Are we reading too much of ourselves into this generalized cautionary fable? Perhaps, but I don’t believe there is strong evidence from hominid evolution on Earth to convince us one way or another, and as long as they might be there, then we have to try to find them.
The Interstellar Age
Sixty years ago a strange glowing object, unlike anything ever seen, suddenly appeared in the sky above Earth, scooting purposefully among the stars. A polished metal sphere twenty-two inches in diameter, with four spindly antennae, it circled our planet for three months. Sputnik 1 transmitted for three weeks, its simple, high-pitched beep, beep, beep causing delight and wonderment among those who had the right gear to receive it, and provoking awe, hope, and fear among everyone else. This portentous message from the sky, lacking content but rich with meaning, announced the arrival of the space age and heralded the rapidly approaching interstellar age of SETI.
This age started on September 19, 1959, when a persuasive paper appeared in Nature advocating for the feasibility of radio communication between the stars, and suggesting that humanity now possessed the tools to search for signals from alien civilizations. Radio telescopes, at the time, were a brand-new kind of instrument—born of wartime advances in radar technology. Astronomers were still figuring out what you could do with them when two Cornell University physicists, Giuseppe Cocconi and Philip Morrison, realized they could be used to communicate with planets orbiting distant stars.
Morrison came to SETI circuitously. Before he started speculating on the existence and longevity of other civilizations, he became intimate with the possible destruction of our own. A gifted nuclear physicist, he trained with J. Robert Oppenheimer and, in 1943 at the age of twenty-eight, was recruited, despite a huge FBI file on his youthful Communist activities, to join the Manhattan Project. Motivated by valid fear of a Nazi bomb, he made key contributions to the design and testing of the first nuclear weapons. He calculated how much plutonium was needed for a successful device, and designed the shape of the nuclear triggers. For the first atomic test, Trinity, Morrison rode from Los Alamos out to the test site in the backseat of a Dodge sedan alongside his plutonium bomb core, which he later described as “slightly warm, like a small cat.” He watched the blast at a distance of ten miles and was seared and stunned by its frightening heat. He helped assemble the bombs that would destroy both Hiroshima and Nagasaki, and helped load both on the planes that would drop them.
Shortly after the war, he visited Hiroshima. Shaken by what he saw there, he realized that nuclear weapons could trap humanity in a disastrous arms race. He wrote that “the public must realize that the bomb opened a door to fear, expense, and danger rather than just end the war,” and became a passionate lifelong activist for peace and nuclear disarmament. The Manhattan Project physicists knew they had unleashed a threat that could bring about the end of human civilization. Morrison was instrumental in organizing them into a powerful and authoritative brain trust for the disarmament movement.
I first met him thirty years later, when I was a young teenager and my parents socialized in the Boston academic scene with Philip and Phylis Morrison. They were an academic power couple in the nicest possible way: gentle, mega-erudite, and seemingly knowledgeable and curious about everything. As a kid, I encountered some adults who made scientists, teachers, and writers seem cooler than athletes and rock stars. This put ideas in my head. The Morrisons were definitely in this category. Another decade later, I reached out to Philip when I was working with a student disarmament group at Brown University. I was thrilled when he accepted my invitation to come speak in Providence. He was our big fish for the Brown University Conference on Nuclear Disarmament in April 1981.* We attracted a huge audience, and Morrison didn’t disappoint. He had a lifelong disability from contracting polio as a child, needing a leg brace, a cane, and eventually a wheelchair. He approached the dais slowly, hunched over his cane awkwardly, his gait lopsided and deliberate. He could barely see over the lectern, and as he bent the microphone downward, it creaked discordantly. Yet, as his soaring contralto voice and radiant intellect filled the hall, the auditorium quickly fell to a hush. He spoke directly to the students in the room: “I believe,” he began,
if we can solve the problem of maintaining the peace against the claims, the all-too-urgent claims of nuclear warfare, then I think we have a chance, an excellent chance, for solving the rest of those problems which you all know so well, the last generation or two has bequeathed you.
After World War II, Morrison had joined the faculty at Cornell, where his research interests veered into astrophysics, and he founded the field of gamma ray astronomy. He started to wonder if hyperenergetic gamma rays might be used by extraterrestrial civilizations to communicate across the galaxy. He and his Italian colleague Cocconi decided to look into it. In working out the physics, they became convinced that gamma rays would not work well for sending information, and that instead radio waves would be the preferred medium for interstellar greetings. Out of this came their landmark 1959 paper, which provided the theoretical basis for modern SETI.
In 1964, Morrison left Cornell for MIT, where he remained until his death in 2005. There he became known as a riveting lecturer on physics, biophysics, and astronomy, and a committed, energetic, and increasingly visible public communicator of science. He and Phylis Morrison, a gifted writer and educator, collaborated on books and radio and television shows.4 Throughout his storied career he maintained his involvement in both SETI and the disarmament movement. He was the nexus between these topics, having played key roles in the origins of both the atomic bomb and SETI, and he often connected the two, arguing that nuclear war, or a more general tendency toward technological self-destruction, might limit the lifetimes, and therefore the numbers, of civilizations in the galaxy.
