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At first Curtis wasn't keen on publishing his comments, but he indicated he would be willing if both he and Shapley delved more deeply on the technical issues. Shapley agreed. They were originally asked to keep to ten pages, which Curtis joked would force him to follow the laws of writing “generally observed in composing telegrams.” Perhaps, he wrote Shapley, they could “shoot our arrows into the air, to let them fall we know not where.” With his customary down-home wit, Shapley suggested that he would provide “ten pages of buncombe and flapdoodle,” while Curtis could supply “ten more pages of wisdom.”

Shapley also wondered if they should exchange their papers, providing the opportunity to rebut each other's arguments. “Should I go ahead, shoot my shot (or wad), then you use your shillelah (or hammer), then I sneak up behind you and apply my ole horn-handle.” Curtis was game, and over the ensuing months a lively train of drafts and comments went back and forth between them. In the process Curtis pushed Shapley to devote more space to the spiral nebulae, “at least a brief statement of how you explain them if not island universes.” Upon completion, their published remarks each expanded from ten pages to twenty-four, and though it wasn't mentioned until his penultimate paragraphs, Shapley's strongest and freshest ammunition against Curtis involved the spirals. It was there at the end that he played his definitive trump card: The spiral nebulae could not possibly be island universes, because the rotations measured by Adriaan van Maanen at Mount Wilson “appear fatal to such an interpretation.” Shapley now seemed more at ease in dismissing the spirals as simply minor objects. “I see no reason for thinking them stellar or universes,” he told Russell during the course of his writing the Bulletin article. “What monstrous assumptions that requires before you get done with it.” From that point on, Shapley's strongest weapon against supporters of distant galaxies was van Maanen's twirling spirals.

Although in his heart of hearts he never believed it would happen, even Curtis had to grudgingly concede in his published response that if van Maanen's findings held up “the island universe theory must be definitely abandoned.” Over the succeeding years, van Maanen and his observations stood like a giant wall before island-universe advocates. If the spiral nebulae were truly remote and massive galaxies, how could you possibly explain seeing them rotate over just a few years from so far away? The island-universe theory would not gain general acceptance until its supporters figured out how to breach this formidable rampart.

Van Maanen had begun his measurements of the spiral nebulae in 1915 and continued into the early 1920s. Astronomers took his results seriously because his reputation was exemplary. He was known to be a careful observer who followed intricate astronomical procedures to the letter. And it was easy to accept his conclusions, as they supported an idea of the universe that many readily believed at the time: The Milky Way defined the universe, and the spirals were mere appendages that from their swirling appearance had to be turning. Stars, planets, and moons rotated; planets revolved around the Sun; rotation was a natural feature of the universe. Given that, it was not surprising to hear that the spirals were rotating. In 1914 Slipher had already reported on a spiral rotation from his spectroscopic data, but simply viewing the curving lines of a spiral's misty arms, captured so vividly in photographs, made it impossible to think otherwise.

Adriaan van Maanen (left) with Bertil Lindblad (Photograph by Dorothy

Davis Locanthi, courtesy of AIP Emilio Segrè Visual Archives)

Van Maanen was the descendant of an aristocratic family in the Netherlands, whose ancestors were ministers, teachers, and noted jurists. Those who knew him attested to his meticulous integrity and high sense of personal honor, instilled by his family's esteemed heritage. After