The Search for Extraterrestrial Intelligence

star field


Why no Signals?

After 60 years of searching, we have received no intelligent signals from outer space and see no evidence of extraterrestrial visitors. Why is this?

We are actually in a poor position to speculate on how planetary civilizations evolve beyond the point we are at and what their future motivations may be. We have barely started human space travel but we have found that after six months in space there are serious questions whether organisms evolving in a one-g environment can survive for periods of years in zero-g. Even if we become capable in future decades of assembling the enormous rotating structures needed to restore a one-g environment in space, there are still questions of the effect of the Coriolis force and the mental stability of crews subject to the social stresses of isolation and sensory deprivation. If these were the only considerations, we would perhaps take an optimistic view that such problems will be overcome and expansion into the solar system and Galaxy would follow.

However, this would be to ignore the exponential increases that are surging forward in computation, artificial intelligence, and genetics. We have no idea how these will change our lives in the next three or four decades. Our slow, linear advances in propulsion and tin-bending pale in the face of the speed-multiplying effects of the feedback of advances in these new areas and their potential interactions. We do not know who we will be in mid-century, or how we will think of our role in the universe. There is already talk of immortality being achieved by then, by transferring the total contents of a individual's brain into a an advanced computer running a total brain simulation. An initial simulation of this type is already under consideration by the European Union as a billion-Euro project to stimulate the region's technical advances.

It is difficult to speculate on the nature of civilizations thousands of years older than ours that have gone well beyond such advances. We may simply be unaware of the technical reason  why we cannot pick up their signals.

Or we have a wrong image of advanced civilizations. We imagine them as populated by gung ho engineers and scientists forever probing the mysteries of the universe.  But an advanced civilization may resolve the mysteries of the universe within a few thousand years and, no longer pursuing advances in the physical and biological sciences, go on to other things. Our level of intelligence, science, and social accomplishments may be of no interest to them. They've seen it all before.

But the simplest reason for not having detected extraterrestrial signals is that space is too big. The lack of signals can readily be explained by the vast amount of physical space and electromagnetic spectrum that has to be searched. The analogy has been drawn that our situation at present is like trying to described the contents of Earth’s oceans from examination of a single cup of water.


Civilizations are Rare

There may be other reasons for lack of communications, of course. Life may have only evolved once under highly improbable circumstance on Earth alone. That would certainly account for absence of extraterrestrial communications. Given the likely abundance of planets capable of supporting life, however, this view of Earth as unique in the universe seems to be not strongly supported by the evidence we have. Perhaps the answer is that intelligent life does not evolve very often. However, since evolving species survive by out-competing others in their environment, intelligence may be the ultimate destination of evolution because it is a multiplier factor for survivability. Since we can see the evolution of intelligence on Earth in both mammals and birds it appears realizable in different brain structures. So the evolution of intelligence is likely, once life starts evolving.

Even so, intelligent civilizations may be improbable. But civilizations are the end point of evolution of social cooperation, which is also a multiplier for survivability. Intelligence and social sensitivity that lead to civilization are likely to come together at some stage to promote the survivability of a species. The problem, as we know from our own experience, is that civilizations rarely last more than a few hundred years. they break up for a variety of reasons. If this is characteristic of extraterrestrial civilizations with evolving intelligence, then there will be few or none at this time, even though millions may have emerged on different planets in the past 5.5 billion years. If there are a few of these civilizations remaining, then they are likely to be very sparsely scattered in the Galaxy, thousands of light years away from us, poorly situated for communication.

Civilizations may also be prevented from evolving, or may be destroyed if they do, by instability of their home planet, or by environmental catastrophes like coment impacts or nearby supernova.


Too Far Apart

The probability that short-lived civilizations are likely to be spread far apart in space and time is suggested by calculations based on the Drake equation. That calculation of the number of Galactic civilizations and their average separation is based on optimistic assumptions about the frequency of appearance of planetary civilizations. Even so, it shows that civilizations with an average lifespan of 1,000 years will be spaced about 5,000 light years apart. They are unlikely to solve the logistical and communications problems of Galactic piracy before they expire.

To be spaced close enough together to communicate and travel between star systems, civilizations should have lifetimes of millions of years, or draw a lucky spot in a somewhat random distribution of Galactic locations. To achieve such lifetimes requires a very stable social system. This means that predatory aggression and religious strife have to be overcome by turning instead to universal cooperation and either a single global religion or an atheistic belief system able to meet their social needs. The solutions adopted will influence the content of the SETI intercepts we may collect.

