The interplay between distinct systems, such as bird flocks and atomic particles, may appear as a dichotomy, but recent research emphasizes that the principles governing their collective behavior might not be as disparate as previously thought. A groundbreaking study conducted by an international team, featuring researchers from the Massachusetts Institute of Technology (MIT) and the National Center for Scientific Research (CNRS) in France, reveals striking correlations in the dynamics of living organisms and basic physical particles. The findings problematize longstanding beliefs within the fields of biology and physics, providing a fresh perspective on collective movement.
At its core, the study suggests that the transition from disordered to orderly movement is governed by principles strikingly similar to those observed in atomic systems. Authors of the study, including MIT Biophysicist Julien Tailleur, argue that while human crowds, bird flocks, and various biological entities, such as cells, operate under visually different contexts, they exhibit remarkable parallels in their behaviors. This insight stems from simulating conditions that prompt significant shifts in movement dynamics among “self-propelled agents,” a term encompassing biological entities.
Tailleur’s assertion that “birds are flying atoms” may initially seem unconventional. However, when delving into the core mechanisms of collective motion, this analogy reveals a deep-seated truth: at a fundamental level, collective movement—whether it’s the flapping wings of birds or the spinning of atoms—obeys similar rules.
Traditionally, scientists maintained a strict delineation between the collective behaviors of particles and those of living organisms. The crucial variable in this distinction was identified as ‘distance’, with particles assumed to exert influence primarily through their proximity. In contrast, biological entities depend less on absolute distances and more on visibility. For example, a pigeon operates based not on the closeness of other pigeons but by assessing which fellow birds are within its line of sight.
This shift towards recognizing ‘topological relationships’—where the spatial arrangement and visibility among entities supersede mere physical distance—has profound implications. Despite beliefs that this fundamentally alters the collective motion landscape, Tailleur and his team’s research posits that such differences do not significantly affect the transition from disordered flow to organized movement.
By employing the advice attributed to Einstein—that one should simplify a phenomenon while stripping away unessential complexities—the researchers crafted a model focused on the relevant aspects impacting collective behavior. This model emphasizes that, while biological and physical agents display variances in how they collect information and influence each other, the governing patterns for movement remain consistent across both realms.
Intriguingly, the model developed by the researchers draws inspiration from ferromagnetic materials, known for their unique magnetic properties. In environments with high temperature or low density, the atomic spins within such materials point in random directions, resulting in disorder. However, as conditions shift towards lower temperatures and higher densities, interactions amongst the spins prompt them to align, creating a noticeable order—similar to how flocks of birds move cohesively.
Tailleur references the work of his colleague Hugues Chaté, who discovered twenty years ago that spins moving in the direction of their orientation lead to a discontinuous phase transition, resulting in sudden large-scale coordinated movement. This observation parallels biological systems, where entities, whether they are birds or cells, experience similar abrupt transitions from chaos to order.
The study’s findings carry significant implications for both the fields of physics and biology. By demonstrating that models inspired by particle behavior can successfully elucidate biological collective movements, the research encourages further exploration into interdisciplinary interactions. As academic disciplines grow increasingly integrated, understanding the connections across such diverse systems could lead to novel applications in areas ranging from robotics to ecology.
While the distinctions between particles and biological entities are clear in certain contexts, the essence of collective movement appears tethered by design. Insights from this innovative research challenge long-held perceptions, suggesting collective behaviors may be unified by underlying physical principles. As we continue to unveil the complexities of collective motion in various contexts, the collaboration of science and an open-minded exploration of similarities may illuminate a path towards deeper understanding.