Quetelet had no idea how long the revolution would last, or whether the new government would support the completion of the observatory—or if it would even allow him to continue as Belgium’s head astronomer. It would prove to be a turning point in his life—and in the way society conceived of individuals.

Previously, Quetelet never cared much about politics or the complexities of interpersonal dynamics. He was solely focused on astronomy. He believed he could keep his distance from any social commotion, which he viewed as irrelevant to his lofty scientific endeavors. But when revolution erupted in his own backyard, affecting his observatory, human social behavior suddenly became very personal. Quetelet found himself longing for a stable government that passed sensible laws and policies that would prevent the sort of social chaos that had derailed his career plans—and that seemed to keep leading to upheaval all around Europe. There was just one glaring problem: Modern society seemed utterly unpredictable. Human behavior did not appear to follow any discernible rules, just like the universe had seemed so indecipherable before Isaac Newton.

As he contemplated the revolution that had put an end to his professional ambitions, Quetelet was struck with inspiration: Might it be possible to develop a science for managing society? He had spent his life learning how to identify hidden patterns in the heavens. Couldn’t he use the same science to find hidden patterns in the apparent chaos of social behavior? Quetelet set himself a new goal. He would apply the methods of astronomy to the study of people. He would become the Isaac Newton of social physics.

Fortunately for Quetelet, his decision to study social behavior came during a propitious moment in history. Europe was awash in the first wave of “big data” in history. As nations started developing large-scale bureaucracies and militaries in the early 19th century, they began tabulating and publishing huge amounts of data about their citizenry, such as the number of births and deaths each month, the number of criminals incarcerated each year, and the number of incidences of disease in each city. This was the inception of modern data collection, but nobody knew how to usefully interpret this hodgepodge of numbers. Most scientists of the time believed that human data was far too messy to analyze—until Quetelet decided to apply the mathematics of astronomy.

Quetelet knew that one common task for any 18th-century astronomer was to measure the speed of celestial objects. This task was accomplished by recording the length of time it took an object such as a planet, comet, or star to pass between two parallel lines etched onto the telescope glass. For example, if an astronomer wanted to calculate the speed of Saturn and make predictions about where it would appear in the future, he would start his pocket watch when he observed Saturn touch the first line, then stop the watch when it touched the second line.