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 \u201chigh tech\u201d 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 \u201clocal\u201d region of the Cosmos.<\/p>\n
\u201cThat\u2019s enough to start thinking about statistics,\u201d says Frank, \u201clike what is the average lifetime of a species that starts harvesting energy efficiently and uses it to develop high technology.\u201d<\/p>\n 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\u2019 population grows and its energy harvesting intensifies, for example, the composition of the planet and its atmosphere may become altered for long timescales.<\/p>\n Frank and Sullivan show how habitability studies of exoplanets hold important lessons for sustaining the civilization we have developed on Earth. This \u201castrobiological perspective\u201d casts sustainability as a place-specific subset of habitability, or a planet\u2019s 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?<\/p>\n We don\u2019t 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.<\/p>\n \u201cIf they use energy to produce work, they\u2019re generating entropy. There\u2019s no way around that, whether their human-looking Star Trek creatures with antenna on their foreheads, or they\u2019re nothing more than single-cell organisms with collective mega-intelligence. And that entropy will almost certainly have strong feedback effects on their planet\u2019s habitability, as we are already beginning to see here on Earth.\u201d<\/p>\n \u201cMaybe everybody runs into this bottleneck,\u201d says Frank, adding that this could be a universal feature of life and planets.\u00a0 \u201cIf that\u2019s 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?\u201d<\/p>\n As Frank and Sullivan show, studying past extinction events and using theoretical tools to model the future evolutionary trajectory of humankind\u2014and of still unknown but plausible alien civilizations\u2014could inform decisions that would lead to a sustainable future.<\/p>\n![\"Schematic](\"https:\/\/www.rochester.edu\/newscenter\/wp-content\/uploads\/2014\/11\/figure-4-630x384.png\")
shows a trajectory representing population collapse. Blue
line shows a trajectory representing sustainability. Credit: Michael Osadciw\/University of Rochester<\/figcaption><\/figure>\n![\"\"](\"https:\/\/www.rochester.edu\/newscenter\/wp-content\/uploads\/2014\/11\/figure5-630x491.png\")
![\"Portrait](\"https:\/\/www.rochester.edu\/newscenter\/wp-content\/uploads\/2020\/06\/2018-06-04_Adam_Frank_063-3-2-165.jpg\")
<\/p>\n<\/div>\n<\/div>\n