According to particle physicist Brian Cox time travel is possible, but only to the future.
“Can you build a time machine?” said Professor Cox. “The answer is yes.”
There’s just one, tiny problem, Professor Cox says – if you can build a machine capable of time-travel, you can only travel into the future. You can’t come back.
Professor Cox explains how building a time machine to travel to the future is possible
here and here.
Thanks to Brian Michael Bendis for the original link.