Physics: Beam vibrations used to measure ‘big G’

Newton’s constant of gravitation has been measured by studying the gravitational interaction between vibrating metal beams, according to a paper published in Nature Physics. The experiment — conducted in a laboratory under the Swiss Alps — will enable insights into the dynamic nature of gravitation.

Newton’s constant of gravitation — known as big G — is a fundamental constant involved in the determination of the gravitational force between two objects. The value of big G must be determined experimentally. However, the uncertainty of big G is relatively high with a large spread in measured values, suggesting that not all sources of uncertainty are known or well understood. Alternative measurement methods are therefore needed.

In a laboratory located in a former underground military facility under the Swiss Alps (which provides a very quiet and temperature-stable environment), Jürg Dual and colleagues suspended two beams in parallel from a support, and set one of the beams into vibration. The gravitational interaction between the beams then induced a motion of the other beam, allowing for the dynamic measurement of big G at much higher frequencies than previous experiments.

In an accompanying News & Views, Christian Rothleitner states that the authors’ “experiment is entering into unknown territory for verifying Newton’s law of gravitation — an important path to follow towards a more complete understanding of gravitation”.