Hello All, The following is a paper I did for school. The subject (and Title) is The Case for Extraterrestrial Intelligence. I would be most grateful if some of you would read and critique it for me. Please leave me a message, good or bad. Thanx, Kev The Case for Extraterrestrial Intelligence Kevin D. Bryan I allowed Priscilla, our house cat, in off the porch this morning. As she scurried by my bare feet I swear I heard her meow "Thanks!" I stood there with the door open for just a second and blinked my half-open eyes. The cold air roused me quickly, and as I closed the door I shook my head and smiled at my fleeting fantasy. What I heard was a cat's meow, nothing more. Priscilla, like all animals worldwide, lacks the required degree of intelli- gence to communicate profound concepts, or utter a simple word like "thanks." Humans alone have this level of intellect. But what about elsewhere? Are there other places with creatures that have intelligence? Are we the only beings in the universe to gaze at the stars and ask these questions? It's a simple question that requires an involved answer. Searching for a solution involves examining issues in astronomy, biology, chemis- try, physics, and the social sciences. Even after much educated speculation, there is still no solid basis to answer absolutely one way or the other. However, we can come to certain conclusions. We can approach the answer in finer and finer increments. We have acquired enough data from many different sources to make an intelligent guess. Such speculation has a long history. In 1543, Nicolaus Copernicus, a Polish Astronomer, published a book that set forth evidence that the earth and other planets revolve around the sun. This conflicted with the widely held theological belief of the time: The earth was the immovable center of the universe and all things, including the sun, re- volved around it. The "Copernican System" provided a foundation for later achievements by Johann Kepler, Galileo, and Isaac Newton.1 This theory led to the inescapable conclusion that the earth was just one planet among many. In fact, later observations determined that earth was only a minor planet when compared with behemoths like Jupiter. Discoveries began to accumulate pointing to a universe that held Earth in no prominent distinction. Not only is the earth a minor to average planet, but we were further humbled by the discovery that our sun was only an average star among billions of others. Many have speculated about life, or even intelligence on other planets. Why shouldn't similar conditions arise elsewhere if Earth is so normal? This has been called the "Mediocrity Principle."2 Many alien cultures or evidence of them have been sighted since the invention of the telescope. There have been highly publicized accounts of extended observations of a moon civilization. And of course there is the famous observations of Martian canals by Percival Lowell. Many have speculated that if there is intelligence in space, maybe it has visited the earth before. Many think we are regularly visited even now. This is the feeling of many UFO enthusiasts. There is no shortage of reports of sightings and encounters with alien visitors from outer space, benevolent and otherwise. However, once all the unusual atmospheric conditions, hoaxes, and misunderstandings are filtered out, there is not much left that's tangible. On the opposite extreme there lies the creationists who sight the Bible as the ultimate source. Their premise is that if God created man in His own image then there is no room for other intelligent life forms. What's more, on the third day of cre- ation, "God said let there be lights in the expanse of the heavens . . . and let them be for signs and tokens and to mark seasons, days, and years" (Genesis 1:14). Obviously if God had created the stars and planets for man's benefit alone then He would not have placed other souls there. Most mainstream theolo- gians agree with evolution, however, and recognize certain biblical stories as legend or parable. Both of these points are complicated and controversial. To do proper justice to either position would require more space than is available here. Suffice it to say that neither of these sentiments are based upon scientific method. That is, they are theories not based upon verifiable, repeatable observations and evidence from many neutral sources. Therefore these opinions lie outside the scope of this article. There are many scientists searching for evidence of alien cultures now. So many astronomers are convinced of the probability of extraterrestrial life that there are roughly one dozen different searches going on all over the world. Most are using radio telescopes to ply the heavens for faint telltale artificial transmissions. This search is called "Search for Extraterrestrial Intelligence," or more commonly: SETI. Additionally, gold-anodized signs were placed on the recent Pioneer and Voyager probes. These spacecraft are the first man-made objects to escape the gravitational influence of the sun and travel outside the solar system. As this is written, they have all passed the furthest planet and are speeding toward the stars. It will be many thousands of years before any of them pass close to another star. The plaques are "very much like a ship- wrecked sailor casting a bottled message into the ocean,"3 and represent a meager degree of the seriousness this subject has taken among some scientists. Why go to all the trouble? What