The Jewish calendar has been closely tied to mathematics for centuries—but it wasn’t until 1977 that Hebrew dates could be calculated by a computer program. The breakthrough was the work of retired human “computer” Ida Rhodes, born Hadassah Itzkowitz in 1900. Let’s dive into this edition of Pioneers in Tech.
From mathematical prodigy to government computing pioneer
Rhodes and her parents immigrated from Ukraine to the Lower East Side of New York City in 1913, and she took the unusual step for a woman of her time of earning bachelor’s and master’s degrees in mathematics from Cornell University. Rhodes join the Mathematical Tables Project (MTP) in 1940. Founded in 1938, the MPT had a unique mission: Employ the unemployed by having them create tables of math functions for use in government projects, including air navigations, bombing strategies and even the Manhattan Project.
After the government abandoned the MTP, Rhodes took her skillset to Washington, D.C., where she worked for the National Bureau of Standards. From 1947 to 1964, she worked on programs for the U.S. Census Bureau and the Social Security Administration, pioneering the use of computers for automated translation work as well as working on computer access for those with visual and hearing disabilities.
Like so many technology pioneers, Rhodes was remarkably prescient. In a short 1952 essay titled “The Human Computer’s Dreams of the Future,” she declared portability to be one of her top desired features for an electronic computer, writing: “I expect that the superb advances made by the electronic engineers in miniaturizing the components … is bound to result in truly portable and easily serviced computing machine[s] so I like to think of the day when one of those precious toys would be sitting on my desk.”
Cracking the code of the Jewish calendar
It was in retirement that Rhodes tackled the Jewish calendar, which differs from the civil calendar in that it’s based on coordination of the Earth’s rotation, the lunar cycle, and the Earth’s revolution around the sun—a programming challenge indeed. But Rhodes’ formula simplified the calendar algorithm developed by mathematician Carl Friedrich Gauss and made it possible.
Rhodes passed away Feb. 1, 1986, in Maryland.
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