Georgia Tech researchers demonstrated that a robot can move without applying force on something. (Image Credit: Georgia Tech)
Humans, animals, and machines tend to push against the water, ground, or air to achieve movement. Physicists thought this was the result of following the law of conservation momentum. Georgia Institute of Technology researchers demonstrated that objects present in curved spaces move without pushing against anything. Georgia Tech's School of Physics assistant professor Zeb Becklin developed a robot set inside a spherical surface, isolated from its environment, allowing the curvature-induced effects to predominate.
"We let our shape-changing object move on the simplest curved space, a sphere, to systematically study the motion in curved space," said Rocklin. "We learned that the predicted effect, which was so counter-intuitive it was dismissed by some physicists, indeed occurred: as the robot changed its shape, it inched forward around the sphere in a way that could not be attributed to environmental interactions."
The team started by determining how an object moved within a curved space. In this case, they deployed a set of motors that operated like moving masses on curved tracks, allowing the object to stay confined on the sphere with minimal contact in the curved space environment. Connecting a rotating shaft to the system ensured that the motors could consistently move on a sphere. Air bearings and bushings support the shaft, resulting in minimized friction. The team also relied on the Earth's gravity to adjust the shaft's alignment, minimizing the gravity's residual force.
Gravity and friction then applied small forces on the robot as it moved. This generated a unique dynamic with properties the forces or curvature effects could not otherwise induce. This work shows how curved spaces "challenges physical laws and intuition designed for flat space." Other research teams could also utilize this experimental approach to study these curved spaces.
While a robot's precision increases, understanding the curvature effect may be crucial. It's similar to the frequency shift that allows GPS systems to precisely transmit their positions to orbital satellites. Harnessing a space's curvature for locomotion could lead to spacecraft navigating the curved space around a black hole.
"This research also relates to the 'Impossible Engine' study," said Rocklin. "Its creator claimed that it could move forward without any propellant. That engine was indeed impossible, but because spacetime is very slightly curved, a device could actually move forward without any external forces or emitting a propellant—a novel discovery."
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