A team of Georgia Tech scientists say they’ve built a robot that can move without anything to push against, a discovery that appears to violate the law of conservation of momentum.
The researchers were able to generate momentum without a surface to push off by building a robot isolated from outside influences and confined to a curved space. In a video, the machine can be seen moving a pair of motors attached to a piece of curved track, moving slowly without any external force.
“What our research shows is that it’s possible to acquire some kind of speed, and thus move forward, without acquiring any momentum,” said lead researcher and Georgia Tech assistant professor of physics Zeb Rocklin. The Register.
“The caveat, though, is that this is only possible in curved space-time. We supplied the curvature by attaching our robot to a sphere.”
Curved space is a fundamental part of modern physics and is essential to understanding general relativity. For humans, who move in three relatively flat dimensions, Newton’s third law dictates that for every force there is an equal and opposite force. This is how rockets get their confidence, how we are able to jump and how cars move on the road.
In curved space, the forces differ; In their paper, the team said that objects in curved space should theoretically be able to move without frictional forces or gravitations.
To minimize the influence of plane space physics on the robot, the team mounted it on an axle supported by bearings and air bearings. The axle was also aligned with the earth’s gravity to eliminate residual force.
The robot faced light frictional and gravitational forces, which hybridized with the curvature of its track “to produce strange dynamics with properties that neither could induce on their own,” Georgia Tech said. According to the institution, the forces on the robot during testing were mainly due to its curved environment.
What do you do with a curved space robot?
Watching the video of the robot in action might be a little underwhelming, but even moving fractions of an inch it’s still doing something important, the researchers say.
As an example, Rocklin said the research done by his team relates to studies of “impossible motors,” such as the experimental EmDrive.
First proposed in 2006, the EmDrive uses microwaves in a vacuum chamber to theoretically create thrust by bouncing off a surface. Tests conducted at TU Dresden found that the thrust reported in the initial EmDrive experiments was due to the test unit’s interaction with the Earth’s gravitational field and did not indicate that the device was actually working.
Rocklin said The Register that the EmDrive would “seriously break physics” if it worked, as there would be no way to gain momentum, something his curved space robot overcomes.
The curved space could theoretically make the EmDrive move, Rocklin said, but to a degree too small to be experimentally detectable. “To see motion through this effect you would need a much larger curvature, like that present in the vicinity of a black hole,” Rocklin told us.
To explain the similarity, the researchers pointed to GPS systems, which rely on slight gravity-induced frequency changes to report locations to satellites. “Although the effects are small, as robotics become increasingly precise, understanding this curvature-induced effect may be of practical importance,” said Georgia Tech.
Rocklin’s scrambling robot may not move much, but the curved piece of “space-time” it operates in isn’t so curved. Like looking at the ocean horizon, it is quite difficult to see the curvature of the Earth when viewed up close.
Apply these principles to black holes, where space theoretically curves more than anywhere else in the known cosmos, and the system could become practical.
“Ultimately, the principles of how the curvature of space can be harnessed for locomotion may allow spacecraft to navigate the highly curved space around a black hole,” Georgia Tech said. With the nearest black hole suspect located more than 3,000 light-years from Earth, it will be a while before we can test it. ®
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