Total event collapse
A Total Event Collapse was a time explosion, which caused the universe to totally collapse, hence the name "Total Event Collapse." It can be caused by a TARDIS exploding, as shown when The Doctor's TARDIS exploded. The Doctor seemed to have knowledge of them. The only way to stop a total event collapse was to try and reboot the Universe. Some things could survive a total event collapse if they were at the centre of the explosion, before they were also erased from existence, as happened with the Earth. The Doctor yelled, "Total event collapse! Every sun will supernova, at every moment in history! The whole universe will never have existed!", so it seemed the total event collapse caused every star to supernova, at every point in history. The Doctor was able to stop the total event collapse by using the Pandorica, which contained some atoms of the former universe, and flying it straight into the heart of the TARDIS, which reset the universe. It seems that even when a total event collapse has happened, time travel is still possible, but only at the heart of the explosion, on the planet it happened. (DW: The Pandorica Opens/The Big Bang)
