by Dava Sobel
Thanks to a 1915 change in the society’s charter, women could now be elected fellows (if British subjects) and associates (if foreigners). Miss Cannon felt content to retain her “honorary” status, but she took Turner up on another of his suggestions in the spring of 1919, regarding the Maria Mitchell Association. “It might be possible, let us say as a friendly act at the present moment of great events and important new departures,” Turner thought, “to assign one of the Fellowships to an Englishwoman. I need scarcely point to the advantages which such action would have both in encouraging woman’s work generally, in cementing friendly relations between the two nations, and in creating a new form of recognition.” Miss Cannon’s committee had already decided on Miss Maury for the coming year, but the members heard in Turner’s words an echo of “Professor Pickering’s international spirit,” and promised to search overseas for the next Pickering Fellow.
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HARLOW SHAPLEY’S “BIG GALAXY,” as he described it in 1918, filled the known universe. It was so immense that it subsumed everything else: globular clusters rimmed it, nebulous forms fit inside it, and the Magellanic Clouds hung from it as appendages. But numerous astronomers refused to be bound by it. Unlike Shapley, they viewed the Milky Way as one galaxy among many—a single “island universe” in a vast archipelago.
Shapley, too, had ascribed to the island-universe theory up until 1917. But once he exploded the size of the Milky Way to titanic proportions through his distance assessments of the globular clusters, he changed his mind. The enormity of the Milky Way ruled out the existence of other, comparable galaxies. Nothing substantive surrounded it, Shapley thought, other than dross and empty space.
Deciding the truth of the island-universe matter depended on determining the placement of the spiral nebulae. These pinwheels of celestial light had been sighted by the thousands, beginning in the mid-nineteenth century, when William Parsons of Ireland and his friends first viewed their distinctive forms through the huge reflecting telescope known as the Leviathan of Parsonstown. The spirals, as they were called for short, looked as though they might be whirlpools of incandescent gas, or whirlwinds of interstellar dust, or whorls of stars. It was difficult to say without knowing their distances. Some astronomers saw each spiral’s bright center and trailing arms as a new solar system of a sun and planets in the making. Those who viewed the spirals as full-blown external galaxies, however, divined in their coiled forms a likely blueprint for the Milky Way.
George Ellery Hale thought the disagreement over the spirals an apt subject for a public debate. When he proposed the topic to the National Academy of Sciences late in 1919, he also named general relativity, which had been much in the news, as an alternate theme possibility. The idea of relativity put forth by Albert Einstein in 1915 was changing the nature of space from a passive container of the stars to a fabric warped by the stars’ presence. Einstein’s German roots and the course of the Great War at first slowed the theory’s acceptance, but the English pacifist Arthur Stanley Eddington tested its validity during the May 29, 1919, total solar eclipse, which he observed from the African island of Príncipe. It was an eclipse expedition even Pickering would have approved. The stunning results, announced in November 1919, demonstrated that light waves indeed felt the effect of gravity—and by the amount Einstein had predicted. The erudite Eddington expressed the findings in poetry as well as prose, borrowing the rhythm of the Rubaiyat of Omar Khayyam: “Oh leave the Wise our measures to collate / One thing at least is certain, light has weight / One thing is certain and the rest debate / Light rays, when near the Sun, do not go straight.”
Given a choice between relativity and the galaxy, the Academy secretary, solar astronomer Charles Greeley Abbot, expressed a strong preference: “As to relativity I must confess that I would rather have a subject in which there would be a half-dozen members of the Academy competent enough to understand at least a few words of what the speakers were saying if we had a symposium upon it. 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.” Having thus settled the discussion topic in favor of spirals, Abbot invited Shapley to present his mono-galaxy idea, and Heber D. Curtis of the Lick Observatory to argue the case for multiple galaxies.
