I tense as the elevator cage rattles, quakes and trundles through the darkness as we head into the depths of the earth.
A mass of people in hardhats is packed in the cage as the slippery walls of the Yates Shaft at the former Homestake gold mine in Lead skim by. Some workers clasp lunch pails. The scent of something like coffee seeps from a thermos that could have been carried by miners who once worked these caverns in a hunt for gold.
But these weren't miners I joined on a trip down the deep shaft last week.
These were scientists, from the United Kingdom, Russia, Germany, the United States and all around the world. They're here at the Sanford Underground Research Facility to study, or attempt to define, alien particles such as dark matter and neutrinos.
A humid gust ruffles the scientists and my ears pop as we descend almost a mile below the earth's surface. I'm here, reporting for the Rapid City Journal, on a rare media tour of the lab, which I've reported on before but had never seen firsthand.
Getting here required driving from Rapid City into the snow-covered Northern Hills at 5 a.m. and donning tall rubber steel-toed boots, coveralls with reflective stripes, safety glasses, a hardhat and a backpack with a worrisome item called the "self rescuer" — a gas mask-like contraption to filter out carbon monoxide.
In the elevator, I feel the ghosts of gold miners from an age not so far back. Homestake closed in 2003, and the process of turning the mine into a lab started in 2006, the result of a $70 million donation from Sioux Falls philanthropist T. Denny Sanford, $40 million in state money and federal funds from the Department of Energy.
The elevator cage creaks to a stop after 10 minutes, the door rolls up like a garage door and the scientists pour out. The once-bare rock walls are coated with shotcrete and painted white. To the left, dark tunnels lead to the Ross shaft, which until recently was the main route from the surface to the 4,850-foot level where we departed.
At this depth, scientists are working on two main projects: the LUX and the Majorana experiments. Nearly a mile of rock helps keep out pesky interference such as cosmic rays and radiation. Deep underground, it's quiet. Really quiet.
I follow my guide, Bill Harlan, the communications director at the lab, to the Davis Campus, which hosts both experiments. The campus was completed in May.
Entering the clean room
To enter the Davis Campus, I must strip off my coveralls, scrub the mud off my boots with jets of water and slip on booties. This place needs to be kept clean, to avoid disrupting the experiments. Even photography equipment must be wiped down and sanitized.
Through a sealed door, part of the Majorana experiment appears to my left. Here, scientists are seeking to discover whether neutrinos, a ubiquitous subatomic particle of which 62 billion pass through your thumbnail every second, are their own antiparticle. To do so, scientists are building an extremely insulated cryostat — a container used to keep a substance very cold — in which they'll put the element germanium-76.
The scientists are hoping to observe a reaction called neutrino-less double-beta decay, which is when two neutrons convert into two protons and two electrons. Such a conversion has never been observed, and would be extremely rare. So for the scientists to sense it, all the cosmic background noise must be eliminated.
Most theorists think neutrinos will turn out to be their own anti-particle, but there's a chance they may not be. "If the neutrinos are their not their own anti-particle, we don't see it. So there's obviously a risk," John Wilkerson, the principle investigator on the experiment, tells me, and I sort of understand, mostly, I hope. Talking with scientists from Sandford is often like this, and it continued from there.
To make make the cryostat quiet enough, the germanium-76 will be insulated, from the inside out, by two inches of electroformed ultra-pure copper, two inches of commercial copper, 24 inches of lead and a plastic shield.
The electroformed copper is made underground, away from pesky particles like uranium and thorium that would give false radiation signals. The copper is deconstructed to its elemental parts by dissolving it in acid and then reassembled from the ground up by running an electric current through the acid solution.
I vaguely remember doing the same thing in high school science class. But not on this scale. Technicians wrapped in head-to-toe white lab suits behind glass windows machine bolts out of the electroformed copper. Science fiction archetypes began to swirl in my mind.
The reason to delve into this science is more philosophical than I might have guessed. Though the detector technology and ultra-clean processes may lead to innovations in microchips, bomb detectors and medical imaging, that's not the driving purpose.
