The Day We Found the Universe - Marcia Bartusiak (2009)
Chapter 12. On the Brink of a Big Discovery-or Maybe a Big Paradox
George Ellery Hale could never rest on his laurels. He was a man of endless enthusiasms. British theorist James Jeans said he possessed “a driving power which was given no rest until it had brought his plans and schemes to fruition.” After being awarded nearly every major scientific honor before the age of forty—from election to the National Academy of Sciences in the United States to the gold medal of Great Britain's Royal Astronomical Society—Hale craved additional triumphs. “He has reached a place where scientific work and honors are not enough,” George Ritchey suggested darkly after a conflict with Hale. “He must have vast poweralso; power to dictate the welfare, the making or unmaking, the positions even, of scientific men both in the observatory and outside of it—as far as his influences can possibly reach.”
Even before Mount Wilson's 60-inch telescope went into operation in 1908, Hale was thinking ahead to a new adventure. In the summer of 1906 he spent a weekend at the home of John Hooker, a wealthy Los Angeles businessman and a founder of the Southern California Academy of Sciences, and excitedly discussed his latest dream. Again, it was to be an even bigger telescope. Like a compulsive climber, Hale was always looking ahead to the next challenging mountain. He captivated Hooker, an amateur astronomer, with his description of a mirror one hundred inches in width that would gather nearly three times more light—the very lifeblood of astronomy—than the 60-inch. Hale and Ritchey followed up with a letter to Hooker, outlining the usefulness of such a large mirror, including the tens of thousands of nebulae that would likely be revealed, unlocking the secret of their mysterious nature.
Hale's charismatic personality, coupled with Ritchey's technical expertise, worked their magic. Within weeks Hooker, who had made his fortune in hardware, pledged the money to construct the mirror, even though no one (neither Hale nor Ritchey) knew at the time whether such a disk—four and a half tons of pristine glass—could even be cast, polished, or mounted. No glass that large had ever been made before. Hale's younger brother, Will, once called George the greatest gambler in the world. Ordering up a 100-inch mirror was his biggest bet ever. And he almost lost.
In December 1908, the giant glass arrived from France, where it had been manufactured, but as soon as the crate was unpacked at the observatory's headquarters on Santa Barbara Street in Pasadena, everyone could see the blank was seriously flawed—bubbles were dispersed throughout the disk and the glass incompletely fused. From the side it looked like a three-layered cake. Such defects jeopardized the mirror's ability to expand and contract uniformly and so maintain stable images as temperatures in the telescope dome changed over the nighttime hours. “We don't pay for this!” declared Hale.
A new disk was ordered, but the best candidate broke as it was cooling. With his funds exhausted, Hale decided to have the first disk ground and polished, despite its imperfections. Both Hooker and Ritchey opposed this decision with intense vehemence. To compound Hale's trials, Hooker grew increasingly jealous and antagonistic over Hale's friendship with Mrs. Hooker. Previously an ally, Hooker was now Hale's demoralizing opponent who balked at any new request. Faced with these multiple struggles, Hale snapped. Having inherited the high-strung and anxious temperament of his reclusive mother, he experienced the first of many nervous breakdowns that plagued him for the rest of his life, attacks that included horrendous nightmares and blinding headaches. His exuberance, once deemed inexhaustible, finally flamed out. In a poignant letter to Walter Adams, Hale's wife wrote that she now wished “that glass was in the bottom of the ocean.”
Hale's recurrent psychiatric episodes gave rise to the popular myth that he sometimes hallucinated during these breakdowns, literally seeing a little “elf” who would advise him on the conduct of his life. Helen Wright first recounted this tale in her noted biography of Hale, referring to the specter as Hale's “little man.” Expanding on Wright's account, other authors began to use the word elf. The legend is rooted in a letter that Hale wrote to a friend, in which he refers to a “little demon” plaguing him. Psychiatrist William Sheehan and astronomer Donald Osterbrock have made a good case that Hale only intended the demon to be taken figuratively, not literally, as the personification of his depressions, much the way Winston Churchill referred to his “black dog” when facing a bout of melancholy.
