“We have all had to take a deep look at what search really means in a world that has gone mobile,” he says. “Our heads explode when we think about this.”

For its entire 17-year history, Google Search has always been evolving, a process that the company often marks with celebratory blog items and an occasional press event. (Though when it comes to quantifying the changes, Google reverts to its usual dogged stinginess — for years, it has described the number of hints it uses to help rank search queries, known as “signals,” as “more than 200.”) Because Search remains the company’s flagship product — and the platform supporting the ads that are still Google’s dominant source of income — Google has never been complacent about improving the way that over a billion people find information in the course of a day. But in the past few years, the pace has accelerated, both in short- and long-term efforts, to keep Google ahead of its competitors.

Users can’t miss some of the changes. Search is faster, it’s fresher, and it’s more social (though after a big push on “social search” around the time Google Plus was launching, you don’t hear much about that now). Search even looks different. “In [earlier] days there was a lot less going on — we had the home page and search results,” says Tamar Yehoshua, one of the executives responsible for what Google calls the search experience. “Today we have lots of different features and products on the search results page.”

Looking ahead, Google has been pushing the frontiers of artificial intelligence to build a giant “brain” that will be able to much better understand both its users and the world, delivering on-target results even before people think to ask about it. (More on this later in this series.)

Yet some critics argue that Google search is on a downward slope. They gripe about too many spam results, or an overemphasis on newer information that occludes more relevant earlier results. You hear that the vaunted “ten blue links” have been polluted by a confusing and self-serving plethora of features like shopping, news, and multimedia results. (On the other hand, Google’s biggest US competitor, Microsoft’s Bing, crows that Google still has too much reliance on the ten blue links.) A Buzzfeed headline last year bleated, “We Are Entering the Worst Period in Modern History,” followed by the outright claim that “Google is becoming less useful.”

Singhal fiercely disputes this charge. “The truth is completely reverse,” he says. “I’ve looked into [these complaints] and I’ve discovered there is some nostalgia that they have for the past. Our search today is far better than it was last year or two years before.”

Singhal’s comments are indicative of the pride and confidence among key people in Google search these days. Only a few years ago, despite Google’s conviction that its search quality was incomparable, there were real fears that the company’s dominance might weaken. Google was in the throes of Facebook panic. “We don’t have those connections,” Singhal told me in 2011, clearly referring to Facebook’s network, which forbade Google’s crawlers. “I don’t know how information flows in those networks.” In the height of this mania, Singhal took on something of a Cassandra role at Google, at one point collaring the company’s head of social, Vic Gundotra, to unleash a self-described rant about how closed networks might threaten Google’s existence. If you suggested to Singhal that the threat did not square with Google’s unchallenged power in search, he had an answer to that: “Pan Am seemed pretty powerful when I was a little child, too,” he told me in that conversation.

But the fears turned out to be overblown; it’s unlikely that someone at Google these days would analogize the company to the failed airline that was once the world’s premier carrier. Facebook’s Graph Search, while still a nascent product, is off to a slow start and has little impact on Google. Bing, while Microsoft has made it a respectable competitor in search quality, still holds less than a fifth of the market. While Google Plus fell far short of the company’s attempt to finally create a blockbuster social networking product, it did succeed in getting many more search users signed in.

Instead of an Internet closed to Google by a single powerful competitor, the threat to search now appears to be an exodus from the web to a variegated archipelago of apps. (The movement to mobile also presents challenges to Google’s search ad revenue, but that’s a story for another series.) Google sees the rise of information within apps as something it can overcome — after all, mobile developers, like webmasters, want their information discoverable. Since the fall of 2013, Google has set up an App Indexing effort to encompass data inside mobile apps into its general index. Fifteen percent searches from signed-in Android users now yield results with information inside apps. Apps indexing, though, does not currently include iOS apps, a serious gap. “There’s still a long way to go, says Lawrence Chang, product manager for Apps Indexing. “But we’re building the fundamental blocks.”

But for now, the challenge of crawling the apps universe hasn’t affected Google’s search dominance. The statistics remain staggering. Google accepts over 3 billion search queries a day. In the US, two-thirds of all searches use Google — worldwide, there’s similar dominance. (A recent dip in market share is largely attributed not to search quality , but Yahoo’s deal to dislodge Google as the default search engine on Firefox). Even more impressive, Google hosts well over 80% of mobile searches. When Google suffered a five-minute outage in 2013, global web traffic dropped forty percent.

No search competitor has Google’s infrastructure, its deep talent, or its experience. Few have its ambition. So while news coverage of Google has dealt with regulatory issues, the fortunes and misfortunes of Glass, and the adolescent superstars of YouTube, Search has been going through a steady but intense reinvention.

In some ways, the changes are simply a continuation of the way Google has been evolving search since the beginning. On a micro basis, Google makes subtle changes in its algorithm, blessing the adjustments in its weekly search quality launch meeting. Then, every two or three years, there’s a major dustup in the ranking system, creating winners and losers among businesses scuffling to be highly associated with important keywords. The most recent of these was 2013’s update, dubbed Hummingbird, which involved a rejiggering of the importance of certain signals associated with search terms. According to Ben Gomes, who has been Singhal’s lieutenant in search leadership for over a decade, Google has made more changes to its rankings in the past three years than it did in the previous thirteen.