We Visited ALMA, the Telescope That Can Hear the Big Bang
published during a waxing crescent moon.

From the summit of the volcano, the people and vehicles below on Chajnantor Plateau seemed to swarm like ants. Two vehicles in particular caught Danilo Vidal’s attention—enormous yellow behemoths with rows of monstrous tires, more like moving launch platforms than trucks. With one eye on the group of climbers he had led to the top of El Toco, some 18,000 feet above sea level, Danilo watched with curiosity as the two giants took turns creeping up and down the reddish dirt path, bearing their ghostly white cargo.

For years, the antennas kept coming. Each time Danilo guided a tour group to a nearby peak, he kept count of the massive, spotless dishes, each carried up the mountain by the behemoths and deposited onto the flat plain of Chajnantor. As their numbers grew, the antennas began to form a cluster of white silhouettes against the Martian-red soil, their dishes aimed into the blue Chilean sky.


Danilo Vidal, PR Coordinator. Like many of the Chilean staff, a love of the stars and mountains brought Danilo to the nearby town of San Pedro, and eventually to work at ALMA. Image Credit: Dave Robertson

What was being built, exactly? Danilo wondered. And why on Chajnantor, of all places—a wholly foreboding slab of land on the wind-battered Andean high plains, located in the Atacama Desert, also known as the driest place on Earth?

A trained mountaineer, Danilo dealt with the physical perils of high elevation on a regular basis—which made the massive construction underway at Chajnantor all the more perplexing. “I was mystified how they were able to do it,” Danilo told me. ”You have to build this entire thing at 16,500 feet, five degrees Fahrenheit, with really strong winds. It would be hard enough doing it at sea level. I needed to know how they could make it work.”


One of two antenna transporters, named Otto and Lore, built especially to move ALMA’s massive antennas. Each transporter has a surface area of a tennis court and a top speed of 20 km/h. Image Credit: Dave Robertson

Six years later, Danilo is on Chajnantor, leading my partner, Dave Robertson, and I among the giant antennas of the Atacama Large Millimeter Array, or ALMA, and the two of us are hard pressed to uncover any secret that might have made the construction of the world’s most extreme radio telescope any easier. With our jacket hoods up against the ceaseless wind, we huff from portable tanks of oxygen to stave off altitude sickness. We shout to make ourselves heard. Every so often, ALMA’s antennas suddenly pivot without warning.

Juliane Götz, a member of the Berlin-based artist collective Quadrature, recalls visiting the array for research and feeling its mysterious vibes: “The antennas move without warning, making a beautiful sound as they turn. You feel perplexed. What are they looking at?” The answer is that they are looking everywhere, following a punishing schedule of international astronomy projects, constantly re-aiming to capture photons from remote corners of the cosmos—even some thought to have emanated from the Big Bang itself.


A view of the array on Chajnantor Plateau in the Atacama Desert. At 16,400 ft, Chajnantor is roughly the same elevation as the base camp for climbing Mount Everest. Image Credit: Dave Robertson

It is challenging enough just to get to Chajnantor. Three days prior we flew from New York to Santiago, then from Santiago to the bustling northern mining city of Calama, then drove to San Pedro de Atacama in a rental car. Our ALMA visit began earlier that day in the modest medical center within ALMA’s main building, the Operations Support Facility, located at 9,000 feet. We are here to pass a medical exam. If our heart rates and blood pressure are up to snuff, the medical staff will permit us to venture up to Chajnantor, and see with our own eyes the sixty-six antennas that are peering further into the very origins of the universe than ever before, sensing radio waves from the very beginning of time. Fail, and we’ll be kept at the OSF, and given roughly the same access granted to tourists: a barrage of promotional videos, followed by a cursory tour of the facilities.

With my love of coffee and salty foods, I just barely pass the test, while Dave, an avid cyclist and footballer, passes with flying colors. Then we pile into a van with Danilo at the wheel and begin the drive up. Per international restrictions, Danilo must wear an oxygen tube in his nose on the entire drive, and periodically check-in via walkie-talkie. Access to Chajnantor is highly regulated—on the first day of your weekly shift as an employee, you’re not allowed up at all, and only in increasing two-hour increments on every day that follows.