The event took place in Washington, D.C., on the evening of April 26, 1920. Shapley, who was known to behave at times in brash and overconfident ways, withered even before he took the podium. Not only did he fear being upstaged by a smooth public speaker of Curtis’s stature, but he had learned well ahead of showtime that Agassiz from the Harvard Observatory’s Visiting Committee would be in the audience to judge his fitness for the director slot. Unfortunately, Shapley pitched his prepared talk at a level appropriate for intelligent laymen, and it impressed no one. Speaking first, he took several minutes to explain the meaning of a light-year as the distance that light traveled in a year. “Now that we have a satisfactory unit of sidereal distance,” he said, reading from his script, “let us go rambling about the universe.” He led a pictorial tour through star clusters near and far, including those seen in Orion and Hercules, but promised, “I shall not impose upon you the dreary technicalities of the methods of determining the distance of globular clusters.” He sidestepped the spirals, except to stress how little was actually known about them. “I prefer to believe that they are not composed of stars at all, but are truly nebulous objects”—in a word, diffuse. Even if the spirals are stellar, he conceded in closing, they are not comparable in size with our stellar system, the Milky Way.
Curtis then came forward, intent on reducing Shapley’s gargantuan galaxy to about one-tenth its grandeur—to the apparent size, that is, of a typical spiral. He laid out abundant arguments in favor of the spirals’ being galaxies, including evidence for the Milky Way’s own spiral shape. Examination of spirals’ spectra, Curtis said, suggested that many more of them were made of stars than of free-flowing gas. In recent years, about a dozen spirals had lit up with new-star flare-ups, such as the 1895 nova that the late Williamina Fleming discovered in the Centaurus spiral. Curtis interpreted the presence of these novae as proof that spirals contained at least some stars, although opponents of the island-universe idea argued that novae arose when spirals collided with stars. Certainly spirals were on the move: Their spectra indicated tremendous speeds in the line of sight, as though most of them were rushing away from the Sun. Curtis saw these fantastic velocities as further testimony to the spirals’ extragalactic location, since no stars within the Milky Way moved as rapidly. Curtis made all his points forcefully, and afterward boasted justly to his family that he had triumphed in the debate.
The face-to-face confrontation ended when the auditorium emptied that night, but the question of the spirals remained undecided. Shapley and Curtis continued their contest via correspondence over the ensuing months as they framed their presentations for publication in the Bulletin of the National Research Council. They traded drafts and weighed the worth of competing claims, but neither could win the other over to his side. While Shapley waited to hear whether Harvard would hire him, Curtis accepted the directorship of the Allegheny Observatory, and moved from California to Pennsylvania.
Those two states, California and Pennsylvania, had joined Massachusetts, Missouri, and thirty-one others by the summer of 1920 in ratifying the nineteenth amendment to the U.S. Constitution. One more state’s sanction was still needed before women nationwide gained the right to vote. On August 18, during a special session in the Tennessee House of Representatives, the measure narrowly won support and became law. Miss Cannon went to the polls at the first opportunity, on September 7, to cast her ballot in the primary. She marked November 2, 1920, as “Election Tuesday” in her diary: “Gray day, and cold. Women out in force. I went with the Baileys at 10:30. Voting is very easy!” That evening she stopped on Boston Common to get the latest election bulletin, and absorbed the general e
nthusiasm for Senator Warren G. Harding of Ohio as the twenty-ninth president of the United States.
In England that autumn, the fourth Pickering Fellow, Miss A. Grace Cook of Stowmarket, stayed outdoors for hours every night to observe meteors, commonly known as falling or shooting stars. Seated in a deck chair, Miss Cook scanned the skies for sudden moving lights that signaled the entry of a bit of space rock or comet dust into Earth’s atmosphere. When a meteor appeared she clicked her stopwatch to time its flight, and with her other hand held aloft a straight, thin wand, about five feet long, aligned with the intruder’s path. In the few seconds of visibility, she memorized the meteor’s changing magnitude compared with that of the stars it passed from apparition to disappearance, and then jotted down her accumulated data. In daytime she could plot the several pathways on a celestial globe to find the radiant, or point of origin, for a given meteor shower. And although the wet English weather often thwarted her, she also observed other naked-eye phenomena such as aurorae and lunar halos, and hunted comets through the small telescope she purchased with her stipend. On February 9, 1921, after receiving the second half of her grant money from Professor Turner of Oxford, she wrote to Miss Cannon, “He seems to understand what a boon such a gift is to an isolated worker and one who can only set aside a small sum yearly to devote to science. It is like a lovely dream come true. I only hope I have made the very best use of it. I have done my best to do so.” After months of reclusive work she added, “Most of my astronomical friends imagine I am in America at Harvard; they think the Fellowship was a residential one!”
