Rocking and rolling: how to stop luggage toppling on the race through the airport

Scientists in Paris come up with unexpected answer to the age-old problem of running to the departure gate with a two-wheeled suitcase

Half a century after the American businessman Bernard D Sadow shocked travellers with the invention of "rolling luggage", scientists have worked out why suitcases tend to to rock violently from one wheel to the other until they overturn on the race through the airport.

This most pressing of modern mysteries was taken on by physicists in Paris, who devised a scale model of a two-wheeled suitcase rolling on a treadmill and backed up their observations with a pile of equations and references to holonomic restraints, finite perturbations and the morphing of bifurcation diagrams.