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arXiv · 2009.09546

Measurement of Gravitational Coupling between Millimeter-Sized Masses

Tobias Westphal·Hans Hepach·Jeremias Pfaff·Markus Aspelmeyer
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Abstract

We demonstrate gravitational coupling between two gold spheres of approximately 1mm radius and 90mg mass. By periodically modulating the source mass position at a frequency f=12.7mHz we generate a time-dependent gravitational acceleration at the location of the test mass, which is measured off resonance in a miniature torsional balance configuration. Over an integration time of 350 hours the test mass oscillator enables measurements with a systematic accuracy of 4E-11m/s^2 and a statistical precision of 4E-12m/s^2. This is sufficient to resolve the gravitational signal at a minimal surface distance of 400mum between the two masses. We observe both linear and quadratic coupling, consistent in signal strength with a time-varying 1/r gravitational potential. Contributions of non-gravitational forces could be kept to less than 10% of the observed signal. We expect further improvements to enable the isolation of gravity as a coupling force for objects well below the Planck mass. This opens the way for precision tests of gravity in a new regime of isolated microscopic source masses.

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Tobias Westphal, Hans Hepach, Jeremias Pfaff, Markus Aspelmeyer. 2020-09-21. Measurement of Gravitational Coupling between Millimeter-Sized Masses. https://arxiv.org/abs/2009.09546

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