Science fiction has always had its share of Earthside dystopias, but starflight’s allure has persisted, despite the dark scrutiny of space travel in the works of writers like J. G. Ballard. But what happens if we develop the technologies to go to the stars and find the journey isn’t worth it? Gregory Benford recently reviewed a novel that asks these questions and more, Kim Stanley Robinson’s Aurora (Orbit Books, 2015). A society that reaches the Moon and then turns away from it may well prompt questions on how it would react to the first interstellar expedition. Benford, an award-winning novelist, has explored star travel in works like the six novels of the Galactic Center Saga and, most recently, in the tightly connected Bowl of Heaven and Shipstar. His review is a revised and greatly expanded version of an essay that first ran in Nature.
by Gregory Benford
Human starflight yawns as a vast prospect, one many think impossible. To arrive in a single lifetime demands high speeds approaching lightspeed, especially for target stars such as Tau Ceti, about twelve light years away.
Generation ships form the only technically plausible alternative method, implying large biospheres stable over centuries. Or else a species with lifetimes of centuries, which for fundamental biological reasons seems doubtful. (Antagonistic plieotropy occurs in evolution, ie, gene selection resulting in competing effects, some beneficial in the short run for reproduction, but others detrimental in the long.) So for at least for a century or two ahead of us, generation ships (“space arks”) may be essential.
Aurora depicts a starship on a long voyage to Tau Ceti four centuries from now. It is shaped like a car axle, with two large wheels turning for centrifugal gravity. The biomes along their rims support many Earthly lifezones which need constant tending to be stable. They’re voyaging to Tau Ceti, so the ship’s name is a reference to Isaac Asimov’s The Robots of Dawn, which takes place on a world orbiting Tau Ceti named Aurora. Arrival at the Earthlike moon of a super-Earth primary brings celebration, exploration, and we see just how complex an interstellar expedition four centuries from now can be, in both technology and society.
In 2012, Robinson declared in a Scientific American interview that “It’s a joke and a waste of time to think about starships or inhabiting the galaxy. It’s a systemic lie that science fiction tells the world that the galaxy is within our reach.” Aurora spells this out through unlikely plot devices. Robinson loads the dice quite obviously against interstellar exploration. A brooding pessimism dominates the novel.
There are scientific issues that look quite unlikely, but not central to the novel’s theme. A “magnetic scissors” method of launching a starship seems plagued with problems, for example. But the intent is clear through its staging and plot.
I’ll discuss the quality of the argument Aurora attempts, with spoilers.
The earlier nonfiction misgivings of physicist Paul Davies (in Starship Century) and biologist E.O. Wilson (in The Meaning of Human Existence) about living on exoplanets echo profoundly here. As a narrator remarks, “Suspended in their voyage as they had been, there had never been anything to choose, except methods of homeostasis.” Though the voyagers in Aurora include sophisticated biologists, adjusting Earth life to even apparently simple worlds proves hard, maybe impossible.
The moon Aurora is seemingly lifeless. Yet it has Earth-levels of atmospheric oxygen, which somehow the advanced science of four centuries hence thinks could have survived from its birth, a very unlikely idea (no rust?—this is, after all, what happened to Mars). Plot fix #1.
This elementary error, made by Earthside biologists, brings about the demise of their colony plans, in a gripping plot turn that leads to gathering desperation.
The lovingly described moon holds some nanometers-sized mystery organism that is “Maybe some interim step toward life, with some of the functions of life, but not all…in a good matrix they appear to reproduce. Which I guess means they’re a life-form. And we appear to be a good matrix.” So a pathogen evolved on a world without biology? Plot fix #2.
Plans go awry. Backup plans do, too. “Vector, disease, pathogen, invasive species, bug; these were all Earthly terms…various kinds of category error.”
What to do? Factions form amid the formerly placid starship community of about 2000. Until then, the crew had felt themselves to be the managers of biomes, farming and fixing their ship, with a bit of assistance from a web of AIs, humming in the background.
Robinson has always favored collective governance, no markets, not even currencies, none of that ugly capitalism—yet somehow resources get distributed, conflicts get worked out. No more. Not here, under pressure. The storyline primarily shows why ships have captains: stress eventually proves highly lethal. Over half the crew gets murdered by one faction or another. There is no discipline and no authority to stop this.
Most of the novel skimps on characters to focus on illuminating and agonizing detail of ecosphere breakdown, and the human struggle against the iron laws of island biogeography. “The bacteria are evolving faster than the big animals and plants, and it’s making the whole ship sick!” These apply to humans, too. “Shorter lifetimes, smaller bodies, longer disease durations. Even lower IQs, for God’s sake!”
