]]]]]]]]]]] WE ARE ALONE IN OUR GALAXY [[[[[[[[[[[[[[[[[ Frank J. Tipler (11-26-1988) From New Scientist, 7 October 1982, pp. 33-35 (Dr Frank J. Tipler is Associate Professor of Mathematical Physics at Tulane University, New Orleans) [Kindly uploaded by Freeman 10602PANC] SUMMARY: Faith in the existence of extraterrestrial intelligent life is so great that many astronomers urge governments to divert scarce research funds into the search for extraterrestrial intelligence. Yet there is no evidence that such life exists, and powerful arguments that it does not. * * * The possible existence of intelligent extraterrestrial life has always fascinated mankind. During the past 25 years several astronomers, notably Carl Sagan and Frank Drake of Cornell University, and Philip Morrison of the Massachusetts Institute of Technology, have proposed that we search actively for such beings by scanning the sky for their signals, using radio telescopes. Estimates for the cost of such a search range from ten to several thousand million pounds, and even at the lower end of this range the cost is very great compared with most scientific research. Before conducting such an expensive experiment, we should consider carefully whether the endeavour has a significant likelihood of success. I believe that such a search is doomed to failure, and that we represent the only intelligent species ever to exist in our Galaxy, and quite possibly the only intelligent species ever to exist in the entire visible universe. Before I give the reasons for my belief I should define what I mean by the expression ``intelligent being''. By ``intelligent being'' I mean a member of a living species that is capable of developing a technology comparable to ours, and which is, like the human species, interested in using this technology to communicate with other intelligent species, and is interested in exploring and or colonising the Galaxy. One might argue that this is too restrictive a definition, but this is the only kind of extraterrestrial life that searches with radio telescopes could possibly detect. I have two basic reasons for my disbelief in the existence of extraterrestrial intelligent beings. First, all the great contemporary experts in the theory of evolution -- Francisco Ayala, Theodosius Dobzhansky, Ernst Mayr and George Simpson -- are unanimous in claiming that the evolution of an intelligent species from simple one-celled organisms is so improbable that we are likely to be the only intelligent species ever to exist. Secondly, I have made calculations that indicate that interstellar travel is not only feasible but could be achieved quite inexpensively by an intelligent species only slightly in advance of us. If such a species existed, there would, therefore, be evidence of its existence on Earth or in the Solar System. How do these two arguments look in detail? The evolutionists contend that the development of intelligent life is extremely improbable because there is an enormous number of evolutionary pathways leading from simple one-celled organisms to many-celled creatures, and, in their opinion, only a very few of these pathways include intelligent beings. One might think that intelligence would be a property that would confer an enormous selective advantage on a species, and this would cause intelligence to evolve; but natural selection is more complex than this. It acts upon the entire body of a creature, not just on a creature's neurological system. In the vast majority of cases, a genetic change that results in an increase in the complexity of the neurological system will cause a corresponding adverse change in some other bodily characteristic that the creature needs for its immediate survival. The adverse change outweighs the improvement in intelligence, and the creature does not survive in order to pass on the increase in intelligence to descendants. Even more important than this trade-off effect is the fact that natural selection has no long-term foresight. Any genetic change that occurs must act immediately to increase the survival probability of a creature, or it will not be selected for. Evolution cannot accept a temporary net decrease in ``fitness'', in the Darwinian sense, in order to achieve a net increase in fitness several generations into the future. So the evolution of a given complex system can be expected to occur only once, because such a system requires the simultaneous appearance of many new genes or a change in several old genes together. The eye is an apparent counterexample. It occurs in many different forms in animals as different as vertebrates and cephalopods (octopus), whose eyes are very similar although their common ancester [sic] lies far back in Precambrian times, more than 600 million years ago. This seems like independent evolution of a complex system. But Professor Leonard Ornstein of the City University of New York, has suggested that the common ancestor already had an eye. Ornstein also points out that this hypothesis can now be tested by comparing the structural genes controlling eye development in cephalopods and and [sic] vertebrates. Modern techniques in molecular biology, developed for genetic engineering, make this possible, although the experiment has not yet been carried out. The ability to develop advanced technology is also built upon a very complex biological system. We would therefore expect that it is exceedingly unlikely to appear more than once. The improbability is so great, in the opinion of many evolutionary experts, that we are likely to be the only intelligent species in the Galaxy, if not the visible Universe. To my mind, however, the second argument is even stronger than the evolutionary argument. If ``they'' existed, they would already be here. The argument assumes that interstellar travel is feasible, which may seem an extreme claim. The human species had, however, already launched four very primitive interstellar probes: Pioneers 10 and 11, and Voyagers 1 and 2. All these have speeds in excess of the escape velocity from the Solar System, and had they been so aimed they could have been targeted to enter any one of several nearby solar systems in about 100 000 years' time. These probes were not so aimed, because they were designed for other tasks and lacked the instrumentation to explore other solar systems. We do not lack the necessary rocket technology to begin interstellar exploration using robot probes; what we lack, and only barely, is the proper instrumentation, the computer technology. What sort of computer technology would be required? I propose that the proper guidance computer should be what I call a von Neumann machine. This is a computer with intelligence close to the human level, capable of self-replication and capable, indeed, of constructing anything for which it has plans, using the raw materials available in the solar system it is aimed at. An interstellar space-probe carrying a von Neumann machine could work as follows. On entering a solar system, the probe would make several copies of itself using matter in the form of asteroids, comets and similar debris. According to