In the end, Ritchey carried out Hale's orders concerning the imperfect glass. Gritting his teeth and complaining all the way, he initiated the grinding and polishing of the flawed disk in 1910, an arduous task that was finally completed in 1916. Over those six years, the disk was figured to exquisite perfection. The curved glass surface was subsequently coated with silver, transforming it, at last, into a true astronomical mirror. All the while, the materials for the mounting and dome—every bolt, rivet, and steel beam—were laboriously transported up the mountain by truck. The nine-thousand-pound mirror went up on July 1, 1917. To Walter Adams “there was more publicity…than was desirable” during the event. The Pasadena police had received word that there might be trouble on the road. As a result, the bridges were guarded, and deputies accompanied the mirror to the top.
Full view of the 100-inch Hooker telescope on Mount Wilson
(AIP Emilio Segrè Visual Archives)
The Hooker telescope got its first trial exactly four months later in the midst of wartime, which resulted in the 100-inch's assuming the nickname of a famous German howitzer—the “Big Bertha” of light. Among those present on that first evening of November were Hale, Adams, and the British poet Alfred Noyes, then visiting Pasadena as a university lecturer. Hale, as director, was the first to climb up the black iron steps to the observing platform and look through the eyepiece at the chosen target, Jupiter, then brilliantly shining in the nighttime sky. To his horror, he saw six overlapping images of the planet rather than one. The mirror was somehow distorted. Was it a physical defect—the numerous bubbles indeed wrecking havoc, as Ritchey had warned—or merely a temporary warping, caused by workmen having left the dome open that day and heating the mirror? “To add to the gloom,” recalled Adams many years later, “news of the great disaster to the Italian army at Caporetto had just arrived, and I remember our sitting around on the floor of the dome speculating on whether Italy was completely out of the war.”
After waiting many excruciating hours for the mirror to cool in the nighttime air, trying but finding it impossible to sleep at one point back at the Monastery in their spare rooms, furnished only with bed and desk, first Hale then Adams returned to their cathedral of brass and steel at around 2:30 in the morning. Jupiter was now out of reach, so the night assistant swung the telescope around, its massive weight smoothly rotating with little friction because its bottom supports floated in tanks of mercury. The scope's new target was the bright blue star Vega. Hale once again peered into the eyepiece, and this time let out a joyful yell. The stellar image was exquisite. To everyone's relief, the mirror was not permanently damaged after all. Noyes later paid homage to this historic launch in his poem “Watchers of the Sky,” fairly bursting with metaphors inspired by the ongoing conflict in Europe:
High in heaven it shone,
Alive with all the thoughts, and hopes, and
Of man's adventurous mind.
Up there, I knew
The explorers of the sky, the pioneers
Of science, now made ready to attack
That darkness once again, and win new
… they hoped to crown the toil
Of twenty years, and turn upon the sky
The noblest weapon ever made by man.
War had delayed them. They had been
Designing darker weapons. But no gun
Could outrange this…
We creep to power by inches. Europe
Her “giant forty” still. Even to-night
Our own old sixty has its work to do;
And now our hundred-inch … I hardly
To think what this new muzzle of ours
But there were delays in the final preparation of the long and imposing telescopic “muzzle,” keeping it from full operation. “The truth is the war work here has completely stopped work on the 100-inch,” said Shapley to a colleague a year later. “Very little has been done with it… because of the war contracts in the shop.” Ritchey, for example, had to turn his attention to making lenses and prisms for such military items as binoculars, range finders, and periscopes. Once the United States officially entered the war on the side of the Allies, the Mount Wilson optical shop was quickly engaged in the effort.
Observations with the 100-inch did not really get going until the war was over and necessary personnel had finally returned from their military duties. Its first images—of the Moon, of nebulae—surpassed the promises that Hale had made to Hooker years earlier when a telescope of such a tremendous size was only a far-off aspiration. “In such an embarrassment of riches the chief difficulty is to withstand the temptation toward scattering of effort, and to form an observing programme directed toward the solution of crucial problems rather than the accumulation of vast stores of miscellaneous data,” said Hale.
