The Day We Found the Universe

by Marcia Bartusiak

  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 gala
xies—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.

  Using the 100-Inch Telescope

  the Way It Should Be Used

  While it appeared that Hubble had clinched astronomy's brass ring, solving the mystery of the spiral nebulae once and for all, a nagging problem remained: how to explain the galaxies' astounding velocities, first spotted by Vesto Slipher in the 1910s. Why were the spiraling disks speeding away from us? They “shun us like a plague,” exclaimed Eddington. It was a puzzle whose solution would prove to be even more momentous than Hubble's settling the island-universe controversy.

  Hubble began to focus his full attention on the cosmic exodus in 1928. That summer the International Astronomical Union was holding its triennial general assembly in the picturesque city of Leiden, set along the Old Rhine in southern Holland. With fine weather to entice them, more than three hundred delegates attended the gathering, where they were entertained with boat excursions down the city's noted canals, gliding past scenery painted by Rembrandt three centuries earlier. It was the height of the Roaring Twenties, and Europe was overflowing with tourists. “Most of the Americans appear to be over here this summer, always on the run scooping up culture with both hands, buying walking sticks and spats, post cards,” noted Lowell astronomer Carl Lampland, who attended the meeting.

  Hubble had been appointed acting chairman of the IAU Nebulae Commission, and in and around its July session, he took the opportunity to sit down with Willem de Sitter to discuss relativity and its application to cosmology. Hubble was undoubtedly familiar with (though hardly an expert on) the Einstein and de Sitter solutions to the universe's structure. At the very end of his magisterial 1926 paper “Extra-Galactic Nebulae,” Hubble had included a brief section titled “The Finite Universe of General Relativity,” in which he mentions both of them. Moreover, the following year at Hubble's direction, Milton Humason had remeasured the redshifts of two nearby galaxies. In his brief report, likely ghostwritten by Hubble, Humason specially noted that the galaxy speeds computed from those redshifts were unusually low, “consistent with the marked tendency already observed” for the closest galaxies to have the smaller pace.

  Hubble was thus certainly aware of the general trend of galaxy velocities outward, but at Leiden he seemed to have finally grasped the tremendous hubbub the galaxy redshifts were generating among cosmologists and received some further lessons from one of the world's few experts on general relativity. Eager to have his model of the universe put to the test, de Sitter encouraged Hubble at this time to extend the red-shift measurements of the spiral nebulae begun by Slipher at the Lowell Observatory. With only a puny 24-inch refractor with which to work, Slipher had essentially come to the end of his search. He had been able to acquire the redshifts of the brightest spiral nebulae, over forty of them, but trying to obtain a reading from ever fainter and smaller galaxies was impossible. Slipher had exhausted the power of his telescope and could simply not gather enough photons. “The Flagstaff assault on these objects stopped just short of some great excitement,” Shapley later pointed out. Most figured that to reliably establish whether a galaxy's redshift was related to its distance in a predictable way would require a far bigger telescope, like the 100-inch reflector available to Hubble at Mount Wilson. It was the perfect match of problem to instrument. De Sitter knew this, and Hubble was obviously convinced as well.

  Upon returning to California, Hubble immediately made this pursuit his top observational priority. Having conquered the mystery of the spiral nebulae, he was now commencing his next great challenge—to see if there truly was a definitive trend to the redshifts of the galaxies as they rushed headlong into distant space. It was at this time that Hubble forged his industrious partnership with Humason, each taking on a specific task to get the overall job done. While Hubble searched for Cepheid variables to determine the distances to a sample of galaxies, his colleague focused on getting the redshift data to figure out the galaxies' velocities (if that indeed was how the redshifts were to be interpreted). Hubble's plan was to put these two pieces of information together and determine if there was a law—a specific formula—that linked a galaxy's distance to its measured redshift.

  Humason was not too happy at first upon hearing of his new assignment. Hubble had come home from Leiden quite excited and quickly suggested to Humason that he try to obtain a galaxy redshift that was not yet known. But the prism on the 100-inch spectrograph had started to yellow, and the photographic plates then on hand were considerably slow-acting for such work. Humason knew it would take several nights to get a decent spectrum. “I didn't feel much enthusiasm about these long exposures,” he later recalled. “But [Hubble] kept at me and encouraged me.” Hubble was after fainter and fainter objects, the ones too distant for Slipher to have studied with his smaller telescope, and some were low on the southern sky. “To get these,” said Humason, “you had to climb onto the 100 inch and sit on the iron frame during the long winter nights, which was extremely cold and uncomfortable.” For hours on end, through the freezing night, he would have to keep his guide star on the center of the cross wires, to make sure his image remained sure and steady. “The eye-strain, the monotony, the constant awareness—it was a test of endurance,” he said. But Humason's unusual entrée into astronomy offered him superb preparation for this arduous undertaking. He was accustomed to hard work.

