Collaborative Research: Measuring G with a Levitated Test Mass

About This Grant

Gravity was the first force mathematically described by scientists as an explanation of the motion of the moon, planets, and stars. Hundreds of years later, gravity is still considered to be the most poorly understood force. It cannot be consistently described across different theories in physics, and even its strength is poorly known. The Newtonian constant of gravitation, which quantifies the strength of gravity, is perhaps the most poorly measured fundamental property of the universe. This project seeks to greatly improve our knowledge of this constant with the most significant change in technique since the experiments of Henry Cavendish in 1798, who used a torsion balance for his measurements. The measurement funded by this award may be of value across many areas of physics and astronomy, and the new experimental tools being developed may lead to new instruments for measuring extremely small forces and accelerations for use in studying the Earth and for inertial navigation. In addition, the attention to detail required in these experiments makes them an exceptional training ground for tomorrow's STEM workers. This project aims to resolve discrepancies in measurements of the Newtonian constant of gravitation, G, advancing our understanding of fundamental forces and potentially uncovering new physics. The approach is to levitate a graphite composite test mass in ultra-high vacuum. Changes in the oscillation frequency of the test mass, induced by carefully positioned field masses, are used to determine G. Eliminating mechanical suspensions minimizes systematic errors, while analysis of the trajectory enables precise modeling of higher-order oscillation modes in the test mass's motion. The goal is to provide an independent and transparent measurement of G with a precision of 10 parts per million, offering valuable insights into resolving discrepancies in existing measurements and paving the way for even more precise determinations. The experiment emphasizes simplicity in design and openness to encourage broader participation from the scientific community. All data and analysis tools will be made openly available to facilitate independent verification. By carefully addressing systematic uncertainties and sharing results transparently, this project aims to contribute constructively to the broader effort of refining the measurement of G, while demonstrating methods with applications in precision metrology and gravitational physics. The project's novel approach, utilizing magneto-gravitational trapping technology, represents a significant leap in precision measurement techniques, with implications for fields ranging from fundamental physics to precision sensing. Beyond improving the accuracy of G, this work could contribute to experiments exploring new interactions, such as potential couplings between dark matter and ordinary matter, as well as to precision accelerometry in space. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.