Time Travel: We Can Travel to the Future. The Past May Be Off the Table.

Is time travel possible? The answer depends on which direction you mean. What we can say with confidence is that travelling into the future is achievable. Travelling into the past is either wildly difficult or flatly impossible. The question isn’t one idea but two, and they don’t get the same answer. To see why, we start where the physics starts: Albert Einstein’s theories of relativity. They describe how space, time, mass and gravity relate to one another. Seen that way, time stops being a fixed backdrop and becomes something that can behave differently from what everyday intuition suggests. This is for anyone who has taken “time travel” to mean one thing, or has assumed the answer is a simple yes or no. It lays out what relativity allows and what it doesn’t, so you can judge for yourself where the real line sits between the achievable and the doubtful.