2003-03-03 19:26 ☼ post
Jon Kleinberg, a professor of computer science at Cornell University, New York, has developed a method by which a computer can deduce the topics that are dominating discussion at a particular time. To do so, the system scans large collections of documents over long periods in an attempt to pick up sudden, rapid bursts of certain words (or burstiness).
The 150 term bursts [bottom of the page] of highest weight in Presidential State of the Union Addresses, 1790-2002. Jon Kleinberg’s web page has a lot of additional information as well.