It is clear that we argue “Light Speed is independent with the Light Source or not”. Let’s discuss more detail:
SR introduced a stationary frame, lets call O; a moving frame, call A, with speed relative to O is V1; and also introduced a special frame-Light Source frame, call L, with speed relative to A is V2. If “Light speed is independent to light source” is truth, then the L frame could be any speed relative to A under one condition: at initial time T=0, O,A and L overlay together, the rest situation will be exactly same discussion in SR. SR only discussed two special situations: V2=0 (rested with O frame), V2=V1 (rested with A frame). When analyzed time, SR used V2=V1 situation (1/2 total time=forward time), when analyzed speed and time relationship, used V2=0, this randomly choice also cause confusion. If V2≠0 and V2≠V1, after certain time, L could appear any location along x axis, it may appear at left of O, between O and A, at right of A, even right of B (A, B is the end of long bar in SR), question: How to choose the light path to create the equations as SR?
Many experiments shown the light speed is independent from light source, is this only way to explain such strange postulation? When Maxwell developed electrodynamics, many people believed that the ether exist, late proved it was wrong. Michelson-Morley experiment may easy explain that all equipments and light source stayed in the same frame. There are many article in cyber that disprove those experiments, I have no time and ability to study and make explanations here. I only focus the SR 2nd postulation problem. Assuming the SR just creates now and people try to understand or not agree with their fresh mind, what will you make decision?