reason do astronomers have for spending millions of dollars on a project with no guarantee of success? Is there reason to believe there is someone else out there? Attempting to answer that question will require a little background to get to a solid base. Before we start let's define what we mean by "life." We are talking about carbon-based, self-replicating life like that found on Earth. Indeed, it is the only life we know of anywhere. This life requires a nearby sun to supply the energy for the chemical processes associated with life and liquid water as the proper medium for these reactions to do their slow, gentle work. When we speak of sun-like stars or earth-like planets, we are speaking of places where the proper factors exist to enable earth-like life to commence. We recognize from the outset that such life will likely not resemble earth life superficially. There is so much opportu- nity for variation, even in the most basic of carbon-based molecules, that from the beginning such life would be very different from earth-life. Yet it would still be carbon based and dependent upon liquid water. What we are not talking about is the possibility of silicon-based monsters that breathe helium on a pink dappled world orbiting a white dwarf. These or equally bizarre life-forms may exist. However, we have no examples of such life and there- fore it is useless to speculate on its existence. There is more than enough reason for speculation based upon what we do know. Nearly three decades ago, Cornell Univers- ity's Frank Drake was among the first to consider the possibility for extraterrestrial intelligence from a realistic perspective. He formulated the now famous "Drake Equation." His equation was soon accepted by many astronomers as the most organized way of looking at the intricacies involved with other sentient races. Today it is still routinely refereed to in magazine articles and books on the subject. The Drake Equation expresses the number, N, of advanced civilizations that may exist now in our galaxy; it takes into account known facts about the universe and combines them with educated speculation from many fields. As new discoveries are made, the equation allows scientists to plug in different vari- ables and analyze the possibilities. Here is a variation of the Drake Equation: N = N* x fp x fg x fe x fl x fi x ft x fL where N* = the number of stars in our galaxy, fp = fraction of stars that have planetary systems, fg = fraction of those stars that are sufficiently sun-like to support life, fe = number of planets in a given system that are ecologically suited for life (Earth-like planets), fl = fraction of those planets where life begins, fi = fraction of life-bearing planets that produce intelligence, ft = fraction of intelligent planets that develop a technological, communicative civilization, fL = fraction of a planetary lifetime that has a technological civilization, With this formula, scientists can get a ballpark figure for the number of alien civilizations that are able to communicate with us. The best way to arrive at that number is to go through the equation, part by part. A galaxy is an oasis of luminous matter in the dark emptiness of the universe. The dictionary defines a galaxy as "Any very large system of stars, nebulae, or other celestial bodies."4 There are at least 100 billion galaxies, each with an average of 200 billion stars. That makes the figure for the sum total of all the stars in the universe a two followed by twenty two zeros! What is the likelihood that out of such extraordinary abundance only one star, our sun, should warm the only inhabited planet? Already before we begin, it would seem highly unlikely we are alone. Astronomers rarely speak of contacting alien cultures in distant galaxies. The expanses involved are far too great. The closest galaxy is 55,000 light-years away, and it is a very small satellite of our own galaxy. The closest "normal" galaxy, Androm- eda, is 2.2 million light-years distant. It has taken the image of Andromeda we see today, 2.2 million years to reach us. Thus we see Andromeda as it was 2.2 million years ago, or the way it was when our hominid ancestors were chipping the very first stone tools. The milky way galaxy, the galaxy that includes our own solar system, has about 300 to 350 billion stars. This makes it a little larger than average. So the first part of the equation is easy: N* = 300 billion stars. Notice that even if we consider The milky way exclusive- ly, we find we still have a substantial base with which to begin. However, just knowing the amount of stars in our galaxy is not enough. Life cannot arise on the surface of a star. For that we need a planet. So how many stars have planets? We have not observed any planets around other stars directly. The problem is that all the stars are so far away, the closest being Alpha Centauri, 4.3 light-years away. When we observe these stars, even with the most powerful telescopes, all we see are pinpoints of light. We cannot discern any disks at all. Therefore any dim object in the same vicinity of a star, that does not radiate its own light, is not observable. It would be like trying to see a moth circling a spotlight on a distant mountaintop; the glare would drown out the moth. So how can we tell if there are planets orbiting distant stars? We know that certain stars wobble slightly as they travel thorough space. The reason for this seems to be the gravitational influence of some unseen nearby