How Will the World End?

Historians have long studied how civilizations rise and fall. But today it isn't just social collapse that makes thoughtful people fret but a potential end to everything. From nuclear war to ecological disaster to rocks from the sky all the way to luring unfriendly interest from "others" out there, science has shed light on myriad ways to fail. To tumble back down into entropy. So, want to have some fun listing and weighing all the ways (that we know) the universe could have it in for us? Partly in order to seek ways through the minefield, of course. But also because, well, who doesn't like a scary campfire story about apocalypse now and then?