"The Day We Found the Universe"--H. Shapley & the Milky Way

The Day We Found the Universe

ISBN-10: 0375424296
ISBN-13: 978-0375424298

"Twinkle, Twinkle, Little Star, Tell Me Are You Very Far?"

by

Joel Achenbach

April 26th, 2009

The Washington Post

Famous astronomy anecdote: It's 1923, and astronomer Harlow Shapley, the leading proponent of the theory that the Milky Way is the one and only galaxy, gets a letter from Edwin Hubble. Shapley reads it, turns to a colleague and says, "Here is the letter that has destroyed my universe." Marcia Bartusiak's new book is the backstory of that anecdote.

At issue are faint wisps of light known as spiral nebulae. Astronomers first detected them in the 18th century. There were dozens of them -- no, hundreds. Their nature was furiously debated. One camp argued that they were within the Milky Way, solar systems in the making -- clouds of dust and gas with an embryonic star at the center. The other camp argued that they were agglomerations of stars -- "island universes" -- that were outside the Milky Way and were small and faint only because of their immense distance.

The debate took a couple of centuries to play out. In the meantime, under scrutiny by ever larger telescopes, the spiral nebulae proliferated. There were thousands, perhaps millions of them. (Billions, it turns out.) For a while the island-universe theory was ascendant. Then contradictory observations pointed to the baby-solar-systems theory. We get all the way to the 1920s with the nebulae still a mystery, and astronomers still trying to figure out the scale of the universe.

The story of the spiral nebulae is a familiar one to astronomy buffs, but Bartusiak's intelligent and engaging book may well become the standard popular account. Some of the early chapters could have benefited from a red pencil here and there to excise unneeded verbiage, but that problem fades as the author hits her stride.

More problematic is the comprehensiveness of the tale. There are moments when I found myself despairing at the arrival on the scene of yet another astronomer, yet another telescope, yet another set of photographic plates, yet another incremental teasing of the truth from the murky heavens. Bartusiak cannot be accused of leaving anyone important out of her story. Indeed, there are almost as many characters as there are stars in the sky. Some of them, such as Shapley and Hubble, are charismatic and quirky; some never quite seem as interesting as their telescopes. However, there is a fine set piece on Henrietta Leavitt, a Harvard assistant who, laboring in this rigidly patriarchal field, realizes that certain stars serve as standards for measuring cosmic distances (she might have won a Nobel Prize had she lived longer).

The astronomers practice heroic science. The telescopes get bigger. The mountaintops get higher and colder. The universe becomes clearer: The nebulae are, indeed, island universes -- separate galaxies outside the Milky Way. Shapley's "Big Universe" turns out to be but a meager portion of Hubble's galaxy-strewn cosmos.

Bartusiak's book is, ultimately, about how hard science is, how taxing, particularly when you are trying to excavate truth from a grudging universe. The astronomers get it wrong about as often as they get it right. Just when a consensus seems to be forming, it is obliterated by a new observation.

There was no single breakthrough, but many of them, as well as many mistakes and misapprehensions. Hubble famously gets the credit for solving the mystery -- a certain kind of variable star he found in the Andromeda nebula revealed that Andromeda is a separate galaxy at great distance -- but his discovery was built on the labor and insights of so many others. Let's throw some love to Vesto Slipher. And Heber Curtis. Oh, and one more thing: Those distant spiral nebulae are racing away from us. Hubble figured that out, too, and with it the most compelling evidence that we live in an expanding universe.

Modern astronomy uses magnificent tools to intensify our perception. The universe says, "Look at me." The astronomers oblige, and you know how it turns out: The universe gets much bigger and much more interesting than we ever could have imagined.

Amazon Exclusive: A Q&A with Marcia Bartusiak...

Question: Was there really a single day when the modern universe was revealed?

Marcia Bartusiak: In some ways there was a unique day: January 1, 1925, at the height of the Roaring Twenties. That's the day when astronomer Edwin Hubble finally announced that the Milky Way was not alone but surrounded by sister galaxies just like our own. Eventually, Hubble directed our eyes to hundreds of billions of other galaxies, scattered like separate atoms through an ever-expanding space. It was the astronomical news of the century, if not of all astronomical history.

Q: In your book Hubble turns out to be a more complex character than portrayed in most astronomy books.

