For example, space elevators, a long-time fantasy of Google's founders and other Silicon Valley entrepreneurs, could collect information or haul things into space. (In theory, they involve rocketless space travel along a cable anchored to Earth.)
"Google is collecting the world's data, so now it could be collecting the solar system's data," Brooks said.
Sergey Brin, Google's co-founder, is deeply involved in the lab, said several people with knowledge of it.
He came up with the list of ideas with Larry Page, Google's other founder, who worked on Google X before becoming chief executive in April, chairman Eric Schmidt and other top executives.
"Where I spend my time is further afield projects, which we hope will graduate to important key businesses in the future," Brin said recently, though he did not mention Google X.
Google may turn one of the ideas - the driverless cars that it unleashed on California's roads last year - into a new business.
Unimpressed by the innovative spirit of Detroit car makers, Google is now considering making them in the United States, said a person briefed on the effort.
Google could sell navigation or information technology for the cars, and theoretically could show location-based ads to passengers as they zoom by local businesses while playing Angry Birds in the driver's seat.
Robots figure prominently in many of the ideas. They have long captured the imagination of Google engineers, including Brin, who has already attended a conference through robot instead of in the flesh.
Fleets of robots could help Google collect information, replacing the humans who photograph streets for Google Maps, say people with knowledge of Google X.
Robots "born" in the lab could be destined for homes and offices, where they could assist with mundane tasks or allow people to work remotely, they say.
Other ideas involve what Google referred to as the "web of things" at its software developers conference in May - a way of connecting objects to the internet.
Every time anyone uses the web, it benefits Google, the company argued, so it could be good for Google if home accessories and wearable objects, not just computers, were connected.
Among the items that could be connected: a garden planter (so it could be watered from afar); a coffee pot (so it could be set to brew remotely); or a light bulb (so it could be turned off remotely).
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