Time travel is a mystery to some, but my theories about time travel, makes sence to me, therefore that’s what i will go with until someone comes up with a better one that I can believe. I will try to explain my theory and you have to pay close attention, or you might miss something in the translation. Once you understand this you will also come to the conclusion this is the only way it could happen, and the only sensible way.
A spaceship leaves Earth traveling speeds approaching the speed of light. The travelers travel for 1 year their time, meanwhile back on Earth 100 years or more have passed. Because when traveling great speeds in space the traveler ages slowly and time slows down, and traveling at the speed of light time for the traveler come to a stand still. So after a year in space traveling that fast the traveler would come back to Earth and everyone on Earth would be a lot older or gone, he would be a lot more than 1 year in the future. If they spent more time at or close to the speed of light they could travel thru time eons into the future.
It has been estimated that astronauts who spend considerable amounts of time in space traveling only 25,000 mph. age more slowly than people back on earth. It’s only a few seconds because they are only traveling a small fraction the speed of light. Now multiply that by 26,000 times and the seconds they age even slower and if they were gone for a year it would be many years that passed back on Earth. in other words the traveler comes back in 1 year after traveling in space only to find everyone he knew has died or very old, while he only aged 1 year.
Now the hard part, explaining traveling into the past, it can be done but only for the travelers and only after they reach a speed greater than light speed. But here is the paradox they can only go back in time that they have created and the whole time they are still speeding right along into the future. In other words while they are traveling greater than the speed of light faster and faster into the future but yet going into their past only never being able to get back to where they started also never aging so they could theoretically go forever and maybe even reach the edge of the universe. Or they could come to Earth far into the future, but never in the past.