The Day We Found the Universe

by Marcia Bartusiak

  Hale took nearly all the best Yerkes men with him to his new astronomical Shangri-la. He had a magnetic aura that drew in people and kept them in awe of him. His second in command at Mount Wilson, Walter Adams, once admitted that he stuck with Hale and astrophysics “partly because of the strong influence of Dr. Hale's remarkable personality…. A very slight change in circumstances might equally well have led me to follow the teaching of Greek as a profession.”

  Others on Hale's charter staff did not have a formal education in astronomy but instead trained on the job, bringing with them valuable skills from such fields as photography and mechanical engineering. These included Ritchey and Ferdinand Ellerman, who was first hired to assist Hale at his private observatory in Chicago.

  Hale eventually extended his search for employees beyond his Yerkes loyalists. When he heard about a PhD student from Princeton who was impressing everyone, he arranged to meet the young man in New York City. Harlow Shapley showed up fully prepped to discuss all the latest astronomical discoveries. Instead, the two men ended up talking about the operas Shapley had time to catch the day before. The conversation went on for a while, but then Hale abruptly remarked, “Well, I must be going.” Not one word on astronomy had passed between them—and no mention of a job. The Princeton grad assumed he had not passed muster, but to his surprise he soon received a letter from Hale. The message was all he had hoped for: “Please come to Mount Wilson.”

  The Solar System Is Off Center

  and Consequently Man Is Too

  Upon arriving at Mount Wilson, Harlow Shapley had no immediate investigative plans, only a developing interest in variable stars. He had told his Princeton mentor, Henry Norris Russell, that he would probably work on odds and ends. But Shapley's wife, also skilled in astronomy, soon came upon an interesting set of stars while examining photos of a globular cluster. “I have looked at some cluster plates a little,” Shapley wrote Russell, “and found five new variables in the middle of a cluster … or to tell the truth my hausfrau found them but I plan to take the credit for it.” It helped him latch onto a focus; he was going to study the Milky Way's globular clusters, each a dense ball of stars that gleams like a cosmic sparkler frozen in time.

  Shapley worked at Mount Wilson from 1914 until 1921, and the best research of his career was accomplished during this time. Shapley was a risk taker. As Hale later noted, “He is much more venturesome than other members of [the Mount Wilson] staff and more willing to base far-reaching conclusions on rather slender data.” Counting up his scientific publications over those seven years, Shapley was the sole author of or a contributor to some 150 notes and papers. Years earlier, none of his childhood friends would have bet on that career outcome, given that Shapley's first job was being a hard-nosed reporter, covering crime and corruption in the Midwest.

  Born in 1885, Shapley and his fraternal twin brother, Horace, along with an older sister, Lillian, and a younger brother, John, grew up on a Missouri farm a few miles from the town of Nashville, on the edge of Ozark country not far from where Harry Truman, the thirty-third president, was also born (in 1884). Shapley's father, Willis, was a hay dealer. Young Harlow attended a one-room schoolhouse for a few years but was mostly taught at home. When milking cows, he recited poems by Tennyson to “keep the rhythm going.”

  “The St. Louis Globe-Democrat was our chief contact with the outside world,” recalled Shapley. That may be why, at the age of fifteen, he became a reporter for the Daily Sun in Chanute, Kansas, a rough-and-tumble oil town about sixty miles northwest of his family's homestead. He later moved back to Missouri to work on the police beat for the Joplin Times. All the while he spent his free time reading in the local libraries, for Shapley's ambition right from the start was to save enough money to go to college. He eventually applied to the local high school, in order to work toward the diploma he vitally needed to matriculate, but, refused admission due to his meager educational record, he paid out of his own pocket to catch up on his academics at a collegiate prep school. Finishing up in 1907, at the age of twenty-one, he at last qualified for admission to the University of Missouri, just as his schoolteacher mother had always desired.

