THE PROBLEM WITH SETI
Message transmitted to outer space -"Is there anyone out there?"
Message received from outer space - "Nyet!"
The SETI movement
Search for Extra-Terrestrial Intelligence is a program that involves amateur and professional scientists in many countries which sweeps of the sky for radio signals emanating from outer space. SETI enthusiasts believe that among the billions of other solar systems out there, there must be a number with intelligent beings that are as advanced as us humans and have the desire to communicate with us and their search sets out to detect signals that they are sure must be there embedded in the noise that comes from beyond the Earth's vicinity.
If we assume, quite reasonably, that all things in our universe are governed by the same physical laws and chemical processes, we may conjecture that many other planetary systems other than our own must have evolved worlds that are capable of supporting and nourishing life forms, or, at least, proto-life forms. The SETI proposition is that detection of signals with some form of coherence would provide sufficient evidence that there is sentient, intelligent life out there beyond our solar system.
While it may seem improbable that other worlds could have evolved life forms of a humanoid nature, especially considering the unique set of conditions needed to support such a life form, SETI enthusiasts point out that the huge number of star systems out similar to our own solar system decreases that improbability to virtual certainty. Recent press releases by cosmologists suggesting that there are many more planets of similar size and composition to Earth appears to support their argument. However, some of the assumptions made either explicitly or implicitly by SETI enthusiasts may not be as sustainable. Lets examine these assumptions.
Before we continue, there are two big questions to be considered. One, what is intelligence? Two, what do we take as a sign of intelligence? Many papers and books have been written in attempt to define intelligence. Many psychologists duck the problem by defining intelligence simply as "what intelligence tests measure." But will such an approach do to assess the intelligence of an extra-terrestrial being? "What is an orange?" And "Name four past presidents of the United States of America?" Such test items are hardly applicable since they refer to things and events of our own terrestrial environment, or to ideas that are peculiar to our way of thinking and running affairs. Nor will repeated patterns of a complex series of pulses necessarily do as these could conceivably be generated by several binary star systems that happen to be in a line.
One alternative definition of intelligence is by use of a notional test proposed by Alan Turing to decide if a computational system is a good simulation of an intelligent system. This method asks if a jury can discriminate between answers given by the system to whatever questions they might put from those that would be given by a human. The "Turing Test", however, defines intelligence in terms of how a human might be expected to respond in a special set of circumstance and is, thus, very limiting on what ultimately might be accepted as "intelligence." An alien could be intelligent in other ways than is a human.
So, what is to be that special status when the putative intelligent entity is from outside our solar environment? Do we take apparent complex behavior as the indicator? Many pet owners claim that certain behaviors shown by animals is indicative of intelligence, but there are many cautions and objections to be overcome before we may conclude that such signifies intelligence. The same goes for machines, and for supposed ETís. Usually we tend to take something that is unexpected, and perhaps intangible about the behaviors shown as an indicator of the special status of intelligence. What we appear to mean by "intelligence" is that there is something unexpected or unpredictable about the way the system interacts with environmental circumstances to bring about a outcomes we would call 'smart' that cannot be explained by reference to mechanistic or systematic processes. However, there are still many pitfall waiting. For example, we are sometimes amazed at the ability of ants in finding the shortest path between the nest and a source of food and we are inclined to attribute this behavior to "ant intelligence, but it appears that ants leaves a pheromone path in their meandering. The more indirect paths decay quicker than the more frequently reinforced direct path to produce, collectively, what is known as "emergent" behavior. Sometimes we take ability to take part in interactive behavior as a sign of intelligence, but this test also has problems. We can see planets interacting with each other and with the sudden appearance of stray or wandering celestial bodies. Could not some observer, ignorant of Newtonian gravitational mechanics, say that the celestial body that adjusts its orbit to accommodate to a wandering intruder is displaying intelligent interactive behavior? If we look, we may even find signals in the form of magnetic waves from that body that could be interpreted as saying, in effect, "I see you and I am moving in response to your presence."
The difficulties of defining intelligence will not be labored further. But the fact that difficulties exist leaves the SETI project with problems of exclusion and inclusion. On one hand we may be restricting our perception of the possibilities far too much by thinking of intelligence in terms of our own experience and limited terms of reference. It would be ironical indeed if we were to reject a signal from a super being as un-interpretable garbage because of our own limited understanding of what constitutes intelligence. On the other hand, as illustrated by reference to ant behavior, what to us might look like high intelligence may be due entirely to circumstances external to the being that is supposed as being intelligent.
The problem of estimating ETI likelihood
We have been told by cosmologistí that there must be billions of star systems in the universe that have planets of earth size. However, this does not necessarily mean billions of earths with similar environments and state of development. How many of such would be likely to have a world of ETI beings that are at least as sentient, curious about the existence of possible neighbors, have the capacity and technology to communicate with us on our terms? Assuming that such worlds would have to have environments and supportive conditions somewhat similar to our own, we can estimate roughly the proportion of planets that meet this requirement.