neighbor. What's more, we per- ceive this wobble only with stars that are relatively close to us. It is reasonable to assume that far-off stars exhibit the same fluctuations but are too far away for us to see the phenom- enon. Another point: slight as these wobbles are it would take an object of some considerable mass to cause the effects we see, something about 8 to 10 times the size of our Jupiter. If we were looking back at our solar system from that far-away vantage point, our sun would not be sufficiently influenced by the gravitation of our planets to have a noticeable wobble. Moreover, in our solar system there seem to be more small objects than large ones, i.e. one star, nine planets; more small planets than gas giants; more moons than planets; more asteroids than moons etc. There even seems to be a tendency for "micro planetary systems" within our solar system. All the gas giants have multi- ple moons, the largest of which are larger then the smallest planets. Jupiter's Ganymede and Saturn's Titan are both bigger than Mercury and Pluto. Add to this the recent discoveries of planetary disks (orbiting clouds of debris that may eventually form into planets) around young stars, and we can conclude that there are many stars with planetary systems in orbit about them. Astronomers make this figure high, around 93%. Lets round it down to an even 90%, and apply it to our formula. 300 billion stars multiplied by 90% thus we have: N* x fp = 270 billion stars in our galaxy with planetary systems. How many of these planetary systems orbit sun-like stars? Astronomers group stars by their spectral class. They use the letter system: O, B, A, F, G, K, and M, where O represents the hottest stars and M the coolest. Our sun is spectral class G, making it a very common star. Of course the hotter stars are also the bigger stars, and as in most everything else in the universe, there are more small stars than big stars. Consequently, there are far more G- type (sun-like) stars than O-type. 93% of all stars are the smaller F-type and below. The larger stars consume their nuclear fuel much faster than the smaller stars. The average life span of a giant O-type star may only be 500,000 years. Our sun has been shining for 5 billion, and has another 6 or 7 billion left to go. Life first appeared on earth a billion years after forming and intelligence took another three billion. Assuming the earth is typical (medi- ocrity principle), the larger stars will not exist long enough for life to develop on an orbiting planet. What about smaller stars? They should last even longer than our sun, allowing them to harbor potential life-bearing planets for more than the time they need. Moreover there are more smaller K and M-type stars in our galaxy than our own G-type. This is true, but they have their own problems. A smaller star will of course also be dimmer and cooler. Therefore a planet would have to orbit closer to be warm enough to maintain life processes. However, an earth-sized planet would encounter higher tidal forces even though the gravitational pull would be weaker. If the tidal force was too great, the planet would never form. A planet orbiting the smallest M-type stars could not get close enough for warmth without first being torn apart by the tidal forces. A slightly larger star, say a large M-type or a small K- type, might allow a planet to form. Still, the tidal forces would probably slow the planet's rotation to the point where one side always faces the sun, much like our own moon always facing its near side to the earth. This would cause the day side to reach incredibly high temperatures and the night side to dip into very low temperatures. It would be very hard to sustain an atmosphere on such a world, let alone life. Life cannot exist on a planet that orbits too large a star. Large stars squander their nuclear fuel too fast, they will not last long enough for intelligence to arise. Also, life cannot exist orbiting too small a star. Tidal forces will be too great on a planet close enough to get the required warmth. About 25% of the stars in our galaxy are considered the proper size to be sufficiently sun-like to maintain life. So we can determine the third part of our equation by multiplying 270 billion stars by 25%, therefore: N* x fp x fg = 67.5 billion sun-like stars in our galaxy. However, life cannot form on just any planet. There may be no planets in the sun-like star's system which: a) are comprised of the proper raw materials for life, b) are the right distance from the star, c) have stable orbits or, d) are the right size. A planet must meet all these criteria before a it is classed as "earth-like." Since we know nothing of other planetary systems we can only speculate on the frequency of earth-like planets based upon our own solar system. Even though only one planet can be classed as earth-like in our system, there are sufficient near-misses to make things ineteresting. The first requirement for an earth-like planet is the proper raw materials for formation. Our sun is a "second genera- tion" star. That means it coalesced from a cloud that was itself the remnant of some very ancient supernova. The heavier elements that laced this cloud were created in the heart of the original "first generation" star. It was these heavy materials that formed into the inner planets including Earth. First generation stars have only hydrogen and helium left over after the star's formation. That means only gas giants would form too far