  Given his years of experience reporting on midwestern mishaps, Shapley had always intended to major in journalism, but upon arriving on campus he discovered that the promised opening of the university's School of Journalism had been delayed. “So there I was,” said Shapley later in life, “all dressed up for a university education and nowhere to go. ‘I'll show them’ must have been my feeling. I opened the catalogue of courses and got a further humiliation. The very first course offered was a-r-c-h-a-e-o-l-o-g-y, and I couldn't pronounce it! … I turned over a page and saw a-s-t-r-o-n-o-m-y; I could pronounce that—and here I am!” Shapley, a lover of tall tales since he was a child, was just joking around. He actually was in need of a job, and an offer from Frederick Seares, head of the university's astronomy department, to work for him at 35 cents an hour was likely the deciding factor. In whatever way Shapley came to major in astronomy, the choice suited him to a tee. Seares was mightily impressed by the former reporter, especially the fact, as he put it, that Shapley “thinks about what he is doing.” Within two years Seares had Shapley teaching the introductory astronomy course. Although starting out with little training in physics and mathematics, Shapley ended up in 1910 graduating with honors.

  Shapley spent another year at Missouri to obtain his master's degree and chose to go to Princeton for his PhD when he won one of its distinguished fellowships. One of his recommenders had warned Princeton officials to accept this rising star before their competitors had a chance to steal him away. There in the idyllic midlands of New Jersey, under the guidance of Henry Norris Russell, the eminent astronomer and theoretician, Shapley specialized in eclipsing binaries—two stars positioned in such a way that, as they circle, one periodically passes in front of the other when viewed from Earth, causing the binary's light to dim for a while and then rise back. Shapley became a whiz in handling a slide rule and consulting mathematical tables to compute the stars' orbits, as well as their densities and size, Russell's special area of interest. Such work was immensely valuable in confirming the wide range of stellar types, including the existence of giant stars.

  Young Harlow Shapley (Photo by Bachrach,

  courtesy of AIP Emilio Segrè Visual Archives)

  It was an odd pairing of adviser and advisee: Russell, with his stiff and aristocratic demeanor, the son of a Long Island clergyman, coupled with the “wild Missourian” with the round face and farmboy haircut, who once attended two New York City theater performances in one day and judged the experience as “worse than log tables.” But they came to appreciate each other's professional expertise and industriousness. According to Russell's biographer David DeVorkin, the two were often seen strolling the campus together, with Russell using “his cane to sweep the undergraduates out of their path.”

  The connections Shapley had made at Missouri proved crucial for his next career step. Seares, his undergraduate professor, had moved to Mount Wilson in 1909 and helped open doors for Shapley to become a staff astronomer at the celebrated observatory. Soon after Hale offered the position in 1912, at a salary of $90 a month plus free board on the mountain. Shapley delayed his start date in order to do some travel in Europe and stay with Russell a bit longer to complete their “crusade” on eclipsing binaries but at last journeyed to Mount Wilson in the spring of 1914. Along the way, he stopped off in Kansas City to marry his University of Missouri sweetheart, Martha Betz, a gifted scholar and linguist he had met in a mathematics class. She took an interest in astronomy once they started dating and even helped him reduce the piles of data he had collected for his doctoral dissertation. On their honeymoon train ride out to California, they together happily computed eclipsing binary orbits. In less than a decade, Shapley had gone from fledgling newsman to professional astronomer, about to look through the eyepiece of what was then the largest telescope in the world.

 
; Conditions at the mile-high observatory were still fairly primitive when Shapley arrived. “Just killed a 3 ft. rattlesnake with 8 rattles lying by our back door,” reported one pioneering staff member. “We had to be rugged in those days,” Shapley later recalled. “We would go up the mountain, a nine-mile hike, sometimes pushing a burro, sometimes not. The new road had not [yet] been put in.” When not on Mount Wilson, Shapley spent his time at the observatory's offices and workshops in Pasadena, a town then in the process of transforming from an agricultural community of lush citrus groves and vineyards to a winter resort town filled with flowers and wealthy visitors from the East.

  A sociable fellow, Shapley forged friendships with several colleagues right away, including solar astronomer Seth Nicholson and Dutch astronomer Adriaan van Maanen, the latter of whom first arrived at Mount Wilson in 1911 as a volunteer assistant and remained on as a staff member for thirty-five years. Among these friends and colleagues, Shapley was an incorrigible raconteur. “A discussion with him was like a rousing game of ping-pong, ideas flashing back and forth, careening off at unexpected angles and often coming to earth in a breathless finish,” said Cecilia Payne-Gaposchkin, who knew Shapley later at Harvard. An enormously vain man, Shapley also liked to be flattered and got along best with those who fawned over him. Moreover, he never forgave a slight. “A generous supporter, a stimulating companion, he could also be an implacable enemy,” added Payne-Gaposchkin.

