Light of the Stars Read online

  Beyond the question of the average lifetime, we could also use the models to see exactly what choices are most likely to save us. Once we have a full suite of trajectories, we can ask what explicitly led some to civilizations to achieve planetary sustainability and others to collapse. Like a doctor looking for a cure by studying the most pathological cases of a disease, we can see what common factors drove the civilizations that died to their fate. The models will have a lot to teach us that we can’t see now with the tunnel vision of just our planet and just our own uncertain future.

  CHAPTER 6

  THE AWAKENED WORLDS

  THE PLANET WE NEED

  If, over the course of billions of years of cosmic evolution, some species make it through their Anthropocene into long-term, sustainable versions of civilization, what do they end up with? What do their planets look like? How do these worlds function in terms of their coupled systems of air, water, rock, life, and the new addition of a planet-spanning, technology-intensive, energy-hungry society? These are the questions we care about most, because this is the target we must aim for.

  There is a great deal of wishful thinking involved when the terms planetary and sustainability are parked next to each other. These are visions of “green utopias,” with sleek, electric-powered trains gliding into elegant eco-cities of vertical farms and buildings mimicking natural forms. While it’s easy to imagine what a single sustainable city might look like, imagining a sustainable planet is another thing entirely. Cities have always been the domains of human control. They are spaces our project of civilization carves out of nature. A planet, however, is a different beast.1

  Planets are their own masters. That’s what the astrobiological perspective shows us. The processes shaping worlds are powerful, complex, and subtle. Planets channel vast energies through ever more refined networks of cause and effect. These networks are embodied in winds that pick up fine dust grains and carry them across thousands of miles, or chemical compounds blown into the air by volcanoes, only to end up, millions of years later, embedded in rocks lying deep beneath oceans. Add life to the mix, and planets become almost infinitely more complex, as the planetary systems can now include a coevolving biosphere.

  So, how does a healthy planet with a healthy, long-term project of civilization work? To answer this question, we must take our investigation to the final level. Crossing to the safety of a fully sustainable project of civilization on Earth requires not just thinking like a planet, but understanding the profound consequences of planets that have themselves learned to think through their civilizations. What, in other words, does it mean for a planet as a whole to wake up?

  THE RUSSIAN MEETING

  Ten years after their famous encounter at Green Bank, Frank Drake, Carl Sagan, and two other members of the original meeting found themselves together again. This time, the setting wasn’t the forests of West Virginia, but a mountain in Armenia. Drake and his compatriots, along with a squad of Russian scientists, had come to the Byurakan Observatory for the first true intraplanetary (or international) meeting on interplanetary civilizations.2 While Green Bank had been an intimate affair, with just nine members, the 1971 Byurakan Observatory meeting had more than forty participants, including luminaries from both the Soviet and American scientific establishments. There were Nobel laureates like Francis Crick (co-discoverer of DNA) and Charles Townes (inventor of the laser). Other notables included artificial-intelligence pioneer Marvin Minsky and Canadian neurophysiologist David Hubel, who would go on to win a Nobel Prize for his brain studies.3

  Carl Sagan played a central role in organizing the Byurakan meeting. At the height of the Cold War, Sagan understood the symbolic value of an international conference devoted to our place among other, hopefully more mature, civilizations. Getting the meeting placed in the Soviet Union, the United States’ bitter enemy, had been no small task, however. To pull it off, Sagan needed a partner on the Russian side who was just as charismatic and passionate about life in the universe as he was. He found that counterpart in Nikolai Semenovich Kardashev.

  Carl Sagan (right) with Armenian astronomer Hrant Tovmassian (center) and other participants at the first international SETI meeting at the Byurakan Observatory in Armenia in 1971.

  Just a year and a half older than Sagan, Kardashev was a radio astronomer who had already made important contributions to the study of galaxies and the interstellar medium.4 He had been the force behind the first Soviet search for exo-civilizations, carried out just a few years after Project Ozma. He’d also led the Soviets’ first internal SETI conference in 1964, a few years after the Green Bank meeting. The report he had written on that meeting established his international reputation as a leading thinker about life and the evolution of other worlds.

  In that paper, Kardashev laid out a scheme for the technological progress of exo-civilizations. His ideas played an important role in the Byurakan meeting, where freewheeling discussions of the long-term fate of civilizations went on until the small hours of the night. But the impact of what came to be called the Kardashev scale would last beyond the Byurakan meeting and would, in its way, prove to be as enduring as the Drake equation.5

  THE KARDASHEV SCALE

  When Nikolai Kardashev proposed his scale for measuring the progress of civilizations, he was primarily interested in finding them. Kardashev’s question can be rephrased in a straightforward way: What are the milestones that mark a civilization’s advancement up the ladder of technological sophistication? The basic idea that civilizations evolve through distinct, quantifiable stages as they progress offered Kardashev a lever to lift the discussion about exo-civilizations above pure speculation by providing a means to quantify their advancement. While his main interest was finding radio signals from exo-civilizations, his scale gave us a way to think about their evolution. But within the Kardashev scale lay an essential and mistaken bias concerning the relationship between civilizations and their host planets. Correcting that bias is an essential step in finding a wise astrobiology-based path through the Anthropocene.