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MISS CANNON HAD KNOWN all along how things would turn out. The very first time she met Harlow Shapley, during his 1914 visit to Cambridge as a Princeton graduate student, she told him, “Young man, I know what you’re going to do. You’re going to be the director of the Harvard Observatory.” Then she laughed. Shapley remembered her laugh years later, as something prophetic, or possibly psychic, when Harvard at last offered him the job.
“Dr. Shapley arrived!” Miss Cannon wrote in her diary on March 28, 1921. The next day she had “a long talk” with him, and decided, “I like him. So young, so clear, so brilliant.” In fact, the thirty-five-year-old Shapley had not yet been named director; he was technically on probation, with the vague title of “observer.” Given his sub-stellar performance in the scale-of-the-universe debate, and the hubris with which he put forth his daring theories, the untried new leader had been given just one year to prove himself worthy of Harvard’s trust. If he should clash with the university or the observatory, then George Ellery Hale would gladly take him back at Mount Wilson.
Shapley himself considered the Cambridge relocation a permanent one. He spent several weeks that spring preparing the director’s residence to receive his family, while Martha and the three children, Mildred, Willis, and Alan, visited relatives in Kansas City.
On his first day at the observatory, Shapley stopped by Miss Cannon’s office and asked to see the spectrum of SW Andromedae, a faint variable that had aroused his interest. She called out to an assistant to retrieve a particular plate, identifying it by a five-digit number catalogued in her prodigious memory. To Shapley’s amazement, “The girl went to the stacks and got the plate and SW Andromedae was on it!”
With Miss Cannon, Shapley initiated an investigation into the distribution of the stars of different spectral types, tallying the number in each class over a wide range of magnitudes. Pickering had attempted a similar statistical analysis decades before, with only one-twentieth the amount of data Shapley now found at his disposal in the Harvard plate collection. The Brick Building held the whole sky captive inside a hive of industry.
“Luckily Harvard College was swarming with cheap assistants,” Shapley said of his early days as observer. “That was how we got things done.” At Mount Wilson he had grown accustomed to making his own measurements of photographic plates. At Harvard he invented the term “girl-hour” for the time spent by young and not-so-young women at various plate-measuring and computing tasks. “Some jobs,” he quipped, “even took several kilo-girl hours.” Surely the ongoing preparation of the Henry Draper Catalogue figured among the more laborious. The fourth volume had been printed before Shapley’s arrival, with the help of donations from observatory friends James and Margaret Jewett and members of the American Association of Variable Star Observers. Now veteran computer Florence Cushman was reading Miss Cannon’s proofs for volumes five and six.
Shapley passed over the prim Ida Woods, who had served as Pickering’s unofficial secretary, and instead selected the younger, more affable Arville “Billy” Walker to assist him with his correspondence. He straightaway engaged Miss Leavitt in a study of the different types of variables in the Magellanic Clouds. Together they demonstrated that the Clouds contained short-period, cluster-type variables, in addition to Cepheids. This was just the confirmation Shapley needed to shore up the great distances he had derived for the globular clusters—the distances on which his enlargement of the galaxy depended.
Further support for Shapley’s Big Galaxy reached him in the spring of 1921 from his Mount Wilson friend and colleague Adriaan van Maanen. After comparing plates of the same spirals taken on dates years apart, van Maanen tied their swirling shapes to what he perceived as a real spinning motion. The spirals not only spun, van Maanen argued, but also their rapid rates of rotation suggested they resided within the Milky Way. At distances no greater than a few thousand light-years from the Sun, their spin pace remained within reason. If removed to the distance of an external galaxy, however, then the millimeters he had marked on the plates would translate into many times more kilometers traveled through space, and accelerate the rotation to exceed the speed of light. Since nothing could move faster than light, van Maanen’s measurements of the spiral nebulae reduced the island universes to absurdity in Shapley’s eyes.
