The Day We Found the Universe (28 page)

Given what was at stake, van Maanen followed all the precautions: He switched the plates in the holders to eliminate machine error, and he got a colleague to redo the measurements with a different machine, to make sure there wasn't an instrumental error or personal bias. He came to believe that the matter within the spiral was drifting away from the center—outward along the arms—and noted in his report that this agreed with the Chamberlin-Moulton model on the origin of spiral nebulae, which involved a collision between a star and a nebula. Thomas Chamberlin was elated to hear the news from Hale. “While the recent revival of the notion that spiral nebulae are mere distant constellations has not seemed to me to have any substantial basis, it is a satisfaction to feel that definite evidence is about to give it a quietus,” he responded.

Van Maanen was aware that his work “might indicate that these bodies are not as distant as is usually supposed to be the case,” but he kept that speculation out of his early reports. That's partly because in 1917 he measured a rotation for the Andromeda nebula with error bars larger than his result. “So that we do not know yet if this is an island universe!” he told Hale.

But that was the exception. Van Maanen primarily got the answer that many expected: Spiral nebulae exhibited internal motions and so must be relatively nearby. Moreover, the announcement was being made by a widely respected astronomer working at the world's premier observatory, whose expertise in stellar measurements was lauded. “His wide experience in astrometric work,” Walter Adams later recalled, “gave his conclusions a high standing among astronomers.” Other observers even confirmed that the spirals were changing; concurring reports came out of Mount Wilson, the Lowell Observatory, and observatories in both Russia and the Netherlands. It became the conventional wisdom among astronomers. And why not? It fit the general opinion of the time.

Only a few, such as Heber Curtis, openly disagreed. Curtis, with his wealth of spiral nebulae photographs at Lick, had earlier attempted to measure a change in the spirals over the years but could only conclude that “a much greater time interval will probably be necessary before nebular rotations can be definitely established.” He knew that many of the older plates that van Maanen was perusing were very poor and useless for measuring anything. To Curtis comparing a photograph made at Lick in 1900 with a more modern picture taken with a completely different telescope at Mount Wilson was a fool's errand, which is why Curtis found it easier than Shapley and others to dismiss van Maanen's data right away. “The mean of five measures each of which is not worth a damn, has a maximum value of only five damns,” he liked to say sarcastically.

But Curtis's warning was not heeded. With hindsight, it now seems easy to dismiss van Maanen's measurements. But at the time it was extremely difficult to assess. Van Maanen was no slouch at telescopic measurements and his finding a spiral rotating appeared quite reasonable. One of the era's leading theorists, the Britisher James Jeans, was especially eager to jump on van Maanen's bandwagon. Upon hearing the Dutch astronomer's results, Jeans speedily sent off a letter to the journal
Observatory
, saying they were “entirely in agreement with some speculations in which I have recently been indulging.” In calculating the behavior of a blob of gas, rotating and condensing, he had determined that tidal forces would lead to the formation of spiraling arms. And now Van Maanen was providing the observational evidence to back him up. Jeans eventually wrote up his ideas in the book
Problems of Cosmogony and Stellar Dynamics
, which exerted a tremendous influence on astronomers at the time. Moreover, both van Maanen and Jeans began to calculate higher masses for the spirals. So, instead of a single solar system in the making, they began to think of a spiral nebula as the start of a dense (but still small) cluster of stars.

As more plates became available, van Maanen expanded his study to include other spirals. He measured a rotational period of 160,000 years for M33 (Triangulum), 45,000 years for M51 (Whirlpool), and 58,000 years for M81, a handsome spiral in the Ursa Major constellation. Other nebulae followed. All were rotating in such a way that the spirals appeared to be unwinding their arms, spreading them farther outward. He figured the spirals were no more than several hundred lightyears wide and ranged in distance from one hundred to a few thousand lightyears away.

Soon van Maanen was running out of spiral nebulae to measure, as few had been regularly photographed for comparison over the years. As a double check on his dexterity with the Blink, he measured a simple globular star cluster, M13, which was known not to rotate. If there were any instrumental error, he should have mistakenly measured a motion, but he didn't, which seemed to imply his methods were valid. A British astronomer independently checked his methods as well and concluded that no one “would be so bold as to question the authenticity of the internal motions…. In fact, the more one studies [van Maanen's] measures, the greater is the admiration which they evoke.”

Adriaan van Maanen's markings on a photo of M33 indicating the
rotation he measured
(From
Astrophysical Journal
57 [1923]:
264-78, Plate XIX, courtesy of the American Astronomical Society)

“I finished…my measures of M51,” van Maanen wrote Shapley in the spring of 1921. “The results look more convincing than M101… Motion outwards along the spirals + some motion away from the center…. By this time Curtis and [Swedish astronomer Knut] Lundmark must be the only strong? defenders of the island-universe theory.”

“Congratulations on the nebulous results!” responded Shapley. “Between us we have put a crimp in the island universes, it seems,—you by bringing the spirals in and I by pushing the Galaxy out. We are indeed clever, we are.” Shapley reported on his friend's latest results at that summer's American Astronomical Society meeting in Connecticut. “I think that your nebular motions are taken seriously now,” he told van Maanen afterward, “and nobody…dared raise his head after I explained how dead the island universes are if your measures are accepted.”

The two were feeling quite cocky. At this stage, van Maanen at last made it publicly known, in the
Proceedings of the National Academy of Sciences
, that his observations “raise a strong objection to the ‘island-universe’ hypothesis.” If M33, the prominent spiral in the Triangulum constellation, for example, were several million lightyears distant, he pointed out, the motions he detected would represent velocities near the speed of light, “which, obviously, are extremely improbable…[and] afford a most important argument against the view that these nebulae are systems comparable with our galaxy.”

