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 light-years.
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.”
Edwin Hubble developing a photograph in the darkroom
(Reproduced by permission of the Huntington Library,
San Marino, California)
And yet, despite his myriad pages of data—proof upon proof of a universe beyond the boundaries of the Milky Way—Hubble still did not publish. Given the relentless reconstruction he performed on his personal life story over the decades, it is obvious that Hubble's ego was fragile. But these boastful embellishments were attached to his life, never to his scientific achievements. Highly conservative when it came to celestial speculation, Hubble never stuck his neck out in the arena of science, unlike Shapley, who readily (and loudly) broadcast his conjectures. Hubble's legal training might well have taught him to restrain his musings until the facts were firmly in hand, or perhaps he couldn't stand the thought of the disgrace if he had to retract his discovery, one that was going to remake the universe.
It was easier for Hubble at this stage to discuss his new findings informally. In July, he wrote Vesto Slipher on routine astronomy committee matters and at the very end of his letter casually mentioned his latest work: “You…may be interested to hear that variable stars are now being found in the outer regions of Messier 31. Already a half dozen are definitely established and several others are under suspicion… You can realize how eager I am to get curves for the others, and how bashful to discuss prematurely the Period-Luminosity relations.” Hubble didn't know that Slipher had already heard about the intriguing finds. The news was rapidly spreading on the astronomical grapevine. Curtis became aware of Hubble's discovery the previous March; Shapley, of course, even earlier. And Princeton's Henry Norris Russell first heard it from James Jeans in England! The tendrils of the grapevine had a long and convoluted reach.
Besides Hubble, no one had more at stake on the outcome than Adriaan van Maanen. If Hubble's discovery held up, it meant he was wrong about his rotating spirals. So, van Maanen made sure to keep tabs on this new development at his observatory and glean all the latest gossip. “What do you think of Hubble's Cepheids,” he wrote Shapley.
Shapley, meanwhile, was receiving updates from Hubble, hearing about the latest variables he was finding, including some in other spiral nebulae. “I feel it is still premature to base conclusions on these variables in spirals,” Hubble wrote him in August, “but the straws are all pointing in one direction and it will do no harm to begin considering the various possibilities involved.”
Hubble was gaining more confidence in his findings. And Shapley, in response to the growing body of evidence, at last saw the scientific handwriting on the wall. He cried uncle, acquiescing speedily and graciously. While visiting Wood's Hole in Massachusetts with his family for a summer holiday, helping dredge starfish at one point off Martha's Vineyard, Shapley briefly paused in his frolicking to respond to Hubble's August letter. He described the new results as “exciting.”
“What tremendous luck you are having,” he wrote. “I do not know whether I am sorry or glad to see this break in the nebular problem. Perhaps both.” Shapley knew his change of heart now meant abandoning his Big Galaxy model of the universe and questioning the spiral rotation measurements of van Maanen, his good friend. He regretted that this had to happen, but Shapley was also relieved to have something definite about the spirals at last come to light. Once proven wrong, the Harvard Observatory director didn't look back and quickly adjusted to the new cosmic landscape, soon becoming its most boisterous promoter.
By the end of 1924 Hubble was finally starting to write a preliminary draft of his findings for the Proceedings of the National Academy of Sciences. He was dipping his toe into the proverbial water, but he was hardly leaping into the drink. As Hubble wrote Slipher on December 20, he was still hugely frustrated by van Maanen's contradictory observations on the spiral rotations. If the spiral nebulae truly resided in distant space, at least a million light-years away, no astronomer could possibly see them rotate in a matter of years. How could he make that conflict go away? “I am wasting a good deal of time investigating the possibilities of magnitude effect in van Maanen's measures. The suggestion is very strong among the comparison stars of M33 and M81 but I can not carry it through some of the others,” he told Slipher. Had he truly discerned the source of van Maanen's error? Were the apparent magnitudes of the spiral stars that van Maanen picked out to make his measurements differing from plate to plate because observing conditions were dissimilar or the star was imaged on a different part of the plate? That could make it tricky to pinpoint each star's exact center, which would lead him to mistakenly measure the stars as moving, making it seem as if the entire spiral were rotating. Or was it something else? Before publishing anything, Hubble wanted to confront and overturn each and every result in van Maanen's work that was at odds with his discovery. He closed his letter to Slipher saying that he would not be attending the latest meeting of the astronomical society, starting in ten days in Washington, D.C.
