TWO-DIMENSIONAL TURBULENT FLOWS LEAK SIGNIFICANT ENERGY to their surroundings, new experiments have confirmed, providing insights that may improve models for the atmosphere and other fluids that move predominantly in two dimensions. As noted fluid dynamicist--and former Einstein postdoc--Robert Kraichnan pointed out in the 1960s, 2-D turbulent flows are remarkably analogous to Bose-Einstein condensates. That's because the vortices in these flat fluids can organize themselves and act in a coherent manner. Perhaps the clearest manifestation of this coherence is the "inverse cascade" effect: small vortices coalesce into larger and larger vortices. This effect partly contributes to the formation of large-scale circulation patterns in the atmosphere, which can be considered a 2-D fluid. The inverse-cascade process would continue unchecked, until a single vortex enveloped the entire fluid, if not for the fact that the fluid dissipates a lot of its energy. But researchers were unsure if this energy primarily went to the fluid's internal viscosity (resistance to flow), or to its surroundings, such as air molecules which exert an external friction. In a new experiment, University of Pittsburgh researchers (X.L. Wu, University of Pittsburgh, 412-624-0873, xlwu+@pitt.edu) create turbulence in a salt-based soap film, by sending electric and magnetic fields through it. (See movies at www.aip.org/png.) By adding a dash of lycopodium (mushroom spores) to the film, they could monitor the turbulence by tracking the lycopodium particles. They found that the energy leakage to the air molecules was at least equal to and in many cases greater than the energy dissipated to internal viscosity. These experiments will give researchers a better idea of the "energy budget" in 2-D turbulent flows. They also underline the fact that there are no ideal 2-D systems in our observable world--they often interact significantly with objects in the third spatial dimension. Such an interaction is essential for maintaining a steady state in the system. (Rivera and Wu, Physical Review Letters, 31 July /pnu/2000/; movie at Phys. News Graphics.)