It has long been known that there are two types of excitation for electrons, as in addition to their charge they have a property called spin. Spin and charge excitations travel at fixed, but different speeds...However, theorists are unable to calculate what precisely happens beyond only small perturbations, as the interactions are too complex. The Cambridge team has measured these speeds as their energies are varied, and find that a very simple picture emerges...Each type of excitation can have low or high kinetic energy... with the well-known formula E=1/2 mv2, which is a parabola. But for spin and charge the...