Low-cost experiment exhibits analogies with black hole collisions

What does a spinning penny have in common with black holes? That was the question on the minds of Meringolo et al. when challenged to set up a low-cost experiment to an open physics question.

Meringolo thought the penny could generate vibrations similar to the reverberations in space-time caused by a black hole merger. The group substituted the penny with a larger aluminum disk to set up an experiment to measure the disk’s vibrations with a smartphone’s accelerometer as it sat spinning on a tabletop. The vibrations were then compared to gravitational wave signatures from two black holes spiraling inward and colliding.

“We have been excited by the fact that two phenomena occurring at such disparate scales exhibit similar behavior and signaling,” said author Domenico Davide Meringolo. “Furthermore, it is exciting that the experiments with the disk can be performed with a low-cost setup.”

Notably, the amplitude and frequency of the vibrations from the spinning disk and the black holes both increased to a singularity. This singularity for the disk was when it finally came to a rest flat on the table, and for the black holes, the singularity was their merger.

“We hope that teachers propose this project to students to help them develop analogy-based reasoning and think outside the box of usual textbooks,” said author Giuseppe Pucci. “We also hope that this work could help spread the good practice of proposing open questions that trigger class projects in which the students can develop their curiosity and creativity and be protagonists of their work.”

Source: “On the analogy between spinning disks coming to rest and merging black holes,” by Domenico Davide Meringolo, Francesco Conidi, Alessandra Mercuri, Massimino Sposato, Riccardo Cristoforo Barberi and Giuseppe Pucci, American Journal of Physics (2025). The article can be accessed at https://doi.org/10.1119/5.0208307 .