Nick Bilton/The New York Times

MENLO PARK, Calif. — Millions of people watched a robot descend last week on Mars , about 154 million miles away, while it shared video, photos and status updates from its own Twitter account

I had my own encounter with a robot last week. I had dinner with one — right here in Silicon Valley.

The dinner was at Willow Garage, a robotics company in Menlo Park, and was intended to introduce some reporters to the robots the company is building.

The main attraction was the PR2, which can pick things up, fold laundry, open doors and bring cups, plates and other small objects to people. The PR2 is pretty stunning to see in action. Its price, $400,000 for the fully functional version, is pretty stunning, too. And although it is impressive to watch, it is still easily baffled by the mundane.

At the dinner, one of the PR2s dropped a soda can on the floor and just stood there, befuddled. It couldn’t figure out what had happened to the can. It was as if it had just performed a wonderful magic trick on itself.

It is hard to know how many robots are in use today because roboticists disagree on what a robot is. Must it have arms, or artificial intelligence, or facial recognition? The earliest definition of the word, which comes from the Czech word robota, means “forced labor,” or “slave.”

Robotics companies give various estimates for the numbers of robots in use. Whatever the numbers, people like Steve Cousins, Willow Garage’s president and chief executive, think robots will become a lot more mainstream in the not-too-distant future.

They point to the Roomba and other robots made by iRobot, which the company says are already cleaning floors, pools and gutters in more than eight million homes and offices. The United States Army has robots to disarm bombs on the battlefield. And an intimidating robot, Big Dog, made by Boston Dynamics, is being built to replace some soldiers in battle.

Roboticists say the price of these machines will begin to drop sharply, which, in turn, will make the use of robots in homes and offices more widespread.

Mr. Cousins said he believed the next wave of robots to enter — or invade — the home and work force would be telepresence robots. These machines have a built-in screen and camera and are essentially mobile video-chatting terminals that can be controlled from thousands of miles away.

Soon, Mr. Cousins said, these gadgets will be given more functional bodies, including arms, so they can interact in a physical space.

“Today’s telepresence robots let you be somewhere,” he said. “When you add arms to these things, they will let you act somewhere, too.”

He added, “I think these robots are going to be huge as they let people warp space and time, letting them be somewhere that they’re not, without the cost and time of a flight.”

Robert S. Bauer, an executive director at Willow Garage, pointed out that computers were once seen as exotic machines. In the early 1970s, he said, Xerox Parc developed a series of sophisticated computers that cost several hundred thousand dollars. But these innovative machines paved the way for today’s personal computers.

“Now, 40 years later, everyone has a PC and smartphone in their home and office,” Dr. Bauer said. “The same is happening now with robots.”

He predicted that the first wave of robots would most likely become “the body for people with physical disabilities.” Wounded warriors, quadriplegics and people with Lou Gehrig’s disease, a degenerative nerve disability, will be able to interact with the physical world by controlling a robot, he said.

At the dinner, the group discussed other possible applications for robots in the near future. Some examples included robots that prepared food; swarms of fly-size robots that could patrol a home or office like guards; robots that cleaned the house, did laundry and took out the trash; and robots that could drive cars, maybe even doing a better job than humans do.

Still, robots cannot solve every problem. I asked Mr. Cousins if there would be a robot that could walk my dog, Pixel.

“We actually did that with one of the PR2 robots,” he replied. “The robot was fine with it, but the dog didn’t seem to like it too much and came back with its tail between its legs.”

E-mail: bilton@nytimes.com or Twitter.