Forget nuclear war, climate change and fiery out-of-control space stations - it's an expanding bubble that will kill us all, scientists say.
The universe will probably end when a subatomic particle called an instanton begins expanding at the speed of light, devouring everything in its path, according to a new paper published in journal Physical Review D.
"It will be very unpleasant," lead author Anders Andreassen of Harvard University told Live Science, perhaps understating the gravity of his claim.
And it may already have begun. Because the bubble would be expanding at the speed of light, it would get here in advance of any other signs of its existence.
The study text is full of phrases like "exact closed-form solutions for the functional determinants over scalars" and "demonstrating manifest gauge invariance in the vector case", but essentially it boils down to this: the amount of energy in the Higgs boson changes for some reason, forming a bubble which expands at the speed of light, destroying everything it touches.
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The Higgs boson was theorised decades ago, but not proved beyond doubt until 2012 thanks to the Large Hadron Collider. There were fears at the time turning the supercollider on would create a black hole that would destroy Earth, which were unfounded - thankfully or sadly, depending on your point of view.
The idea of an existence-ending bubble of carnage has been bandied about before, notably by Stephen Hawking, but the new research has also put a likely date on the universe's expiry: somewhere between 10 octodecillion years (one with 58 zeros after it) and 10 quinquadragintillion years (139 zeros).
"That is a very, very, very, very, very, very, very, very, very, very long time," said Prof Andreassen. "Our sun will burn up and many things will happen in our solar system before this is very likely to happen."
There are only about 5 billion years (nine zeroes) until the sun dies.
The reason the number is so big is that the universe may be infinitely huge - we just don't know.
While the bubble will kill us and everything we know, Prof Andreassen says the universe might rise again.
"I wouldn't put my money on this being the end of the story. I would expect dark matter to come kick in and change the story."