  Kardashev based his classification scheme on the energy a civilization had at its disposal. The scale had three levels.

  •Type 1: These civilizations can harvest the entire energy resources of their home planet. In practice, this means capturing all the light energy that falls on the world from its host star, since stellar energy will likely be the largest source available on a habitable-zone planet. The Earth receives the equivalent of thousands of atomic bombs’ worth of energy from the Sun every second.6 A Type 1 species would have all this power at its disposal for civilization building.

  •Type 2: These civilizations can harvest the entire energy resources of their home stars. The total output of the Sun every second is a billion times larger than the sunlight that falls just on Earth. The physicist Freeman Dyson anticipated some of Kardashev’s thinking in a paper written in 1960, in which he imagined an advanced civilization constructing a vast sphere around its star.7 This solar system–sized machine would capture stellar light energy, perhaps via an inner surface covered in solar cells. Such “Dyson spheres” became the archetype for scientists imagining how a Kardashev Type 2 civilization would go about its energy-harvesting business.

  •Type 3: These civilizations harvest the entire energy resources of their home galaxy. A typical galaxy contains a few hundred billion stars. Perhaps Type 3 civilizations envelop all their galaxy’s stars within Dyson spheres, or perhaps they have even more exotic technologies at their disposal.

  The Kardashev scale represents the scientific imagination working at the grandest, and therefore most mythic, scale. A single Dyson sphere would be a machine of staggering capacity and size. The inner surface of a Dyson sphere built around the sun, with a radius the size of Earth’s orbit, would cover more than ten thousand trillion square miles (the equivalent of almost a billion Earths). Building a machine of this size would require grinding up whole planets for construction materials. We won’t be building one of these anytim
e soon. Dyson spheres are truly the stuff of science fiction.

  But by focusing on stellar-energy capture as the yardstick for a civilization’s evolution, Kardashev’s science fiction–sounding evolutionary scheme could be set firmly in the real world of real physics. That is what gave the Kardashev scale its reach, and why it has endured. For example, a number of researchers, such as Jason Wright at Penn State University, have conducted astronomical searches for the radiation signatures of Type 2 civilizations via their Dyson spheres.8 Thus, as astronomer Milan M. Cirkovic wrote in 2015, “Kardashev’s scale remains the most popular and cited tool for thinking about advanced extraterrestrial civilization.”9

  A large part of the appeal of the Kardashev scale lies in its combination of science and mythic-scale optimism via a technologically coherent road map for the progress of civilizations. Its implications are undeniably hopeful. If we continue to advance as a technology-building species, we should naturally pass through each Kardashev type on our way to a future of unimaginable power and reach. A civilization that could build a Dyson sphere would be the equivalent of technological demigods to us. In physics, power is defined as energy used per time. Since the Kardashev scale is explicitly based on energy use, the links between a civilization’s physical power and its metaphorical power—between the science and the mythic—are baked into the scale’s application. Make it far enough, the scale tells us, and you will become as the gods.

  More than one author has tried to calculate where on the Kardashev scale human civilization falls today. In 1976, Carl Sagan suggested a way of calculating “fractional” values of Kardashev status based on world energy production.10 In Sagan’s calculation, we end up at about Type 0.7. Freeman Dyson went further, suggesting that human civilization will reach full Type 1 status in approximately two hundred years (with Type 2 requiring another hundred thousand to one million years).11

  That sounds pretty good. In just a couple of centuries, we are going to become a true Type 1 cosmic civilization. The problem, of course, is that we may never get there. Our project of civilization has a bottleneck to navigate right now, and our progress through it is anything but assured.

  The Kardashev scale originated from a particular historical moment in thinking about exo-civilizations. Like Sagan and Drake, Kardashev was raised on a techno-utopian vision of the future. Technology was imagined in terms of sleek, gleaming machines that were destined to be humanity’s salvation. We could expect that technology’s growth and power would be unconstrained. That was why the Kardashev scale focused solely on energy. Civilizations were expected to rise up the ladder of energy harvesting to ever-greater heights until the entire galaxy would become a resource to be mined. And at each stage (each Kardashev type), the feedback from all this energy use on the physical systems from which the energy was drawn could be ignored. Planets, stars, and galaxies would all simply be brought to heel.

  While it is possible that stars and galaxies might not care what you do with their energy, planets are another story. That is the painful lesson of the Anthropocene.

  The engineering of entire solar systems or galaxies is so far into the realm of speculation that it’s impossible to know what challenges it will require. But for planets—the focus of Type 1 civilizations—we already understand enough to see how the Kardashev scale represents a kind of planetary brutalism. It inherits a vision of advanced civilizations living in perfect, world-girdling cities where nature is fully controlled. Science fiction is full of this kind of thing. There is Trantor, the home world of the galactic empire in Isaac Asimov’s classic Foundation trilogy. Trantor’s surface lies hundreds of miles below the many shells of machinery that make up its single planet-scale city.12 A more recent example is Coruscant, the home world of the galactic republic in Star Wars, with its continuous stream of “air cars” traveling amid the city’s towering spires. These are visions of planets conquered by the mighty energy-wielding capacities of their civilizations.

