So where are they? The problem Fermi identified seems compounded now by the “Great Silence,” the fact that in nearly sixty years of searching for radio signals or optical laser signals, we have not really detected anything promising.
Many answers have been suggested.16 Here I’ll summarize a few:
Fermi Answer 1: They are out there in abundance, but our assumptions about how to find them are wrong.
In 1959, Cocconi and Morrison made such a convincing case for radio SETI that it still dominates the way we think about detecting or contacting our sentient counterparts out there in the beyond. But it’s possible that the aliens don’t read Nature magazine, and never got the memo that this is the way to do it. Radio SETI presupposes that they are more advanced than we are, but not so much more advanced that they have abandoned radio in favor of some other communication technology that we have not yet invented or imagined. Maybe for a mature civilization using radio to communicate between the stars would be like you and I putting messages in a bottle to reach across the ocean when we could just make a phone call.
Fermi Answer 2: They have no interest in us.
The Great Silence may be neither. We imagine ET civilizations as a slightly more advanced version of ourselves, and picture establishing a common language and exchanging information, as if they will be curious about us beyond a level of zoology. There is a lot of frail human ego wrapped up in this rational fantasy. How could it be that our star kin won’t want to talk to us? Won’t they be proud of us and our wonderful equations and symphonies? Of course they will think we are exceptional and be excited to share technological information with us. Yet what if they couldn’t care less? What if our most sophisticated messages seem to them like the cute preverbal babbling of a baby? Even in the face of the solid quantitative conclusion that they will be incredibly advanced beyond our imaginations, we cling to this idea that they are going to be interested in talking to us more or less as equals, not as pets or specimens or curiosities, but as electromagnetic pen pals. This may make as much sense to them as it would for you to discuss philosophy with a frog.
Many have speculated that advanced civilizations may in fact not be living organisms but machines. Perhaps, as Arthur C. Clarke put it, “We’re in an early stage in the evolution of intelligence, but a late stage in the evolution of life. Real intelligence won’t be living.” This is but one in a universe of possible aliens that are much more different from us than we can imagine. Of course, even if they are far beyond us, they might decide to stoop down to our level to say hello, or probe us with primitive radio the way we might dose a laboratory insect with some pheromone, as a means to get our attention. But what if they’re just not that into us?
Fermi Answer 3: The Zoo hypothesis
It’s possible that other civilizations exist but for some reason are shielding us from knowledge of their existence. Maybe they’ve decided to leave us alone, perhaps for our own good. They could be protecting young civilizations like ours from some harm or shock or other effects of contact that they deem inappropriate, similar to Star Trek’s “prime directive,” which prohibits spacecraft crews from any interference in the development of local cultures, and specifically forbids alerting them to the fact that there are other, space-faring civilizations.
In 1897, H. G. Wells was inspired by the dismal history of European contact with native Tasmanians (none of whom survived) to write War of the Worlds, the archetype of a certain kind of unhappy extraterrestrial contact story. We know what happens when the guys with the fancy machines show up. It’s often the beginning of the end. Perhaps those who have explored the galaxy thoroughly have experience with this kind of thing, and they know that it is better for us not to know about them.17 Maybe advanced aliens maintain radio silence specifically because they know that primitive societies like ours are likely to conduct radio searches. Maybe they’ve decided that it is best that we not learn of their existence. Have we been wrapped for our own protection in something that filters out signals from interstellar space? An intelligent cosmos might prefer to mimic one devoid of consciousness for the benefit of primitives like us.
Fermi Answer 4: There is really nobody out there. We are alone.
It is certainly possible that there are simply no other civilizations out there. Maybe advanced technology always leads to a quick accidental suicide. Or we could be the most advanced in all the galaxy, the first to build radios and start listening. If you imagine evolution unfolding on somewhat similar tracks on worlds around different stars, sometimes taking a longer or shorter path to the stage of interstellar communication or travel, then somebody has to be the first, and for them it will seem like a quiet, lonely cosmos. This solution requires that Earth be special in an almost biblical way that seems inconsistent with the ridiculous profusion of planets where evolution could run its course.
The astrophysicist most identified with this point of view has been Michael Hart, whose papers in the 1970s and ’80s were so influential that you sometimes hear reference to the “Fermi-Hart paradox.” The galaxy is observably empty of other technological species, he claimed, because if they existed, then Earth should long ago have been visited or colonized. The lack of alien visitors and the failure of our early radio searches both point toward a galaxy free of other thinking, communicating beings. Hart and others have made mathematical models of Fermi’s question. You can consider the galaxy to be like a giant sand pile, with stars as grains of sand, and with life and intelligence as an initially rare but self-multiplying impurity spreading through the pile. Then you can make assumptions about the colonizing behavior of individual civilizations and calculate how the pattern will move through the galaxy. These models show pretty convincingly that if the process started off anywhere at almost any time in galactic history, then the wave of colonizing technological intelligence should long ago have passed through the entire galaxy.
