Is time travel possible? Yes, we actually do it all the time. Every passing minute is a moment we travel into the future, at a rate of one minute per minute. From 12:00 to 12:05, we travel five minutes into the future. That sort of time travel is not very sexy. It’s not the type of story science fiction loves, where characters go on voyages in time, hundreds of years into the future or into the past. But here's the good news: that’s possible as well. At least we’re sure we can time travel years, even millennia, into the future, and we’ve known how to do it for decades now, all thanks to the work of Albert Einstein.
In his theory of Relativity, the famed scientist explained that gravity and speed affect time flow. What does this mean? That the faster you move, the slower time passes for you. For example: if you get into a spaceship and travel at a speed close to the speed of light, when you get off the spaceship back on Earth, you’d do it thousands of years after your departure. The same happens with gravity. The stronger the gravitational pull you experience, the slower time passes for you, relative to everyone else. It’s what happens in films like Interstellar: the characters approach a black hole (its gravitational pull is huge, given its massive density) and when a few minutes latter they return to their spaceship, far from the black hole’s gravitational pull, 17 years have passed. So traveling to the future? You just need a very fast spaceship or a very strong gravitational field.
But what about traveling to the past? Well, here's where it gets tricky. Most scientist say it’s impossible, since the universe is governed by laws of causality, cause and effect. For a process to occur (effect), there needs to be another process before it (cause). Time traveling into the past breaks these rules, for it generates time paradoxes: events without apparent causality. This sounds complicated, but just think about it in movie terms. In Back to the Future Marty travels to the past and his mother falls in love with him, which stops her from marrying his father, therefore preventing Marty’s birth. But if Marty was never born, then he wouldn’t travel to the past and his parents would fall in love, and he would be born after all. And this loop goes on and on and on to infinity. Which one happened first? Which event was the cause and which one the effect? It’s like the chicken or egg dilema.
The laws of physics make traveling to the past an impossibility, so that’s that. Or is it? Some, like Ron Mallett, are not so sure. This theoretical physicist has dedicated his entire career to finding ways to build a time machine that might allow a person to travel back in time, and if he succeeds, his life story will definitely be adapted into an tear-jerking Academy Award winning biopic. You see, Ron’s motivation to do this is to stop his father from dying from a heart attack when he was 10 years old. The event was and still is so traumatizing to him, that he decided to pursue a career as a scientist to stop it from taking place, so he joined the army and fought in the Vietnam War in order to secure a scholarship to Penn State University.
During his remarkable career as a professor and researcher, Ron came up with what some consider our best shot at traveling into the past, as the rest of the accepted theories require technological advances we won’t see for hundreds of years, if ever at all. His proposal involves light. You see —as he explained last year in an interview with the Telegraph—, Einstein’s theory states that light can generate gravity, just like matter, and we’ve already established that gravity affects time, so Ron thinks that if you can use light to generate enough gravity and then make it spin, it could bend space and time, and therefore allow us to travel to the past through a wormhole (a disturbance that connects two points in spacetime). This would be accomplished through a device called a "ring laser", that make lasers go around in loops.
If he succeeds in creating his time machine, Ron wouldn’t be out of the woods just yet, since the laws of physics wouldn’t allow him to travel to any point before the time machine came into existence, when it generated the wormhole in the first place. But he’s started using quantum mechanics to generate new models (that go around the laws of causality) that might allow him to travel to any point in history, including somewhere before his father’s death in 1955. It seems insane to imagine a world where time travel could be a reality, and even more in the terms Ron Mallett proposes, but who knows? This scientist seems convinced it’s something we could accomplish someday, and he’s got 60 years of experience to back his claims.
If you enjoyed this, try out this article on the Philadelphia project and the "scientific" reason why there are few women in science.