Google's Search Secret Revealed

Page rank is key to its success

Imagine a library containing 25 billion documents but with no centralised organization and no librarians. In addition, anyone may add a document at any time without telling anyone.

You may feel sure that one of the documents contained in the collection has a piece of information that is vitally important to you, and, being impatient like most of us, you'd like to find it in a matter of seconds. How would you go about doing it?

Posed in this way, the problem seems impossible. Yet this description is not too different from the World Wide Web, a huge, highly-disorganized collection of documents in many different formats.

This article in the American Mathematical Society describes Google's PageRank algorithm and how it returns pages from the web's collection of 25 billion documents that match search criteria so well that "google" has become a widely used verb.