I posed the question earlier with no takers.

I repeat with an explanation.

We recite that light travels at about 186,281 miles per second because that is what we measure in this solar system. Forget that reference data.

Who and how does science prove that the measured speed is what it should be everywhere? What mathmatics are there to prove our sun produces light at that speed because of some physical factors that are measurable? Does the assumption exist solely on the basis that the speed measured must be the speed every where? No proof required to arrive at reasons for 186,281 miles per second?
jjw