Rubuta ci gaba ga wannan sakin layi - A 1920 an nada shi darektan Allegheny Observatory. A wannan shekarar ya shiga cikin Babban Muhawarar
tare da Harlow Shapley (wanda ake kira Shapley <unk> Curtis Debate) a kan yanayin nebulae da galaxies, da girman duniya. Curtis ya goyi bayan ra'ayin da aka yarda da shi yanzu cewa akwai wasu taurari banda Milky Way.