The Fermi Paradox poses the perplexing question: if humans are not unique and civilizations may arise everywhere in the universe, why have we yet to discover anybody else? A new article offers a striking response. Even if tens of thousands of civilizations exist, they must live for thousands of years before they have an opportunity to communicate with someone else. To be honest, various worrying answers to the Fermi Paradox have been proposed, so waiting doesn’t sound that horrible.
Researchers Wenjie Song and He Gao calculated the number of communicating extraterrestrial intelligent civilizations (CETIs) out there using two parameters: the probability of life appearing on a terrestrial planet and the stage of evolution of the planet’s host star at which the CETI would be born, as reported in The Astrophysical Journal. CETIs were either infrequent or widespread in nine situations devised by the two researchers. If CETIs are uncommon (on the scale of 110 over the Milky Way), a communicative civilisation may have to wait 400,000 years for a signal from another, with about 43,000 CETIs, it would take at least 2,000 years for a communicating civilization to get its first cosmic greeting in their best-case scenario.
“It’s possible that we haven’t received a signal because human communication lifetimes are now insufficient. However, many potential disruptions, such as population issues, nuclear annihilation, sudden climate change, rogue comets, ecological changes, and so on, have been proposed that civilizations’ lifetimes are very likely self-limiting (known as the Doomsday argument), according to the authors of the paper from Beijing Normal University. “If the Doomsday argument is right, humanity may not receive any signals from other CETIs before extinction in some gloomy scenarios.”
In recent years, probabilistic alternatives to the Fermi paradox have been proposed, implying that our present search for alien civilizations is still quite restricted and may remain so. After all, if someone were hunting for us, they’d have to be in a pretty small part of the galaxy to pick up Earth signals. However, the scientists recognize that their odds are subject to large uncertainty, so there may be a possibility to interact with aliens sooner rather than later.
“The fraction of terrestrial planets that can give birth to life is rather unclear, and the process of life developing into a CETI and being able to transmit detectable signals to space is highly unexpected,” the scientists write. However, there is a strong possibility that there are just a few CETIs out there. Who knows whether they wish to communicate with us? Perhaps the dark woodlands theory is correct after all.
