Few sounds say “rocket launch” quite like a voice counting backward toward zero. But the familiar launch countdown became famous before humans had anything remotely capable of reaching space.

In 1929, German filmmaker Fritz Lang used a countdown in his silent science-fiction film Woman in the Moon, about a crew traveling to the Moon. As the fictional rocket prepares to launch, the film counts backward toward the moment of ignition, ending not with “zero,” but with the German word JETZT: NOW.

Lang's reason was wonderfully practical: suspense. If you count upward, the audience doesn't know when the launch is coming. Count backward, and everyone knows exactly how much time remains.

The movie took its rocketry seriously. Lang had hired pioneering rocket scientist Hermann Oberth as a technical adviser, and the film became influential among the small community of engineers then trying to turn spaceflight from fiction into reality.

Before long, the cinematic device became part of real rocketry. German rocket engineers adopted countdown procedures, and the practice ultimately became standard in modern spaceflight.

Lang wasn't the first person ever to count backward toward a dramatic event; examples appeared in fiction decades earlier. But Woman in the Moon helped give the rocket launch its countdown.

A filmmaker trying to make a fictional trip to the Moon more exciting helped create a ritual that accompanied the real one 40 years later.