The Day We Found the Universe - Marcia Bartusiak (2009)
January 1, 1925
The twenties were not just roaring, they were blazing.
Moviegoers were flocking to the cinema to watch in amazement as Moses parted the Red Sea in Cecil B. DeMille's silent film epic The Ten Commandments, Greece overthrew its monarchy and proclaimed itself a republic, the first dinosaur eggs were discovered in Mongolia's Gobi Desert, and crossword puzzles became all the rage. It was the height of the Jazz Age, when Victorian ideals came tumbling down in a frenzy of flappers, Freudian analysis, and abstract art. While majestic ocean liners crossed the Atlantic in under five days, Clarence Birdseye introduced the public to the novelty of frozen food and a failed artist named Adolf Hitler published Mein Kampf. It was a world, wrote F. Scott Fitzgerald in his classic novel The Great Gatsby, “redolent of orchids and pleasant, cheerful snobbery and orchestras which set the rhythm of the year, summing up the sadness and suggestiveness of life in new tunes.”
It was also an era of immense scientific fervor. On December 30, 1924, some four thousand scientists descended upon Washington, D.C., to attend the annual conference of the American Association for the Advancement of Science. Taking advantage of the three-day gathering, the American Astronomical Society held its meeting in the capital at the same time, with nearly eighty astronomers attending from across the United States. They lodged at the Powhatan, a plush eight-story hotel located on the corner of Eighteenth Street and Pennsylvania Avenue, where a room with private bath cost $2.50 a night and weary travelers could relax in its rooftop garden. Two blocks away Calvin Coolidge opened the doors of the White House to the visiting AAAS members. While notorious for being a man of few words, the thirtieth president of the United States was uncharacteristically chatty the day of the reception. “It has taken endless ages to create in men the courage that will accept the truth simply because it is the truth,” Coolidge told his guests. “We have advanced so far that we do not fear the results of that process. We ask no recantations from honesty and candor… Those of us who represent social organization and political institutions look upon you with a feeling that includes much of awe and something of fear as we ask ourselves to what revolution you will next require us to adapt our scheme of human relations.” Six months later high school biology teacher John Scopes would go on trial in Tennessee for illegally teaching Charles Darwin's theory of evolution.
The astronomers, though, were scarcely aware that Washington was host to the largest number of scientists ever assembled for an AAAS meeting. Their interest was intently focused on the astronomy program, which included talks on the atmosphere of Mars, how fast celestial objects could move, the temperature of Mercury, and the latest computed orbit of the eclipsing double-star system Algol.
On Wednesday, the second day of the meeting, the astronomers were taken by glass-topped buses to the U.S. Naval Observatory, in the northwest sector of the town, for a tour of the facility and a buffet luncheon in its stately main hall. Later that evening, New Year's Eve, “occurred an event which was marked on the program and celebrated by a number of the faithful,” Popular Astronomy recounted. As the clock struck twelve, astronomers happily changed to civil reckoning for determining the start of a day. No longer would the astronomical day begin at high noon, a tradition launched in the days of Ptolemy that often led to great bookkeeping confusion. Instead, it now began at midnight, just as it did for everyone else. “It will probably be remembered and noted long after other astronomical happenings of the current year are forgotten,” stated the magazine.
But a presentation made on Thursday, New Year's Day, ultimately overshadowed all other events at the meeting. Looking out their hotel windows that inaugural morning of 1925, convention-goers discovered a blanket of snow covering the city, enough to give holiday sleds a good tryout, reported the Washington Post. Despite the ongoing snowstorm, however, the astronomers kept to their schedule and walked the short distance to the newly constructed Corcoran Hall, on the nearby campus of George Washington University, for a joint session with the mathematicians and physicists of the AAAS. They first heard a talk on stellar evolution, followed by a lecture posing the question “Is the Universe Infinite?” which led to a lively discussion among the conferees. Then right before the noon break, a paper modestly titled “Cepheids in Spiral Nebulae” was presented to the assembled audience. Those not familiar with astronomy likely imagined it was a minor technical work, of interest only to a specialist. But the astronomers in the room immediately grasped its significance. For them, it was electrifying news. Despite its lackluster title, this paper was no less than the culmination of a centuries-long quest to understand the true nature and extent of the cosmos. January 1, 1925, was the day that astronomers were officially informed of the universe's discovery.
