After 10 years of painstaking work, National Institute of Standards and Technology physicist Stephan Schlamminger has produced a new measurement aimed at one of science's most frustrating questions: the true strength of gravity.
The result was precise, hard-won, and still not enough to settle the debate, ScienceDaily reported.
Here's what to know
Schlamminger spent about 10 years at the National Institute of Standards and Technology working to measure the universal gravitational constant, known as "big G" — the number that describes how strongly objects attract one another through gravity.
But when he finally revealed his team's blinded result during a presentation on July 11, 2024, it did not match the International Bureau of Weights and Measures' 2007 result from Sèvres, France.
ScienceDaily noted that the NIST team published a value of 6.67387 × 10-11 meters3/kilogram/second2 in Metrologia, a result 0.0235% lower than the BIPM experiment.
Even such a small difference matters because big G has resisted precise agreement for more than 225 years. Many other fundamental constants can be measured to six or more significant digits, but gravity's central constant has remained unusually difficult to determine.
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Before unveiling the answer, Schlamminger said: "I had really dotted all the i's and crossed all the t's of the experiment."
More background
Gravity's effects are familiar enough: it keeps people anchored to Earth, governs the motion of planets, and helps shape galaxies.
What makes the measurement so challenging is that gravity is incredibly weak compared with the other fundamental forces.
A small magnet lifting a paper clip illustrates that imbalance clearly, overcoming Earth's pull.
In the lab, researchers are trying to detect gravity between far smaller objects, which makes the signal extraordinarily faint.
That is one reason even small discrepancies matter in precision physics.
Sometimes they trace to overlooked experimental effects. Other times, they raise the possibility that researchers may be missing a deeper feature of nature.
For everyday life, this new number is not expected to change much. It will not alter a bathroom scale reading or affect ordinary kitchen measurements.
For fundamental physics, however, getting the constant right is part of building a more accurate picture of the universe.
What's being done?
NIST took multiple steps to reduce bias and rule out hidden errors.
Schlamminger's colleague Patrick Abbott helped set up a blind analysis by secretly altering part of the mass data, and the correction was sealed away until the analysis was complete.
The team also revisited the work after discovering that an air pressure effect had not been fully accounted for, delaying the reveal and extending the project by two more years.
To test whether the materials themselves might be skewing the answer, the researchers repeated the experiment using both copper and sapphire masses. Both produced essentially the same result, eliminating one possible explanation for the mismatch.
"Every measurement is important, because the truth matters," Schlamminger explained.
"For me, making an accurate measurement is a way of bringing order to the universe, whether or not the number agrees with the expected value," he added.
Where can I learn more?
Check out these articles on Ohio campus policy, big-picture physics debates, fusion and plasma experiments, and a Florida lab conspiracy rumor.
• Across physics, experts remain split on how reality works in a sprawling cosmology survey.
• At PPPL, engineers built an SUV-sized barrel to probe magnetic reconnection and flare-like bursts.
• Physicists revisiting old data made a remarkable discovery about fusion after replicating a forgotten experiment.
• In Florida, the National MagLab became a joke online after a weather-control conspiracy spread.
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