The Day We Found the Universe - Marcia Bartusiak (2009)
Chapter 13. Countless Whole Worlds... Strewn All Over the Sky
October 4, 1923. The seeing was poor, but it was good enough (just barely) to stalk some celestial quarry that autumn evening. Hubble first pointed the 100-inch at NGC 6822, the far-off, Magellanic-like cloud of stars that he had long been studying. As the giant scope swung around, there was a whine, a series of loud clicks, and then a final clang as the instrument was secured into place. After taking an hour-long photographic exposure, Hubble went on to examine M32, a small and roundish nebula, for a spell. He then maneuvered the telescope just a fraction of a degree to photograph M31—the famous Andromeda nebula, the target of choice in the island-universe debate. By then the seeing had deteriorated to a point that other astronomers might have closed up shop. But Hubble persevered, and despite the mediocre viewing, soon noticed a new speck of light within Andromeda's cloudy veil. It was exactly what he was hoping to find one day as he conducted his extensive survey of the nebulae. Novae had been seen before in Andromeda; that wasn't startling. But Hubble was sure that additional sightings would help reveal Andromeda's secret. “Nova suspected,” Hubble neatly wrote in black ink in his logbook for Plate H 331 H. After photographing Andromeda for forty minutes, he went on to observe another nebula, a barred spiral, before ending his run.
The very next night Hubble returned to the 100-inch to follow up. This time the atmosphere was better—clear and steady, at least for a while. When the sky was at its best, he aimed the telescope at Andromeda and again saw the new pinpoint of light. “Confirms nova suspected on H 331 H,” Hubble noted in his logbook.
Everything, though, cannot be readily seen through the telescopic eyepiece or by a quick peek at a newly developed photograph. Plate H 335 H, the forty-five-minute exposure taken on October 5 to verify the nova, was analyzed in more detail later, back in Hubble's Pasadena office. There he confirmed not just one but rather three new pinpoints of light within Andromeda. He figured he was seeing two additional novae and wrote “N” beside each one on his plate to mark their location.
From his earlier work on the Magellanic cloud-like NGC 6822, Hubble knew that he had to make sure his newly spied objects were truly novae and not some other phenomenon. For a further check, he turned to the massive collection of plates archived in a quakeproof vault at the observatory headquarters. He began perusing previous photos of the Andromeda nebula, taken by observatory astronomers as far back as 1909. By comparing his latest photographic plate with those from the past, he could easily see that two of his spots of light were indeed novae—never-before-seen stellar flares. But one spot, the one farthest out from the center of the nebula, had been around before. Going from plate to plate, Hubble could see that this tiny dot of light was brightening and dimming over time. It was not a nova at all, but instead some kind of variable star. At this point Hubble went back to plate H 335 H, crossed out the N beside this particular dot, and beneath it wrote “VAR!” instead. His exclamation point emphasized the significance of this discovery: He had struck celestial gold. Once he had this stellar nugget in his hand, he didn't let it go.
Hubble more carefully tracked the ups and down of his variable's luminosity from the archival photographic plates. He also continued his survey of the heavens, making sure to check back on Andromeda again and again, as this was the time of year when Andromeda was in full view. He found more novae and another variable. He kept track of his finds, numbering each nova and variable and marking their positions in the spiral with a tiny red dot or circle on photos of Andromeda.
Three nights in February 1924 proved especially crucial. Over the fifth, sixth, and seventh of that month he directly observed his first variable in Andromeda brightening by more than a magnitude, doubling its luminosity, a tremendous break. From the data he had on hand he could now sketch a reliable light curve. The variable star went through its complete cycle—from bright to dim and back to bright again—in a matter of 31.415 days. From the length of this period and the shape of the curve (sharp rise and slow decline), Hubble now comprehended that he had captured that elusive and rare celestial beast—a Cepheid variable, a star seven thousand times brighter than our Sun. But it appeared so dim—the barest smudge on his photographic plate—that Hubble knew it had to reside at a great distance. It was on average more than one hundred thousand times dimmer than the faintest stars visible to the unaided eye.
