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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
Albert Einstein founded his theories of relativity on the notion that nothing can travel faster than the speed of light, however, something that should preclude the instantaneous nature of entanglement.
—Robert Lea, Space.com, 7 Jan. 2025
Solar flares travel at the speed of light, reaching Earth in eight minutes.
—Stephen Ornes, Discover Magazine, 2 Jan. 2025
Fast Performance The speed of light will still be a constraint, but performance and access to data will improve even over the extended distances of space.
—Russ Kennedy, Forbes, 30 Dec. 2024
There is no longer a need to create phrases that are easy to type on a mobile T9 keyboard, instead, Gen Z slang seems to be shaped by meme cycles that evolve at the speed of light and a love of the group chat over online message boards.
—Benedict Cosgrove, Newsweek, 20 Dec. 2024
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Word History
First Known Use
1823, in the meaning defined above
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 Jan. 2025.
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
Britannica.com: Encyclopedia article about speed of light
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