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By Root 578 0

there Curtis went on to focus on the spiral nebulae, the subject that Shapley conveniently avoided. Curtis showcased his best evidence, echoing many of the points he had made to the Washington Academy of Sciences just the year before: He stressed that the spiral nebulae displayed the spectra typical for collections of stars—not gas; that not one spiral had ever been found within the Milky Way itself; that the spirals are primarily seen away from the Milky Way, because obscuring matter blocks the view through the plane of our galaxy. He paid special attention to the many novae being sighted within some spirals. He showed that if the flare-ups in Andromeda were half a million light-years distant, their luminosity would roughly match those seen in our own galaxy. Any closer and they would be far too bright. And then there was the movement of the spirals detected by Slipher; the spirals traveled speedily through space unlike any other celestial object in the Milky Way, which suggested that they had to be located outside our galaxy's borders.

All in all, the two men were simply talking at cross purposes. Shapley primarily defended his new vision of the Milky Way—its unexpected bigness—while Curtis hammered away on his contention that the spiral nebulae were far-off galaxies. In hindsight, each turned out to be partly right and partly wrong. Shapley argued for his larger Milky Way (true) but insisted that the spirals were local (wrong). Curtis still believed in a smaller home galaxy (wrong) but persevered in his belief that the spiral nebulae were situated far outside the Milky Way and rivaling it in size (true). At the end of the day, it was a wash.

Everyone in essence went home maintaining the beliefs they held at the start of the lecture. The data were so muddled that Curtis and Shapley could take the same facts and arrive at completely contradictory conclusions. At the time of the debate, there was no overwhelming evidence to settle the inconsistencies either way. Both men were traveling along a precarious road, each viewing his destination through an obscuring fog and interpreting the hazy view in different ways.

There was a winner, however, for best presentation. Curtis headed off that night feeling pretty good about his performance. He received assurances afterward that he “came out considerably in front.” Shapley, on the other hand, was judged more poorly. Russell wrote Hale afterward that his former student sorely needed to enhance the “gift of the gab.” Agassiz, the Harvard evaluator, was not impressed by Shapley's performance at all. “He has … a some what peculiar and nervous personality…lacks maturity and force, and does not give the impression of being a big enough personality for the position,” he reported back to Harvard's president two days after the event. More attractive to Agassiz was Russell, who spoke quite eloquently that night in support of Shapley's arguments during the audience response period. He said that Russell had “more balance more force and a broader mental range.”

The two opponents came to acknowledge what others sensed all along over the course of that April evening. “Yes, I guess mine was too technical,” admitted Curtis to Shapley a couple of months after the debate. “I thought yours would be along the same line, but you surprised me by making it far more general in character than I had expected.” As captivating scientific theater, the so-called Great Debate was ultimately a letdown.

A full year after the debate, however, the two astronomers battled it out once again within the Bulletin of the National Research Council. The original intent was to simply print the lectures they had given before the National Academy. But as the articles were being prepared, each man deepened and extended his arguments. It was not during that misty spring night in Washington that Shapley and Curtis had their great debate but rather within the pages of the Bulletin. It was the written version, vastly altered and amended, that ultimately established the legend handed down by succeeding generations of astronomers,