there is no scientific evidence or established theory that suggests time travel to the past is possible. The concept of traveling back in time remains purely speculative and largely confined to the realm of science fiction.
In terms of theoretical possibilities, some physicists have explored the idea of time travel using concepts from general relativity, such as wormholes or space-time loops. These ideas involve the bending of space and time to create a path that connects different points in time or allows for closed timelike curves. However, these theories involve exotic matter with negative energy densities or the need for stable, traversable wormholes, both of which are purely hypothetical and not yet supported by experimental evidence.
Regarding the energy requirements for time travel, it is difficult to quantify since we do not have a well-established theory of time travel. Speculative methods such as creating and manipulating wormholes or using cosmic strings would likely require enormous amounts of energy, potentially on the scale of the entire energy output of a star or even more. However, this is purely conjectural, and the actual energy requirements, if time travel were possible, remain unknown.
It's important to note that the laws of physics, as we understand them today, do not provide a clear path for backward time travel. Our current understanding suggests that time travel to the past is highly unlikely, if not impossible.