The Woman Who Checked the Machine

Katherine Johnson was born on August 26, 1918, in White Sulphur Springs, West Virginia, a mathematical prodigy who finished high school at fourteen and college at eighteen. For a brilliant Black woman with a gift for numbers in the 1930s, the available job was teaching, and she taught. Then, in 1953, she joined a pool of "human computers" at the Langley laboratory of what would become NASA — women, segregated into a separate unit, who did by hand the calculations that the space program ran on.

Johnson at NASA Langley Research Center, 1980. NASA, Public domain, via Wikimedia Commons

She was too good to keep in the pool. Engineers pulled her into the Flight Research Division, where she worked the hardest problem in spaceflight: the trajectory. To put a person into space and bring them home is to throw a human being at a moving target — a capsule at a spinning Earth — and be exactly right, or lose them. Johnson calculated the trajectory for Alan Shepard’s 1961 flight, the first American in space. There was no margin for a rounding error.

Her most famous moment came in 1962. NASA had begun using electronic computers to compute orbital paths, but the machines were new, and nobody fully trusted them yet. Before his Friendship 7 orbital flight, John Glenn asked the engineers to "get the girl to check the numbers" — meaning Johnson — and said that if she confirmed the computer’s output by hand, he was ready to go. She ran the equations herself. He flew. It is one of the great moments in the history of people and machines: the astronaut trusted the human, and asked her to vouch for the computer.

Johnson at NASA Langley, 2014, honored late in life for work long kept invisible. NASA, Public domain, via Wikimedia Commons

She helped calculate the trajectory for Apollo and the Moon landing of 1969, and later worked on the Space Shuttle. For decades her contribution was invisible to the public — a Black woman’s mathematics underwriting the space race, uncredited outside the agency. The 2016 book and film "Hidden Figures" finally told the story, and in 2015 she received the Presidential Medal of Freedom.

Katherine Johnson died on February 24, 2020, at one hundred and one. Her career is a quiet argument about people and machines that only grows more relevant: the computer did the arithmetic faster, but a human being had to be trusted to know it was right. Long before we started asking whether we can rely on the machines we build, an astronaut answered by asking a mathematician to check one. NASA later put her name on the building where it does its computing.