“JUDGE a man by his questions, rather than his answers,” Voltaire advised. Google has become one of the most successful firms in history by heeding that advice. It evaluates the intention of web-surfers’ queries and returns relevant advertising alongside search results. But for years there has been a lingering question about Google: can it create a new, highly profitable unit to rival its search business?

Not yet. In the past five years, Alphabet, formed as a holding company for Google and other disparate projects in October 2015, has spent $46bn on research and development (see chart). Much has gone to so-called “moonshot” projects, such as self-driving cars, smart contact lenses and internet delivered via balloons. Its British artificial-intelligence unit, DeepMind, also falls into the category of other projects. Since the start of 2015, these bets have together recorded a loss of $6bn.

Advertising still accounts for nearly 90% of Alphabet’s revenues and almost all of its profits, according to Brian Wieser of Pivotal Research Group in New York. Search advertising in particular makes up around three-quarters of Alphabet’s total ad revenues. (YouTube, a video site, and a business that places ads on non-Google-owned sites are other contributors.)

On December 12th Alphabet put its self-driving car project into a separate unit called Waymo so staff can better focus on achieving commercial viability. In truth it is not much of a separation, as the firm will still be inside Alphabet and will not disclose more financial details. Other splits have been more drastic. In the past six months executives overseeing several initiatives, including those focused on venture capital, drones, self-driving cars, high-speed internet and smart thermostats, have left. Alphabet has also been trying to sell its malfunctioning robotics business, Boston Dynamics.

The reason for these departures is Alphabet’s ambivalence about how tightly it should manage costs, say people close to the firm. When Nest, the thermostats maker, was acquired for $3.2bn in 2014, its executives were promised they could invest and expand their business for years. But when the Alphabet structure was suddenly adopted, the message changed. Overnight, units were expected to pay for their share of overhead, which irked some executives who remembered how the parent company had itself doled out big salaries and other luxuries (like free food). Few at the firm are optimistic that Alphabet is closer to devising a business as lucrative and large as search continues to be. As one former executive says, “You’re unlikely to win the lottery twice.”

Meanwhile, the way that people navigate their way around the internet is also changing, which could eventually pose a threat to Google’s search-advertising business. There are two big impending shifts. One is the use of voice as a way to get information, and the other is the rise of virtual assistants. Already, around a fifth of searches on Android devices are done by voice (as opposed to text), and that share will grow as speech recognition improves. Voice will also become more important with the spread of stand-alone devices that answer questions, such as Amazon’s Echo and Google’s own new product, Google Home, which do not support advertising.

As interactions with devices like these become more complex, people will be able to rely on them to complete tasks they might have done online, such as ordering gifts, booking flights and locating nearby stores. Although Google has helped bring about this future with its Home device, its snazzy virtual assistant that predicts users’ needs and its messaging app, called Allo, it is unclear that these offerings will be healthy for its bottom line. In future, “searches” will be more focused on completing tasks and fetching information in environments where it will feel dissonant for ads to appear, such as in messaging apps or on smart-home devices. “As Google shifts more away from being a search engine to an answer service, its utility will go up. But the business model will fall apart,” argues Ben Thompson, who writes Stratechery, a blog on technology.

As well as the fact that Amazon delivers ad-free information via the Echo, the retail giant poses a direct threat to Google because more people are starting searches for electronics and other kit directly on its site, rather than through a general search engine. By one estimate, 55% of internet users now begin researching products on Amazon, depriving Google of the opportunity to deliver an ad.

Alphabet has confronted worrisome transitions before, such as the shift from desktop PCs to mobile. Its ad business is still booming, because it devised a way to deliver ads on small screens. It is possible that Google’s ad model could in future shift to taking a fee for each transaction it facilitates. This is already the case in air travel: people searching for flights scan options via one of Google’s tools, and airlines pay if a person books a ticket. Google could do the same if someone said to their phone, “order me a pizza”. But how it would choose which firm to place the order with, and whether consumers would be happy with that order being routed to the firm that paid most, are tricky questions, to which it is unlikely that even Google knows the answer.