The conclusion that nothing can travel faster than light is not merely a hypothesis but a fundamental aspect of Einstein's theory of special relativity. According to this theory, the speed of light in a vacuum, denoted as 'c,' is an absolute speed limit in the universe. It is a fundamental constant that remains the same for all observers, regardless of their relative motion.
The theory of special relativity has been extensively tested and confirmed through numerous experiments and observations. One of its key postulates is that the laws of physics are invariant under Lorentz transformations, which means they remain the same for all observers moving at constant velocities relative to one another. From this postulate, it follows that the speed of light is constant in all inertial reference frames.
As an object with mass accelerates towards the speed of light, its energy increases, and its mass appears to increase as well. According to the theory, the energy required to accelerate an object with mass becomes infinite as it approaches the speed of light. This implies that it would take an infinite amount of energy to accelerate an object to, or beyond, the speed of light, making it impossible to achieve.
Therefore, based on our current understanding of physics and the empirical evidence supporting special relativity, the conclusion that nothing can travel faster than light is considered a plausible and well-established aspect of the theory.