from the star to allow a foothold for life. The core of our galaxy, as well as other galaxies, has almost no heavy elements. Therefore there will be no earth-like planets in the galactic core. An earth-like planet's distance from its sun is another consideration. Too far away and the planet is too cold for life, too close and it's too hot. The area around a star where the distance is just right for life is the "ecosphere." In our solar system we only have to look at Venus for an example of a planet too close. Venus is roughly the same size as earth with about the same raw materials. But it is just barely too close to the sun. The sun's heat did not allow liquid water to form on the surface. Instead, a thick atmosphere of carbon dioxide and sulfuric acid formed, causing a runaway greenhouse effect. The surface temperature is so hot that lead would run liquid, much too hot for life to start. On the other extreme we have Mars: too far from the sun, and therefore too cold for life. However there was a time when liquid water did flow on the Martian surface. We know this from photographs of erosion scars that look exactly like dry river beds. Mars' problem is further compounded by its small size. It is not large enough to hold onto an atmosphere thick enough to sustain liquid water for a sufficient time to allow life to form. However, the jury is not in yet on Mars. Despite the lack of life signs from experiments on the Viking landers, there is still speculation that some life exists, or at least fossils of dead life. The final earth-like requirement is orbital stability. A planet can be the proper size and comprised of the proper materi- als, but if it has an orbit that is too elliptical to keep it consistently in the ecosphere then life will not begin. Life- bearing planets require the consistent temperatures that only a stable, circular orbit can produce. So to summarize, for an earth-like planet to form there must be enough heavy elements available in the ecosphere to form an object large enough to hold an atmosphere and allow liquid water to condense on it's surface. How much chance for all this to happen? It happened one planet out of nine in our system. Who knows, if Mars had been a little larger or Venus a little farther away from the sun maybe we would have two planets with life. Some astronomers say nearly every solar system around sun-like stars will have an earth-like planet, others say almost none and that Earth is a fluke. Even if we aim for a conservative middle of the road this cuts down the number considerably. Only one out of forty sun-like stars have planets that meet all the criteria for an earth-like planet. So we now have: N* x fp x fg x fe = 1.65 billion earth-like planets in the galaxy. How many of these earth-like planets are likely to have life arise? Astronomers point to our own earth where the oldest fossil evidence of life is 3.5 billion years old. That's compar- atively soon after Earth cooled about 4.6 billion years ago. Also, we find many organic molecules in the most unlikely places, the cores of meteorites, and interstellar clouds. This is significant because organic molecules are the building blocks for more complicated substances essential to life. Perhaps even more significant is the laboratory experi- ments of Harold Clayton Urey and his student Stanley Lloyd Miller in 1952. They filled a sterile flask with gases and water that they theorized comprised Earth's primordial atmosphere and ocean. Then they subjected the contents to small electrical discharges to simulate lightning. Within a week they had brewed a mixture of amino acids, chemicals essential to the formation of proteins. To be sure, this was not life but it demonstrated the propensity for self-starting chemical processes in the direction of life. Perhaps life is inevitable under the right conditions. Lets be conservative and say one half of all earth-like planets get life. Thus: N* x fp x fg x fe x fl = 825 million life-bearing planets in our galaxy. However, a single-cellular creature cannot make its presence known across a gulf of light-years. That requires intelligence and technical knowledge. The most optimistic views have every life-bearing planet eventually spawning intelligence and a technological communica- tive culture. These notions ignore certain points that are covered later. So let's go middle of the road again and say 1 out of every 100 life-bearing planets attains intelligence and goes on to form a technological civilization. Therefore we can knock off two more variables in our equation: N* x fp x fg x fe x fl x fi x ft = 8.25 million worlds on which intelligence and technology are successful. Finally we must consider the average lifetime of a technological civilization. Some speculate that intelligence is outgrown by its own inventions and is destined to destroy itself after a short time. If this is the case then there would be very few other societies out there to talk to. Carl Sagan paints a grim picture about this possibility: . . . it is hardly out of the question that we might destroy ourselves tomorrow. Suppose this was the typical case. . . at any given time there would be only a tiny smattering, a handful, a pitiful few technical civilizations in the Galaxy . . . The number N might even be as small as 1. If civilizations tend to destroy themselves soon after reaching a technological phase, there might be no one for us to talk with but ourselves. And that we do but poorly. Civilizations would take