I try to imagine being the first scientist to find Chajnantor. To circle this spot on the map and have the guts to tell an international committee featuring space agencies from six nations that it’s the place to build ALMA, at a cost of over one billion US dollars. The desolate, otherworldly Atacama seems tailor-made to serve as this story’ s backdrop. The Atacama is the driest non-polar desert on the planet: twenty times drier than the Sahara, and fifty times drier than Death Valley. Some spots have never recorded a single drop of rain. With very little water vapor to create clouds or scatter photons, the Atacama offers astronomers unparalleled access to the stars.


ALMA is built in Chile’s Atacama Desert, the driest non-polar desert in the world. Incredibly low water vapor and high elevation have made the Atacama a mecca for radio astronomy. Image Credit: Dave Robertson

The vast Atacama is strewn with messages from the past.

The dryness of the Atacama allows the past to surface in the present. From the sky, light from millions of years ago strikes ALMA’s antennas. In the soil, traces of our human past lie undisturbed by moisture. In Desert Memories, his travelogue of the Atacama, Chilean novelist and playwright Ariel Dorfman observes that “it is in the desert, in this driest of dry dwelling places, that….[so many] secrets of the past can be uncovered because, quite simply, in a place like this they have never been truly lost. They have merely been waiting for the right hand, the right eye, the right questions, to bring them back to life.”

The vast Atacama is strewn with messages from the past—messages that Pablo Neruda, Chile’s most beloved poet, described as “submerged and forgotten paper.” Scratch the desert’s surface, and you encounter remnants of primitive civilizations, including their markings and their own mummified bodies. You may also encounter the remains of victims of Augusto Pinochet, the dictator whose military coup in 1973 was supported by the United States and who terrorized his country for a generation.

In 2010, the same year that Danilo first saw antennas popping up on Chajnantor, Chilean director Patricio Guzmán released the documentary Nostalgia for the Light, in which he sought to connect ALMA’s cutting-edge research to find our cosmic origins to the plight of local Chilean women who still roam the Atacama looking for traces of their siblings—members of “The Disappeared” whose bodies were clandestinely relocated to this wasteland by Pinochet’s men. One woman, miraculously, digs into the suspected site of a mass grave and manages to locate her brother’s shoe, foot inside. Whether among the sand dunes or the stars, in the Atacama, the search for the past is endless. It takes love, it takes obsession, and it takes sacrifice.


Each of ALMA’s sixty-six antennas weighs over 100 tons, yet its radio-sensitive surface is thinner than a sheet of paper. Image Credit: Dave Robertson

With its remoteness and its secrets, the Atacama has a way of pulling you in. Originally from Santiago, Danilo had come to San Pedro, the closest town to ALMA for miles, with a plan to visit for ten days. He never left. “It was like ‘Hotel California,’” he tells me, “but the good version.” A thousand years after San Pedro was carved out of the harsh landscape by the pre-Incan Atacameños, the village is still a desert oasis with cobblestone streets and adobe walls—although now its streets are lined with souvenir shops and independent travel guides hawking visits to nearby attractions like high-mountain geysers and salt flats. In addition to its peaceful charm, it was San Pedro’s location that got Danilo hooked— a stone’s throw from the towering volcanoes and mountains of the Andes.

One day, after years of watching ALMA being built from nearby peaks, Danilo got a phone call. On the other end was someone wanting to know if Danilo, with his expertise in tour guiding and high elevation, would be interested in working there. Danilo assumed they were joking. He eventually accepted a job offer, knowing that he would be mixing with scientists and engineers of the highest caliber, from all over the world—scientists like Rüdiger Kneissl, a clean-cut, well-traveled Bavarian astronomer, whose work lies at the heart of ALMA’s mission.

Having cut his teeth doing radio astronomy at Cambridge, Kneissl leads ALMA’s efforts to scan the vast cosmic desert for signals from the very beginning of time—particles that scientists believe are left over from the Big Bang. Kneissl lives in Santiago with his family and commutes once a month to ALMA, where he can be on hand as the latest data comes through on the Cosmic Microwave Background—considered to be the oldest light in the universe, and proof that the “Big Bang” was real. As Yale astronomy and physics professor Priyamvada Natarajan calls it, the Cosmic Microwave Background, or CMB, is “the Rosetta stone of the universe,” the “key to deciphering the origin of the cosmos.”


