One of the many fascinating aspects of physics is the surprising scaling behaviour between the very small and the very large. Early last century, it became clear that the structure of the solar system and a single atom are both governed by similar attractive interactions. More recently, chaos theory has explained why similar fractal shapes exist in snowflakes, ferns and the shapes of entire mountain ranges.
Now another observation of atomic and planetary systems behaving in surprisingly similar fashion has been reported by Robert Birtcher and Sandrine Schlutig at Argonne National Laboratory, US, and Stephen Donnelly of Salford University, UK (Phys. Rev. Lett. 2000 85 4968). In the March issue of Physics World, Kai Nordlund of the University of Helsinki in Finland describes how the pair used xenon ions to produce huge craters in a gold film – and how their work might shed light on planetary-impact phenomena.
