???? https://en.wikibooks.org/wiki/Fundamentals_of_Physics/Physics_and_Measurement A meter is a unit of length, currently defined as the distance light travels within 1/299782458th of a second. It is defined this way because the speed of light is known invariant. Before relativity, a meter was defined by a physical standard of length kept in a bell jar at controlled temperature and pressure. The standard was eventually changed to s standard number of wavelengths of photons produced by a particular hyperfine energy transition of a rare element. Of course, the invariance of the speed of light does not depend on any particular wavelength because they all travel at c in a vacuum. If you think this is a "crock", then the rest of your questions don't matter at all. Do you have this understanding or not? A light year is not the only standard to which light's invariance in a vacuum has been applied. It applies to literally dozens of them. A standard "Jiffy' is about a 20 picoseconds, or just under a centimeter of light travel time. A light nanosecond is about a foot in physical length. I used this relation frequently in a very long and successful engineering career, for phase tracking and group delay equalization, to name only two such applications. What technical career could you possibly have that you would think it was a "crock" that the speed of light was related to a standard of distance measurement? Have you not used any instruments that depend on calibration standards in your work? They are calibrated to laboratory standards traceable to these.