Stephen Hawking: Time Travel Possible, But Only Forward

May 7, 2010 Updated: May 7, 2010

In Stephen Hawking’s universe, even spaceships can slow down time with high speed. By surpassing time, humans would find themselves able to travel into the distant future.

Hawking said that it would take 86 years for such a spaceship to reach the edge of the galaxy, in which six of the years would be spent on accelerating the ship to 98 percent of the speed of light, according to the Daily Mail.

Time travel through the fourth dimension is realistic, said Hawking, such as finding a tiny wormhole and enlarging it wide enough for a space ship to fit in.

Nevertheless, only time travel forwards is possible. Otherwise it would violate the universe’s fundamental law—the cause before effect.

“Any kind of time travel to the past through wormholes or any other method is probably impossible, otherwise paradoxes would occur,” Hawking wrote. “So sadly, it looks like time travel to the past is never going to happen. A disappointment for dinosaur hunters and a relief for historians.”

For a Star Wars fan, this scenario comes at no surprise. Yet Hawking said that he is afraid of talking about time travel since back in the day it seemed too farfetched.

“I used to avoid talking about it for fear of being labeled a crank. But these days I'm not so cautious,” Hawking wrote.