While people have speculated for many centuries about intelligent life elsewhere in the universe, the actual search for it is a quest of our time. It now seems reasonable to expect that scientific developments in the coming decades will yield the answers we seek.
The search began in 1960 with project OZMA, when Frank Drake, now at Cornell University, scanned two nearby stars -- epsilon Eridani and tau Ceti -- for radio messages.
Since then, several other searches have been undertaken in the United States, the Soviet Union, and Canada, including Project OZMA II, in which Pat Palmer of the University of Chicago and Ben Zuckerman of the University of Maryland looked at 600 stars. None of these searches produced positive results, and a feeling began to grow that we might be all alone in our galaxy. This led to a hiatus of several years. Some new developments last year, however, indicate a renewed interest in this area among astronomers, with exciting prospects for the future.
* The International Astronomical Union, the supreme world body in astronomy, held its triennial general assembly in August in Montreal, and for the first time it included a joint session on "Strategies for the Search for Life in the Universe." This one-day session attracted great interest, and when Dr. Drake and I summarized the results for the general membership the next evening, the large auditorium of the University of Montreal was packed with more than 1,000 astronomers from all around the world.
* In November another very interesting conference took place, at the University of Maryland. The topic of this two-day meeting was "Where Are They? A Symposium on the Implications of Our Failure to Observe Extraterrestrials." It was attended by many of the leading scientists in this field.
* NASA has formed a prestigious committee, including several Nobel Prize winners, to study the problem of SETI -- the search for extraterrestrial intelligence.
* A national committee trying to formulate the goals of astronomy for the next decade is seriously considering including SETI.
It is of interest to mention here some of the highlights from the two conferences, because they give the flavor of the views prevailing in the scientific community on this subject.
The Montreal meeting focused on the following four topics:
1. Alternative views on the number of technological civilizations in our galaxy.
2. Strategies for SETI through radio waves.
3. Search for early forms of life in our solar system and in other planetary systems.
4. Different manifestations of advanced cosmic civilizations.
In No. 4 the possibilities for interstellar travel were discussed, including Project Daedalus, the spaceship design study of the British Interplanetary Society. This spaceship, its designers claim, could travel to other stars using nuclear bombs for propulsion. At this stage, such a trip would need all the nuclear bombs available on Earth, but then, who could possibly think of a better use for our nuclear stockpiles?
In 3 it was exciting to hear of new developments in our efforts to detect planets among nearby stars. This is a very difficult task, which has not yet been fully accomplished. The basic problem is that the dim light from these planets is totally lost next to the bright glow of their suns. It is like trying to see a firefly sitting at the edge of a powerful searchlight. In 2, all the previous radio searches in the US, Canada, and the Soviet Union were reviewed and various large- and small-scale projects for the future were discussed.
The exchanges in No. 1 on how many advanced civilizations might be present in our galaxy proved to be lively. A growing number of scientists, including me, have in recent years supported the view that technological societies, such as ours, will inevitably become engaged in space exploration and colonization that will ultimately populate the whole galaxy.
These ideas are based on the observation that terrestrial life, from algae to humans, has a natural tendency to expand like gas to occupy all available space. With the development of technology, humanity has managed to adapt quickly to every conceivable environment and, after conquering land, sea, and air, is now ready to venture into outer space, the largest expanse of all.
The feasibility of interstellar travel, and hence of galactic colonization, has been greatly enhanced by the space colonies proposed by Gerard O'Neill of Princeton University. These colonies, which may very well become commonplace in the next century, would obtain their energy either from the sun or from thermonuclear fusion. They would get raw materials initially from the moon and later from the asteroids and the moons of Mars and Jupiter. As a result, they would in time become independent of Earth.
Such colonies could embark on long interstellar trips that might last for several centuries. It would make no difference to these people whether their colony were orbiting the sun or were on its way to another star. Once the colonization of the galaxy were thus initiated, with speeds of 1 to 3 percent of the speed of light, the colonization wave should sweep through the whole galaxy in probably less than 10 million years.
The question now posed to us is: Has our galaxy already been colonized? If one is tempted to think that it must have been, then the next question is: Where are the colonists? -- the topic of the University of Maryland symposium organized by Michael Hart of Trinity University, Ben Zuckerman, and me.
The literature, of course, is full of stories about ancient astronauts and UFO episodes, but there is no convincing scientific evidence for any of these stories. For this reason Michael Hart has adopted the position that they are nowhere to be found, and therefore in all probability we must be all alone.
In all fairness, it must be stated that the colonization argument is not accepted by all. For example, two of the leading scientists in this field, Dr. Drake and Carl Sagan, also of Cornell, reject it. Dr. Sagan estimates it would take 10 billion years, not 10 million. Dr. Drake reckons it would simply be too uneconomical.
My own view is that the possibility that our galaxy has already been fully colonized cannot be dismissed until we have carefully searched throughout our own solar system, and in particular in the asteroid belt, for space colonies.
Such a search inside our solar system is already within the capabilities of our technology, in terms of both astronomical observations from Earth and direct spacecraft missions. It is quite possible, therefore, that by the turn of the century we will know whether our solar system has been colonized or not. We will also have searched our nearby stars for planets as well as for signs of any technological activities, including radio, infrared, and optical signals, all of which are being considered by the SETI subcommittee as possible goals for the ' 80s.
If all these searches turn out to be negative, we ought to consider seriously the possibility that we might really be one of the very few, if not the only, advanced civilization in our galaxy. After all, if the ultimate goal of creation is to populate the entire galaxy with intelligent life, this goal can be achieved a thousand times faster by starting from a single star and colonizing all the others, rather than by waiting for intelligent life to evolve independently in each star.
In conclusion, it seems reasonable to expect that in the coming decades either we will discover that our galaxy is teeming with intelligent life and we will be invited to join an already blooming galactic society, or we will have to accept the idea that we are alone and it is up to us to infuse life into the entire galaxy. Standing at the threshold of such profound cosmic knowledge makes our times a unique and most exciting period in the history of man.