No, special relativity does not only apply to light. Special relativity is a theory developed by Albert Einstein that deals with the behavior of objects and observers in the absence of gravitational forces. It encompasses a broader range of phenomena beyond just the behavior of light.
Special relativity introduces two fundamental principles: the principle of relativity and the constancy of the speed of light. The principle of relativity states that the laws of physics are the same for all observers in uniform motion relative to each other. This means that the laws of physics should be consistent regardless of the observer's velocity.
The constancy of the speed of light in a vacuum is another key concept in special relativity. According to this principle, the speed of light in a vacuum is always the same for all observers, regardless of their relative motion. This means that the speed of light is a universal constant.
Special relativity provides a framework for understanding how space and time are interwoven and how they are perceived differently by observers moving at different velocities. It introduces concepts like time dilation, length contraction, and the relativity of simultaneity. These concepts apply to all objects and observers, not just light.
While special relativity does have profound implications for the behavior of light, such as the fact that nothing can travel faster than the speed of light, it applies to all types of objects and phenomena in the universe. However, its effects become more pronounced at very high speeds, close to the speed of light.