The Secret to Sorting 25,000 Jumbled Dice Involves Some Surprisingly Simple Physics

Image: Asencio et al (Phys Rev Let 2017)
Image: Asencio et al (Phys Rev Let 2017)

Physics has a bit of a problem. Stuff that you don’t really think about, like single items moving on frictionless surfaces or two bodies traveling in the void of space, are really easy to explain. Stuff you experience every day, like water dropping or M&Ms spilling on the floor, are incredibly complex.

A team of Spanish and Mexican scientists were therefore interested in a problem I bet you’ve thought of: How to perfectly compact a container full of jumbled dice. In experiments, and through a series of light twists on these “cubic particles,” the dice assumed a perfect alignment inside of a cylinder.

“In this work, we have shown that twisting a sample of cubic particles is a highly efficient way to achieve ordered packings,” the authors write in the paper published recently in Physical Review Letters.


You might remember that things falling to the Earth always accelerate at around 10 meters per second squared—they go ten meters per second faster for every second they’re falling. At accelerations greater than half that, the dice packed after 10,000 twists.

This is due to the presence of the flat surfaces on the dice; when they slide past one another, these surfaces prefer to line up. And unlike previous experiments that have involved a lot of tapping, the twisting action led to eventual ordering regardless of how hard the twisting was (up to a point). Tapping requires much more specific motions and rates to order the dice.

There are uses for experiments like these—mainly industrial ones where companies need to pack a lot of stuff into a container. And one scientist not involved in the study, Matthias Schröter of the Max Planck Institute for Dynamics and Self-Organization in Germany, told Physics that the ordering of the dice came from the presence of the boundary—the container. It’s kind of like a crystal growing, except with dice. “The experiments are solid and quite clean,” he told Physics.

Next up, time to test this experiment in space.

[PRL via Physics]


Former Gizmodo physics writer and founder of Birdmodo, now a science communicator specializing in quantum computing and birds

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