  The one person Shapley couldn't sway with his gee-whiz midwestern charm was Walter Adams, the effective leader at Mount Wilson. Hale, prone to nervous breakdowns and bouts of depression, was often gone from Mount Wilson in the 1910s. Sometimes his absences were due to war work, but often because he was recovering from his illnesses. Whenever that happened, Adams was in charge. A proper and dutiful man known for his frugal ways, Adams was so regular in his habits that staffers could “set their clocks by his comings and goings.” An inveterate pipe smoker as well, Adams forged the “Lucky Strike” trail, a shortcut from the observatory to the cigarette stand of the rustic hotel then operating nearby on the mountain. Shapley often grumbled about Adams to his friends. “I feel very sure that if I should go away from here no opportunity would be given me to return so long as Adams has the deciding voice,” Shapley once told a colleague. But the tension between them didn't seem to affect Shapley's innovative work while he was on staff.

  The seed for Shapley's groundbreaking research was actually planted before he got to the mountain. While still a Princeton graduate student, Shapley had visited Harvard and there met veteran astronomer Solon Bailey, who suggested to the young man that he use Mount Wilson's new 60-inch telescope “to make measures of stars in globular clusters.” When Bailey was stationed at Harvard's Peruvian outpost in the 1890s, serving as its head, he had begun discovering large numbers of variables, hundreds of them (including Cepheids), in some of the clusters and sensed it was terribly important. He knew that a large telescope, such as the one on Mount Wilson, would be immensely valuable in extending this work. It would have the power to resolve variables in the crowded inner regions of a globular cluster and peg their pulsations.

  Shapley ultimately took Bailey's advice and, starting with the variables found by his wife, placed a firm stake in this domain. Shapley and globular clusters quickly “became synonyms” atop the mountain. Shapley's involvement became so intense that he eventually contacted Bailey, to make sure the Harvard astronomer didn't feel Shapley was trespassing on his celestial territory. “I have not intended to intrude upon your field, and I think that you do not feel that I am,” wrote Shapley. “Very much of my work on clusters has been the direct result of my conversation with you in Cambridge three years ago when you suggested the advantages of the Mount Wilson instruments and weather.” Bailey, a kind and gracious man, was in fact delighted by Shapley's joining in. “I hope you will appreciate the fact that I claim no proprietorship in these clusters,” replied Bailey, “but… welcome other investigators in this field.” It was fortunate that he was so affable. Bailey was primarily a data gatherer; Shapley by nature was a bold interpreter, a trait enhanced during his apprenticeship with Russell, who advocated problem-driven research. And that made all the difference in advancing the science.

  A globular cluster appears through a telescope as an assembly of brilliant specks of light hovering around a dense and blazing core. With stars packed in like subway commuters at rush hour, the cluster offers a far more exotic celestial environment than our local stellar neighborhood. Alpha Centauri, the star closest to the Sun, is some 4 light-years away. But if the Sun were in the center of a packed globular cluster, it would have thousands of stars closer than that, covering Earth's sky like a sequined blanket visible both day and night. Near misses between stars would be commonplace.

  That a globular cluster is a highly spherical collection of stars was not known until the 1600s, with the advent of the telescope. Before that, ancient astronomers simply noted the objects on their sky charts as a “lucid spot” or a lone “hazy star.” Today, these clusters are known to be arranged as a globelike halo, surrounding the disk of the Milky Way somewhat like bees buzzing around a hive. But as late as the 1910s, when Shapley began his observations, astronomers didn't know that, nor exactly how big an individual globular cluster was. Some even pondered if they were island universes in their own right. Shapley himself believed that was true when he was starting out: “It is quite obvious that a globular cluster … is in itself a stellar system on a great scale—a stellar unit which without doubt must be comparable to our own galactic system in many ways,” he wrote in the first paper of his study. Some dabbled with the idea that a spiral nebula was an early stage of a globular cluster about to form: Like an open flower closing at twilight, the spiral over time would fold up into a ball. Shapley's goal was to learn the globulars' true sizes, distances, and compositions and see if such ideas were valid.

