For most of us, the idea of time travel is one confined solely to science fiction programmes and novels. For many physicists, however, time travel is a very real idea built into the fabric of the universe we live in.In fact, many of today’s most prominent scientists believe that one day, humanity will be able to travel forward in time as easily as stepping on an airplane. Even Stephen Hawking believe it. Seems like time’s not quite as solid as your wristwatch would have you believe. As Doctor Who will tell you, time is “more like a big ball of wibbly wobbly, timey wimey… stuff.”Why? Well, to explain that, we’ll have to start with everyone’s favourite genius: Albert Einstein. At the start of the 20th century, Einstein blew everyone’s minds with his ideas about how we should think about time and space.Einstein suggested that we shouldn’t think of the two as two separate elements, but as one: spacetime. And if we can travel through space, then we should theoretically be able to travel through time. Time becomes an extra fourth dimension, one which anyone should be able to move through.According to Einstein’s theories, if we could travel faster than the speed of light, then we would be able to travel forward in time. The problem with that, however, is that no one can figure out how to make a human go faster than the speed of light. That’s 186,282 miles per second, just in case you were wondering.Okay, so putting the mechanics aside for one minute… if we could travel faster than the speed of light, what would happen? Well, if we somehow managed to build spaceships that can fly faster than the speed of light, a day onboard would be equivalent to a year on Earth.
As Professor Stephen Hawking recently explained: “It would take six years at full power just to reach these speeds. After the first two years, it would reach half light speed and be far outside the solar system. After another two years, it would be traveling at 90 per cent of the speed of light.“After another two years of full thrust, the ship would reach full speed, 98 per cent of the speed of light, and each day on the ship would be a year on Earth. At such speeds, a trip to the edge of the galaxy would take just 80 years for those on board.”Sounds pretty nifty, huh? If we could travel forwards in time, we’d be able to reach incredible distances in a relatively short amount of time. The potentially habitable planet Proxima Centauri b you’ve been hearing so much about? We’d be able to reach it in just 4.22 years. Unfortunately, though, by the time you returned back to Earth, your entire family would probably be dead.Theoretical physicist and string theorist Brian Greene, of Columbia University explained: “When you step out of your ship, you’re one year older but Earth has gone through many, many years. It can have gone through 10,000, 100,000 or a million years depending on how close to the speed of light you traveled.”Another idea for travelling in time involves travelling through wormholes connected to another areas of spacetime. Michio Kaku, physicist at the City University of New York said: “Wormholes are the future, wormholes are the past. But we have to be very careful. The gasoline necessary to energize a time machine is far beyond anything that we can assemble with today’s technology.”Not only is travelling forward in time possible, in fact, it’s already happened. Russian Cosmonaut Sergei Krikalev not only holds the record for the longest time spent in space, at 803 days, nine hours, and 39 minutes; but he also holds the record for the human who’s traveled the furthest in time. Why? Well, thanks to the effects of time dilation, Krikalev has actually lived for 0.02 seconds less than everyone else on Earth. This mean’s he’s effectively travelled 0.02 seconds into his own future. Freaky, right?Now, I know what you’re thinking: what about travelling backwards in time? Well, I think it’s safe to say that one’s a little more tricky. In order to create the series loops and wormholes required to go backwards in time, we’d need half of all the matter and energy in the universe. Probably best to leave your dream of going back in time and killing Hitler on the shelf for now, then.