Of course, you do have to start with some assumptions about the behavior of individual civilizations in order to model the macroscopic behavior of colonization through space. This is a lot like deriving laws of economics by assuming certain simple things about individual human behavior, and then showing how the mass effects of that behavior will manifest. Your assumptions can always be wrong, bringing your conclusions into doubt. There is a lot of room for finding the answer that you are seeking—a dangerous possibility in a science such as SETI, which obviously contains a great deal of subjectivity. Hart’s calculations, and others that followed, have often assumed that some technological species will be motivated to expand as much as possible, to colonize any planet they can get their grasping tentacles on, to keep launching new colonization missions until they have left their mark everywhere, and to maintain this behavior through many, many successive migrations over millions of years. It’s the same narrative I critiqued earlier in this chapter, as the “inevitable expansion fallacy,” often expressed as belief in the inexorable progression through Kardashev’s types of civilizations.
Defenders of Hart’s argument consider it obvious that at least some civilizations will want to keep sending out “colony ships” that will establish new planetary civilizations and send out more colonizing ships until they have filled the entire galaxy. Is this something that happens out in the real galaxy, or only in human science-fiction stories, projecting, onto unknown others, a mentality that is already becoming obsolete on our own planet?
If you accept the premises of the uniqueness argument, then if a technological civilization got started anywhere, by now it should be everywhere. In that case, absence of evidence really is evidence of absence.
Fermi Answer 5: The Sustainability Solution
It may be, as I argue earlier, that truly intelligent civilizations do not grow without limit. Maybe advanced societies inevitably turn against an expansionist mentality, and focus on the survival and quality of life on their home worlds. If it is rare or aberrant behavior for a civilization to expand relentlessly, then the chance that this pattern is main
tained and repeated throughout countless generations of colonizing and recolonizing, unceasingly over millions of years may be effectively zero. This would resolve the paradox. They are out there but are not driven to keep expanding and to colonize the entire galaxy. The answer to “Where are they?” may be: they’re all over the universe, cultivating their own gardens and minding their own business.
This idea has been explored by some young scholars who, appropriately, relate it to the current survival challenges of humanity in the Anthropocene. In 2009, Jacob Haqq-Misra, whose studies of Earth’s future human-altered climate cycles I discuss in chapter 4, and Seth Baum, an ethicist who studies global catastrophic risk, published “The Sustainability Solution to the Fermi Paradox”18 which included a critique of the assumption, based on human history, that civilizations must grow exponentially. They pointed out that not all civilizations have been exponentially expansive, and those that have done so often proved unsustainable and suffered collapse. They concluded:
The absence of ETI observations can be explained by the possibility that exponential or other faster-growth is not a sustainable development pattern for intelligent civilizations.
As we evolve our way toward Terra Sapiens, a wise Earth, we may shed this reflexive desire for physical expansion. The Exo sapiens born of other worlds may have done the same. They may be out there in reasonable abundance without running roughshod over the entire galaxy. The Great Silence might actually be a very good sign.
Fermi Answer 6: The galaxy is silent because contact is very dangerous.
There are several reasons why contact could be much more dangerous than we usually imagine, and even represent an existential threat to humanity. This possibility has been raised recently in a newly heated debate within the SETI community, which I will explore in the next chapter, over the wisdom of sending out messages from Earth to provoke a response. Advanced aliens might be malevolent or inadvertently harmful. It has been proposed that the Great Silence could result because civilizations have all been destroyed or because they know better than to attract attention to themselves.
Certainly it is possible that, even if extraterrestrials are not in any way malevolent, contact would still have an extremely disruptive effect on us. Many people believe—I think with good reason—that it would change us profoundly. Imagined scenarios run the gamut from salvation to damnation. Many people view advanced extraterrestrials as powerful and hopeful creatures who might come and save us from ourselves. This idea was explored in the novels of Arthur C. Clarke such as Childhood’s End (1953) and 2001: A Space Odyssey (1968). Clarke gave us utopian, transformative visions where extraterrestrials inducted us into our next phase of evolution, allowing us to achieve some kind of cosmic maturity that eluded us while we were isolated from galactic culture. SETI pioneers such as Sagan and Drake have proposed that advanced civilizations might send information designed to teach us the keys to survival. This utopian view of contact is in stark contrast to the idea of the invading, conquering, or destroying aliens portrayed in War of the Worlds and countless subsequent alien invasion stories.
Some SETI theorists believe that the silence is conspicuous and could mean that there are dangers lurking in the galaxy. If there are many civilizations out there, and none of them are announcing their locations, do they know something we don’t know? Or, if there are no civilizations, did something happen to them all?
What if there is something out there that seeks out and destroys young broadcasting civilizations? One way to do this would be to build a fleet of self-replicating machines that spread throughout the galaxy, listening for the first radio signals of fledgling technical races, ready to sweep down on these worlds and obliterate all life. Such killer probes are called “Berserkers,” after a 1970s science-fiction series by Fred Saberhagen that invoked relentless machines programmed to destroy all organic life. Yet, as is often the case in this field, when you study an idea carefully, you discover that Shklovsky and Sagan were already there. As they phrase it in Intelligent Life in the Universe: “Might an extraterrestrial society want to be alone at the summit of Galactic power, and make a careful effort to crush prospective contenders?”
