The Day We Found the Universe (5 page)

When an element is hot and glowing, it radiates its distinctive pattern of spectral colors. But at other times it can absorb those same wavelengths, which explains the origin of the dark lines that Fraunhofer found in the solar spectrum. Each element in the Sun's cooler outer atmosphere absorbs its designated colors, robbing the sunshine of those selected wavelengths before they arrive on Earth. The bright lines are simply the reverse of this process—the elements emitting those very same wavelengths of light as they fiercely burn. Either way—dark or bright—the pattern of lines indicates the presence of the element. Not until the early twentieth century, with the advent of atomic physics, did scientists come to understand this behavior as arising from the electrons in an atom jumping from one energy level to another, the atoms emitting bursts of light when they lose energy and gaining energy when they absorb the photons.

Astronomers quickly realized that, along with revealing a star's composition, a stellar spectrum could also tell them how the star was moving. In the 1840s the Austrian physicist Christian Doppler had surmised that the frequency of a wave, such as the tone of a sound wave or the color of a light wave, would be altered whenever the source of the wave moved. We've all heard the pitch of a siren rise to a higher tone as a police car or ambulance races toward us. This is the very effect that Doppler spoke of: The sound waves emitted by the screeching siren crowd together as they approach us, shortening their length and likewise raising the pitch. Conversely, as the police car pulls away, the sound waves stretch out, producing a lower pitch. In an analogous fashion, a light wave's length is shortened (gets “bluer”) when the source of the light approaches and is lengthened (gets “redder”) when the source moves away.

Astronomers, though, don't assess the overall color of a star or galaxy to measure its speed. That would be too difficult. They can more easily examine how the bright and dark lines in a celestial spectrum shift from their well-known laboratory positions. Depending on the object's motion, the lines can shift toward either the blue or red end of the spectrum. If a star or nebula, for example, is headed for us, its spectral lines move over toward the blue—that is, the lines get “blueshifted.” If moving away, the lines swing over toward the red and hence become “redshifted.” The exact velocity is pegged from the amount of shift in the spectral bands. Blueshifts and redshifts are nothing less than the speedometers of the universe.

Keeler had the eye of a hawk in measuring how the celestial light entering his spectroscope was separated into its component wavelengths, with each spectral line offering enticing clues. He was America's leading practitioner of this new technique, with some of his best work being done on measuring the speeds of nebulae within the Milky Way. In Latin,
nebulae
is the word for “clouds” or “mist,” exactly what these extended objects look like through a telescope. Some are roundish and were dubbed “planetary nebulae” in the eighteenth century by British astronomer William Herschel, who thought they resembled planets through his telescope. Today, astronomers know that such circular nebulae are the result of aging stars casting off their outer envelopes. Other nebulae, such as the renowned Orion nebula, are more irregular and diffuse, made luminous by the new stars being born within these great cosmic oceans of gas.

By the late 1880s, as Keeler entered his thirties and continued these celestial explorations, he faced a career crisis. He was eager to marry Cora Matthews, the niece of Richard Floyd, the superviser of the observatory's construction and president of the Lick Trust. The couple had first met on the mountain but could not tie the knot right away because Lick officials would not provide them adequate housing at the observatory once married. There was also Keeler's growing dissatisfaction with director Holden, a tyrannical and humorless man who often tried to share credit for some of Keeler's discoveries and at times ordered the young man to carry out observations he was not eager to do. It was said that Holden, given his West Point background, ran the observatory “as though it were a fort in hostile territory,” barking out commands like a general under seige. On top of that, there was the tiresome isolation atop the mountain, with few opportunities to escape to the city and engage in a fuller social life. “I am a human being first and an astronomer afterwards,” Keeler confessed to a friend.

Faced with these growing concerns, Keeler began networking among his astronomer contacts and in 1891 secured the directorship of the Allegheny Observatory, a return to his first place of employment. His old boss Langley had by then moved to Washington, D.C., where he served as secretary of the Smithsonian Institution and was beginning work on his lifelong dream to successfully launch a flying machine.

In terms of telescope power, Keeler's transfer to the Allegheny Observatory, situated on a hill across the river just north of America's steel capital, was a giant leap backward. The weather was poorer, the air was tainted with Pittsburgh's industrial smoke, the atmosphere was more turbulent for viewing, and the observatory's main telescope was a 13-inch refractor, far smaller than Lick's 36-incher. Yet, in some ways it was a blessing. The constraints forced him to focus his astrophysical studies on such objects as nebulae, a less trendy territory and hence riper for discovery. Because of their larger size, compared to stars, the fuzzy objects could still be adequately examined, even with a smaller scope. Moreover, astronomical photography had become more efficient and convenient, allowing him to build up exposures and see spectral details he could not see before with his eye alone. He doggedly tracked down every new advance in spectroscopic and photographic equipment in hope of offsetting Lick Observatory's advantages. The experience, though exhausting, only enhanced his astronomical abilities.

From his new post in Pennsylvania Keeler eventually made headlines worldwide. He had been using his spectroscope at Allegheny to measure how fast some of the major planets, such as Venus, Jupiter, and Saturn, were rotating. Based on a method already used to gauge the Sun's rotation, Keeler knew that a spectral line in light arriving from the edge of the planet rotating toward us would be shifted toward the blue end of the spectrum; this same line would shift equally the other way, toward the red, when emanating from the edge, or “limb,” of the planet moving away. Along the way, Keeler cannily comprehended that he could also peg the velocity of Saturn's rings with the very same technique.

