Time travel is a concept that is still largely theoretical and not fully understood. According to some theories, it involves using the curvature of space-time to create a closed time-like curve, allowing an object to move back in time. However, this concept is still highly debated and has not been proven scientifically.
Cosmic strings are hypothetical one-dimensional objects that are thought to have formed in the early universe. While they have been proposed as a potential way to achieve time travel, there is currently no scientific evidence to support this idea. Additionally, the energy required to create and manipulate cosmic strings would be immense and beyond our current technological capabilities.
Black holes are objects with such strong gravitational pull that not even light can escape from them. Some theories suggest that black holes may act as portals to other points in space and time. However, this is still just a hypothesis and has not been proven.
Many theories of time travel suggest that altering the past is not possible. This is because any changes made would create a paradox, where the past and present would no longer align. Some scientists also argue that the laws of physics would prevent such changes from occurring.
While time travel is currently not possible with our current understanding of physics, it is still a topic of ongoing research and speculation. Some scientists believe that advances in technology and a deeper understanding of the laws of physics may one day make time travel a reality. However, it is important to note that any potential advancements in this area are still purely theoretical at this point.