The speed of light in a vacuum is measured at 186,282 miles per second, which is 670,616,629 miles per hour. The speed of light is denoted mathematically by the symbol "c."
Although early scientists thought that light traveled at an instantaneous speed, later experimentation concluded that there was a finite speed. Two French physicists in the mid-1800s, working simultaneously on different experiments, arrived independently at results that were within 1,000 miles per second of an accurate answer. It wasn't until 1879 when Prussian-born Albert Michelson, working in the United States, used a high-quality system of light beams, lenses and mirrors to arrive at the result of 186,355 miles per second, the most accurate measurement for the next 40 years.