The thought problem in section 7 of “Relativity” is the beginning of Einstein’s rationale for using his version of Lorentz Transformations. He uses a railroad embankment as one “rigid reference-body (frame)”, and a train car on the tracks moving at a constant speed parallel to the embankment as a second (inertial)“rigid reference body”. He has removed the air above the embankment so his “ray of light” will be propagated in a vacuum. He does this is to demonstrate why simple addition of velocities won’t work the same for the light in this thought problem as it did for a man walking along the railroad car in the same direction as the train’s motion in section 6 of “Relativity” where he demonstrated the “theorem of the addition of velocities” in regard to the speed of the man relative the embankment. (W = v + w) The question posed by Einstein in his section 7 problem is this: “If a ray of light is sent along the embankment, we see from the above that the tip of the ray will be transmitted with the velocity c relative to the embankment. ---” The unknown of the problem is the speed of the tip of the ray relative to a train carriage moving at speed v (relative to the embankment) in the same direction as the light. He sets up an equation using the standard equation for an addition (or in this case, subtraction) of velocities problem with the resultant velocity w as the unknown: w=c-v. It is Einstein’s next comment that is the beginning of his justification for using the Lorentz Transformations: “The velocity of propagation of a ray of light with respect to the carriage thus comes out smaller than c.” That of course violates the second postulate of Special Relativity and leads him into his famous statement at the end of this same section. “As a result of an analysis of time and space, it became evident that in reality there is not the least incompatibility between the principle of relativity and the law of propagation of light,----” And we’re off Galilean/Newtonian Universe out; Time dilation, rod shortening, speed limits and eventually the curving space-time continuum in. Some time ago I began to wonder what would happen if I put actual numbers into Einstein’s section 7 problem. This is what I found: a light flash begins from a source situated 100 meters away from a point (A) on the embankment at the moment a mirror on the back of the carriage aligns with point A. The carriage is moving 100km/h. It will take the “tip of the ray” 1/3rd of a microsecond (333ns)to reach point A on the embankment but the train will only have moved .00925 millimeter in that time. The “tip of the ray” will cover that extra distance in .030833ns. Obviously these are distances and intervals far too small for human observers to perceive. But what if the speed of the carriage is 200,000km/sec. (2/3 c). As before the tip of the ray of light will reach point A on the embankment in 1/3rd microsecond in which time the train will have moved a very perceptible 66.6 meters. The light will catch up to the observer on the train in just 1 microsecond from its starting point at a point 200 meters from the observer on the embankment. Though a human observing from Einstein’s omnipotent point of view would clearly see the 200 meter difference, he would not likely be able to perceive a time difference of only 1 microsecond. (Light traveling at c moves 300m/microsecond.). So it would appear to the observer that the light arrived at both the point on the embankment and the mirror on the train 200 meters down the track simultaneously. If the reflected light from the mirror is accurately timed it will be back at the source exactly 2 microseconds from when it began and if you could substitute an accurate measuring device for the mirror it would be measured as exactly c. I don’t think there is a problem here for either of Einstein’s Special Relativity postulates but for me it puts up a big question mark about the rationale for his use of the Lorentz Transformations and all of the phenomena that derive from. That doesn’t necessarily prove that none of those are true, it just seems to negate Einstein’s pathway to them. The Lorentz Transformations are the only math Einstein used in relation to Special Relativity. Am I missing something here? Please tell me the flaw in my reasoning.