The Great Dome
Before the early film impresarios set up shop here for the constant sunshine - a full decade, in fact, before Carl Laemmle’s 230-acre chicken ranch became Universal City - someone had already noticed the light in Los Angeles. That someone was George Ellery Hale, an astronomer from back East who had developed a way to photograph the sun. Hale studied the sun daily, so he needed good light. And in 1904 he built a big version of his spectroheliograph atop Mount Wilson, about 10 miles northeast of Los Angeles, to take advantage of the calm air and the 300 cloudless days the area gets each year. The site grew, with four more telescopes added over the next decade and a half, the last of which was the Hooker 100-inch - then the largest in the world, and the instrument with which Edwin Hubble discovered (or proved, depending on whom you talk to) that the universe was expanding.
I moved to Pasadena in 1981 when my father took a job at the Jet Propulsion Laboratory, and Mount Wilson has been with me ever since. It’s the tallest summit in our little stretch of Sierra Madres, and you can see it from the entire city. Since I was 14, it’s been framed right in the center of my bedroom window (I’m looking at it right now). My father is a physicist - to the aging crack about smarts that went, “What are you, some kind of rocket scientist?” he always responded, “Yes indeed!” - and he gave my brother and me an early start with the sciences. Next to our charts of the solar system, we had mural-sized posters of eclipses, Io’s angry volcanoes and Europa’s mottled tundra, with its zigzagging furrows. I was up on quasars, brown dwarves, pulsars, the date of Voyager II’s expected Saturn flyby. And I knew that Hubble made one of the most important cosmological discoveries, one that fundamentally changed our idea of the universe - even Einstein’s idea of the universe - right up there on Mount Wilson. There’s a canyon below the mountain, and right at the edge, hidden by a barricade of oleander, is a little platform where I liked to take girls in high school, not only because it was secluded but also because we could talk about the string of lights up on the mountain and how they gave us the universe that we know. Those lights blinked slowly over my first kiss.
Despite all this, I had never been to Mount Wilson until recently. Like most people, I assumed that the observatory no longer operated — that light pollution had rendered the telescopes ineffective decades ago. I am admonished about this on my first visit by Don Nicholson, the associate director of the Mount Wilson Institute, who explains that the Hooker and the other telescopes have been in daily use since they were built (except for an eight-year stretch when the Hooker was offline for lack of funding). A full staff continues to use the daylight to watch the sun; and the night sky, which filters through some of the world’s calmest air, affords what astronomers call good “seeing” - down to half an arc-second on some nights, a resolution that, as the convivial octogenarian Nicholson says, “makes other astronomers drool.” And lately, Mount Wilson has been home to some pioneering technologies that make the observatory as relevant as ever. Despite the smog and the encroaching city, Los Angeles still gives us a great sky.
The Mount Wilson grounds occupy about 40 forested acres atop a 5,700-foot peak that overlooks much of Southern California, from Mount San Jacinto to the Malibu hills. Its spot on the ridge is tight, almost precarious. From some points the crest becomes so narrow you’ll look south and find Catalina floating in the mist and then turn around to see the Angeles National Forest stretching off toward the Mojave Desert. From these places, the view due east is divided equally between a solid urban grid and empty wilderness.
The solar observatories on Mount Wilson are imposing towers, although the giant structures we see from the city are the nearby broadcast facilities. Together, the various spires and domes feel sci-fi: They give the impression, especially at night, of some kind of far-off research colony. People do live there, and for them there is a cluster of buildings that provides housing, a galley for cooking, and a library.
Dwarfing them all is the dome of the Hooker 100-inch telescope, which is settled on a north-facing, downward-sloping promontory that puts it out of sight of city lights. It looks like what we imagine observatories to be because it set the standard: a massive white metal cap, raised on a pedestal, with a wide arc of a door that opens to reveal the cage and optics that make the heavens visible.
The Hooker was finished in 1917, after three years of construction, and it’s built like a dreadnought - solid steel top to bottom, a massive complex of structure, supports and bulkhead doors. “They didn’t have finite element analysis back then,” Nicholson says as we enter the open floor of the observatory. “So they overengineered. They just worked it out on the back of an envelope and doubled the numbers.” The telescope weighs 50 tons and the dome twice that, and both are moving parts: While the scope swivels, the full range of the sky is reached by turning the entire dome. The reflecting element at the bottom of the scope is 9,000 pounds of wine-bottle glass from the Saint Gobain bottle works in France. It remains the largest solid plate mirror ever cast. All of this was hauled up the tortuous Mount Wilson Toll Road by burro and a few specially designed Mack trucks, which, as you’d expect of trucks built in 1917, often got stuck and required assistance from the donkeys and their drivers.
To the dismay of many visitors (including me), the Hooker, like all professional observatories since, doesn’t have an eyepiece. You can’t bend over, squint, and see Jupiter. The whole apparatus is guided electronically and mostly records data. But photographic images taken by Edwin Hubble more than 70 years ago were the basis for Mount Wilson’s most important scientific discovery. Hubble, with the help of his historically neglected partner, Milton Humason, used a spectrograph mounted at the top of the telescope to expose spectral images onto photographic plates. Over eight years, Hubble took thousands of exposures, which together revealed something extraordinary.
