The use of "c" as the symbol for the speed of light can be traced back to the pioneering work of the French physicist Augustin-Jean Fresnel in the early 19th ce

The use of "c" as the symbol for the speed of light can be traced back to the pioneering work of the French physicist Augustin-Jean Fresnel in the early 19th century. In his research on light and optics, Fresnel used the letter "c" to represent the speed of light in his equations and formulas. The choice of "c" was likely influenced by the Latin word "celeritas" and its association with speed.