Earth is like 'Ground Hogs Day'... the movie. Each day lasts 26,000 years (or maybe its 14,000, or 3,600 years), the civilizations just keep rebuilding/repeating until one of them finally gets it right. They seem to keep blowing themselves (we/us) up so far though... so who knows what will happen this go round.
http://www.youtube.com/watch?v=T_yDWQsrajA
Even tptw keep running in to underground bases built a really long time ago... they just scratch their head and continue to do the same thing again.


I guess that really gives a chilling thought to 'Time' being Toroidal and not linear.