  Born in Minnesota in 1891, Humason as a boy moved to the West Coast with his family and one summer as a teenager enjoyed a camping holiday on Mount Wilson. He fell in love with the mountain and soon dropped out of grammar school to work as a bellboy and handyman at the newly opened Mount Wilson hotel, a popular resort spot for local residents. He washed dishes, corralled the horses, and shingled the cottages. Once the 60-inch telescope was under construction, he drove the mule trains that took the equipment, piece by piece, up the rugged path to the top of the peak. When a mountain lion was found feasting on a prized goat in the area, Humason tracked the animal down and shot him between the eyes with a .22-caliber rifle. Several years after Humason married the daughter of the observatory's chief engineer, his father-in-law arranged for him to work as the observatory's janitor. Gradually he was allowed to help the astronomers as a night assistant and over time won their respect and trust in making observations on his own, despite his eighth-grade education and lack of formal training in astronomy. Seth Nicholson took the young man under his wing and taught him some mathematics; Shapley mentored him as well. With his round face and round eyeglasses, the quiet and self-effacing Humason came to look like an academic. In 1920 he was promoted to a staff position in the photography department and two years later moved up to assistant astronomer. Known for his patience and conscientious attention to detail, he became especially skilled at taking long photographic or spectroscopic exposures of the most faint celestial objects. A likable fellow and an inveterate gambler, he relieved the pent-up tension from this grinding work by playing poker with the other night assistants and shop workers. If his schedule allowed, he'd catch the late-afternoon horse races at the nearby Santa Anita racetrack, taking any astronomer who wanted to go with him.

  Over time, Humason was even put in charge of arranging telescope time. Sharing Hubble's strong loyalty for the Republican Party, Humason tried to get as many Democrat observers as possible on the mountain, away from the polls, on election days. Solar astronomer Nicholson, a staunch Democrat, evened the score by making sure only Republicans were scheduled on the solar telescopes at the same time. Hubble, whose status could never be threatened by Humason's humbler origins, got along fine with his devoted junior partner.

  Milton Humason at Mount Wilson

  (Courtesy of AIP Emilio Segrè Visual Archives)

  • • •

  By 1929 Hubble had determined the distances to twenty-four galaxies (including the Small and Large Magellanic Clo
uds), the most remote then judged to reside some 6 million light-years away. He accomplished this feat by establishing a ladder of measurements, one rung leading to the next. First he used Cepheid variables, his most reliable yardstick, to directly obtain the distances to six relatively nearby galaxies; then he judged the magnitude of the brightest stars in those galaxies. Figuring such stars were similarly bright in other, more distant galaxies, he proceeded to use them as standard candles. He sought out these radiant stars in more far-off galaxies—fourteen in all—and estimated each galaxy's distance based on the stars' apparent luminosities. Then, taking all twenty of these galaxies into account (the first six and the subsequent fourteen), he estimated the brightness for an average galaxy and used that value for judging the distance to four more remote galaxies. Hubble's moving outward like this, rung by rung, was similar to Shapley's strategy for his globular cluster distance measurements, but here Hubble was making an even braver leap into distant space.

  Hubble then paired each galaxy's distance with its measured velocity to see if there was a connection, some sort of organized flow in which the galaxies flew outward into the depths of space. Humason by then had redone a number of the redshifts, but when Hubble prepared his first paper on the findings (“A Relation Between Distance and Radial Velocity Among Extra-Galactic Nebulae”), he primarily used Slipher's original measurements.

  Hubble was more vigilant than usual in preparing this landmark 1929 publication, chiefly because of the checkered history of the subject. An earlier and rather clumsy attempt by the Polish-American mathematical physicist Ludwik Silberstein to find a relationship between a galaxy's distance and its redshift had been met with derision, especially by noted astronomers Knut Lundmark and Gustaf Ström-berg, who was Hubble's colleague at Mount Wilson. Silberstein had lumped globular clusters in with spiral nebulae, which led to a meaningless result. He was ridiculed for both his inept analysis and leaving out data that went against his prediction, which tainted everyone's outlook on the problem. To make sure this didn't happen to him, Hubble shrewdly sought out the advice of Silberstein's two harshest critics and specifically highlighted their contributions in his paper. “Mr. Strömberg has very kindly checked the general order of these values… Solutions of this sort have been published by Lundmark,” he wrote fawningly. Hubble knew he was dealing with a controversial finding, so he was taking every precaution. He was wooing potential enemies to his side. He didn't even like Lundmark, having earlier accused the man of plagiarizing his system for classifying the galaxies, and the point he had Strömberg verify was so simple it scarcely needed checking. As it was, Hubble held up publication of his data to make sure he had nailed down every argument, as well as gathered data on even fainter galaxies so he and Humason could quickly publish a follow-up and prevent others from jumping into what Hubble considered his field. He was being both careful and cunning; he was not just introducing an idea but selling it hard. Hubble knew he had to make an air tight case in order to convince his more skeptical colleagues. “There is more to the advance of science than new observations and new theories,” historian Norriss Hetherington has noted. “Ultimately, people must be persuaded.”