According to our current understanding of physics, the speed of light in a vacuum, denoted by "c," is considered the maximum theoretical speed in the universe. This concept is a fundamental principle in Einstein's theory of relativity, specifically the theory of special relativity.
There are a few key reasons why the speed of light is believed to be the ultimate speed limit:
Consistency of Maxwell's equations: James Clerk Maxwell's equations describe the behavior of electromagnetic waves, including light. These equations suggest that electromagnetic waves propagate at a constant speed, which we call the speed of light. If an object were to exceed this speed, it would violate the fundamental principles of electromagnetism.
Relativity and the constancy of light speed: Albert Einstein's theory of special relativity, developed in 1905, is built upon the notion that the laws of physics are the same in all inertial reference frames. One of the central tenets of special relativity is that the speed of light in a vacuum is constant and the same for all observers, regardless of their relative motion. This constant speed of light forms the basis for many other phenomena in relativity, such as time dilation and length contraction.
Mass and energy increase: As an object accelerates, its mass increases according to the relativistic mass-energy equivalence, expressed by Einstein's famous equation E=mc². As an object with mass approaches the speed of light, its energy and momentum increase dramatically, requiring an infinite amount of energy to reach or surpass the speed of light. This implies that massive objects can never attain or exceed the speed of light.
These reasons collectively indicate that the speed of light is deeply ingrained in the fabric of spacetime and the laws of physics as we understand them. While it is always possible for future scientific discoveries to refine or expand our knowledge, based on our current understanding, the speed of light stands as the maximum theoretical speed in the universe.