Adam Frank
Adam Frank is an astrophysicist and leading expert on the final stages of evolution for stars like the sun. His computational research group at the University of Rochester has developed advanced supercomputer tools for studying how stars form and how they die. A self-described “evangelist of science,” he is also committed to showing others the beauty and power of science, and exploring the proper context of science in culture.
Essay
Adam Frank, The Extraplanetary
We were never alone. At least when it comes to other planets in the galaxy, Earth has a lot of company. That recognition is a pivot point around which a new vision of the human future can turn. For more than two and half millennia human beings debated the existence of other planets orbiting other stars. In the 4th century BCE, Aristotle was sure that Earth was entirely unique in the Universe. Around the same time, Democritus was just as sure that Aristotle was wrong. In 17th century France, Bernard De Fontenelle argued that planets were common among the stars. At the start of the 20th century, English astronomer James Jeans believed they were extremely rare. Here in the early 21st century, however, we need neither the surety of opinions nor beliefs. The new science of Astrobiology has ended the ancient debate. We’ve discovered alien planets everywhere in the galaxy.
As humanity stands at the precipice of dangerously altering its own world, realizing the staggering abundance of “extra-solar” planets (exoplanets) is not a sterile bit of astronomical trivia. Instead, it offers a new vantage point for imagining a different kind of human culture on a climate changing world. This alternative design for the future has been called The Planetary. It is a foil to the “Globalism” of modern political economies which remain functionally blind to the Earth’s coupled systems of air, water, rock and, most importantly, life. Unlike the Global, the Planetary understands that all human societies are embedded deep within those coupled Earth systems and how our thriving depends on theirs. Unpacking the Planetary and its consequences for human culture is an ongoing endeavor across many domains of scholarship (as this volume demonstrates). In this essay I want to focus on my own fields of astrophysics and astrobiology. My purpose is to argue that the promise of the Planetary also requires the enlarged vision of the Extraplanetary. All those newly discovered planets are essential for the Planetary to take hold.
The difficulty that kept us from finding exoplanets for centuries was one of technology. Planets are faint compared to the stars they orbit. That means finding a distant planet is like looking from New York City all the way to Candlestick Park in San Francisco and picking out a firefly flitting around one of the stadium lights. But by 1995, new developments in telescope instrumentation allowed the discovery of the first planet orbiting a Sun-like star. At first, additional planets were slowly added to the list of discoveries. By 2010, however, new methods and instruments were bagging exoplanets wholesale. Within a few years astronomers had their first version of an exoplanet census. The “where” and the “what” of worlds across the galaxy had been answered and those answers changed how we saw the night sky.
When I began astrophysics graduate school in 1986 no one knew if any planets existed beyond the eight worlds which made up our solar system. Now the exoplanet census has shown us that every star you see at night hosts a family of worlds. It turns out planets are common as dirt. Even more important, however, were those special planets living in their star’s “habitable zone” (also known as the “Goldilocks zone”). The habitable zone is a band of orbits around the host star where water on a planet’s surface can remain liquid. Worlds too close to their star are so hot that surface water instantly boils away. Planets too far from their star are so cold that surface water remains permanently frozen. But worlds orbiting within the habitable zone can remain wet for billions of years. Since most scientists believe that water is the key for the formation of life, habitable zone planets are the holy grails of astrobiology. Thus, more important than finding that every star hosts a planet was the discovery that one in five of those stars hosts a habitable zone world.
This “exoplanet revolution” vastly increased the possibility for life in the Universe. But exactly how many worlds where life might have formed did this new science give us? In 2016 Woody Sullivan and I set out to answer this question and found there must be about ten billion trillion habitable zone planets in the visible Universe. That’s 1 with 22 zeros after it. The key feature of our result was that each one of these worlds represents an experiment nature has run in planets and the possibilities of life. These possibilities include the appearance of tool-building species like our own. Put it all together and the only way we humans are the first time a technological civilization has appeared in cosmic history would be if all of those ten billion trillion experiments failed and somehow ours alone succeeded. We are likely not the first technological civilization in the Universe. But the implications of all those planets reach even further.