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 light-years (“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 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.” The 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.”
In Hubble's absence, Russell stepped in and read the paper to the assembled conferees on the snowy morning of January 1, 1925. Hubble relayed that he had found twelve Cepheids in Andromeda and twenty-two in Triangulum, their telltale blinks indicating a distance for each of nearly a million light-years, confirming what others had gleaned with shakier methods. More than that, the 100-inch telescope had allowed Hubble to resolve the outer regions of the two nebulae into vast collections of stars. Astronomers could now be certain that the spirals were not simple nebulosities, not just clouds of dust and gas. At the end of his paper, Hubble hinted at more results to come, having by then sighted variable stars in M81, M101, and NGC 2403, some of the most commanding spirals in the celestial sky.
Astronomers in the audience could practically feel the universe changing as they listened to Russell—except for one. Curtis, who was briefly at the Washington meeting, took the announcement in stride. “As you know,” he wrote a former Lick colleague the next day, “I have always believed that the spirals are island universes, and Hubble's recent results appear to clinch this, though I myself did not need the confirmation.” You can almost hear him yawn between the lines.
Soon after Russell's presentation, the American Astronomical Society Council sent in its petition to the AAAS, nominating Hubble's paper (one of seventeen hundred presented at the conference that year) for the coveted prize. “Dr. Hubble,” the council stated, “has found that the outer parts of the two most conspicuous nebulae, in Andromeda and in Triangular [sic], are resolved upon his best photographs into ‘dense swarms of actual stars.’ This has been suspected as a possibility for a century, but has never previously been unequivocally proved… This paper is the product of a young man of conspicuous and recognized ability in a field which he has made peculiarly his own. It opens up depths of space previously inaccessible to investigation and gives promise of still greater advances in the near future. Meanwhile, it has already expanded one hundred fold the known volume of the material universe and has apparently settled the long-mooted question of the nature of the spirals, showing them to be gigantic agglomerations of stars almost comparable in extent with our own galaxy.”
Although the great distances to the two nebulae flagrantly disagreed with van Maanen's data, most astronomers quickly rallied around Hubble's figures. The Cepheids were fast becoming the gold standard for measuring distances to the more remote starry regions of the universe. Nearly everyone came to assume that van Maanen was mistaken. “The great distances recently derived have made rapid rotation impossible,” said Harvard astronomer Willem Luyten, “and the quick internal motion measured some years ago is now universally regarded as an optical illusion.” James Jeans confirmed Hubble's distance results with an alternate technique and wrote Hubble that “van Maanen's measurements have to go.” The long and convoluted squabble on the nature of the spiral nebulae—centuries of debate—was finally over. The spirals were not adjuncts of the Milky Way at all but instead galaxies in their own right. The universe officially became far larger—and far more intriguing.
Edwin Hubble and James Jeans at the 100-inch telescope
(Reproduced by permission of the Huntington Library,
San Marino, California)
Russell's instincts, it turns out, were very good. Hubble in the end won the AAAS award for extending the boundaries of the known universe. He was informed by telegram on February 7, but the amount he received was cut by half. The young astronomer was told he was sharing the award with another scientist. Parasitologist Lemuel Cleveland of the School of Hygiene and Public Health at Johns Hopkins was also honored for his study of microscopic protozoa found inside the digestive tracts of termites. He showed that the tiny organisms were essential for a termite to digest cellulose. “To scientists,” reported the Los Angeles Times, “the infinite and the infinitesimal are merely relative terms, alike in importance.” The Hubbles had just bought an acre lot in San Marino to build their charming new home (designed in the style of a small Tuscan villa) and used the funds to help pay for pruning the live oaks on their property and clearing out the deadwood—a needed renovation for appreciating the fine view of Mount Wilson and the San Gabriel Mountains from their backyard. There at his home Hubble began collecting old books, specifically on the Renaissance years, when the old Aristotelian representations of the universe were crumbling. “If an old scrap of paper, published within the sacred period, contains the names of Copernicus, or Tycho Brahe, or Kepler, or Galileo, [Hubble] hankers after that paper more than a debutante hankers after orchids,” wrote a local reporter. It was an apt hobby for the man who erected his own new-and-improved model of the cosmos.
