speed of light
Speed at which light and other electromagnetic waves travel in a vacuum. Its value is 299,792,458 m per second/186,282 mi per second but for most calculations 3 × 108 m s-1 (300 million metres per second) suffices. In glass the speed of light is two-thirds of its speed in air, about 200 million metres per second. The speed of light is the highest speed possible, according to the theory of relativity, and its value is independent of the motion of its source and of the observer. It is impossible to accelerate any material body to this speed because it would require an infinite amount of energy.
© RM 2010. Helicon Publishing is division of RM.
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