For more than three centuries, Newton’s Third Law has stood as one of the most intuitive and reliable principles in all of physics: for every action, there is an equal and opposite reaction. Push against a wall, and the wall pushes back. Fire a rifle, and the recoil kicks your shoulder. It is a law so fundamental that generations of engineers, scientists, and students have built entire careers on its certainty. Now, a team of physicists has demonstrated something that appears to violate this bedrock principle — and they did it using one of the strangest phases of matter ever conceived: time crystals.
A study published in the journal Nature Physics by researchers at Aalto University in Finland has shown that two coupled time crystals can exchange magnons — quasiparticles of magnetic energy — in a way that is decidedly non-reciprocal. In plain terms, when one time crystal pushes the other, the second one does not push back equally. The finding, as reported by MSN, represents a striking departure from classical mechanics and could open new frontiers in quantum computing, ultra-precise sensing, and the fundamental understanding of non-equilibrium physics.
What Exactly Is a Time Crystal, and Why Should Anyone Care?
The concept of a time crystal was first proposed in 2012 by Nobel laureate Frank Wilczek. Ordinary crystals — diamonds, salt, quartz — have atoms arranged in a repeating pattern across space. A time crystal, by analogy, has a structure that repeats not in space but in time. Its constituent particles oscillate in a periodic pattern, returning to their original state at regular intervals, without absorbing or expending energy. This makes them a new phase of matter, one that exists in a perpetual state of motion in its lowest-energy configuration, seemingly defying the expectation that systems at minimum energy should be static.
Time crystals were first experimentally realized in 2017, and since then physicists have been probing their properties with increasing sophistication. The Aalto University team, led by Professor Samuli Autti, created their time crystals inside a sample of helium-3 — a rare isotope of helium — cooled to within a fraction of a degree above absolute zero. At these temperatures, helium-3 enters a superfluid state, and collections of magnons within the superfluid can be coaxed into forming time crystals. These are not abstract mathematical constructs; they are physical, measurable objects that oscillate with clockwork regularity.
The Experiment That Upended a 300-Year-Old Law
The Finnish team’s experiment involved coupling two of these magnon time crystals together and observing how they interacted. In a system governed by Newton’s Third Law, any force exerted by time crystal A on time crystal B should be met with an equal and opposite force from B back on A. But that is not what the researchers found. Instead, the interaction was asymmetric — one time crystal influenced the other more strongly than it was influenced in return. The magnon populations transferred between the two crystals in a lopsided fashion, breaking the reciprocity that Newtonian mechanics demands.
According to the research team, this non-reciprocal behavior arises because the time crystals are inherently non-equilibrium systems. Newton’s Third Law, while extraordinarily reliable in everyday and even most quantum scenarios, assumes a kind of equilibrium symmetry in interactions. Time crystals, by their very nature, exist outside of thermal equilibrium — they are perpetually oscillating, perpetually dynamic. This non-equilibrium character, the researchers argue, is what permits the violation. As Professor Autti explained in statements accompanying the research, the result shows that “Newton’s third law can be broken” in systems that are fundamentally out of equilibrium, a finding with potentially far-reaching implications.
Non-Reciprocity: A Concept With Enormous Practical Potential
Non-reciprocal interactions are not entirely unknown in physics, but they are rare and typically require very specific engineered conditions. Optical isolators, for example, allow light to pass in one direction but not the other, and they are essential components in laser systems and fiber-optic communications. But achieving non-reciprocity at the quantum level, in a system of interacting matter rather than photons, is a substantially different and more difficult proposition. The Aalto University result demonstrates that nature itself can produce such asymmetry under the right conditions, without the need for elaborate engineering.
The practical applications of controllable non-reciprocal quantum interactions could be significant. In quantum computing, where information must flow in precisely controlled directions and where unwanted backflow of quantum states can destroy coherence and introduce errors, a naturally non-reciprocal coupling mechanism could prove invaluable. Similarly, in quantum sensing — where the goal is to detect extraordinarily faint signals without disturbing them — non-reciprocal elements could allow sensors to receive information from their environment without radiating energy back into it, dramatically improving sensitivity.
