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

In summary, the speed of light is 299,792,458 m/s because it is defined as the distance traveled by light in vacuum in 1/299 792 458 of a second. This ratio is also related to the fine structure constant and the intrinsic properties of our universe. The question of why humans have chosen these units of distance and time is partially due to historical contingency, but also relates to the mysteries of gravity and spacetime curvature.
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Why 299,792,458 m/s?
Why does light travel at the speed that it does?
 
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  • #2
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/.
 
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https://www.youtube.com/watch?v=E383eEA54DE
 
  • #5
From the FAQ section of our relativity forum:

https://www.physicsforums.com/showthread.php?t=511385
 
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  • #6
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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  • #7
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.
 
  • #8
The OPs question has been answered.
 

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

What is the significance of 299,792,458 m/s in relation to the speed of light in a vacuum?

The number 299,792,458 m/s is the exact numerical value of the speed of light in a vacuum, which is considered to be a fundamental constant in the field of physics. It is denoted by the symbol 'c' and has a value of approximately 3.00 x 10^8 meters per second.

How was the speed of light in a vacuum determined to be 299,792,458 m/s?

The speed of light in a vacuum was first measured by Danish astronomer Ole Rømer in the 17th century using observations of the moons of Jupiter. However, it was not until the 19th century that it was accurately measured by scientists using a variety of experimental techniques, such as the Fizeau-Foucault apparatus and the Michelson-Morley experiment.

Why is the speed of light in a vacuum considered to be a constant?

The speed of light in a vacuum is considered to be a constant because it is the same for all observers, regardless of their relative motion or inertial frame of reference. This means that no matter how fast you are moving or in which direction, the speed of light will always appear to be the same.

What is the significance of the speed of light in a vacuum for the theory of relativity?

The speed of light in a vacuum plays a crucial role in the theory of relativity, as it is used to define the fundamental relationship between space and time. According to this theory, the speed of light is the maximum speed at which any object or information can travel, and it is the same for all observers.

What are the implications of the speed of light in a vacuum for our understanding of the universe?

The speed of light in a vacuum is essential for our understanding of the universe, as it allows us to measure distances and time intervals accurately. It also plays a crucial role in various physical phenomena, such as the behavior of electromagnetic radiation and the structure of space and time. Without the speed of light, many of our current theories and models of the universe would not be possible.

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