Robinson has always confronted the nasty habit of factions among varying somewhat-utopian societies. His Mars trilogy dealt with an expansive colony, while cramped Aurora slides toward tragedy: “Existential nausea comes from feeling trapped… that the future has only bad options.”
Should the ship return to Earth?
Many riots and murders finally settle on a bargain: some stay to terraform another, Marslike world, the rest set sail for Earth. The ship has no commander or functional officers, so this bloody result seems inevitable in the collective. Thucydides saw this outcome over 2000 years ago. He warned of the wild and often dangerous swings in public opinion innate to democratic culture. The historian described in detail explosions of Athenian popular passions. The Athenian democracy that gave us Sophocles and Pericles also, in a fit of unhinged outrage, executed Socrates by a majority vote of one of its popular courts. (Lest we think ourselves better, American democracy has become increasingly Athenian, as it periodically whips itself up into outbursts of frantic indignation.)
When discord goes deadly in Aurora, the AIs running the biospheres have had enough. At a crisis, a new character announces itself: “We are the ship’s artificial intelligences, bundled now into a sort of pseudo-consciousness, or something resembling a decision-making function.” This forced evolution of the ship’s computers leads in turn to odd insights into its passengers: “The animal mind never forgets a hurt; and humans were animals.” Plot Fix #3: sudden evolution of high AI function that understands humans and acts like a wise Moses.
This echoes the turn to a Napoleonic figure that chaos often brings. As in Iain Banks’ vague economics of a future Culture, mere humans are incapable of running their economy and then, inevitably, their lives. The narrative line then turns to the ship AI, seeing humans somewhat comically, “…they hugged, at least to the extent this is possible in their spacesuits. It looked as if two gingerbread cookies were trying to merge.”
Governance of future societies is a continuing anxiety in science fiction, especially if demand has to be regulated without markets, as a starship must. (Indeed, as sustainable, static economies must.) As far back as in Asimov’s Foundation, Psychohistory guides, because this theory of future society is superior to mere present human will. (I dealt with this, refining the theory, in Foundation’s Fear. Asimov’s Psychohistory resembled the perfect gas law, which makes no sense, since it’s based on dynamics with no memory; I simply updated it to a modern theory of information.) The fantasy writer China Mieville has similar problems, with his distrust of mere people governing themselves, and their appetites, through markets; he seems to favor some form of Politburo. (So did Lenin, famously saying “A clerk can run the State.”)
Aurora begins with a society without class divisions and exploitation in the Marxist sense, and though some people seem destined to be respected and followed, nothing works well in a crisis but the AIs—i.e., Napoleon. The irony of this doesn’t seem apparent to the author. Similar paths in Asimov, Banks and Mieville make one wonder if similar anxieties lurk. Indeed, Marxism and collectivist ideas resemble the similar mechanistic theory of Freudian psychology (both invented by 19th C. Germans steeped in the Hegelian tradition)—insightful definitions, but no mechanisms that actually work. Hence the angst when things go wrong with a supposedly fundamental theory.
The AIs, as revealed through an evolving and even amusing narrative voice, follow human society with gimlet eyes and melancholy insights. The plot armature turns on a slow revelation of devolution in the ship biosphere, counterpointed with the AI’s upward evolution—ironic rise and fall. “It was an interrelated process of disaggregation…named codevolution.” The AIs get more human, the humans more sick.
Even coming home to an Earth still devastated by climate change inflicts “earthshock” and agoraphobia. Robinson’s steady fiction-as-footnote thoroughness brings us to an ending that questions generational, interstellar human exploration, on biological and humanitarian grounds. “Their kids didn’t volunteer!” Of course, immigrants to far lands seldom solicit the views of their descendants. Should interstellar colonies be different?
Do descendants as yet unborn have rights? Ben Finney made this point long ago in Interstellar Migration, without reaching a clear conclusion. Throughout human history we’ve made choices that commit our unborn children to fates unknown. Many European expeditions set sail for lands unseen, unknown, and quite hostile. Many colonies failed. Interstellar travel seems no different in principle. Indeed, Robinson makes life on the starship seem quite agreeable, though maybe tedious, until their colony goal fails.
The unremitting hardship of the aborted colony and a long voyage home give the novel a dark, grinding tone. We suffer along with the passengers, who manage to survive only because Earthside then develops a cryopreservation method midway through the return voyage. So the deck is stacked against them—a bad colony target, accidents, accelerating gear failures, dismay… until the cryopreservation that would lessen the burden arrives, very late, so our point of view characters do get back to Earth and the novel retains some narrative coherence, with character continuity. Plot Fix #4.
