"Sidewise in Time"
While physicists contemplate waveform collapse, author William Fitzgerald Jenkins writes of parallel worlds under the pen name Murray Leinster. In the story "Sidewise in Time," a mathematics professor named Minott predicts that patches of parallel universes—worlds where human history unfolded differently—will start to tear through into our reality. When that actually happens, Minott leads a band of students on an adventure across the parallel worlds, hoping to locate and rule a world that lacks sophisticated technology. "Sidewise in Time" isn't the first story to feature parallel worlds, but it does bring the concept to a pulp science fiction audience when the story is published in Astounding Stories in 1934.