• A pair of astrophysicists revealed new calculations that suggest we may be one of a just few dozen complex civilizations in the galaxy.
  • Since the 1960s, scientists have been using the Drake equation to estimate the probability to contacting extraterrestrial life in our galaxy.
  • According to the team's new calculations, our alien neighbors are likely 17,000 light-years away.

For centuries, scientists have explored the universe for cosmic clues as to whether we're alone in the universe. Now, new estimates suggest there could indeed be other active civilizations out there—but not many.

The Drake equation, introduced in the 1960s by the astronomer Frank Drake, is a formula many researchers use to estimate the probability that we might communicate with extraterrestrial civilizations in our galaxy, the Milky Way.

Drake's seven key variables, which range from how many habitable planets exoplanets there are in the galaxy to the amount of time over which intelligent life takes shape, are almost impossible to pin down. The formula acts more like a framework for the probability of finding life; previous estimates have ranged from zero to over a billion civilizations.

A pair of researchers from the University of Nottingham in the U.K.—working under the assumption it takes the same amount of time for life to evolve in the distant reaches of the galaxy as it did right here at home—have narrowed down that estimate to just 36 extraterrestrial civilizations.

"There should be at least a few dozen active civilizations in our galaxy under the assumption that it takes 5 billion years for intelligent life to form on other planets, as on Earth," astrophysicist Christopher Conselice explained in a press statement. The team dubbed this calculation the "Astrobiological Copernican Limit."

Using this calculation as a guidepost, the scientists charted multiple scenarios: One end of the spectrum is a weak scenario where it takes intelligent life no more than 5 billion years to form, and on the other end, there's a strong scenario where it takes intelligent life between 4.5 and 5.5 billion years to blossom.

According to the scientists' calculations for the strong scenario, there should be anywhere between four and 211 complex civilizations that have the ability to send signals out into the universe, with 36 being most likely. The closest of these complex civilizations ought to be around 17,000-light-years away from Earth, orbiting a low-mass M-type dwarf star.

But this doesn't bode well for our chances of connecting with distant extraterrestrials. Communicating over these distances is impossible with today's technology.

Not everyone buys the analysis, which was published June 15 in The Astrophysical Journal. Some researchers, according to the Guardian, are skeptical of the work. Oliver Shorttle of the University of Cambridge told the news organization that more factors need to be considered—such as how exactly life formed on Earth—before taking the new findings as fact.

So what could this mean for the future of life on Earth? The quest for life elsewhere in the universe will reveal insight into our own fate.

"If we find that intelligent life is common then this would reveal that our civilization could exist for much longer than a few hundred years," Conselice said. "[A]lternatively if we find that there are no active civilizations in our Galaxy it is a bad sign for our own long-term existence."

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Jennifer Leman

Jennifer Leman is a science journalist and senior features editor at Popular Mechanics, Runner's World, and Bicycling. A graduate of the Science Communication Program at UC Santa Cruz, her work has appeared in The Atlantic, Scientific American, Science News and Nature. Her favorite stories illuminate Earth's many wonders and hazards.