It's a question that has dominated the thoughts of conspiracy theorists and astronomers alike for generations - if there's alien life out there in space, why haven't we heard from it?
Given that Earth has been sending out messages and information for years in case other civilizations come across them, the lack of response has been disappointing for some.
For others, though, it's not surprising at all, but instead plays into their favorite theory about the universe - one that Stephen Hawking apparently believed in when he was alive.
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As explained by a recent TikTok from creator Kalpana Pot (@toknerdytome,) it's called the 'dark forest hypothesis'.
It's all prompted by the huge size of the universe, and the lack of other civilizations talking to us within that expanse.
As Pot puts it: "Take a look at our Milky Way galaxy. Some estimates say it has 400 billion stars and possibly trillions of planets. Even if a tiny fraction of those planets have intelligent life, that's still a big number - small amounts in space terms is still a lot."
So, given that "we've been scanning the skies for signals for over 60 years", she says, how can there be nothing to speak of coming back to us?
Well, this is where the dark forest idea comes in - it's a theory that argues there almost certainly are other civilizations out there which have evolved to the point where they could communicate with us, and that they probably are aware of Earth's existence.
However, for any of a number of reasons, they're choosing not to talk to us. This could be because they've previously been attacked by other civilizations they've discovered, or, more scarily, because they want to keep humanity in the dark in order to maintain a competitive advantage against us.
Worst of all, perhaps there's an even more threatening power out there, one that has frightened others into silence - a lesson that we haven't yet had the chance (or misfortune) to learn.
This is where Stephen Hawking comes in - he's on record as saying in 2010 that alien contact would almost certainly be a bad thing for our species. He said in a documentary for the Discovery Channel: "If aliens visit us, the outcome would be much as when Columbus landed in America, which didn't turn out well for the Native Americans."
That's a pretty sobering thought, especially when it came from someone who had such deep knowledge of astrophysics and astronomy.