  But in the years since Kardashev proposed his classification system, we have learned the hard way that planetary biospheres are not so easily ignored. From the work of Lovelock, Margulis, and others, a new scientific understanding of planets and life emerged. Even when they lack life, we now know planets are complex systems. And if a vibrant biosphere is present, it becomes part of that complex whole. The living and non-living parts of the system coevolve across time. In this way, the coupled systems that make up a planet have their own internal dynamics—their own logic. That logic must be fully embraced when mapping out the trajectories of civilizations, as Kardashev hoped to do.

  Once again, we are forced to stop seeing civilizations like our own as standing apart from the world that gave them birth. All civilizations, including those that might occur on other worlds, are expressions of their planet’s evolutionary history. From this perspective, our project of civilization is just one consequence of the Earth’s history, not its future master. Every civilization must be seen as a new form of biospheric activity arising within a planet’s history of transformation and evolutionary innovation.

  So it is not simply energy consumption (the focus of the Kardashev scale) that must be considered. Instead, we must learn to think in terms of energy transformations. We need to look at those physical laws that constrain energy as it flows through a planetary system. This means we must take a fully thermodynamic perspective as we follow the energy of sunlight being turned into the energy of rising air columns, which turns into the energy of falling rain, and so on, all the way to the energy of living cells.

  Recognizing the limits on energy transformation is the fundamental lesson of the Anthropocene. You can’t just bring a planet to heel, meaning you can’t use energy to build a civilization without expecting feedback. Instead, we must begin with a richer understanding of biospheres and civilizations as part of the coupled planetary systems. That means a new kind of map for how civilizations rise to the Type 1 stage and, possibly, survive long enough to become something more. The development of long-term, sustainable versions of an energy-intensive civilization must be seen on a continuum of interactions between life and its host planet.

  Sustainable civilizations don’t “rise above” the biosphere, but must, in some way, enter into a long, cooperative relationship with their coupled planetary systems. But what does that look like?

  EARTH AS A HYBRID PLANET

  Planets are nature’s way of turning starlight into something interesting. The evolution of a planet across billions of years depends on which processes it can harness to absorb starlight and, by doing work, transform that energy into something else. From rainstorms to forests to civilizations, the story of planetary evolution across cosmic time is the story of these energy transformations.

  Energy flows are the domain of thermodynamics. The engine in your car is a thermodynamic system. It’s a “heat engine.” Gasoline gets ignited in the cylinders, converting chemical molecular-bond energy into hot gas, or heat energy. The hot, expanding gas pushes on the pistons, converting heat into motion via kinetic energy. The motion of the pistons gets transferred though the gears into the motion of the wheels.

  So, it’s not just the energy in the gas tank that matters. It’s the transformation of that energy from chemical form into kinetic form that you need to pay attention to. Some of that original chemical energy gets dissipated (meaning it’s lost and can’t help in doing the work of moving the car) through the heating of the engine block or the friction of the tires on the road.

  The science of thermodynamics tells us about the limits of those transformations. It tells us that not all the initial energy (contained in the fuel in the gas tank, for example) can be used to do useful work. Some of it, by necessity, must turn into “waste.” Nature has built these limitations into the universe through the laws of thermodynamics.13 That is why thermodynamics is the right way to think about planets and civilizations and their combined fate.

  For a planet with no atmosphere, like Mercury, the available ener
gy transformations are pretty limited. Sunlight hits Mercury’s surface. The surface warms up and emits heat radiation back into space. Once the planet’s surface reaches its equilibrium temperature, there is not a whole lot more to the story, which is why Mercury has looked pretty much the same from one day to the next for the last three billion years or so.14

  Add an atmosphere to the planet, however, and the story gets a lot more interesting. When sunlight warms the surface of a planet with an atmosphere, the air near the ground is also warmed. Then the air rises, creating large-scale “convective” circulation. Atmospheric gas rises, and then cools and falls back toward the surface to start the circulation over again. Atmospheric convection is a kind of planetary heat engine, converting sunlight into motion.

  If the atmosphere also includes molecules like water, CO2, and other “volatiles,” then evaporation and condensation can occur in the circulation.15 Water, for example, will evaporate near the planet’s surface, turning into a gas that rises with the rest of the air. When the air cools at higher altitudes, the water condenses back into a liquid (in the form of droplets). This is how interesting things like rain or snow can occur—things that could not happen on an airless world.

  Just these ingredients—an atmosphere with stuff that can evaporate and condense—are enough to give a planet climate and weather. It’s why even a relatively “dead” world like Mars can still look different from one day to the next, as dust storms, fog, or frost roll in and out.

  The presence of liquids flowing across the surface, in the form of rain runoff and rivers, adds a new layer of “interesting,” as the strong weathering of rocks can begin. Elements once locked up in minerals get exchanged with the air and the surface liquids, launching “cycles” of these materials between the planetary systems.16 The branching pathways of these cycles and their feedbacks bestow a new richness to the planet, allowing it to evolve in even more complex ways.