present astronomical theories, such debris should be present in virtually every stellar system whether or not it contained planets. These copies of the probe would then be launched on to other stellar systems, where the process would be repeated, while data were sent back to the home station. Eventually, all the stars in the Galaxy would be reached by some descendant of the single original probe. The Galaxy would be explored for the price of one von Neumann machine! Once copies of the probe have been launched, the first von Neumann machine would enter a stellar system can concentrate on exploration. It could be programmed to construct whatever devices it needs for the task, and even to colonise the target system with replicas of the species that constructed the first such probe. All the information needed to synthesise a human being is coded in the DNA of a fertilised human egg cell. This information could in principle be stored in the memory of a von Neumann machine, which could be instructed to synthesize an egg and place the ``fertilised cell'' in an artificial womb. Remember that the probe has all of the raw materials of a solar system at its disposal, and all the energy it needs from the output of the central star in that system. In nine months there would be a human baby in the stellar system, and this could be raised to adulthood by surrogate parents, constructed by the von Neumann machine. A first generation of people could thus occupy a space station also constructed by the machine, or even be set loose on a planet. This colonisation scenario could be played out for any form of life that even remotely resembles the forms with which we are familiar. If for some reason the ``parent'' species did not which to ``colonise'' the Galaxy with its own form, they could have just as easily have instructed the probe to seed any suitable planet with one-celled organisms. Such a dispersal of single-celled organisms throughout the Galaxy has been proposed by Francis Crick, co-discoverer of the structure of DNA, who calls it ``direct panspermia''; the advantage of the von Neumann machine lies in the range of options open to the original constructors of the first probe, thanks to the probe's flexibility. This could colonise any stellar system that contained enough debris to manufacture a space colony; or they could seed the Galaxy with simple life forms and leave evolution to take its course; or they could simply explore. Such a probe could make contact with intelligent beings whatever their level of technological development. This gives von Neumann probes an enormous advantage over radio where the search for extraterrestrial intelligence (SETI) is concerned. With radio searches, we are restricted to searching for civilisations that have developed similar technology to our own, but which have not yet begun interstellar travel, nor developed a more effective signaling technique. There are no such restrictions with probes. A spaceship, built by a probe out in the asteroid belt, in front of Buckingham Palace, say, would have been noticed long before radio was invented on Earth. A key difficulty with SETI proposals is that there is an extremely high probability that these expensive experiments will tell us absolutely nothing. If a signal is received, well and good; but what if nothing is detected? Does that mean there is nobody out there, or that we are listening on the wrong frequency or at the wrong time, or with the wrong equipment altogether? Beings out there might have better things to do than send out signals for centuries in the silly hope that someone might listen. I have posed these, and similar questions to SETI enthusiasts, but have never had a reply. I firmly believe that the proponents of SETI should give serious thought to the possibility of failing to detect a signal, and the meaning of such a failure, before an expensive SETI project is funded. With von Neumann probes there is no such difficulty. One is always certain to get some useful information back from a successful probe. The main difficulty with the probe idea is that it involves technology in advance of ours, and therefore cannot be proved feasible. However, the great mathematician John von Neumann proved that a self-reproducing universal constructor is possible in principle -- that is why I have named the probes in his honour -- and computer scientists believe that such machines will be built within a century. Assuming that such machines are built once, they will then make copies of themselves, and must become cheap. So I have calculated the cost of a von Neumann probe on the basis of fuel costs. The price tag, in round terms, is [pound sign] 2000 million. This is the cost of exploring the entire Galaxy, yet it is within the means of many private organisations, let alone governments, today. An interstellar probe using our rocket technology would need 40 000 years before it reached the nearest stellar system and began to send back information. Is it reasonable to consider such a long-term project? I think it is. A group need maintain its interest in the project for only a few years; what happens after the probe is launched will not affect the exploration/ colonisation of the Galaxy, and a single successful probe launched by any species anywhere in the galaxy makes this exploration/colonisation inevitable. People may be motivated by an idealistic vision of galactic exploration, or by a desire to spread their own image throughout the Galaxy. Either way, any society would be likely to have people who would be attracted to such a project even if it would not be completed until long after they were dead. Even SETI proposals assume that such enthusiasts exist. These proposals require that somewhere in the Galaxy there is a society willing to broadcast signals for thousands or millions of years before receiving a reply. This is, if anything, less plausible than the idea that a group could hold together for the few years necessary to build and launch a von Neumann probe. Even using our primitive rocket technology it would take only 300 million years to cover the entire Galaxy with such probes, and this is such a short time compared with the age of our Galaxy of 10 thousand million years that I conclude that if intelligent beings existed their probes would be here. Because they are not here, no such beings exist. This is a bare outline of my argument against the existence of extraterrestrial intelligent life. I have presented a more detailed analysis in a series of papers published in the Quarterly Journal of the Royal Astronomical Society, and I have challenged Carl Sagan, the most well-known believer in ETI, to a ``letter debate'' on this question. Such a debate consists of an exchange of letters between two opponents, with the letters being published after a year or so of exchange. Professor Sagan has yet to respond to my challenge. I hope he will debate. Then each reader would have a chance to decide for himself or herself if we are really alone in the Universe.
Return to the ground floor of this tower
Return to the Main Courtyard
Return to Fort Freedom's home page