by Paul R. Spitzzeri
Among the many elements of the rise of greater Los Angeles as a major American metropolitan region during the early 20th century, there are the usual recognized landmarks: the burgeoning oil industry, the rise of motion pictures, industrial development, and the steady march of suburbia, though agriculture was still an important part of the local economy during the first few decades of the century.
Not as readily recognized because its financial impacts were negligible, but critical to the broadening of knowledge in the exponentially expanding world of astronomy was the establishment of the Mount Wilson Observatory. A prior post here covered some of the history of the outpost atop the peak in the San Gabriel (then often referred to as the Sierra Madre) range above Pasadena, specifically during the 1920s when Edwin Hubble achieved fame for his work there.
This post takes us back to the earliest years of the Observatory’s operations and an article in the February 1909 issue of Sunset, the magazine established a little more than a decade prior by the Passenger Department of the Southern Pacific Company, the railroad behemoth that founded the journal to promote tourism in the many areas of the western United States served by the firm. Today, Sunset is a lifestyle magazine with an emphasis on homes, gardens, food and travel, but, 115 years ago, there were poems, stories, articles on current events and, elsewhere in this issue, several articles related to China.
The article, titled “In Galileo’s Footsteps,” consisted of three parts: ”Opportunity,” written by Alexander McAdie of the United States Weather Bureau; “Achievement,” penned by the Observatory’s founding astrophysicist George Ellery Hale; and “Equipment,” by Stanley Du Bois, a correspondent, critic and traveler. McAdie ran the San Francisco office of the bureau and was also vice-president of the Sierra Club, while later he was a professor of meteorology at his alma mater, Harvard University.
He noted that Galileo Galilei was born just over two decades after Juan Cabrillo sighted California and that, around the time that Jamestown was established in Virginia, the great Italian scientist created an early version of a telescope. Through this instrument, he noted Saturn’s rings, Jupiter’s moons, the phases of several planets and observed the motion of planets around the Sun, postulated by Copernicus. McAdie added,
Many other things did Galileo; but to Californians, because of their pride in the work now being done at Mt. Wilson, the most interesting of all [his] advances was the discovery of spots on the sun . . . Little did Cabrillo think when he discovered [?] California, and little did Galileo imagine when he invented the telescope, that in the years to come, on the summit of one of the Sierra Madre, there would be a great observatory devoted solely to the study of solar phenomena. It is a genuine tribute to California climate and to the steadiness of the air over our western hills, that of the whole world here should be the site selected for the installation of the greatest telescope that modern science can construct.
With the work of Hale, moreover, a mammoth “spectro-heliograph” would provide photographs of spots on the Sun, while also “analyzing the structure of the ‘whirls’ [storms] at all levels in the sun’s atmosphere.” These images also demonstrated how massive the Sun is, but also reminded those studying it in 1909 that there were unanswered questions that the work of Hale and his associates sought to answer.
McAdie identified three areas of inquiry: measuring the radiation of heat and energy from its surface; what was in the atmosphere of the Sun; and its history and evolution. He continued that “the Mount Wilson Observatory is the premier observatory of the world” and that “some of the most interesting discoveries are those of the present year” with the detection of atmospheric currents, the attraction of hydrogen by sunspots, and vortices with magnetic fields.
He also observed that “the results obtained by observations are tested in the physical laboratory at Pasadena,” at what was then called the Throop Polytechnic Institute, now the California Institute of Technology for confirmation or modification. McAdie further wrote that “in this respect also it is believed that Mount Wilson leads the world, the combination of observatory and laboratory making possible the determination of the truth of existing theory, as well as foreshadowing future discoveries.”
Another important point raised was that, unlike other stars that were then too distant to appear as anything other than points in the sky, the sun showed as a disk in existing telescopes. It was added that there were other “suns like our own and therefore what we find out about our own star, the sun, will be the basis for our studies in stellar evolution.” From this, McAdie concluded that “this is the ultimate problem of all, the evolution of the universe” and beholding this foundational question “one stands appalled at the stupendous task.” Rather than be overwhelmed by this puzzle, though, he exhorted “let us glory in the fact that the mind of man can reach out beyond the finite limits of this earth.”
For his part, Hale began his short essay with:
The purpose of the Mount Wilson Solar Observatory is to study the life history of stars; how they are formed from nebulae, what changes occur as the condensing gaseous mas passes through the earlier stages of stellar life, what are the signs and conditions of maturity, old age and death.
He observed that nebulae resembled the clouds of Earth’s atmosphere, but there were also flames pushed by winds, what looked like planets, and what Hale considered most important, “enormous spirals” that proved challenging in terms of understanding any changes in their structure because of the 93 million mile distance.
The astrophysicist continued that, having the 60-inch reflecting telescope meant that “it should be possible to secure excellent photographs of these spirals,” which, compared over time through imaging, “may show that changes are in progress.” It was also hoped that the instrument would help better understand the nebulae through photography as well as “spectroscopic analysis of their light.” Having spectroscopes, moreover, allowed for the intensive analysis of the chemicals, motion, pressure and temperature in the composition of stars.
