Scientists have found that micron-size particles which are trapped at fluid interfaces exhibit a collective dynamic that is subject to seemingly unrelated governing laws. These laws show a smooth transitioning from long-ranged cosmological-style gravitational attraction down to short-range attractive and repulsive forces. The study by Johannes Bleibel from the Max Planck Institute for Intelligent Systems in Stuttgart, Germany, and his colleagues has just been published in the journal EPJ E. The authors used so-called colloidal particles that are larger than molecules but too small to be observed with the naked eye. These particles are adsorbed at the interface between two fluids and assembled into a monolayer. This constitutes a 2D model in which particles that are larger than a micron deform the interface through their own weight and generate an effective long-range attraction which looks like gravitation in 2D. Thus, the particles assemble in clusters. Read more