In “The Sound of the Drums,” Doctor Who’s nemesis, “The Master,” uses a “paradox machine” to protect the universe from collapsing as the plot line makes a breach of logic. The paradox in question is one that scientists are currently working on: the grandfather paradox.
The paradox, first described by science fiction writer René Barjavel in 1943, goes something like this: What if a man travels back in time and kills his own grandfather before that grandfather ever has children? Then, that grandson wouldn’t exist. And if the grandson was never born, how could he travel through time to kill his grandfather? In conceptual outlines of time-travel, that paradox has been a sticky spot for scientists.
In 2010, physicists at MIT proposed what has been hailed as a solution to the paradox: The principles of quantum teleportation and post-selection, which means that reality can accept only certain results, could limit what a time traveler could or could not do (and that would include killing his ancestors).
