Lightspeed
Symbol: c
Lightspeed characterizes the speed of electromagnetic radiation in vacuum. According to the theory of special relativity it is a physical constant and the highest speed, energy or matter can travel.
In 1983 the meter was defined as the distance light is travelling in vacuum in 1/299,792,458 of a second. As a result, lightspeed is exactly 299,792,458m/s.
1m/s = 0.000000003335641c