Hubble was measuring the distances and velocities of galaxies outside our own, and he found that all of them, in every direction, were receding from us. And the farther away they were, the faster they were moving. This relationship could be quantified, and the resulting number became Hubble’s constant. Until then, many assumed the universe was fairly static; that the firmament was fixed; that it was, had been, and always would be the same general size and shape. But Hubble proved that the universe was, in fact, expanding, and he could say how fast. One of the conventional ways to visualize the phenomenon is to imagine a balloon with dots all over it. When the balloon fills with air, the space between all the dots expands. No two dots are getting closer together. From the perspective of any one dot - or galaxies, in the case of the universe - all the others are moving away. The expanding-universe idea quickly led to the Big Bang theory: If the universe is getting bigger all the time, it must have been smaller before. In the beginning, then, it all started in one place, as one point, a singularity.
Today, technology has made Hubble’s photographic plates obsolete, but it is also giving the observatory a new lease on life. From the catwalk outside Hooker’s dome, you can see a few small silver domes poking out over the trees below. These are the components of a nearly finished stellar interferometer, which is an instrument that receives the light from multiple observatories and combines it into an image with the resolution of a hypothetical telescope that would be far too big to build. Interferometry is not new; there are many such instruments already, including an older one on Mount Wilson. But this new one, ã which should be fully functional this spring, will be among the world’s most powerful.
The aging Hooker, too, has been upgraded. Five years ago, it was outfitted with an adaptive optics system, which uses a deformable mirror and computers to monitor and correct in real-time blurring caused by light in the atmosphere. It undoes the stars’ twinkle to get a much sharper image. When this system is in operation, the Hooker lens will be able toget the same quality images as NASA’s Hubble Space Telescope.
Astronomers live differently from the rest of us. They are true night owls, sometimes sleeping through daylight entirely.
Anyone with a research project can rent the Hooker at $1,800 a night and make use of its improved capabilities. But when no one else is in, the telescope carries on the age-old task of mapping the night sky. That ongoing project, called “HK” for the spectrum in which the observations are made, is in its 21st year, and is less than half finished. One night, Jim Strogan is the telescope operator on hand, taking data on the calcium flux of about 60 stars. “Depending on the time of year, you can do more or less stars,” he says as he steps onto the telescope mounts to check something out. “You take data on each one for a few minutes, and then move on.”
Astronomers live differently from the rest of us. They are true night owls, sometimes sleeping through daylight entirely. Their world goes by sidereal time, with days that are 23 hours and 56 minutes and clocks that match ours only twice a year. They think about position in terms of declination and right ascension instead of longitude and latitude. They brave the elements and, in the case of Mount Wilson, the cougars that sometimes come out of the forest to forage.
And they don’t mind isolation. The act of astronomy is a lonely activity. The people who live on Mount Wilson call the dormitory building the Monastery. Nowhere does it feel more monastic than at the desk of the scope itself, where one or sometimes a few dedicated astronomers stay up through the night to study the sky. The place is cold, cavernous and - since the lights go out when the telescope is active - very, very dark. Only the scope operator’s desk is lit, the sole beacon in the enormity of the dome, except those dim lights coming in from the sky.
There is also no noise, or any sound at all, but for the Geiger counter–like crackle of a detector on the telescope that gives audio cues to the operator. (Each pop is one photon, so the more light, the louder the crackle; when you’re right on a star, the detector’s speaker really sputters.) When the operator is working, the place is an empty, dark metal cavity, alternately silent and filled with electronic hiss, and it can be downright spooky.
Nevertheless, it’s easy to see why people want to be there. Although astronomy is not very glamorous - there are few “Eureka!”s and even Hubble’s discovery was built on others’ ideas - the appeal is in just being there. Strogan, for example, is a former auto mechanic and astronomy hobbyist who made it to the controls of the field’s Holy Grail, and for him there’s nothing like sitting for a night at the desk. “It’s tough living up here,” he says. “But the hard part is the downtime, when we’re not working. The fun is when we’re in here.” If you like the night sky, what better place to be? After all, when the dome opens, it really is just you and the heavens.
Which is an unavoidably impressive feeling. When I first see the door slide out to reveal the stars and an invading sliver of moonlight, I can’t help wondering if the mere sense of place influenced Hubble’s discovery: Looking out into that expanse, how could you not find an expanding universe? From Mount Wilson, it’s easy to see why the early narratives and rituals of civilization were rooted in the stars - they tell us a lot, especially now that we can add scientific understanding to superstition. The night sky, as those of us who seldom see it forget, invites both awe and interpretation. The first marvel is that the stars are really there, drifting around a universe indescribably far beyond our scale. More startling is that we actually know a lot about these things and can derive scientific, if not metaphysical, meaning from them.
This, for me, has always been the essence of Hubble’s discovery - that science constantly navigates the edge of fathoming the unfathomable. From lines exposed onto glass plates, we can deduce the nature of a cosmos that will always be outside our experience. Like relativity, or other great discoveries, that kind of intuition is sort of the cosmological equivalent of Hitchcock’s zoom-dolly shot: It puts us, uneasily, at the center of a center-less universe. Human intellect keeps revealing, in very certain detail, a universe that is indifferent to it. And that’s the rub: We learn ever more about a physical world that can be described but not fully understood. Every time science answers How? at a place like Mount Wilson, the Why? question only looms larger. As a friend rejoined after I tried to explain Hubble’s discovery: “Aah. So, the universe must be expanding, because the dots on the balloon are moving away from each other. But,” - he turned, leaned in, and added with a pointed finger - “then who’s blowing up the balloon?”
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