What was Einstein’s real achievement in his 1905 theory of special relativity?

Several years before Einstein published his 1905 theory of special relativity, ether theorists had essentially discovered the main relativistic effects predicted by the theory: length contraction, time dilation and the relativity of simultaneity. In this lecture I will argue that Einstein’s work was more than a novel exercise in packaging (providing a “principle” rather than “constructive” approach). It also introduced a completely unprecedented way of understanding the physical meaning of the mathematics of motion.