to upheavals in a science.

Still, the greatest intellectual challenge to the worldview of modern astronomers came in the early sixties, not because of new space probes, telescopes, and computers but because of an idea.

Starting in 1959, with a classic paper by Cocconi and Morrison, a series of articles and books were published with titles like Interstellar Communication, Habitable Planets for Man and, in 1966, a major work entitled Intelligent Life in the Universe by Iosef Shmuelovich Shklovskii and Carl Sagan. With these studies astronomers began to concern themselves with life itself.

The early sixties were pivotal for the field of "exobiology" (extraterrestrial biology) and especially the sub-branch that dealt with intelligent life, "xenology." For the first time it was legitimate for leading scientists to publicly consider the possibility of contact with intelligent species off of the planet Earth.

Of course a lot of thought had gone into the subject previously, on the pages of science fiction novels and magazines. Many of the private discussions between authors such as Sagan, radio astronomer Frank Drake, and Rand Corporation scientist Stephen Dole grew out of ideas germinated by the likes of Clarke, Asimov, and Clement during the thirties and forties. But prior to the publication of Intelligent Life in the Universe, the number of "respectable" papers on the subject printed in the West could be counted on one's fingers and toes.

In the Soviet Union extraterrestrial intelligence was not only considered possible but was required by Leninist dogma. (It was assumed dialectically impossible that any advanced intelligence could be anything but socialist, of course.) When scientist I. S. Shklovskii wrote "Universe, Life, Mind" in 1962, his thoughts were widely popularized, and extracts were reprinted in major Soviet scientific journals.

In the West it took more time for scientific speculation about the distribution of life in the cosmos to become acceptable. A tradition of skepticism and rigor kept Western science relatively safe from scientio-religions such as Lysenkoism, which caused so much harm in Russia. But the same attitudes made it hard for those interested in the possibility of alien life-forms to bring up the subject in scientific gatherings without being criticized for "playing with science fiction."

The older scientists who dished out the ridicule shouldn't be blamed too harshly. In squelching early discussions of exobiology, they may have been overreacting to the excesses of earlier enthusiasts, such as Percival Lowell, the astronomer who convinced millions that there were living Martians and "networks of canals" on the red planet.

But with the arrival of the space age, resistance to "science fictional" ideas was dealt a fatal blow. Those who had declared that "spaceships" belonged only in comic books were caught flat footed. A new generation of scientists brought exobiological speculation out of the fringes and onto the pages of respectable journals. These men and women, who had proven their scientific credentials with solid research, came from an age group that didn't consider "science fiction" a dirty word. Most of them had cut their teeth on the stuff.

The first time I witnessed the subject of extraterrestrial intelligence brought up at a scientific seminar was at a Wednesday Cal Tech colloquium in 1968. The speaker remarked on the remote possibility that pulsars might be beacons of an advanced civilization. They were, after all, several thousand times more regular in their repetitive "beepings" than any other astronomical radio source ever discovered.

The speaker was only partly serious, but sides were quickly taken, and it was soon very clear that most of those with tenure didn't like this kind of talk at all.

Attitudes were changing very rapidly during those years. A few years later some of those who were the angriest in 1968 applauded the loudest when Carl Sagan unveiled the gold plaque that was to be placed upon Pioneer 10, the first human artifact to be launched on a trajectory out of the solar system.

Today that plaque is famous. It, and those that followed on Pioneer 11 and the Voyagers, depict the nude figures of a woman and a man, an arm raised in greeting, a schematic of the planets of our system, and a rayed pattern of lines and binary dots representing the most prominent pulsars detectable from Earth. The pulsar map should enable any distant beings who recover the spacecraft to trace its point of origin within a light-year in space, and its launch date to within six months.

Shortly thereafter respectable scientists were discussing not whether extraterrestrial intelligences exist but how to go about listening for signals from our nearest neighbors! Small (very small) amounts of public money were allocated to adapting radio telescopes for the search.

If the first revolution in the nascent field of xenology came on the pages of science fiction pulps of the thirties and forties, the Second Xenological Revolution took place in the sixties, when scientists in large numbers began asking, "Where are they?"

Anyone interested in the possibilities of life outside the Earth should certainly read Intelligent Life in the Universe. Although some of its science is dated, it remains the classic in the field. Still, to a veteran reader of SF, Intelligent Life may seem overly tame and conservative. For instance, the authors barely mentioned the possibility of travel between the stars. To investigators of that time, it seemed pointless to discuss interstellar colonization.

Science fiction has long used, as furniture, ships that bypass relativity. But to early xenologists it was dangerous enough talking about alien life-forms, without risking one's scientific reputation talking about "hyperspace warpdrive" and the like. Shortcuts may lend SF a lot of pizzazz and spawn stories about galactic empires, but Einstein's speed limit dominates serious talk about life in the universe.

The gulfs separating the stars are vast. And during the sixties it seemed unlikely that even the modest velocities allowed under Einstein's edicts could ever be reached economically.

Thus the first era of modern scientific xenology (from 1959 to about 1972) dealt with the possibility of intelligent life springing up in isolation (here and there on fertile planets scattered across the sky), islands of intelligence separated from one another by vast distances and for all time.

Next... three major discoveries change the equation.