The speed of light in a vacuum, denoted by the symbol "c," is a fundamental constant of nature and is approximately 299,792,458 meters per second. Electromagnetic radiation, including visible light and other forms of electromagnetic waves, travels at this speed due to the underlying properties of electromagnetic fields and the structure of spacetime.
The speed of light is determined by the interaction between electric and magnetic fields, as described by Maxwell's equations in classical electrodynamics. These equations mathematically link the electric and magnetic fields, forming electromagnetic waves that propagate through space. The speed at which these waves propagate is dictated by the fundamental properties of electric and magnetic fields.
The speed of light is also linked to the permeability and permittivity of free space, which are intrinsic properties of the vacuum. These properties determine how electric and magnetic fields interact and propagate through space. The interplay between electric and magnetic fields, as well as the properties of the vacuum, sets the speed at which electromagnetic waves, including light, travel.
As for why electromagnetic radiation doesn't go faster or slower than the speed of light, it is ultimately a consequence of the nature of spacetime and the fundamental laws of physics. In the theory of special relativity, proposed by Albert Einstein, the speed of light in a vacuum is considered an upper limit for the velocity of any physical object or information. According to this theory, as an object with mass approaches the speed of light, its energy requirements to accelerate further become infinite. This concept is known as "mass-energy equivalence" or "relativistic mass."
Additionally, the speed of light is tied to the geometry of spacetime itself. The theory of general relativity, also developed by Einstein, describes gravity as the curvature of spacetime caused by massive objects. The speed of light plays a crucial role in general relativity, and any deviation from its constant value would have significant implications for the behavior of gravity and the structure of the universe.
In summary, the speed of light is a fundamental limit imposed by the properties of electromagnetic fields and the nature of spacetime. It cannot go faster or slower due to the underlying principles of electromagnetism and the laws of physics.