Nelson Tabilo (L) and Bonifacio Gonzalez (R), electronics technicians, seen in the ALMA receptor lab, where they obsessively polish and maintain each antenna’s radio receptors. Image Credit: Dave Robertson

Aim an optical telescope into the spaces between stars and galaxies, and you won’t see much of anything. Use a radio telescope, which scans at electromagnetic wavelengths some thousands of times longer than visible light, and you will register a faint hum. This is the same hum that two Bell engineers, Arno Penzias and Robert Wilson, heard in 1964 when they were busy trying to innovate means of bouncing radio signals off balloons.

Try as they might, Penzias and Wilson could not isolate the radio frequency they needed—a strange static kept interfering. Eventually, after much debate, the scientific community concluded that this noise was actually the sound of the Big Bang itself—the leftover bits of radiation that had flown out of the Big Bang’s fireball but never coalesced into atoms or matter. For their accidental discovery, Penzias and Wilson won the Nobel Prize.

Essentially leftover stardust, the Cosmic Microwave Background is certainly not as dramatic or attention-grabbing as other cosmic bodies, like a supernova, or a black hole. The CMB is optically invisible, and incredibly low energy. And it is everywhere. In total, energy from CMB radiation exceeds that from all the starlight in all the galaxies combined and accounts for 99 percent of the total radiation in the universe. Not only, as is sometimes said, are we humans made of stardust, so is most of the cosmos.

Kneissl’s most recent work at ALMA shows how tracking the CMB has multiple other research benefits as well—it can help us locate other cosmic bodies, like giant galaxy clusters. ALMA can observe photons from the CMB being affected by massive clouds of electrons, and thus identify the location of a cluster. “You see holes in the sky,” Kneissl explains. “The Cosmic Microwave Background is only three degrees Kelvin, which is extremely cold, and gas from a cluster is very hot, at millions of degrees. The CMB’s photons get a net increase in energy, and so the spectrum is shifted.”

As often happens during our visit to ALMA, this description of the telescope’s capabilities is overwhelming to me. I feel a bit disoriented, and it’s not the altitude, but ALMA’s extremes of scale, piling up in my mind. The oldest noise in the universe. Signals from thousands of light years away. Antenna dish surfaces thinner than a sheet of paper. Equipment that’s constantly frozen to near-absolute zero. A billion and a half-dollar observatory that’s one of the highest-altitude human structures on the planet. None of it for profit, or for warfare, but for the endless pursuit of understanding our place in the universe.


Vasco Cortez, systems engineer. Having been a part of ALMA nearly since its inception, Vasco has helped grow the array team from a scrappy start-up atmosphere to a highly complex organization. Image Credit: Dave Robertson

Strewn with vacuum pumps, cryogenic chambers, and radio frequency simulators, ALMA’s receptor lab looks every bit the mad-scientist warren you might imagine, except exceptionally clean, like a hospital. A compact, winsome electronics technician in his early sixties, named Bonifacio Gonzalez is lecturing us on the finer points of a damaged radio receptor. With his good charm and geeky enthusiasm, Bonifacio evokes Billy Crystal in a lab coat. As Bonifacio shepherds us through the lab, ALMA’s efforts become clearer to me in a new way. The entire observatory is fueled by a gigantic fight against entropy. It is an interminable battle because entropy is found basically everywhere in the universe, in the form of radiation, only some of which is useful at any given time, depending on what you’re looking for.

Everything radiates, even you and me, giving off energy across the electromagnetic spectrum: heat, visible light, x-rays, gamma rays, ultraviolet light, infrared light, and of course, radio waves. To listen in on incredibly faint radio waves sent from across the universe, ALMA’s team obsessively maintain, calibrate and polish their instruments, at a magnitude unseen anywhere on earth. Imagine constantly dusting off the needle on your record player, so the sound is clearer, only it takes over 600 people from 20 countries working in shifts, at an altitude roughly equivalent to Mount Everest base camp. All to ceaselessly block out the noise you don’t want from the noise you do want, the sliver of frequencies on the electromagnetic spectrum that may contain new shreds of evidence in humankind’s longest-running detective story.

The Eye in the Desert