The Day We Found the Universe (34 page)

The photographic plate of Andromeda (M31) on which Edwin Hubble
identified a Cepheid variable star, mistaken at first for a nova, in a spiral
nebula—the first step in Hubble's opening up the universe
(Courtesy
of the Observatories of the Carnegie Institution of Washington)

At some point during these deliberations, Hubble went back to his logbook, page 157, and quickly scrawled an added note on the side of the page to amend the report of his October 5 observing run. Customarily reserved, Hubble at this moment is unmistakably restive. He didn't write his message in black ink, which he regularly did for his records, but instead in pencil. And his handwriting, usually so fluid and precise, was more hurried and askew. He was obviously elated: “On this plate (H 335 H), three stars were found, 2 of which were novae, and 1 proved to be a variable, later identified as a Cepheid—the 1st to be recognized in M31.” To highlight the addition, he drew a big arrow, pointing directly downward at his historic news. In its broad stroke, the arrow makes his excitement visible upon the page. For once Hubble dropped his guard and figuratively clicked his heels at this moment of discovery.

Hubble couldn't help but notify his nemesis. On February 19 he wrote Harlow Shapley about his efforts over the previous months. Hubble didn't open with polite niceties or inquiries of health. He got straight to the point. “Dear Shapley:—You will be interested to hear that I have found a Cepheid variable in the Andromeda Nebula (M31). I have followed the nebula this season as closely as the weather permitted and in the last five months have netted nine novae and two variables.” His glee in communicating this news jumped off the page as he then provided Shapley with all the technical details on color index corrections and magnitude estimations. Shapley was, after all, the world's reigning Cepheid expert—not only in using them as standard candles but figuring out early on, soon after he arrived at Mount Wilson, that they were pulsating stars, their atmospheres repeatedly ballooning in and out.

Pages 156 and 157 of Hubble's 100-inch telescope logbook
(Reproduced by permission of the Huntington Library
,
San Marino, California)

Accompanying this legendary letter was a graph that Hubble had fastidiously drawn in pencil on paper torn from a notebook. It displayed the light curve for his “Variable No.
1”
in M31—a roller-coaster ride that peaked at eighteenth magnitude, dipped a bit below nineteenth magnitude, and then rose once again to its maximum brightness over a period of thirty-one days, “which, rough as it is,” he told Shapley, “shows the Cepheid characteristics in an unmistakable fashion.” And here was the kicker. Hubble used the exact same technique for gauging a distance to the spiral that Shapley had devised for mapping the arrangement of globular clusters around the Milky Way. Applying the Cepheid period-luminosity formula that Shapley had derived, Hubble calculated a distance to Andromeda of around 1 million lightyears (“subject to reduction if star is dimmed by intervening nebulosity,” he carefully noted). No more oblique evidence or convoluted reasoning, such as Heber Curtis was forced to use. The Cepheid provided a direct and indisputable yardstick out to the nebula. Andromeda was indeed an island universe.

Edwin Hubble's graph of the periodicity of Variable No. 1
in Andromeda, included in his letter to Harlow Shapley that
destroyed Shapley's universe (
Harvard University Archives, UAV 630.22
,
1921-1930, Box 9, Folder 71)

The second Andromeda variable, which Hubble had later found at the very edge of a spiral arm, was too faint for him to make a reliable distance measurement as yet. But no matter. “I have a feeling that more variables will be found by careful examination of long exposures. Altogether the next season should be a merry one and will be met with due form and ceremony,” said Hubble at the close. He was having a fine time at Shapley's expense.

Shapley, upon reading the letter, immediately grasped that Hubble's finding spelled doom for his cherished vision of the cosmos. Harvard astronomer Cecilia Payne (later Payne-Gaposchkin) happened to be in Shapley's Harvard office when Hubble's message arrived. He held out the two pages to her and exclaimed, “Here is the letter that has destroyed my universe.” Hubble was at last confirming the speculation that had been circulating through the astronomical community since the days of Thomas Wright, Immanuel Kant, and William Herschel. The Milky Way was not alone, but merely one starry isle in an assembly of galactic islands that stretches outward for millions of lightyears.

Though Shapley assuredly sensed this sea change, he continued for a while to put up a good front. He mischievously wrote back that the news of “the crop of novae and of the two variable stars in the direction of the Andromeda nebula is the most entertaining piece of literature I have seen for a long time.” He wouldn't even concede that the variables were
in
the nebula, only “in the direction of.” He admitted that the second variable is a “highly important object” but went on to caution Hubble that his first variable star might not be a Cepheid after all, which meant it would be unreliable as a distance marker. And even if it were, he went on, Cepheids with periods greater than twenty days are “generally not dependable…[and] are likely to fall off of the period-luminosity curve.”

Hubble was undeterred by Shapley's caveats and continued his searches at a brisk clip. His discovery spurred him to find even more Cepheid variables, in both Andromeda and other spiral nebulae. But cautious as ever, he made no public announcement. Not yet.

