Researchers developed a new robot that could help us travel around black holes
- The robot recreates the same environment found around black holes.
- It does so by moving in a curved space.
- It could one day allow us to further study black holes.
There is one constant on Earth and that is that when humans, animals, and machines move, they always push against something, whether it’s the ground, air, or water. This fact consists of the law of conservation momentum and was up to now undisputed.
Curved spaces provide new principles
However, new research from the Georgia Institute of Technology has come along to showcase the opposite – when bodies exist in curved spaces, they can move without pushing against something.
The new study was led by Zeb Rocklin, assistant professor in the School of Physics at Georgia Tech, and it saw the engineering of “a robot confined to a spherical surface with unprecedented levels of isolation from its environment, so that these curvature-induced effects would predominate,” according to a statement by the institution published on Monday.
“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 whole purpose of the new research was to evaluate how an object moved within a curved space. To do this, they used a specialized robot.
The machine was built to induce an environment with minimal interaction or exchange of momentum in the curved space by using a set of motors on curved tracks as moving masses. This system was then connected to a rotating shaft so that the motors would always move on a sphere.
This shaft was supported by air bearings and bushings to minimize the friction, and the alignment of the shaft was adjusted with the Earth’s gravity to minimize the residual force of gravity.
The end result was a robot that continued to move while gravity and friction exerted slight forces on it. These forces hybridized with the curvature effects to produce a strange dynamic with properties neither could induce on their own.
Challenging physical laws
The robot’s curved movements are an important demonstration of how curved spaces can be attained and how they fundamentally challenge physical laws.
“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.”
The researchers speculate that such robots could also one day help us travel around black holes by recreating the same environment the celestial objects exist in. Now that would be a cool development!
The findings were published in the Proceedings of the National Academy of Sciences.
Locomotion by shape changes or gas expulsion is assumed to require environmental interaction, due to conservation of momentum. However, as first noted in [J. Wisdom, Science 299, 1865-1869 (2003)] and later in [E. Guéron, Sci. Am. 301, 38-45 (2009)] and [J. Avron, O. Kenneth, New J. Phys, 8, 68 (2006)], the noncommutativity of translations permits translation without momentum exchange in either gravitationally curved spacetime or the curved surfaces encountered by locomotors in real-world environments. To realize this idea which remained unvalidated in experiments for almost 20 y, we show that a precision robophysical apparatus consisting of motors driven on curved tracks (and thereby confined to a spherical surface without a solid substrate) can self-propel without environmental momentum exchange. It produces shape changes comparable to the environment’s inverse curvatures and generates movement of 10−1 cm per gait. While this simple geometric effect predominates over short time, eventually the dissipative (frictional) and conservative forces, ubiquitous in real systems, couple to it to generate an emergent dynamics in which the swimming motion produces a force that is counter-balanced against residual gravitational forces. In this way, the robot both swims forward without momentum and becomes fixed in place with a finite momentum that can be released by ceasing the swimming motion. We envision that our work will be of use in a broad variety of contexts, such as active matter in curved space and robots navigating real-world environments with curved surfaces.
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