Why did experts say computers could never understand English?

When Grace Hopper proposed building a programming language made of English words, she was told, very quickly, that it couldn't be done, because computers didn't understand English. She pushed ahead anyway, reasoning that it's much easier for most people to write an English statement than to use symbols, so data processors ought to be able to write 'Subtract income tax from pay' and let the machine translate it into code.

Her idea sat unaccepted for three years. By 1952 she had a working 'compiler' (an early program that today would be called a link-loader), and still nobody believed it: 'They told me computers could only do arithmetic,' she later said. She pressed on regardless, and in 1954 was named her company's first director of automatic programming, releasing some of the earliest compiled languages. In 1959 a committee built on her ideas to create COBOL, which became one of the most widely used business programming languages in history.

Hopper had been curious about how things worked since childhood; at seven she took apart seven alarm clocks just to see their insides, until her mother limited her to one. That same curiosity carried her from a math PhD at Yale, through a wartime commission in the Navy, to the Harvard Mark I computer team in 1944. In 1947, while she was working on its successor, the Mark II, her team found a moth stuck in a relay and taped it into their logbook with the note 'First actual case of bug being found' ; Hopper is credited with popularizing the word 'debugging' afterward, and the moth's remains still sit in that logbook at the Smithsonian.

Later in her career, when generals and admirals asked her why satellite calls took so long, she handed them foot-long pieces of wire: the distance light travels in one nanosecond. Apart from building the compiler, she said, the most important thing she had accomplished was training young people: when they asked if something could be done, she told them to try it.