We argue that storage rings can be used for the detection of low–frequency gravitational–wave background. Proceeding from the measurements by Schin Daté and Noritaka Kumagai (Nucl. Instrum. Meth. A421, 417 (1999)) and Masaru Takao and Taihei Shimada (Proceedings of EPAC 2000, Vienna, 2000, p.1572) of variations of the machine circumference of the SPring–8 storage ring we explain the systematic ...