This turn is an authorial choice, not an inevitability. Earthsiders welcome the new cryopreservation technologies as the open door to the stars; expeditions launch as objections to generation ships go away. But the returning crew opposes Earth’s fast-growing expeditions to the stars, because they are just too hard on the generations condemned to live in tight environments—though the biospheres of the Aurora spacecraft seem idyllic, in Robinson’s lengthy descriptions. Plainly, in an idyllic day at the beach, Robinson sides with staying on Earth, despite the freshly opened prospects of humanity.
So in the end, we learn little about how our interstellar future will play out.
The entire drift of the story rejects Konstantin Tsiolkovsky’s “The Earth is the cradle of mankind, but humanity cannot live in the cradle forever.” – though we do have an interplanetary civilization. It implicitly undermines the “don’t-put-all-your-eggs-in-one-basket” philosophy for spreading humanity beyond our solar system. Robinson says in interviews this idea leads belief that if we destroy Earth’s environment, we can just move. (I don’t know anyone who believes this, much less those interested in interstellar exploration.) I think both ideas are too narrow; expansion into new realms is built into our evolution. We’re the apes who left Africa.
Robinson takes on the detail and science of long-lived, closed habitats as the principal concern of the novel. Many starship novels dealt with propulsion; Robinson’s methods—a “magnetic scissors” launch and a mistaken Oberth method of deceleration—are technically wrong, but beside the point. His agenda is biological and social, so his target moon is conveniently hostile. Then the poor crew must decide whether to seek another world nearby (as some do) or undertake the nearly impossible feat of returning to Earth. This deliberately overstresses the ship and people. Such decisions give the novel the feel of a fixed game. Having survived all this torment, the returning crew can’t escape the bias of their agonized experience.
Paul Davies pointed out in Starship Century that integrating humans into an existing alien biosphere (not a semi-magical disaster like his desolate moon with convenient oxygen) is a very hard task indeed, because of the probable many incompatibilities. That’s a good subject for another novel, one I think no one in science fiction has taken up. This novel avoids that challenge with implausible Plot fix #2.
Realistically considered, the huge problems of extending a species to other worlds can teach us about aliens. If interstellar expansion is just too hard biologically (as Paul Davies describes) then the Fermi paradox vanishes (except for von Neumann machines, as Frank Tipler saw in the 1970s). If aliens like us can’t travel, maybe they will expend more in SETI signaling? Or prefer to send machines alone? An even-handed treatment of human interstellar travel could shore up such ideas.
Still, a compelling subject, well done in Robinson’s deft style. My unease with the novel comes from the stacked deck its author deals.
The New Horizons imagery has been breathtaking, and never more so than in the image below. Here we’re seeing Pluto seven hours after the July 14 closest approach, looking back at Pluto as it occults the Sun. The backlit atmosphere shows us layers of haze reaching 130 kilometers above the surface.
Image: Pluto sends a breathtaking farewell to New Horizons. Backlit by the sun, Pluto’s atmosphere rings its silhouette like a luminous halo in this image taken around midnight EDT on July 15. This global portrait of the atmosphere was captured when the spacecraft was about 2 million kilometers from Pluto and shows structures as small as 19 kilometers across. The image, delivered to Earth on July 23, is displayed with north at the top of the frame. Credit: NASA/JHUAPL/SwRI.
Alan Stern, principal investigator for New Horizons, speaks of having his jaw on the ground when he saw our first image of an atmosphere in the Kuiper Belt, and for good reason. We’ve known that Pluto had some kind of atmosphere, one that might well freeze out as the dwarf planet moved further away from the Sun, but here we actually see it in two distinct layers of haze, one about 80 kilometers up, the other at about 50 kilometers. The atmosphere is not a surprise, but the beauty of the image when first encountered is stunning.
Michael Summers (George Mason University) believes the hazes seen in the image help us understand the processes at work on the surface, helping to create complex hydrocarbon molecules that account for the reddish hue we all remarked on as New Horizons neared the world. Summers believes we are seeing hydrocarbons falling into the lower, colder parts of the atmosphere, condensing as ice particles to form the haze layers. Ultraviolet light from the Sun then converts the hazes into the dark hydrocarbons — tholins — found on Pluto’s surface.
Image: Hydrocarbon hazes in Pluto’s atmosphere, extending as high as 130 kilometers above the surface, are seen for the first time in this image, which was taken on July 14. New Horizons’ Long Range Reconnaissance Imager captured this view about seven hours after the craft’s closest approach, at distance of about 360,000 kilometers from Pluto. Inset: False-color image of hazes reveals a variety of structures, including two distinct layers, one at 80 kilometers above the surface and the other at about 50 kilometers. Credit: NASA/JHUAPL/SwRI.
