The concept of time travel is a fascinating topic, often explored in science fiction, but as of our current understanding of physics, there are several limitations and challenges associated with time travel. These limitations include:
Causality and paradoxes: Time travel raises the issue of causality paradoxes, such as the famous "grandfather paradox." If you were to travel back in time and prevent your grandparents from meeting, it would create a paradoxical situation where you would never be born, which raises logical contradictions. Resolving such paradoxes is a significant challenge.
Consistency with physical laws: Time travel would need to be consistent with the known laws of physics, such as general relativity and quantum mechanics. Currently, there is no conclusive scientific evidence or theory that supports the feasibility of time travel.
Energy requirements: The energy requirements for manipulating time on a macroscopic scale are currently beyond our technological capabilities. The energy densities and exotic matter that might be needed to bend or warp spacetime significantly are still hypothetical or only exist in extreme astrophysical conditions.
Technological limitations: Even if we were to imagine that time travel were possible, developing the technology to achieve it would require advances far beyond our current capabilities. It would involve immense engineering challenges and a deep understanding of fundamental physics.
Regarding the idea of humans visiting their ancestors, if time travel were to become a reality, it might allow individuals to travel to different points in the past. However, the exact mechanics and possibilities would depend on the nature of time travel itself, which is still purely speculative.
It's important to note that while time travel remains a captivating concept in fiction, scientists and researchers are primarily focused on understanding the nature of time itself and advancing our knowledge within the framework of current scientific theories. At present, time travel is not considered a viable or confirmed possibility according to our current understanding of the laws of physics.