I never cease to marvel at the passage of time. It feels like I am located at a point in time, but is time really anything but the collective change of things? It seems to me there is no such thing as time.
I don't know the physics. I know that if I speed up near the speed of light, I slow down in relation to everything else. But this is just a change in the manner of my changing relative everything else. There is no jumping from one time to another because time is not a place. If one could move backward in time, it would mean you changing forward as normal relative to everything else "unchanging" itself. You could only "get to the past" by "passing through" each previous moment of change for everything else.
And if you weren't in the vacuum of space, you would alter the "future" of the rest of the world as your molecules moved through space previously occupied by other molecules. Your moving forward into previously occupied space would displace those molecules, creating an alternative path of change for them going forward. "Time travel" thus, unless it took place in space never occupied, would inevitably change the "future" irreparably. It would alter the path of changing for any molecules into which one came into contact.
I imagine what I just wrote is gross ignorance. I just marvel to think of my former self and to know something about my future self. I will grow old and die--or die early. I see people I knew in a different form decades ago, and now they are different people. I am in this room but soon I will be home. How I got here and how I will get there "in time" I do not know. Each moment, a new me appears and an old me disappears. Where they all come from and where they all go, I do not know.