Ice Flows and Geology
New Horizons’ LORRI instrument has also shown us details of Sputnik Planum, a region inside the western half of Tombaugh Regio, the now famous ‘heart’ of Pluto. A sheet of ice within the region appears to have flowed in ways similar to glaciers here on Earth, and indeed may still be flowing, a kind of surface we would expect only on active worlds. Meanwhile, we learn from the Ralph instrument that the center of Sputnik Planum is rich in nitrogen, carbon monoxide and methane ices.
“At Pluto’s temperatures of minus-390 degrees Fahrenheit, these ices can flow like a glacier,” says Bill McKinnon, deputy leader of the New Horizons Geology, Geophysics and Imaging team at Washington University in St. Louis. “In the southernmost region of the heart, adjacent to the dark equatorial region, it appears that ancient, heavily-cratered terrain has been invaded by much newer icy deposits.”
Take another look at Sputnik Planum, in an image that NASA released ten days ago. It’s a plain without craters that researchers believe to be no more than 100 million years old.
Image: This frozen region is north of Pluto’s icy mountains and has been informally named Sputnik Planum (Sputnik Plain), after Earth’s first artificial satellite. The surface appears to be divided into irregularly-shaped segments that are ringed by narrow troughs. Features that appear to be groups of mounds and fields of small pits are also visible. This image was acquired by the Long Range Reconnaissance Imager (LORRI) on July 14 from a distance of 77,000 kilometers. Features as small as 1 kilometer across are visible. The blocky appearance of some features is due to compression of the image. Credit: NASA/JHUAPL/SWRI.
Back in the days of Apollo 8, journalist David Brinkley was one of those covering the story when the spacecraft disappeared behind the Moon as the crew prepared for Lunar Orbit Insertion. The engine burn had to be performed on the far side, leaving controllers and journalists to wait for the signal that all had gone well. I remember Brinkley asking during the interminable wait, “What do you say when you come around from behind the Moon for the first time. For the first time?”
The chill down my spine at that thought back in 1968 was re-created when I saw the first of New Horizons’ ‘look back’ images. Even as our Voyagers pushed toward interstellar space, Pluto has remained a mystery, a symbol of all that is remote and at the edge of our knowledge. Now we have the view from behind Pluto, a lambent ring circling a place with features we have named. New Horizons reminds us that space exploration is transformative, its images shaping our identity as a species as we see what we have done and what we can become.
We recently looked at the $100 million infusion into the SETI effort by Yuri Milner, with backing by major figures in the field. When I’m considering SETI developments, I always look to Michael Michaud, whose judicious perspective in his book Contact with Alien Civilizations (Copernicus, 2007) remains a touchstone. He served in senior international science and technology positions with the U.S. State Department and two American embassies and acted as chairman of working groups at the International Academy of Astronautics that discuss SETI issues, in addition to publishing numerous articles and papers on the implications of contact.
Michaud recently addressed the Astrobiology Science Conference 2015 (AbSciCon2015) in Chicago in mid-June, more than a month before the Breakthrough Initiatives announcement, and touched on many of the relevant themes. What follows is an essay drawn from that talk but expanded with new material and references. What if a very advanced technology is indistinguishable not from magic but from nature? Read on for Michaud’s perspective on our thus far unsuccessful search for other civilizations, what it implies about our methods and ourselves, and where we go from here.
by Michael A.G. Michaud
For centuries, many humans have believed that life and intelligence arise on other worlds. We have repeatedly anticipated their discovery, hoping to find them on the Moon, on the other planets of our solar system, and now on planets orbiting other stars.
More than a century ago, a few astronomers observing Mars at the limits of their instruments perceived lines on the Martian surface. Some came to an erroneous conclusion that they were channels or canals constructed by intelligent beings. (1) A newer technology, robotic spacecraft, revealed in the 1960s that the canals did not exist outside the observers’ imaginations. Some things are not only unknown; they may be unknowable with the scientific means available to us at the time.
That has led some very intelligent people to conclude that such things can never be known. French philosopher Auguste Comte declared in 1842 that, although we may learn the forms, distances, sizes and motions of stars, we can never know their chemical composition. (2) Yet Fraunhofer already had discovered dark lines in the Sun’s spectrum by an early form of the spectroscopy that later revealed the chemistry of astronomical objects. What seems unknowable now may become knowable later.
Before 1959, most astronomers would have said that detecting signals from technological civilizations at interstellar distances was impossible. Cocconi and Morrison pointed out that the means had come into our hands in the form of radio astronomy. (3) What had been unknowable became knowable through scientific and technological advance.
