Beneath a prairie about 35 miles west of Chicago, scientists are beaming subatomic particles through the Earth at nearly the speed of light.
The Fermi National Accelerator Laboratory, or Fermilab, used to be home to the world’s most powerful particle accelerator, the Tevatron. That title now belongs to the Large Hadron Collider in Europe, and in 2011, the Tevatron was shut down.
Now, Fermilab is a global center for research into a tiny particle that could help answer some of the biggest questions in physics: the neutrino. Neutrinos have no electrical charge and almost no mass, but they’re everywhere.
Bonnie Fleming, Fermilab’s deputy chief research officer, holds out her hand and counts to three.
“Three trillion neutrinos just passed through my hand,” she says. “There are some left over from the Big Bang; they’re produced in stars, in supernovae, in nuclear reactors, in the highest cosmic accelerators in the universe and in particle accelerators here on Earth.”
Neutrinos may be ubiquitous, but they’re also mysterious. Despite being the second-most abundant particle in the universe (after photons), they rarely interact with other matter. Scientists think studying neutrinos could reveal more about the origins of the universe. Namely, why didn’t neutrinos and anti-neutrinos annihilate each other when the universe was being formed?
“Put simply, are neutrinos the reason we exist?” Fleming says. “What they’re going to tell us about the cosmos, we’re still learning.”
To help answer that question, scientists at Fermilab are working on a project called the Deep Underground Neutrino Experimentor DUNE, in collaboration with the Sanford Underground Research Facility in South Dakota.
DUNE is currently under construction, but once it’s finished, scientists at Fermilab will be able to fire the world’s most intense beams of neutrinos between detectors more than a mile underground at the two research facilities, 800 miles apart. That will allow them to detect subtle changes in the type, or flavor, of neutrinos as they travel long distances, and possibly answer some of physics’ most fundamental questions about the nature of the universe.
Most of Fermilab’s neutrino experiments have to be done deep underground to filter out background radiation from cosmic rays at the surface.
About 300 feet underground another neutrino experiment called NOvAhas been collecting data since 2014. Scientists visiting the experiment have to leave their IDs outside an industrial elevator at the surface, so people will know who is down below in case of an emergency.
At the bottom of the elevator shaft is a cavernous tunnel. Water trickles down the sides of rock walls. In the NOvA experiment room there are rows of computers, and a semi-truck-sized box of acrylic bars filled with a special oil that measures the path of charged particles affected by the neutrinos passing through.
Fleming says there are similarities between the data Fermilab is collecting here, 300 feet below the surface of the Earth, and the experiments done by astronauts.
“You are looking into the farthest reaches of the universe through the eye of a neutrino interaction,” she says. “And in that sense, absolutely, you’re looking back in time and using neutrinos to be able to do that.”
More than 4,000 scientists work at the lab. About 1,000 work on DUNE, a project that will cost around $1 billion between Fermilab and the other facilities involved.
Fleming says scientists like her are trying to understand if neutrinos can explain why the universe didn’t self destruct in its early days.
“Fundamentally that’s a really fascinating and interesting question,” she says. “It requires big experiments and big science to be able to answer, but knowing the answer to it tells us something about how the universe was created, how everything we see was created, and that’s fantastic.”
Above ground, Femilab’s director Nigel Lockyer sits in his office, beneath a whiteboard full of complex mathematical equations.
“I suspect we’re scratching the surface on everything we know,” Lockyer says. “The experiment we’re pursuing is not only to understand the neutrino, but understand the role the neutrino plays in the cosmos.”
Lockyer says fundamental scientific research benefits society, often in unexpected ways. When he talks to lawmakers in Washington about Fermilab’s work, Lockyer says he usually cites a few examples.
“My first one I usually talk about is cancer therapy,” he says. “Modern hospitals use protons, not just x-rays, for cancer therapy. And the seminal paper on using protons for cancer therapy was written by the first director of Fermilab.”
Even the now-defunct Tevatron inspired the design of superconductors and critical parts of magnetic resonance imaging machines or MRIs.
“We’ve had an indirect, huge impact on medical physics,” Lockyer says. “We’re a laboratory that builds things, and we build things at the edge of what’s possible.”
The edge of possibility now is the DUNE experiment, which is scheduled to be fully operational in 2026. Once it’s up and running, it will collect data for decades and could change our understanding of the universe.
Chris Bentley, Marcelle Hutchins and James Trout produced this story for broadcast, and Todd Mundt edited.
This article was originally published on WBUR.org.
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