Mary Cartwright and the Birth of Chaos

On International Women's Day, we celebrate Mary Cartwright (1900–1998), who co-founded chaos theory in the 1940s — decades before Edward Lorenz's famous butterfly. Working with J.E. Littlewood on radio signals during WWII, Cartwright found that Van der Pol's differential equation produced wildly irregular, unpredictable behaviour for certain parameters. She was the first to recognise this as a fundamental mathematical phenomenon rather than an experimental error. She became the first woman elected to the Council of the Royal Society.