Why was Hubble able to accomplish this magnificent feat while others were not? In actuality, there were several opportunities to resolve the island-universe controversy earlier. The Cepheids could have been hunted down and observed without the 100-inch telescope. It's somewhat surprising that more astronomers didn't sense the celestial riches to be found in distant space, just ready for mining. Having access to the world's largest telescope was not the essential key to Hubble's success (although it certainly helped). Mount Wilson's 60-inch telescope, erected in 1908, could have done the job just fine. Even the Crossley telescope at Lick had an outside chance. But few were interested in this area of endeavor, and those who did had bad luck. For example, the first person to find a variable star in a spiral nebula was not Hubble at all, but rather Wellesley College astronomer John Duncan. In 1920, while using Mount Wilson's 60-and 100-inch telescopes to search for novae, Duncan found three variable stars within the Triangulum nebula, M33. Over the next two years, he took additional images and also checked other photographs of the region made at the Yerkes, Lick, Lowell, and Mount Wilson observatories from 1899 to 1922 in an attempt to track the variables' periods but was unsuccessful. The data were simply too sparse at the time. And in his report of the find, Duncan refrained from directly linking the variables to the nebula. If he had followed up, the prize would have been his: The faintest variable he saw was later found to be a Cepheid and could have been used to peg the nebula's distance. Why didn't Shapley himself, the world's Cepheid guru, search for these special stars in the spiral nebulae and garner one of the choicest discoveries in astronomical history? It seemed like it would have been a natural progression for him. But around 1910 his colleague at Mount Wilson, George Ritchey, had photographed thousands of “soft star-like condensations” in Andromeda and other spirals, which he figured were nebulous stars in the process of formation. This interpretation suggested that a spiral nebula was simply the early stage of a modest star cluster forming, rather than an entire galaxy. Shapley admitted he was deeply influenced by Ritchey's images at the time, as were many others. Years later, in his autobiography, Shapley also suggested that strict divisions were in place in Mount Wilson as well: Shapley was relegated to the globular clusters and Hubble to the spiraling nebulae. Moreover, his taking the Harvard Observatory directorship distanced him from the thick of the battle.
But in truth, Shapley had basically taken off his scientist's hat and become too wedded to his vision of the Milky Way as the defining feature of the universe. He ignored conflicting data longer than he should have, which kept him from extending his work to the spiral nebulae and beating Hubble to the punch. He saw no reason to search for Cepheids in spiral nebulae, since he had already convinced himself that they were not separate galaxies. He was enormously attached to his Big Galaxy concept and had built his career on it. It's not surprising that he would be reluctant to let his vision be supplanted.
Shapley, in the end, was simply human. He didn't view his ignoring the early doubts about van Maanen's work as a scientific lapse but rather a personal one. “I faithfully went along with my friend van Maanen and he was wrong on the…motions of galaxies… [People] wonder why Shapley made this blunder. The reason he made it was that van Maanen was his friend and he believed in friends!” declared Shapley (oddly in the third person). He was also a man who was far too confident for his own good, if a popular tale often recounted at Mount Wilson is true. Around 1920 Shapley allegedly asked staffer Milton Humason to examine with the Blink some photographic plates of the Andromeda nebula Shapley had taken over the preceding three years. After comparing the plates for several weeks, Humason came to notice what appeared to be some variable stars in the nebula, possibly the same Cepheids that Hubble found a few years later. Humason, still in training, used a pen to mark off the suspects on the glass plates and went back to Shapley to show him the results. Shapley, not impressed, patiently explained to Humason why his spots couldn't possibly be Cepheids. Shapley was so certain of his position that he proceeded to take a handkerchief out of his pocket and rub out the marks, wiping the plates clean—not to mention wiping out his chances for further astronomical glory. While Shapley was waiting in 1920 to hear from Harvard about the directorship, he confided to one of his former Missouri professors, Oliver D. Kellogg, that he was frustrated by the university's indecision, since it disturbed his ability to prepare his research program for the next few years. Belying what he later said about there being “strict divisions” at Mount Wilson, Shapley noted that “spiral nebulae” were on his agenda and that “cosmogony” would be his future field. Had Shapley not gone to Harvard and instead stayed at Mount Wilson, he would surely have continued to look for novae in Andromeda, the purpose of his photographic survey, and perhaps come to recognize the Cepheids after all. He might have scooped Hubble. That he didn't only added to the ongoing rivalry between the two Missouri men.
