A seismic recording device on Mayotte was the first to detect the hum, though not the first one people noticed. Mark Tingay (@CriticalStress_) processed the data to create this image. (Image credit: Mark Tingay) There was a hum that nobody could hear. It was a seismic event, one that originated off the coast of Mayotte on Nov. 11, a tiny island in the waters between Madagascar and Mozambique. From