Z is for Zed. The End. The End of Space and Time.
I have no doubt that if the DeLorean and the TARDIS were to collide in the Time Vortex, the whole fabric of space and time would disintegrate. Or explode, setting everything ablaze. Maybe that's what happens on December 21, 2012? These two time machines hit each other and everything in this quadrant of the whole universe—known and unknown—collapses in on itself and ceases to exist.
Oh, yeah...here's this morning.
And the Cecil B. DeMille close-up.
*License: I took these pictures, or made them.
Word to the Nerd