For the last million years or so, mankind's principal diplomatic interest has been to handle social intercourse on his own planet. Interaction with other societies, from other worlds, was the province of science fiction. That may soon change. Modern science and technology suggest that a transmutation of past fiction to present reality could be imminent.
If so, the dynamics of interaction will surely be far different than the alien encounters routinely portrayed in the cinema and on television. The ideas developed more than a century ago by European novelists such as Jules Verne and H. G. Wells, while imaginative, were not prescient. The aliens won't come here, and we won't go there. Our interaction will be a distant one, conducted by the electronic equivalent of very slow diplomatic pouch.
But while it seems unlikely that any face-to-face meeting with extraterrestrial beings will ever transpire, it is now within our technical capability to detect the signals beamed by advanced societies from their home planets. In the coming century it is both thinkable Ñ and some would say likely -- that we will establish at least one-way communication with a sentient, non-human civilization. This is because of a small-scale experiment known as SETI, the search for extraterrestrial intelligence. By taking account of the methods used for such searches, it's possible to speculate on the likely parameters of a SETI contact. This might help us better envision how we would deal with an event that would mark a major discontinuity in societal evolution.
The Martian Chronicles
Seventy-seven years ago, the first serious attempt to contact our cosmic brethren was made by a few imaginative Americans using the new technology of radio. In 1924, Mars was in opposition, not in a strategic sense, but in an astronomical one. It was opposite to the sun in the sky, thus placing the Red Planet substantially closer to Earth than is usually the case: approximately 45 million miles away. It was a fortuitous time to get in touch.
There was also motivation to try. Since the end of the 18th century, Mars had beguiled astronomers with its clear atmosphere, dark markings, and icy polar caps. It was a world thought to be not only habitable, but inhabited. If so, then radio waves broadcast by sophisticated Martians could be traversing the empty spaces of the solar system and, if detected, would bring us proof of their existence and information regarding their situation. An attempt was made with the receivers of the time to tune in on these putative Martian transmissions. Even William Friedman, America's premier cryptographer (he would later break the Japanese Purple Code), was on standby alert, in case the messages from Mars proved enigmatic.
As it turned out, Friedman's expertise wasn't needed. The Red Planet passed through opposition in radio silence. We now know that if any life exists on Mars today, it is undoubtedly of a very simple sort -- perhaps microbes dwelling in wet rock hundreds of feet below the dusty, sterile surface. While it would be very significant to find such simple biology, the repercussions of this type of discovery would be mostly felt in the world of science.
Not so in the case of SETI, the search for extraterrestrial intelligence. If the efforts to detect signals from sentient beings bear fruit, there will be immediate and profound social consequences. Finding a sophisticated society, even at 1,000 light-years' distance (100 million times as far as Mars), would be more than an interesting science story. It would force us to confront the fact that we are only one of many technological civilizations in our galaxy (and probably among the least advanced). It would also compel us to decide whether to attempt communication with these alien beings, and if so, to consider what we would say. (See the accompanying article by Michael Michaud for an examination of that question.)
Today's SETI experiments bear only a superficial resemblance to the 1924 effort to eavesdrop on Martian radio broadcasts. Not only is our communication technology far more sophisticated now, but we also have a better idea where intelligent beings might be located. No contemporary scientist seriously expects that any of our solar system's other planets or moons are home to thinking creatures. Instead, SETI astronomers look to more distant realms.
Since 1995, when the first planet outside our solar system was discovered, astronomers have found that a significant number of the hundreds of stars they've studied in detail have planetary companions. Indeed, recent discoveries of planets around other stars suggest that at least 10 billion alien worlds populate the star fields of our galaxy, the Milky Way. (For those who find these statistics insufficiently encouraging, note that there are roughly 100 billion other galaxies, each with a similar number of planets.) In addition, there is growing suspicion, based on studies of the solar system, that biology may also be widespread throughout the universe.
These data reinforce the presumption that other worlds, with other beings, might be commonplace. In popular fiction, such worlds are only a rocket ride away. In this view, advanced technology -- either ours or theirs -- will permit spacecraft to beat their way from star to star. Even if our engineers aren't quite up to it, advanced aliens will surely have mastered space travel and might be headed our way. Indeed, according to polls taken since the 1960s (e.g., the CNN/TIME poll of June 1997: http://www.cnn.com/US/9706/15/ufo.poll/), a majority of Americans believes that extraterrestrials are already in our neighborhood (arriving in spaceships known popularly as UFOs: unidentified flying objects). A similar percentage is convinced that the federal government is keeping these interstellar social calls under wraps. When those who believe in visiting spacecraft are asked why Washington would suppress the most interesting science story of all time, the usual response is that "the public couldn't handle the news." But that explanation is clearly deflated by the simple fact that roughly half the public already believes the extraterrestrials are here, yet there seems to be no panic in the streets.
Moreover, the presence of aliens on (or slightly above) Earth is largely disputed by the scientific community on two grounds: (1) the lack of convincing, physical evidence, and (2) the enormous difficulty of effecting interstellar travel. The energy required to send a 400-ton (the same weight as a 747 jumbo jet) spacecraft to the stars at 90 percent of light-speed is sufficient to power the city of Washington, D.C. for three million years. Irrespective of the technology used to propel a spacecraft, this prodigious energy cost argues against routine reconnaissance missions to other solar systems. Scientists also point out that even at these terrific speeds, it still takes many years to reach the stars.
