Study uses astrobiology to estimate how many civilizations with technology to communicate exist in our galaxy
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One of the largest and oldest questions in human thought history is whether there are other intelligent life forms in the universe. Getting good estimates of the number of potential extraterrestrial civilizations, however, has been very challenging.
A study led by the University of Nottingham (UK) and published today (June 15th) in the journal “The Astrophysical Journal” took a new approach to this issue.
Starting from the assumption that intelligent life forms on other planets are similar to those on Earth, researchers estimated the number of intelligent and communicative civilizations in the Milky Way. They estimate that there could be more than 30 intelligent civilizations capable of communicating active in our galaxy.
Christopher Conselice, a professor of astrophysics at the University of Nottingham and the research leader, explained, “There should be at least a few dozen active civilizations in our galaxy, assuming it takes 5 billion years for intelligent life to form on other planets, just as on Earth.” Conselice also said, “The idea is to look at evolution, but on a cosmic scale. We call this estimate the astrobiological Copernican limit.”
The study’s lead author, Tom Westby, said, “The classic method for estimating the number of intelligent civilizations is based on guessing values related to life, where opinions on these matters vary substantially. Our new study simplifies these assumptions using new data, providing a solid estimate of the number of civilizations in our galaxy.”
Signals to space
Westby continued, “The two astrobiological Copernican limits are intelligent life forms in less than 5 billion years or after about 5 billion years — similar to Earth, where a communicative civilization formed after 4.5 billion years. In strong criteria, requiring metal content equal to that of the Sun (the Sun is relatively metal-rich), we estimate that there should be about 36 active civilizations in our galaxy.”
The research shows that the number of civilizations heavily depends on how long they are actively sending signals of their existence into space, such as radio broadcasts from satellites, television, etc. If other technological civilizations last as long as ours, which is currently 100 years old, there will be about 36 ongoing technical intelligent civilizations in our galaxy.
However, the average distance to these civilizations would be about 17,000 light-years away, making detection and communication with our current technology difficult. It’s also possible that we are the only civilization within our galaxy unless survival times for civilizations like ours are long.
Conselice said, “Our new research suggests that the search for intelligent extraterrestrial civilizations not only reveals how life forms but also gives us clues about how long our own civilization will last.
If we believe that intelligent life is common, it would indicate that our civilization could exist for much longer than a few hundred years; alternatively, if we find out that there are no active civilizations in our galaxy, it’s a bad sign for our long-term existence.
In searching for intelligent extraterrestrial life — even if we find nothing — we are discovering our own future and destiny.”
