It is interesting to explore some issues about how google works. Actually, the basical components for a searching engine is very simple: web crawler, indexer and searcher. I can use Lucene to do indexing and searching part, but I am still curious that how google do web crawling and collect those useful informations. Google uses Googlebot to do those things while need handle lots of statistcs information for web pages, how can he do that? well, i know it is hard to say before doing some researching...again, for a good search engine, there are still lots stuff need to consider, page rank is only one of them, also not easy one.  More difficult or more intellegent, a perfect search  engine should "understand exactly what you mean and give you back exactly what you want." which is said by Larry Page.

Well, can not say that Google is not a miracle in technolgy field... also exciting to read those google stories

reference:
http://www.googleguide.com/google_works.html
http://www.google.com/technology/