And the third question is: what does that take? Just as astrobiologists try to discern universal principles that may shape biological evolution, SETI theorists have, for the last sixty years, been poking at this question: could there be common laws that shape cultural evolution on different worlds? We infer that we are young and imagine that any civilization we are likely to encounter might be some kind of much older version of us. If we believe in the possible existence of these long-lived societies, does that mean we could become one? What is required of us? What are the impediments? How does that vision of long-lived civilizations map into our Anthropocene dilemma and how we respond to the threat of us?
No Transition, No Transmission
When we imagine alien technological intelligences, we start with some variation of what we have here. Try as we might, it’s hard to avoid taking human civilization as some kind of standard or template. Most discussions of extraterrestrial intelligence seem to accept the implicit assumption that, with the age of space travel and radio astronomy, we ourselves have now crossed some threshold and become an “intelligent civilization.” Having achieved this state, we can begin to search for other intelligent civilizations. A Scientific American blog in February 2015 asked: “Is human-like, technological intelligence likely to be common across the universe?” This is the way the question is usually phrased. We discuss our own longevity, putting it so far at less than one hundred years, and we speculate that other technological civilizations must have achieved longevities of many thousands of years. So we tend to picture those more aged transmitting societies as a continuation, an elaboration, of what we are now. We think we are already one of them, just very young. We’re charter members of the Galactic Club, intelligent, radio capable, and ready to listen, and it’s just a matter of time before we graduate to becoming broadcasters. We take our own existence as proof that evolution can produce intelligence of the kind that can participate in interstellar conversation.
Yet there is inherent asymmetry in galactic radio discourse. It is much easier to listen than to transmit. A huge gulf yawns between the ability to build a radio telescope and the ability to mount a sustained multimillennial broadcasting and listening program. We cannot reasonably search for our equals. A serious SETI broadcast, the kind that could realistically be detected by young ones like us, would take a continuity and global unity of effort that is currently beyond us. We clearly have some, but not all, of the tools required for cosmic visibility. We can build fancy machines but are not quite capable of using them in any coherent, planetary-scale, long-term way. To succeed, SETI requires that more mature intelligent species will have developed not only machines that are more advanced than ours, but civilizations entirely different from what we have so far constructed. When you think it through, and you do the math, you realize that with SETI, we are not really searching for others of our own kind, but for evidence of something we hope to become. There is an aspirational aspect to the search.
Maybe the critical threshold, to the kind of intelligence that matters on a cosmic scale, is one that we haven’t crossed yet. In that case, what we seek is not a slightly more advanced version of ourselves, but something qualitatively different. To get there may require more of a transformation than simply a continuation. Many rivers to cross.
As we ponder the distinction, between a proto-intelligent society like ours that may not be ready or able to broadcast consistently or continuously, and those “wise ones” we are listening for, we might again consider a definition of intelligence that doesn’t assume we are at the pinnacle of evolution. What will those long-lived civilizations be like? They would have planetary intelligence: the ability to act coherently and intentionally, on a global scale, on projects that persist for many millennia.
This maps into the four kinds of planetary change I discuss in chapter 3. If you have built radio telescopes, you are employing clever technology and are clearly capable of planetary changes of the third kind. Yet to enact a sustained program of messaging for thousands of years on behalf of your planet’s inhabitants? That requires something else. This purposeful, long-form coherent activity would mean you are capable of planetary changes of the fourth kind. It would be a sign of true planetary intelligence. So any messages we receive will be from a civilization that has experienced the transition. No transition, no transmission.
As I discuss in chapter 5, we seem to be entering a bottleneck through which our increasingly powerful technology will either fairly soon (within the next couple of centuries) end the tenure of our civilization or ensure that, in some form, it survives for a long time—perhaps for much, much longer than the roughly ten thousand years since we started settling in villages. Our habits, honed for survival in the Holocene, are mismatched with the new threats we face in the Anthropocene. Perhaps civilizations elsewhere in the universe must all reach a point, similar to where we find ourselves now, when they are forced to confront the global implications of their actions. Is this an inevitable juncture for a young technical civilization? The specifics of the path will vary from planet to planet, but some waypoints could be the same. The universal nature of life (at least of nonintelligent life) is to expand, to exploit available resources, and to alter its environment. On planets where life becomes complex, evolution of intelligence may sometimes allow for the discovery and development of technology, which will accelerate these biological patterns, up to a point of excess and ecological crisis. If so, then early technological development will always cause unintended consequences and “global changes of the third kind,” and these will always force a reckoning and a choice: to face catastrophe or to develop a new kind of intelligence capable of exerting the planetary self-control needed to enact global changes of the fourth kind: what I am calling planetary intelligence.
Those who make it through the technical bottleneck will have emerged as a different kind of entity. They will have learned to apply global technology in concert with the functioning of their world, augmenting it in the service of life. They will have unimaginably powerful tools and understanding at their disposal, so natural disasters will have become avoidable. Once intelligent life gets to that point, it will have become a stable, integral part of the functioning of its home planet.
