NIST Achieves Record-Precision Big G Measurement
SkimNews Take
Refined measurement of gravity's strength, despite slight methodological variations, indicates the consistency of its fundamental nature even at high precision, rather than revealing a chaotic or inconsistent force.
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- Schlamminger and colleagues at NIST measured big G at 6.67387×10⁻¹¹ m³/kg/s² using a sophisticated torsion balance with eight weights on two precisely calibrated turntables suspended by hair-thin ribbons — a painstaking reproduction of a 2007 French experiment.
- The new value is a fraction of a percent lower than the 2007 measurement, bringing it more in line with other tests performed over the years and increasing overall agreement among independent big G measurements.
- The team spent a decade identifying and reducing every possible source of uncertainty, pinning down several sources that hadn't previously been known, according to Jens Gundlach at the University of Washington.
- Big G measurements have historically disagreed with one another, and while most researchers attribute the remaining discrepancy to unrecognized sources of bias, Schlamminger notes there's a chance gravity itself behaves differently than expected — a 'crack' worth investigating.
- Henry Cavendish first measured gravity in 1798 using a torsion balance, a technique that has remained the foundation of big G experiments for more than two centuries, per Schlamminger.
- As cosmological measurements grow more precise, accurate knowledge of gravity's strength becomes increasingly important — Kasey Wagoner at North Carolina State University warned that small lab differences can 'blow up' on cosmic scales with potentially major implications.
Why it matters: The new measurement introduces previously unrecognized sources of uncertainty that future experiments can now target, reducing the scatter in a fundamental constant that has resisted consensus for decades. For cosmology, which depends on gravity's strength to interpret observations at the largest scales, a more reliable G value trims a stubborn systematic error with cascading downstream effects on measurements from lab to universe.
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