91原创

Human-caused climate change, ocean acidification and species extinctions may eventually threaten the collapse of civilization, according to some scientists, while other people argue that for political or economic reasons we should allow industrial development to continue without restrictions.

In a new paper, two astrophysicists argue that these questions may soon be resolvable scientifically, thanks to new data about the Earth and about other planets in our galaxy, and by combining the earth-based science of sustainability with the space-oriented field of astrobiology.

鈥淲e have no idea how long a technological civilization like our own can last,鈥� says 91原创 astrophysicist Adam Frank.听 鈥淚s it 200 years, 500 years or 50,000 years?听 Answering this question is at the root of all our concerns about the sustainability of human society.鈥�

鈥淎re we the first and only technologically-intensive civilization in the entire history of the universe?鈥� asks Frank. 鈥淚f not, shouldn鈥檛 we stand to learn something from the past successes and failures of these other species?鈥�

, Frank and co-author Woodruff Sullivan call for creation of a new research program to answer questions about humanity鈥檚 future in the broadest astronomical context. The authors explain: 鈥淭he point is to see that our current situation may, in some sense, be natural or at least a natural and generic consequence of certain evolutionary pathways.鈥�

To frame these questions, Frank and Sullivan begin with the famous Drake equation, a straightforward 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 鈥渉igh tech鈥� 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 鈥渓ocal鈥� region of the Cosmos.

鈥淭hat鈥檚 enough to start thinking about statistics,鈥� says Frank, 鈥渓ike what is the average lifetime of a species that starts harvesting energy efficiently and uses it to develop high technology.鈥�

Employing 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鈥� 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 鈥渁strobiological perspective鈥� casts sustainability as a place-specific subset of habitability, or a planet鈥檚 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?

We don鈥檛 yet know how these other life forms compare to the ones we are familiar with here on Earth. But for the purposes of modeling average lifetimes, Frank explains, it doesn’t matter.

鈥淚f they use energy to produce work, they鈥檙e generating entropy. There鈥檚 no way around that, whether their human-looking Star Trek creatures with antenna on their foreheads, or they鈥檙e nothing more than single-cell organisms with collective mega-intelligence. And that entropy will almost certainly have strong feedback effects on their planet鈥檚 habitability, as we are already beginning to see here on Earth.鈥�

鈥淢aybe everybody runs into this bottleneck,鈥� says Frank, adding that this could be a universal feature of life and planets.听 鈥淚f that鈥檚 true, 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?鈥�

As Frank and Sullivan show, studying past extinction events and using theoretical tools to model the future evolutionary trajectory of humankind鈥攁nd of still unknown but plausible alien civilizations鈥攃ould inform decisions that would lead to a sustainable future.