More than 30 extraterrestrial civilizations may exist in our galaxy

In recent studies, scientists on the search for extraterrestrial life have found evidence to suggest that we will discover life beyond Earth in the next ten to 20 years. As more advanced missions are launched to study planets and stars, the chances of finding signs of extraterrestrial civilizations are better now than ever before. 

It is challenging to calculate the number of potential extraterrestrial civilizations, but a new study led by the University of Nottingham has taken a unique approach to obtain this estimate. According to the researchers, there could be more than 30 communicating civilizations within our own galaxy.

“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,” said study lead author Professor Christopher Conselice. “The idea is looking at evolution, but on a cosmic scale. We call this calculation the Astrobiological Copernican Limit.”

The two Astrobiological Copernican limits are that intelligent life forms in just under or just over 5 billion years. On Earth, a communicating civilization formed after 4.5 billion years. 

“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,” said first author Tom Westby. “Our new study simplifies these assumptions using new data, giving us a solid estimate of the number of civilizations in our galaxy.”

“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.”

The researchers explained that if other technological civilizations last as long as ours, which is currently 100 years old, then there should be about 36 active high-tech civilizations throughout our galaxy.

The average distance to one of these potential civilizations is 17,000 light-years, which means it would be very difficult to detect any active signals such as radio or satellite transmissions. Furthermore, if extraterrestrial civilizations do not survive as long as ours has, we may be the only intelligent life in our galaxy. 

“Our new research suggests that searches for extraterrestrial intelligent civilizations not only reveals the existence of how life forms, but also gives us clues for how long our own civilization will last,” said Professor Conselice. 

“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, alternatively if we find that there are no active civilizations in our galaxy it is a bad sign for our own long-term existence.”

“By searching for extraterrestrial intelligent life – even if we find nothing – we are discovering our own future and fate.”

The study is published in The Astrophysical Journal.

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By Chrissy Sexton, Earth.com Staff Writer