We Earthlings live in an environmental space, or niche, that is remarkable in that it keeps within fairly close tolerances in terms of celestial scales. It is within these tolerances that we evolved more-or-less by a sequence of marvelous co incidents and accidents, each of which were of astronomic improbability if we were waiting around at any particular stage for that set of precise events to occur. It is only that they did happen to occur that human civilization exists in its present forms today. We can survive without special devices such as spacesuits only if the temperate stays within about a 20-degree range, and if pressure does vary not much from 101 kp. We need an atmosphere that is about 21% oxygen. Because our flora and fauna, and the total supporting wherewithal has all evolved more or less within the same bounds, our own bodies have co-evolved to work efficiently within these bounds, and, by and large, only within these bounds. We have also evolved sensitivities to certain wavelengths of electromagnetic waves, and to pressure waves that work best in the environment that has been created within a very thin and peculiar layer of atmosphere of this one special planet which we call Earth. These conditions have formed and guided the way we and other animals move and communicate. We thus do not naturally respond to electromagnetic radiation outside the band of frequencies we call light, or to pressure waves outside the 20 to 20,000 Hz band of frequencies that are audible to us. Familiarity with these environmental features has conditioned our thinking about things, and our ideas of what may be possible.
In stellar space, in contrast, many other possibilities exist. Temperatures can be from -273c to millions of degrees, and pressures can be from high vacuum to millions of kilopascals, or whatever, and gravitational fields that would crush a steel cube into a minute dot. While light is almost ubiquitous, sound in our terms is not. (While we use light and sound to communicate, there are other forms of radiated energy that could carry communications - e.g. gravity waves.) *
Assuming that each environmental space, or aperture for an ET, regardless of form, would be of approximately the same size as that we have on Earth, we may gain a ballpark estimate of the possible different forms that could exist by dividing each of the seven or eight relevant dimensions by aperture size. First, dividing the total temperature range that exists in extra-terrestrial space by 20, the range in degrees that we can exist within, yields at about 50,000 slots. (or, more conservatively, about 10,000, or 104, if we allow slots to be proportional to magnitude.) Summing over a similar division of the seven or eight other dimensions yields between 1011 to 1012 environmental niches in which an life forms might conceivably evolve, or indeed could have evolved. It is possible that life forms could have developed in a way that is as various as those found on Earth within each of the 1011 or 1012 niches.
The question is, that of all these possibilities, how many ET's could there be that would be compatible enough with us to bridge the communications gap? If we expect to be able to understand messages from an alien intelligence, and to communicate back perhaps, we will need a fair degree of system compatibility with not only the alien signaling system, but also the alien's physical world for we will only be able to make sense of any message if semantic references are similar to ours. That is, the physical structure and constraints of their world and their environmental referents will have to be reasonably like ours. If it were otherwise, their signs and codes would have little or no meaning to us, and vice versa.
Considering that we are talking of 1011 to 1012 possible environmental niches that are each different in some way from our own, and mostly in very big ways. Without limiting in any way the possibility that any or all of the niches could have developed intelligent systems, the number of niches that will have some overlap with our own that will meet our criteria will be small indeed! Restricting our survey to earth-size planets changes nothing, since that simply reduces the number of candidate worlds. It thus can be argued that this will drastically reduce the number of possible sources for SETI type signals that would be in any way meaningful to us. Any sustainable arguments to the effect that only few of these would be appropriate and stable enough to develop intelligent forms would reduce that number even further. Thus, even if there were ten billion, or 1010, solar systems out there, dividing through with the niche estimates leaves very few candidate world possibilities indeed.
A further consideration is that, even if there is a planet out there that offers a similar environment to our own, and bears a life form comparable to us, to communicate it must have developed to roughly the same stage as ourselves. Of the 400 million years our planet has had some life-form extant, we humans have only been around for less than one hundredth of that time, and had the ability to communicate beyond Earth for about 100,000th part of that. Given that we persevere with our search for another 60 years before losing interest, as we surely will if we have no decent results, then our search-time aperture will only be 100,000th of our existence. If there is at least one ETI world out there, what are the chances of overlapping endeavors to communicate?
One further problem for SETI is the distance we must suppose a signal must travel to reach us. While some possible sources may be a matter of a few light-years away, others are as far out as 15 billion light-years. If we did detect the arrival of a suitable complex signal, it could be that the signal was sent anywhere between several decades and several billion years ago. Without an agreed time code to peg the time of sending, we will have only our guesses as the age of the message and its distance of origin. We would then have the possibility that the message sender, and perhaps even the species were long since extinct. Reception and eventual decoding of such a message from a more distant source than - say, one hundred light-years away, would be a pyrrhic victory indeed.