Hale expressed the view that spectroscopes and telescopes would reveal the development of the history of stars in the composition of the chemicals involved, variations in temperature, and, more importantly, because of the great power of the former instrument, the first real understanding of what variations there were in stellar atmospheric pressure. Combining research on nebulae, stars and the Sun for the past three years, it was anticipated that the understanding of the latter “will be continued and extended” and, as McAdie wrote, knowing more about the Sun would allow for “the interpretation of stellar problems” more broadly.
Echoing his colleague, Hale reiterated the importance of having the Throop laboratory readily at hand, as he noted, “here, at the high temperatures of electric furnaces, or in sparks or vacuum tubes or flames, the conditions observed in the heavens are experimentally imitated.” For example, material in sunspots, like iron, could be replicated with the sparks generated between very powerful magnets at the lab. This led the astrophysicist to end with:
In this way the evidence favoring the existence of a magnetic field in sunspots, which was furnished by solar observations made on Mount Wilson, has been confirmed and placed beyond all doubt.
Du Bois celebrated the installation of the 60-inch telescope as “a great event in scientific and popular astronomy” and as a culmination of the evolution of telescopic research from Galileo forward that meant that current instruments “reveal to the astronomer of to-day worlds and conditions which to the ancient astronomers were only a dim dream.” The recent challenge was to get past the limitations of refraction and the loss of light due to absorption by the lenses and it was noted that larger telescopes and their lenses was not a solution.
Even the best lenses lost up to 45% of the light passing through them, but, in 1884, Andrew A. Common developed a 36-inch reflecting instrument, with a silver film used to limit loss of light, while the new technology meant that the amount of light lost did not correspond to the larger sizes of glass used. The next major advance was by George W. Ritchey, a Chicago optician who, at his own expense, came up with a 24-inch reflector. Hale, then head of the Yerkes Observatory southeast of Milwaukee, learned of it and hired Ritchey to join him there.
It took some time to work out the mounting of the glass, but “this done, the results obtained were so marvelous and so satisfactory that it was at once determined to construct a much larger one,” this being the 60-inch telescope. A large amount of money was raised and the lens made near Paris, with grinding taking place at the Yerkes facility, with many hurdles in working with the 2,000 pound piece of glass with respect to maintaining the desired shape for proper reflection. A case weighing several tons was constructed to keep the glass in place with levers and weights keeping the optimum pressure on the lens, worth some $50,000.
The next issue was location, as DuBois commented,
a place was sought which should be free from fogs and clouds, from extremes of heat and cold, and also from wind currents, which are of themselves distracting to astronomers, but often carry with them more or less dust. It was also desirable to locate it where it would be reasonably convenient to transportation facilities and civilization. All this being taken into consideration, it was agreed that the summit of Mount Wilson more nearly met all the requirements than any other point. Here was stone and timber [for building] . . . water was to be had . . . [along with] the large percentage of cloudless days and nights.
The Mount Wilson Trail, built by namesake Benjamin D. Wilson (who came to Los Angeles with the Rowland and Workman Expedition of 1841) for hauling timber, was used for the carrying of hundreds of tons of cement and iron “mostly on the backs of burros,” but the larger issue was how to convey several hundred tons of machinery for the telescope. This involved widening the trail to a ten-foot width, including blasting away portions of the mountainside, constructing supports and reducing the steepness of the grade at intervals—this work, done mainly by Japanese laborers, taking almost a year.
At Pasadena, a machine shop was built which received its power from “a mountain waterfall seventy-eight miles away” and the facility was where, with custom designs and processes, the mechanical components of the telescope were made and installed. The grinding of the glass required a nearly completely uniform temperature and the process, also involving intricate shaping and polishing, took three years, with some days only allowing for five minutes of work to avoid disturbing the molecules.
Du Bois added that the main lens was in a concave/parabolic shape with a depth of some three-quarters of an inch so that light rays were concentrated and undiffused, while five others were about sixteen inches in diameter, with three having convex/hyperbolic surfaces and the others having optical planes. With some exceptions of castings and shafts, all of the metal material was made at the Pasadena shop with some remarkable precise cutting involved. It was recorded that “although this is the heaviest telescope ever made,” it was easy to maneuver as it “is floated in a bath of mercury.” The focal length was noted as 25 feet and the dome 60 feet in diameter, both smaller than the famed Lick Observatory scope with its 36-inch lens, while the main glass was at the lower end, not the usual upper side.
Notably, the silver film was so thin that less of that material was used “than is contained in an old-time three-cent piece” for the 2,800 square inches of surface. Du Bois also commented that the workers were so careful in handling the lenses in the workshop that the floors were always kept wet and the crew wore white suits and headgear only utilized in the rooms “so that no particle of dust might scratch the polished glass.” He ended by noting that a special electric truck, with a carrying capacity of nine tons and motors for each wheel with a gas-powered dynamo, was built to haul the material at just one-and-a-half miles per hour. Moreover, a mule team was always ahead of the vehicle “ready to take hold if the power should fail.”
This article is a fascinating look at the construction of the the Observatory and its revolutionary telescope just after both began operation, helping to further the rapid advances of astronomical and astrophysical research, specifically with the Sun. Well over a century later, valuable work continues at Mt. Wilson, much of it unnoticed by the millions of people who lived within a short distance of the facility.