During the universe’s formation, equal parts of matter and antimatter should have been created, but that didn’t happen. Neutrinos may hold the key to why.

The universe as we know it shouldn’t exist. Unlocking the reasons why may depend on once again striking gold in a mine buried a mile underground in rural South Dakota.

The largest U.S.-based particle physics experiment ever is now under construction in the old mine in Lead, S.D., breathing new life into the small town more than 140 years after the Black Hills gold rush drove its founding.

The international collaboration involving 1,000 scientists from more than 30 countries aims to answer the question: Are mysterious particles called neutrinos the reason we are here?

Scientists believe equal parts of matter and antimatter should have been created during the formation of the universe. But that didn’t happen, and no one knows why. Instead, the visible universe is dominated by matter. Neutrinos may be the reason why — physicists just need a bigger, well, everything to find out.

10 years, $1 billion, 870,000 tons of rock

Once complete, the Deep Underground Neutrino Experiment will beam the particles 800 miles through the earth from Fermi National Accelerator Laboratory outside Chicago to Lead’s Sanford Underground Research Facility.

Sanford Underground Research Facility, which opened in 2012 after it repurposed the gold mine for scientific research, has run experiments involving neutrinos and dark matter, but nothing even close to this scale.

To embark on its grand experiment, Sanford must first expand its footprint by carving out the Long-Baseline Neutrino Facility amid tunnels that once housed the deepest and most productive gold mine in the Western Hemisphere.

Over the next 10 years, workers will remove more than 870,000 tons of rock and install a four-story high, 70,000-ton neutrino detector, while the lab’s Illinois counterpart also…