It was one more defeat in our long and losing battle to keep the Sun perfect, or, if not perfect, constant, and if inconstant, regular. Why we think the Sun should be any of these when other stars are not is more a question for social than for physical science. John A. ("Jack") Eddy Delineator of the Maunder Minimum On the human Idée fi xe as to why the Sun must be seen energetically as a linear entity. Around 1904, Kapteyn noticed that the stars did not move randomly through space, but that their movements had preferential directions... there was regularity in something astronomers had always thought to be chaotic. Adriaan Blaauw, emeritus director of the Kapteyn Institute, Groningen, Netherlands On Jacob Cornelius Kapteyn's discovery of star streaming: the concept of galactic rotation and so, proof of some regularity in stellar behavior.