The concept of time travel was touched upon in various earlier works of science fiction, but was really made popular by H. G. Wells' 1895 novel "The Time Machine", which moved the concept of time travel into the public imagination, and it remains a popular subject in science fiction. But it is possible according to physics...
From National Geographic's "Are We Alone?" special magazine:
Well, you're more than welcome to travel into the future. In this universe, you can come up with interesting ways to fast-forward yourself relative to other people. Thanks to the theories of general and special relativity, if you travel close to the speed of light, the passage of time would slow down for you in relation to someone at rest. That would allow you to age less rapidly and effectively shortcut your way to the future. Alternatively, if you somehow put yourself in the middle of a symmetric and strong source of gravity, such as an astronomically massive hollow shell, you would accomplish the same result. And indeed the same would occur if you took a trip around a deep gravitational well, such as a black hole.
But to travel back in time, you would need to get creative in ways the cosmos simply doesn't allow. For instance, if the universe rotated, there would be a path you could travel so that you'd be going backward in time measured against someone else. But to the best of our knowledge, the universe doesn't rotate around any special point. Or, in principle, if you took the right path into a spinning black hole, you might be able to find your way to another space or time, but the mathematics don't seem to line up with our universe.
There are even more mind-bending ways to imagine time travel. Let's say that you and a friend control two ends of a wormhole. You jet off into space at close to the speed of light holding one end of the wormhole and then return. Your companion and her end of the worm-hole will have experienced more time passing than you and your end. Let's say ten years passed for her and three years passed for you. What would happen if you then went through your end? The wormhole connects two places in space and time, so you would exit on your friend's side three years after you started your journey—or seven years in your friend's past. So if wormholes exist, can we start time-traveling? Even if we could get that to work, you could only go as far back as the moment you started traveling in the first place. And even then, it's unclear whether quantum mechanics would allow it. It's possible that a kind of quantum-mechanical "feedback loop" would destroy the wormhole before you or anything else could get through.
In principle, if you took the right path into a spinning black hole, you might be able to find your way to another space or time. gravitational well, such as a black hole.
From National Geographic's "Are We Alone?" special magazine:
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