He Wouldn't Fly Until She Checked the Math

In 1962, NASA had shiny new electronic computers, and John Glenn was about to trust one with his life. He had one condition before he'd fly around the Earth. Get the girl, he said, to check the numbers.

"The girl" was Katherine Johnson, a mathematician from West Virginia who had been doing by hand what the machines were just learning to do.

Johnson was a prodigy, in college at fifteen, done at eighteen. NASA's predecessor hired her into a pool of Black women mathematicians who were literally called computers: they computed. Flight paths, wind tunnel results, trajectories, all of it worked out on paper, precisely, because a wrong digit meant a lost pilot.

In 1961 she calculated the trajectory for Alan Shepard's flight, the first American in space. The path up and the path home: her arithmetic.

So when Glenn prepared to orbit the Earth and the numbers came from an electronic computer nobody fully trusted yet, he asked for Johnson to run the same calculations by hand. If her numbers matched the machine's, he would go. They matched. He went. He came home.

“The machine was checked against her, not the other way around.”