Even decades later, when writing his memoir in the late 1960s, Shapley couldn't let go of the beefs with his rival. “The work that Hubble did on galaxies was very largely using my methods,” he recalled sulkingly. “He never acknowledged my priority, but there are people like that.” But then he grudgingly conceded that Hubble had “made himself very famous, and properly so. He was an excellent observer, better than I.” Hubble was patient.
It was that patience that enabled Hubble to methodically carry out the measurements that eluded earlier astronomers. Others had approached the nebular mystery yet gathered only tantalizing and incomplete hints; Hubble performed the painstaking tasks that closed the deal. That meant searching for stars and novae at the very limit of his telescope's resolving power and using them to measure a distance. Curtis had removed himself from big telescope access; Shapley refused to consider that spirals could be huge stellar systems. Only Hubble pursued the question with dogged effort and even he had been looking for novae at first, not Cepheids in particular. Luck certainly played a small role, but as Louis Pasteur once put it, “In the fields of observation, chance favors only the prepared mind.”
Once the news was out, reporters couldn't get enough of the tall and broad-shouldered Major Hubble, as they often addressed him. He was turning into an accomplished popular communicator. “There is just not one universe,” Hubble told a local journalist about his discovery. “Countless whole worlds, each of them a mighty universe, are strewn all over the sky. Like the proverbial grains of sand on the beach are the universes, each of them peopled with billions of stars or solar systems. Science has already taken a census of nearly ten million galactic systems or individual universes of stars.”
Newspapers vied with one another to come up with the catchiest headline to describe the new cosmic order: “Ten Million Worlds in Sky Census,” “Gigantic Telescope Finds New Wonders in Heavens,” “Mount Wilson Observers Now Study Stars on Newly Found Horizons,” “Distances of Star Systems So Great 18 Ciphers Are Needed to Express Them in Miles,” “Light Registered on Photographic Plates Started Million Years Ago.” A London magazine ranked Hubble's achievement “with the greatest in the history of astronomy. Columbus discovered half of a known world, but Dr. Hubble discovered a host of new universes.” Another droll scribe said Hubble had found “more systems of stars than there are hairs in the whiskers of Santa Claus.”
Hubble had even gained enough fame to be joked about. “Professor Edwin Hubble announces that he has found another universe. Some people never seem to know when they have enough,” said the caption of a Nation cartoon.
At lectures Hubble drew record crowds. At one Los Angeles talk, the room was filled to capacity while hundreds more jammed the doorways and windows to listen in. An additional five hundred were turned away. “Astronomy, as a matter of popular interest,” reported the Los Angeles Examiner, “joined rank with football and prize fights” that night. When standing on the balcony of Mount Wilson's observatory laboratory one night with a reporter, the two gazing at the lights of the towns below, Hubble was asked how he carried out his work. “It is like looking at those lights,” he replied, “and from them alone trying to tell what manner of people live there.”
