Its value is 299,792,458 meters per second, or 186,282 miles per second. The speed of light is in reference to how fast light moves from one point to another. This is based on light traveling in a vacuum regardless of the motion of the source. If light is traveling through a medium, then it is slowed, depending on the type of medium. This part of the famous Einstein formula E = mc2, where C stands for light.