The author of the paper was thirty-five-year-old Edwin Hubble, a staff astronomer at the Mount Wilson Observatory, in southern California. Hubble had aimed Mount Wilson's 100-inch reflector, the largest telescope in its day, toward a pair of celestial clouds known as Andromeda and Triangulum, the only spiral nebulae in the nighttime sky that can be seen with the naked eye. By having access to significant telescopic power, Hubble was at last able to resolve individual stars in the outer regions of the two mistlike clouds, and to his surprise and delight some turned out to be Cepheids, special stars that methodically dim and brighten as if they were slow-blinking cosmic stoplights.
The signals revealed that our galaxy, the Milky Way, was not alone. The Cepheids were telling Hubble that the Andromeda and Triangulum nebulae were very distant, situated far beyond our galactic borders. Our celestial home was suddenly humbled, becoming just one of a multitude of galaxies residing in the vast gulfs of space. In one fell swoop, the visible universe was enlarged by an inconceivable factor, eventually trillions of times over. In more familiar terms, it's as if we had been confined to one square yard of Earth's surface, only to suddenly realize that there were now vast oceans and continents, cities and villages, mountains and deserts, previously unexplored and unanticipated beyond that single plug of sod. Hubble directed our eyes to billions of other galaxies—other Milky Ways formerly unknown—scattered like separate atoms through space and time, as far outward as telescopes could peer. Indications of the Milky Way's true place in the universe had been cropping up for years, but the evidence was indirect, conflicting, and controversial. Hubble stepped into the fray and finally provided the decisive proof. He confirmed an idea to everyone's satisfaction that beforehand had been on far shakier ground.
It was the astronomical news of the century and yet Hubble, astonishingly, was not present—at this, his moment of triumph. Instead, the staid and respected Princeton University astronomer Henry Norris Russell stood in for Hubble that morning and relayed his findings to the conferees. From all accounts, Hubble was neither sick nor detained by family matters. He might have been put off by the long and wearying cross-country train ride, but the reason for his absence was possibly more idiosyncratic. Hubble, a former legal scholar trained in weighing evidence, was concerned that by the time of the astronomy meeting he hadn't countered every feasible argument against his finding. At his own observatory, in fact, a colleague had gathered the strongest ammunition against his conclusion, evidence Hubble couldn't yet refute. This loose end bothered him immensely. What Hubble craved was an airtight case—no stone unturned, no question left unanswered—before stepping up to the podium himself. Being caught in a scientific error was Hubble's greatest nightmare. Back in California the young astronomer was fretfully asking himself, Could I possibly be wrong?
With the stunning pictures of our resplendent cosmos now so widely circulated, such a part of the routine imagery that surrounds us daily, it's difficult to remember that less than a hundred years ago astronomers' conception of the universe was very different than it is today. There were no quasars, no distant galaxies, no exotic black holes or wildly spinning neutron stars. No one even knew for sure how the Sun could keep generating its tremendous energies over billions of years. What was called “the universe” consisted of a single, disk-shaped collection of stars that cuts a magnificent swath across the celestial sky. With Earth located within this great stellar assembly, we peer outward through the disk and perceive it as a band (much the way a plate looks viewed from its side). Known since ancient times as the Milky Way because of its ghostly white visage, our galaxy a century ago was not just the sole inhabitant of the cosmos. It was the cosmos—a lone, star-filled oasis surrounded by a darkness of unknown depth.
A few voices of dissent could be heard, arguing against this perspective. A growing number of small spiraling clouds were being sighted in the heavens; these faint celestial objects were lurking wherever a telescope gazed away from the Milky Way into deep space. Were these spiral nebulae close to us or were they farther off? No one knew, because at the turn of the twentieth century astronomers didn't yet have the means to determine their distance with assured accuracy. The only thing they could do was speculate. Some looked at these nebulae, shaped like springs unwinding, and thought, “Ah, nearby solar systems in the making.” Others observed the same tiny clouds and imagined them as a host of sister Milky Ways so distant that their stars melded into faint and misty whiteness. That would mean the Milky Way was not special at all but merely one island of stars caught in the midst of a far larger archipelago. But the majority of astronomers rejected this strange—even frightening—concept. That other galaxies existed seemed inconceivable, and so they fiercely clung to what they perceived to be their pivotal place in the cosmos. Nicolaus Copernicus may have moved Earth and its inhabitants from the hub of the solar system in the sixteenth century, but humanity remained comforted by the notion that it retained a privileged position in the very heart of the Milky Way, the sole galaxy. They rested easy knowing they resided in the very center of the universe. There was no hard-and-fast evidence to suggest otherwise.