There is no certain rational rebuttal to the frightening and bleak possibility of Berserkers, and (it seems) no good way to assess the likelihood of such scenarios. These hypotheses may seem paranoid, but that doesn’t mean they are not true. As solutions to the Fermi paradox, they represent perfectly logical possibilities. How seriously you take them probably reflects your own psychology. Personally I don’t believe that advanced aliens will want to harm or destroy us. I can cloak this belief in logical arguments, but honestly I think it comes down to spiritual reasons, arising from my faith in the basic goodness of life, intelligence, and consciousness. This may be the best retort against the logical possibility of evil, paranoid Berserkers enforcing a quiet and barren galaxy. As a Kwakiutl chief once advised, “Do not fear the universe.”
I know some of this sounds more like cheesy science fiction than sober science, but all these ideas can be found, discussed, and debated within the peer-reviewed scientific literature. When it comes to the paths that evolution of intelligence may take elsewhere, science-fiction writers have done a better job than scientists of exploring the wide landscape of possibilities. They have the advantage of not having to undergo peer review, and they are paid to push the envelope, while the rest of us furiously scribble equations on the back of it. Consequently, some fraction of their guesses should turn out to be right.
Some people feel they know the answer. They are certain that we are completely alone in the universe, or they know for sure that we are not alone. Yet at present the only foolish answer is an overconfident one. Fermi’s question, like Drake’s equation, serves to spark a conversation that leads us through the logical options. As we learn more about the universe, the reasonable options slowly narrow. As of now, however, the possibilities are still wide open. Is the chance of intelligence evolving on an appropriate planet nearly inevitable, as the Dolphins of Green Bank concluded, or so rare as to make the search fruitless, as others have stated? Will advanced aliens display a universal altruism and wisdom that characterizes all minds winnowed through the bottleneck of powerful technology? Or will they be ruthless predators who have ensured their own survival by destroying all potential competitors? Are intelligent creatures out there seeking conversation, broadcasting high-tech survivalist sermons, or hunting for competitors to quash or worlds to steal? Sophisticated arguments appealing to history, anthropology, or biology predict everything from a lonely universe to inevitable, ubiquitous technological civilizations. In the absence of data, these questions are as much philosophy as science. Intellectual honesty demands that we remain comfortable with uncertainty as we explore, experiment, and speculate. And so we search. And listen. And wait…
7
FINDING OUR VOICE
The Destiny of Earthseed is to take root among the stars.
—Octavia Butler
Shouting in the Dark
It has taken far too long to get through. Finally, an answer comes, but the signal is weak with static. We search for a common language, encouraged by a shared desire to communicate, by an assumption of goodwill.
“My understanding of spoken English not so good,” explains Alexander Zaitsev from Moscow. Graciously awkward, he has an easier time talking than listening, and our conversation does not get very far. “Better we e-mail,” he suggests. I had called him in September 2007 to discuss a growing dispute in the SETI community, a group of scholars I have long admired for their selfless dedication to a long-term endeavor, for keeping their eyes on the cosmic prize. Yet Zaitsev was now playing a starring role in a festering quarrel that had opened into an angry rift.
The spat is over the idea of sending messages from Earth toward other stars, known as “active SETI,” in contrast to the traditional, more passive approach of just listening for messages from others. Should we try to provoke a response, shout as
loudly as we can toward the stars, and then cup our ears and listen? This would be a break with the sixty-five-year SETI practice of patient searching, assuming that others are broadcasting. Some scientists think it’s time to shake things up a little bit and announce our presence to the galaxy. Others are not so sure this is a good idea, at least not without inclusive worldwide discussion and debate. Others still are dead set against it, regarding it as an unconscionably irresponsible act that could open up our world to unprecedented existential risk.
We always knew SETI could take a long time, and that success was uncertain at best. It was always envisioned as a multigenerational effort. Still, you cannot participate unless you imagine the possibility of success, picture the adrenaline rush of discovery and the mechanics of confirmation, announcement, and reaction. SETI practitioners have rehearsed for that moment many times, in their heads and in actuality. They’ve developed confirmation protocols and announcement procedures to follow, just in case. And they are only human. Who wouldn’t feel a little impatient? Some feel that we have been waiting long enough, and it’s now time to take a more active approach.
Zaitsev, chief scientist at the Russian Academy of Sciences’ Institute of Radio Engineering and Electronics, thinks we need to let the other denizens of the Milky Way galaxy know that we are here, that they are not alone. He has decided that we can no longer wait for an answer from the sky, and he has taken it upon himself to start broadcasting. Rather than use “active SETI,” he prefers to call his broadcast program METI, for Messages to Extraterrestrial Intelligence. The two terms are now used interchangeably. Zaitsev is reaching out to the inhabitants of nearby planetary systems because he feels he must, because it is the right thing to do. He feels he’s speaking for all mankind.
Earth in Human Hands Page 35
