There are billions of galaxies in the observable universe, each with up to a trillion stars, meaning there are likely trillions and trillions of habitable planets in the cosmos.
But, if such worlds are so abundant, and life on Earth has been able to thrive, then why have we not found any aliens yet?
Known as the Fermi paradox, this is a question that continues to plague scientists - and in a video, experts have tried to tackle what's going on.
But it seems unlikely that we would be the first civilisation to reach this stage, so surely we should have heard from someone by now?
This has led people to suggest that true interstellar travel may be impossible or, more dauntingly, perhaps no civilisation can last long enough to make contact
In a video created by YouTube channel Kurz Gesagt, they take a look at some of the factors that might have prevented us from making contact so far.