It was not too long ago that I was concerned about how I would carry all my books to continue my research after retirement. Today, because of the advent of the Internet the problem no longer exists, and the main reason for that is the development of the theory of search engines on the Internet. With the imminent availability of a computer for every child, it looks as though any child should be in a position to shake up the world, if he so desires.

Here we might as well mention a serious problem we are currently facing. We have already collected an enormous amount of data about our universe, as exemplified by the several billions of pages surfed by Google. Since it is obvious that not all these pages can possibly be significant, our immediate problem is to weed out the irrelevant pages from our collection. Fortunately for us, there is a good mathematical theory behind the ranking of the web pages, and this blog gives my thinking about the subject.

Using Perron-Frobenius theorem, four stochastic matrices are defined, that can be used to rank the pages and hyperlinks in the Web. For the mathematical details visit