In addition to the age of the population, the number of civilizations in the Milky Way is influenced by all of the other factors in the Drake equation. The additions to the detected planet population in the Galaxy announced by the Kepler Mission and ground telescopes, and improvements in the definition of the zone around stars able to support life on planets, have changed the probabilities previously calculated. Also there are alternative viewpoints about the probability of civilizations arising, even though the probability of life appearing on planets has risen with the discovery of extremophiles capable of living in very hostile environments. Theological considerations can lead another viewpoint to the probability of extraterrestrial communications.


Lifetimes are Short

Even if we search for a few more centuries we may still come up empty handed, because the average life of planetary civilizations is shorter than the time it takes light or radio waves to travel between them. A civilization that recognizes itself to be in this situation could well decide that the mounting of a major effort of interstellar communication would be pointless. It would be communicating with nothing but empty space.

If extraterrestrial civilizations are uniformly distributed throughout the Galaxy, we can calculate their separation by estimating the number of civilizations that are present at any one time. It appears that the number of planets capable of sustaining life may be in the hundreds of millions or even billions. However, the number with civilizations is critically dependent on the probability that simple life will successfully evolve into highly complex social organisms. It is also strongly dependent on the probable lifetime of planetary civilizations. These controversial probabilities are discussed under ET Civilizations. Under different assumptions the estimates of the probable number of civilizations vary from one (us) to millions. A low probability of for evolution of civilizations from simple life, or a high probability that a civilization will destroy itself or its environment within a few centuries, can account for the absence of extraterrestrial communications.

Given the age of the Galaxy, civilization lifetimes below a million years mean huge numbers of dead civilization if at any one time sufficient numbers are present to be close enough to communicate. For every civilization out there, 10,000 may have passed away.


We are Quarantined

We cannot become a technically advanced civilization capable of extended space travel and communication unless we can evolve socially to live at peace and preserve our planet. We may receive no communications from other civilizations because we are at a stage in our evolution where we can potentially destroy our environment, ourselves, and other species, either by war or by disease, waste and pollution. Significantly, the physical constants of the universe, notably the strength of gravity, prevent us from damaging extra-solar planets in a similar fashion, because they are way beyond our technological reach. For this reach to be extended requires large advances in our technology or discovery of new principles of physical science whose presence is merely hinted at. The time it takes to develop a suitable technology or to exploit new physical principles is likely to be very much longer than the time it takes to either annihilate ourselves or to evolve the necessary social qualities that will enable us to preserve and enhance our planet.

Any advanced extraterrestrial civilizations that exist will be aware of this, and will treat other civilizations exhibiting our present level of technology as something to be quarantined—no visits, no communications to be sent, restricted access to communications received. Our own experience with world wars, suicide bombing, bioweapons, and malicious software would indicate that this is a prudent strategy

There have been suggestions that our planetary neighborhood may be like a nature park where the inhabitants are left undisturbed for the sake of longitudinal studies by more intelligent beings. But this suggests a uniqueness that we do not have if millions of advanced civilizations have evolved in the universe. An alternative explanation points to the fact that sampling by the Kepler Space Telescope indicates there may be 50 billion possible planetary systems in the Galaxy. There is a strong chance, then, that the solar system as a possible location of intelligent life has not yet been investigated by another civilization, and consequently no communication has been attempted.


Contrary to Dogma

Recent findings from astronomical spacecraft and ground observatories suggest that there may be hundreds of billions of planets in the Milky Way, and many hundred millions may support life and possibly civilizations. In the universe as a whole, there are over 100 billion galaxies. Thus the potential number of civilizations could also approach hundreds of billions. This raises significant questions for religions. Do Christians believe that the passion of Jesus Christ saved all these civilizations? Does a prophet of Allah fly on a Buraq to  paradise from all those planetary orbits?  Does Krishna never tire of driving Arjuna’s chariot into battle and justifying a caste system in which a warrior may kill his relatives without remorse?

As Christianity has a readily accessible collection of dogma developed over the past 2,000 years, it is possible to examine in some detail the problems posed to it by extraterrestrial civilizations. This was the subject of a presentation by Professor Christian Weidemann,  of  Ruhr-University, Bochum, Germany, speaking at the 100-year Starship Conference in Oralando, Florida. last October.

Christians believe that some 2,000 years ago God appeared in the world in human form as Jesus Christ, preached the proper way to live to achieve imortality, and allowed Himself to be put to death by crucifixion. By this sacrifice He is believed by most Christians to atone for their sins, allowing them to avoid God’s wrath. This unique series of events saved the world, according to Chapter 3 of the Gospel of John, verses 16, 17, 35, and 36. By “the world” John probably meant “all creation” as he could envisage it.

In the light of our improved understanding of the universe,  Professor Weidemann discussed the possible fate of the inhabitants of extraterrestrial worlds.

