>sky event
the sun's dark companion makes it's once per 26,000y visit to the inner solar system bringing a cloud of gravitationally entrained comets?
4000 yrs of endless winter leading to the next glacial expanse w/ 3 mile thick ice covering CONUS?
a stratospheric thermonuclear detonation producing a EMP destroying the entire electrical grid of north america?
anyone got any moar?