The Milky Way could be harbouring many intelligent alien civilisations
According to a new study, there could be more than 30 civilisations capable of long-distance communication here in the Milky Way. Led by researchers at the University of Nottingham, they assumed that intelligent life not only exists off-Earth, but develops on other planets similarly to how it does on Earth. To estimate the number of intelligent civilisations in our galaxy, the team took into account two major ‘Astrobiological Copernican limits’ – conditions that such an ‘intelligent’ civilisation would depend on.
For one of these limiting factors, the researchers used Earth, where life began approximately 4.54 billion years ago, as an example. They assume that intelligent life most likely forms in less than 5 billion years. The second limiting criterion focused on stars. They estimate that a planet with intelligent life would orbit a star like our Sun. This Sun-like star would have “a metal content equal to that of the Sun… the Sun is relatively speaking quite metalrich,” said Tom Westby, an assistant professor at the University of Nottingham.
In addition to these two Astrobiological Copernican limiting criteria, the scientists factored in technological capability. The researchers figured that the number of ‘intelligent’ civilisations depends on technological prowess, specifically how long they have been sending out some sort of signal into space – anything from radio transmissions from orbiting satellites to television. Using our civilisation as an example for a potential extraterrestrial one, the researchers estimated that humans have been ‘technologically advanced’ for about 100 years.
“We calculate that there should be around 36 active civilisations in our galaxy,” said Westby. However, the average distance to these alien worlds would be approximately 17,000 light years – much too far for us to contact with existing technology.