In chapter 5, I discuss the possibility that one outcome of the Anthropocene could be a transition to a new eon, the Sapiezoic, where a long-lived, sustainable technological civilization becomes a component of a planet for the rest of its existence. If we get through this bottleneck, then we will be fine for at least several billion years, until the Sun swallows Earth (and that gives us plenty of time to figure out what to do then, possibly going interstellar). If such a bottleneck is a universal challenge to young technical civilizations, this has interesting consequences for the meaning of L, the average longevity of civilizations. It implies there is a bifurcation of lifetimes. This means that the probability distribution of lifetimes is not a smooth, continuous function—like the probable lifetime of a human being, which peaks at average life expectancy and tails off at higher and lower ages—but, rather, a choice with two possible end states. Many, perhaps most, civilizations may be short-lived ones that don’t make it through, but those few (perhaps only an infinitesimal fraction) that do may be very long-lived indeed.
How long lived? Possibly immortal.
I call them quasi-immortal because we don’t know if the universe is going to last forever.* They would be “immortal for a while,” or until this universe ends. Even if most civilizations at our present stage are indeed doomed to self-destruct, this would not be at all incompatible with some small fraction making the transition to quasi-immortality.
This possibility was raised by Iosif Shklovsky back at Byurakan I, in 1964:
There is however, a possibility that some civilizations, having reached a highly advanced level, will find themselves past the inevitable crises and internal contradictions which plague the younger civilizations. The evolutionary time scale of these quiescent civilizations may be c
onsiderably longer, approaching the cosmogonic scale.
Shklovsky remarked on how incredibly strange it would be if the immortals did not exist:
I would like to stress that for me there could be no greater wonder than a conclusive proof that no “cosmic wonders” exist. Only an astronomer can fully grasp the true meaning of the fact that among the 1,000,000,000,000,000,000,000 stars comprising the visible part of the universe not a single one houses a sufficiently advanced civilization.
Frank Drake has long maintained that it is the immortals whom we are most likely to hear from with SETI. These immortals would be another kind of entity altogether, much more different from us than you are from a mite on your skin. It seems likely that, following Arthur C. Clarke’s famous dictum that “Any sufficiently advanced technology is indistinguishable from magic,” they would appear to us more like gods than highly capable engineers. Although it sounds like a crazy, techno-futurist fantasy, somewhat religious in its idealism, the more you think about the timescales available to evolution in the universe, and the accelerating pace of technology, the more you realize that the result of such a process must be beyond our ability to imagine. If you allow yourself to sit with the numbers, the idea of the immortals starts to make sense.
Technosignatures
We are in the very beginning stages of an era when we will be able to observe the atmospheres, and other qualities, of a large number of exoplanets. If some planets can reach a stage with stable world-changing intelligence, we should think about what that would look like. What if the current troubles of our civilization are really the adolescent growth pains beginning the transformation to true planetary intelligence? Earth’s Sapiezoic Eon may conceivably last for a significant portion of the planet’s existence. Some portion of the exoplanets we observe in the future will be considerably older than our solar system, and some may have biospheres where complex life arose more quickly than on Earth. So, we might discover planets where such a Sapiezoic transition occurred long ago. If there are any “Exo sapiens” out there, how would we spot one?
This gives us another way to think about the possible qualities of Earth in the Sapiezoic Eon. It also suggests a new approach to SETI, to complement our existing radio and optical searches. The “radio intelligence” search mode has been justified because it is pragmatic—it gives us something specific and well-defined to look for. Yet it may be that, with the discovery and investigation of exoplanets, we have opened up a new way to search for our cosmic company, one that does not require that aliens have any interest in contacting us. As we start to scrutinize exoplanets we should keep one eye, or one spectrometer channel, open for signs of worlds that do not seem “natural,” whether or not they are blasting galactic public radio in our direction. Obviously when we find planets that seem promising for life, we should check for radio waves or laser pulses. Yet we could also end up discovering intelligent life simply by finding the atmosphere of a managed planet. In astrobiology we talk a lot about how to identify “biosignatures,” the signs of life on another world that we could detect from afar. I suggest we also stay alert for technosignatures, or “noösignatures,” that is, signs of a noösphere, a sphere of intelligent influence. When we define biosignatures, we are forced to question which qualities of terrestrial life might be universal. Likewise, it is worth considering which observable aspects of technological civilization might be widespread, and how these might be discernable from “mere” biosignatures.
