Measurement of Newton's gravitational constant with the BIPM torsion balance

In 2001, researchers at the International Bureau of Weights and Measures (BIPM) published a measurement for the gravitational constant G, determined with a torsion balance using two independent modes, the Cavendish (free deflection) and servo (electrostatic) [1]. While the results obtained with both methods agreed, they were significantly higher than results obtained by other researchers. In the following years, researchers at the BIPM built a second-generation torsion balance, MARK-2, and published in 2013[2,3]. The 2001 and 2013 results were also in agreement. To further understand both the large discrepancy between the BIPM measurements and those of the rest of the world as well as the inconsistent results produced by all 16 of these G experiments, MARK-2 was shipped to NIST in 2016. At NIST, we performed an independent, blind measurement of G and will provide a status update on the experiment and, possibly, reveal the first result.

[1] T.J. Quinn et al., Phys. Rev. Lett. 87, 111101 (2001).

[2] T.J. Quinn et al., Phys. Rev. Lett. 111, 101102 (2013).

[3] T.J. Quinn et al., Phil. Trans. Roy. Soc A 372, 20140032 (2014).