Time travel is not only possible, but it’s been done. Through a phenomena known as ‘time dilation’.
Time dilation is related to Einstein’s theory of relativity. It says that the closer you get to the speed of light, the slower time moves. If you were to leave earth and travel at 99% the speed of light for one year, when you came back to earth, 223 years would have passed. You would have essentially traveled forward in time.
We’ve already done this on a tiny scale. We’ve sent astronauts into space aboard shuttles, and to the moon. These astronauts travel at great velocities for extended periods. Nowhere near the speed of light, but the effect still happens. For every year an astronaut spends aboard the space station (it’s traveling at 17,230 mph or 27,720 km/h), time dilation gives them an extra 10 milliseconds. When they get back to earth, they will be 10ms younger than you.
But what about backwards time travel?
Nothing in Einstein’s theories says it cannot be done, but many scientists balk at the idea because of all the well known paradoxes that it unleashes.
Some scientists, such as the co-founder of String field theory, Michio Kaku, claim those paradoxes don’t necessarily have to happen. There might be a way around them.
He says that quantum mechanics might allow for backwards time travel without paradoxes. The “many-worlds interpretation” of quantum mechanics says that all possible alternative histories and futures are real and exist. It was initially postulated for the quantum world. The world of the sub atomic particles. But if it applies to the world of the small, it must also apply to the world of the large.
But what does this mean for time travel?
It says that when you travel back in time, you are not traveling to your own time line, or dimension. You are traveling to an alternate one. Or rather, creating a new dimension, branching off once you made the decision to go back in time.
You could then go back and kill your grandfather before your father was born, and there would be no paradox because your grandfather still existed and helped to conceive your father in the world or reality you came from. However, there would be no ‘you’ in this new reality, or world. You would have never been born.
It’s certainly mind bending to think about.
Michio Kaku (founder of string field theory) on Time Travel and Parallel Universes: