The Day We Found the Universe (2 page)
Read The Day We Found the Universe Online
Authors: Marcia Bartusiak
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. Spacetime 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 spacetime 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.
Setting Out
The Little Republic of Science
A
n immense continent of rock known as the North American plate slid inexorably over an oceanic slab of Earth's crust moving eastward. At the tectonic juncture, where the two gargantuan plates smashed together, the ocean floor plunged downward, the tremendous compression forging massive blocks of shale and sandstone. In due course some of this material lifted upward from its depths, relentlessly rising toward the sky to form the Diablo Mountain Range—two hundred miles of peaks and vales stretching from the San Francisco Bay southward along California's coastline. As if readying for a performance, nature sculpted the landscape that, millions of years later, offered astronomers a unique observing platform for their studies of the cosmos. Situated on the eastern edge of the Pacific, this lofty terrain became the perfect vantage point from which to make the first great discoveries in twentieth-century astronomy.
One noticeable peak in the Diablo Range, some forty miles from the sea, was known to early settlers as La Sierra de Ysabel. The first to record an ascent to its uppermost reaches were William Brewer, a geologist who worked on California's first complete geological survey, and Charles Hoffman, a topographer. Laurentine Hamilton, then a Presbyterian minister from San Jose, tagged along for the 1861 summertime adventure. While journeying over the lower elevations the men used mules but struggled over the last three miles on foot. With the two scientists burdened down by their heavy equipment, the minister was able to sprint ahead, pushing through the chaparral, mesquite, and thick groves of scrub oak that filled the mountain's furrowed sides like well-sprinkled seasoning. Upon reaching the summit, Hamilton waved his hat in the air and exclaimed, “First on top, for this is the highest point.” In honor of the achievement, Brewer graciously named the peak after his “noble and true” friend.
Within three decades Mount Hamilton was the site of a radical new endeavor in astronomy. Fueled by America's escalating wealth, “the public mind in this country is now directed to the importance of original scientific research,” wrote Joseph Henry, head of the Smithsonian Institution, in 1874 to the noted English biologist Thomas Huxley, “and I think there is good reason to believe that some of the millionaires who have risen from poverty to wealth will in due time seek to perpetuate their names by founding establishments for the purpose in question.” In the vanguard to answer that call was San Francisco entrepreneur James Lick, who funded the world's first astronomical observatory permanently established at high elevation. Before this, professional telescopes were routinely constructed in relatively lowlying areas, near major cities or on university campuses for easy access.
In 1888, from its commanding perch atop Mount Hamilton, the Lick Observatory began operating the largest telescope in its day, which featured a pair of imposing lenses a full yard wide to gather and magnify the celestial light. It was the same type of telescope through which Galileo first peered, one that directed the light through two aligned pieces of glass, but the diameter of the Lick instrument was a couple of dozen times larger. Its founder spared no expense to house this giant refractor. The massive building was designed in a classical style by Washington architect S. E. Todd. From afar, it appeared as if a European palace had been magically transported to the American West. Inside its dome, hand-carved moldings decorated the walls. The floors were curved wooden planks, polished to a sheen and stylishly following the shape of the circular dome. Tourists traveled on stagecoach for hours for a glimpse of this new wonder of the scientific world.
Unbeknownst to those visitors, though, the most innovative work at Lick was actually being done in more modest surroundings, about a quarter of a mile south of the showstopping telescope, at the end of a mountain spur known as Ptolemy Ridge. There, in a far smaller dome that resembles a quaint medieval chapel, James Keeler labored to put a reflecting telescope into operation, which used a silvered mirror instead of a lens to magnify its image. It was an instrument that everyone warned him would be nothing but trouble. Big-lensed refractors were the telescopes of choice in the late 1800s, but Keeler bravely broke from that tradition, establishing an approach in professional astronomy that eventually spread to every major observatory throughout the world.
