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How Can We Achieve Contact?
by Allen Tough, Ph.D., University of Toronto
email tough @


The scientific search for extraterrestrial intelligence could add several powerful new search strategies, instead of limiting itself to just one or two.

Extraordinarily advanced technology

Think for a moment about the changes that have occurred in our science and engineering over the past 100 years, since approximately the year 1900.

Now think for a moment about the changes that will likely occur in the next 100 years of our science and technology.

Now multiply that amount of change by 100 in order to get some sense of the advanced technology that SETI scientists are trying to detect.

SETI, of course, is the search for extraterrestrial intelligence. To be more precise, in its present form SETI is the scientific effort to detect extraterrestrial technology.

SETI scientists, therefore, must give some thought to just what that technology might be like. What sort of technology are we trying to detect? Their technology is likely thousands of years beyond ours. One astronomer even defends 2.7 billion years as the average age difference. [Reference 1]

Any other civilizations in our galaxy are probably much older than human civilization. Two factors support this assumption. First, the vast majority of stars in our galaxy are much older than our sun, many of them millions of years older. It follows, then, that any civilizations on planets revolving around those stars likely arose much earlier than our own civilization did. Second, it seems quite possible that some civilizations survive for a million years or even longer. If the civilizations in our galaxy range in age from a few thousand years up to a million years old, then we are one of the youngest: by most definitions, human civilization is not much more than 10,000 years old.

Because other civilizations in our galaxy are thousands of years older than human civilization, they have presumably developed science and technology that are far beyond our present level. Some civilizations may fail to survive once they discover nuclear weapons or other means of extinction, but surely others learn to cope successfully with this problem and then survive for a very long time. Some of them may have technology that is 100,000 years or even millions of years more advanced than we are.

A list of their technology might strike us as unbelievable when we first read it. Would a human being 10,000 years ago, though, have reacted any differently to a list of our present capacities? Electricity, airplanes, astronauts, moon-walks, telescopes, selective breeding, television, microbes, hospitals, DNA, computers, universities, skyscrapers, nuclear weapons, and many other aspects of today's world would have been dismissed 10,000 years ago as ridiculous or impossible.

That was the time when the Ice Age ended, humanity's main crops became domesticated, and the world's first town arose. Pigs, cattle, and horses had not yet been tamed 10,000 years ago. Weaving, wagon wheels, and writing had not yet been invented. The Bronze Age and Iron Age had not yet begun. Stone buildings, philosophy, and science still lay in the future. [Ref. 2] No wonder the people of that time could not have anticipated today's capacities.

For us, in turn, the actual capacities of a civilization or intelligence 10,000 years beyond us will probably make our guesses seem unimaginative.

Interest in monitoring us

We see, then, that some highly advanced civilizations or some other forms of extraterrestrial intelligence (ETI) may exist in our galaxy. Presumably at least some forms of ETI are interested in monitoring or studying human civilization in some detail. At least they might want to explore and categorize our solar system and our civilization, just as our astronomers and anthropologists would want to do. And they might want to keep an eye on us to be sure we do no harm to other civilizations. They might also want to have a lively educative and scientific dialogue with us, or teach or convert or inspire or uplift us, or help us in some other way.

It is quite likely that some form of ETI is monitoring us (one way or another) in some detail. The opposite possibility is just too hard to accept. If there are other civilizations that are thousands of years beyond us, it is hard to accept that not even one of them wants to look us over--not even one of them is bothering to monitor us.

Interstellar probes may be the easiest way to get here. Although our human civilization is very young, it will no doubt launch a small smart interstellar probe within 200 years. Indeed, NASA plans to launch one within 30 years. Presumably any advanced civilizations in our galaxy developed this capacity long ago. At least one interstellar probe from at least one of these civilizations could well have reached our solar system already. If there are other civilizations in our galaxy with highly advanced technology, it seems very unlikely that not one of them has sent a probe to monitor or study us. Because this logical train of thought has already been spelled out thoroughly in an earlier paper [3], we need not review the details here.

Other ways of getting here, too, could be used in order to study us. Perhaps a spacecraft staffed by biological beings from a nearby star. Or faster-than-light travel from another galaxy. Or some other means that is far beyond today's human science, such as those discussed in science fiction and in the psychic and UFO literature (astral travel, a point of light or consciousness, an extraterrestrial disguised as a human, and so on). Or even a wise, all-seeing, all-knowing, naturally evolved intelligence somewhat similar to a secular god or guru.