The word seminal is used to describe many important papers, but when Cocconi and Morrison published their Nature paper “Searching for Interstellar Communications,” they planted a perfect seed into fertile ground. Three months later, on winter solstice 1959 (the day I was born), the cover of Life magazine carried a banner headline: “Target Venus: There May Be Life There!” As the 1960s began, voyages to the planets were imminent, and scientists were predicting that plant life would be found on Venus and Mars. The heady optimism of these times was reinforced when chlorophyll (the green stuff in green plants) was detected on the Red Planet, or so it was reported in Science magazine.* A 1961 National Academy of Sciences panel concluded that “the evidence taken as a whole is suggestive of life on Mars.” The news was also peppered with flying saucer reports. The beeping of Sputnik and its successors had made the concept of high-tech messages from above seem less fantastic. Space was wide open, and the world was ready. The SETI idea germinated and became rooted in the scientific consciousness, and soon sprouted into public visibility. Cocconi and Morrison presented the case so clearly, elegantly, and convincingly that, quite suddenly, the notion of exchanging messages with technically advanced alien civilizations was no longer an outlandish speculation. They somehow made it seem like a reasonable proposition by treating it as a physics problem, working out the equations and determining the size of telescopes, energy of transmitters, and sensitivity of receivers needed to succeed. They showed that even a young and relatively primitive scientific civilization, just like late twentieth-century humanity, would, in the course of investigating the physical universe, likely develop equipment that could easily be used to communicate across the interstellar void. Their paper concluded:
The reader may seek to consign these speculations wholly to the domain of science-fiction. We submit, rather, that the foregoing line of argument demonstrates that the presence of interstellar signals is entirely consistent with all we now know, and that if signals are present the means of detecting them is now at hand. Few will deny the profound importance, practical and philosophical, which the detection of interstellar communications would have. We therefore feel that a discriminating search for signals deserves a c
onsiderable effort. The probability of success is difficult to estimate; but if we never search the chance of success is zero.
Who could argue with that? The Cocconi and Morrison paper became the theoretical basis for an unprecedented kind of experiment that began a year later, in 1960, and continues to the present day. For all we know, it may just be getting under way. It is an experiment that a scientist can undertake only if she is comfortable with the idea that it may not succeed within her lifetime, if ever.
The Green Bank Dolphins
The time was ripe. In a stunning example of convergent intellectual evolution, a few hundred miles (or 0.001 light-seconds) to the south of Ithaca, New York, Frank Drake, a brave and gifted young radio astronomer, had independently produced the same calculations as Cocconi and Morrison, and reached the same conclusion. Not only did Drake determine that a radio search for alien messages had become possible, but he decided to do something about it.
In 1960, he began Project Ozma, aiming the eighty-five-foot dish of the National Radio Astronomy Observatory in Green Bank, West Virginia, toward two nearby Sun-like stars, Tau Ceti and Epsilon Eridani, tuning the frequency dial by hand to search one possible alien radio “station” at a time. Lo and behold, Drake immediately picked up a strong signal! Could it be that easy? No. The signal was coming from a radar installation—on Earth. The intelligence was military, not extraterrestrial. From April to July of that year, for six hours a day, Drake searched for a signal. Nothing turned up that was both artificial and extraterrestrial, but the era of experimental radio SETI had begun.
In 1961, Frank Drake hosted the first SETI conference at Green Bank. There were only eleven in attendance, including Philip Morrison; Carl Sagan; Melvin Calvin (who, during this conference, received a call awarding him a Nobel Prize!); astronomer Su-Shu Huang, who invented the notion of habitable zones around stars; and neuroscientist John Lilly. Swept up in optimism and camaraderie, the participants formed a whimsical organization called the Order of the Dolphin, after Lilly’s work toward communicating with these sleek, bright creatures who seemed to encourage our hope for conversing with other intelligent species. The presence of all these notables helped to establish SETI as an endeavor that reputable people could take seriously—or, as Sagan described it, they “crossed the ridicule barrier.” Maybe so, but one wonders why there are no published proceedings or photographs from this meeting.
In putting together the agenda, Drake wrote down all the different factors that must be considered in any attempt to estimate the number of broadcasting civilizations in the galaxy. How often are new stars born? What fraction of them have planets? What portion of these have suitable conditions for life? What fraction of suitable planets actually develop life, and on what portion of these does intelligence develop? What fraction of these develop the capacity and desire for interstellar communication? How long do they last?
