Smith's characters never really appealed to me, but his science speculations were ahead of their time. Knowing about the SoL limitation, Smith attempted to create a method by which star travel would be possible. To this end he introduced "Inertialess propulsion." Basically, the spacecraft was submitted to a field that made its mass zero, making SoL travel possible. He suggested this in the 1930s. Now we have a proposed quantum particle and field that gives particles mass - the Higgs particle and field. Suppose the hypothesis proves correct. Once discovered, would a "Higgs Field Neutralizer" be all that far off? It would make travel to the stars instantaneous for the traveler (although to those left behind the SoL time would be apparent).