The Day We Found the Universe (35 page)

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 lightyears 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 lightyears 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 lightyears, 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.