Apart from mere detection of an ETI, practicable communication with such seems only possible within a limited envelope of space, say, out to about 15 light-years radius, for to have any surety that the signal we have picked up is indeed from an ETI we will need to perform at least one 'handshake.' That is, at least one message must pass each way for one party to know that a message has been interpreted correctly. The 25 years arises for us because twice that, the time for our handshake to be confirmed, would be about the maximum working life of the handshake sender. It seems unlikely that successors to present senders would be terribly interested in a handshake transaction initiated a century or so before them, especially if the next round was not expected to arrive until they themselves would be long gone.
A signal horizon of about 25 years would leave all but about 1/3000 millionth of the posited universe out of reach. This, of course, cuts down the possibility of establishing contact with an extra-terrestrial drastically. However, if the considerations discussed below are valid, it may be that it does not matter anyway.
Why bother saying hello?
Except the possibility that in receiving a signal from outer space that is significant of an intelligent sender is simply eavesdropping on communication between parties that are known to each other, or the chance encounter with a wandering alien "star trek" ship, why would an alien being send a message to us? For what purpose, or for what motive would an alien wish to be known, and possibly to communicate! While humans seem to have an inbuilt desire to talk to each other, and even to other animals, it is most possible that this is just a peculiarity created by our own social evolution. Why would or should non-terrestrial intelligent life forms share this characteristic?
The usual purpose of any communication is to receive some return response that is meaningful - "I want you to do something," or," Tell me something." For example, "We are about to demolish your planet to make way for a hyperspace bypass. Please vacate it immediately." Or "Do you have a . . . " One must wonder for what purpose someone some tens of light-years away may wish to exchange communications with us, even given our world systems are in some way compatible.
Exploration is one possible motive, with a payoff in terms of materials, colonization, or trade. While we ourselves have explored new worlds in the past for such purposes, these were on our own planet. Contrary to the traditional stories about sailors believing that they were in danger of sailing over the end of the earth, the principal explorers knew pretty well that whatever new lands to might discover would be pretty much like back home. In contrast, a would-be explorer several tens-of-light-years away, would have little idea of how our terrain might be arranged, the extant geothermal conditions, or of life-form possibilities, just as we, respectively, would have little idea of their world. If they do happen to have some information from a returned space probe, because of the delay, it is possible they may conclude that the earth is dominated by 20 metres long things with long necks and vicious incisors, or by green slime. In any event, stepping between interstellar worlds is considerably more difficult, and much more hazardous than is stepping between continents on planet Earth for us, and for aliens.
Establishment of communication with Earthlings as a prelude to a possible expedition seems also untenable proposition. For any ETI at many light-years remove, there is sure to be an abundance of material sources more readily at hand than the third rock from a small, dying star, and one that is not even visible from home base. If we were to suspect that material mining was a possible motive, our best option would be to stay very quiet. One never reveals wealth to strangers who might then try to take it from you. Besides, how would we handle meeting a being that turns out to be vastly and intimidatingly superior in intelligence than us? Would they even bother to be civil to us, or simply step on us like we do to ants?
Colonization has the problems of environmental compatibility again, and of getting here at any speeds short of that of light. Trade seems out for the same reasons. The immense costs of interstellar or intergalactic travel also puts all above motives for communication into the very, very unlikely bracket.
As to the eavesdrop possibility - while it may confirm our suspicion that we are not alone in the universe, it would be about as exciting as discovering from hard listening outside our bedroom window that somewhere in the neighborhood there are people who shout to each other in a language we don't understand.
This still leaves the possibility that there are aliens that, like humans, have this desire or curiosity to know if there is anyone beyond their world that is as intelligent as they, and who, moreover, wish to be friendly. No argument against this can be offered here. If SETI enthusiasts have fun while exploring this possibility, it their prerogative so to do. It has the added attraction of providing a mass of recorded information on electromagnetic radiation from out space for scientific analysis. However, friendliness to strangers is a cultural rather than an universal characteristic in humans. It would seem that the chance of finding an alien with such a human characteristic is very small indeed. Fishing in unknown waters can result in a surprising and exciting catch, but in this case the waters are very different from anything we have found fish in before. The prospect of a catch must also be very small.
Trick or treat?
Finally, if we do manage to detect, and perhaps communicate with, an extraterrestrial, where does it leave us? If we do connect, it will mean that to do so the ETI will be at least as advanced and as intelligent as us, and there is the possibility that it would be much more in both aspects. If it should turn out that they are about the same level in both, then, ho-hum, it would be not terribly exciting. If they are more intelligent, or we suspect that they are, then it is likely that we will not want to know that. Besides constituting a real threat to know that there is actually something out there that could beat us hollow, it would be an unbearable blow to our collective ego to discover that we are not the superior beings we would like to believe we are, but mere minors.
Perhaps, in essence, the SETI program is really an attempt to reify our image of ourselves as being the supreme intelligent being - apart from the Almighty. The SETI project, I suspect, is one we all secretly hope will fail, and it could even be argued that the way it has been conceptualized and set up guarantees that it will.