The suggested plan of the galactic system may be concretely formulated through the following series of propositions. … Taken altogether they attempt to establish a general idea of the arrangement, extent, and constituency of the system of stars and nebulae. A. The globular clusters are a part of the galactic system and knowledge of their distances seems at present to afford the best way to fathom the system. B. The system of globular clusters, which is coincident in general, if not in detail, with the sidereal arrangement as a whole, appears to be somewhat ellipsoidal. … C. The center of the sidereal system is distant from the earth …
       —Shapley