The speed of light in a vacuum is approximately 299,792 kilometers per second (or about 186,282 miles per second). This value is denoted by the symbol 'c' in physics and is a fundamental constant of nature. It represents not only the speed at which light travels but also sets an upper limit for the speed of information and matter in the universe, as per Einstein's theory of relativity. Light speed is crucial for various scientific calculations and technologies, including satellite communications and GPS systems.