A curved-space robot defies established physics rules, offering up new avenues.
When humans, animals, and machines move around the world, they are continuously pushing up against something, whether it is the ground, the air, or the sea. Until recently, physicists assumed this was a constant owing to the momentum conservation law. Georgia Institute of Technology researchers have now shown the inverse: when bodies exist in curved spaces, they can travel without colliding with anything.
The Georgia Tech study’s findings were published in the Proceedings of the National Academy of Sciences (PNAS). According to the researchers, their findings contravene Newtonian dynamics’ premise that “a stationary object cannot move without exchanging momentum with its surroundings.”
This robot was confined to a spherical surface in a highly isolated system, and the major influences it sensed were not from its surroundings, but from the curvature of the space itself. The robot gyrates and jiggles, changing shape. However, in a regular, flat space, these factors would not cause it to travel in any specific direction.
Constructing a Curved Path
The scientists set out to explore how an object moved across a curved zone. They allow a sequence of motors to drive on curved rails as moving masses to restrict the object on the sphere with little interaction or momentum exchange with the environment in the curved zone. The system was then mounted to a rotating shaft in such a way that the motors always traveled on a sphere. To decrease friction, the shaft was supported by air bearings and bushings, and its alignment with the Earth’s gravity was adjusted to lessen residual gravity force.
As the robot went ahead, gravity and friction produced modest strains. These forces interacted with the curvature effects to form a unique dynamic with characteristics that neither could achieve alone. The work is notable because it illustrates how to produce curved rooms without fundamentally contradicting physical assumptions and intuition developed for flat space. Rocklin anticipates that the experimental tools he developed will allow other researchers to examine these curved locations.
Space and beyond applications
While the impacts are minor, as robotics gets more precise, knowing this curvature-induced effect may become important, much as understanding the modest frequency shift caused by gravity proved critical in allowing GPS systems to properly transmit their locations to orbiting satellites. Finally, understanding how to harness a space’s curvature for locomotion may enable spacecraft to navigate the highly curved region around a black hole.
“This research is also related to the ‘Impossible Engine’ investigation,” Rocklin explained. “Its designer claimed that it could travel without using any propellant. Because spacetime is very slightly bent, a gadget might move forward without any external forces or producing a propellant—a unique finding.”
A curved-space robot defies known physical laws, ushering in new locomotive technology possibilities
A Georgia Institute of Technology (Georgia Tech) robot has done the unthinkable by breaking a firm law of motion, implying that new laws must be developed. Such novel ideas may find use in novel kinds of mobility that do not require propellants. We’ve all seen the funny slapstick prank in which an unsuspecting person stumbles on a banana peel and lands humorously on their rear. Although it may not appear so, the joke is founded on the fact that human movement, like all locomotion, is governed by Newton’s third law of motion.
The same is true for all forms of movement. Rockets, for example, use high-speed ejection of large volumes of materials to propel themselves in the opposite direction. Sea and air animals push against the water and atmosphere, respectively. There is always a strong desire to move. However, the Georgia Tech robot has avoided the requirement for propulsion to shift momentum. It does this by using curved space.
“We let our shape-changing item travel over the simplest curved space, a sphere, to explore motion in curved space systematically,” explains lead researcher Zeb Rocklin, an assistant professor in Georgia Tech’s School of Physics. “We discovered that the expected effect, which some physicists disregarded, did occur: as the robot changed shape, it inched ahead around the sphere in a way that could not be explained to ambient interactions.”
To ensure that the effects caused by the curvature of the robot’s space predominate, the physicists had to isolate the system from external influences as much as possible. Only then could the crew guarantee little interaction or momentum exchange with the surroundings. The curved environment was created by driving a series of motors on curved tracks. The rails were subsequently connected to a spinning shaft, creating a circular environment. Air bearings and bushings were used to reduce friction – low heat and low mess alternatives to ball bearings. By matching the rotating shaft with Earth’s gravity, gravity was reduced.
The robot felt relatively minor forces from friction and gravity, but the two effects were found to combine with the curvature of the space itself to form a peculiar dynamic with qualities that neither friction nor gravity could produce on their own. As a result, the team illustrated not only how curved space may be realized, but also how it fundamentally undermines core conceptions associated with flat space rules.
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