High on Hale's list of priorities was determining once and for all the true size and nature of the universe, a job that Hubble took on with single-minded devotion.
Hubble's first night of observing on the mountain was on October 18, 1919. It took about an hour then to make the journey in a motorcar. Via the single stretch of telephone wire that ran to the top of Mount Wilson, the tollhouse keeper at the bottom alerted the observatory that a car was on its way, as the road was only wide enough for one car. Away from active observing for more than two years due to the war, Hubble initially freshened up his telescopic skills that autumn evening by using a 10-inch refractor called the Cooke lens. Though small, the telescope's wide-angle view enabled him to explore the sky quite handily. He took photos of the North America nebula (a diffuse cloud in the Cygnus constellation) and then directed the telescope to a nebulous loop of gas near the “belt” of Orion. He was getting back his sea legs, perusing familiar celestial territory, and mulling over his observing strategy for the coming months.
Seven days later Hubble tried out the 60-inch telescope. He took a photograph of the nebula NGC 1333, a rich star-forming region in Perseus, and later checked out how his beloved variable nebula, the one he first noticed as a graduate student at Yerkes, was doing. He noted that “striking changes have happened [in it] since 1916,” which was the last time he had taken a look.
Milton Humason, who became Hubble's devoted observing partner a decade later, first met the young astronomer during these opening runs at the observatory. “He was photographing at the Newtonian focus of the 60-inch, standing while he did his guiding,” recalled Humason, many years later. “His tall, vigorous figure, pipe in mouth, was clearly outlined against the sky. A brisk wind whipped his military trench coat around his body and occasionally blew sparks from his pipe into the darkness of the dome. ‘Seeing’ that night was rated extremely poor on our Mount Wilson scale, but when Hubble came back from developing his plate in the dark room he was jubilant. ‘If this is a sample of poor seeing conditions,’ he said, ‘I shall always be able to get usable photographs with the Mount Wilson instruments.’…He was sure of himself—of what he wanted to do, and of how to do it.”
Hubble got his first crack at the 100-inch telescope, what he called his “magic mirror,” on Christmas Eve. So immense was its light-gathering power that it could spot a candle from five thousand miles away. Hubble couldn't have asked for a more fitting holiday present; the atmosphere was almost at its best at the start of the evening, and it was also dark-sky time, a waxing crescent Moon having just set in the west. That was the prime opportunity to seek out the sky's faintest objects. He first photographed a hazy star near the Pleiades cluster. With a sixty-minute exposure, its nebulosity showed up fairly well. Afterward, he perused two more objects, a wispy planetary nebula and (again) his variable nebula NGC 2261. After Hubble aimed the giant scope at this target, he was able to obtain his best photo of the night. The variable nebula soon became his observational “mascot.”
At the end of his observing runs, if he was particularly eager to see his results, Hubble would go right to the dark room and develop his plates. Once dry, each was entered into his official Observing Book and put away in a numbered envelope. For marking his plates, Hubble used a special code: H 31 H, for example, stood for the hundred-inch telescope, plate number 31, taken by Hubble.
One of Hubble's first tasks on Mount Wilson was working with Frederick Seares to determine the color of “nebulous stars,” stars surrounded by diffuse clouds of luminous matter, such as the ones in the Pleiades. For that project he primarily worked with the 60-inch and got a paper published fairly quickly in the Astrophysical Journal. It was a warm-up session for Hubble's main purpose for being at Mount Wilson. He was going to finish what he started in his doctoral dissertation—figure out exactly what those faint spiral nebulae truly were. As he later told Slipher, he was committed to one issue and one issue only: “to determine the relation of nebulae to the universe.”
Henry Norris Russell was getting nervous about the spirals around this time. There were so many conflicting observations. The novae occasionally discovered within the spiraling clouds suggested they were far-off stellar systems. But then van Maanen was seeing them rotate, at an impossible rate if they were truly distant. “We are on the brink of a big discovery—or maybe a big paradox, until someone gets the right clue,” ventured Russell.
