Special relativity provides a theoretical basis for time travel. If you keep moving faster than the speed of light, your time will be slower than that of an object that does not move faster than the speed of light. To exaggerate, it can be understood that when you have been moving at a speed faster than the speed of light 1 year, and our time may have passed three years, then you stop at this time, and you think that it has only passed one year, but in fact it has passed three years. So you can go to the future.
However, if we want to go back to the past, we must look for theoretical basis from general relativity, which suggests that it is possible to go back to the past. For example, if we draw two points on a piece of paper, then we can think about it in different ways. The shortest distance between them is not a straight line. We can fold the paper so that two points overlap, which is the shortest distance between them! We regard paper as space, two points as past and present, and time as that straight line. That line can only go in one direction. We can't go back. But if we distort or even fold the space, then the past and the present will approach or even overlap, and there will be a wormhole between these two points (that is, what we say is just visiting), through which we can go back to the past. But this is just a theory. Science has proved that once human beings are sucked into wormholes, it is impossible to cross them. And going back to the past also involves the problem of "grandmother paradox"!
What is it? In other words, if I go back in time and kill my grandmother before my mother was born, there will be no mother, no mother and no me. This is the famous grandmother paradox! This seems to show that going back to the past is not feasible. But scientists put forward the view of "historical equality" (that is, "parallel universes"), that is to say, there is not only one world, but many parallel worlds exist. A person can go back to the past and kill his grandmother, but this will lead the world into two different tracks, one with that person (the original track) and the other without that person. This is more popular.
All the above assumptions are based on relativity. In reality, at least for now, humans can't travel through time and space. If they want to go to the future, they can't go beyond the speed of light now. It is even more impossible to go back to the past, and whether they can cross the wormhole or not, they can't create enough power to distort the present space!