Time travel to the past is theoretically possible in certain general relativity spacetime geometries that permit traveling faster than the speed of light, such as cosmic strings, traversable wormholes, and Alcubierre drives.
The fact that the universe is still around is ample evidence that time travel to the past is impossible.
The idea is that backwards time travel is impossible because if it occurred, time travellers would attempt to do things such as kill their younger selves (or their grandfathers etc.). We know that doing these things—indeed, changing the past in any way—is impossible.
In the Back to the Future franchise, the DeLorean time machine is a time travel device made by retrofitting a DMC DeLorean vehicle with a flux capacitor, which allows for time travel when it hits 88 miles per hour.
While it's not possible (yet) to travel to the future fast than the rate at which we're doing it now, it is possible to speed up the passage of time. But, it only happens in small increments of time. And, it has only happened (so far) to very few people who have traveled off Earth's surface.
And, as physicist Stephen Hawking pointed out in his book "Black Holes and Baby Universes" (Bantam, 1994), "The best evidence we have that time travel is not possible, and never will be, is that we have not been invaded by hordes of tourists from the future." Science does support some amount of time-bending, though.
The simplest answer is that time travel cannot be possible because if it was, we would already be doing it. One can argue that it is forbidden by the laws of physics, like the second law of thermodynamics or relativity. There are also technical challenges: it might be possible but would involve vast amounts of energy.
Most physicists agree that you cannot change the present by going back to the past. The Novikov self-consistency principle is a formal statement of this assertion. If we are able to go back to the past, and make changes, the universe will simply rearrange events so that the present stays the same.
In fact, according to Albert Einstein's famous equation, E = mc² , time travel is possible, at least in one direction.
People go through a series of difficult experiences in life that might force them to contemplate their past. During these periods of reflection or regret, they'll sometimes wish they could turn back time, either to return to “the good old days” or to undo the mistakes they've made.
People in the past used to travel in search of livelihood, to escape from natural disasters, or to conquer other land of others.
One idea from the 'multiverse' hypothosis is that if you did go back in time & met yourself, time (& hence reality) would 'branch off' and develop in a way that is different from the way it developed in your memories.
In special relativity, the speed of light is the ultimate speed limit to the universe. Nothing can travel faster than it.
It may not always be possible to forget unwanted memories, but people can use strategies to help them cope with traumatic events. This can include memory suppression techniques, identifying triggers, and contacting a mental health specialist.
Over the years, you develop, change, grow, and learn so many new things. Your interests change, as do your hobbies, relationships, and experiences. If you stay stuck in the past, you will never truly be able to embrace who you are in the present day, and you will never be able to grow to your fullest potential.
While researchers have never found a wormhole in our universe, scientists often see wormholes described in the solutions to important physics equations. Most prominently, the solutions to the equations behind Einstein's theory of space-time and general relativity include wormholes.
Because space isn't curved they will never meet or drift away from each other. A flat universe could be infinite: imagine a 2D piece of paper that stretches out forever. But it could also be finite: imagine taking a piece of paper, making a cylinder and joining the ends to make a torus (doughnut) shape.
Time travel is still impossible because all these theories can't be tested practically. Scientists are trying to make a time machine, but it all seems possible in science-fictional movies. You will find several people claiming to time travel, like Alexander Smith. But no one has concrete proof to support their claim.
In short, space-time would contain the entire history of reality, with each past, present or future event occupying a clearly determined place in it, from the very beginning and for ever. The past would therefore still exist, just as the future already exists, but somewhere other than where we are now present.