The dawn of the 1920s seemed the right time to break the impasse. With the war over, pent-up energies were fueling a plethora of inventions and clever ideas. Heber Curtis, now settled at the Allegheny Observatory, was particularly enamored of a newfangled entertainment medium. “I have just gone into the lecture room, pressed a button, and heard records by Galli-Curci and Rachmaninoff sent out by wireless telephony from East Pittsburgh, ten or twelve miles away,” he wrote his former Lick boss, Campbell. “As soon as the Westinghouse people start a broadcasting station at San Francisco, the mountain would enjoy one of these receiving and amplifying sets. They send out music, stock market reports, news bulletins, speeches, etc… We have one of their experimental models here on loan (hope they will eventually give it to us). It is called ‘the Aeriola Grand’; is the size of a small phonograph such as you have; is simplicity itself; has only one button and one dial,—no adjustments; about 75 feet of a single wire forms our aerial. Sermons on Sunday, with no collection possible!”
At Mount Wilson Albert A. Michelson and Francis Pease mounted a special instrument called an interferometer on the front of the 100-inch telescope and made the first successful measurement of a star's diameter. Betelgeuse, in the constellation Orion, was their target. They learned that if the red giant star on Orion's right shoulder were placed inside our solar system, it would engulf the planets out to Jupiter. And, of course, Harlow Shapley at this time was also on the mountain resizing the Milky Way.
Hubble's and Shapley's employment at Mount Wilson overlapped for about a year and a half, until Shapley moved to Harvard. Their relationship over that brief period, though, could hardly be called collegial. Both were from the heartland of America, but they might as well have been born continents apart. Hubble cultivated an air of sophistication and restraint around his colleagues. The cold and standoffish persona of his youth never went away. Hubble kept his distance and maintained a regal air. With his ever-present pipe, he would occasionally blow smoke rings out into the room or flip his lighted match and catch it, still alight, as it came down. As other astronomers put it, he was a “stuffed shirt,” who couldn't “write an inter-office memo without it sounding like the Preamble to the Constitution.” Shapley, on the other hand, retained his brassy and chummy country ways. Hubble's affectation for wearing jodhpurs, leather puttees, and a beret while observing or going around and saying “Bah Jove” was simply too much for Shapley to bear. An unadorned “Missourian tongue” was good enough for him. The fact that Shapley was a close friend of Adriaan van Maanen's made it even more difficult for the two midwesterners to cozy up. “Hubble disliked van Maanen from the time he himself arrived on Mount Wilson; he scorned him,” claimed Shapley years later. It may have been because van Maanen, more senior than Hubble, openly displayed his jealousy at having to share time on the 100-inch. To Shapley, though, “Hubble just didn't like people. He didn't associate with them, didn't care to work with them.”
Edwin Hubble wearing his knickers on Mount Wilson
(Courtesy of the Archives, California Institute of Technology)
Part of the coolness and tension between Hubble and Shapley had to do with their differing experiences during the war. Hubble had immediately volunteered, putting his professional life on hold and taking the risk that his research would be taken up by others. Shapley, who hated war, remained at Mount Wilson—the “conscientious slacker”—weakly suggesting that Hale convinced him to stay and taking on work that Hubble had hoped to tackle, such as the globular clusters. But, fortunately for Hubble, analyzing the mysterious nebulae was still a wide-open field when he returned from overseas. And once Shapley left for Harvard, Hubble at last had the chance to step out of the formidable shadow Shapley, then the golden boy of astronomy, had been casting on Mount Wilson.
Hubble first carried out an extensive study of the diffuse nebulae within the Milky Way, identifying the various types and describing the sources of their luminosity. But he also kept track of the “non-galactic nebulae” that he came across as he carried out this research. Hubble's sympathies certainly leaned toward the island-universe theory. When he was a graduate student at Yerkes he especially noted that the high velocities of the spiral nebulae “lend some color to the hypothesis that the spirals are stellar systems at distances to be measured often in millions of light-years.” But he became more circumspect once he became a staff member at Mount Wilson, at least in print. Caution became his byword. He emphasized in a 1922 Astrophysical Journal paper that the term non-galactic didn't mean the spirals were necessarily “outside our galaxy” but that these nebulae tended to avoid the galactic plane. At this point, Hubble's publications no longer contained grand references to island universes or other galaxies, as those of Heber Curtis and Vesto Slipher were doing. Hubble started to keep his words fairly neutral, adopting the guarded language that came to be a trademark of his research reporting. He was now consciously hiding his biases to avoid criticism.
