Physicists are reviving one of science's oldest experiments to hunt for dark matter. Researchers plan to upgrade Henry Cavendish's 1773 torsion balance apparatus, which originally measured gravitational force between lead spheres, into a detector potentially 10,000 times more sensitive than current dark matter searches.

The upgraded experiment would work by looking for axions, hypothetical particles proposed as dark matter candidates. When axions pass through the torsion balance, they would cause subtle shifts in how the apparatus rotates. The method exploits a quirk of axion physics: these particles interact weakly with normal matter, making them nearly invisible to conventional detectors.

What makes this approach appealing is cost and speed. Traditional dark matter experiments like those using cryogenic germanium detectors or liquid xenon tanks require enormous underground facilities costing hundreds of millions of dollars. The Cavendish upgrade needs only modest modifications to the historic apparatus and existing laboratory space. Researchers could build and test multiple versions quickly, scanning a wider range of possible axion masses simultaneously.

The torsion balance method isn't entirely new to dark matter hunting. Previous teams have proposed similar approaches, but the Cavendish upgrade promises better sensitivity because the original apparatus was engineered with exceptional precision. Its 250-year track record demonstrates it can measure forces of extraordinary delicacy.

However, limitations remain. The sensitivity gain only applies to a specific axion mass range. The experiment must run in controlled environments shielded from vibrations and electromagnetic noise. Researchers must also account for systematic errors that plagued earlier gravitational measurements.

The project represents a strategic bet that sometimes overlooked historical instruments can outperform modern brute-force approaches. Rather than building bigger detectors, this work mines elegant design from the 18th century.

THE TAKEAWAY: Recycling Cavendish's 250-year