That inspired a Search for Extraterrestrial Intelligence that seeks evidence of extraterrestrial technology in the form of radio signals. What may be the least likely from of alien biology – a transmitting intelligence –seemed the easiest to detect with the means we had at that time.
After 55 years of intermittent searches, or about two human generations, we now have the perspective to treat SETI as an historical phenomenon. There have been well over one hundred search programs. Searches have been broadened beyond radio signals to visible regions of the spectrum and to the infrared, notably to seek emissions from Dyson spheres.
This effort has constrained some dimensions of search strategy, such as the probability of beacons. Yet there has been no confirmed detection.
There are many potential explanations for SETI’s lack of success. Here I will mention only one, voiced by SETI pioneer Frank Drake: Radio and visual spectrum transmissions may be temporary artifacts of technological intelligence. There might be only a narrow window of time in the development of technological civilizations when noisy electromagnetic signals are generated in large amounts. (4)
Those scientists who have dedicated much of their careers to SETI deserve respect for maintaining scientific standards as they sought to achieve a very difficult goal. Yet, after half a century, it is easy to become discouraged about SETI. We can hope that new observing capabilities like the Square Kilometer Array will make some form of detection more likely, but there is no guarantee of success.
The lack of a confirmed finding could lead to a false negative, reflecting the limitations of our technologies, our search strategies, and our assumptions.
Civilizations more technologically advanced than ours might be invisible to our present means of searching. Compressed digital data may be indistinguishable from random noise.
Arthur Clarke famously said that any sufficiently advanced technology would be indistinguishable from magic. (5) What if a very advanced technology is indistinguishable from nature?
SETI Institute astronomer Seth Shostak was quoted as saying in 2011 that “If this experiment has merit, it’s going to succeed within two or three decades. If it doesn’t, then there’s something fundamentally wrong with our assumptions.” (6)
Shostak also has written that our own developmental trajectory suggests that, shortly after inventing technology capable of interstellar communication, a society also develops artificial intelligence. If so, AI may constitute the majority of the sentience in the cosmos. Consequently, looking for signals from habitable planets could be the wrong approach for SETI. (7)
Eventual success still may be possible, though it might require a broader strategy and technical means not yet available to us. The existence of alien civilizations can not be disproved.
WHY DO WE SEARCH?
Why do we seek distant intelligence, even in the face of repeated failure? Is SETI just an extension of normal science? I suggested in 1993 that we search for communicating civilizations in the hope that contact with intelligent others will introduce new and hopefully positive factors into human affairs. (8) The discovery of extraterrestrial intelligence would involve much more than science, raising important philosophical and societal questions.
Even without a discovery, the search has inspired creative thought. As the SETI literature has grown and diversified, we have seen many proposed scenarios of discovery, and many different predictions of what contact might bring. What was once an exotic, small-scale scientific enterprise has led to a vast, multidisciplinary thought experiment about the nature and behavior of intelligence, both on and beyond the Earth.
The prospect of interacting with an alien intelligence has stimulated both hopes and fears; predictions of the consequences have ranged from utopian to apocalyptic. Some authors have imagined extraterrestrials as noble, altruistic philosopher-kings who will help us to solve our problems. Others have imagined ruthless alien invaders who will enslave or destroy us.
These are exaggerations of our own behaviors, at our best and at our worst. It is time to escape Hollywood, particularly the tiresome invasion scenario.
Astronomers Ivan Almar and Jill Tarter proposed a scale to categorize the impact of contact. (9) Shostak gave us hypothetical examples based on that scale, ranging from benign to disastrous. He later published a fictional story which ended with the Earth’s atmosphere bursting into flame. (10)
That brings me to the debate about Active SETI, also known as Messaging to Extraterrestrial Intelligence. METI advocates wish to send unusually powerful targeted signals to alert other technological civilizations to our existence in the hope of stimulating a response.
It is easy to understand the frustration of those who have devoted their working lives to discovering signals generated by alien beings. But METI is not physical or biological science. It is an attempt to provoke a reaction from a technological civilization whose capabilities and intentions are not known to us.
That reminds us that a factor is missing from the Drake Equation, a factor almost impossible to quantify: alien motivations. Intelligent beings can make choices and take actions. We cannot assume that their actions will be ones that we prefer. Our assumptions about alien behavior have not passed the empirical test.
