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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). [Note 3] According to the special theory of relativity, c is the upper limit for the speed at which ...
Jan 23, 2024 · Learn how the speed of light was first measured, why it is a constant and what it means for relativity. Find out how light slows down in different media and why it is the cosmic speed limit.
May 17, 2023 · The speed of light in a vacuum is 186,282 miles per second (299,792 kilometers per second), and in theory nothing can travel faster than light.
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Learn about the speed of light, the fastest thing in the Universe, and how it compares to other phenomena. Find out if there is anything faster than light, what is the speed of darkness, and what would happen if you traveled faster than light.
Jul 16, 2024 · Learn about the speed of light, a fundamental constant of nature that limits the speed of signals and material particles. Find out its value in a vacuum, its role in relativity, and its relation to Avogadro's number.
- The Editors of Encyclopaedia Britannica
Jul 16, 2020 · But on the other hand, the speed of light can't be anything other than exactly what it is, because if you were to change the speed of light, you would change the fine structure constant. But our ...
May 30, 2023 · So, what is the speed of light? Light moves at an incredible 186,000 miles per second (300,000 kilometers per second), equivalent to almost 700 million mph (more than 1 billion km/h). That's fast ...
