Exotic states of matter known as time crystals are thought to be primarily a quantum phenomenon. now, team from New York University (NYU) showed the classic time crystal It can appear in a much simpler way. speaker And Styrofoam.

This system is not only a very clean example of a classical time crystal, but also Very neat laboratory to study non-interaction At the macroscopic scale, particles interact through scattered sound waves rather than direct balanced forces.

“Time crystals are fascinating not only because of their potential, but also because they look so exotic and complex.” says David Greer, a physicist at New York University..

“Our system is great because it’s incredibly simple.”

crystal of time, first predicted in 2012even stranger than its name suggests. This term does not describe an object, but rather a type of behavior, and is concerned with how patterns repeat.

In crystals such as quartz, diamond, salt, and all other metals, the atoms are arranged in an ordered lattice structure that repeats in three-dimensional space, like the joints between the bars of a jungle gym. Any part of the pattern can completely overlap any other part of the pattern.

a time crystal It is an arrangement of particles that repeats over time and, like a spatial crystal, oscillates in a repeating temporal pattern in a way that can even be superimposed. Importantly, this continuous oscillation breaks time symmetry and operates at a frequency that emerges from the interaction itself, without being set by an external ticking clock or periodic drive.

Many experimental time crystals are quantum systems based on entangled states. Greer and his colleagues, New York University physicists Mia Morell and Leela Elliott, discovered the classical system almost by accident while investigating different types of physical interactions.

small polystyrene Beads, just 1 to 2 millimeters in diameter, are excellent tools for studying how objects interact indirectly through sound waves. It’s very light, so Float using sound wavesHowever, it has sufficient structural integrity to remain rigid under acoustic forces. There are also slight differences in size and shape, which is very important when studying nonreciprocal interactions.

Scientists conducted the experiment as part of ongoing research into these interactions. First, a small speaker array was tuned to generate standing sound waves. perfectly balanced Structurally, there is no forced rhythm. Next, a bead was introduced, creating a small obstacle that bounced the sound waves off.

“Sound waves exert a force on particles, just as waves on the surface of a pond exert a force on floating leaves.” Morel says.

“By immersing an object in a sound field called a standing wave, it is possible to suspend the object against gravity.”

The two beads interact through waves that each scatter. A slightly larger bead will cause more disturbance than a smaller bead. Therefore, the force exerted on a small bead is greater than the force exerted by a small bead on a large bead.

This is what non-interaction means. Although common in acoustics and optics, they are usually small and difficult to isolate experimentally.

The researchers investigated this phenomenon using a device and found that, under the right conditions, the interaction between two beads causes them to vibrate in a temporal pattern without anyone shaking, prodding, or introducing a beat.

Related: World’s first: physicists create a quantum time crystal that they can actually see

The beads can maintain a stable repeating pattern for hours, settling into a robust steady state rather than temporary fluctuations. And only two beads? it is the smallest possible system behave subconsciously As a crystal of time.

Although it may not yet have practical applications, this discovery could spark other experimental pursuits. For example, some biochemical systems in our bodies are engage in non-reciprocal interactions. This does not mean that our circadian rhythms are time crystals, but it does raise interesting questions about whether similar principles might emerge in biology.

It also shows that you don’t necessarily need expensive high-tech equipment to investigate some of the more exotic behaviors of the physical world. In some cases, it seems like you can make do with Styrofoam and perhaps a subwoofer.

The survey results are physical review letter.