The ability to capture motion in photography opened up a previously invisible source of scientific data. Etienne-Jules Marey was a scientist trying to understand biomechanics, or the motion of the body, and he used photography to acquire information he couldn't get any other way, as in this photograph of a man on a stationary bicycle.

"What happens in this picture is that each split second exposure is layered on top of each other, so you get the sense of the full arc of the motion," Keller said. "And he's put a piece of tape down the arm and torso and the leg where the joints articulated, so as the leg went around and around the whole pedal stroke is outlined."

This wasn't just to create beautiful pictures; Marey was on a committee in France to improve the ergonomics of the newly popular bicycle.

"So by studying the motion of the leg, he would have been able to improve the engineering of the bicycle," Keller concluded.