Heddy Lamarr was born Eva Marie Kiesler in Vienna, and married the arms manufacturer Fritz Mandle. She once recommended that he use radio waves to guide his missiles, but others pointed out that radio waves can be jammed, and so a radio-controlled missile would probably go astray. She didn't pursue the idea, and when the Second World War broke out she left her husband and fled to America. Having already made her name in the explicit German film Ecstasy, she was soon approached by Louis B Meyer, who persuaded her to sign a contract for the MGM studio.
One evening, while chatting to the composer George Antheil in a noisy room, Lamarr realised that they could hear each other more clearly when they sang to each other. When they spoke, their dialogue was being jammed by the noise around them, but when they sang, hopping from one note to another, their words became much clearer. Lamarr immediately thought back to her musings on missile guidance and imagined a radio-control system that hopped randomly between different frequencies. It would be impossible for the enemy to jam such a communication channel, because it would be changing frequency continually and unpredictably.
Lamarr and Antheil received a patent for their idea in June 1941. They suggested using a punched paper tape, similar to the type used to play a pianola, to control the frequency hopping. As long as the controller and the missile had the same tape, they would be able to synchronise their frequency hopping and maintain a communication channel. Unfortunately, paper tape was not really up to the job, and it would take several years before the technology would become available to properly implement the idea.
Lamarr was keen to continue inventing, but Meyer convinced her that she should concentrate on making films and raising the morale of the nation. Hence, her most famous contribution to the war effort was to raise money by selling kisses. She raised over $7m, sometimes selling a single kiss for $50,000. Although proud of filling America's coffers and lifting spirits, she was slightly ashamed that she was wasting her brain. She once famously said: "Any girl can look glamorous. All you have to do is stand still and look stupid."