From "The conceptualization of time and the constancy of the speed of light", Vasco Guerra and and Rodrigo de Abreu. I just came across this article which proves that the speed of light had to be constant by just assuming "good" clocks record time correctly irrespective of orientations. Consider 2 similar (Feyman) clocks that record a "tic-tac" round trip period with a light photon reflected perpendicularly by 2 parallel mirors. Rotating one 90 degree gives the equivalent of the Michelson Morley experiment ! Thus the constancy of the speed of light. Seems brilliant, but I am no physicist. Can someone comment. Are these authors first with this idea.