Coming of Age in the Milky Way - Timothy Ferris (2003)



Life, like a dome of many-colored glass, Stains the white radiance of Eternity.


A sad spectacle. If they be inhabited, what a scope for misery and folly. If they not be inhabited, what a waste of space.

—Thomas Carlyle

           The scientific developments we have been discussing in this book have worked, however inadvertently, to implicate and involve our species in the wider universe. Astronomy, in shattering the crystalline spheres that had been said to seal off the earth from the aethereal realms above the moon, placed us in the universe. Quantum physics cracked the metaphorical pane of glass that had been assumed to separate the detached observer from the observed world; we are, we found, unavoidably entangled in that which we study. Astrophysics, in determining that matter is the same everywhere and that it everywhere obeys the same rules, laid bare a cosmic unity that extends from nuclear fusion in stars to the chemistry of life. Darwinian evolution, in indicating that all species of earthly life are related and that all arose from ordinary matter, made it clear that there is no wall dividing us from our fellow creatures on Earth, or from the planet that gave us all life—that we are such stuff as worlds are made of.

The conviction that we are in some sense at one with the universe had of course been promulgated many times before, in other spheres of thought. Yahweh fashioned Adam out of dust; Heraclitus the Greek wrote that “all things are one;” Lao-tzu in China depicted man and nature alike as ruled by a single principle (“I call it the Tao”); and a belief in the unity of humankind with the cosmos was widespread among preliterate peoples, as evidenced by the Suquamish Indian chief Seattle, who declared on his deathbed that “all things are connected, like the blood which unites one family. It is all like one family, I tell you.” But there is something striking about the fact that the same general view has arisen from sciences that pride themselves on their clearheaded pursuit of objective, empirical fact. From the chromosome charts and fossil records that chart the interrelatedness of all living things on Earth to the similarity of the cosmic chemical abundance to that of terrestrial biota, we find indications that we really are a part of the universe at large.

This scientific verification of our involvement in the workings of the cosmos has of course many implications. One of them—the subject of this chapter—is that, if intelligent life has evolved on this planet, it may have also done so elsewhere.* Darwin’s theory of evolution, though it does not explain away the ancient conundrum of why there is such a thing as life, does make it clear that life may arise from ordinary matter and evolve into an “intelligent” form, at least on an Earthlike planet orbiting a sunlike star. As there are plenty of sunlike stars (over ten billion of them in the Milky Way galaxy alone), and, presumably, more than a few Earthlike planets, we can speculate that we are not the only species ever to have studied the universe and wondered about our role in it.

Our comprehension of the relationship between mind and the universe may depend upon whether we can make contact with another intelligent species with which to compare ourselves. Seldom has science done very well at studying phenomena of which but a single example was available: Newton’s and Einstein’s laws would have been far more difficult—perhaps impossible—to formulate had there been only one planet to test them against, and it is often said that the central problem of cosmology itself is that we have but a single universe to examine. (The discovery of cosmic evolution eases this difficulty, by proffering for our consideration the very different state of the universe during the first moments of cosmic evolution.) The question of extraterrestrial life, then, goes beyond such issues as whether we are alone in the universe or may look forward to cosmic companionship or need fear alien invasion; it is also a way of examining ourselves and our relationship to the rest of nature.

Though much here is new, recent interest in extraterrestrial life can be viewed as resulting from the latest upturn in the fortunes of materialism, the philosophical doctrine that events can be explained solely in terms of material interactions, without recourse to insubstantial conceptions such as that of spirit. Darwinism engendered a new respect for the potential of ordinary matter: A lump of mud in a puddle of rainwater begins to look quite magical, if one appreciates that its like once reared itself up into the whole panoply of earthly life, including that possessed by the individual who contemplates the mud. No longer could a thinking person, mindful that his or her ancestry stretches back through the mammals to the fishes to the amino acids and sugars of prebiotic matter, readily agree with Martin Luther that the earth is but “defiled and noxious,” or accept the verdict of the Christian Science service that “there is no life, truth, substance, nor intelligence in matter.”

Historically, materialists have been inclined to imagine that there is life on other worlds. Metrodorus the atomist wrote in the fourth century B.C. that “to consider the earth as the only populated world in infinite space is as absurd as to assert that in an entire field sown with millet only one grain will grow.”1 Five centuries later, Lucretius the Epicurean proposed that “there are infinite worlds both like and unlike this world of ours.”2 The Roman Catholic Church, convinced that humans are essentially immaterial spirits, felt threatened by the materialistic point of view: When Giordano Bruno, the Renaissance doyen of pop mysticism, asserted that matter “is in truth all nature and the mother of all living things,”3 and declared that God “is glorified not in one, but in countless suns; not in a single earth, but in a thousand, I say, in an infinity of worlds,”4 he was tied to an iron stake and burned alive, on February 19, 1600, in the Piazza Campo dei Fiori in Rome.

