When humans, animals, and machines move throughout the world, they always push against something, whether it's the ground, air, or water. Until recently, physicists believed this to be a constant, following the law of conservation momentum. Now, researchers from the Georgia Institute of Technology have proven the opposite—when bodies exist in curved spaces, it turns out that they can in fact move without pushing against something.

The findings were published in Proceedings of the National Academy of Sciences on July 28, 2022. In the paper, a team of researchers led by Zeb Rocklin, assistant professor in the School of Physics at Georgia Tech, created a robot confined to a spherical surface with unprecedented levels of isolation from its environment, so that these curvature-induced effects would 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."