Astrophysicist Adam Frank frames Earth’s sustainability transgalactically
DOI: 10.1063/PT.5.8095
The University of Rochester astrophysicist and science popularizer Adam Frank sees a meaningful, and maybe portentous, linkage of exoplanets and astrobiology with planetary sustainability and climate science.
With his colleague Woodruff Sullivan of the University of Washington, Frank recently published “Sustainability and the astrobiological perspective: Framing human futures in a planetary context ” in Anthropocene. That scientific journal names itself with the term increasingly used for Earth’s present geological epoch, and accordingly says of itself that it “publishes peer-reviewed works addressing the nature, scale, and extent of the interactions” that people have with the planet. Frank elaborated on the Anthropocene article in an 18 January New York Times “Sunday Review” commentary headlined “Is a climate disaster inevitable?”
Earlier, in a 2013 Times commentary on science denial, Frank declared that scientists “must become fierce champions of science in the marketplace of ideas.” He’s a founder of NPR’s 13.7 blog , named for the age of the universe in billions of years and dedicated to the proposition “that scientists must engage in the public debate of what science can and cannot do.”
Science can extrapolate useful sustainability knowledge even from present astrobiological understanding, says the paywalled Anthropocene article. Its freely accessible abstract begins, “We explore how questions related to developing a sustainable human civilization can be cast in terms of astrobiology. In particular we show how ongoing astrobiological studies of the coupled relationship between life, planets and their co-evolution can inform new perspectives and direct new studies in sustainability science.”
Frank and Sullivan invoke the Drake equation , a formula for estimating the number of Milky Way galaxy civilizations whose electromagnetic emissions are detectable. Using it “as a vehicle to explore the gamut of astrobiology,” they write, “we focus on its most import [sic] factor for sustainability: the mean lifetime...of an ensemble of Species with Energy-Intensive Technology (SWEIT). We cast the problem into the language of dynamical system theory and introduce the concept of a trajectory bundle for SWEIT evolution.”
They summarize implications, discussing “how astrobiological results usefully inform the creation of dynamical equations, their constraints and initial conditions.” They engage three “specific examples of how astrobiological considerations can be folded into discussions of sustainability": "(1) concepts of planetary habitability, (2) mass extinctions and their possible relation to the current, so-called Anthropocene epoch, and (3) today’s changes in atmospheric chemistry (and the climate change it entails) in the context of pervious [sic] epochs of biosphere-driven atmospheric and climate alteration (i.e. the Great Oxidation Event).”
The Great Oxidation Event figures centrally in Frank’s message to the public. His Times commentary begins by asserting that because almost all of the Milky Way’s 300 billion stars have planets, there are lots of “chances for evolving intelligent, technologically sophisticated species.” He writes:
From the vantage point of this relatively new field, astrobiology, our current sustainability crisis may be neither politically contingent nor unique, but a natural consequence of laws governing how planets and life of any kind, anywhere, must interact.
The defining feature of a technological civilization is the capacity to intensively “harvest” energy. But the basic physics of energy, heat and work known as thermodynamics tell us that waste, or what we physicists call entropy, must be generated and dumped back into the environment in the process. Human civilization currently harvests around 100 billion megawatt hours of energy each year and dumps 36 billion tons of carbon dioxide into the planetary system, which is why the atmosphere is holding more heat and the oceans are acidifying. As hard as it is for some to believe, we humans are now steering the planet, however poorly.
Can we generalize this kind of planetary hijacking to other worlds? The long history of Earth provides a clue. The oxygen you are breathing right now was not part of our original atmosphere. It was the so-called Great Oxidation Event, two billion years after the formation of the planet, that drove Earth’s atmospheric content of oxygen up by a factor of 10,000. What cosmic force could so drastically change an entire planet’s atmosphere? Nothing more than the respiratory excretions of anaerobic bacteria then dominating our world. The one gas we most need to survive originated as deadly pollution to our planet’s then-leading species: a simple bacterium.
The Great Oxidation Event alone shows that when life (intelligent or otherwise) becomes highly successful, it can dramatically change its host planet. And what is true here is likely to be true on other planets as well.
But can we predict how an alien industrial civilization might alter its world? From a half-century of exploring our own solar system we’ve learned a lot about planets and how they work. We know that Mars was once a habitable world with water rushing across its surface. And Venus, a planet that might have been much like Earth, was instead transformed by a runaway greenhouse effect into a hellish world of 800-degree days.
By studying these nearby planets, we’ve discovered general rules for both climate and climate change. These rules, based in physics and chemistry, must apply to any species, anywhere, taking up energy-harvesting and civilization-building in a big way.
A University of Rochester press release about the Anthropocene paper quotes Frank’s observation that if life forms on exoplanets “use energy to produce work, they’re generating entropy. There’s no way around that, whether they’re human-looking Star Trek creatures with antenna on their foreheads, or they’re nothing more than single-cell organisms with collective mega-intelligence. And that entropy will almost certainly have strong feedback effects on their planet’s habitability, as we are already beginning to see here on Earth.”
An article at Vox also quotes Frank: “It’s a change in perspective. What we’re saying is that what our species is going through right now, from an astrobiology perspective, is probably not unique. It probably happens all the time—and we can learn from that.” The article adds: “If we looked at climate change as a predictable consequence of intelligent life—and a process that tends to follow specific patterns—we might be better equipped to figure out how to stop it.”
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Steven T. Corneliussen, a media analyst for the American Institute of Physics, monitors three national newspapers, the weeklies Nature and Science, and occasionally other publications. He has published op-eds in the Washington Post and other newspapers, has written for NASA’s history program, and is a science writer at a particle-accelerator laboratory.