The common unit of measure for the speed of light is the meter per second (m/s). In a vacuum, the speed of light is constant at approximately 299,792,458 m/s, which is fundamental to various physical theories, including relativity. Understanding the speed of light is essential in fields such as astronomy, physics, and telecommunications, as it influences concepts like time dilation and the observable universe's structure. It serves as a critical standard in both theoretical and experimental contexts in science.