Xeinstein said:
What is the physics answer to the question of why light has an invariant speed
to anyone and everyone, other than this is what light is? There must be a
reason why light behaves this way (or perhaps not necessarily this way
always). I'd think something must have happened external to the light to give
it this peculiar property. Put it in another way, what's wrong with the
classical physics where velocity would follow the law of vector arithmetics,
when applied to light?
c = 1/sqr(Uo*Ep)... where Uo is the permeability and Ep is the permittivity for free space.
This relationship holds true because the speed of light (and of all electromagnetic phenomena) is determined at the aether level. It remains constant in all frames because it is not dependent on a coordinate system like matter with mass is. Since ratios like permeability and permittivity are determined at the aether level and the aether is immaterial and not bound by spacetime laws, 'c' can be frame independent.
The speed of light is frame independent, but it is dependent on the physical properties of free space, and free space is immaterial, with no landmarks, therefore, not subject to the laws of Relativity, like objects in spacetime are. That's why the speed of light is a constant unaffected by the speed of the observer or the observed.
The speed of light sets the scales. For fields to continue to work regardless of spacetime conditions there must be time and space distortions between the observer and the observed when dealing with relativistic speeds. This is where the principles of relativity and equivalency come from. Because a field's speed must not change regardless of relative motion, and because energy is finite, for reality to work, all parameters must be adjusted around the speed of light. This is why we get time dilation and length contraction.
Since the speed of light, hence, the propagation speed of fields, must remain constant for all the other fundamental constants to continue to be proportionally the same, process (mass) has to increase in order to keep up... to a point, once we go over the speed limit and fields can't keep up, matter disintegrates. When we reach the speed of light, wavelength and frequency drop to zero, waves become flat, devoid of any information, and we are back to being immaterial empty space.
Time and length contractions are real. They need to be in order for the Equivalency Principle and the laws of Thermodynamics to hold. Spacetime, or material space, is a product, not a fundamental or primary component of reality, and that is precisely what is claimed by Relativity. In spacetime, space-like separation is relative. If spacetime were primary then spatial extension wouldn't be variable or dynamic, but it is, it shrinks and expands, just like clocks run slower or faster, depending on energy usage vs. energy available.
Since the speed of light is constant and closely related to the Compton wavelength and the Schwarzschild radius, the universe is the same everywhere, independently from existing spacetime conditions. This means that matter will always have the same properties and behave the same way everywhere, regardless of the existing spacetime conditions, that a carbon atom will look and behave like a carbon atom anywhere in the universe.
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"...quantum field theory says that associated with any mass m there is a length called its Compton wavelength, lc, such that determining the position of a particle of mass m to within one Compton wavelength requires enough energy to create another particle of that mass. Particle creation is a quintessentially quantum-field-theoretic phenomenon. Thus, we may say that the Compton wavelength sets the distance scale at which quantum field theory becomes crucial for understanding the behaviour of a particle of a given mass. On the other hand, general relativity says that associated to any mass m there is a length called the Schwarzschild radius, ls, such that compressing an object of mass m to a size smaller than this results in the formation of a black hole. The Schwarzschild radius is roughly the distance scale at which general relativity becomes crucial for understanding the behaviour of a given mass. Now, ignoring some numerical factors, we have:
lc = hbar/mc
and
ls = Gm/c^2
These two lengths become equal when m is the Planck mass. And when this happens, they both equal the Planck length!"
------ John C. Baez (from "Higher-dimensional algebra and Planck scale physics", as it appeared on the book "Physics Meets Philosophy at the Planck Scale" by Craig Callender and Nick Hugget)