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Study says there are 36 intelligent alien races in our galaxy

Published Jun 15th, 2020 9:12PM EDT
aliens in milky way
Image: NASA

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  • A new study calculates the number of intelligent alien civilizations likely to exist in the Milky Way.
  • The scientists believe there are roughly 36 intelligent civilizations in our galaxy.
  • The average distance to an alien civilization is calculated to be around 17,000 light-years.

As far as we know, humans are the only “advanced” civilization in the entire universe. That might not mean much, however, because we don’t possess the technology to observe the surface of planets outside of our own solar system, and we have only managed to even detect a tiny fraction of the worlds in our home galaxy, much less the rest of the universe.

Scientists have long tried to use math to calculate the probability that life exists somewhere other than Earth. The problem is that with just one single data point in the “life” column, it can feel more like a blind guess than an actual calculation. Now, researchers from the University of Nottingham have come up with what they believe is a reasonable guess for the number of intelligent civilizations in our galaxy, and it’s a bit of a shock.

The research, which was published in The Astrophysical Journal, attempts to simplify the mathematical reasoning for assuming that intelligent life exists somewhere other than Earth. It all comes down to the amount of time it took for intelligent life to take root here on Earth, which is estimated to be between 4.5 billion and 5 billion years.

Based on that figure, and accounting for the number of stars that are likely capable of supporting life on a planet in their orbit, the researchers suggest that there are roughly 36 active alien civilizations in the Milky Way alone. Woah.

“The classic method for estimating the number of intelligent civilizations relies on making guesses of values relating to life, whereby opinions about such matters vary quite substantially,” Tom Westby, first author of the study, said in a statement. “Our new study simplifies these assumptions using new data, giving us a solid estimate of the number of civilizations in our Galaxy.”

“The two Astrobiological Copernican limits are that intelligent life forms in less than 5 billion years, or after about 5 billion years—similar to on Earth where a communicating civilization formed after 4.5 billion years,” Westby says. “In the strong criteria, whereby a metal content equal to that of the Sun is needed (the Sun is relatively speaking quite metal rich), we calculate that there should be around 36 active civilizations in our Galaxy.”

That might sound ridiculous, but only until you consider the size of the Milky Way itself. Our home galaxy is huge, with estimates suggesting its diameter may be as wide as 200,000 light-years. It’s also estimated to be around 1,000 light-years thick, holding as many as 400 billion stars and an untold number of planets orbiting those stars.

With that in mind, 36 seems like a perfectly reasonable number. The scientists say that the average distance from one intelligent civilization to the next is likely around 17,000 light-years, meaning that even if there are dozens of alien civilizations in our galactic neighborhood, we’re not even close to being able to detect or contact them.