Why is 299,792,458 m/s the speed of light in a vacuum?

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Discussion Overview

The discussion centers around the question of why the speed of light in a vacuum is defined as 299,792,458 m/s. It explores the implications of this definition, the nature of light's speed, and related philosophical inquiries about measurement and the universe.

Discussion Character

  • Exploratory
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • Some participants note that the speed of light is defined by the length of the path traveled by light in a vacuum during a specific time interval, as per the definition of the meter.
  • One participant raises a philosophical question about the historical and natural reasons behind human units of distance and time, suggesting a deeper inquiry into the nature of measurement.
  • Another participant discusses the significance of the speed of light as a limiting speed for all particles, linking it to the fine structure constant and its mysterious value, which may relate to gravity and spacetime curvature.
  • A participant asserts that the original question has been answered, though this claim does not reflect a consensus among all participants.

Areas of Agreement / Disagreement

Participants express differing views on the implications and interpretations of the speed of light's value, with no clear consensus on the deeper reasons behind its specific speed or the significance of related constants.

Contextual Notes

The discussion includes philosophical considerations and references to definitions that may depend on specific contexts, such as historical contingencies and intrinsic properties of the universe, which remain unresolved.

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Why 299,792,458 m/s?
Why does light travel at the speed that it does?
 
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Because the metre is, by definition, "the length of the path traveled by light in vacuum during a time interval of 1/299 792 458 of a second". See http://www.bipm.org/en/CGPM/db/17/1/.
 
https://www.youtube.com/watch?v=E383eEA54DE
 
From the FAQ section of our relativity forum:

https://www.physicsforums.com/showthread.php?t=511385
 
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It's fun to turn this question around, and say, "Why do humans have these units of distance and time, whose ratio is 1/300,000,000 in natural units?" Which is partly a question about historical contingency, but it's also a question about why human beings have the size and speed that they do.
 
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The speed of light is 1 light*second per second. Its value doesn't tell us much about why it has that particular speed. What is important to know is why light and all electromagnetic radiation and even perhaps gravity waves if they exist have a certain limiting speed beyond which in this universe no particle with or without mass can exceed. The answer lies in the fine structure constant, a dimensionleess quantity equal to about 1/137, which is an intrinsic property of our universe. Its value is a mystery. Hawking hints (I believe) that its value is what it is due to gravity..spacetime curvature in the presence of mass and energy.. which makes our universe what it is, and which therefore makes Gravity..especially at the quantum level...the greatest mystery of all.
 
The OPs question has been answered.
 

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