Hubble was far more vocal and forthright, though, about his observational plans. In February 1922 he sent a lengthy, typewritten letter to Slipher, a member of the Committee on Nebulae for the International Astronomical Union, on his long-term strategy for studying the nebulae. It was going to be an all-out attack. Hubble planned to determine their structure, peg their distribution across the heavens, and measure their dimensions. And as a stealth advocate of the island-universe theory, Hubble wanted to obtain undeniable proof that stars—vast collections of stars—resided in the spiral nebulae. He knew that finding novae were crucial in doing this and urged the IAU that “half a dozen of the largest spirals in addition to Andromeda should be followed carefully for novae.” Major Hubble was now applying his lessons on military tactics to conquering his astronomical targets.
“I must confess that I am rather dazed by [Hubble's] letter,” said Lick astronomer William H. Wright, who had also received a copy of Hubble's agenda. “One can see that the nebulae will have no private life when he has his way. Hubble is a great lad, and I only hope that he will have the strength and energy to carry out a fraction of the work he would like to see done.”
Hubble, who had just gained a seat on the committee, was particularly fired up about a nebula classification scheme he wanted the IAU to adopt. To Hubble, properly categorizing the nebulae was an essential first step in determining their physical nature. By 1923 he had divided the nongalactic nebulae into two categories: the ellipticals and the spirals. An elliptical was an amorphous blob shaped somewhat like an egg. The spirals, of course, were the stunning pinwheels. If the bright center of the spiraling disk was a round bulge, he called it a “normal spiral;” if elongated, a “barred spiral.” The nongalactic nebulae that didn't fit either class, like those resembling the chaotic Magellanic Clouds, were tagged “irregulars.” But the IAU committee dragged its feet on Hubble's naming system and desired some changes, a rebuke that may have had long-term effects. At one point in the long wait, Knut Lundmark published a similar scheme, which enraged Hubble. He accused the Swedish astronomer of plagiarism. Afterward, Hubble was never keen to work on committees, attend general astronomy meetings, or share in collaborations. With a few exceptions, he tended to work alone. There might have been another reason for this as well. Though displaying a commanding public presence, Hubble was actually “pathologically shy around colleagues with whom he had little… contact,” contends Allan Sandage, who knew Hubble in his later years. Hubble proceeded to classify the nebulae in his own way and over time his arrangement was eventually accepted by the astronomical community.
Throughout 1923, over a total of forty-seven nights on the mountain, Hubble used both the 60-inch and 100-inch telescopes to survey a variety of nebulae around the celestial sky. He was on a reconnaissance mission. Though scarcely any nebulae were repeated, he did pay special attention to NGC 6822, a nebula in Sagittarius first discovered in 1884 by his former Yerkes colleague E. E. Barnard. The nebula stood out from the pack because it looked strikingly similar to the Magellanic Clouds in the southern celestial hemisphere.
The 100-inch and 60-inch telescopes (left, right) side by side on Mount
Wilson (Courtesy of the Archives, California Institute of Technology)
By July Hubble found five variable stars in NGC 6822 and informed Shapley at Harvard, suggesting that Shapley investigate the object on the plates stored away at the Harvard observatory. “What a powerful instrument the 100-inch is in bringing out those desperately faint nebulae,” responded Shapley. “As for N.G.C. 6822, I think there is no doubt but that it is another star cloud like the Magellanic Cloud.” Although there was no love lost between Shapley and Hubble, the two astronomers maintained a courteous correspondence, perhaps adhering to that old adage, “Keep your friends close but your enemies closer.” In actuality, they needed each other. Shapley oversaw the world's foremost collection of astronomical photographs, while Hubble had ready access to its largest telescope.
