Discuss the “Great Debate†that took place between HarlowShapley and Heber Curtis in 1920. (a) What werethe major arguments on each side of the question of whether thespiral nebulae were Galactic (in the Milky Way) or extragalactic(outside the Milky Way)? (b) Briefly outline howShapley estimated the size of the Milky Way.
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