The Milky Way over the Kitt Peak National Observatory, Arizona (Photo by Michael R. Cole, UrbanImager)
That contentment was shattered, though, as astronomy underwent a spectacular transformation, starting in the waning years of the nineteenth century. “This was an era of extraordinary change in every phase of human life on this planet,” recalled Edwin Frost, an astronomer who had personally witnessed the transition at the Yerkes Observatory in Wisconsin. “[It] was truly a Victorian age drawn to a close with the end of the century.” When Frost was growing up in the 1880s, Europe was the touchstone in matters of literature, painting, and science. “Even steel rails for the trunk-lines were imported from Britain as late as my college days,” he said. “Then Andrew Carnegie and others found that rails could be made better and cheaper in America… The child was rapidly getting out of its infancy.” Discoveries and inventions were on the rise. Seemingly overnight, there were electric lights, heating by coal, hot-air furnaces, indoor bathrooms, and automobiles smoothly traveling down asphalt-paved roads.
Astronomy blossomed within this atmosphere of teeming innovation. Cameras became standard equipment on telescopes, enabling observers to gather light over an entire night and so generate images of faint stars and nebulae never before seen. And spectroscopes, devices that separate starlight into its component colors, allowed astronomers to figure out what the stars and other celestial objects were truly made of. Suddenly the very chemistry of the heavens was in their grasp. Meanwhile, prominent industrialists, enriched by the bounty of the Gilded Age, provided the money that allowed big dreamers to construct the large telescopes they had so long desired.
Given the swift emergence of these technological improvements, dry textbook accounts, reduced to a discovery's most essential elements, make it appear as if Hubble's historic achievement had taken place overnight. He goes to the world's largest and best-equipped telescope and, voilà, he reveals a cosmos populated with myriad galaxies spread over space as far as the telescopic eye could see. The Milky Way suddenly becomes a minor player in a much larger drama, and Hubble is anointed cosmology's “prime architect” for making this astounding breakthrough. But that is not the case at all. In reality, Hubble stood on the shoulders of a series of astronomers farsighted enough to tackle a problem others had been ignoring. Answers did not arrive in one eureka moment, but only after years of contentious debates over conjectures and measurements that were fiercely disputed. The avenue of science is more often filled with twists, turns, and detours than unobstructed straightaways.
Astronomers trained in the older, classical ways, who dwelled on calculating the motions of the planets and measuring the positions of stars to the third decimal place, had not been distressed at all by the mystery of the spiral nebulae. They figured that once the matter was resolved it would not greatly change their perception of the overall structure and contents of the heavens. Simon Newcomb, the dean of American astronomy in the late nineteenth century, remarked at an observatory dedication in 1887 that “so far as astronomy is concerned…we do appear to be fast approaching the limits of our knowledge… The result is that the work which really occupies the attention of the astronomer is less the discovery of new things than the elaboration of those already known, and the entire systemization of our knowledge.”
Within ten years James Keeler, director of the Lick Observatory, in California, proved Newcomb was exceedingly shortsighted. Against everyone's advice, Keeler got a troublesome reflecting telescope—the first of its kind at high elevation—back in working order and demonstrated its power with singular panache. Even though the telescope's mirror was relatively small, it allowed him to estimate that there were tens of thousands of faint nebulae arrayed over the celestial sky, ten times more than had been known before. In the 1910s Lick astronomer Heber Curtis followed up on Keeler's findings and gathered additional evidence to suggest that these many spiraling nebulae were nothing less than separate galaxies. At the same time, a few hundred miles south at Mount Wilson, near Los Angeles, Harlow Shapley resized the Milky Way, measuring it as far larger than previously thought and shoving our Sun off to the side, away from the galaxy's hub. As Shapley liked to put it, “The solar system is off center and consequently man is too.”
The story of our universe's discovery centers mightily on Shapley and Hubble, scientific knights who jousted with each other for years over the universe's true structure. These archrivals shared similar backgrounds and yet couldn't have been more different in temperament and tactics. Both were born in rural Missouri and both came to astronomy through unusual routes: Hubble as a discontented high school teacher, Shapley as a crime reporter. And each, after obtaining his doctoral degree, was selected by the visionary George Ellery Hale to work at the Mount Wilson Observatory, the greatest astronomical venue in its day. Each pursued a question that few others were asking. For Shapley, it was our precise location within the Milky Way; for Hubble, our place in the universe at large.
Their work took place during a crucial moment of transition. While European astronomers were diverted by World War I and its resulting turmoil, American astronomers were free to push forward on the question of the spiral nebulae. Figuring out the universe's exact configuration became an American obsession, its participants drawn from the Lick, Mount Wilson, and Lowell observatories, newly built in the western United States. The world's older observatories had no chance at all, for at the Lick and Mount Wilson observatories, in particular, astronomers had access to advanced telescopes situated on prime high-elevation sites, a combination essential to cracking the mystery.
