The Day We Found the Universe (26 page)

Go at Each Other “Hammer and Tongs”

T
he year 1920 was one of achievements—illustrious, infamous, resourceful, and humorous. American women got the vote, Joan of Arc was canonized by Pope Benedict XV, prohibition was initiated throughout the United States, an employee at the Johnson & Johnson company invented the Band-Aid, and the U.S. Post Office ruled that children may not be sent by parcel post. Moreover, astronomers didn't yet know exactly how the Sun generated its tremendous power or that the solar orb was largely composed of hydrogen, even though Einstein's newly introduced theory relating mass to energy, nicely summarized as
E = mc
²
, was offering a fresh clue.

What 1920 is best remembered for in the annals of astronomy is Harlow Shapley and Heber Curtis meeting in Washington, D.C., before members of the National Academy of Sciences to argue the arrangement of the universe. The sides were now clearly drawn, and it was time for a showdown. Shapley had, of course, recently pronounced that the Milky Way was far bigger than previously assumed, easily imagining the spirals as minor players hovering on the edge of our vast system of stars. Curtis, on the other hand, thought otherwise. This epochal encounter is commonly known as the “Great Debate,” al though in truth that's hardly an apt description at all. More like two lectures back to back, the event wasn't covered by even the science-oriented press. In astronomy circles, the venerable legend that surrounds that April session—the memory of it as the mighty clash of cosmic titans, astronomy's version of
High Noon
—developed gradually over time, the embroidery added so profusely over the years that it was eventually described as a “homeric fight,” two opposing sides battling it out in the highest court of scientific opinion.

This odyssey, though, began quite simply. George Ellery Hale had suggested at a council meeting of the academy that the 1920 Hale lecture on a topic of interest to scientists, an annual event established in honor of his father in 1914, be held during the academy's upcoming spring conference. He himself was leaning toward a discussion of Einstein's general theory of relativity, the trendiest scientific topic of the era. But the academy's home secretary, solar physicist Charles Greeley Abbot, feared that the revolutionary new view of gravity would already be “done to death” by the time of the meeting. The triumphant British solar-eclipse expedition was the science story of the year, still garnering headlines around the world. More than that, Abbot was wary of relativity's radical and difficult-to-comprehend concepts: “I pray to God that the progress of science will send relativity to some region of space beyond the fourth dimension, from whence it may never return to plague us,” he declared. Abbot wondered whether the “cause of glacial periods, or some zoological or biological subject” might be more appealing. The Prince of Monaco was even suggested as a lecturer, to speak on oceanography. But eventually Hale's second choice came to the forefront—the unresolved issue of the island-universe theory.

There was no question that Shapley, the thirty-five-year-old rising star, would defend his Big Galaxy idea. But who to pick for the other side? Lick Observatory director W. W. Campbell was briefly considered to champion the island universes, but Curtis, who had been devoting his professional life at Lick to this issue, was ultimately chosen, as by then he had become the leading spokesman for the claim. In terms of personalities, it was an interesting matchup. Shapley was acknowledged to be the “daring innovator, pressing the last bit of information from his observations, unafraid to extrapolate from the known to the unknown…occasionally depending upon intuition to supply connecting links.” Curtis, on the other hand, was considered a “cautious, sometimes overcautious, conservative who weighed every observation and more often concluded ‘not proven’ than ‘not so.’” Though not as prominent a figure as Shapley, Curtis was a respected astronomer nonetheless; by then forty-seven years old, bespectacled, and far less brash than his younger contender, he struck one as being a distinguished banker. Despite this stolid appearance, however, he proved to be the more venturesome one in regard to the upcoming talk.

