Temporal collision

A temporal collision occurred when the Tenth Doctor inadvertently caused his TARDIS, which he had neglected to shield, into that of his fifth incarnation's, which put the universe in danger of being sucked into a Belgium-sized black hole. However, the Doctor used his memory of the event from his fifth incarnation's viewpoint to create a supernova at exactly the same moment the black hole appeared. As a result, the Doctors' TARDISes separated and the two parted ways. (TV: Time Crash)