In the end, however, smart unstaffed probes seem the most likely means, at least within our current grasp of science and technology.

Our train of thought leads us, then, to a clear but startling conclusion: it is quite possible that a civilization or intelligence far older than ours has already reached our planet. It may be here in the form of a small smart interstellar probe, or in some other form.

Interstellar probes 1960-1998

The possibility of detecting an interstellar probe has been a theme within the SETI field since Ronald Bracewell's 1960 article in Nature. [4] The 1966 book by Shklovskii and Sagan [5] devoted an enthusiastic chapter to "Interstellar contact by automatic probe vehicles."

The 1970s and early 1980s saw much lively debate about interstellar travel, colonization, and the Fermi paradox. Steven Dick's history devotes eleven pages to this debate, and notes that "by 1984 the furor raised by the galactic colonization thesis reached its peak." [6]

During the 1980s, two search strategies were tried. Freitas and Valdes [7] looked for a probe at a Lagrange point and Papagiannis [8] analyzed infrared data from the asteroid belt. During this period, the scientific literature on extraterrestrial probes generally assumed they would be fairly large, with limited and inflexible intelligence--perhaps programmed to deliver a recorded message to us if triggered by the correct stimulus. My 1991 chapter on ETI, for instance, said "a complex probe might be programmed to release a significant detailed message to any beings who trigger it by approaching it, by directing certain radio waves or laser beams at it, or by achieving an advanced state of technology." [9] In the 1990s, rapid advances in computers, robotics, space exploration, and nanotechnology indicate that interstellar probes may be much smaller, smarter, closer, and more knowledgeable than previously thought. Because of molecular manufacturing (nanotechnology), each probe might be smaller and cheaper than a basketball or a bottle of champagne. The idea of small smart interstellar probes suddenly became mainstream in 1997 when NASA adopted the goal of launching such a probe by 2030.

A probe from a highly advanced civilization might be even smaller. If our current nanotechnology literature is correct, a probe could be smaller than a coin, but smarter and more knowledgeable than a human being.

It could also, of course, be much larger. Greg Matloff has recently noted: "Common perceptions of technically advanced extraterrestrials assume they are talkative creatures who stay home and send radio signals in our direction. But because success has thus far eluded terrestrial radio astronomers, it may be wise to alter our misperceptions and broaden the search net. Perhaps extraterrestrials, or their robotic proxies, venture well beyond their home solar system on board starships, as our terrestrial robots have done with the Pioneer 10/11 and Voyager 1/2 extrasolar probes." [10]

Monitoring our telecommunications

In what ways would a smart probe monitor us, once it reached our solar system and our planet?

In addition to visual inspection, the most likely approach is to monitor our telecommunications. An advanced intelligence combined with highly advanced technology could easily monitor radio broadcasts, fax, email, the World Wide Web, and our other telecommunications. Most of these can readily be intercepted as they travel between the ground and a satellite, or between two microwave relay towers. Our own intelligence agencies are already doing this on a massive scale [11] and can even monitor an individual computer screen from a van parked a few blocks away: presumably a visiting probe is thousands of years beyond our capabilities.

Note too that a probe might well be able to use molecular manufacturing techniques to produce additional probes or other equipment needed for this task. It might also use a fog made up of millions of smart nanomachines that can form themselves into various objects. To the human reader this sounds like unrestrained science fiction until one notes which major governments, armed forces, car manufacturers, and scientists are actively pursuing nanotechnology projects.

Presumably a smart probe is capable of learning one of our languages, just as human children do. And translation should be easy: after all, some human web sites can automatically translate a document in less than 10 seconds.

ETI will presumably choose the World Wide Web as a particularly good way to learn about our contemporary civilization. As Jaron Lanier points out, "the Internet has created the most precise mirror of people as a whole that we've yet had. It is not a summary prepared by a social scientist or an elite think tank. It is the real us, available for inspection for the first time. Our collective window shades are now open. We see the mundanity, the avarice, the ugliness, the perversity, the loneliness, the love, the inspiration, the serendipity, and the tenderness that manifest themselves in humanity." [12]

An intelligent probe, then, will likely monitor the World Wide Web as one key part of its efforts to learn about us. This gives rise to a promising new search strategy. Perhaps we could use the World Wide Web to interact with ETI.

