The woman who taught search engines which words matter

A closer look

Every time you Google a bizarre question at 3 AM and actually find the answer, you owe a debt to Karen Spärck Jones. In 1972, this British computer scientist introduced the concept of 'inverse document frequency' (IDF). It was a cynical but brilliant realization: words that appear everywhere are practically useless for searching, while rare words are absolute goldmines of relevance. She essentially taught computers how to judge the importance of text. For decades, her work was treated as an obscure academic curiosity, until the 1990s rolled around, the internet exploded, and suddenly every major search engine on Earth frantically built their algorithms on top of her exact mathematical foundation.