Placing the Discovery in the Broader Physics Landscape
The discovery arrives at a moment when the physics community is increasingly focused on non-equilibrium quantum systems. For decades, the overwhelming majority of quantum physics research dealt with systems at or near equilibrium — superconductors, superfluids, Bose-Einstein condensates in their ground states. But a growing body of work, including research into many-body localization, Floquet systems, and now time crystals, is pushing into territory where the familiar rules may not apply. The Aalto University finding adds a dramatic data point to this emerging field, suggesting that non-equilibrium quantum matter may harbor behaviors that have no analog in classical or equilibrium quantum physics.
It is also worth placing this result in the context of ongoing debates about what time crystals actually are and what they can do. Since Wilczek’s original proposal, there has been considerable discussion — and some controversy — about whether time crystals truly represent a distinct phase of matter or are simply a clever relabeling of already-understood phenomena. The 2017 experimental realizations, carried out independently by teams at the University of Maryland and Harvard University, went a long way toward settling that debate in favor of time crystals’ legitimacy. The new Finnish result goes further, demonstrating that time crystals are not merely exotic curiosities but systems capable of producing genuinely novel physics — physics that challenges principles as old and venerable as Newton’s Third Law.
What Newton’s Third Law Actually Says — and What It Doesn’t
It is important to be precise about what is and is not being claimed here. Newton’s Third Law is not “wrong” in any general sense. It remains an extraordinarily accurate description of how forces work in the vast majority of physical situations, from planetary orbits to automobile collisions to the biochemistry of muscle contraction. What the Aalto University experiment shows is that the law has a domain of applicability, and that domain does not extend to all non-equilibrium quantum systems. This is not unprecedented in the history of physics — Newton’s laws of motion themselves were shown to be approximations of deeper relativistic and quantum mechanical truths by Einstein and the founders of quantum theory in the early 20th century. Each such discovery did not invalidate Newton so much as reveal the boundaries of his framework.
The researchers have been careful to frame their findings accordingly. They are not claiming to have overturned classical mechanics. Rather, they have identified a specific and reproducible physical regime in which one of its foundational principles does not hold. That distinction matters enormously, both scientifically and in terms of public understanding. The temptation to declare that “Newton was wrong” makes for dramatic headlines but poor science communication. What the Finnish team has done is more subtle and, in many ways, more interesting: they have mapped a new boundary of known physics.
The Road Ahead for Time Crystal Research
The immediate next steps for the Aalto University group and others in the field involve characterizing the non-reciprocal interaction more precisely — understanding exactly how the asymmetry scales with the size of the time crystals, the strength of their coupling, and the degree to which they are driven out of equilibrium. There is also the question of whether similar non-reciprocal behavior can be observed in other types of time crystals, such as those created in arrays of trapped ions or in nitrogen-vacancy centers in diamond, which operate at much higher temperatures than superfluid helium-3.
If non-reciprocity turns out to be a generic feature of coupled time crystals rather than a peculiarity of the helium-3 system, the implications for quantum technology could be substantial. Researchers are already exploring whether time crystals could serve as components in quantum networks, where directional information flow is a persistent engineering challenge. The ability to create quantum elements that inherently favor one direction of interaction over another — without external magnetic fields or complex photonic structures — would represent a significant advance.
A Quiet Revolution in How We Understand Matter
For now, the discovery stands as a remarkable demonstration of how much remains unknown about the behavior of matter at its most fundamental level. Three centuries after Newton codified the laws of motion, physicists are still finding regimes where those laws bend or break. Time crystals, once dismissed by some as a theoretical novelty, are proving to be a rich source of surprises. The Aalto University experiment, published in Nature Physics and covered widely in science media, may well be remembered as the moment when these exotic objects moved from the margins of physics to its center — not because they disproved Newton, but because they showed that the universe still has rules we have not yet learned.
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