The theory that we would be able to travel through time has intrigued people for an eternity. It seems that the eminent British physicist, Stephen Hawking, decided to conduct an experiment just to show that we are not quite there yet in our ability to travel in this manner.
Several years ago, Hawking decided that he would throw a party and that the only people that were able to go ahead and attend, aside from himself, would be those individuals that could travel through time. In order to show that this is not possible, he only announced the party the day after it happened since the theory was that only people that could travel backwards would then be able to attend.
You must admit that it was a clever idea, but then it is also not that surprising to hear that nobody then turned up therefore proving his theory to be correct.