Just a week after sending off his triumphant communiqué to Shapley, in the very midst of these cosmos-altering observations, Hubble married, a surprise to many. His bride was Grace Burke Leib, thirty-five years old and the daughter of a wealthy Los Angeles banker. A smart and petite woman, Grace had graduated Phi Beta Kappa from Stanford University with a degree in English. She had compelling dark eyes and lustrous brown hair, but a stern mouth. She was more handsome than beautiful. Grace had been previously married to geologist Earl Leib, who specialized in assaying coal deposits and was tragically killed in a mining accident in 1921. Leib's sister was the wife of Lick Observatory astronomer William Wright, a connection that first put Grace in contact with Mount Wilson's most eligible bachelor while she was still married. When Wright visited Mount Wilson to carry out some observations in the summer of 1920, he took along his wife and sister-in-law, who stayed in a visitors' cottage on top of the mountain. Going over to a small library tucked away in the laboratory building one day to borrow some books, the two women came across Hubble. Years after Hubble's death, swept up in the nostalgic haze that colored most of her writings about her husband, Grace recalled that moment: “He was standing at the laboratory window, looking at a plate of Orion. This should not have seemed unusual, an astronomer examining a plate against the light. But if the astronomer looked like an Olympian, tall, strong, and beautiful, with the shoulders of the Hermes of Praxiteles, and the benign serenity, it became unusual. There was a sense of power, channeled and directed in an adventure that had nothing to do with personal ambition and its anxieties and lack of peace. There was a hard concentrated effort and yet detachment. The power was controlled.”

By 1922 Hubble and Grace, who was now widowed, renewed their acquaintance and the couple, soon smitten, began a discreet courtship. She, more than anyone else, came to see Hubble's gentler side, his spontaneous and hearty laugh whenever someone surprised him or made an original remark. A reserved man not prone to idle chatter, he could still display a dry wit at moments. After Hubble had made the rounds of New York nightclubs one evening with a friend, his companion finally collapsed and said, “I've got to turn in. How can you stay up this way?” To which Hubble replied, “Do you think you can stay up later than an astronomer?”

Hubble wooed Grace with gifts of books and by reading to her and her parents when visiting the family's Los Angeles home. On February 26, 1924, they were married in a private Catholic ceremony (Grace's faith), with none of Hubble's family members in attendance. After honeymooning at her family's cottage, set on six scenic acres near Pebble Beach, in Carmel, they toured Europe.

Edwin and Grace Hubble on their wedding day in 1924
(Reproduced by permission of the Huntington Library
,
San Marino, California)

With their fondness for outdoor pursuits—riding, hiking, and fishing—and their stylish outfits, the Hubbles would have felt right at home in the countryside of aristocratic England. In California, they liked to mingle with the elite of Hollywood society rather than astronomers: writers, directors, and actors, such as Helen Hayes, George Arliss, and Charlie Chaplin. Given Hubble's fervent Anglophilia, they also hung out with members of Hollywood's long-established British colony, which at one point included the noted authors Aldous Huxley and H. G. Wells.

The Hubbles were a highly compatible match, as they both enjoyed the ways of high society (Grace grew up being chauffeured about in one of her family's two Cadillacs; Edwin got his suits and shirts custom-made in London) and always maintained a polite reserve; as one acquaintance noted, “A stranger could drop raspberry soufflé on the rug without hearing a murmur.” Those who observed their interactions called the couple's relationship “quite out of the common.” Given Edwin's astute powers of observation—he had a remarkable eye for detail—Grace said she “was Watson to his Sherlock Holmes.”

As soon as Hubble returned in May from his three-month honeymoon—the very evening of his arrival, in fact—he was back on the mountain applying those Sherlockian skills to his study of the spiral nebulae. Throughout the remaining months of 1924 he found even more variables, tracking the ups and downs of each luminosity with care. It was plodding work. A dozen of the thirty-six variables he ultimately found in Andromeda turned out to be Cepheids, their cycles ranging from eighteen to fifty days. He did even better when he started studying M33, a striking face-on spiral in the Triangulum constellation, situated right next door to Andromeda toward the east. There Hubble found a total of twenty-two Cepheids with a similar range of periods, which provided him with a rich sample for calculating the nebula's distance.

In these days long before computers or handheld calculators, Hubble's computations for assessing the magnitudes of his Cepheids and determining their periods were scribbled on pieces of flimsy yellow paper or heavy graph paper—hundreds of pages now filed away in an archive. Points were carefully plotted on a graph to indicate a Cepheid's changing luminosity. As if playing connect the dots, Hubble then drew a crude line through the points, which displayed across the page the steady rising and falling of the Cepheid's light.

Hubble was not the best astronomer when it came to equipment. Anxious to see his results, he sometimes cut corners in the darkroom, not always using fresh developer or trimming the time for fixing and washing. The photographs and spectra he handled himself were often scratched up and required retouching before publication. But as a celestial accountant he was superb. Hubble patiently carried out his computations for variable after variable. Novae, as well, were studied and tabulated. It's the very core of astronomical work, the endeavor that is never glorified, carried out as the astronomer is hunched over a desk far away from the telescope. It was there in his quiet, book-lined office on Santa Barbara Street in Pasadena—a spacious but spartanly furnished room once occupied by Hale—that Hubble truly discovered the universe. As Caltech astronomer Jesse Greenstein once said, astronomical observing “is one lump of beauty mixed with lots of incredible boredom and discomfort…. A single fact involves a tedious, incredibly long, difficult process.”