Test of theoretical solid earth and ocean gravity tides

Abstract

Data from three superconducting gravimeters at four different locations are analysed for agreement with theoretical computations of gravity tides and of the influence of ocean tides on gravity. The absolute value of the measured tide is determined by an independent absolute calibration of the gravimeters. The method differs from previous tests of tide theories in that it compares the entire predicted time series rather than specific harmonic constituents. In this way it is possible to test the solid earth and ocean tide effects independently. We find that the ratios of observed to predicted solid earth tides at different locations are the same within an uncertainty of about ±0.2 per cent. However, the magnitude of the tides deduced by the absolute calibration of the gravimeters is 0.6 per cent larger than the theoretical solid earth tide. We point out that an accurate determination of the solid earth tide in this way provides a direct comparison between the gravitational constant, G, at laboratory scales and at the distance to the moon.