Superman and the Flash are fictional characters from comic books, and their abilities are often portrayed in a way that defies the known laws of physics. In their respective storylines, both characters possess superhuman speed, but the specifics of their abilities can vary depending on the interpretation.
Superman is typically depicted as having superhuman speed, allowing him to move at incredible velocities. However, the extent of his speed varies across different versions of the character. In most portrayals, Superman's speed is described as being less than the speed of light, although still significantly faster than a normal human.
On the other hand, the Flash, such as the character Barry Allen, is known for his ability to tap into the "Speed Force" in the DC Comics universe. The Speed Force is a fictional concept that grants the Flash and other speedsters in the DC universe extraordinary speed. The Flash is often depicted as being able to reach or even exceed the speed of light, enabling him to perform feats like time travel and dimension hopping.
In the realm of physics, our current understanding based on Einstein's theory of relativity suggests that objects with mass cannot reach or exceed the speed of light in a vacuum. According to this theory, as an object with mass approaches the speed of light, its relativistic mass increases, and it would require an infinite amount of energy to reach or surpass the speed of light.
Therefore, based on our understanding of physics, it is not possible for any object, including Superman or the Flash, to move faster than light. However, it's important to remember that these characters exist in fictional universes where different rules can apply, allowing them to possess superhuman abilities beyond what is currently possible according to our scientific knowledge.