In June of 2009, Stephen Hawking threw a party. The invitations were sent after the party and not one person knew about it beforehand. The party was for time travelers and was an experiment on the possibility of time travel.
Time travel and its repercussions have long been speculated and showcased in book and film. The possibilities include erasing humanities worst moments, detecting terminal illnesses early, and preventing death.
Fore more information about time travel in pop culture, read Time travel : a history by James Gleick.