In the 1960s and ’70s, the SETI pioneers talked about looking for astrophysical “miracles,” the great works of astroengineering built by million-year-old civilizations who had progressed far beyond being simple planet shapers. Yet when SETI got started, even the idea of finding planets around other stars, as we have now done, was just a scientific fantasy. The notion of actually discovering what such planets were like must have seemed even farther off, almost akin to warp drive or teleportation—something that could almost conceivably be achieved by the science of a different time or civilization, but not by us. They didn’t know that fifty years later we would be starting to observe the atmospheres of exoplanets. And they also didn’t understand, in the visceral way we do now, the extent to which industrial civilizations alter atmospheres and climates. Now, more than half a century after Green Bank and Byurakan, this notion of world-changing civilizations feels a lot closer to home. We have become acutely aware that we are inadvertently altering a world, and we have no choice but to learn to engineer it to survive. The first task of this engineering project will be to stop our restless emissions and ecological wreckage. Yet it doesn’t stop there.
Arguably if our civilization is to survive, or give rise to one that will survive with technology, Earth will have to stay managed. It’s strange to say, but I think true, that from now on Earth will to some degree be a terraformed world. We are at a branching point, and it’s interesting to consider what the distant signature of a sustainably regulated planetary climate might be.
An evolving biosphere is complex, and defies prediction. Yet, as I have argued here, there are stages that may well be convergent, and therefore universal. Inhabitants of other worlds will probably have eyes and use light to see, so perhaps at some point they will light up their nights. Their atmospheres and surfaces will undergo rapid changes as they develop science and technology and “master” their worlds. Technological life, it has been proposed, will use energy in increasing amounts. Up to some point, that should be true, but what will happen when unrestrained technical cleverness encounters planetary limits? Whatever path it takes, successful life, at its core, is homeostatic, self-stabilizing. So intelligent aliens will find ways to transcend the environmental limitations and vicissitudes of an unaltered planet. They will engineer their worlds.
The obvious first thought is “Let’s look for industrial air pollution, for global warming, for marked increases in CO2.” Yet it is extremely unlikely that we would see this. As with radio SETI, the math argues that it is nearly impossible to find anyone at our stage. Yes, fossil fuel deposits on planets with photosynthesis do seem quite plausible. But, even if we surmise that other civilizations will arise somewhat in parallel with ours and encounter the same problems, an age of rampant pollution is inherently self-limiting and has got to be brief. Any planetary civilization we have a chance to find would have long moved on, and would be altering their world in ways that are compatible with long-term coexistence.
Planetary changes of the third kind would be the hardest to find elsewhere because they can’t last. A planet experiencing such a phase must be very rare, like an animal going through some quick molting or metamorphosis, and you’d have to be very lucky to catch one. This inadvertent stage will either be terminal, or a gateway to a long-lived phase where sentience becomes part of the way a planet functions.
How might we identify such Exo sapiens? We can imagine how we ourselves would terraform worlds, or mitigate natural hazards on a future Earth. For example, as I’ve discussed, in the future we will likely choose to dampen down the Milankovič cycle climate oscillations. If our descendants are still here and want to maintain their civilization, let alone a thriving biosphere, they will intervene to stop future ice ages and, eventually, prevent the Venus-style runaway greenhouse that will despoil an Earth left to its own devices. It’s hard to imagine such a significant global engineering effort that wouldn’t in some way be detectable at interstellar distances. If we find an exoplanet with a strange climate that is being controlled by unexpected atmospheric compounds such as chlorofluorocarbons, that should get our attention. Or if we find a world with a suspiciously unusual pattern of albedo (reflectivity) or day/night pattern of brightness, we might suspect planetary engineering with mirrors or surface alteration. We should take notice if such a world seems to be in a climate state that preserves or extends an earlier evolutionary stage, stabilizing against the aging of its star. These are just fun guessing games, though. We can’t really anticipate the choices of superadvanced intelligent al
iens. Yet we should stay alert for “unnatural” planetary states, and be prepared for surprises as we start to observe the properties of exoplanets.
If I am right that the kinds of planetary change I’ve outlined have any universal applicability, then there should be three kinds of exoplanets: dead, living, and sapient. Most of them will probably be dead. I think some will be living. These will, I predict, be fairly obvious when we find them. Certainly our own biosphere would be. From afar, the most noticeable feature of our planet is still that ridiculous surplus of oxygen in the air. So arguably, up to this point, the ancient cyanobacteria have been more effective than humans at betraying our presence to aliens. They, at least, have sent an existence proof, a calling card of life, making our planet noticeable and interesting to distant astrobiologists. If we are lucky, some living worlds may be nearby enough to find with the telescopes and spectrometers we’ll build in the coming decades. Sooner or later we might also find one that is sapient.
Cosmic Optimism
I don’t know if we can become one of these quasi-immortal civilizations, but I like the idea that they exist. Part of the point of SETI has always been a search for answers about our own cosmic potential and destiny. If they are out there, it means that there may be hope for us. It means there is a solution to this puzzle of forging a healthy, long-term relationship between a planet and a technological civilization.
Earth in Human Hands Page 33
