This is an issue that the character Ye Wenjie wrestles with in the first episode of Netflix’s 3 Body Problem. Working at a radio observatory, she does finally receive a message from a member of an alien civilization—telling her they are a pacifist and urging her not to respond to the message or Earth will be attacked.

The series will ultimately offer a detailed, elegant solution to the Fermi Paradox, but we will have to wait until the second season.

Or you can read the second book in Cixin Liu’s series, The Dark Forest. Without spoilers, the explanation set out in the books runs as follows: “The universe is a dark forest. Every civilization is an armed hunter stalking through the trees like a ghost, gently pushing aside branches that block the path and trying to tread without sound.”

As we go on with our everyday lives, it’s very easy to forget about the sheer size of the universe.

The Earth may seem like a mighty place, but it’s practically a grain within a grain of sand in a universe that is estimated to contain over 200 billion galaxies. That’s something to think about the next time you take life too seriously.

So when we gaze up into the starry night sky, we have every reason to be awestruck—and overwhelmed with curiosity. With the sheer size of the universe and the number of galaxies, stars, and planets in it, surely there are other sentient beings out there. But how come we haven’t heard from them?