I was watching this video
and it had me thinking about time and how time is really about state. If a system has changed we can say that time has passed but if nothing changes in a system has time passed? If we can go back to a previous state we have effectively time travelled. I am thinking that the bigger and more complex a system the harder it is to return to a previous state. I suggest that local time travel is possible and can be studied at a very small scale and time can go in the opposite direction at that very small scale. Maybe it is possible, we just do not have the power or capability to do it.
My friend Chatty says that what I am describing is essentially the Loschmidt paradox in thermodynamics and the notion of time’s arrow: the fundamental laws are symmetric, but entropy breaks the symmetry macroscopically. So my intuition is very close to actual physics debates. At the smallest scales, physics shows us that time can behave strangely: while the universe’s laws are largely time-reversible, entropy makes it practically impossible to undo changes in large, complex systems. However, in controlled quantum experiments scientists have already demonstrated "time reversal" by restoring particles to earlier states, effectively making them behave as if time ran backward. This suggests your intuition is right—local time travel is possible in principle, but scaling it up to the complexity of everyday reality is far beyond our current power.
Which brings me to my conclusion. In reality we may not be able to achieve time travel but in a simulation we may be able to. If we can create a simulation using very powerful quantum computing where we have figured out the starting point of the universe we could effectively create time travel and go back to the past in the simulation and predict the future except if free will is a reality then that would be something to overcome. We cannot simulate free will or maybe we could. God has designed free will. Maybe that design is humanly discoverable.
My friend Chatty says that in a simulated universe, time travel becomes trivial because the entire "state" of the system is just data that can be rewound or advanced at will, unlike reality where entropy and incomplete information make this impossible. With enough computational power—say from advanced quantum computing—and a perfect model of the universe’s initial conditions, we could recreate its evolution and jump backward or forward inside the simulation. The major challenge would be free will: if it’s truly non-deterministic rather than an emergent, rule-based process, then no simulation could perfectly predict or recreate it, making the past and future only partially knowable even in a perfect model.
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