What is the speed of light in a vacuum?

The speed of light in a vacuum is approximately 299,792,458 meters per second, often rounded to 3.0 × 10⁸ m/s. This universal constant, symbolized as c, is fundamental to physics, especially in Einstein’s theory of relativity, where it represents the maximum speed at which information or matter can travel. Light’s constancy across all reference frames forms the basis for modern physics. The value also serves as a cornerstone for measuring astronomical distances, such as light-years, and defining the meter in the International System of Units. Understanding light’s speed helps scientists study time, space, and energy across the universe.