Horse in Motion
It may come as a surprise in the twenty-first century to discover that, in the 1880s, details of how objects move were unknown. The human eye, unaided, cannot resolve the details of fast motion. Eadweard Muybridge and his experiments with motion photography, such as this series of pictures of a horse's gait, helped solve this mystery.
From http://www.hrc.utexas.edu/exhibitions/permanent/windows/southeast/eadweard_muybridge.html - edited
Eadweard Muybridge
Eadweard Muybridge (9 April 1830 – 8 May 1904, born Edward James Muggeridge) was an English photographer important for his pioneering work in photographic studies of motion, and early work in motion-picture projection.
In the 1880s, Muybridge entered a very productive period at the University of Pennsylvania in Philadelphia, producing over 100,000 images of animals and humans in motion, capturing what the human eye could not distinguish as separate movements. He spent much of his later years giving public lectures and demonstrations of his photography and early motion picture sequences, travelling back to England and Europe to publicise his work. He also edited and published compilations of his work, which greatly influenced visual artists and the developing fields of scientific and industrial photography.
From https://en.wikipedia.org/wiki/Eadweard_Muybridge - shortened