According to our current understanding of physics, it is not possible to go back in time. The concept of time travel to the past, such as going back and changing events, is still purely speculative and not supported by any scientific evidence. While there have been discussions and theories in physics that explore the possibility of time travel, such as wormholes and time dilation, there are significant challenges and paradoxes associated with them.
Regarding the speed of light, as far as our current knowledge goes, it is not possible to exceed the speed of light in a vacuum. In Einstein's theory of relativity, the speed of light is considered an absolute speed limit in the universe. It is denoted by "c" and is approximately 299,792,458 meters per second. As an object with mass approaches the speed of light, its energy increases, and its mass appears to increase as well. The closer an object gets to the speed of light, the more energy would be required to accelerate it further, making it exponentially difficult to reach or surpass the speed of light.
Various experiments and observations have consistently confirmed the constancy of the speed of light, and it plays a fundamental role in our understanding of the laws of physics. However, it's worth noting that the concept of warp drives and other speculative ideas have been explored in science fiction and some theoretical physics frameworks, but their feasibility and compatibility with our current understanding of the universe remain highly uncertain and speculative.