The speed of light in a vacuum, denoted by the symbol "c," is approximately 299,792,458 meters per second (or about 186,282 miles per second). This value is considered to be a fundamental constant of nature.
According to our current scientific understanding, the speed of light in a vacuum is a universal constant that does not change with distance or time. It is the maximum speed at which information or signals can propagate through space. This constancy of the speed of light is a fundamental postulate of Einstein's theory of special relativity.
In special relativity, it is stated that the speed of light is the same for all observers, regardless of their relative motion. This means that any observer, regardless of their own velocity, will always measure the speed of light to be the same value, c.
The constancy of the speed of light is a crucial concept that has far-reaching implications in physics, including the equivalence of mass and energy (E=mc²) and the time dilation and length contraction effects predicted by special relativity.