Symmetry breaking in a chemical pinwheel

A transition that breaks the m‐fold rotational symmetry of a chemical pattern of traveling waves is reported. The chemical waves travel around a thin annular gel, the inner and outer edges of which are in contact with continuous flow chemical reservoirs. Observations of the dependence of the rotating wave pattern as a function of temperature reveal several distinct states, including a wavelength‐doubled state in which successive waves alternate in shape.