Well speaking as to the world in its entirety; its crust, mantle, core, etc. then I think it's safe to say the sun will eventually do the job.

Speaking with regard to our world, as in that which concerns all life then my money's on a big rock doing the dirty deed. In the last billion years or so big rocks have had a nasty habit of intefering with evolutionary progress on our planet.


Speaking of which, a big rock is scheduled to miss us come July 3rd. Supposedly it's a about a half mile in diameter and will come almost as close as the Moon's average distance to the Earth. Too close for comfort eh?

http://news.yahoo.com/s/space/200606...pastearthjuly3

Just curious, how many of you would really care about the fate of our planet knowing our species is scheduled to buy the farm?