billions of years of tortuous evolution to arise, and then snuff themselves out in an instant of unforgivable neglect.5 Perhaps the recent events in Eastern Europe are the first signs of a maturing in the Human Race and cause for a more optimistic view of the average life span of a technological civilization. Clearly a society need only survive until it has branched out into nearby space. Establishing permanent, self- sustaining colonies away from the home world, assure the survival of the race in some cosmic accident, global war or plague. Such a point may lie only 100 years in our future, surely within 200. Therefore, let's assume that most civilizations survive for millions of years and that nearly all of them are still out there. Let's put a very conservative figure of 25% to those extraterrestrial societies that do succumb to some disaster that results in their extinction. Therefore our final figure is: N* x fp x fg x fe x fl x fi x ft x fL = 6.1875 million extraterrestrial civilizations capable of radio communications over distances of light-years in our galaxy. Lets round it down to an even 6 million. This may sound like a large number but when compared to our original figure of 300 billion stars in the galaxy, it diminishes considerably. Only one out of every 10,000 stars in the galactic rim shines down on a planet that has a technical, communicative civilization. Galactic cores lack heavy elements and therefore do not have the raw materials to form earth-like planets. So these societies will only exist around the galactic rim. Our Galaxy is a disk shaped volume of stars roughly 100,000 light-years across with an average of 7.6 light-years between stars in the rim. So if we assume a more or less even dispersal of societies we can calculate the probable ballpark distance to our nearest neighbor. This comes to about 164 light-years distance between societies. This distance does not seem that great. What are the chances of travelling to our nearest stellar neighbors? It would seem that interstellar travel is very difficult. At 186,000 miles per second it still takes light from Proxima Centauri (our nearest star) 4.3 years to reach us. The fastest object launched from Earth, Voyager 2, is speeding away from us at 42,250 miles an hour. At that velocity it would take nearly 100,000 years to travel just to the nearest star. And of course Alpha Centauri is not a favorite candidate for a sentient race. We have just calculated the most likely distance to be 164 light- years. In addition, even if we were to attempt to send something that far, in what direction should we aim? What about faster-than-light travel? It was thought at various times that certain velocities were impossible to exceed. We have surpassed the ten-day transatlantic crossing, the sound barrier, even the four minute mile. Surely the speed of light is similar and we will eventually surpass even that, given advanced enough technology. Alas, this seems not to be the case. Faster-than-light travel, at least in our three-dimensional space, is indeed impossible. Einstein's theories of relativity ascertain that the only explanations for certain perplexing astronomical observa- tions is a universal speed limit of 186,000 miles per second, the speed of light. Later experiments on gravitational light refrac- tion and particle acceleration have supported Einstein's theories quite well. Thus it is likely we will never invent Star Trek style "warp" drives, and travel between the stars will never be conve- nient. After all, if there are a large number of sentient civili- zations on other worlds, presumably more advanced than us, then it follows that they may have mastered faster-then-light travel. But if that is the case then where are they? Surely they would have visited us by now. The lack of faster-than-light speed only makes interstel- lar travel inconvenient, not impossible. Perhaps a civilization could build "arks" in which generations of inhabitants would live out their lives in transit. There is nothing theoretically impossible to overcome about such an idea. These large "worldle- ts" would lumber among the stars going perhaps as fast as one tenth light speed. This is bad news for proponents of the possi- bility of extraterrestrial intelligence. Why is the possibility of generation arks bad news? It would seem that such a proposition would be great news. Dr. David Brin writes, "The possibility of starships places a new and awesome burden on xenology [the study of extraterrestrial life]. It presents us with a paradox that is very difficult to over- come."6 The problem with starships is that they provide a mecha- nism by which a race could colonize all habitable planets in The Milky Way within sixty million years. In all the six million civilizations we calculate to be out there why hasn't one colo- nized Earth in the past? Even if none have come here, "why have we picked up no radio signals, when the stars should be humming with information and commerce? Where are they?"7 Contact optimists try to explain this quandary in many ways. They suggest that truly advanced races would have perfected zero population growth and therefore would lose a prime motiva- tion for interstellar travel. Furthermore, if they have been successful at increasing their own life spans then perhaps they would favor a very conservative, risk-free life and would stay secure and safe in their home system. Perhaps there is a plausible faster-than-light technique. Astrophysicists