NYU Physicists Observe Macroscopic Time Crystal Driven by Nonreciprocal Acoustic Forces

A team of physicists at New York University (NYU) has experimentally realized a novel time crystal existing at the macroscopic scale, a significant development detailed in the journal Physical Review Letters on February 6, 2026. This exotic phase of matter utilizes millimeter-sized polystyrene beads suspended in air by an acoustic levitator, a system the researchers characterized by its fundamental simplicity.

The central finding concerns the mechanism of interaction: levitated particles exchange forces mediated by scattered sound waves, a process that inherently breaks the reciprocity required by classical mechanics. The experimental setup, which is small enough to be held in one hand and stands under thirty centimeters tall, uses standing sound waves to counteract gravity on the styrofoam particles. When these suspended beads interact, the force exchange is asymmetric; a larger bead scatters more acoustic energy, exerting a greater force on a smaller bead than the reciprocal force it receives.

This inherent asymmetry, which violates Isaac Newton's Third Law of Motion, is the critical element permitting the system to sustain a persistent, self-regulating rhythmic oscillation—the defining feature of a time crystal. The research, led by Professor David Grier, Director of NYU's Center for Soft Matter Research, involved graduate student Mia Morrell and undergraduate Leela Elliott. The patterned oscillation of the beads demonstrated notable stability, maintaining coherence for several hours within the acoustic trap.

This achievement establishes a classical, macroscopic time crystal whose operational principle relies on the violation of Newtonian reciprocity. The work moves the study of time crystals beyond typically complex quantum environments, offering an accessible model system for investigating non-reciprocal phenomena across various scientific fields, including biological dynamics such as circadian rhythms and metabolic processes.