New estimate suggests alien civilizations in the Milky Way are incredibly rare

Eight.

That is the number of intelligent, communicating extraterrestrial civilizations that two astronomers at the University of Nottingham believe could exist in the Milky Way, our home galaxy.

A new study published in the Astrophysical Journal on Monday provides an updated estimate of the likely number of extraterrestrial civilizations that could exist in the Milky Way. The analysis, performed by astronomers Tom Westby and Christopher Conselice, begins by revising the Drake equation, a formula Frank Drake proposed in 1962 to estimate how many worlds are likely to host intelligent life in our galaxy. The equation is based on a variety of factors, including how often sun-like stars form in the galaxy, how many stars are orbiting planets, and how often life evolves and becomes intelligent enough to recognize.

But as it is, the Drake equation is fundamentally “unsolvable” and contains an important variable that we only know when we find intelligent life: How long can foreign civilizations be proven on average?

“The classic method of estimating the number of intelligent civilizations is based on guessing values ​​related to life,” Westby said in a press release. “Our new study simplifies these assumptions using new data and gives us a solid estimate of the number of civilizations in our galaxy.”

Westby and Conselice started the Drake equation, but approached the search for so-called “Communicating Extra-Terrestrial Intelligent” civilizations in a somewhat different way. They incorporated a key assumption into their estimate: life on another planet will arise in a similar way to that on Earth.

In fact, this means that their revised equation takes into account the idea that a planet must exist in the habitable zone around a star for about 5 billion years before it can develop intelligent life with the ability to communicate across the universe. The duo set three different boundaries for this “suitable planet” that houses life with weak, moderate and strong categories with different time frames for the emergence of life.

The weakest limits allowed them to make estimates for more than 5 billion years, while the strongest limits only rated worlds between 4.5 and 5.5 billion years.

If you put the strongest limits and numbers into their complex new equation, which they called the CETI equation, the data shows that there could be at least eight CETI civilizations in the Milky Way. Such an estimate is relatively close to the number 10 that the famous astronomer Carl Sagan found while discussing the Drake equation in the Cosmos science show from the 1980s.

There is a catch: these worlds are at least 7,000 light years away – which makes it almost impossible for us to contact them. The team estimated that we have to actively search for signals from space for about 6,300 years before we can get messages from another civilization.

“It is clear that the lifespan of a communicating civilization is the key aspect of this problem,” the authors write.

On the other hand, Westby and Conselice, using weaker limits, suggest that there could be up to 2,900 worlds in which life has found a way that means we may be able to recognize them earlier.

However, what remains of the study on humans is somewhat bleak: In our cosmic hide-and-seek game with other lives, we have just “ready or not, here I come!” Called. and we’ve taken a couple of preliminary steps in our search. But if we want to win the game, civilization has to to survive a long time to uncover the hiding places of other life in the universe. And if we can’t find an intelligent life nearby, it may not be a good sign of our long-term survival.

“If we found intelligent life to be common, it would show that our civilization could exist for much longer than a few hundred years,” said Conselice. “Alternatively, if we find that there are no active civilizations in our galaxy, it is a bad sign of our own long-term existence.”

Although this is an interesting new way to examine an age-old question, the work is based on many assumptions. The authors make it clear that there is only one data point for intelligent, communicating life, namely humanity. If we use ourselves as the basis for other life in the cosmos, it can be faulty itself, because in truth we simply don’t know what other intelligent life looks like or where it could thrive.

As with the Drake equation, the CETI equation provides a framework to examine the life chances in our galaxy and to discuss the likelihood that we might soon hear from extraterrestrials.

“By searching for extraterrestrial intelligent life – even if we can’t find anything – we discover our own future and destiny,” said Conselice.

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