METI advocates assume there could not be any negative consequences from contact, for two reasons. First, more technologically advanced extraterrestrials are benign, an unproven assumption. Chinese science fiction writer Cixin Liu put it this way:
On Earth, humankind can step onto another continent and, without a thought, destroy the kindred civilizations found there through warfare and disease. But when they gaze up at the stars, they turn sentimental and believe that if extraterrestrial intelligences exist, they must be civilizations bound by universal, noble, moral sentiments, as if cherishing and loving different forms of life are parts of a self-evident universal code of conduct. (11)
Second, METI advocates assume that interstellar flight by robotic spacecraft is impossible. We humans already have reached all the planetary bodies in our own solar system through such spacecraft, a feat that many considered impossible as late as the 1950s. Some of our machines have left our solar system. There already exists an extensive scientific and engineering literature on interstellar probes, frequently reported on the Centauri Dreams blog. Before dismissing interstellar flight by machines on the basis of its cost to us, we should try to estimate its feasibility for a civilization much more technologically advanced than our own.
Consider an example from our own history. Humans began populating the Americas about 17,000 years ago. (12) For thousands of years, after the land bridge closed, oceans insulated newly indigenous Americans from the peoples of other continents. Technological advance, in the form of reliable ocean-going ships and gunpowder weapons, made them vulnerable. The growing credibility of direct contact by uninhabited machines requires us to widen the range of possible consequences.
Whatever the consequences of calling attention to ourselves might be, our descendants will not be able to opt out of them. Prudence suggests that we should conduct a global conversation on this issue before we embark on a sustained program of broadcasting our presence with more powerful transmissions.
Almar proposed what he called the San Marino scale, intended to quantify the potential hazard of transmissions. The main factors are the signal strength in relation to Earth’s natural background radiation, and characteristics of the transmission such as direction and duration. (13)
One approach would be to set quantitative thresholds for the proposed signals, such as the normal power, duration, and directionality of pulses from military and planetary radars. Above that level, transmissions would require approval from the organizations that fund, control, or regulate the largest radars and transmitting radio telescopes. Radio telescopes capable of transmitting powerful signals to distant stars have been funded by taxpayers, making their use a legitimate subject for governmental policy decisions.
A discussion, perhaps within the United Nations, could lead to an agreed statement of international policy on such transmissions. We already have seen successful examples of this procedure in space debris and in planetary defense against asteroid impacts.
We could shift the debate to a more positive agenda. Expanding SETI beyond the microwave window could be more productive than sending our own signals.
An editorial in Nature in 2009 put it this way: “Will we want to beam messages to those other Earths? That question is not resolved. But we should at least listen. Humankind may decide that it does not want to open its mouth, but it would be foolish to cover its ears.” (14)
The discovery of planets in orbit around other stars is changing the game. We should recall that some astronomers had been skeptical, even dismissive, of the idea that such planets existed. (15)
Finding many extrasolar planets—including some that may be near analogs of the Earth—enables us to begin filling in the suitable planet factor in the Drake Equation. On this point, the SETI optimists were largely right.
Thanks to technological advance and clever people, we soon may be able to search for what is likely to be far more widespread than transmitting civilizations: evidence of biology. What once was considered unknowable again is becoming knowable.
Searching for evidence of life with powerful new observing technologies coming on line in the next decade may have a higher probability of success than searching for signals from ETI. Finding a form of biology on one of those planets would give us a second data point for the life factor in the Drake equation, a second L.
Some believe that discovering alien life just a matter of time, effort, and improving technology. NASA’s Chief Scientist was quoted as saying that we’re going to have strong indications of life beyond Earth within a decade, and definitive evidence within 20 to 30 years. (16)
That optimism is admirable. Yet the nagging voice of history suggests caution.
We might recall older mistakes, such as interpreting the periodic darkening of the Martian surface as evidence of the seasonal spread of plant life.
At the same time, we should beware of false negatives due to the limitations of our equipment and our search strategies. Once again, we are observing at the limits of our technologies. A false negative might reflect our assumptions about extrasolar biology, which may be very different from the biology we know on Earth.
There also could be false positives, or evidence that is inconclusive or disputed. The Mars Rock controversy of 1996 may be a preview of what will happen. We are on the fringes of knowability, the time when observations are most likely to lead to ambiguous results.
Before astronomers began finding planets around other stars, our model of planetary systems was based on the one example we knew—our own solar system.
Now we know that our case is not typical. (17) Is that also true of biology, intelligence, and behavior? Our models of extrasolar life and intelligence, usually inspired by Earthly examples, may prove to be exceptions to galactic general rules.
We may be underestimating how alien the products of utterly different evolutions could be. No one anticipated the strange creatures that scientists first found around Pacific sea floor vents in 1977. The search for extrasolar life will spark new thought experiments about the nature of very different evolutions.
Those who seek life on distant planets may be wise to remember the SETI experience. Like the search for signals, the search for extrasolar life may be more difficult than its most optimistic supporters/advocates foresee. (18) Our expectations may exceed the grasp of science as we know it today. Yet a failure to detect such life would not prove the absence of life elsewhere.