theorize about travel from one spot in our space to another by travelling through fourth dimensional space or "geometrodynamic" travel.8 Fourth dimensional mathematics is a routine, though theoretical form of higher math. Maybe the entrance into "trans-dimensional space" is via black holes. If so, then star travelling cultures would tend to congregate around these openings. Since our solar system is not near any black holes, no one would have a reason to visit our vicinity of the galaxy. Also, ark-type star travel might then diminish. All the points against the possibility of interstellar travel may prove to be compelling, and the obstacles too large to surmount. Yet, there does not have to be actual travel between stars to communicate. As we have mentioned earlier there is radio. It turns out that radio waves (and most other parts of the electromagnetic spectrum) are easy to produce and easy to receive despite their low energy consumptions. It is this low energy requirement that makes radio so ideal for interstellar communication. If we were to initiate a radio conversation with our nearest potential neighbor, it would be 328 years before we received a response. Electromagnetic evidence of our own existence, old broadcasts of "I Love Lucy" and LORAN transmissions, is a steadi- ly expanding sphere scarcely 100 lights-years across. So we are not yet known by the closest societies. It is ironic to think the first impressions of humanity will be sitcoms or the signals of a warlike race. However, we are probably the most recent civilization to achieve the required sophistication to have radio. Any younger societies probably are still in the alien equivalent of the stone age. Likewise any radio-capable civilizations have had that ability for hundreds, perhaps thousands of years. So it makes more sense to listen for evidence of their existence then to send our own signals. Where do we aim our radio telescopes? In a sphere with a radius of 164 light-years with earth at the center, there are literally hundreds of candidates. We have been listening for about fifteen years with no success, but we have only spent one- tenth of one percent of the resources needed for a truly realis- tic seaach.9 That is not the only problem. The electromagnetic spec- trum is very wide. It encompasses a broad array of frequencies. Where do we tune our radio receivers? On what frequency would a distant civilization use to broadcast its messages? The substan- tial amount of natural background radio noise emanating from the universe complicates this problem. Do we listen for intelligence in a naturally occurring quiet spot? Or do we pick a frequency that is very common all over the universe? There are numerous plans on the drawing board that would step up the search and cover the cosmos with a thoroughness never before possible. Radio technology has improved to the point where we can monitor many frequencies at the same time. Perhaps a new technology is just around the corner that would render radio obsolete. If so the older races would have discovered it and would be using it routinely among themselves. They might abandon radio altogether. This is doubtful because they would want to keep radio lines of communication open as a service to emerging radio cultures such as ourselves. There are other reasons we may not have heard from anybody yet. It may be that we are quarantined. Reasons for this may be that we are deliberately avoided to maintain our innocence. If we are one of the youngest cultures in the galaxy then the tendency would be for us to absorb and not to contribute, at least at first. What could we offer to a galactic federation of various cultures if we did not experiment on our own and perhaps make new discoveries from our unique "human" perspective. Primitive cultures tend to decline when they come in sudden contact with more advanced societies. There are many examples of this in our own history. At some predetermined point, when we could "add richness to galactic culture,"10 we would be welcomed into the "club" with open arms (or perhaps open tentacles). Even with the various excuses for the difficulty of star travel, the vastness of a radio search, and other reasons for deliberate avoidance, we must face the possibility that we may have overestimated some of the variables in the Drake Equation. Perhaps we should amend the tally of extraterrestrial civiliza- tions in the galaxy. Maybe we truly are unique having just missed some obscure catalyst for life or intelligence in our conjec- tures. But the "Mediocrity Principle" is a strong point on the side of alien cultures. Lets see if we can arrive at a compromise between alien civilizations every 164 light-years, and the Milky Way with just humanity as its sole benefactor. Astronomers have been most confident that other societies exist in space. But notice that of the eight variables in the Drake Equation, only four have to do with astronomy. The others involve mostly biochemistry. Chemist Richard E. Dickerson has remarked, "It is one thing to propose scenarios for origin of life that might have been; it is another thing entirely to demonstrate that such scenarios are either possible or probable." 