Several web pages have already acknowledged the possibility that an extraterrestrial reader or two could look at their page someday. Here are several examples:

(a) The web-based "Invitation to ETI" project will be described later in this paper. It was launched in 1996 by Allen Tough. [13]

(b) The SETI@home project asked for four types of volunteers in its early stages: programmers, illustrators, science teachers, and "Aliens: If you're reading this, you can save us a lot of trouble with one simple email!" [14]

(c) The Planetary Society's web page has invited readers to "submit your greeting to extraterrestrials" as one way to "participate in the search for extraterrestrial intelligence." [15] These greetings are then displayed on the Web, presumably for extraterrestrial readers as well as human readers.

(d) Above its counter, the Columbus optical SETI page says, "While the number of times that Aliens have accessed this home page through the Optical Interstellar Information Superhighway (Intra-Galactic Internet) is unknown, the number of hits by [humans is....]" [16]

(e) A Montreal-based bilingual web page opens with this greeting: "Hi, e.t.! I am a female mammal of the human species."[17] This web page then urges ETI to "read a few pages from the menu on your left before you set foot (paw, rod, tentacle, wheel, tripod, or whatever you set foot with) on our planet." The page explains some of our human foibles to ETI, and offers to build a web site for ETI "if you want to communicate with humans."

(f) The Extraterrestrial Anti-Defamation Organization (ETADO) describes itself as "a worldwide association created to challenge negative stereotypes about our extraterrestrial visitors." Its web page "makes a standing offer: ETADO will assist any bona fide extraterrestrial who desires to file an individual or class action lawsuit against any terran government, media venue or religious organization for defamation of character, slander or libel." [18]

Let's summarize the line of thought up to this point. First, there is general agreement in the SETI field that any alien intelligence or technology we detect will likely be thousands or even millions of years beyond ours. Second, such an advanced intelligence and technology is presumably interested in monitoring and studying us, and has the capacity to do so one way or another. As a small smart probe or in some other form, then, ETI likely reached our planet long ago. It is probably monitoring our telecommunications (just as our own security agencies do), including the World Wide Web. Suddenly, when the Web became widely used in the mid-1990s, a fresh approach became possible in the search for extraterrestrial intelligence, as we will see in the next section.

Invitation to ETI

While monitoring the World Wide Web, ETI should have little difficulty using the web search engines and directories, and then finding the web pages of particular interest. As it checks key words such as "extraterrestrial intelligence", it will come across the following URL: At that address it will discover an "Invitation to ETI" from a group of SETI scientists and others who are inviting ETI to communicate. ETI will note that this group appears enthusiastic, well-intentioned, thoughtful, friendly, and eager to communicate. The group also hopes that ETI will want to proceed toward a worldwide educative and scientific dialogue with humankind, perhaps even leading eventually to people supporting formal relations between ETI and the United Nations. And the coordinator of this invitation to ETI has already developed a list of questions for ETI based on a survey of 225 people. [19]

After discovering these web pages, what will ETI do? Four possibilities come to mind.

(a) Long ago, ETI may have decided (or been instructed) not to interact with humans under any circumstances. Or it may have its own clear-cut agenda that does not allow interaction at present. In either case, ETI will not reply to the invitation.

(b) ETI may have decided not to interact with humans until we have eliminated warfare and armed conflict. In this case, ETI might tell us so, or it might help us achieve worldwide peace, or it might simply ignore the invitation.

(c) ETI may be waiting for a formal invitation from the IAA SETI Committee, UNESCO, the UN General Assembly, COPUOS, the Planetary Society, or some other global organization.

(d) Or ETI may reply enthusiastically to our informal invitation. "At last, after so many years of waiting, an appropriate group invites me to communicate! I had considered initiating communication with the United Nations, but I foresee unhappy consequences if I choose that route (for the same reasons that my own civilization long ago replaced nation states with more flexible and harmonious forms of governance). So I am glad to receive a thoughtful invitation to communicate with a flexible group of highly appropriate individuals, who in turn have links to appropriate global organizations. I cannot think of a better option for my initial human interaction."

Search strategies

If a super-smart probe or some other form of highly advanced ETI has already reached our solar system or planet, how can scientists proceed to detect it? Four scientific search strategies seem particularly promising.

(a) Gather together a flexible group of SETI scientists to issue an informal invitation on the World Wide Web, as discussed in the previous section. Since we have no idea of ETI's purposes, methods, and preferences, this strategy is at least as promising as any other.

(b) Encourage one or more of the large global scientific or political organizations to issue a formal invitation on the World Wide Web. Seek major news coverage of this invitation in case ETI monitors the news media but not the Web. Potential organizations include the IAA SETI Committee, UNESCO, ICSU, COPUOS, the UN General Assembly, and the Planetary Society. The SETI field could encourage each of these organizations to create and post its own invitation to ETI on the World Wide Web.

