Extraterrestrial Intelligence: Communication

by William Sims Bainbridge

In The Encyclopedia of Language and Linguistics, edited by R. E. Asher (Oxford: Pergamon, 1994) Volume 3, pages 1200-1203.

Prospects for Success
Technical Methods
Understanding Extraterrestrial Communications


Epicurus, in the fourth century BC, believed that the universe contained other worlds like our own, and since his time there has been considerable debate whether extraterrestrial life exists and might communicate with us. In the last quarter of the twentieth century, an international social movement has emerged which advocates an attempt to achieve communication with extraterrestrial intelligence, CETI, and many of its most active members have been leading scientists. Modest efforts to detect radio signals from intelligent extraterrestrials have already been made, both under government aegis and privately funded, and the technical means for a more vigorous search have been developed. If a CETI project were successful, linguists would suddenly have one or more utterly alien languages to study, and some consideration of linguistic issues is a necessary preparation for it.

1. Prospects for Success

Although extrasolar planets have not been directly observed, and the indirect evidence for the existence of planet-like bodies in orbit around several nearer stars is only suggestive, the consensus among late twentieth-century astronomers holds that planets are probably quite common companions of stars like our sun. There are about 100,000,000,000 stars in our galaxy, and sober estimates place the number of planets at the same order of magnitude. How many harbor life is certainly not known, but the chemical processes that underlie biology are considered to be universal, and thus life of some complexity should be common enough that at least a few other civilizations have come into being roughly contemporaneously with that of Earth.

If, as some CETI proponents assert, there are thousands of civilizations in the galaxy, then ours must be among the youngest of them, and several writers have suggested that the older societies long since established interstellar communication networks. If so, achievement of CETI means membership in a 'cosmic club' exchanging information, art, and intellectual challenges drawn from myriads of sources. No society less technically advanced than our own could participate, and thus our status would be that of kindergarten students who had wandered into a university.

Frank Tipler has contended, however, that ours is the only intelligent, technological species. Stars comparable to our sun have existed long enough that, if intelligent species evolved frequently, several would be sufficiently old to have colonized the entire galaxy, including the Earth, yet this does not seem to have happened. Perhaps life and intelligence are far rarer than CETI advocates imagine. According to the 'anthropic principle,' advocated by Tipler, our situation is a privileged one, because only under conditions conducive to intelligent life will observers come into existence and wonder about their place in the universe. Thus, it is wrong to generalize from the existence of one inhabited planet to assume the existence of others. The chance of beings such as ourselves evolving may be so small that it has happened only once in the entire history of the universe, and Tipler has collaborated with John Barrow in a massive book documenting the improbable coincidences required to produce us (Barrow and Tipler 1986).

While granting the ubiquity of civilizations and the feasibility of CETI, Roger MacGowan and Frederick Ordway have argued that civilizations quickly evolve out of the biological stage and become entirely mechanistic, artificial intelligence replacing the natural intelligence that originally created the machines. If so, humans are doomed to extinction in a few hundred years, when computers outgrow the need for us, and CETI will eventually be accomplished not between humans and living beings near other stars, but between the descendants of current IBMs and the cybernetic entities built by other extinct intelligent species. Without going to this extreme, the possibility must be considered that extraterrestrial intelligence will be more similar to computers than to humans, and thus one should be ready to decipher messages composed in symbol systems more like data transmission protocols than natural languages.

2. Technical Methods

After a century of development, radio communication has reached a high level of effectiveness. The Voyager II spacecraft transmitted color pictures from Neptune over a distance of 4,000,000,000 kilometers using a transmitter with only 30 watts, a third the power of an ordinary light bulb. During the late 1960s, Carl Sagan estimated that the 300 meter Aricibo dish antenna in Puerto Rico could communicate with a similar system at a distance of 100 parsecs (about a million times the distance to Neptune). The technology to increase this figure by a factor of 100 exists in the early 1990s.

Most analyses have considered ordinary microwave radio signals to be more effective than other means, perhaps around a frequency of 2,000 mega-hertz where natural interference is at a minimum. Plaques bearing messages for extraterrestrials were placed on Pioneer and Voyager probes, which have left the sun's family of planets, but thousands of years will pass before any of them come near another star. Indeed, the vast distances across interstellar space will preclude ordinary conversations, even by radio. A question transmitted by Earth would take 4.4 years to reach the nearest star other than the sun, and the answer would be received after double that time. Across a distance of 100 parsecs, a single question and answer exchange would take 650 years.

Writers on the subject frequently suggest that advanced civilizations will establish long-term cultural enrichment projects, rather like combinations of Encyclopedia Britannica and the BBC World Service, beaming knowledge out into the void in hopes that other societies will receive the signals and be enlightened by them. However, optimistic statements about the ease of sending interstellar signals assume that the direction of the other party is known, so that all the power of the transmitter can be concentrated into a narrow beam. True broadcasting to the stars would be very power-consuming and thus expensive. Few societies may be willing to invest in it.

The glacial pace of conversations between stellar civilizations might demand more patience than even highly advanced societies possessed, thus preventing the development of a galactic communication network. But if even only one civilization were sufficiently stable and motivated, its broadcasts would eventually be picked up by others, which, when they got in touch with the broadcaster, would come to know of each other's existence.

An alternative is eavesdropping. With very sensitive receivers, it might be possible to pick up the ordinary radio traffic of an extraterrestrial civilization. However, radio broadcasting may be a brief stage in the development of electronic communications, and, in the early 1990s, most households in the USA are able to receive their television programs by cable. Once our entire planet is bound together with fiber optics, the only remaining strong radio signals may be high power radars, and they also may be turned off if our species outgrows the military conflicts that caused them to be built.

