Once photography became more or less commonplace, one interesting phenomenon became noticeable: a sequence of pictures displayed rapidly will create the illusion of change. The eye holds an “afterimage” of what it perceived for a fraction of a second after its disappearance. The first devices to take advantage of this were essentially hollowed out drums set spinning to give strips of still pictures movement. Combining still photographs with these devices was the next step, taken up by Eadweard Muybridge.

On this day, June 15 in 1878 Muybridge set up 12 cameras along a racetrack, spread threads across the track and triggered each to a camera shutter. As the horse galloped along the track, it would trip each thread and create a sequence of photographs taken within seconds of each other.

Muybridge set up his experiment at the behest of railroad tycoon Leland Stanford, who had a bet on whether a racehorse ever had four feet off the ground at once. The photos proved the horse did indeed have all four feet off the ground at one point, and Muybridge went on a tour displaying the photographs on his own moving-image device he called the zoopraxiscope.