If technological civilizations like ours have appeared before in cosmic history, then our dangerous moment of climate change may have played out before on other worlds. In a series of papers my collaborators and I showed that a changing climate is likely to occur on any world where a technological civilization begins harvesting energy for its projects. Using mathematical models of planetary evolution in the presence of an energy harvesting species we found that strong planetary feedback, i.e. alien “Anthropocene’s”, were common. If you draw vast energies from your planet and use it to build stuff, your planet will push back. Our models showed that subsequent evolution depended on the technological species being smart enough to collectively recognize their planetary impact. If they wanted to endure, they had to bring their “technosphere” back in line with a healthy biosphere. These results shed new light on the climate change we are facing. Our results were the first step in an “Astrobiology of the Anthropocene” that placed our current dilemma into its proper extraplanetary context. It demonstrated that planets and the life they create will evolve together wherever they appear in the Universe.
Beyond showing us our Anthropocene predicament in “light of the stars”, recognizing the ubiquity of exoplanets also changes the stance from which view our own place in the Cosmos. Even before we ask the question of if life might appear on any of those planets, we can first recognize how each of those worlds is a place. Each world is a location where stories are unfolding. Even without life we can be sure that on some of those planets there is, right now, snow drifting quietly across deep shadowed valleys, rain cascading down mountain slopes and oceans driving the crash of waves onto rocky beaches. If a planet has an atmosphere, it will have a climate. Climates evolve and change creating an astonishing diversity of places. Once the imagination takes hold of these possibilities, we recognize that even without life, a planet is nature’s way of turning sunlight into something interesting. And once life does appear all bets are off. There is no way to predict what direction a biosphere’s creative energies might take or how, via the Gaian process of co-evolution, it might reshape the trajectory of a planet for its own ends.
So why does any of this matter for the emerging cultural, political and economic “design” called the Planetary? The answer is, obviously, right there in the name. In the Planetary scholars considering how the human future will respond to the Anthropocene see a new way to conceive being human. Instead of living outside the “system of systems” that is the Earth, there is hope that the Planetary represents a path towards fitting us back into the biosphere. The Planetary’s central organizing idea is that every world must be seen as a single epistemic whole. Earth, the Planetary tells us, cannot be reduced to component parts like a machine. Instead, it must be recognized as a vast complex system operating via dense networks of feedback. The complex system that is human culture, politics and economy cannot ignore that fact.
The Earth alone, however, is not enough to fill out this vision. The new imaginative Universe humans must inhabit to bring the Planetary to fruition requires more. In “Down to Earth” Bruno Latour explored the question of why environmental movements failed to gain the needed traction to effect real political change. He correctly identified a key idea missing in the opposition between a disembodied view of the Earth as a fragile ball hanging in space and the myopic “localism” motivating retrenched populisms. The latter could not speak to people living with their daily concerns in the here and now. The former was cynically being used as a front by global billionaires to withdraw from the collective responsibilities of dealing with climate change. Bruno argued the alternative was “the terrestrial”, a recognition that we needed to “come down to earth”, to “land somewhere”. He was calling for a new imaginative map where the consequences of our individual lives and their stakes could be reframed.
The Planetary offers that reframing. But because it is a new kind of social cosmology it requires a new Universe to inhabit. That is why the Planetary requires the Extraplanetary. With so many worlds littered across the galaxy the Extraplanetary changes what we see every night as we stand under the stars. We become inhabitants of one of many worlds, even if we don’t yet know if any of those planets harbor life. Just as important, the decades-long search for life, just getting underway now, will play out just as the Planetary itself is emerging. This is how the Extraplanetary becomes the pivot point around which the Planetary can emerge as a new form of human self- conception.
The stars have always figured prominently in our mythologies and religion. They always mattered for how we imagine our place in the world and in our collective lives. Now we understand that the night sky isn’t just strewn with stars, it's rich with other worlds. That is why the Extraplanetary also matters. In light of the stars, in light of the expanded vision science has given us, the Extraplanetary becomes the fertile ground from which the Planetary can take root, grow and thrive bringing us all along with it.