<prompt> Bhala okuqhubekayo kwalesi sigaba - Ngokuhambisana nalendlela eshintshashintshayo yokuhlola indawo yonke, impikiswano endala ngesakhiwo sendawo yonke yayifinyelela umvuthwandaba. Isazi sezinkanyezi saseMount Wilson uHarlow Shapley wasekela imodeli yendawo yonke eyakhiwe ngohlelo lwezinkanyezi lweMilky Way kuphela; kuyilapho uHeber D. Curtis ephikisana nomqondo wokuthi ama-spiral nebula ayeyizinhlelo zezinkanyezi ngokwazo njengeziqhingi zomhlaba. Lokhu kwehluka kwemibono kwafinyelela umvuthwandaba ngokuhlelwa kwe-Great Debate  <response>: ngo-Ephreli 26, 1920 emhlanganweni we-U.S. National Academy of Sciences eWashington, D.C. Impikiswano yaxazululwa lapho u-Edwin Hubble ethola i-Cephid Variables e-Andromeda Galaxy ngo-1923 nango-1924. Ibanga lazo lakha ama-nebula e-spiral ngale komngcele we-Milky Way. 