  Shapley's initial observations were fairly basic. Using the 60-inch telescope, he simply surveyed the colors and magnitudes of the stars in the most prominent clusters. These included Omega Centauri (the biggest of them all), the Hercules cluster, and M3, a globular noted by Charles Messier in 1764. Shapley had no idea where this would lead, but that was standard practice in astronomy: Gather as much data as you can when faced with the unknown and keep your eye out for unusual trends. If anything, Shapley hoped his observations might help Hale in his quest to understand how stars aged and evolved, still quite a mystery to astronomers in the early twentieth century.

  Globular Cluster M80

  (The Hubble Heritage Team [AURA/STScI/NASA])

  As his collection of photographs mushroomed, though, Shapley began to identify Cepheids which he knew would serve as his measuring tape out to the globular clusters. He was quite aware of the paper that Henrietta Leavitt had published just a couple of years earlier and intended to apply it. “Her discovery … is destined to be one of the most significant results of stellar astronomy,” Shapley later wrote to her boss, Pickering.

  What was needed was a reliable distance to a Cepheid—any Cepheid, anywhere in the sky—that could serve as the calibration for determining the distances to all other Cepheids using Leavitt's period-luminosity law. That was the beauty of her discovery: Know the distance to just one Cepheid and you know the rest.

  Distance measurements have long been a problem for astronomers. To our eye, the celestial sky resembles a dark bowl with pinpoints of light affixed to it—everything appears to be the same distance away. But in reality the stars we see reside at vastly different ranges. Bluish-white Sirius, the brightest star in the heavens, is located 8.6 light-years from Earth; Vega, the prominent summertime star in the constellation Lyra, lies 25 light-years away. How do astronomers arrive at these numbers? “Parallax” is one surveying technique. Parallax is the apparent change in a star's position on the sky when observed first at one end of Earth's orbit and then six months later at the other end (similar to the way an object close by will appear
to shift when you view it first with one eye, then the other). By setting the radius of Earth's orbit as a baseline and knowing the angle of shift in the star's parallax, a bit of geometric triangulation determines the star's distance from the Sun directly. Astronomers devised the term parsec to describe the distance between Earth and a celestial object that displays a parallax of one arcsecond of angular measurement on the sky. (One parsec equals 3.26 light-years.) The parallax method is useful out to several hundred light-years. After that, the change in a star's position is too small to be discernible by ground-based telescopes, which is why Leavitt's law was so treasured. It would enable astronomers to extend their distance surveys much farther outward. It would have been nice if a Cepheid resided fairly close to our Sun; then astronomers could have measured the star's parallax and gotten their calibration fairly easily. Unfortunately, there was no Cepheid within reach of a direct parallax measurement from Earth in Shapley's day. Nature was not so accommodating to astronomers. (The closest Cepheid to us is Polaris, the North Star, located about 430 light-years away. Polaris is actually a three-star system, one of which is a large yellow Cepheid that completes its dim/bright cycle every four days.)

  The first person to try to confront the Cepheid distance problem was Ejnar Hertzsprung, who had initially recognized that Leavitt's twenty-five variables in the Small Magellanic Cloud were specifically Cepheid stars. He began to look at the Cepheids best studied within the Milky Way, thirteen in all. He couldn't measure their parallax (they were too far away), but he could consult a chronological sequence of astronomical atlases to see how far the stars had moved across the sky, at right angles to our line of sight, in their travels through the Milky Way. It was a matter of determining how their celestial coordinates had changed over the years. Astronomers refer to this advance as a star's “proper motion.” From another type of catalog he looked up how fast they were moving either toward or away from Earth based on the stars' blueshifts or redshifts (a rough gauge of their overall velocity). In an imaginative leap, he then estimated the Cepheid's distance by comparing the star's measured velocity with how fast it appears to be moving across the sky from our far away vantage point. The more distant the star, the slower it seems to journey across the sky. (His actual mathematical procedure, which also involved the Sun's motion through the galaxy, was more complex, but this provides the basic idea.) Hertzsprung's approach in the end provided a crude statistical calibration, one that he then applied to Leavitt's Cepheids in the Small Magellanic Cloud. He concluded that the cloud was 30,000 light-years distant, one of the greatest distances then measured for a celestial object. This demonstrated for the first time the potential power of Leavitt's discovery.