re: Incidentally...
By extreme, I'm only thinking along these terms for now:
Extreme: 1) Asteroidal or cometary impact.
2) Our sun shedding it's outer shell, in about 4 billions years from now. Before then, we WILL feel it's heat. Someone I admired here said that it would be in the thousands of years (hopefully, hundreds) as our sun's outer shell starts to 'grow'.
