By combining the Earth-based science of sustainability with the space-oriented field of astrobiology, two astrophysicists are attempting to answer questions about humanity’s future in the broadest astronomical context.
In their paper, which appears in the journalAnthropocene, Adam Frank and Woodruff Sullivan (both from the University of Rochester) propose that climate change, ocean acidification, and species extinctions may be a natural and generic consequence of certain evolutionary pathways.
“We have no idea how long a technological civilization like our own can last,” says Frank. “Is it 200 years, 500 years or 50,000 years? Answering this question is at the root of all our concerns about the sustainability of human society. Are we the first and only technologically-intensive civilization in the entire history of the universe? If not, shouldn’t we stand to learn something from the past successes and failures of these other species?”
To frame these questions, Frank and Sullivan begin with the famous Drake equation, a formula used to estimate the number of intelligent societies in the universe. In their treatment of the equation, the authors concentrate on the average lifetime of a Species with Energy-Intensive Technology (SWEIT). Frank and Sullivan calculate that even if the chances of forming such a “high tech” species are 1 in a 1,000 trillion, there will still have been 1,000 occurrences of a history like own on planets across the local region of the cosmos.
Using dynamical systems theory, the authors map out a strategy for modeling the trajectories of various SWEITs through their evolution. The authors show how the developmental paths should be strongly tied to interactions between the species and its host planet. As the species’ population grows and its energy harvesting intensifies, for example, the composition of the planet and its atmosphere may become altered for long timescales.
Frank and Sullivan show how habitability studies of exoplanets hold important lessons for sustaining the civilization we have developed on Earth. This astrobiological perspectivecasts sustainability as a place-specific subset of habitability, or a planet’s ability to support life. While sustainability is concerned with a particular form of life on a particular planet, astrobiology asks the bigger question: what about any form of life, on any planet, at any time?
The authors propose that every intelligent species may run into this bottleneck, and that this could be a universal feature of life and planets. “If that’s true,” argues Frank, “the question becomes whether we can learn anything by modeling the range of evolutionary pathways. Some paths will lead to collapse and others will lead to sustainability. Can we, perhaps, gain some insight into which decisions lead to which kind of path?”
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