Shapley proceeded to estimate the distance of NGC 6822 by comparing its size and the observed magnitudes of its brightest stars to that of the Large Magellanic Cloud. Interestingly, he arrived at a distance of about a million light-years. “It appears to be a great star cloud that is at least three or four times as far away as the most distant of known globular clusters and probably quite beyond the limits of the galactic system,” reported Shapley in his observatory's December 1923 Bulletin. A news report by Science Service promptly called it “the most distant object seen by man, another universe of stars.” NGC 6822 wasn't a spiral nebula, but it certainly offered Shapley proof that large stellar systems existed beyond the Milky Way. Yet, for Shapley, his distance calculation for this stellar cloud simply had no bearing on the question of the spirals. For those he tenaciously held fast to his convictions and continued to spread the word in various publications that spiral nebulae were “neither galactic in size nor stellar in composition.”
Hubble obtained more than fifty photographs of NGC 6822 over time and found fifteen variable stars. “Eleven…are clearly Cepheids,” he eventually reported two years later. Using them as standard candles, Hubble calculated a distance of some 700,000 light-years, which was undoubtedly beyond the borders of Shapley's newly supersized Milky Way. “N.G.C. 6822 lies far outside the limits of the galactic system,” stated Hubble, “and hence may serve as a stepping-stone for speculations concerning habitants of space beyond.” His early work on NGC 6822 likely gave Hubble the confidence that he could pursue Cepheids as distance markers in spiral nebulae, observations he was carrying out at the same time and would actually report on first.
Observing with the 100-inch was a choreographed dance within the monumental dome a hundred feet high and nearly as wide. Sometimes Hubble could just lean back in a bentwood chair, his favorite, and serenely smoke his pipe in the darkness while taking a photograph. But other times he was perched high in the air on a platform that could adjust to any height via rails set on either side of the dome opening. With the telescope's clock drive shifting the telescope as the nighttime sky slowly moved overhead, he and his assistant made sure the advance stayed in synchrony with Earth's rotation. At the same time, they had to keep the dome rotated and the platform height adjusted, so that the telescope kept spying on the cosmos and not an inside wall. “This was the astronomical observing experience at its best,” noted Mount Wilson astronomer Allan Sandage, “a dark, quiet dome, a silently moving monster telescope, and mastery of the dangerous…platform, all in the interest of collecting data on a problem of transcendental significance.” Night after night, the cosmic waltz went on. If Hubble got clouded out, he had a backup: “You begin with deskwork, later you turn to heavy reading, and later, to a detective story,” he said.
Edwin Hubble observing at the 100-inch, sitting on his
favorite bentwood chair (Reproduced by permission of the
Huntington Library, San Marino, California)
The only scheduled break was “lunch,” provided at midnight. In the early years, it was simply hardtack and cocoa (Hale considered coffee “unwholesome”), served in a concrete bunker beneath the 60-inch. Later on, at a shack built halfway between the 60-and 100-inch, astronomers were offered two pieces of bread, two eggs, butter and jam, and a single cup of coffee or tea, a repast purposefully kept skimpy by the observatory's notoriously frugal administrator, Walter Adams. Hubble gained the respect of the night assistants when he washed his own dish afterward, giving them a break from their cleaning responsibilities. The assistants also liked Hubble's no-nonsense attitude. Unlike some other Mount Wilson astronomers, he always arrived for his scheduled runs with a well-thought-out observing plan in hand. He delegated authority and expected a professional performance in return. “You knew where you stood with him,” said Humason.
Hubble's observations at this time were fairly routine as he methodically went from target to target. He was noted for carrying a map of the heavens in his head; the hundred-odd Messier objects were as familiar to him as the alphabet. On July 17 he stopped to confirm a new and wispy nebula that Shapley had reported seeing on two occasions earlier that year in the Boötes constellation. But even after a 150-minute exposure, Hubble came up empty-handed. He saw nothing in that area of the sky. “Shapley object is probably an accident,” wrote Hubble in his logbook. From a photo he took on August 15, he spotted the track of an asteroid passing by. Week by week the routine continued.
And then came the October surprise.