But this declaration was hardly a resolution to the Great Debate. While Shapley and van Maanen were smugly celebrating, Knut Lundmark was visiting the Lick Observatory, using the Crossley reflector to gather the extremely faint light of M33. It was a difficult task, requiring extremely long exposures, one totaling thirty hours collected over four nights. Lundmark eventually saw that the light from the nebula's spiral arms resembled nothing less than the light of ordinary stars. Where other astronomers had seen a fuzzy patch in a spiral arm and called it a “nebulous star,” Lundmark pondered whether each mistlike spot was instead “a great number of very distant stars…crowded together [to] give the impression of nebulous objects.” That led to his cogent conclusion: that his observations of the spiral arms “speak for a large distance.” The respected Swedish astronomer soon became one of the loudest voices championing the existence of other galaxies, and Shapley began to feel sizable pressure on his beloved model of the universe under Lundmark's onslaught.

Meanwhile, Slipher, in Arizona, had dispatched a story to the
New York Times
revealing that he had found a new “celestial speed champion,” a faint spiral nebula that he judged had to be “enormously large” and “many millions of light years” away. And in the following year, 1922, Ernst Öpik, at the Dorpat Observatory, in Estonia, carried out an elegant calculation demonstrating how the Andromeda nebula must be some 1.5 million lightyears distant. He did this by assuming that its mass and luminosity were comparable to those of the Milky Way. This “increases the probability,” reported Öpik in the
Astrophysical Journal
, “that [Andromeda] is a stellar universe, comparable with our Galaxy.” Thrust and parry. Thrust and parry. The duel over the island universes continued. Nothing would be settled until astronomers obtained a clear and unequivocal distance measurement to a spiral nebula—an observation so clear, so decisive, so comprehensive, that it immediately quelled all doubts.

Poor Shapley, it turns out, did put himself in jeopardy with his performance before the National Academy of Sciences gathering. Still in his thirties, Shapley was judged as too impetuous and immature to be the head of the Harvard College Observatory. Instead, his Princeton mentor, Russell, was offered the position. “Shapley couldn't swing the thing alone,” Russell confided to Hale two months after the conference. “I am convinced of this after…observing Shapley at Washington. But he would make a bully second … if he grew intellectually he would be a prodigy!”

Russell gave the Harvard directorship intense consideration, with the understanding that Shapley would be his assistant. “At this point,” continued Russell to Hale, “I would like to see your expression! I know I have my nerve with me: but,—and here I am very serious indeed,—consider what Shapley and I could do at Harvard! Between us, we cover the field of sidereal astrophysics pretty fully…and I might keep Shapley from too riotous an imagination,—in print.”

But Russell, after nerve-racking deliberation and an attractive counteroffer from Princeton, ultimately declined the job (“I would rather do astronomy,” he confided to Shapley). Harvard came back to Shapley, but not for the top position. Harvard officials brought up the title of “Chief Observer or something of the sort.” He, a bit miffed, curtly turned it down. A month later, however, Shapley reversed his decision when Harvard (spurred by a suggestion from George Hale) agreed to try him out for a year as chief of staff, starting in the spring of 1921. He obviously passed muster, for he was soon named full director and served at the post for thirty more years, working at his unique desk that turned like a wheel—“a kind of rotating galaxy for ideas,” noted a friend.

Shapley breathed new life into the sclerotic institution, bounding up the stairs two steps at a time and greeting everyone with a sporty cheerfulness. “He cast spells over people,” said one staff member. Pickering had run the observatory like an absolute monarch. Under the youthful and energetic Shapley, it became a band of enthusiastic workers. Leo Goldberg, a student at Harvard in the 1930s, compared him to a benevolent Mafia Godfather. On the one hand, “he inspired us all,” said Goldberg. “He pepped us up, he raised us out of the depths of discouragement many times.” But a darker side lurked within Shapley as well. Adopting a “divide and rule” principle, he could be a father figure to some, while a tyrant to others. He also stubbornly ignored new scientific data at times, if it conflicted with his personal vision of how the universe should work.

Even as Shapley settled into Harvard, his former employer requested one more task from him. He was asked to contribute to Mount Wilson's annual report, to recount the final work he carried out there in 1920. “I thought I told you that I left Mount Wilson just to avoid this ordeal,” he replied playfully. “Suppose I had lived wickedly and unrepenting died—would you even then haggle with His Majestic Nibs for your annual tithe of Blood-and-Brain?” Shapley was again being Shapley. It was his last hurrah for the California observatory. Mount Wilson got its notes.

Meanwhile, Curtis, who could have done much toward solving the mystery of the spiral nebulae, stepped out of the race entirely. Just a few months after the debate, he left the Lick Observatory to become director of the Allegheny Observatory, the same post that James Keeler once held. He had actually tendered his resignation ten days before the Washington debate took place. Being in charge of an observatory, a more highly paid position with increased prestige, was an opportunity hard to pass up, especially for a family man. But, as with Keeler, the urban setting, cloudy weather, and poorly equipped telescope at the Pennsylvania observatory ultimately prevented Curtis from making any further cutting-edge discoveries. Some considered it “the biggest mistake he ever made.” Even Curtis later confessed to his former boss Campbell that “the California combination of instruments PLUS climate is a hard one to beat… There is no place like the hill [Mount Hamilton] for astronomical work and…any man who leaves these opportunities is bound to be sorry for it.” A visiting colleague found him at Allegheny one day puttering with an instrument and chided him for turning into a toolmaker. “You play golf don't you? Well, this is my golf,” he responded.