The first big problem is that “time” still remains a big mystery to today’s physicists. Unlike every other process in physics, which theoretically can be reversed, time seems to be stubborn in its directionality or one-way-ness.
The reason for this is spiritual! Time (or succession) is not limited to the physical speed of light.
Time is actually the outcome of God’s creative activity in the universe called “coming into being” or “taking form.” Time proceeds out of the fundamental spiritual fabric of God’s Infinite Love and eternal aim (which is simultaneous). Time is the form that Love dictates. Said another way, Love adapts time (and its forward process) to its own disposition.
Einstein was one of the first modern thinkers to believe that time was a part of the very fabric of physical reality. He was basically correct. But where his theory jumped the tracks is that spacetime was not continuous—like a linear sheet of paper or a membrane. (So wormholes offer no hope of time travel.)
Time is cyclic (periodic) because all process in the universe travels in repeating patterns. Within these patterns are distinct and smaller units of periodic process (like Ezekiel’s vision of wheels within wheels). Therefore, time is layered and operates on different scales. That is why everything in the universe is unified, and has order and orientation.
Because time is the result of God’s influence in the world, all time finds its successive moments leading to some cosmic result—that is, some utility. The universe is nothing but process finding form in uses. Time cannot manifest outside this cosmic law—which promotes interdependence through utility.
To go backwards in time would mean to thwart God’s unifying activity and the directionality of Divine Providence. To move into the future, one would have to jump ahead of God’s creative activity and providence—which means that you would have to know where God is taking the world and be able to do God’s Will all by yourself!
The human mind is, however, designed to jump into different scales of time—even moving outside the realms and boundaries of the physical world. We not only can experience the past through our memory and predict, to a small degree, the future (which meteorologists do), we can also experience the flow of mental and spiritual states, which allow us to experience time differently from our physical bodies.
Deep within the human brain and neuron are structures (substrates) that operate on these different scales. We indeed experience time differently between states of happiness or boredom.
Time travel is not a subject that can be fully grasped from a secular point of view. In fact, if you could jump into the spiritual substrate of your mind, you would experience the passage of time within the narratives of the Lord God’s Holy Word as analogous to the process and directionality of spiritual salvation.