New Levitating Time Crystals Challenge Newton's Third Law

Researchers at New York University (NYU) have made a significant advancement in the field of quantum physics by observing a new type of time crystal that can levitate on sound waves. This discovery, detailed in the journal *Physical Review Letters*, suggests that these time crystals may defy Newton's Third Law of Motion, which states that for every action, there is an equal and opposite reaction. The team, led by David Grier, director of NYU's Center for Soft Matter Research, includes graduate student Mia Morrell and undergraduate Leela Elliott.

The Debrief

Time crystals are unique systems that exhibit repetitive oscillations without a continuous external force. The NYU team demonstrated that small Styrofoam beads, when placed in a sound field created by high-frequency sound waves, can levitate and enter a state of rhythmic motion. Morrell explained that sound waves exert forces on particles similarly to how waves on a pond affect floating leaves. This levitation allows the beads to interact in ways that challenge traditional physics.

NYU physicists create visible time crystals levitated by soundThe Debrief

The researchers found that larger beads scatter sound waves more effectively than smaller ones, leading to an imbalance in the forces acting on them. This phenomenon allows the beads to oscillate spontaneously, creating a clock-like ticking motion. The team identified four distinct states of motion in their system, including two emergent active steady states that disrupt space-time symmetry, thereby constituting a classical time crystal.

NYU physicists create visible time crystals levitated by sound

The implications of this research extend beyond theoretical physics. The unique properties of these levitating time crystals could pave the way for advancements in quantum computation, data storage, and the design of new sensors and oscillators. The simplicity of the setup—an acoustic levitator that can be held in one hand—highlights the potential for practical applications in various fields, including biology, where similar nonreciprocal interactions are observed in biochemical networks.

The Debrief

While the findings are groundbreaking, some critics may question the practical applications of time crystals, given that their utility has yet to be fully realized. Additionally, the reliance on specific size combinations and imperfections in the beads raises questions about the reproducibility of these effects in larger systems.

NYU physicists create visible time crystals levitated by sound

• “Time crystals are fascinating not only because of the possibilities, but also because they seem so exotic and complicated,” — David Grier, Director, NYU Center for Soft Matter Research

The Debrief

• “We can levitate objects against gravity by immersing them in a sound field called a standing wave.” — Mia Morrell, NYU Graduate Student

NYU physicists create visible time crystals levitated by sound

• “Each one makes water waves that push the other one around—but to different degrees, depending on their size,” — Mia Morrell, NYU Graduate Student

The Debrief

The NYU team's research opens new avenues for exploring the behavior of time crystals and their potential applications in technology. Future studies may focus on scaling these systems and investigating their interactions in larger groups, which could reveal further insights into the fundamental principles of physics and their applications in real-world scenarios.

NYU physicists create visible time crystals levitated by sound