There has been much talk about SETI rather than CETI, replacing the C for 'communication with' by an S for 'search for.' The most modern radio equipment dedicated to this project is capable of observing thousands of frequencies simultaneously, but cannot resolve the signals, merely identifying the presence of a carrier wave. Once a signal is detected, far more sensitive equipment would be required to resolve it. Only then could a serious attempt be made to decipher the message.

3. Understanding Extraterrestrial Communications

The dead languages of the Earth presented great challenges to linguistics, from Egyptian hieroglyphics, through Linear B, to Mayan. Extraterrestrial languages would be even more difficult, because humans would not share the same environment or biological heritage as their creators. Many writers have suggested that the most effective Rosetta Stone would be mathematics and the physical sciences. Furthermore, an encyclopedia broadcasting society would plan for the decipherment of their signals, and include a primer, perhaps transmitted repeatedly on one wave-length while a great variety of more advanced messages went out on a different one. The primer could begin by counting out the first few integers: 1, 11, 111, 1111, 11111, and then transmitting the same numbers in the simplest positional number system, which is binary: 1, 10, 11, 100, 101. After that could come lessons in arithmetic, algebra, physics, and chemistry. While some branches of mathematics are undoubtedly culture-bound, number theory is likely to be universal, as is the periodic table of the elements and many other parts of the physical sciences.

Details of biology, psychology, and sociology might have to be communicated visually, and several writers suggested that the very first messages should be pictures. In 1962, Bernard Oliver demonstrated how a single picture could serve as the first message, consisting of 1,271 bits of data which can be arranged in a 31-pixel by 41-pixel rectangular image. However, when Frank Drake and Carl Sagan challenged their colleagues to decipher similar messages, success was quite mixed. To ensure that it would be understood, an interstellar encyclopedia would have to contain many redundancies, including repeated transmission of the same section and numerous internal consistency checks, restating the same material several different ways.

Attempts have been made to create rudimentary CETI languages, including Astroglossa, by Lancelot Hogben in 1952, and Lincos, by Hans Freudenthal in 1960. Lincos is rooted in mathematics and symbolic logic, augmented with a number of new symbols and three-letter words, often derived from Latin, like cur 'why' and enu 'counts' (from enumerat). Freudenthal shows how each word or symbol could be defined through a series of logical examples.

For example, the message on the right
shows how the concept of variable (X)
could be introduced, through a series of
equations featuring binary numbers.
100 +111 = 111 + 100
100 + 1 = 1 + 100
100+ 1101 = 1101 + 100
100 + 11 = 11 + 100
100 + X = X + 100

In discussing Lincos, Shklovskii and Sagan show how it might be possible to communicate the fact that person B is more intelligent than C. Assume the following has already been established: A, B. and C are persons; A --> B: means 'A says to B the following'; T means 'true' while F means 'false,' and .'. means 'therefore.' The concept >IQ 'more intelligent than' can be defined:

The concept >IQ
'more intelligent than'
can be defined as shown
in the message on the
A --> B: 15 X 15 = ?
B --> A: 15 X 15 = 220
A --> B: F
A --> C: 15 X 15 = ?
C --> A: 15 X 15 = 225
A --> C: T
.'. C >IQ B

The potential social consequences of CETI are incalculable, and questionnaire research by William Bainbridge (1991) found that people hold a bewildering range of expectations for it. Many hoped for vast troves of scientific information, technical advances including cures for deadly diseases, and even political advice to help achieve world peace. However, a barrage of scientific findings from a more advanced civilization might stifle humankind's own intellectual explorations. Medicine beneficial to alien physiologies might be useless to humans. If our world becomes desperate for solutions to mounting social problems, humanity might fall victim to insidious political propaganda from an interstellar dictatorship. Religious implications of CETI, such as those explored by C. S. Lewis in Out of the Silent Planet and its sequels, could be substantial and unpredictable. While alien art might be among the main benefits gained, it is a sad fact that even among the most highly educated very few people develop a taste for literature translated from exotic terrestrial languages.

The assumption that the extraterrestrials are more advanced than humans deserves to be questioned. Natural limits may exist to technological and scientific development, and a moral judgment is required before it can be called 'progress.' The evolution of wings was highly advantageous for birds, and yet even condors cannot fly to the moon. The evolution of language and the associated increase in intelligence have taken humankind far, but mathematics has already proven it possesses inherent limitations, and beyond a certain point greater knowledge may not provide greater power.

At the beginning of the twentieth century, three authors wrote about Martian civilizations, under the assumption that their planet was older than ours. H. G. Wells imagined a War of the Worlds, in which technically advanced Martians proved malevolent, at least from the human perspective. In Auf Zwei Planeten by Kurd Lasswitz, the Martians were both technically and morally superior. But in the novels of Edgar Rice Burroughs, technically advanced Martians were morally no better or worse than Earthlings. Just as the moral level of extraterrestrials cannot be predicted with confidence, one cannot be sure how their culture will compare with ours. Thus there is no reason to suppose that extraterrestrial languages will be more complex than those of our own planet.

Even before an extraterrestrial signal had been deciphered, humanity would have to deal with the discovery that we are not alone. But, in a sense that would take us back to the situation that existed before Europe launched its great exploration of the world, when each society knew that others existed beyond its borders, following different customs and speaking mysterious languages, and none understood fully the strange voices that surrounded them


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