The universe is trying to kill us. In Death From the Skies! by our own Bad Astronomer, Phil Plait, counts the ways the world will end. Start worrying in a few million years about a cosmic dust collision, when the sun hits the closest spiral arm of our galaxy. Take your chances with an exploding star. Or manage to escape these threats, and you just get an extra 1035 years before all matter decays anyway.
||Odds of fatality per lifetime
||Local for a small rock, global for a big one
||1 in 700,000
||Almost 100% preventable. Identify potential impactors, then blow them up or push them out of the way
||Collapse of power grid, potential ozone depletion
||Non-preventable, but mitigatable
Build robust power grids
||Ozone depletion, radiation
||1 in 10,000,000
||Ozone depletion, radiation, setting planet on fire
||1 in 14,000,000
||Destruction of Earth
||1 in 1,000,000,000,000
||Humanity wiped out by aliens, space bugs give us runny noses
||Preventable, assuming we colonize the galaxy first.
Otherwise, forget it.
|death of the sun
||Earth cooked to a crisp
||Not preventable, but we have a long time to go yet
||Ice ages, radiation, eaten by supermassive black hole
||Not preventable, but again, none of these will happen on a human timescale
|death of the universe
||Decay of all matter, collapse of false vacuum
||Not preventable, but dwarfs any timescale we can imagine
* Fatalities are very unlikely from a solar event, but they can still cause extensive damage.
† These events all take billions of years (at least!) to unfold, so the chances of them happening during your lifetime are zero, but are inevitable over longer times.
Table reprinted by arrangement with Viking, a member of Penguin Group (USA) Inc., from DEATH FROM THE SKIES! © Philip Plait, Ph.D., 2008