Nevertheless, as science ascended so did materialism, and with it the belief in a plurality of populated worlds. In England in 1638, a Protestant clergyman named John Wilkins published a book proposing that the moon was habitable. Descartes, whose theory of cosmic vortices foreshadowed aspects of Newton’s universal gravitation, wondered whether “elsewhere there exist innumerable other creatures of higher quality than ourselves.”5 But no writer did more to infuse the conception of a diverse, fertile universe with a sense of delight than the young French Cartesian Bernard de Fontenelle, whose Conversations on the Plurality of Worlds was published in 1686 and has enchanted readers ever since. The book takes the form of a dialogue between Fontenelle and a beautiful, unnamed countess with whom he walks in the gardens each evening at twilight, discussing the stars as they wink into view in the darkening sky. “Who can think long of the moon and stars, in the company of a pretty woman!” Fontenelle exclaims, but he soon gets down to business. “The earth swarms with inhabitants,” he tells the countess. “Why then should nature, which is fruitful to an excess here, be so very barren in the rest of the planets?”6 The moon, he thinks, may be inhabited, but he does not know by what sort of beings: “Put the case that we ourselves inhabited the moon, and were not men, but rational creatures; could we imagine, do you think, such fantastical people upon the earth, as mankind is?”7

The countess has her doubts: “You have made the world so large,” she says, “that I know not where I am, or what will become of me. … I protest it is dreadful.”

“Dreadful, Madam?” Fontenelle replies. “I think it very pleasant. When the heavens were a little blue arch, stuck with stars, I thought the universe was too strait and close, I was almost stifled for want of air. But now it is enlarged in height and breadth…. I begin to breathe with more freedom, and think the universe to be incomparably more magnificent than it was before.”8

Not until the latter half of the twentieth century did it become possible to actually begin searching for life on other worlds. One way to do this was to send spacecraft to other planets in the solar system. This endeavor began with the American Pioneer and Soviet Venera missions to Venus in the 1960s, and continued with unmanned American missions to Mars and the Jovian planets in the following decades. The results of these and other preliminary reconnaissances were negative: Photographs taken by unmanned Soviet landers turned up no trace of life on Venus, which has a thick atmosphere but is hotter than Dante’s hell, and two landers dispatched to the surface of Mars by the American Viking project recorded no obvious sign of Martian life, either. But these, of course, were insufficient grounds upon which to reach a conclusion about the prevalence of extraterrestrial life in general, since the solar system harbors fewer than one ten-billionth of the total number of planets estimated to exist in our galaxy alone.

One might search for life beyond the solar system by traveling to the stars, but to do so within any reasonable amount of time is a very tall order indeed. The stars are just too far away: A spacecraft capable of traveling a million miles per hour—and this would be a stunningly fast ship, one that could fly from Earth to Mars in less than two days—would take nearly three thousand years to reach Alpha Centauri, the nearest star. If the expeditionaries proceeded to the next promising star—Delta Pavonis, spectral class F8, would be a reasonable choice—and then hastened on to, say, Beta Hydri, and then kept going to Zeta Tucanae before stopping for a well-earned rest, they would have succeeded in visiting about one one-hundred billionth of the stars in the galaxy—a sample statistically less significant than attempting to understand all Shakespeare’s writings by examining only two letters from one of his sonnets. What is more, the trip would have taken over thirty thousand years, which is a very long time; thirty thousand years ago, our Paleolithic ancestors were carving the world’s first wooden drums.

There is, however, a better method of searching for intelligent life beyond the solar system. It is to employ radiotelescopes to listen for electromagnetic signals—radio or television transmissions—beamed into space by alien civilizations. Such a signal, transmitted using only a few cents’ worth of electricity, travels at the speed of light and could be intercepted by radiotelescopes on Earth across distances of many thousands of light-years. This was the realization behind what came to be called SETI—the search for extraterrestrial intelligence.

