Milky Way might have 36 intelligent civilisations — but humans are unable to communicate with them

• There could be 36 active intelligent civilisations in our own galaxy, the Milky Way, but we are unable to communicate to them because the average distance to these civilisations would be 17,000 light-years away, new research has said.
• According to researchers, 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.

There could be 36 active intelligent civilisations in our own galaxy, the Milky Way, but we are unable to communicate to them because the average distance to these civilisations would be 17,000 light-years away, new research has said.

According to researchers, 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.

"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 Christopher Conselice, professor of astrophysics at the University of Nottingham.

"The idea is looking at evolution, but on a cosmic scale. We call this calculation the Astrobiological Copernican Limit," he added.

It is also possible that we are the only civilization within our Galaxy unless the survival times of civilizations like our own are long, said the study led by the University of Nottingham published in The Astrophysical Journal.

"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," explained first author Tom Westby.

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.

"Our new study simplifies these assumptions using new data, giving us a solid estimate of the number of civilizations in our Galaxy," said Westby.

The number of civilizations depends strongly on how long they are actively sending out signals of their existence into space, such as radio transmissions from satellites, television, etc.

If other technological civilizations last as long as ours which is currently 100 years old, then there will be about 36 ongoing intelligent technical civilizations throughout our Galaxy.

"Our 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 Conselice.

If researchers 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 authors wrote.