science
Decade-Long Experiment Yields New Measurement of Gravitational Constant
A team at the National Institute of Standards and Technology completed a 10-year experiment to measure the gravitational constant, known as big G. The result differed slightly from a previous measurement conducted in France. This ongoing discrepancy highlights challenges in precisely determining this fundamental constant.
Apr 26, 2:08 PM·2m read1 source
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A 10-year experiment conducted by a team at the National Institute of Standards and Technology (NIST) in the United States has produced a new measurement of the gravitational constant, referred to as big G. The constant quantifies the strength of gravitational attraction between objects.
The team's leader stated that the effort serves as a reminder of gaps in scientific understanding. The gravitational constant influences phenomena such as objects falling, personal weight measurements, and the moon's orbit around Earth. It applies to both small-scale events like an apple dropping and large-scale motions of galaxies.
Despite over two centuries of attempts, measurements of big G continue to vary slightly between experiments.
The experiment replicated a prior study from the International Bureau of Weights and Measures in France to assess consistency. The setup used a torsion balance, based on a design by English scientist Henry Cavendish in 1798. This involves a thin wire suspending weights, which rotate minimally when attracted by nearby masses.
In the NIST version, metal cylinders were positioned to exert gravitational pull on the suspended weights. Instruments measured the wire's twist to calculate the gravitational force and derive big G. To ensure accuracy, the team refined the apparatus over the decade.
The team leader implemented a blinding method by having a colleague add an unknown offset to key measurements, sealed in an envelope. This prevented bias from influencing refinements. The envelope was opened at the experiment's conclusion during a conference.
