Mark Zuckerberg is searching for something. AP Everyone knows Google dominates search. It usually has roughly 70% market share of all search activity on the net. Microsoft's Bing comes a distant second.

But Google is facing a series of challenges that could upset that dominance. The challenge comes with a new type of search, called "latent," "abstract," or "conversational" search.

Until now, if you wanted to search for something on the web, you typed in keywords. Google has trained us all to type in those words in order of importance, not the order in which they make sense. In the future, that may change. Google, Facebook, and Apple are all developing tools that will allow us to search the way we speak naturally, even though searching for the kinds of non-specific, abstract, or latent concepts we use in real life — "where is a good place to eat dinner?" — generally produces useless search results.

Google speaks "Caveman English"

Larry Kim, founder of Wordstream, and an expert in search, described it to Business Insider this way:

People have become accustomed to desktop searches on Google in all sorts of strange broken up keywords. For example, for best search results, people often search on complex long tail queries like “directions black sand beach best Hawaii,” if they’re looking for directions for a beach in Hawaii. I call this “Caveman English” because if you read out the search queries it sounds very unnatural and more like something a caveman might say. I estimate that 20% of searches on Google are done using caveman English like this.

Facebook has recently rolled out Graph Search to all its U.S. users, and it's coming to all Facebook users worldwide soon. If you've ever tried to search for something on Facebook, you'll know how tricky it is. Regular keyword-type searches often have unsatisfying results. But use Graph Search to find out what your friends' favorite movies are, and the results can be fascinating. (My crowd favors "Best in Show" over "Citizen Kane." Hmm.)

The difference between Graph Search and Google keyword search is that on Facebook, you're searching for something where you don't actually know what the answer is — "latent" search. On Google, you're usually searching for something you know exists — "White House history," for instance.

Google's Larry Page Bing Maps Enter the Hummingbird

Google isn't sitting still for this, of course. Its big new "Hummingbird" algorithm change, rolled out over the last few weeks, has the ability to handle conversational search requests, such as, "How do I tie a bow tie?"

Google regards Hummingbird as the most significant change it has made to its core product since 2001.

To the layperson, this is going to feel dry and technical. Who cares if search engines get tweaked so they become easier to use?

People are moving from Google to Facebook

Recently, people began spending more time on average inside Facebook than with Google, according to comScore. Google's search empire is a $60 billion business. Facebook has a $6 billion empire, not based on search.

If Facebook were to fully develop a decent alternative search engine to Google — perhaps by teaching us to search for latent queries rather than keywords — then you could see how that might precipitate a tectonic shift in search marketing dollars. (Facebook so far has offered only limited Graph Search advertising.)

Kim says:

Now when it comes to mobile searches (which is slightly under half of total searches), an increasing share of queries are being done by voice, and as people, we’re not as good speaking caveman English out loud. So, the ability to process more natural sounding questions becomes key for improving relevancy.

Apple's Tim Cook Justin Sullivan/Getty Images The real purpose of Siri

And then there's Apple.

If you own an iPhone, you may wonder why Apple persists with Siri, its often less-than-convenient voice assistant. One reason is that Apple knows the future of computing is mobile, and it's often easier to speak to your mobile phone than type search requests onto it.

Again, if Siri was improved enough so that voice-activated mobile search with Siri became genuinely useful, iPhone users could switch en masse to Siri search rather than Google search.

That's a big speculative leap, of course, but Apple isn't afraid of big leaps.

Siri currently uses Bing for search, and Microsoft has a deal with Facebook where Bing is Facebook's search engine. Apple has the power to have Siri use whichever default search engine it chooses. It just switched from Google to Bing for iOS 7, the new operating system update. The alliances here are complicated, but they don't favor Google.

Google Glass v. Siri

Google has its own voice assistant on Android, which is more useful than Siri. It's hoping to lock in Android users to the Google search system, especially as Hummingbird has a conversational aspect to it.

And, of course, Google is developing Google Glass, the voice-activated smart eyewear it hopes will become commonplace one day.

Again, note that voice-activation is the key here.

All three companies appear to be anticipating a day when speaking to our devices replaces typing on them, which is why getting conversational search right could be the first, most important battle to win.

Disclosure: The author owns stock in Facebook and Google.