According to our current understanding of physics, based on the theory of relativity, traveling back in time or exceeding the speed of light are not possible. Here's a brief explanation:
Time travel: The theory of relativity, specifically the theory of special relativity, suggests that the flow of time is relative and depends on the relative motion between observers. However, it also establishes that the speed of light is an absolute cosmic speed limit. Time dilation effects occur at high speeds, meaning that time can appear to pass differently for objects moving relative to each other. However, going back in time, commonly referred to as "backward time travel" or "retrocausality," is not supported by the currently accepted scientific theories.
Exceeding the speed of light: According to the theory of special relativity, as an object with mass approaches the speed of light, its energy and momentum increase infinitely, making it impossible to accelerate to or exceed the speed of light. This principle is often referred to as the "cosmic speed limit." The theory of general relativity also indicates that exceeding the speed of light would lead to violations of causality and disrupt the fabric of spacetime.
It's important to note that our understanding of physics is based on empirical observations, experimental evidence, and mathematical models. If new scientific discoveries or theories emerge that challenge the current understanding, our knowledge might be revised. However, there is no scientific consensus or evidence supporting the possibility of backward time travel or exceeding the speed of light.