Google News: How does the search giant's headline aggregator work?

Google News is checked by millions of people on a daily basis looking for quick access to a range of coverage of a given event or issue. It was founded by software developer Krishna Bharat in 2002 in response to the scramble for news that followed the attacks on the World Trade Centre on 11 September 2001. The service collects and ranks all articles on a particular topic then making international headlines into clusters, allowing readers to choose which publication's account they read. But how does Google rank the content it shows? Rather than a physical team of news editors, Google relies on an algorithm whose methodology, like Colonel Sanders' recipe for fried chicken, is a closely guarded secret.