With more professional experience under his belt, Curtis was quite comfortable at a podium and eager for a good tussle. But for Shapley, then ill at ease as a speaker, public exposure at this time was problematic. British historian Michael Hoskin first pointed out that Shapley had come to believe he was the front-runner for the directorship of the Harvard College Observatory, one of astronomy's most prestigious positions. Edward Pickering had recently died, having established a monumental legacy, and the search for his replacement was actively under way. Though young and completely untested in managing a world-class research institution, Shapley submitted his name for consideration, wanting to advance his career and strike while the iron was hot. Though he would be leaving the world's biggest telescopes, Shapley was enticed by Harvard's extensive collection of photographic plates, which offered a lush resource for the problems in which he was most interested. “Perhaps Harvard is amateurish, compared with Mount Wilson,” he told Russell, “but you and I…realize the enormous possibilities of the place.” More than that, it was an opportunity for Shapley to get away from his troubled relationship with Mount Wilson's deputy director, Walter Adams. Given this ambition, he worried how he would come across to certain members of the National Academy audience, who might have influence in the final decision. Curtis was known to be a dynamic lecturer; Shapley feared he would look bad by comparison. A letter from Curtis before the debate didn't calm his fears: “I am sure that we could be just as good friends if we did go at each other ‘hammer and tongs.’ … A good friendly ‘scrap’ is an excellent thing once in a while; sort of clears up the atmosphere.”

There was a flurry of correspondence between the participants and the National Academy in the months before the event, aimed at establishing the rules of engagement. Curtis was eager to air the controversy in a no-holds-barred debate. He told Shapley he wanted to “‘take the lid off’ and definitely attack each other's viewpoint.” But Shapley had a different agenda altogether. He wanted to discuss solely his new supersized model of the Milky Way and even informed Russell a few weeks before the debate that he didn't intend to say much about the spiral nebulae at all. “I have neither time nor data nor very good arguments,” he lamented. In fact, Shapley was relieved that the chosen title for the lecture, “The Scale of the Universe,” was ambiguous enough to allow him to carry out his plan. Shapley was quite reluctant to dwell on the spiral nebulae, a subject with such uncertain evidence. He hated airing science's dirty laundry in public.

Ardently voicing these concerns, Shapley convinced Hale that the so-called debate should be more of a discussion, “two talks on the same subject.” And instead of forty-five minutes for each speaker, as originally posed, Shapley asked for thirty-five. “My sympathies are with the audience, always,” he argued. “Could it listen to or endure nearly two hours of nebulosity?” Curtis was dismayed by this suggestion; he firmly believed he needed more time to lay out his scientific arguments. “We could scarcely get warmed up in 35 minutes,” he pleaded with Hale. After a while, they all compromised at forty minutes. And there would be no rebuttals. “If you or he wish to answer points made by the other, you can do so in the general discussion,” Hale told Curtis.

Shapley and Curtis were each paid an honorarium of $150, out of which they paid their travel expenses to journey from California to the East Coast. For Curtis it was $2 for the stagecoach to San Jose, then another $100 for the round-trip railroad ticket. By chance both Shapley and Curtis took the same train out to Washington via the southern route, but they agreed not to hash out their ideas ahead of time in order to keep their arguments fresh. When the train broke down at one point in Alabama, they got out and walked around for a while, keeping their conversation focused on flowers and the classics. Shapley didn't forget to collect a few native ants. In all likelihood, they were also, silently and unobtrusively, sizing up their competition.

The annual meeting of the National Academy of Sciences that year extended over three days. During the daytime sessions, a number of outstanding scientists presented talks. Franz Boas, the father of American anthropology, spoke on “growth and development as determined by environmental issues,” and rocket pioneer Robert Goddard advocated the use of rockets in weather forecasting. The “debate,” however, took place on the cool and showery evening of April 26, 1920, at the end of the conclave's first day. The audience of around two hundred to three hundred gathered in the Baird Auditorium of what is now the Smithsonian Institution's Museum of Natural History, prominently positioned along Washington's national mall directly across from the Smithsonian “castle.” In a news report the day before, the
Washington Post
announced that “Dr. Harlow Shapley, of the Mount Wilson solar observatory, will discuss evidence which seems to indicate the scale of the [Milky Way] to be many times greater than is held… Dr. Heber D. Curtis, of the Lick Observatory, will defend the old theory that there are possibly numerous universes similar to our own, each of which may have as many as three billion stars.”

The proceeding started at 8:15 p.m., and Shapley was the first to speak. He had been right to be nervous; two friends of Harvard president A. Lawrence Lowell—George Agassiz, a member of the Harvard astronomy department's visiting committee, and Theodore Lyman, chairman of its physics department—were in the audience to size him up. But Shapley came prepared. He made sure that Russell, still a valuable supporter of his cosmic model, was in the audience to back him up during the discussion period.