From that point on, the nebulae beyond the Milky Way became the sole subject of Hubble's professional life; he scarcely studied anything else—although he did by chance discover “Comet Hubble” in August 1937 while photographing a spiral nebula. When a friend asked him to name Jupiter's moons one day, he could recall three or four but no more. “I am commuting to a spiral nebula, and I forget the suburban stations,” he responded apologetically.
Astronomers had been proceeding outward into space and time on stepping-stones. The first stops were at the globular clusters, followed by a giant leap to the spiral nebulae. The conventional understanding of the universe was changing and very swiftly. Just a few years after Hubble confirmed the existence of other galaxies, Jeans wrote that “astronomy is a science in which exact truth is ever stranger than fiction, in which the imagination ever labours panting and breathless behind the reality, and about which one could hardly be prosaic if one tried.”
The English poet Edith Sitwell, upon a visit to Hubble's home, was ushered into the study, where she was shown slides depicting the myriad galaxies that cannot be seen with the naked eye, galaxies millions of light-years away. “How terrifying!” exclaimed Sitwell, to which Hubble replied, “Only at first. When you are not used to them. Afterwards, they give one comfort. For then you know that there is nothing to worry about—nothing at all!”
Except, perhaps, what to call them. There was much confusion at first on how to identify the newfound stellar systems. Everyone seemed to have a pet name, including anagalactic nebulae, nongalactic nebulae, star clouds, cosmic nebulae, and island universes. Hubble preferred “extragalactic nebulae,” using it in his lectures and publications rather than the term galaxies, the name regularly employed by Shapley at Harvard. “I want to get away from both the words universe and nebula in reference to these objects, as frequently as possible,” argued Shapley. “Therefore I am adopting…the term galaxy, and from that the term inter-galactic space follows naturally.”
Edwin Hubble in his office with a picture of the Andromeda galaxy
(Hale Observatories, courtesy of AIP Emilio Segrè Visual Archives)
But Hubble didn't see any pressing need to abolish the “venerable precedent” of preserving the word galaxy for the Milky Way alone. The term originated from galakt, the Greek word for milk. As a purist, Hubble chose the Oxford English Dictionary as his final arbiter. At the time its pages said the term galaxy was “chiefly applied to a brilliant assemblage…of beautiful women or distinguished persons.” “The term nebulae offers the values of tradition; the term galaxies, the glamour of romance,” concluded Hubble. According to historian Robert Smith, which code word an American astronomer used quickly pinpointed whether they came from the East or West Coast. The intense Hubble-Shapley rivalry had extended into a surprising new sphere. It wasn't until Hubble's death in 1953 that the term galaxy became the universally accepted moniker.
Van Maanen was obviously panicky once Hubble's findings were officially out. He soon wrote Shapley asking if there was a list somewhere in the literature of every observation of a nova. “I want to compare them with the novae in spirals,” he said. “After Hubble's discovery of Cepheids I have been playing again with my motions and how I look at the measures.” He was clearly baffled. “I cannot find a flaw in [my measurements of] M33, for which I have the best material. They seem to be as consistent as possibly can be.” He understood that there were two sets of observations in circulation—his and Hubble's—that arrived at “radically different conclusions.” He planned to take more plates for a reassessment.
But Shapley by now had completely switched sides and in response at last lowered the boom on his good friend. “I am completely at a loss to know what to believe concerning those angular motions; but there seems to be no way of doubting the Cepheids, providing Hubble's period-luminosity curves are as definite as we hear they are,” he replied. When van Maanen a few years later again tried to defend his spiral work to Shapley, the Harvard Observatory director replied that he didn't “know what to think of your confounded spirals… There is little chance that we can get the universe out of this mess.” He avoided the topic with van Maanen from that point on.
