The maximum limit on the speed of propagation, often referred to as the "speed limit" of the universe, is determined by the fundamental principles of relativity, specifically the theory of special relativity. According to special relativity, the speed of light in a vacuum, denoted by "c," is the ultimate speed limit of the universe. This means that no information, energy, or physical object can travel faster than the speed of light.
The speed limit arises from the structure of spacetime and the principles of causality. Special relativity shows that space and time are interconnected, forming a four-dimensional fabric called spacetime. The theory also introduces the concept of spacetime intervals, which are invariant and define the separation between events.
When an object or information travels through spacetime, it does so by traversing a path known as the worldline. The length of the worldline, measured in spacetime intervals, represents the proper time experienced by the object or information. Special relativity establishes that the proper time experienced by an object is always greater than or equal to zero.
If an object were to travel faster than the speed of light, its proper time would become imaginary, violating the principles of causality and leading to inconsistencies. It would imply the possibility of effects occurring before their causes, creating paradoxes and undermining the predictability and coherence of the universe.
Electromagnetic waves, including light, are massless particles that travel at the speed of light in a vacuum. They are not subject to the same constraints as massive particles because they have no rest mass. Thus, they naturally propagate at the maximum speed allowed by the universe, which is the speed of light.
It's important to note that there are various experimental observations and theoretical frameworks that support the limitation imposed by the speed of light, and it has been extensively confirmed by experiments in the realm of physics.