SETI was first proposed in 1959 by two scientists, Giuseppe Cocconi and Philip Morrison. “The probability of success is difficult to estimate,” they noted, “but if we never search, the chance of success is zero.”9 The first SETI experiment, Project Ozma, was conducted in the early 1970s by the American astronomer Frank Drake. Drake observed a total of 659 stars over a three-year period, listening at but a single frequency with radio dish antennae of 300 and 140 feet in diameter. He detected no artificial extraterrestrial signals, but was not disappointed, given that the total number of stars in the Milky Way is so large; even if there were, say, a thousand civilizations beaming signals our way at exactly the listened-for frequency, the odds against Project Ozma’s having detected one of them would have been nearly a million to one. When one factored in the many other uncertainties—guessing at the right frequency, allowing for Doppler shifts introduced by the motion of the sun and earth, and so forth—the chances became even slimmer. If SETI were to succeed, it would have to be a continuous, long-term endeavor.

In the meantime, however, the very existence of even a few modest SETI projects in the United States and the Soviet Union spurred fresh reaction against the extraterrestrial-life hypothesis. When NASA proposed spending two million dollars a year to divert a small amount of radiotelescope time to SETI, Senator William Proxmire of Wisconsin scotched the idea, bestowing upon it his “Golden Fleece” award for wasteful public spending and declaring that extraterrestrial civilizations, “even if they once existed, are now dead and gone.”10 Thus ridiculed, SETI had to proceed in fits and starts, and by the mid-1980s only a few thousand hours of listening time had been accumulated on major radiotelescopes.

The opponents to SETI marshaled two central arguments. One was probablistic in nature, and like many statistical arguments was dogged by confusion. The other, called Fermi’s question, raised important issues that, if they did not dismiss the SETI case, did hold interesting implications for its search strategy.

The probabilistic argument consisted of adding up all the conditions thought to have been necessary for intelligent life to have evolved on Earth, then calculating that it was highly unlikely that the same thing had happened elsewhere. Its proponents began with the size of the earth’s orbit—were the earth slightly closer to the sun all its water would boil, and were it slightly farther away all the water would freeze—and tallied all the twists and turns in evolutionary history thought to have led to the emergence of Homo sapiens. Were all these variables ascribed to chance (as both sides presumed they should be) the result was a vanishing small likelihood of intelligent life appearing anywhere. There are more than one million species of life on Earth today, the evolution of each of which is estimated to have involved perhaps a thousand unsuccessful mutations that led nowhere; the probability, therefore, that another planet has evolved a similar biology can be estimated at a thousand million to one. Allow for all the cultural and biological variables involved in the advent of human beings and their civilization, and the odds go up to perhaps 1015 or 1018 to one—a number that exceeds the likely total of all the planets in the galaxy. Therefore, went the argument, we are almost certainly alone.

This line of thought resembled the old argument from design, as succinctly summarized by Bertrand Russell: “You all know the argument from design: Everything in the world is made just so that we can manage to live in the world, and if the world was ever so little different, we could not manage to live in it. This is the argument from design.”11 The poverty of this argument is that one cannot reliably calculate the odds of a particular thing having happened unless one either understands the process—that is, can properly identify and quantify all the variables involved—or has an adequate experimental data base from which to draw phenomenological information about it. If, for instance, we want to predict how close an intercontinental ballistic missile will land to its intended target, we can calculate all the variables—the flight characteristics of the missile, the influences of environment on its navigational system, etc.—or we can test real missiles, as often as possible, in order to generate a data base about how they perform. In practice one does both, since both approaches may err. But when the question involves intelligent life arising on other planets, we can with confidence do neither, since we have only a rudimentary understanding of the variables involved, and none whatsoever regarding the statistics. To reason probabilities without them is to fall victim to the post hoc fallacy, by the lights of which almost every event may be calculated to be unique. If, for instance, we were to ask how likely it is for you to be reading this page at this moment, we might add up all the twists and turns of your life and mine, beginning with our births and running down through a billion variables to the circumstances in which I wrote these words and you read them, and conclude that the thing is so nearly impossible that it would almost certainly never have happened, anywhere in the universe. Yet here we are.

In fairness, though, sentience might, indeed, be but an improbable accident, in which case we humans with our poor little radiotelescopes represent the highest form of intelligence in the universe. A SETI project could never prove that this were so, but if it went on listening for many decades and found nothing, the implication surely would be that we have few if any cosmic compatriots. But until that happens, as Michelangelo used to say, permit me to doubt.

The other argument is credited to Fermi, who is said to have asked, at Los Alamos one day in the late 1940s, “Where are they?” His reasoning was that if technically advanced extraterrestrial civilizations are prevalent, some of them ought to be able to migrate to other star systems, colonizing new planets as they go; the colonists subsequently could launch additional interstellar missions, until virtually every star system in the galaxy was occupied. Yet they are not here. Therefore, they do not exist.