While discovering simpler forms of life would be fascinating for scientists, non-intelligent life will inspire less public interest than alien intelligence. Such life can not grant us wisdom, nor can it threaten us. Emotional debates about the possible consequences of contact—our hopes and our fears– may fade.
The SETI experience tells us that there is no guarantee of success. Yet the search is likely to continue, in one form or another.
THE SECOND I
Detecting a habitable world, or extraterrestrial life, could inspire greater optimism about finding ETI by making the existence of alien intelligence seem more probable. Could studies of extrasolar planets reveal evidence of a technological civilization?
Some suggest that evidence of certain chemicals in exoplanet atmospheres may imply energy consumption or waste products of industry. (19) But fuel burning and waste-generating industry may be temporary phenomena in a planet’s history.
Observations might miss non-technological intelligence, or intelligence that employs technologies that we cannot detect or that are unknown to us.
The discovery of an alien civilization may not mean communication with it; there could be contact without communication. What we are looking for is not a dialogue of centuries, but an existence proof.
A failure to find evidence of intelligence could discourage those who hope for inspiration or assistance from outside. We may never receive guidance from distant stars, leaving us responsible for our own fate. That could help revive the anthropocentrism that SETI has challenged for half a century.
Even if sapient aliens exist elsewhere in the galaxy, our inability to find them with existing technologies could leave us effectively alone. The scientific paradigm of Earth’s uniqueness as the abode of life and intelligence has not yet been broken.
Finding ETI may be a multi-generational task. Discovery may require rigorous and repetitive searching and data analysis that last beyond individual human lifetimes. It may require a broader strategy, and a willingness to look in new places. It may require technical means not yet available to us.
We are in a transitional period. While both SETI and the search for life on extrasolar planets will go on, we are seeing an implicit shift of emphasis from seeking deliberate signals of technological intelligence to searching for evidence of life, which may be much more common.
A major factor in this shift is the vast disproportion in resources. The science of planet-hunting is funded much more generously than the science of seeking signals from other technological civilizations. SETI scientists can only dream of a taxpayer-funded capability equivalent to the Kepler telescope.
Planet hunters hope to make use of several powerful new instruments (James Webb Space Telescope, Thirty Meter Telescope, Giant Magellan Telescope, European Very Large Telescope, Transiting Exoplanet Survey Satellite). But detecting Earth’s twin may have to wait a decade or two. (20)
Ultimately, we may need interstellar probes for closer observation of potential life-bearing planets. Except for our Moon, all of our explorations in our solar system have been conducted by machines, not by inhabited spacecraft. That is even more likely at the interstellar scale.
In the long run, our own interstellar probes could lead to a role reversal. If they are detected by intelligent aliens, the impact of contact might flow from us to them.
There is another idea implicit in finding and characterizing distant worlds: some might be seen as future homes for our descendants. The theme of human expansion, so prominent in spaceflight literature, may be revived. As Paul Gilster put it, finding a habitable world within twenty light years, coupled with a failure of SETI, would be a powerful boost in building an interstellar consensus. (21) The ambition to travel to those distant worlds, and to convert them to human use, could generate a paradigm that we might call anthropocentrism with a goal.
Statistically, the nearest non-transiting habitable zone Earth-size planet may be within 23 light years.(22) One can envision a hundred year robotic mission to the star hosting such a planet; one human generation might start the project knowing that future generations would finish it.
Encouraging early work on interstellar probes is a small but necessary contribution. I hope that the new Nexus for Exoplanet System Science will reach out to those doing serious scientific and engineering work on interstellar flight by machines.
We may never find alien intelligences out there, but someday we may find extraterrestrial intelligences descended from us. What seems impossible now may become possible later.
Yet there is nothing inevitable about interstellar exploration. It has to be chosen as a course of action, and funded. We cannot foresee all the threats or opportunities that could motivate such ventures, nor can we be sure that those motivations will be enough to make starflight a necessary task for near future human generations.
If interstellar flight is possible, why don’t we see them? Even if technological civilizations have the scientific and technological knowledge to launch interstellar probes, they may not do so. Expansion could fail if technological societies are unable to agree on a course of action. They may suffer failures of perception, failures of imagination, failures of nerve, or failures of politics.
WHO WILL LEAD?
What nation, or which people, will lead this effort? In the near term, the United States will remain the biggest player in space, with the world’s largest and most diverse programs. But American elites lack consensus about where to go, or when.
They are turning away from shared visionary goals that would require us to amass public resources for long-term, large scale non-commercial projects like interstellar exploration or eventual human expansion.