Considering himself a gentleman at heart, Hubble didn't openly argue with van Maanen either, and hardly anyone else in the astronomical community appeared particularly concerned. But behind closed doors, it was another matter altogether. Personally Hubble felt that van Maanen's paradoxical findings lingered as a stubborn stain on his great accomplishment, a blemish that tarnished his otherwise sterling reputation. In her memoirs, Grace Hubble cheerily declared that the van Maanen episode hardly affected her husband at all, but she told others privately that “van Maanen's contradiction disturbed her husband so greatly from the late 1920s into the 1930s that he sometimes came home from the office and lay on his bed until his anguish abated.” Hubble had been aiming a critical eye at van Maanen's findings for quite a while and had begun preparing a series of private manuscripts, even before he announced that the Milky Way was not the only galaxy in the universe. His sole objective: to find out where van Maanen had gone wrong.
For several years, Hubble kept his doubts to himself and his covert manuscripts stashed away in his office drawer. It appeared that the Hubble-van Maanen conflict would just wither away, likely remembered, if at all, as a minor episode in the history of the island-universe debate. That would have been the case, except that van Maanen was perversely unwilling to admit defeat. He began remeasuring some of his spirals and in Mount Wilson's 1931 annual report it was announced he had found in M101 “a decided internal motion in the same direction as was found in his original measures of this nebula.” With this surprising new strike, the battle was reignited. “They asked me to give him time. Well, I gave him time, I gave him ten years,” responded Hubble to the latest assault. Now faced with van Maanen's implicit slap in the face, the former boxer put his gloves back on and rushed headlong into one of Mount Wilson's most fabled tempests. It had already been simmering in regard to telescope use. Van Maanen was sure that Hubble had been heading up a cabal to deny him a fair share of time on the 100-inch. That's when van Maanen slapped his sign on the front of the Blink, warning others not to use the machine without his permission.
The skirmish even extended into the dining room atop Mount Wilson. Seating arrangements for lunch at the Monastery followed a strict protocol: The observer scheduled to use the 100-inch telescope always sat at the head of the table, the 60-inch-telescope observer to his right, and the solar-tower observer to the left. Down the table it went in order of diminishing telescopic prominence. But one day Hubble arrived on the mountain for a run on the 60-inch and slyly switched the napkin rings, each specially marked with a staff member's name. When the dinner bell rang van Maanen, then working on the 100-inch, proceeded into the dining room and found himself placed lower down, with Hubble victoriously positioned at the table's prime spot. It was the ultimate insult one could receive on the mountain.
Drawing on his former legal training, “Hubble skillfully employed trial tactics to attain a favorable verdict from the court of science,” contends Hubble scholar Norriss Hetherington. First Hubble got his observing partner, Milton Humason, to photograph the Triangulum spiral over two nights in September 1931. He then compared this latest image with a photograph of the same galaxy taken in 1910. This was followed by new photographs of other prominent spirals long studied by van Maanen, such as the Whirlpool and Pinwheel galaxies. Hubble spent hours and hours comparing the old and new plates—picking out comparison stars, just as van Maanen did, and looking for telltale signs of rotation over the years. In the end, he concluded that “no evidence of motion” could be found. In a strategic coup de grâce, Hubble commandeered Seth Nicholson, who had assisted van Maanen in his earlier measurements, to examine the plates as well. This time Nicholson saw no changes whatsoever, at least within the range of probable error. The clever prosecutor had gotten a key witness to reverse his opinion on the courtroom stand. It appeared that van Maanen had made a personal error in regard to spiral rotation, simply finding what he expected to find.
Hubble wrote up his findings for publication, but his bosses were not pleased at all with his first draft. Breaking all the rules of dispassionate scientific discourse, Hubble's grudge with van Maanen was starkly visible upon the page. “Its language was intemperate in many places and the attitude of animosity was marked. He objected to any material change in the wording and a deadlock seemed to be indicated,” confided Mount Wilson director Walter Adams to the president of the Carnegie Institution of Washington, John Merriam. Like the preparations for a treaty between two warring nations, resolution involved delicate diplomacy, although in this case the principals involved worked at the same place. Frederick Seares, who served as the editor for papers written at Mount Wilson, did not want the battle to go public. If he solely published Hubble's criticism of van Maanen's work, it would be as if he were taking sides. A serious man known for his courtly manner, Seares wanted to maintain a certain decorum. Otherwise, morale at the observatory could plummet.
