When will humans find intelligent extraterrestrial life?

Alien civilizations : 36 times intelligent life in the Milky Way

"There should be at least a few dozen active civilizations in our galaxy, assuming it will take five billion years for intelligent life to form on other planets," says Christopher Conselice of the University of Nottingham in the UK.

To arrive at this estimate, the astrophysicist's team initially assumed that intelligent life on other planets arises in a manner similar to that on earth. "The idea is to look at evolution on a cosmic scale," says Conselice.

As the researchers report in the specialist magazine "The Astrophysical Journal", there are 36 active communicating civilizations in the Milky Way.

For previous estimates, assumptions were made about the conditions under which life can arise. "But opinions about these framework conditions differ," says co-author Tom Westby. The new study simplifies these assumptions and provides a solid estimate of the number of civilizations in our galaxy.

Distance in space and time

On the one hand, the authors postulate a limit of five billion years before or after which intelligent life develops. It was about 4.5 billion years on earth. On the other hand, they say that the star system must be as rich in metal as the solar system.

How many civilizations currently exist depends heavily on how long they are active and send signals such as radio transmissions from satellites into space. If one takes the age of human civilization at this stage of development of around 100 years as a basis, the result is the number of 36 other intelligent technical civilizations.

The average distance to these civilizations is about 17,000 light years, a university statement quoted in the study cited. With today's technology it is therefore practically impossible to discover or contact them.

A radio signal would take around 17,000 years to complete the one-way trip. Spaceships should take a little longer. So far, the NASA “Voyager 1” probe is the most distant human-built object. Since it started in 1977, it has moved a good 22 billion kilometers from the sun. That corresponds roughly to 0.002 light years.

Bad signs

The search for extraterrestrial civilizations could also provide clues about the future of humanity, the authors say. "If we find that intelligent life is widespread, it would show that our civilization could exist for much longer than a few hundred years," says Conselice.

On the other hand, it is a bad sign if the search for other active civilizations remains fruitless. It is quite possible that humanity is the only civilization in the Milky Way. However, this calls into question their long-term survival.

"In search of extraterrestrial intelligent life, we discover our own future and our own fate, even if we don't find anything," says Conselice.

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