In the movie "Back to the Future", Marty McFly almost ends up erasing himself from existence after nearly having prevented his parents from falling in love. This idea is often referred to as the "grandfather paradox" - if you traveled back in time and killed your grandfather, then your father or mother would have never been born - a logical impossibility. Of course, the question has been on everybody's mind at least once - is time travel possible?
Pop culture websites and magazines often feature various intriguing, but substanceless, so-called evidence that time travel may be possible. A common mention is a scene from Charlie Chaplin’s film, The Circus. In it, we see a relatively mundane shot from the film’s premiere at Grauman’s Chinese Theatre in 1928. Two individuals walk across the screen behind a zebra. That's a big odd by itself, but far from being the gist. Looking closer, you can see there's a women holding what looks like a cellphone to her ear. While the resolution isn't the best, one can argue that that's a modern hearing aid of some sorts, by the standard of the time. Still, let your imagination roam wild!
Let's not forget about the various celebrities turned time travelers, featured by sites like Buzz Feed.
If genuine time travel were possible, would there be a way to find out? Robert Nemiroff, a professor at Michigan Technological University, recently published a paper in which he presents a possibly viable strategy for spotting time travelers. The whole idea is based on “prescient knowledge" - if you can find information available at present that describes an event from the future, then that information may have been left there by a time traveler, considering there couldn't have been any other way.
With this in mind, Nemiroff searched for a mention of something or someone on the Internet before people should have known about it. He chose two important keywords or phrases Pope Francis and Comet ISON. Apparently, no single record prior to these events becoming public were found. One mention indeed was found about Pope Francis before Jorge Mario Bergoglio was elected head of the Catholic Church on March 16, however the researcher marked the find as an accidental mention more than time travel prescience.
Also, queries themselves, not actual results, were combed through - still, no results were found. That this mean the method is invalid? Not necessarily, maybe Nemiroff didn't use the right keywords. We know that time travel is possible for certain in one direction - the future, thanks to the legacy Einstein left pertaining to relativity. Going back in time, however, is another story.
The study is available in full here.