A team of scientists from the Georgia Institute of Technology say they have built a robot that can move without being pushed by anything — a discovery that appears to violate the law of conservation of momentum.
The researchers were able to generate momentum without a surface by building a robot that was isolated from external influences and confined within a curved space. In a video, the machine can be seen moving a pair of motors attached to a curved track, slowly moving on its own without any external force.
“Our study shows that it’s possible to get a certain speed, so it’s possible to go forward without any momentum,” lead researcher Zeb Rocklin, assistant professor of physics at Georgia Tech, told Reuters register.
“It’s important to note, though, that this is only possible in curved spacetime. We provide the curvature by attaching the robot to the sphere.”
Curved space is a fundamental building block of modern physics and crucial to understanding general relativity. For humans moving in three relatively flat dimensions, Newton’s third law states that every force has an equal and opposite force. That’s how rockets gain their trust, how we can jump, and how cars go on the road.
In curved space, the forces are different; objects in curved space should theoretically be able to move without friction or gravity, the team said in their paper.
To minimize the impact of plane space physics on the robot, the team mounted it on a shaft supported by air bearings and bushings. The axis is also aligned with Earth’s gravity to eliminate residual forces.
The robot does face slight friction and gravity, which mixed with its orbital curvature “creates a strange dynamic whose properties cannot be induced on its own,” Georgia Tech said. According to the agency, the stress on the robot during the test was mainly due to its curved environment.
What do you do with a curved space robot?
Watching a video of the robot in action may be a little impressive, but even moving an inch, it’s still doing something important, the researchers said.
As an example, Rocklin said the research his team has done involves studies of “impossible engines” such as the experimental EmDrive.
EmDrive, first proposed in 2006, uses microwaves in a vacuum chamber to theoretically generate thrust by bouncing off surfaces. Tests at TU Dresden found that the thrust reported in the original EmDrive experiment was due to the test cell’s interaction with Earth’s gravitational field, and did not show that the device actually worked.
Rocklin told register EmDrive would “wreak havoc with physics” because it couldn’t get power, and his curved space robot overcomes that.
The curved space could theoretically allow the EmDrive to move, Rocklin said, but was too small to be detected experimentally. “To see motion through this effect, you need a larger curvature, such as that near a black hole,” Rocklin told us.
To explain the similarity, the researchers point to the GPS system, which relies on a slight gravity-induced frequency shift to report position to satellites. “While the effect is small, understanding this curvature-induced effect may have practical implications as robotics becomes more precise,” Georgia Tech said.
Rocklin’s shuffling robot may not move very far, but the “spacetime” bending bits it operates aren’t quite as curved. Just like looking at sea level, it is very difficult to observe the curvature of the earth up close.
Apply these principles to black holes, and space is theoretically more curved than anywhere else in the known universe, and the system could become practical.
“Ultimately, principles of how to exploit the curvature of space for motion may allow spacecraft to navigate the highly curved space around black holes,” Georgia Tech said. The nearest suspected black hole is more than 3,000 light-years away, and it will be a while before we test it. ®