The reason why the speed of light is considered an absolute speed limit in our universe is deeply rooted in the principles of special relativity, a fundamental theory developed by Albert Einstein.
According to special relativity, the speed of light in a vacuum, denoted by the symbol 'c,' is the same for all observers, regardless of their relative motion. This means that no matter how fast an observer or object is moving, it cannot surpass or reach the speed of light.
There are several interrelated reasons why this speed limit is fundamental:
Constancy of the Speed of Light: In Einstein's theory, the laws of physics, including the propagation of light, are described by a set of equations that are consistent in all inertial reference frames. These equations predict that the speed of light remains the same regardless of the relative motion between the source of light and the observer. Numerous experimental observations have confirmed this constancy of the speed of light.
Time Dilation: As an object approaches the speed of light, according to special relativity, time dilation occurs. This means that from the perspective of an observer in relative motion, time appears to slow down for the moving object. As the object's speed approaches the speed of light, time dilation becomes increasingly significant. This effect is a consequence of the relativistic relationship between time, space, and velocity and is a way the universe preserves the speed limit.
Mass-Energy Equivalence: Special relativity also introduces the famous equation E = mc^2, which states that energy (E) and mass (m) are interchangeable and directly related. As an object with mass accelerates, its energy increases. As it approaches the speed of light, the energy required to accelerate it further becomes infinite. This energy requirement makes it impossible for an object with mass to reach or exceed the speed of light.
Causality and Paradoxes: Allowing objects to travel faster than light would lead to violations of causality, which is the principle that cause and effect must follow a consistent order in time. If information or signals were to travel faster than light, it would result in paradoxes and contradictions, such as being able to send messages back in time.
The universe, as far as we understand it, follows these fundamental principles and properties. The speed of light acts as a fundamental speed limit, preserving causality, ensuring consistency of physical laws, and maintaining the structure of spacetime. The preservation of this upper barrier on the speed of light is a fundamental aspect of our universe's behavior, as revealed by our current understanding of physics.