“Congratulations on the nebulous results!” Shapley cheered to van Maanen on June 8. “Between us we have put a crimp in the island universes, it seems,—you by bringing the spirals in and I by pushing the Galaxy out. We are indeed clever, we are.”
Shapley introduced himself to the wider Harvard community by offering a colloquium on astronomy, in which he tried hard to improve his performance over the previous year’s “debate” in Washington. This time he told jokes. Former president Charles Eliot, who attended the talk, advised Shapley afterward that he need not embroider his grand subject with gratuitous humor.
In his attempt to win new friends for astronomy from Cambridge and Boston, Shapley instituted a series of open nights, inviting the public to hear a nontechnical lecture and peer through some of the telescopes. Admission was free, but interested visitors needed to register for tickets, since the observatory could not accommodate large crowds, and many sought entry. Pleased with the response, Shapley also planned to set aside separate nights for welcoming pupils from the local schools, as well as groups of boys’ and girls’ club members.
In the fall, when Hale inquired whether he should anticipate Shapley’s return to Pasadena, Lowell said Harvard meant to keep him in the East. University officials had voted to appoint Shapley as permanent director on the very day Hale’s letter arrived, October 31, 1921.
As soon as Shapley relaxed into his leadership role, he awoke to the menace lurking in Mandeville. William Pickering released his latest research results in Popular Astronomy, and newspapers quickly picked up the Jamaica-based Harvard professor’s account of “Life on the Moon.” William reported vegetation sprouting on the lunar surface in rapid regular cycles, with abundant water and occasional steam emanating from craters. “We find, therefore,” William asserted, speaking for himself, “a living world at our very doors, where life in some respects resembles that on Mars, but utterly unlike anything on our own planet, a world which the astronomical profession in general for the past fifty years has systematically neglected.”
William was cur
rently on sabbatical in Europe, a perquisite that Bailey had won for him from the Harvard Corporation. Bailey had tolerated William’s excesses, and even gained him a small salary increase—the first raise in William’s thirty-plus years on the observatory staff. “It seems to me that one can safely accept most of his observed phenomena,” Bailey said in William’s defense. “The difficulty comes in the interpretation.” Shapley had no such patience. He planned to terminate Harvard’s connection with the Woodlawn Observatory in Mandeville the moment William reached the age for mandatory retirement.
At the same time, but with a very different emotion, Shapley faced losing Miss Leavitt, whom he valued as “one of the most important women ever to touch astronomy.” The discoverer of the period-luminosity law was dying of cancer. “One of the few decent things I have done,” Shapley wrote in his memoir, “was to call on her on her death bed; it made life so much different, friends said, that the director came to see her.”
Miss Cannon called often on Miss Leavitt toward the end, taking small gifts and marking each decline in her diary. “December 12. Rainy day pouring at night. Henrietta passed away at 10:30 p.m.” On the fourteenth Miss Cannon attended “Henrietta’s funeral at Chapel of 1st Cong. Church 2 p.m. Coffin covered with flowers.”
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SOLON BAILEY WITHDREW GRACEFULLY from the helm of the Harvard Observatory. In order to give the new director room to maneuver, Bailey offered to return to Peru for another sojourn at Arequipa. Along with his wife, Ruth, he anticipated a fruitful reunion with the southern star clusters. Their son, Irving, now a Harvard professor of botany and married to Margaret Harwood’s sister Helen, did not accompany them this time. However, Miss Cannon did, encouraged by Shapley to take her own plates of the Milky Way, for later classification of stars fainter than ninth magnitude. She kept a close, lyrical account of her travels: “The sky line of New York faded away in a drapery of moist snow on March 1, 1922, when the Grace Liner Santa Luisa steamed out for Panama, Peru, and Chile.”