Time travel into the future is theoretically possible and has been observed through phenomena such as approaching the speed of light or being near a massive gravitational well. However, time travel to the past is still a theoretical concept that scientists have tried to understand using Einstein’s field equations.
One possibility is the existence of “closed timelike curves” where spacetime is warped, allowing an object or observer to return to their starting point. Another idea is the creation of a wormhole, which could connect two regions of space and time. However, physicists have yet to observe a stable wormhole that can be traversed.
Another theoretical concept is the Tipler cylinder, also known as a Tipler time machine. This involves creating an incredibly long and dense cylinder that rotates at absurd speeds, potentially allowing travel thousands or billions of years into the past.
According to some mathematical theories, moving around the cylinder in the direction of rotation can shift one’s path back in time, making it possible to travel into the past. However, this concept is still highly speculative and requires significant advances in technology and our understanding of the universe.
Source: https://www.iflscience.com/tipler-cylinders-using-a-gigantic-rotating-tube-to-travel-back-in-time-75310