Quantum mechanics is weird. One of the attempts at explaining how come it is so weird is the Many Worlds Interpretation, which states that every possible way history could have turned out, actually has in seperate parallel universes.
The problem between all the interpretations of quantum mechanics is that no one has been able to determine which one reflects what actually happens.
Now Frank Tipler, a physicist at Tulane University in New Orleans says he has hit upon a way in which these interpretations must produce different experimental results.