On the face of it, Fermi’s question is easy enough to answer: Advanced extraterrestrials are not here because, for one reason or another, they are not able or do not want to be here. Perhaps interstellar travel is too expensive and time-consuming an enterprise for them to bother making the trip to other stars, or at least to our star, a yellow dwarf in the galactic suburbs orbited by a small blue planet the atmosphere of which is contaminated by the notoriously poisonous gas oxygen. Or perhaps they know we are here, but scruple not to interfere with our development (the “zoo hypothesis”). One can think of many such explanations; the point is, as they say, that absence of evidence is not evidence of absence. Lobster exist on earth, but I can set a place at my dinner table and wait a very long time before a lobster will come in the front door and climb up onto my plate; it’s just not worth the lobster’s trouble.

Fermi’s question, however, returns with far greater force when applied to the question of whether the solar system has been visited, not by a gigantic ark full of intrepid aliens, but by an automated, instrumented, self-replicating probe. Suppose that a nonhuman society were to send ten such machines to ten stars, and that each, upon arrival, were to mine an asteroid or planet in the system for materials and fuel from which to construct and dispatch ten more probes, while itself staying behind to keep an eye on things. In this fashion it would be possible for an advanced civilization to establish a remote-sensing presence in many star systems. If, for instance, the average time required for a probe to reach a new star, replicate, and send forth ten new probes were ten thousand years, there would be probes in orbit around half the stars in the galaxy within one hundred thousand years after the project began. The galaxy is more than ten billion years old, so presumably there has been plenty of time for someone to have tried such a thing. The cost is manageable, the return in data enormous. So where are the probes?

One obvious answer is that they may already be here. The first rule of interstellar space-flight is to make everything as light as possible, in order to save fuel. Consequently we would expect a probe dispatched to the solar system from another star to be small. How small? A study conducted at NASA’s Jet Propulsion Laboratory in 1980 concluded that an interstellar spacecraft with sensing devices and an antenna capable of calling home could be encapsulated, using near-future technology, in a package weighing less than three hundred pounds. The example of the human brain suggests that it should be possible to miniaturize considerable sensory and data-processing power into an even smaller package, perhaps the size of a grapefruit and weighing only a few pounds. A probe that small could be in orbit around the sun right now—adrift in space or sitting on one of the millions of asteroids orbiting the sun or on a satellite of Mars, or Jupiter, or Saturn, quietly watching and transmitting its findings back home—and we would not know it. We have as yet no means of detecting such a probe, unless it had been programmed to make itself conspicuous, and there are good reasons for it not to call attention to itself, the foremost among which is that if we discovered its presence we might very well go get it and take it apart. The further exploration of the solar system might, therefore, eventually turn up evidence of intelligent extraterrestrial life. This of course was the thesis of Arthur C. Clarke’s science fiction tale 2001, in which an astronaut investigates an alien probe discovered in orbit around Jupiter, the sun’s largest planet.

The possibility of automation also raises an intriguing prospect with regard to the search for intelligent interstellar radio signals: It suggests that the first signal acquired by a SETI receiver might very well have been dispatched, not by the inhabitants of another planet, but by an intelligent machine. To see how this could be so, we need only to consider the practical exigencies that an advanced civilization would encounter once it had been in the interstellar communications business for a while.

Suppose that yours is one of among a hundred and one worlds in the Milky Way galaxy that have established radio communication with one another. You now have a minimum of one hundred antennae in action, each maintaining contact with a different planet thousands of light-years away. This arrangement has two drawbacks. First, it is inefficient; for the sake of economy, you would prefer to be using as few antennae as possible. Second, far more serious, is the Q and A time; if you ask a question it takes thousands of years to get an answer.

The way to alleviate both problems is to network the system. You install a single, automated station in space to handle all the radio traffic, and you link it to your planet via a single antenna system. Getting out your galactic map, you then determine strategic locations for siting other such automated stations, and you transmit an appeal to the worlds located at those junctures to please build them. Soon—meaning in a matter of a few dozen millennia or so —everybody is sending and receiving data to and from all the other worlds through local junction terminals, which may be in their own star system or in one next door. This way they need not employ separate antennae for each planet with which they communicate, any more than Earthlings maintain a separate telephone for every person they call.

