The scaling laws found in our study allow a-priori predictions of the dynamical importance of Coriolis forces for a given system. Application to the Earth’s core for example suggests that it is controlled by rotation, but much closer to the transition point than previously expected. Future studies, incorporating additional dynamical effects such as fluid compressibility, low Prandtl number, magnetic fields and more complicated geometries are necessary to account for the individual characteristics of specific natural systems.