Word of Hubble's discovery was still spreading like wildfire through the astronomical community. Though not yet official, the news even made it into the New York Times. Readers turning to page 6 on November 23, 1924, saw this headline (complete with misspelling): “Finds Spiral Nebulae Are Stellar Systems—Dr. Hubbell Confirms View That They Are ‘Island Universes’ Similar to Our Own.” With Hubble revealing that the Andromeda and other nebulae were at least a million light-years distant, reported the newspaper, then “we are observing them by light which left them in the Pliocene age upon the earth.”
Yet Hubble continued to stall, unwilling to rush his finding into the scientific literature. Though the island-universe theory had been gaining supporters, others persisted in regarding the spiral nebulae as minor entities. But the scent of resolution was in the air. At the December 1924 meeting of the British Astronomical Association, Peter Doig, a prominent figure in British amateur astronomy, presented a paper on the spiral nebulae that cautioned that “the rapid progress of knowledge, and the changing state of speculative theories of the nature and origin of these objects, perhaps make the compilation of… a paper [on the topic]…rather a risky procedure.” Doig didn't realize how fast his prophecy would come true. The mountain of doubts and reservations concerning the spirals came tumbling down in less than a month.
Russell was so impressed by Hubble's accomplishment that he nominated the young Mount Wilson astronomer for membership in the National Academy of Sciences, quite an honor for someone still junior in his profession. Formerly a solid supporter of Shapley's cosmic model, the Princeton astronomer had now done a quick about-face. Just ten months earlier he had been lecturing that spirals were nearby, supported by van Maanen's evidence, but now Russell was telling the managing editor of Science Service that Hubble's find was “undoubtedly among the most notable scientific advances of the year.” He contacted Hubble and encouraged him to publish his results as soon as possible, wanting him to present a paper at the thirty-third meeting of the American Astronomical Society, which was going to be held jointly that year with the annual conference of the American Association for the Advancement of Science.
“Heartiest congratulations on your Cepheids in spiral nebulae!” wrote Russell on December 12. “They are certainly quite convincing. I heard something about them from Jeans a month or two ago, and was wondering when you would be ready to announce the discovery. It is a beautiful piece of work, and you deserve all the credit that it will bring you, which will undoubtedly be great. When are you going to announce the thing in detail? I hope you are sending it to the Washington meeting, both, because we all want to know all about it, and because you ought, incidentally, to bag that $1000 prize.” Th
e Council of the American Astronomical Society was ready to nominate Hubble's paper for the prestigious $1,000 AAAS prize (a substantial sum of money in its day) given to the best paper read at the gathering. It was only the second year for the competition, and the Washington Post was reporting “considerable interest” in the outcome.
But Hubble was hesitant to change his plans. As he later related to Russell, “The real reason for my reluctance in hurrying to press was, as you may have guessed, the flat contradiction to van Maanen's rotations.” Van Maanen was a more senior member of the Mount Wilson staff, and Hubble was hoping to avoid a public conflict, even fantasizing that there might be a way to reconcile the two contradictory sets of data. “But in spite of this,” he admitted, “I believe the measured rotations must be abandoned… Rotation appears to be a forced interpretation.”
Russell assumed his letter (and the lure of the prize) would finally persuade Hubble to put aside his concerns and make the discovery official once and for all. As soon as Russell arrived at the Washington conference, he had dinner with University of Wisconsin astronomer Joel Stebbins, then secretary of the astronomical society, and eagerly asked Stebbins whether Hubble had as yet sent in his paper. When Stebbins replied no, Russell was flabbergasted and declared that Hubble was “an ass!! With a perfectly good thousand dollars available he refuses to take it.”
A telegram was quickly drafted, urging Hubble to send his principal results by overnight letter. Both Russell and Shapley stood ready to take Hubble's data, whatever he chose to convey, and turn it into a proper paper for the meeting. But just as Stebbins and Russell were about to go over to the telegraph office, Russell noticed on the floor behind the hotel desk a sizeable envelope addressed to him. Stebbins spied Hubble's name in the return address. Hubble had mailed his paper after all, and in the nick of time. “We walked back to the group in the lobby, saying that we had got quick service,” Stebbins later told Hubble. “That coincidence seemed a miracle.”
The Day We Found the Universe Page 24