11 On these points the astronomers must bow to the biochemists, and for the most part the biochemists are more cautious about the possibility of extraterrestrial intelligence then astronomers. Some biochemists have a real problem with the current models of the formation of the earliest life. Noted biologist Harold Klein has remarked: The early steps in this process of chemical evolution [of life] are becoming fairly well understood, but the critical step in the formation of life, namely, the origin, the actual origin of a replicating system, is still very, very far away.12 New theories are appearing all the time. The recent discovery of a whole previously unknown ecosystem on the Pacific floor has fueled new speculation of life's origin. These commu- nities of organisms, including six-foot worms and eyeless, pale crabs, are totally independent of the solar energy upon which their surface-oriented counterparts rely so much. They flourish instead on the nutrient-rich geysers of hot water (called smok- ers) spurting up from volcanic vents on the ocean floor. Thus most biologists and biochemists accept the inevita- bility of simple life-forms under the proper conditions. Never- theless the two variables that have the biochemists most worried are fi and ft. They point out that it is nearly futile to attempt predictions of the possibility of intelligence and technology. We recognize "that evolution is unique and, in detail, nonrepea- table," 12 and also, "Natural selection does only one thing: it produces organisms better adapted to the local environment. It contains no built-in 'self-perfecting' principle that guarantees a particular outcome, such as intelligence."13 It seems that the jump from single-cellular life to intelligence may be much greater than that from a lifeless world to one that harbors life. Consider that 85% of the time that life has existed on earth it has existed in only the single-cell form. If we compressed the 4.5 billion years since the earth formed into a single year, then single cell organisms would first appear around March 20. The first multicellular creatures would appear around November 11. Also consider that the dinosaurs ruled the earth for 140 million years without the benefit of intelligence, December 12 through December 25. Whereas humans have only existed for 3.5 million, or since about four AM the morning of the 28th. We have only had fire for perhaps 300,000 years and written history for only the last five thousand, thirty five minutes and fifty eight seconds before midnight on December 31 respectively. Intelligence seems to have a very limited value to the survival of a species. Only in humans has it been a great asset, and it may never have occurred were it not for many unlikely and hard-to-predict circumstances. University of Illinois's Edward C. Olson makes a very plausible argument against routine alien intelligence. He embel- lishes the Drake Equation by breaking up fi into smaller steps. His equation within an equation takes into account many "major biological inventions" (or their alien equivalent) that he maintains are by no means assured, but are required for intelli- gence to occur. Included in these inventions are photosynthesis, multicellularity, land organisms, the extinction of the dino- saurs, angiosperms (flowering plants), and bipedalism. His most optimistic analysis puts intelligence occurring simultaneously only once out of every two galaxies (his worst prediction is one out of 20,000 galaxies). Other scientists would maintain that he is underestimat- ing the example of convergent evolution that has happened many times on this planet. In Asia the placental wolf evolved, while in Australia the marsupial wolf evolved. The common ancestor of these two creatures was a very primitive shrew-like mammal from the time of the dinosaurs. It was probably an egg layer, neither placental nor marsupial. Yet when Australia split from Asia some sixty five million years ago, the two creatures were free to evolve separately. The placental/marsupial split is just about the oldest split in the mammal class. The marsupials divided and subdivided to fill their own ecological niches free from the competition of their placental cousins who were likewise evolving on the Asian continent. The ancestors of the marsupial wolf found places as carnivores and gradually evolved wolf-like features such as canine teeth, snout, feet and even hunting techniques. The resemblance was so uncanny that the first white Australian settlers named the animal the tasmanian wolf. Yet this animal is more closely related to the kangaroo and the koala then the wolf family. There are many other examples of convergent evolution. Powered flight has risen independently four separate times. Birds, bats, insects, and the extinct flying reptiles (pterosau- rs), have all evolved flight individually. Eyes have evolved many times independently. We also have the case of whales and dolphins which are mammals that have returned to a sea life and have evolved very streamlined fishlike bodies. There is at least a fair chance that convergent intelligence would arise on some other world, as an analogous answer to similar problems, even if it takes a drastically different route. Accordingly, we shall revise our estimation of fi. Lets say one out of every 250 life-bearing planets produces intelli- gence. However, intelligence does not necessarily mean a tech- nology. One can imagine an intelligent species evolving in the depths of a watery world, perhaps with no solid land surface. But such a species would never see the stars and would therefore never contemplate life there. It undoubtedly would not have a technology like ours. Humanity did not succeed merely on intelligence. We had to have bipedal