Interstellar travel may therefore remain a fictional enterprise. Nonetheless, we have already noted that contemporary astronomy hints at a plethora of other worlds, spinning silently and unseen through the galaxy. Some of these could be home to sentient beings. To verify this hypothesis, SETI researchers attempt to find the aliens by deploying multi-million channel receivers attached to massively large radio antennas. Their goal is to detect the radio or light emissions advanced societies would produce.
While some SETI efforts scan large tracts of sky, the most sensitive searches target individual, nearby star systems. The premier example of this type of experiment is Project Phoenix, run by the SETI Institute, in Mountain View, Calif. In the next two decades, this experiment will be greatly expanded, thanks to the inexorable march of computer technology. The number of scrutinized stellar targets will grow from approximately 1,000 to several million. It is this predictable improvement that has largely motivated the consideration of what to do if we detect E.T., for the chance of finding a signal is increasing rapidly.
Message In A Bottle
While the general population would be vastly interested to learn of a transmission from another world, their curiosity would center on two obvious questions: are we in danger, and what are the aliens saying?
The first concern is easily dismissed: We would not be in any danger. Since SETI is a passive endeavor -- scientists are only listening -- the fact of a detection would only be known by us, not by them.
As for the second query, the popular impression, harkening back to the 1924 Mars episode, is that the aliens will employ some sort of code -- perhaps based in mathematics -- to school us in the fundamentals of trans-species communication. If we should master this introductory material, according to this scenario, they may then choose to enlighten us with the equivalent of the Encyclopedia Galactica. And since it is a statistical near-certainty that any civilization we uncover will be thousands of years or more beyond our technical level, they could teach us much.
This optimistic prediction is probably unrealistic. Today's SETI receivers look for narrow-band transmissions, which on the basis of simple engineering considerations would be the most logical for establishing contact: they would make good "hailing signals." However, these types of signals can carry only limited amounts of data. They are like excruciatingly slow modems, or, to use an older analogy, they would produce a signal akin to a message in a bottle. There would be precious few bits of information from whatever distant society had produced the signal.
Nonetheless, finding the bottle is only the beginning. A barrel full of books might be in the offing, if we only continue our search. Presumably, any extraterrestrials that would bother to establish an interstellar transmitting facility would also wish to load their broadcasts with a worthwhile message. To hunt for more information once a signal has been found, SETI scientists would need to build far larger antennas: perhaps many thousands of times larger than what are used now. Only these much more massive instruments would be able to find the high-speed data that we presume an alien transmitter would be sending.
That is a project that might take years or even decades. In the interim, we would need to be satisfied with the very basic sorts of information that could be deduced from a slowly varying, narrow-band transmission. This would give us the length of the day and year on the aliens' planet which, combined with information about their star (obtained by standard telescopic techniques) would tell us something about the average temperature of their world. These are the simple parameters that could be readily deduced from the note within the bottle. They are entirely of a technical nature, of course. Nonetheless, there would undoubtedly be enormous public reaction to even this simple discovery. We would suddenly be treated to the disarming news that the currently popular portrait of an inhabited universe is more than mere entertainment at the cinema or on the television. The testimonies of the UFO believers and those who claim to have been abducted by gray beings from other worlds would suddenly seem quaintly irrelevant. A signal found by SETI would be more than a breathlessly told story: it would be hard evidence easily verified by anyone with a suitable antenna and receiver -- evidence that is impossible to hide.
We Are Not Alone
A discovery that we are neither alone in the cosmos, nor the galaxy's most sophisticated thinkers, has often been likened to the Copernican revolution. The practical consequences may be minimal, but the philosophical implications are profound. Yet even this formidable event would pale in comparison to finding and understanding a message. The consequences of the latter would so affect humanity as to become a true discontinuity in our cultural evolution.
As alluded to earlier, the statistics of the SETI enterprise virtually guarantee that any transmission we receive will be from a long-lived, technologically sophisticated civilization. The reason for this is simple: only long-lived signals have much chance of being detected. Thus, if a signal is found, then the society at the transmitting end is very likely to be thousands or more years beyond our technical level by now. Accordingly, if we can understand their message, we might be enlightened by the last word on physics, astronomy, chemistry, and (insofar as it applies) cosmic biology.
On the face of it, this sounds as if it might be a good deal, somewhat akin to learning to read and gaining access to the contents of the metropolitan library. Yet history suggests that a sudden flood of advanced knowledge is usually disruptive. For example, the South Pacific island societies James Cook visited in the 18th century saw their cultural heritage evaporate when exposed to the heat of European technology. Similarly, humankind might lose confidence and its sense of purpose if suddenly tutored by enormously more sophisticated beings.
This is a discomfiting scenario that I personally find unlikely. Advanced extraterrestrials would probably have no more interest in schooling us than we have in schooling pigeons or pandas. If Australopithecus were somehow available to us, would we make major efforts to educate him in the ways of the early 21st century?
If we find a message, it's quite possible that it will be nothing more than a meaningless bit stream to us for centuries, or possibly forever. It would be like discovering Egyptian hieroglyphics, but not the Rosetta Stone. We might never comprehend what the aliens are broadcasting. But even if we fail to understand the transmission, the mere fact of its existence will have taught us something deeply important. We will know that the seeming miracle of biology and evolution that has produced thinking beings on this planet is no more than a natural and non-unique process. This will, at the very least, place our human diplomacies in a larger, and humbling, context.
Dr. Seth Shostak is an astronomer with the SETI Institute in Mountain View, Calif.