Dynamic measurement of gravitational coupling between resonating beams in the hertz regime

To date, there have been few dynamic measurements of gravitation in the laboratory, and fully controlled quantitative experiments have been limited to frequencies in the millihertz regime. Here we introduce a fully characterized experiment at frequencies in the hertz regime, which allows a quantitative determination of the dynamic gravitational interaction between two parallel beams vibrating at 42 Hz in bending motion. A large amplitude vibration of the transmitter beam produces a gravitationally induced motion of the high-quality-factor resonant detector beam with amplitudes up to 10(-11) m. The sub-picometre-resolution measurement is made possible by a setup that combines acoustical, mechanical and electrical isolation; a temperature-stable environment; heterodyne laser interferometry; and lock-in detection. The interaction is quantitatively modelled based on Newton's law of gravitation. Amplitude measurements at varying beam distances follow an inverse square law and agree with theoretical predictions to within approximately three percent. Furthermore, we extract the value of the gravitational constant G and near-field gravitational energy flow. We expect our experiment to enable progress in directions where current experimental evidence for dynamic gravitation is limited, such as the dynamic determination of G, inverse square law and gravitational shielding. Measurements of the gravitational interaction between two parallel beams vibrating in bending motion enable the quantitative investigation of dynamic gravitation in the hertz regime and allow the determination of the gravitational constant.