What exactly happened that night—the tenor of the speakers, the reception of the audience—is largely guesswork, based on the limited evidence left behind. Recollections of the event are riddled with false memories. Shapley, for instance, recalled an interminable banquet beforehand with honored guest Albert Einstein whispering to his table-mate that he “just got a new theory of Eternity.” But the conference dinner was the following night, and the noted theorist of relativity didn't make his first visit to America until the following year. However, Shapley did save the typescript of his talk, complete with last-minute scribbles (some in shorthand, a talent honed in his reporting days), which revealed his style and manner. Given the diversity of his audience, many not schooled in astronomy, Shapley chose to avoid technicalities and spent a good portion of his time just presenting basic astronomical facts: He carefully described the size of the Milky Way, its structure, and its constituent parts—the stars, gaseous nebulae, and clusters. He accompanied it with slides of the 100-inch telescope, the Moon, the Sun, the Pleiades cluster of stars, globular clusters. It was a visual tour of the known universe, with special attention paid to making the audience understand the meaning of a lightyear. “You do not see the sun where it is, but where it was eight minutes ago,” he instructed. “You do not see these stars as they are now, but more probably as they were when King Cheops was a little boy.”

Instead of talking about the nature of the spiral nebulae, the very reason for the encounter, Shapley focused on his Big Galaxy model. He figured that if he proved the Milky Way was immense, the spiral nebulae would automatically be relegated to minor status in the cosmic scheme of things, mere hangers-on. Anticipating that Curtis would challenge his use of the Cepheids as standard candles in determining the globular cluster distances, Shapley simply ignored the technique in his remarks. “[Curtis] may question the sufficiency of the data or the accuracy of the methods of using it,” he said. “But this fact remains: we could discard the Cepheids altogether, use instead the thousands of B-type stars upon which the most capable stellar astronomers have worked for years, and derive just the same distance [to the globular clusters]…and obtain consequently the same dimensions for the galactic system.” But Shapley was being disingenuous. Two years earlier he had reported to the Astronomical Society of the Pacific that the Cepheids carried “so much greater weight” for his distance measurements and that the magnitudes of red giants and blue stars “can best be used as checks or as secondary standards.”

Shapley went on to stress his finding that the Sun is not at the center of the Milky Way: “We have been victimized by the chance position of the sun near the center of a subordinate system [of stars], and misled by the consequent phenomena, to think that we are God's own appointed, right in the thick of things.” As for the spirals? “I shall leave the description and discussion of this debatable question to Professor Curtis,” he said. Shapley conceded that the possibility remained that they were comparable galactic systems, but only if the Milky Way were cut down to a tenth of his newly defined dimensions. He believed that unlikely and preferred to think of the spirals as nebulous objects. He maintained “that it is professionally and scientifically unwise to take any very positive view in the matter just now.”

One can imagine Curtis's mounting dismay as his opponent was progressing through his talk. Shapley had spent most of his time on just the basics of astronomy, while Curtis had prepared a full-fledged analysis, laden with scientific detail. The Lick astronomer was about to address the audience on issues that Shapley had never brought up. While he anxiously awaited his turn at the podium, his mind raced, wondering whether he should change his approach on the fly, making his presentation more relaxed and general. But in the end he decided to stick to his original plan.

Unlike with Shapley, a copy of Curtis's script no longer exists, but some of his slides, displaying his essential points, do survive, and they provide a glimpse of the flow of his arguments that evening. Contrasting sharply with Shapley's popular approach to the topic, Curtis's talk was more technical, although by all accounts he spoke more spontaneously. At first he focused on one of his major disagreements with Shapley: the size of the Milky Way. He carefully outlined his reasons for believing that the Milky Way was a tenth the size that Shapley was hawking. Mainly, he had no confidence in Shapley's use of the Cepheids. Shapley himself knew that his momentous refashioning of the Milky Way's size stood on the foundation of eleven “miserable” Cepheids, as he had earlier described them in a letter.