One generation passeth away, and another generation cometh: but the earth abideth forever.
-- Ecclesiastes
No, not forever. At the outside limit, the earth will probably last another 4 billion to 5 billion years. By that time, scientists predict, the sun will have burned up so much of its own hydrogen fuel that it will expand and incinerate the surrounding planets, including the earth. A nuclear cataclysm, on the other hand, could destroy the earth tomorrow. Somewhere within those extremes lies the life expectancy of this wondrous, swirling globe. How long it endures and the quality of life it can support...