In 1856 the famous Scottish theorist James Clerk Maxwell had theoretically proven on paper that Saturn's rings were not solid, akin to a phonograph record, but rather composed of innumerable particles, little “moonlets” circling around in independent orbits. Saturn's immense gravitational pull, avowed Maxwell, would have torn apart any sort of solid disk. If true, then Newton's law of gravity would predict that the myriads of tiny chunks located in the outer part of the ring would be traveling slower than those closer in, nearer to Saturn's gravitational grip—just as Pluto, far from the Sun, orbits at a slower velocity than the solar system's inner planets.

A spectrum, taken on the night of April 9, 1895, gave Keeler the direct proof. The spectral lines indicated that the ring's particles were circulating around Saturn according to the rules of Sir Isaac. The ring was not a rigid plate after all. Within days, Keeler dispatched a report to the newly established
Astrophysical Journal
, and a torrent of newspaper and magazine articles about his triumph followed. His scientific reputation rose sharply, especially since he had devised such an elegant and simple test of Maxwell's conjecture, one that other astronomers knew they could have done years earlier, if only they had been so clever.

While Keeler was busy with Saturn, Lick director Edward Holden was scheming to expand his astronomical empire, by bringing the historic Crossley reflector to the observatory—a telescope first constructed by a Londoner, Andrew Common, in 1879. He had built it to test out some design ideas, even earning a gold medal from the Royal Astronomical Society in 1884 for the fine photographs taken with it, including the first image of a nebula, Orion. Its mirror was a glass disk, three feet wide, coated with a thin layer of silver, a relatively new development in reflector technology. Early telescopic mirrors had been made out of metal, which readily tarnished and easily got out of shape. Widespread use of reflecting telescopes did not occur until instrumentalists in the mid-nineteenth century learned how to cast large and sturdy glass mirrors, with the glass first ground and polished into an ideal shape for focusing the light and then its surface coated with a thin surface of metal for high reflectivity.

Satisfied with his design, Common was soon eager to make an even bigger scope and sold his award-winning instrument in 1885 to Edward Crossley, a wealthy textile manufacturer who moved it to his estate in Yorkshire. But after a few years, Crossley sadly deemed the English countryside unsuitable for decent astronomical observations and put the reflector (as well as the special dome he had built for it) up for sale in 1893.

Original Crossley telescope at the Lick Observatory
(Mary Lea Shane Archives of the Lick Observatory, University Library
,
University of California-Santa Cruz)

Holden may have been a poor astronomer but he was a powerful persuader. He convinced the English tycoon to donate his entire assembly for free to the University of California, which now owned and operated the Lick Observatory. Once the parts for the scope and its dome arrived in 1895, Holden pushed mightily to get the system reassembled as soon as possible. As the dome was reconstructed on the edge of Ptolemy Ridge, a time capsule was inserted into its wall. The small zinc box, still hidden away, contains a letter from Crossley, the calling cards of the Lick astronomers then on staff, a Lick visitors pamphlet, and a set of U.S. postage stamps.

Lick astronomers, however, were not at all interested in this new addition to their astronomical arsenal. One disgruntled staffer declared the equipment “a pile of junk,” after some halfhearted attempts were made to put the telescope back into working order. For many, the Crossley was the last straw in a battle that had been raging for a very long time: a face-off between the director and his workforce. Tired of Holden's militaristic commands, hogging of the spotlight, and endless interference, the staff eventually revolted. Holden (described by Lick employees behind his back as “the czar,” “the dictator,” “that humbug,” “an unmitigated blackguard,” and “the great I am”) was forced to resign. The university regents had lost confidence in him. Holden took his final ride down “Lick Avenue,” the mountain's dusty road, on September 18, 1897. Only one person, a young assistant, went out to say good-bye.

Keeler, by this time, was getting restless back in Pennsylvania. The mighty iron and steel mills in the Pittsburgh area were expanding, dirtying up his sky even further with the black soot of their coal fires. And, though he was noted as the country's most able spectroscopist, Keeler was more and more hampered by his tiny 13-inch refractor, a telescope originally built forty years earlier for amateur viewers. Its aging lens absorbed the higher wavelengths of light—blue and ultraviolet—which limited him to work primarily in the yellow-red region of the spectrum. To make matters worse, his former assistant at Lick, William Wallace Campbell, had arranged for Lick to get a new spectrograph (an instrument that not only disperses the light into its constituent colors but records the spectrum as well). It was being built in Pittsburgh, and Keeler had agreed to test it out before it was shipped to California. The experience made him realize that it would soon be impossible for him to compete with Lick, especially since a great economic turndown, a depression that started in 1893 and lasted for years, had dried up sources of funds to expand his facility and raise his salary. Holden's firing came at an opportune time for Keeler.

In the search for Holden's replacement, a number of names came into play, including the venerable Simon Newcomb, George Davidson, who had originally coaxed Lick to fund the observatory, and several senior Lick astronomers. Keeler was added to the mix as a dark horse but soon became a favorite among the more progressive university regents. They wanted someone young, someone with impressive credentials, who would help the University of California achieve first-class status. Keeler won the vote by 12 to 9, Davidson coming in second.

Hearing that they might lose their director, Allegheny Observatory supporters launched a last-minute effort to raise enough funds from the Pittsburgh elite to build a new edifice for Keeler, one equipped with an imposing 30-inch telescope. Poems were even written and printed in local newspapers to boost the cause:

“Stay with us, Keeler,” so they say,
“And twice as much as Lick we'll pay.”
Wherefore perchance he'll not resign
But stay and keep our stars in line.