locomotion, something we shared with birds and some dinosaurs. We had to have grasping hands, like all the rest of the primates and some other animals. We needed good vision, also like the other primates and some birds. And finally, we needed a brain capable of the complexities of language along with the physical requirements of dexterous jaws and vocal cords. We needed all these things to succeed as a species the way we did. Would a slightly different evolutionary direction cause an alien intelligence with drastically different priorities? Maybe an affection for deep inward philosophy at the expense of outward exploration? In addition, there could evolve a land-based intelligence moving steadily in the direction of technology that stalls. This could happen for any number of reasons. Religious superstition could cause such a stagnation. Europe experienced a 1000 year stagnation during the dark ages due in part to religious super- stition. It's not hard to imagine something similar occurring on another world but for a much longer period of time. How many technological civilizations arise out of budding intelligence? Lets say one out of 100, just to be safe. This gives a new number for N: N = N* x fp x fg x fl x fi x ft x fL = 33,000 communicative civilizations in the Milky Way galaxy. That means one out every 1.8 million stars in the galactic rim shine down on a world with a technological culture. Thus the mean distance between stellar civilizations grows from 164 to 927 light-years. This new figure is more optimistic than Olsen's "one for every two galaxies" sum. Yet it is substantially less optimistic than the most hopeful speculations of "hundreds of millions" of cultures in our galaxy as stated by some astrono- mers. So is there extraterrestrial intelligence? Yes probably, but we just do not know for sure. Surely the pros are as strong as the cons. Why haven't we heard from them? There are many possible reasons, but mainly we have not searched very exten- sively yet. Remember there are thousands of possible candidates within 927 light-years. Why should we search for them? This question is perhaps one of those that if you have to ask, you will not understand the answer. But that is skirting the issue. First, it is not very expensive. With the world changing around us, military spending will begin to be cut back. Many groups will be clambering for the newly available funding. Perhaps we should consider earmarking a bit for SETI. Carl Sagan has always thought it would be worthwhile to begin a "serious, rigorous, systematic search," maintaining that "It is compara- tively inexpensive: the cost of a single naval vessel of inter- mediate size - a modern destroyer, say - would pay for a decade- long program in the search for extraterrestrial intelligence."14 Second, we would learn so much about the universe as an accidental consequence of a delicate, persistent search. Any more knowledge is good for its own sake. Third, even if we found no evidence of anyone else out there it would not be a loss. It would amplify the notion of the preciousness of ourselves as the "caretakers of the most fragile bloom in the universe."15 We would be perhaps less likely to risk this rare jewel of sentience in our trifling worldly quarrels. Finally, the discovery of artificial signals of extrater- restrial origin, even if we cannot decipher, would surely have a unifying effect on the human race. Issac Asimov writes: The mere thought of other civilizations advanced beyond our own, of a Galaxy full of such civilizations, can't help but emphasize the pettiness of our own quarrels and shame us into more serious attempts at cooperation.16 Imagine awakening one morning to the news that we discov- ered verified artificial radio signals overnight from some distant star. That day the way we looked at ourselves would surely change. It would be a momentous occasion. If we did decipher the message and sent one of our own, the nearly two thousand years we waited for an answer would be extraordinary for us. The generations that passed during that time would know that we are not alone and that we had initiated a dialogue. New philosophies would arise to include this wisdom and we would benefit without ever obtaining a response. But when the response finally does come and we join the "club," what wonderful marvels would commerce with other worlds bring to Mankind? What richness in science and the arts would be ours to share? The most cosmopolitan among us would instantly convert from thinking "I am a citizen of the World" and magnify by many orders of magnitude to proclaim, "I am a citizen of the Galaxy!" Endnotes (1) "Copernicus, Nicolaus." New Standard Encyclopedia. (Chicago: Standard Educational Corp. 1981 ed.). p. C-563a (2) Isaac Asimov, Extraterrestrial Civilizations (New York: Crown Publishers, Inc., 1979). p. 112. (3) Carl Sagan, The Cosmic Connection (Garden City, New York: Anchor Books, Anchor Press/Doubleday, 1973). p. 17. (4) Funk and Wagnalls Standard Desk Dictionary (New York: Funk and Wagnell, Inc., 1979). Vol. 1. p. 261. (5) Carl Sagan, Cosmos (New York: Random House, 1980). p. 301. (6) David Brin, Ph.D, "Xenology: The Science of Asking, 'Who's Out There?'". Analog Science Fiction/Science Fact, May 1983. p. 71. (7) Ibid. p. 72 (8) Ibid. p. 81 (9) Sagan, Cosmos. p. 302 (10) Brin. p. 80. (11) Edward C. Olson, "Intelligent Life in Space". Astronomy, July 1985. p. 9. (12) Ibid. p. 21. (13) Ibid. p. 22 (14) Sagan, Cosmos. p. 302. (15) Olsen. p. 22.