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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
The stray electrons zip around Jupiter near the speed of light and release radio waves.
—Shi En Kim, Smithsonian Magazine, 22 May 2024
Particles from a solar flare can travel at the speed of light and reach Earth in minutes.
—John Tufts, The Courier-Journal, 10 May 2024
As the camera reaches the speed of light, the accretion disc becomes more distorted as space-time warps.
—Eric Lagatta, USA TODAY, 7 May 2024
For instance, the Artificial Intelligence (AI) industry has become mainstream in recent years and is constantly evolving at the speed of light.
—Hilary Tetenabaum, USA TODAY, 5 Apr. 2024
At this time, the cosmos was dominated by radiation—photons and other particles moving close to the speed of light.
—Steve Nadis, WIRED, 25 Feb. 2024
Answers here could be almost unfathomably weird—think parallel dimensions or the ability to travel at a fraction of the speed of light.
—Garrett M. Graff, WIRED, 11 Mar. 2024
The magnetic field surrounding the behemoth black hole at that galaxy's center, known as M87*, is thought to play a key role in its dramatic behavior: The black hole launches a powerful jet of electrons and other subatomic particles into space at nearly the speed of light.
—Denise Chow, NBC News, 27 Mar. 2024
That nearby gas and plasma can also help reveal how feasting black holes create extreme cosmic structures such as relativistic jets — gigantic beams of superheated plasma accelerated to nearly the speed of light.
—Michael Greshko, Quanta Magazine, 12 Feb. 2024
These examples are programmatically compiled from various online sources to illustrate current usage of the word 'speed of light.' Any opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback about these examples.
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 8 Jun. 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
Britannica.com: Encyclopedia article about speed of light
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