Doppler effect, mass changes of objects, and all relativistic effects (v^2/c^2) are based on $c$ as the maximum velocity ($Vt$) in the Universe. We have a fairly good understanding of relativity (I will stop at SR). If $Vt$ was only slightly higher than $c$ (say 0.001%), then certain conflicts in physics could be resolved. For example, photons could then have a very insignificant rest mass, which would then match all the other photon physical characteristics and properties.

Therefore my question is - What is the experimental and/ or measured data for setting that ultimate velocity limit? Keep in mind that assuming 'nothing goes faster than the speed of light' is not what I am asking as it is generally agreed that we have not seen anything yet. Nor am I asking for mathematical assumptions that were then incorporated into the interpretation of the measured data, as this is circular logic.


closed as unclear what you're asking by knzhou, CuriousOne, heather, John Rennie, Qmechanic Aug 4 '16 at 21:45

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    $\begingroup$ Special and general relativity along with all the measurements validating them? $\endgroup$ – Sanya Aug 3 '16 at 21:26

Oddly enough the first experimental data for that choice originated in the nineteenth century.

You see, the Lorentz transformation arises as one of the symettries of electromagnetism, and the speed of light appears as powers of $\epsilon_0$ and $\mu_0$ (the permittivity and permiability of free space), which were measured with some attention to detail in the development of electromagnetism.

Demonstration that the symmetry present in Maxwell's equations also applied to material objects came later, but it is amply checked and rechecked at accelerators the world over year in and year out.


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