Learning how Google really works

May 9, 2012, 2:15 PM UTC

FORTUNE — Google is notoriously (and understandably) tight-lipped about the details of its algorithm — the formula that determines how search results are presented. But the company also seems to genuinely try to help explain, to the extent that it safely can and in broad terms, the thinking that goes into how it tweaks the algorithm to return the most relevant results.

This is far from a simple proposition. Figuring out what millions of searchers are looking for and matching them with the best possible results for each of their particular needs is an incredibly complex undertaking. The people who most want to know how it all works are, of course, Webmasters. For them, Google (GOOG) has a YouTube channel called GoogleWebmasterHelp that offers short videos responding to user questions. That it’s for Webmasters shouldn’t dissuade all interested parties from checking it out — the explanations are pretty clear and often enlightening.

Tuesday’s entry takes on a basic issue: “Does Google try to return results based on signals other than popularity?”

We should hope so, because if popularity alone drove results, searches on “particle physics,” “birdwatching” and “tennis tips” would yield nothing but porn and stuff about Lindsay Lohan. “A lot of people visit porn sites,” says the video’s host, “but very few link to porn sites.” He says that “reputation is different from popularity and PageRank codes that pretty well.”

This might be somewhat disingenuous. Many, many people link to porn sites. In fact, much of that industry relies on so-called thumbnail sites to drive traffic. There is clearly something else at work that pushes porn results down, which of course is preferable for most of us who aren’t looking for porn. Note for example that searching on “redhead” returns all kinds of non-porn-related sites at the top of the results. We must assume that a huge number of sites link that term to porn, but somehow, they are filtered out, meaning that porn-searchers would have to be more specific in their search. Good.

Interestingly, the host also notes that if, for a particular search, Google doesn’t satisfy, there are options. “If Google isn’t doing a good job, I do think that Bing (MSFT) or Blekko or Duck Duck Go or other search engines in the space will explore and find other ways to return things.”

Are you listening, Justice Department?