Rubuta ci gaba ga wannan sakin layi - A cikin 1920 an yi muhawara tsakanin Harlow Shapley da Heber Curtis (Babban Muhawara
), game da yanayin Milky Way, nebulae mai juyawa, da girman sararin samaniya. Don tallafawa da'awarsa cewa Babban Andromeda Nebula wani galaxy ne na waje, Curtis ya lura da bayyanar layuka masu duhu waɗanda suke kama da gajimare na ƙura a cikin Milky Way, da kuma mahimmancin Doppler.