Drake realized that these agenda topics could also be combined into one equation, with each question, each unknown probability, represented by a variable, and the output, N, representing the estimated number of civilizations in the Milky Way galaxy. Some of the variables were well known, such as R*, the formation rate of stars. Some were wild guesses, such as fi, the fraction of biospheres that would develop technological intelligence. One important variable, fp, the fraction of stars with planets, was a wild guess at the time and has since become a known, observed quantity. Each fractional probability was given a value between zero (no chance of occurring) and one (inevitability, 100 percent chance). This mathematical tool became known as the Drake equation. The formula was not meant to provide a single, definitive, correct answer for N, the number of civilizations, but to organize our collective thoughts and discussions. It is a “heuristic” equation, useful for thought experiments. It allows us to ask questions such as What if we assume that life always forms complex communicating societies on a planet after two billion years, but these last for only an average of five thousand years? How would this affect the total quantity of civilizations? We can plug in numbers and get answers for our hypothetical situations. As we slowly learn more about the universe, and replace wild estimates with observed constraints, the range of reasonable hypotheticals narrows down. The Drake equation serves as an evolving quantitative framework for our continuing assessment of the paths and outcomes of cosmic evolution. Or, as Frank Drake describes it, the point of his equation is “to organize our ignorance.” It has served this purpose brilliantly, and has become a ubiquitous, time-tested tool, the iconic encapsulation of our efforts to suss out the population density of thinking species in the galaxy.
Historically, others had made a similar calculation but had not connected it to the practical consideration of an actual search program. In chapter 1, I mention a pioneering meeting on climate change organized in 1952 by Harvard astronomer Harlow Shapley. There, Shapley discussed “The Abundance of Life Bearing Planets” and wrote out an equation that is nearly identical to the Drake equation.5 His calculation led him to conclude that
the life phenomenon is widespread and of cosmic significance. We are not alone. And we should admit, of course, that the animal, vegetable, or other organisms on other happier planets may have far “surpassed” the terrestrial forms. There is no reason whatever to presume that Homo sapiens, Apis mellifera and Corvus americanus* are the best that biochemistry and star shine can do.
Yet there was an essential difference between Shapley’s treatment in 1952 and Drake’s nine years later. Shapley stopped short of discussing complex or intelligent alien life as something we might ever actually observe. Perhaps in the early 1950s such a thought would still have seemed too outlandish even in such brave and forward-thinking company. In the intervening years, with the advancement of radio astronomy, SETI had become possible as an observational science. In Cocconi and Morrison’s theoretical framework and Drake’s calculations, these estimates made the leap from idle speculation to testable prediction.
At the Green Bank meeting, Drake encouraged the participants to come up with a consensus estimate for every factor in the equation. They estimated that half of all stars have planets (a little low, we now know) and that the average number of habitable planets orbiting each of these stars is between one and five (probably a little high). They figured the probability of life forming on one of these planets is 100 percent. This seems optimistic, but sixty years later, we still don’t have any empirical purchase on this number. As I’ve described, a high probability is (weakly) supported by the quickness with which life established itself on Earth. Then they made their most controversial assumptions: the percentage of biospheres where life, once established, will evolve to intelligence is also 100 percent, and of these, the fraction that will develop the technology and desire to communicate with radio telescopes is 10 percent. These estimates, reflecting the zeitgeist of those times, now seem wildly optimistic. Yet, of course, nobody knows. The point of SETI, after all, is to try to find out.
The Dolphins concluded it was definitely worth a look.
Russians
SETI was born as the Cold War was heating up. While the nuclear powers were aiming missiles at each other across the Bering Strait, devising strategies for mutual assured destruction, scientists on both sides were looking out into the galaxy and wondering about establishing friendly relations with other civilizations.
At the time of Green Bank, a growing community of Soviet scientists was becoming interested in SETI, thinking along nearly parallel lines as the Americans, but with a Russian twist. The idea of more advanced civilizations that should evolve from early industrial ones fit very well into a tradition of Russian thought going back at least to the early twentieth-century cosmists such as Fedorov, Tsiolkovsky, and Vernadsky, who all saw contemporary human civilization as a passing phase in cosmic evolution. They imagined that the Anthropocene (or the noösphere, as they called it) was something just getting under way on Earth and that it might one day extend beyond this planet and make contact with its counterp
arts.
Soviet scientists also tended to see the subject within the political/philosophical frame of Marxist dialectical materialism, in which human history is unfolding according to inevitable historical laws. It was only reasonable to suppose that if such laws existed they would, after the current epoch, produce more advanced stages of civilization, and that these same patterns would be playing out elsewhere in the universe. Many of the boldest and most visionary ideas about galactic civilizations and the far-future evolution of societies (or past evolution on planets that got the jump on us by millions or billions of years) have come from Russian scientists steeped in these philosophical traditions.
The Soviet counterpart to the Green Bank meeting, the First All-Union Conference on Extraterrestrial Civilizations and Interstellar Communication, was held in May 1964, at the Byurakan Astrophysical Observatory in Soviet Armenia. Perhaps less concerned about the “ridicule barrier” and any public threat to research funding in their more centralized scientific enterprise, the Soviet scientists were eager to publish their papers. So this is the first SETI meeting for which published proceedings exist.
The father of modern SETI in the USSR, the Soviet Frank Drake, was Ukrainian astrophysicist Iosif Shklovsky, from the Sternberg Astronomical Institute in Moscow. Shklovsky, already an eminent pioneer of Soviet radio astronomy, had been inspired by the Cocconi and Morrison Nature paper in 1960. When he turned his career toward the theoretical study of SETI, it started a vital and sustained tradition of important Eastern Bloc contributions to this field.
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