Why c, revisited still again

Give it a rest, Dale!

Because the velocity of narwhals is too variable.

The speed of light isn't really a speed. It's an asymptotic threshold to a relativistic energy curve.

Narwhals have a hard time with that too.

They're really pretty useless, quantum wise.

Of course. Goes without saying

But Con why
Returning to the OP isn't the difference in approach evident

Okay Ros but the q remains as to why it occurs at this particular….uhhh….velocity

The speed of electromagnetic radiation, including light, through any medium (including a vacuum) is determined by certain electromagnetic properties of that medium: the permittivity (capacitance per unit volume) and permeability to a magnetic field.

It's not about velocity Dale, it's about the structure of space time.

Thanks fellas

Apparently it's not an arbitrary velocity as I had assumed

I am wondering however, Con, whether either of these values might be set using the velocity of light c itself as a determinant

They can be derived independently (this is the whole point!); They arose from the work of researchers into electricity and magnetism mainly in the 19th century.

In 1851 Hippolyte Fizeau developed a method to determine the speed of light based on time-of-flight measurements on Earth and reported a value of 315000 km/s. His method was later improved upon by Léon Foucault who obtained a value of 298000 km/s.

In 1856, Wilhelm Eduard Weber and Rudolf Kohlrausch measured the ratio of the electromagnetic and electrostatic units of charge, 1/√ε0μ0, by discharging a Leyden jar, and found that its numerical value was very close to the speed of light as measured directly by Fizeau.

In 1857 Gustav Kirchhoff calculated that an electric signal in a resistanceless wire travels along the wire at this speed.

In 1862 James Clerk Maxwell (one of the giants of science) showed that, according to the theory of electromagnetism he was working on, what he called 'electromagnetic waves' propagate in empty space at a speed equal to the Weber/Kohrausch ratio, and drawing attention to the numerical proximity of this value to the speed of light as measured by Fizeau, he proposed that light is in fact an electromagnetic wave. These were later verified to exist and put to practical use (radio, lasers, etc).

http://en.wikipedia.org/wiki/Vacuum_permittivity
http://en.wikipedia.org/wiki/Vacuum_permeability

Thanks Con, your response much appreciated by us Average Clods

So I wonder whether it might not even be possible to address the relativistic changes in a moving body using language suitable to the Intuition. Okay the math shows that a moving body appears to gain mass as it clock slows down etc, but why, how