We all know Google is the most popular search engine in the world, and there are numerous reasons for that. Its uncluttered interface, for instance. When several search engines are busy putting unrelated advertising links on their homepages, Google's page with its simple search box with two buttons come as a breath of fresh air.

But the main reason behind Google's worldwide popularity and its entry into popular culture is its extensive database of links, which at the last count, has exceeded one trillion.

Two Google engineers on Friday said that Google's index of the Web now contains 1 trillion unique Uniform Resource Locators (URLs). In 1998, when Google opened for business, it had 26 million URLs.

By 2000, it had reached 1 billion.  In 2005, Google claimed it had more than 8 billion Web pages in its index, at least until it took the index count off its home page. In 2008, Google's measure of the Web is 1 trillion Web pages.

Jesse Alpert and Nissan Hajaj, software engineers from Google's Web Search Infrastructure team, admitted that Google doesn't know the total number of pages on the World Wide Web because they ''don't have time to look at them all''.

Moreover, ''strictly speaking, the number of pages out there is infinite - for example, web calendars may have a "next day" link, and we could follow that link forever, each time finding a "new" page'' – without much user benefit. However, they asserted they are ''proud to have the most comprehensive index of any search engine, and our goal always has been to index all the world's data''.

They said that ''Google downloads the web continuously, collecting updated page information and re-processing the entire web-link graph several times per day'' and described the graph of one trillion URLs as being similar to a map made up of one trillion intersections.

To put things into perspective, the engineers described Google's daily work as the ''computational equivalent of fully exploring every intersection of every road in the United States. Except it'd be a map about 50,000 times as big as the US, with 50,000 times as many roads and intersections.''

It had been a while since Google had made public pronouncements about the size of its index, a topic that routinely generated controversy and counterclaims among the major search engines years ago.

Those days of index-size envy ended when it became clear that most people rarely scan more than two pages of Web results. In other words, what matters is delivering 10 or 20 really relevant Web links, or, even better, a direct factual answer, because few people will wade through 5,000 results to find the desired information.