Today's Google doodle--the occasional replacement for the logo at the top of the Google search page--commemorates the 182nd birthday of Eadweard Muybridge, the photographer credited with the historic experiment that formed the foundation for motion pictures, especially animation.
It's a matrix of stallions seen in profile, and by clicking the "play" icon in the center, the stallions slowly begin to run and gallop across the screen. In addition to being one of only a dozen or so animated doodles out of approximately 1,000 Google has done, it's also one of the few that doesn't obviously incorporate the company's name.
At its core, the doodle is actually a tribute to an 1878 experiment funded by former California governor Leland Stanford. Fifteen years out of the California governor's office and thirteen years ahead of founding the university named for his son, Stanford believed that the stallions at his Palo Alto farm lifted all four hooves off the ground when they ran. He hired photographer Muybridge to prove him right.
Over several years, Muybridge had unsuccessfully tried to capture the horses' hooves off the ground as the horse was ridden (as the Google image shows). The tests didn't work until he set up 12 cameras attached to 12 wires across a running track on Stanford's farm and had a trainer behind the horse in a sulky, so that the sulky's wheels tripped the cameras. As described in a 2001 Stanford magazine article, "When a sulky wheel rolled over one of the wires, it completed an electrical circuit, tripping the shutter of the attached camera. The shutters firing in quick succession sounded like a drumroll."
The result was a set of photographs that played in succession showed the horse's hooves were all off the ground simultaneously. The concept of having single frames shown in succession became the basis for motion-picture photography.