The network, once established, could be endowed with a number of salutary features. For one thing, it could be assigned the task of acquiring signals from new worlds and bringing them on-line. Indeed, its stations might broadcast acquisition signals for the purpose of attracting the attention of such relatively undeveloped planets. If so, the first signal intercepted by a SETI radiotelescope might come from an automated station sited far from any inhabited planet. In order to accomplish this and other tasks efficiently, the network should be made capable not only of repairing itself but also of expanding as the growing body of data requires. Here the technology of the self-replicating probes comes in handy; the network could dispatch probes to strategically favorable star systems in the galaxy, where each would build itself into a new junction station that would in turn hook up with the rest of the network.

Most important, the network should be equipped with a commodious and self-expanding memory, one that is replicated and regularly updated at every station. The great advantage of this is that it alleviates the Q and A problem. What one wants from interstellar communication is not really conversation, which takes too long, but information: One wants to know who else lives in the galaxy, what they look like and how they think and what they do, and about their history and that of the species that preceded them. To make this and all other information available to everyone interested, one should have the network remember everything that it conveys.

The network, then, would be not only a telephone or television system, but also a computer and a library, access to which would be as near as the nearest junction. If a species of intelligent birds on one side of the galaxy were interested in the biology of a species of intelligent reptiles on the opposite side of the galaxy, they would not have to send a direct message and wait two hundred thousand years for a reply. Instead, the information would already be stored in the memory banks of the network itself, and the requisite Q and A time would be little longer than the light travel time to and from the nearest network junction. Nor would the information be hostage to the fate of any particular world; once submitted to the network, it could survive indefinitely.

Direct radio communication between intelligent species would be relatively slow and inefficient. Here, eight inhabited worlds scattered around the galaxy are communicating directly. The average Q&A time is one hundred thousand years.

Networking of interstellar communication greatly improves the efficiency of the system. This rudimentary network, consisting of only four junctions, cuts the Q&A time (for communication with the terminals’ memory banks) in half, to fifty thousand years. By adding more junction stations to the network, the Q&A time can be reduced to a century or less.

We arrive, then, at the prospect of an immortal system, constantly expanding and continually acquiring and storing information from all the worlds that choose to subscribe to it. In the long run, the network itself might reasonably be expected to evolve into the single most knowledgeable entity in the galaxy. It alone could survey the full sweep of galactic history and experience the development of knowledge on a panstellar scale. Growing in sophistication and complexity with the passage of aeons, forever articulating itself among the stars, the network would come to resemble nothing so much as the central nervous system of the Milky Way.

Which, perhaps, is the ultimate purpose of intelligence, if life and intelligence may be said to have a purpose. We often find that our deepest yearnings have less to do with ourselves than with the wider scheme of things. (Love, which makes the world go round, is a highly individual experience, but its ultimate function is to perpetuate and advance the species.) Perhaps this is true as well of our deep but seemingly inexplicable desire to learn whether we are alone in the galaxy. Life might be the galaxy’s way of evolving a brain.

The process could extend beyond the galaxy, too, through contact with similar networks in other galaxies. Intergalactic Q and A times go to many millions of years—too long a wait for mortal beings, even if they are as longevous as Joshua trees, but perfectly manageable for an interstellar network. The network could afford to fashion giant antennae, use them to broadcast powerful acquisition signals to the Andromeda galaxy, to Centaurus A, even to the populous heart of the Virgo Supercluster, sixty million light-years distant, and then wait for a reply. Every world on every network would stand to benefit as galaxy after galaxy established contact, spinning electromagnetic threads across the expanding universe and exchanging the wealth of galactic libraries. The human species is only about two million years old, a time equal to that required for a message to travel one-way from the Andromeda galaxy to ours; we cannot very well expect to start up a meaningful dialogue with a society in Andromeda. But if information about Andromeda and the history of its worlds were already stored in our galaxy’s network, we might be able to begin accessing it within a matter of decades after making contact.

All this may be a dream. Certainly it is no more than a conjecture, and a materialist’s conjecture at that; what could be more materialistic than a galactic “intelligence” composed of communicating computers that rear themselves up out of the ash-gray rocks of dead asteroids? Yet it points to an idealistic vision of worlds by the thousands, some in their youth and some in their graves, linked by an intergalactic mechanism devoted to pure thought. And, it suggests a cosmic role for intelligence—that the combination of intelligence and technology could awaken the universe to its own life and thought and history. That would make us all the substance of a cosmic mind.

*I will not dwell on the self-flattery we exhibit in describing ourselves as “intelligent,” or on the enormous variations that might be embraced by the term when it is applied in a panstellar context. For the purposes of this discussion, “intelligent” creatures are defined merely as those with the means and inclination to engage in interstellar communication via electromagnetic (“radio”) waves.