Which theory about the universe keeps you up at night?

What if the entire universe — you, your nan, your disappointing pension — is just a sophisticated computer simulation? Elon Musk believes it. Oxford philosophers argue about it. Sleep tight.

Eventually, billions of years from now, all stars will burn out, all matter will decay, and the universe will reach a state of absolute cold nothingness. There is no escape, no sequel, no reboot.

Quantum mechanics suggests every decision spawns a parallel universe where the other outcome happened. Somewhere out there, a version of you never voted for Brexit — or did, twice, proudly.

Fermi's Paradox asks why we've never found alien life, and the Great Filter theory suggests some catastrophic barrier destroys intelligent species — and we might not have passed it yet.

Statistical physics allows for the random spontaneous assembly of a conscious mind floating in space — your entire existence, memories and all, could be a cosmic fluke that appeared a second ago.