He suggested that if Jesus saved only the Earth, then either billions of civilizations may be the subject to Gods’ wrath, or they are without sin. If they are without sin, then Earth is unique in being created with sinful inhabitants who need a sacrifice of God’s only son to avoid His wrath. Weidemann doubted that this alternative could be supported. The principle of mediocrity , which holds that our own experience is not likely to be exceptional, indicated to him that if there are other intelligent beings in the universe they are likely to be sinners too.

If this is the case, asked Wiedemann. would God send his incarnation as Jesus to every inhabited planet, to undergo crucifixion to save those worlds and atone for the sins of their inhabitants? Based on scientific estimates of how many civilizations may exist in the universe and their average lifetime, Wiedemann calculated that a Savior with a life-span of 30 years would have to be manifest in 250 incarnations simultaneously at any one time. For a truly corporeal Jesus, incarnated as a human, this alternative would be physically impossible.

The leaves the alternative, argued Weidemann, that God would become incarnate not just in the form of Jesus but in the form exhibited by the dominant species in each extraterrestrial civilization.

It is possible to see what this involves from the manner in which God became incarnate on Earth. This described carefully in the definition of the person of Christ developed by the Council of Chalcedon in 451 C.E. It can be translated as follows:

“Therefore, following the holy Fathers, we all with one accord teach men to acknowledge one and the same Son, our Lord Jesus Christ, at once complete in Godhead and complete in manhood, truly God and truly man, consisting also of a reasonable soul and body; of one substance with the Father as regards his Godhead, and at the same time of one substance with us as regards his manhood; like us in all respects, apart from sin; as regards his Godhead, begotten of the Father before the ages, but yet as regards his manhood begotten, for us men and for our salvation, of Mary the Virgin, the God-bearer; one and the same Christ, Son, Lord, Only-begotten, recognized in two natures, without confusion, without change, without division, without separation; the distinction of natures being in no way annulled by the union, but rather the characteristics of each nature being preserved and coming together to form one person and subsistence, not as parted or separated into two persons, but one and the same Son and Only-begotten God the Word, Lord Jesus Christ; even as the prophets from earliest times spoke of him, and our Lord Jesus Christ himself taught us, and the creed of the Fathers has handed down to us.”*

Presumably. on the basis of Weidemann’s line of reasoning, the holy Fathers on other planets would similarly describe their incarnation of God as “like us in all respects”. These different physical manifestations, suggested Wiedemann, could be viewed as constituting a polytheistic religion, which would be inconsistent with the monotheism of Christianity. Thus this alternative also would not be acceptable to Christian thought.

In this way, Professor Weidemann eliminated the various alternatives whereby extraterrestrial civilizations might be saved from the wrath of God by the Son’s atonement for their sins. He concluded that this indicates that the initial assumption that there are many extraterrestrial civilizations is not correct. That is, we are alone in the universe and have been chosen by God to explore it and carry our civilization to planets around other stars.

This theological conclusion is consistent with a line of scientific reasoning that sees life in the universe as widespread but the emergence of civilizations as being very improbable*. Both of these viewpoints require further examination in the light of current interest in the future of civilization and the search for extraterrestrial intelligence (SETI).

*The Chalcedonian Definition. Agreed at the Fourth Ecumenical Council at Chalcedon in 451. @

** This thesis is put forward in Rare Earth, by Peter D. Ward and Donald Brownlee (Copernicus Imprint of Springer-Verlag, NY, 2000).

Woodpeckers of the Galaxy

 Jared Diamond wrote a provocative article in 1990 arguing that it was unwise to assume a high probability for evolution of an intelligent species comparable to homo-sapiens elsewhere in the universe. He added that our increasing ability to destroy ourselves and our degradation of our environment raise the probability that civilizations such as ours may last only a few hundred years from the time they start to seek evidence of extraterrestrial radio transmissions. Together, argued Professor Diamond, these two probabilities can account for our failure to detect transmissions indicating extraterrestrial intelligence. Our singularity and accelerating progress toward self-destruction may therefore benefit the universe.

 Professor Diamond based his argument for the rarity of extraterrestrial intelligence on the global distribution of woodpeckers. He demonstrated that this species has evolved only once in one area of Earth and not in other areas where it could have evolved with equal success. That is, a particular evolutionary line can emerge successfully in one location but may not appear in other locations that look equally favorable. Thus, although we may detect planets in habitable zones around stars, extraterrestrial intelligence as we understand it may not exist there. We may be the woodpeckers of the universe.


'Alone in a Crowded Universe' by Jared Diamond, Natural History, June 1990.