Why is the speed of light what it is?

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Discussion Overview

The discussion centers around the question of why the speed of light is what it is, exploring both fundamental understandings and the implications of measurement units. Participants delve into theoretical aspects, the relationship between physical constants, and the nature of speed as a concept in physics.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant queries whether there is a fundamental understanding of the speed of light similar to that of force and mass.
  • Another participant states that the speed of light can be expressed as \(\frac{1}{\sqrt{\mu_0 \epsilon_0}}\), linking it to the permittivity and permeability of free space, but acknowledges the ongoing question of why these constants have their specific values.
  • A different viewpoint suggests that the numerical value of the speed of light, 299792458 m/s, is influenced by human choices in measurement units, proposing that natural systems may prefer different units where the speed of light is normalized to 1.
  • Another participant notes that while the speed of light is dependent on the choice of units, its magnitude appears to have significance in relation to other physical phenomena, questioning why it takes a specific duration for light to travel certain distances compared to other measurements.

Areas of Agreement / Disagreement

Participants express various viewpoints on the nature of the speed of light and its dependence on measurement units, with no consensus reached on a fundamental explanation for its value or significance.

Contextual Notes

The discussion highlights the complexity of defining the speed of light, including the influence of measurement choices and the lack of universally accepted explanations for its specific value.

Who May Find This Useful

Individuals interested in the foundational concepts of physics, the nature of physical constants, and the implications of measurement systems may find this discussion relevant.

cybernomad
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I'm a newbie here - this is my first post - and have interest in physics. Now we understand if force ‘a’ is applied to mass ‘b’ for ‘c’ seconds we can determine it velocity in the absence of any friction or other force.

So my question is do we have a similar fundamental understanding of the speed of light of why it is what it is?
 
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We do know that the speed of light is [tex]\frac{1}{\sqrt{\mu_0 \epsilon_0}}[/tex]

[itex]\epsilon_0[/itex] is the permittivity of free space, [itex]\mu_0[/itex] is the permeability. The speed of light is a cosequence of these two numbers via maxwell's equation.

Of course, you can always ask why these parameters have the values they have. (But in general one can always keep asking "why this? why that? why the other thing?).
 
cybernomad said:
So my question is do we have a similar fundamental understanding of the speed of light of why it is what it is?
Speed is (measurement unit)/(measurement unit). The fact that the speed of light happens to be the seemingly random number 299792458 m/s is a result of mankind's choice of units for time and space, which is obviously not Nature's preference. These units are often redefined in relativistic calculations so that the speed of light becomes exactly 1, which is probably more in line with the system of units that Nature prefers.
 
The numerical value of the speed of light of course depends on our choice of units for distance and time. Nevertheless the speed of light has a sort of magnitude that is independent of those units, because we can relate the traveling of light to other physical phenomena.

For example, the speed of light (in whatever units) is such that it takes about 4.3 times as long for light to travel from Earth to Alpha Centauri, as it does for the Earth to travel once around the sun, as measured in the Earth's reference frame. Why not 43 times as long, or 4300?

As far as I know there is no generally accepted explanation for why light travels at the first speed and not the other ones. I can't even think of any non-generally-accepted explanations, off the top of my head.
 

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