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
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With real-time payments, money moves at the speed of light—well, almost. Nick Chandi, Forbes, 16 Oct. 2024 To get all of that working, the scientists needed to invent a device that could accelerate the particles to near the speed of light quickly and over a relatively small distance. Michael Franco, New Atlas, 11 Oct. 2024 The signal crossed the solar system at the speed of light, covering a distance of about 158 million miles in just 14 minutes. Democrat-Gazette Staff From Wire Reports, arkansasonline.com, 22 July 2024 Here’s a fun fact: Electricity—like the photons that comprise quantum technologies—travels at the speed of light or 186,000 miles per second. John Prisco, Forbes, 16 Oct. 2024 See all Example Sentences for speed of light 

Word History

First Known Use

1823, in the meaning defined above

Time Traveler
The first known use of speed of light was in 1823

Dictionary Entries Near speed of light

Cite this Entry

“Speed of light.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/speed%20of%20light. Accessed 21 Nov. 2024.

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

More from Merriam-Webster on speed of light

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