The astronauts, by background and by nature, resisted the computers and their ghostly intellects. In a test flight, a pilot staked his reputation and his life on his ability to exercise total, direct, and constant control over the plane. A tiny error of judgment or a spec of delay in deciding on a course of action might mean the difference between safety and calamity. In a plane, at least, it was the pilot’s call; the “fly-by-wire” setup of the Mercury missions, here the craft and its controls were tethered via radio communications to the whirring electronic computers on the ground, pushed the hands-on astronauts out of their comfort zone. Every engineer and mathematician has a story of double-checking the machines’ data only to find errors. What if the computer lost power or seized up and stopped working during the flight? That too was something that happened often enough to give the entire team pause. The human computers crunching all of those numbers—now that the astronauts understood. The women mathematicians dominated there mechanical planes. The numbers went into the machines one at a time, came out one at a time, and were stored on a piece of paper for anyone to see. Most importantly, the figures flowed in and out of the mind of a real person, someone who could be reasoned with, questioned, challenged, looked in the eye if necessary. The process of arriving at a final result was tried and true, and completely transparent. Spaceship-flying computers might be the future, but it didn’t mean John Glenn had to trust them. He did, however, trust the brainy fellas who controlled the computers. And the brainy fellas who controlled the computers trusted their computer, Katherine Johnson. It was as simple as eighth-grade math: by the transitive property of equality, therefore John Glenn trusted Katherine Johnson. The message got through to John Mayer or Ted Skopinski, who relayed it to Al Hamer or Alton Mayo, who delivered it to the person it was intended for. Get the girl to check the numbers,” said the astronaut. If she says the numbers are good, he told them, I’m ready to go.

The results were what mattered, she told classrooms of students. Math was either right or wrong, and if you got it right, it didn’t matter what color you were.