Last year, physicists created a time crystal—atomic arrangements repeating motion patterns—visible to the naked eye. But the latest research on this quantum eccentricity might represent more than a few steps forward.
This time crystal, described in a recent Physical Review Letters paper, is big enough to be held in your hand, and it levitates. Discovered by a team of physicists at New York University (NYU), the new type of time crystal consists of styrofoam-like beads that levitate on a cushion of sound while exchanging sound waves.
If that wasn’t strange enough, the time crystal does this by violating Newtonian physics—and the team believes that gives the new crystal both academic and practical significance.
“This was a discovery in the truest sense,” David G. Grier, the study’s senior author and a physicist at NYU, told Gizmodo. “Perhaps the most remarkable thing is that such rich and interesting behavior emerges from such a simple system.”
What are time crystals?
In 2012, Nobel laureate Frank Wilczek pitched an idea for an impossible crystal breaking the rules of symmetry in physics. Typically, solid crystals maintain a continuous lattice of their respective components. Time crystals, however, do the exact opposite, with the individual atoms inside them changing positions over time in a relatively defined pattern.
In the past decade or so, physicists have managed to find varying versions of Wilczek’s vision. But these instances mostly featured short-term, microscopic time crystals with little practical implications. It was only last year that one team at the University of Colorado Boulder proposed a time crystal design that we can actually see.
Styrofoam finds a new quirk 
The setup of the new time crystal system. A bead (purple) is suspended in mid-air by sound waves emanating from (black) circular speakers arranged in a six-inch-tall 3D-printed frame. Credit: NYU Center for Soft Matter Research
The newly discovered time crystal may represent huge advances in the practical relevance of time crystals. For one, the bead in the experiment is expanded polystyrene—the same material used for packing styrofoam.
The team turned this common material into a time crystal by suspending styrofoam beads in sound waves. By itself, the bead floats motionlessly, but things begin to change once multiple beads levitate together.
In this system, each bead scatters its own share of sound waves. That contributes to an overall system of “unbalanced interactions” that essentially allows the particles to harvest and supply energy from the sound waves, Grier explained. “The key point is that time crystals select their own frequency without being told what to do by any external force.”
The simplest of them all?
What’s more, these interactions aren’t bound to Newton’s third law of motion, which dictates that two bodies exerting force on each other must exert the same amount of force in opposite directions.
“Think of two ferries of different sizes approaching a dock,” Mia Morrell, the study’s lead author and a graduate student at NYU, said in a university statement. “Each one makes water waves that push the other one around—but to different degrees, depending on their size.”
A stop-motion image that shows pairs of millimeter-scale beads forming a time crystal over approximately one-third of a second in time. The colors represent the beads interacting at different stages during this period. Credit: NYU Center for Soft Matter Research
According to Grier, the sheer simplicity of this time crystal setup potentially makes it the “hydrogen atom” for this phenomenon—highlighting its potential across other contexts, such as “the neural pacemakers in our hearts to cyclic trends in financial markets.”
“We’re hoping that studying a minimal model will provide access to the deepest insights into the spontaneous emergence of clocks in more general and more complex manifestations,” he added.