Looked on as drudges, human computers spat out calculations for decades
For two centuries they were the blue collar workers of science, mental laborers who could grind out logarithms as efficiently as other factory workers turned out pins. A large percentage of them were women. Though male scientists deemed creative mathematics beyond feminine abilities, they saw women as perfect for this kind of numerical needlework. One even measured computing time in "girl hours": A complex calculation might even require "kilo-girl-hours."
In "When Computers Were Human," David Alan Grier tells the tale of these human drudges of mathematical calculation. They came in with the 18th-century Industrial Revolution and quickly disappeared in the mid-20th as electronic computers proved to be faster and, eventually, more reliable.
Most of the human computers left no record of their personal lives. They didn't think they were doing anything remarkable as they calculated using ink and paper and, later on, early mechanical computing machines like the Felt & Tarrant Comptometer or the Burroughs Arithometer.
One of the earliest human computers was Nicole-Reine Lepaute, the wife of France's royal clockmaker. In the 1750s, teamed with two male colleagues, she did some fancy figuring to predict the return of Halley's Comet in 1758 after a 76-year absence. The team's estimate was off by just over a month.
A few computers were innovators. In the early 20th century, Mary Clem, a woman with only a high school education working at the Iowa State Statistical Lab, developed her own system of "zero checks" for detecting errors in calculations.
Foreshadowing today's networked computers, human computers learned to divide up complex tasks. They cross-checked and doublechecked to winnow out errors.
A supervising computer, called the comparator, checked the work and searched for discrepancies.
By 1940, the Mathematical Tables Project, a giant effort funded by the Works Progress Administration, still employed more than 300 human computers, half of them using paper and pencil. But in 1952, IBM began selling its Model 701 electronic computer. By the 1960s, nearly all the number-crunching was being done by machines.
Grier has a knack for making elaborate scientific concepts understandable. His opening device, in which he tries to discover why his grandmother told him proudly that she took calculus in college in 1921, lends a human note.