MB: He was an odd bird, but certainly a handsome one. Friends called him an Adonis. I think he resembles the British actor Jeremy Irons. Raised in Missouri, in a solid middle-class household, Hubble somewhere along the line yearned to be singular and distinct. Once he graduated from the University of Chicago, he went to Oxford University as a Rhodes scholar, where he completely reinvented himself; he adopted a British accent that he maintained for the rest of his life, dressed like a dandy, and began to add dubious credentials to his resume, like saying he once practiced law, which he never did. He married into a rich Los Angeles family, and throughout his life seemed intent on erasing his Midwestern roots. His wife never met Hubble’s mother or siblings. Hubble was not chums with his astronomy colleagues but preferred to socialize with the actors and writers in nearby Hollywood. One astronomer called Hubble, often arrogant and standoffish, a "stuffed shirt."

Yet, while Hubble fibbed to his friends about his background, he was meticulously careful about his science. In fact, when he obtained the first evidence in early 1924 that the Andromeda nebula was truly a distant galaxy, he held off an official report for almost a year. He first wanted to counter every possible argument against his find. Being caught in a scientific error was Hubble's greatest nightmare. And when he did finally release the data at that astronomy meeting on New Year's Day in 1925, after a lot of arm-twisting from his colleagues, he wasn’t even there. He had someone else relay the findings.

Q: The Day We Fond the Universe informs us that there were numerous important figures whose efforts contributed to this monumental discovery-that Hubble didn’t do it alone as the textbooks today seem to imply.

MB: Not at all. This is a far richer story--filled with trials and errors, serendipitous breaks, battle of wills, and missed opportunities. Several astronomers could have snatched victory years before Hubble but for various reasons didn't. However, they constructed the firm foundation that allowed Hubble to step in and make his great discoveries, revealing the modern universe as we know it today.

Q: Who are some of those other astronomers?

MB: The first was James Keeler, then director of the Lick Observatory on Mount Hamilton in California near San Jose, the first observatory in the world to place a gigantic telescope at high elevation. Its lenses were a yard wide. But Keeler chose to spend his time at a smaller telescope, which every other astronomer on his staff despised. He fixed it up and began to discover that there were tens of thousands of faint, disklike nebulae arrayed over the celestial sky. This was in 1899. At the time most astronomers thought these spiraling clouds were baby solar systems in the making. If he had continued, Keeler had a good chance of revealing they were actually galaxies, other Milky Ways. He had the smarts (he was one of the best astronomers in his day) and he had the equipment. But he died at the age of 42, likely of lung cancer. He was never seen without a cigar in his mouth. If he had lived, it might have been the "Keeler Space Telescope" now orbiting the Earth.

Q: Didn't anyone follow-up?

MB: Not right away, oddly enough. Most astronomers at this time were primarily concerned with the Sun and stars. The study of nebulae was not popular. It wasn’t until the 1910s that Heber Curtis, another Lick Observatory astronomer, went back to the same telescope that Keeler used and advanced this work. He found so many new nebulae that he estimated there were at least a million around the sky. Moreover, he began to report that they were indeed distant galaxies. He told one reporter that one he sighted had to be 20 million light-years away, an astounding distance for its time.

Q: So why don't we remember Curtis as the discoverer of the modern universe?

MB: Because all the evidence Curtis gathered was merely circumstantial. Astronomers were waiting for a "slam dunk." The novae, or sudden flare-ups, that occasionally appeared in these spiraling nebulae suggested they were far-off, since the novae were so faint when compared to the ones that pop off in our own Milky Way. But no one was sure. Some of the novae were so bright, there wasn't any physics to explain the phenomena. This was before astronomers understood that stars could completely explode. Curtis was on the verge of solving the mystery, but he took himself out of the game when he accepted the directorship of an observatory in Pennsylvania, where the nighttime skies were so bad that he could no longer compete.

What was needed to resolve the problem was an undeniable distance measurement out to those nebulae. It required a cosmic yardstick, but none was available. And that’s where an interesting woman, Henrietta Leavitt, comes in.

Q: The role of women in astronomical history is prominent in your work. What are the parallels between their experiences and those of contemporary female researchers?

MB: It was a far different time for women in the sciences at that time. Women astronomers weren't allowed to observe on the major university telescopes. It was considered unseemly to have women and men work together on an isolated mountaintop. At Harvard, for example, women were mainly relegated to being what were called "computers"-staying in offices, scanning photographic plates and recording each star's position, luminosity, and spectrum. Yet it was immensely valuable work. In the course of it, Henrietta Leavitt astutely discovered the celestial Rosetta Stone that later allowed Hubble to make his great discoveries. In 1912 she found a unique pattern to the blinking of variable stars called Cepheids. These are stars that repeatedly brighten and dim over a matter of days, weeks, or months. She revealed that the brighter Cepheids had the slower periods; the dimmer ones were faster. That meant you could follow the Cepheid's change from afar, determine its period, which would let you know how bright the star is and hence how far away it was.

