There's a very simple reason why scientists don't think humans will ever meet aliens

Will humans ever make contact with aliens?

Following the release of Pentagon footage which shows suspected UFOs, lots of people have been asking this question.

A new “UFO sighting” video seems to go viral on social media every other week, but as coronavirus keeps us all inside, thoughts of the universe beyond our homes (and even beyond our planet) seems to be on peoples' minds.

So it's worth remembering a 2018 study which dashed the hopes of people who are desperate to meet aliens in their lifetime.

Scientists claimed that, if we ever do find a signal from an advanced alien civilization, those aliens are likely to be dead by the time we hear it.

The study, which came to a rather depressing conclusion, examined how long civilisations might live for and how far away from Earth they are likely to be.

It is thought there could be between 20 and 40 billion Earth-sized worlds in the Milky Way with habitable conditions. Yet we don't know how many have spawned life.

What makes discovering these civilisations difficult is their short lifespan. Astronomer Frank Drake estimated in 1961 that the lifetime of Earth-like civilisations ranges from 106 to 12,100 years or more. Considering humans have only covered 0.001 per cent of the Milky Way with signals in 80 years, it is unlikely that a civilisation under 100,000 years old will still exist by the time we receive a signal from them.

Study leader Claudio Grimaldi, of the Federal Polytechnical School of Lausanne in Switzerland, concluded:

If the civilization emitted from the other side of the galaxy, when the signal arrives here, the civilization will already be gone.

The study notes that when a civilization stops emitting signals, their signals will likely continue travelling out in an echo. While it might be possible to spot these, the odds of finding a living civilisation are slim.

The transmissions arriving at Earth may come from distant civilizations long extinct, while civilizations still alive are sending signals yet to arrive

But there are potentially habitable planets within 80 light-years of Earth, which is close enough to have received a signal from us, so hope is not completely lost.

HT: IFL Science