Speed of light

1676 Speed of light

The book of science

Tom Sharp

Ole Rømer electromagnetism

Speed of light

Historical speeds

In a vacuum

The speed of light, c, is exactly 299,792,458 meters per second, about 186,282 miles per second. Only luxons—photons, gluons, and, theoretically, gravitons—can travel at this speed. Anything with “rest mass,” according to the special theory of relativity, gains “relativistic mass” as its speed approaches the speed of light, which it can not reach.

The numeric value of c in meters per second is fixed by the definitions of meter and second.

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