On the subject of Caltech’s underground lairs of legend, there is certainly no match for the famed steam tunnels, where student wall art—like ancient cave paintings—has intrigued viewers and marked the passage of time for decades. But there is another subterranean cranny on campus that, while less well known than the tunnels, is steeped in even more history. And within months, history is all it well may be.

We are speaking, of course, of the Robinson pit, located 82 feet below ground level, deep in the bowels of the Robinson Laboratory of Astrophysics. The shaft was built for Caltech cofounder and astronomer George Ellery Hale, and has served over the years as a venue for various forms of instruction and experimentation. But the residents of Robinson recently relocated across California Boulevard to the new Cahill Center for Astronomy and Astrophysics, and their former haunts, now nearly 80 years old, are slated to get a new lease on life as Caltech’s Ronald and Maxine Linde Center for Global Environmental Science.

The center will bring together faculty from chemistry, engineering, geology, and environmental science, among other disciplines, to work on issues related to global climate change. Reflecting this overall mission, Robinson will undergo an ambitious $32 million rehab into a “green” building, with the goal of achieving a Leadership in Energy and Environmental Design (LEED) platinum certification—the highest designation.

Aiming high, Caltech will go low—all the way down to that subterranean Robinson lair—as part of a plan to maximize energy efficiency. In an innovative approach to climate control, the Institute plans to fill the pit below the lowest basement with water that will be used to cool the building during those warm summer months. “At first, we weren’t sure if the walls could hold the water,” says Brad Smith, senior project manager for design and construction in Caltech’s Facilities department. “We looked at the original architectural drawings, and they showed that the walls of the shaft are two feet thick.” Smith, who’s charged with overseeing the ambitious renovation, says that the walls should be able to do the job once they’ve been coated with a sealant—a fluid-applied rubberized asphalt waterproofing, to be exact. With the shaft slated for a bold new role and the astronomers and astrophysicists now gone from Robinson, the time may come when no one on campus remembers the original purpose of Hale’s five-story solar duct. In fact, judging from a recent flurry of correspondence to Caltech News, its storied past may already be fading from memory.

The subject of the shaft materialized after a recent Caltech News (Volume 42, Number 4) published an investigative piece about a vanished campus sundial built by Hale’s longtime colleague, Russell Porter. We thought we might hear more on that subject from our readers, and indeed we did, as a sequence of letters on sundials published in the next issue attests. But one letter prompted us to embark on a whole new investigation.

The note in question came from Michael D. Decker ’69, who wrote, “This letter is stimulated by your recent ‘Sundial’ article. While taking the campus tour last year for Alumni Seminar Day, I asked the guide to remind me which building had the pit with the Foucault pendulum. I was told that was a myth, there was no such thing.

“Nonsense!” wrote Decker, who went on to get his MD from Rush Medical College in Chicago and is today the vice president for scientific and medical affairs and chief medical officer for the American division of Sanofi Pasteur, the world’s single largest manufacturer of human vaccines. (This was before the swine flu outbreak, so Decker had a bit of time on his hands.) “During my tenure (1964–69) I visited the pit countless times, taking a number of dates down there. The pendulum was suspended about 3–4 stories above the sub- (or sub-sub) basement floor, descending through a round or octagonal central space about 15–25 feet in diameter. The floor was marked with a compass rose/clock face. The pendulum was magnetically driven, as I recall. Access was via a small elevator. There was a small ‘mezzanine’ level, one or two floors before the base of the pit, onto which persons unknown had wedged a ratty old couch, for obvious purposes.

“After the tour, I prowled around for quite a while trying to jog my memory as to its location. I suspect that it was in the astronomy building, in space now occupied by the solar telescope, but that’s really conjecture. Can you track this down and restore this ‘myth’ to rightful ‘legend’ status?”

Despite the implications of certain of Decker’s recollections, Caltech News decided to fearlessly follow the story up. Before we take this racy chronicle any farther, however, we should inject a bracing dose of science by reminding any readers who may have forgotten that the Foucault pendulum was conceived by the French physicist Léon Foucault as a device to conclusively demonstrate the rotation of the Earth. In 1851, he suspended a weight with a 67-meter wire from the dome of the Panthéon in Paris. The plane of the pendulum’s swing, rotating clockwise 11 degrees per hour, proved Earth’s rotation beyond question.

But what happened in Paris roughly 150 years ago did not, evidently, stay in Paris. Was Decker correct in asserting that Caltech possessed a Foucault device of its own? Naturally, Caltech News turned first to Senior Archivist Shelley Erwin, who suggested referring the matter to “longtime denizens of Robinson.” We then consulted Marshall Cohen, professor of astronomy, emeritus, and Wal Sargent, Caltech’s Bowen Professor of Astronomy, who, in the midst of their move to the new Cahill Center, kindly supplied us with their reminiscences.

The name Edgar Allen Poe does not automatically spring to mind in connection with Caltech, but there are affinities nonetheless. America’s master of the macabre is generally associated with ravens (Caltech has at least two that annually nest in the window ledges outside Parsons-Gates), eccentric romantic attachments (readers might like to weigh in on this aspect), pits and pendulums, and, finally, the invention of the modern detective story. With the first two themes already represented on campus, this seemed like the ideal opportunity to bring the last two into the fold. Accordingly, not long after we heard from Sargent and Cohen, our Caltech News colleague, Barbara Ellis (whose husband, astronomer Richard Ellis, was part of the mass migration from Robinson to Cahill), asked Brad Smith if he would be willing to take us on an underground tour of the Robinson pit. Smith was kind enough to agree, and the following week found the four of us in the sub-subbasement of Robinson at the back of a newly vacated lab, standing in front of a 1930s-vintage Llewellyn elevator, complete with an interior sliding gate door and decorative metal gratings near the ceiling. The wooden door wheezed open, the four of us squeezed into a space about the size of a phone booth, and the ancient lift ferried us, Disneyland Haunted Mansion–style, three stories down, before creaking to a halt at what Smith assured us was the lowest point on campus.