In 1989, as the Cold War was ending, Francis Fukuyama wrote that the worldwide ideological struggle that brought forth daring, courage, imagination, and idealism will be replaced by economic calculation, the endless solving of technical problems, environmental concerns, and the satisfaction of sophisticated consumer demands. (23)
A society whose elites are preoccupied with immediate gratification will not support the vision of human expansion. Some pessimists have suggested that the age of manned spaceflight may be coming to a close. (24) Others express nostalgia for an age of exploration that ended with the mission to Pluto. (25)
Analysts predict that China will become the world’s largest economy less than fifteen years from now. (26) China’s space program is newer and smaller than its American counterpart, but it is growing. China is on the rise, with a determination to succeed in great societal endeavors and an authoritarian political system which makes that possible.
History is not about immutable fate. It is about the choices that humans make.(27)
I end with a quotation from another non-scientist, William Shakespeare:
There is a tide in the affairs of men
Which, taken at the flood, leads on to fortune…
On such a full sea are we now afloat:
And we must take the current when it serves,
Or lose our ventures.
(1) The history is described in Michael J. Crowe, The Extraterrestrial Life Debate, 1750-1900, Cambridge University Press, 1986, 480-540. Republished by Dover in 1999.
(2) Auguste Comte, The Positive Philosophy, Book II, Chapter 1 (1842).
(3) Giuseppe Cocconi and Philip Morrison, “Searching for Interstellar Communications,” Nature 184 (1959), 844-846.
(4) See Michael A.G. Michaud, Contact with Alien Civilizations, Copernicus (Springer), 264, and “Signs of Life,” The Economist, February 27, 2010, 87.
(5) Arthur C. Clarke, “Aspects of Science Fiction,” in Greetings, Carbon-Based Bipeds! Collected Essays, 1934-1998, St. Martin’s Press, 1999, 399.
(6) Quoted in Tim Folger, “Contact: The Day After, Scientific American, January 2011, 41-45.
(7) Shostak, Seth, “Searching for Non-Biological Extraterrestrial Intelligence,” paper presented at the Astrobiology Science Conference, Chicago, June 2015.
(8) Michaud, Michael A.G., “SETI and Diplomacy,” in G. Seth Shostak, editor, Progress in the Search for Extraterrestrial Life, Astronomical Society of the Pacific Conference Series, Volume 74, 1995, 551-554.
(9) Almar, Ivan and Jill Tarter, “The Discovery of ETI as a High Consequence, Low-Probability Event,” Acta Astronautica, 68 (2011), 358-361.
(10) Shostak, Seth, “The Rio Scale Applied to Fictional SETI Detections,” paper presented at the International Astronautical Congress in 2002, and “The Second Signal,” Communications of the Association for Computing Machinery 57 (January 2014), 128-129.
(11) Cixin Liu, The Three Body Problem, Doherty (Tor), 2014, 395. Published in China in 2006. Translated by Ken Liu.
(12) Ewen Callaway, “South America settled in one go,” Nature 520 (30 April 2015), 598-599.
(13) Hecht, Jeff and Paul Schuch, “The San Marino Scale: A New Analytical Tool for Assessing Transmission Risk,” Acta Astronautica 60 (2007), 57-59.
(14) “SETI at 50,” Nature 461 (17 September 2009), 316.
(15) Sage, Leslie. “Introduction to special section on exoplanets,” Nature 513 (2014), 327.
(16) Wall, Mike, Space.com. “Top NASA Scientist: We’ll Find Signs of Alien Life within a Decade,” nbcnews.com, accessed April 18, 2015.
(17) Sage, op.cit.
(18) LePage, Andrew, Astrobiology: A Cautionary Tale. Posted on Centauri-dreams.org February 27, 2015.
(19) “Signs of Life,” The Economist, April 17, 2010, 89-90.
(20) Anglada, Guillem, Doppler Worlds and M-Dwarf Planets, posted on Centauri-Dreams.org May 15, 2015.
(21) Gilster, Paul. Spaceflight and Legends, posted on Centauri Dreams December 16, 2011.
(22) Sara Seager, “Exoplanets Everywhere,” Sky and Telescope, August 2013, 18-26.
(23) “Nietzsche is not dead,” The Economist, October 15, 1994, 113.
(24) “The End of the Space Age,” The Economist, July 2, 2011, 7.
(25) Dennis Overbye, “A Great Ride While it Lasted,” The New York Times, July 7, 2015.
(26) Shanker, Thom. “Study Predicts Future for U.S. as No. 2 Economy.” The New York Times, December 11, 2012.
(27) Paine, S.C.M. The Wars for Asia, 1911-1949, Cambridge University Press, 2012, 7.