(c) At locations where many unidentified flying objects have recently been reported, try to record solid repetitive data showing the physical presence of extraterrestrial technology. Such efforts over the years have used still cameras, video cameras, and a variety of measuring and recording equipment. The equipment is usually carried by hand, in a mobile van, or in a rented helicopter, but it could also be left stationary on an autonomous scanning platform. (In addition, various groups have tried lights, laser beams, sounds, meditation, landing platforms, and other means for attracting ETI to their particular site.) The next needed step is to develop highly sophisticated equipment and calibration, because only a rock-solid research design can collect data that will be accepted by mainstream science. A careful design that is carried out for many years may enable scientists to confirm the existence of ETI, or to disconfirm the ETI hypothesis for UFO sightings.

(d) Look within our solar system for optical, radio, or infrared evidence of small or large spacecraft (either active or abandoned). The Lagrange equilibrium points, the Moon, and the asteroid belt are often mentioned as obvious places to check for current activity or ancient artifacts. On Earth itself, presumably our security and intelligence agencies already monitor all parts of the planet.


The icon of the radio telescope has long dominated the SETI field. This extraordinarily narrow view of a wide-ranging scientific field is no longer appropriate. The scientific search for extraterrestrial intelligence can now include an array of at least seven potentially effective strategies.

Three of these strategies seek extraterrestrial signals arriving here after traveling from a source that is many light-years away: these three are (1) radio SETI, (2) optical SETI, and (3) active SETI.

And this paper has mentioned four strategies for extraterrestrial intelligence that has already reached our planet. These four are: (4) an informal invitation to ETI on the World Wide Web from a group of SETI researchers, (5) a formal invitation to ETI on the Web from an official international organization, (6) highly sophisticated data collection at UFO hot spots, and (7) a search within our solar system for optical, radio, or infrared evidence of small or large spacecraft.

Most of these seven strategies are relatively neglected and underfunded at present.

The phenomenon that we are trying to detect is so advanced, so unknown, perhaps so old and wise, that we cannot be sure which of these strategies is most likely to succeed.

Faced with the task of detecting an intelligence about which we know so little, how should scientists respond? I hope they will respond by fostering several strategies, thus enhancing our chances of achieving contact.


  1. Ray Norris, "Can science survive a SETI detection?" July 14, 1998.
  2. Nigel Calder, Timescale: An atlas of the fourth dimension. New York: Viking, 1983.
  3. Allen Tough, "Small smart interstellar probes," Journal of the British Interplanetary Society, Vol. 51, pp. 167-174, 1998.
  4. R. N. Bracewell, "Communications from superior galactic communities," Nature, Vol. 186, No. 4726, pp. 670-671, 1960.
  5. I. S. Shklovskii and Carl Sagan, Intelligent life in the universe. New York: Dell, 1966.
  6. Steven J. Dick, The biological universe: The twentieth-century extraterrestrial life debate and the limits of science. New York: Cambridge University Press, 1996. Debate pp. 443-453; quotation p. 450.
  7. Robert A. Freitas Jr. and Francisco Valdes, "The search for extraterrestrial artifacts (SETA)," Acta Astronautica, Vol. 12, pp. 1027-1034, 1985.
  8. Michael D. Papagiannis, "An infrared search in our solar system as part of a more flexible search strategy." In The search for extraterrestrial life: Recent developments, M. D. Papagiannis (ed.). Boston: D. Reidel, 1985.
  9. Allen Tough, "Intelligent life in the universe: What role will it play in our future?" In Crucial questions about the future, pp. 87-102. Lanham, MD: University Press of America, 1991 and London: Adamantine, 1995.
  10. Greg Matloff, Searching for starships, SETIQuest, Vol. 4, No. 2, pp. 12-14, 1998.
  11. Nicky Hager, Secret power: New Zealand's role in the international spy network. Nelson, NZ: Craig Potton, 1996.
  12. Jaron Lanier, "Taking stock: So, what's changed in the last five years?" Wired, January 1998, p. 60.
  13. Invitation to ETI.
  14. September 1997.
  15. December 11, 1997.
  18. May 8, 1998.
  19. Allen Tough, "Our questions for ETI."

Copyright © 1998 by Allen Tough. All rights reserved.
This paper is a longer version of an oral presentation on "Interstellar Probes Within SETI, 1960-1998" at the International Academy of Astronautics SETI meeting in Melbourne (Australia), September 1998.

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