Hubble gets deserved credit for providing the last, painstaking turn of the lock. “Hubble's drive, scientific ability, and communication skills enabled him to seize the problem of the whole universe, make it peculiarly his own, contribute more to it than anyone before or since, and become the recognized world expert of the field,” wrote astronomer Donald Osterbrock, archivist Ronald Brashear, and physicist Joel Gwinn for a centennial celebration of Hubble's birth.
By 1929, just five years after his initial finding on the galaxies, Hubble made an even more astounding discovery. He and his colleague Milton Humason gathered the key evidence that opened the door to proving that the universe was expanding, with the galaxies continually riding the wave outward. Space-time was in motion! Half the work to reach this startling conclusion was actually performed on an Arizona mountaintop a decade earlier by Vesto Slipher, a Lowell Observatory astronomer whose vital role in arriving at this finding is now largely forgotten outside the halls of academia. Such is the power of Hubble's legend. It pushed the contributions of others into the shadows as the years progressed. This book intends to shine the spotlight once again on the entire cast of characters who contributed to revealing the true nature of the universe and laid the groundwork for Hubble's success.
Knowledge of the cosmic expansion was a transforming event. It allowed astronomers to escape the confines of their home galaxy, letting them explore a far larger cosmological vista. The Milky Way was now fleeing outward, giving theorists free rein to contemplate the universe's very origin. They mentally put the cosmic expansion into reverse and imagined the galaxies drawing closer and closer to one another, until they ultimately combined and formed a compact fireball of dazzling brilliance. In this way, they realized that the universe had emerged in the distant past from an enormous eruption—the Big Bang. No longer was our cosmic birth a matter of metaphysical speculation or a biased whim; it had become a scientific principle that could be tested and probed.
This new cosmic outlook came about through a unique convergence—the perfect storm—of sweeping developments. Not only did a burgeoning economy provide the money—and new technologies the instruments—to make these discoveries, but newly introduced ideas in theoretical physics supplied some answers. No less a scientific figure than Albert Einstein had arrived on the scene with a novel theory of gravity that provided a unique explanation for the universe's bewildering behavior.
A dynamism entered into the universe's workings. Einstein's equations introduced the idea that space and time are woven into a distinct object, whose shape and movement are determined by the matter within it. His general theory of relativity anticipated the universe's expansion and turned its study into an intellectual and theoretical adventure. Early globetrotters had crossed the oceans in search of terra firma—solid land, new continents—previously unknown to them and ready for exploration. With his relativistic vision of space-time as a pliable fabric that can bend and stretch, Einstein allowed astronomers to recast the ancient search into a quest for cosmos firma. Glued together by the genius physicist, space and time became cosmic real estate to be appraised, mapped, and scrutinized, with Hubble serving as its first surveyor.
Hubble eventually summarized his cosmological findings in a work titled Realm of the Nebulae, which is part history, part college textbook, and part professional memoir. This book was labeled a “classic” by his peers at the very time it was published in 1936. And Hubble's initial take still holds up in its broad outline. “[His] picture differs from today's only in details,” Caltech astronomer James Gunn noted decades after its publication. “One looks through the pages almost in vain for things that are known to be wrong. One finds a few…[but] we still determine the distances of the nearest galaxies by methods described [by Hubble]. We still mostly use Hubble's classification scheme. We still pay a great deal of attention to the questions Hubble asks.”
However, there is one glaring exception to Gunn's statement. Although Hubble's name is now strongly attached to the discovery of the expanding universe, he was never a vocal champion of that interpretation of his data. That was because there were other hypotheses in play in the 1930s and 1940s. Hubble was reluctant to choose sides, at a time when his newly mined data and Einstein's theory were so fresh. Hubble always coveted an unblemished record: the perfect wife, the perfect scientific findings, the perfect friends, the perfect life. His observations that the galaxies were fleeing outward were to him always apparent velocities. He wanted to protect his legacy in case a new law of physics sneaked in and changed the explanation. So far, it hasn't.
Hubble was lucky in a way. The Hubble Space Telescope could easily have been given another name had certain events turned out differently: if someone had not prematurely died (Keeler), if someone else had not taken a promotion (Curtis), or if another (Shapley) was not mulishly wedded to a flawed vision of the cosmos. The discovery of the modern universe is a story filled with trials, errors, serendipitous breaks, battles of wills, missed opportunities, herculean measurements, and brilliant insights. In other words, it is science writ large.