Time travel
It introduces more problems than it solves.
It would violate some very fundamental laws of Physics. To give an example, the second law of thermodynamics. It states that the entropy (number of possible states a given thing can occupy) of an isolated system always increases with time.
It it wasn’t for this law, physical laws would work the same way regardless of the direction of time. In a sense, this law of thermodynamics acts like an arrow of time, for we can say that time has passed when we see entropy increasing.
It is possible to decrease entropy in localised regions, for example, humans are a product of decreased entropy, but the entropy of the whole Universe is always increasing.
What time travel would suggest is that entropy increases over a long period of time, but may not be satisfied in localised periods of time. Instead of entropy decreasing in a particular space at a...