Seares decided that it would be best to prepare a joint statement, to be published under all the names of the people involved in reviewing the case—Hubble, van Maanen, Nicholson, as well as Walter Baade, a new staff member who had also assisted. All the parties agreed to this cooperative effort—except for Hubble, who opposed it violently. He declared “no compromise, no compromise” as the truce was worked on, insisting on no watering down of his views of the evidence. Hubble was sure he was right and van Maanen wrong. Adams was appalled by this response. “I do not feel that Hubble's attitude in this matter was in any way justified… This is not the first case in which Hubble has seriously injured himself in the opinion of scientific men by the intemperate and intolerant way in which he has expressed himself,” Adams reported to Merriam. Seares was so exasperated by Hubble's pigheaded attitude that he was almost ready to tell him, “Print what you like, but print it elsewhere.”
It was a moment when Hubble's discretion and judgment completely failed him. Although all the facts were assuredly in his favor, his obstinate manner in this episode deeply hurt his relations at the observatory. “The attitude of van Maanen in the matter was much superior to that of Hubble,” concluded Adams. “Hubble, who had much the better of the general weight of evidence, showed a distinctly ungenerous and almost vindictive spirit.” Hubble had become the big man in astronomy and could tolerate no lesser colleagues. He had begun to blithely ignore his duties on international committees when the chores didn't suit his schedule and was also less willing to join cooperative projects at the observatory, acting more as an individual driven by personal ambition than as a member of a larger staff. Adams lamented that he “recognized this curious ‘blind spot’ in almost every important dealing” he had with Hubble.
Hubble's increasing worldwide fame was inflating his ego, already outsized as it was. Never great pals with his astronomical colleagues, he widened the breach with his boorish behavior. He broke promises, ignored vital correspondence, took more travel than the norm (with pay), and failed to show up at meetings that he said he would attend. Adams's remarks were a reflection of the growing irritation at Mount Wilson with this loutish conduct, but it was hard to rein in the observatory's most famous staff member. Hubble was, after all, the discoverer of the modern universe. Hubble's family, too, was deeply affected by his self-centered concerns. When his mother died in 1934, Hubble did not try to return from England, where he was then traveling, once he was cabled the news. By then he hardly interacted with his family or helped them much financially. Never once did Grace meet her in-laws. “Great men have to go their own way,” his youngest sister, Betsy, said with resigned acceptance many years later. “There is bound to be some trampling. We never minded… With Edwin, it was out of sight, out of mind. When he was with you, you were the only person in the world, but if you were away, he would forget you. His head was in the stars.”
In the end, Hubble and van Maanen grudgingly arrived at a gentleman's agreement. After much discussion with Adams (and a lot of arm-twisting), Hubble at last consented to publish a brief statement on his own, which was to be accompanied by a paper by van Maanen in which he acknowledged the existence of possible errors in his research. Hubble's brief note came out in the May 1935 issue of the Astrophysical Journal. It was a mere four paragraphs plus a table, summarizing his measurements of M81, M51, M33, and M101. All arrived at the same conclusion: no “rotations of the order expected.” In an orchestrated move, the Astrophysical Journal had van Maanen's paper immediately follow. After including new plates taken with the 100-inch telescope in his reevaluation, van Maanen conceded that his measured motions were now smaller. “[My] results, together with the measures of Hubble, Baade, and Nicholson…make it desirable to view the motions with reserve,” he stated. Van Maanen promised a “most searching investigation in the future,” but as the years progressed he never followed up.
The one nagging discrepancy keeping Hubble from his full triumph—the unquestioned discovery that the spiral nebulae were truly separate galaxies—was at last resolved. In print, the two adversaries symbolically shook hands and went their separate ways. But, from that point on, whenever the two passed each other in the observatory hallways, they exchanged not a word.