LEAD, SD — Every morning, two dozen miners and engineers cram into a cage-like elevator for an 11-minute descent into the bowels of South Dakota’s Black Hills.
At the bottom, a mile below the surface, the cage door lifts up and workers descend a winding, rocky corridor. At the end is the result of three years of work: two empty caverns, each as tall as a seven-story building and so long that it takes a full second for your voice to reach the back wall and echo.
For more than a century, these depths have been scoured by miners in search of gold. Today, they are home to the Sanford Underground Research Facility, or SURF. In the coming years, some of the world’s top particle physicists plan to turn this realm into the listening end of an 800-mile-long, $5 billion tin can telephone. They hope to hear a whispered answer to an existential question: How did we get here?
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The message will be delivered by incoming neutrinos, strange, elusive particles that weigh almost nothing and travel nearly as fast as light. At the other end of the wire, a half-mile-wide particle accelerator operated by Fermi National Accelerator Laboratory, just outside Chicago, will create billions of neutrinos every second in a narrow beam pointed directly at that cavern. They will travel underground, not through a tunnel, but through three states of solid rock.
Physicists hope that when neutrinos arrive, they will finally explain how the Big Bang created just a little bit more matter than its opposite, antimatter – an excess that makes up everything in the universe today.
The phone, officially called the Deep Underground Neutrino Experiment, or DUNE, is the largest underground science and engineering project in U.S. history. It took a decade to get to this point, and it may be another decade before it starts working. If all goes well, it will turn the neutrino into a known quantity, filling a major gap in scientists’ understanding of the universe and, perhaps, returning the United States to its former position as the center of particle physics.
What is antimatter?
When an atom splits, its two fragments fly off at odd, oblique angles. In 1930, physicist Wolfgang Pauli came up with the neutrino to explain this behavior: “There must be a third, invisible bullet whizzing in a third direction, as fast as light but as ethereal as a ghost,” Pauli concluded.
It took decades for someone to prove him right. Neutrinos are the most numerous particles in the universe, but also the most difficult to study. They elude particle detectors as easily as they pass through bedrock. They are so slippery that they are the only particles whose mass remains a complete mystery.
Moreover, while all other particles have an immutable identity, neutrinos are shapeshifters. Once operational, Fermilab’s accelerator will produce one of three “flavors” of neutrinos. But when they reach the Southern Hemisphere, they will not be able to expand.
