Muybridge set out to answer the popularly-debated question of the day: whether during a horse's trot, all four hooves were ever off the ground at the same time.
By 1878 Muybridge had successfully photographed a horse in fast motion using a series of twenty-four cameras. The cameras were arranged along a track parallel to the horse's, and each of the camera shutters was controlled by a trip wire which was triggered by the horse's hooves.