Harlow Shapley, a young up-and-comer at the new Mount Wilson Observatory in southern California, was the first to take advantage of this wonderful new yardstick, discovering that the Milky Way was far larger than anyone had ever suspected. Ten times larger. It was now 1918, and Shapley could have continued outward, determining the distances to those mysterious spiral nebulae and beaten Hubble to the brass ring--but he didn’t.

Q: Why not?

MB: Because Shapley was mulishly wedded to his own vision of the universe. To him, the Milky Way was so big that its borders defined the very boundaries of the universe. The spiral nebulae were mere appendages. He saw no reason to study them. He regretted that blunder for the rest of his life.

Hubble had by then arrived at Mount Wilson, and at first stood in Shapley's shadow. Shapley was the golden boy of astronomy for his remake of the Milky Way. The two astronomers never got along, throughout their professional careers. Shapley, also from Missouri, 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. To Hubble's relief, Shapley soon left Mount Wilson to become director of the Harvard College Observatory, which allowed Hubble to focus on the spiral nebulae and make his great discovery.

Q: How did Hubble go on to see the universe expanding?

MB: Well, that's where the standard textbooks don't get the story quite right. There was another astronomer, by the name of Vesto Slipher, who actually found the first glimmer of evidence that the spiral nebulae were fleeing outward. He did this from the Lowell Observatory in Arizona. By 1917 Slipher was sure they were distant galaxies and even reported they might be "scattering" in some way. By 1925 he pegged the velocities of more than forty galaxies, a momentous accomplishment because the galaxies are so faint. It sometimes took weeks at the telescope for Slipher to clinch just one velocity.

In 1929 Hubble took on a partner, Milton Humason, to see if the galaxies were moving outward in a specific way. Hubble pegged the galaxies’ distances, while Humason measured their velocities. Putting this information together, Hubble did find a trend: the velocity of the galaxies steadily increased as he probed deeper and deeper into space. At double the distance, a galaxy's speed doubled as well. But when Hubble first published this rule, he solely used Slipher's data already on hand. Yet he made no mention whatsoever of Slipher in the paper--no citation, no acknowledgment, a serious breach of scientific protocol. Slipher deserves half the credit but is now largely forgotten by the public.

Moreover, Hubble had no idea at this stage that his newfound rule meant the universe was expanding. That understanding didn't arrive until 1930, when astronomers finally became acquainted with the work of the Belgian Georges Lemaître, both a theorist and Jesuit priest. Working out a cosmological model based on Einstein’s general theory of relativity, Lemaître predicted that space-time was moving outward, with the galaxies going along for the ride. He did this in 1927, two years before Hubble even published his rule. But Lemaître's model went unnoticed for a couple years, because it was published in an obscure Belgian journal.

But today this story is now vastly simplified: everyone says Hubble went to the great 100-inch telescope on Mount Wilson and, voilá, discovered the expanding universe. It’s an ironic twist, because Hubble was never a champion of a universe ballooning outward. "It is difficult to believe that the [galaxy] velocities are real," he told a reporter. Up until he died in 1953, he always referred to the galaxy speeds as “apparent velocities,” to protect his legacy just in case a new law of physics sneaked in and changed the explanation. Hubble coveted an unblemished record: the perfect wife, the perfect scientific findings, the perfect friends, the perfect life.

Q: You write about these astronomical discoveries in light of the cultural and geopolitical context of the early 20th century. What were the connections?

MB: It was a unique moment, a fantastic era when technology was rapidly on the rise. Astronomy blossomed within this atmosphere. Cameras became standard equipment on telescopes, capturing pictures of stars and nebulae never before seen. And spectroscopes allowed astronomers to discern the very chemistry of the heavens. More important, prominent industrialists, enriched by the bounty of the Gilded Age, provided the money that allowed American astronomers to construct the large telescopes so crucial to solving the mystery of the spiral nebulae.

In this venture, American astronomers were also aided by a more somber event. European astronomers were diverted by World War I and its resulting turmoil. This allowed American astronomers to freely push forward on the most outstanding question of the day. Figuring out the universe’s true nature became an American obsession, its participants drawn from the Lick, Mount Wilson, and Lowell observatories newly built in the U.S. West. The world’s older observatories didn't have a chance at all, because the Americans had the most advanced telescopes perched on high-elevation sites, a combination that was essential to cracking the mystery.


"The Great Debate" [1921]--Shapley & Curtis


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