Nuclear war, because we really are that stupid. I'm curious, as to how exactly 'The Earth's centre implodes' will happen? It sounds like some terrible 'evil plan' some James Bond villainesque character would do, and fail at. Or is this actually possible and I've never heard of it before.
I'd say an Asteroid is a potential candidate too, but I'd hope we'd notice an Asteroid big enough to destroy the Earth, with another time to do something about it.
I'd say an Asteroid is a potential candidate too, but I'd hope we'd notice an Asteroid big enough to destroy the Earth, with another time to do something about it.