We're all gonna die! Life on Earth has only 1.75 billion years
left  Scientists have done the math, and according to their
calculations, life on Earth has 1.75 to 3.25 billion years left
to thrive.  And that's if a giant asteroid or a nuclear war
doesn't finish us off first.  Yes, there is a big difference
between 1.75 billion and 3.25 billion years, but predicting the
end of life on our planet it is not an exact science, at least
not yet.  To arrive at that 1.5-billion-year doomsday spread,
graduate student Andrew Rushby of the University of East Anglia
in Britain created two slightly different equations that
estimate the length of time Earth will remain in the "habitable
zone" around the sun.  A planet is considered to be in the
habitable zone when liquid water can exist on its surface.  If
Earth was too close to the sun, high temperatures would cause
our oceans to evaporate; too far away, and we'd be an icy
wasteland.  Earth is firmly in the habitable zone of our sun
right now (obviously - we're all here!)