"The real outcome of this is to give us an understanding of how all the forces go together and work. That is something that people have wondered about since Greek times. Where do we come from? What are we made out of?" Wilkerson tells me as we watch the technicians.
Mining for dark matter
We trek a short way down the hall to the LUX experiment. This one is deep underground for the same reasons as the Majorana — to avoid the background noise so prevalent on the surface. But these scientists are looking for something perhaps more elusive than neutrino-less double-beta decay: dark matter.
When scientists calculate the mass of the universe and compare it to how galaxies move gravitationally, the numbers don't crunch quite right, according to current laws of physics. There has to be something out there that comprises a significant amount of the mass in the universe. That's dark matter. But beyond that, scientists don't know much.
"It's the turn of the 21st century and the embarrassing situation is we still don't know what 95 percent of the universe is made of," Rick Gaitskell, the principle investigator for the LUX experiment, told me.
We descend a flight of steps to a room with water tank 24 feet in diameter and 24 feet tall filled with 72,000 gallons of highly purified water. Inside that tank is another cryostat filled with one-third of a ton of liquid xenon cooled to -100 degrees Celsius.
When the switch is flipped on this LUX experiment in the coming weeks, scientists are hoping to observe a particle of dark matter — particles of which are soaring through us all the time — interacting with a molecule of xenon. More than 120 light-sensitive detectors can sense the light that would be produced from an interaction. With two weeks of data, Sanford scientists will surpass the volume of research ever completed on dark matter.
The 4,850 feet of rock, the tank, the water and even the xenon all shield the detector. "In the middle, it is so quiet, if we start seeing reactions in there ... it's highly likely it has to be the case those events are from dark matter," Gaitskell said.
Gaitskell's rapid-fire ramblings gradually take on a more philosophical flavor. He pontificates on the meaning of science and why researchers strive to understand the universe. Sure, there are side benefits to the LUX experiment: inspiring Black Hills area students to study science, boosting the local economy. But the root of the experiment is an eons-long mission to know who we are.
"Are we really okay not knowing what 95 percent of the universe is made of?" Gaitskell said.
I think of the same pursuit that compelled people more than a century ago to excavate the open cut outside Lead, then to sink the Ross and Yates shafts once they could cut no further. The difference is they weren't mining for knowledge. They were mining gold.
We leave the LUX area, re-donning our coveralls and putting on hardhats. As we walk away, the world of science and sterile, white-washed rooms fades quickly. We board a decades-old mining cart on narrow tracks.
More exploration to come
Harlan, my guide, wants to show me the other side of this underground labyrinth. Soon the cart is whooshing through tunnels and I smell rock dust and something incinerated. Our driver, Bill Heisinger, fearlessly pilots us down these tracks, arteries through rock he's known since he started working at the mine almost 40 years ago. The work is different now.
"It's a lot easier going. They just don't have the hustle and bustle of having to get rock out everyday, so many tons of rock out. It's just deliver the supplies, take care of the shafts," said Heisinger, one of 70 former Homestake Mine employees who works for the lab.
Other experiments are on the horizon. In the Long Baseline Neutrino experiment, scientists intend to shoot a stream of neutrinos underground from the Fermilab in Chicago to the Sanford lab to study how the neutrinos change en route. But that experiment would take more space and cost more money than anything the lab has done yet.
Other experiments, too, are already in progress, including ones into microbiology and geology. Fourteen research groups are active at the laboratory, though LUX and Majorana are the main ones.
The cart takes us back to the elevator cage. This time, just a few people board the cage, including a former miner, Fritz Reller. He looks like a man from another era: grit and grime coat his face, his helmet looks like it came from a World War I German soldier and his hands look strong and are covered in grease.
The elevator cage creaks and bumps as it starts its ascent. With most of our headlamps off, the dark crushes in, the lab white suits fade from memory and I'm left looking at a miner who just stepped in from an era 30 years earlier.