The **speed of light** in vacuum, commonly denoted $c$, is a universal physical constant that is exactly equal to 299,792,458 metres per second *(approximately 300,000 kilometres per second; 186,000 miles per second; 671 million miles per hour)*. According to the special theory of relativity, $c$ is the upper limit for the speed at which conventional matter or energy *(and thus any signal carrying information)* can travel through space.
spam fails_task lang_mismatch pii not_appropriate hate_speech sexual_content quality toxicity humor helpfulness creativity violence