The elevator doors opened, and, as we practically fell out of it, we found ourselves in a chamber not unlike a catacomb, measuring about 10 feet by 30. Smith flipped a switch, and two bare bulbs threw some yellowish light onto dingy gray concrete walls. As our eyes grew accustomed to our surroundings, we could see the shaft angling five stories upward, terminating at an octagonal opening onto what was presumably the roof. The room itself was dominated by a few large wooden tables, one of which held a dusty and bulky IBM “portable” personal computer, likely from the 1980s, and a large beaker of mysterious-looking liquid, which gave off an eerie green glow when Smith trained his industrial strength flashlight on it. For the record, we did not see a sofa or any poetic references to loaves and jugs. We did spot what appeared to be the remains of a Lord of the Rings Ditch Day stack—a sheet of paper showing a Xeroxed picture of either one very large ring (to rule them all?) or a very small dog collar and the words “Paths of the Dead: The ghost of a departed warrior will guide your next steps/Use the scraps with the letter board to decipher the clue.” As we contemplated these words, one of us spotted another circular object—a large, extremely dusty metal disk—and almost immediately after that, we saw a wooden crate, with the words “Accessories for the Foucault pendulum” scrawled across it. Inside we found a jumble of wires and metal parts. Another box held the lead bob, about the size of a honeydew melon, and it took two of us to lift it up for a better look. The disk, we now realized, was probably the compass rose or clock face mentioned in Decker’s letter. His recollections were apparently correct!

Brad Smith (above) shines his flashlight on an eerie-looking liquid at the base of the Robinson pit. To stand in that spot again, after the renovation that he is overseeing, Smith will have to don scuba gear. The elevator, shown below left, will be relocated and turned into a telephone booth in the renovated building.

With the pendulum mystery at least partly settled, Smith explained that the shaft was originally built to house a system of mirrors called a coelostat for Hale’s solar investigations. We then reboarded the elevator and rode to the roof of Robinson to look at the dome, which held the main equipment of the coelostat, still intact.

The primary mirror—42” in diameter—sat on an elaborate steel mounting structure, and was protected by a metal plate. Smith explained that during the days of solar astronomy research in Robinson, the mirror would be uncovered and maneuvered to intercept the sunlight, which it would then reflect to another, somewhat smaller mirror in the dome. The second mirror would send the sunlight down through the octagonal portion of the shaft to the floor where it would continue on the path described by Professor Cohen, until it reached the basement laboratory where the sunlight’s spectrum would be analyzed. (“The sun is a star—the only one we can observe up close,” Hale liked to say. Unlike other stargazers, a solar astronomer also wouldn’t have to miss any sleep during the night.) Smith told us that the coelostat had been in use until about 20 years ago.

To shed more light on the coelostat, we contacted Rich Goeden, a retired electrical engineer, who used to maintain the coelostat for a group of Caltech solar astronomers. “I would set up the hardware and make sure the stuff was set up for experiments,” he said. A few weeks after the tour with Smith, Goeden escorted us back to the shaft, and opened a door on the basement level to show us where the beams of sunlight would bounce off the final mirror in the instrument, and then be directed horizontally into a laboratory. Sitting on a granite slab, the dust-covered equipment in the room looked like it had been untouched since it was last used. In fact, it may have been last operated by Goeden himself, who deftly moved around the cramped space with great familiarity, pointing out where not to stand, unless one wanted to take the quickest way down the shaft. Goeden recalled that on at least one occasion, the equipment was used during an eclipse, in which the image of the sun was projected down a hall.

“The image of the sun was three feet in diameter,” he says. “You could see the sun spots.”

In an article that appeared in the Astrophysical Journal in 1935, Hale described in detail the entire coelostat and the shaft. However, it’s an open question whether he ever put the instrument to use, writing in that same paper that “the 75-foot spectrograph is not yet ready, and other apparatus is under construction.” Caltech archivist Erwin notes that Hale was ill from 1932 until his death in 1938 and says that she could find no evidence that he had ever conducted research with the instrument.

The days of astronomical investigation are over for Robinson, but the sun will still have a primary place there through both the solar energy research that will be carried on in the building, and the new role that will be played by the mirrors in the dome. A computer will automatically turn the dome and open its window during sunny days. The mirrors will beam the sunlight down the shaft, which will be painted a light color for better reflectivity, and windows cut into the shaft will allow natural light to stream into interior offices and labs. At the lowest basement levels, the mirrors will direct sunlight into custom light fixtures. Smith said that additional energy-saving measures, including the solar-shaft cooling system, will end up reducing by at least 60 percent the energy use of a similarly sized new building.

As for that film noirish elevator, Smith says that the cab will be removed and placed somewhere else in the building and turned into—what else?—a telephone booth. Will people put away their cell phones and return to the ancient technology of a pay phone? Or is the booth more likely to figure in Ditch Day stacks involving caped crusaders? The solution to that mystery may start to emerge near the end of 2010, when the Robinson rehab is scheduled for completion.

Does this story bring back memories of unrecorded, little-reported Institute lore and legends, or similar capers? How about other unsolved campus mysteries of general interest? If so, we’d like to hear from you. Write to hja@caltech.edu or to mrogers@caltech.edu.