speed of light

noun phrase

: a fundamental physical constant that is the speed at which electromagnetic radiation propagates in a vacuum and that has a value fixed by international convention of 299,792,458 meters per second

—symbol c

Examples of speed of light in a Sentence

Recent Examples on the Web

Photons travel at the speed of light and are less susceptible to interference, and these networks can achieve incredibly fast data transmission with minimal energy loss. —Pramod Kumar, Forbes, 12 Sep. 2024

WIMPs could have masses ranging anywhere from one to 100,000 giga-electron-volts divided by the speed of light squared (GeV/c2), a unit of mass roughly equal to that of a proton. —Saima S. Iqbal, Scientific American, 4 Sep. 2024

These numbers, such as the speed of light or the gravitational constant, define how everything works in our universe. —Quanta Magazine, 4 Sep. 2024

Traveling at the speed of light, the song took almost 14 minutes to reach its destination. —James Factora, Them, 17 July 2024

Word History

First Known Use

1823, in the meaning defined above

Kids Definition

speed of light

: a fundamental physical constant that is the speed at which electromagnetic radiation travels in a vacuum and that has a value of 299,792,458 meters per second