Showing papers by "Robert L. Parker published in 1989"
TL;DR: An Airy-type geophysical experiment was conducted in a 2-km-deep hole in the Greenland ice cap to test for possible violations of Newton's inverse-square law, and an anomalous gravity gradient was observed.
Abstract: An Airy-type geophysical experiment was conducted in a 2-km-deep hole in the Greenland ice cap at depths between 213 and 1673 m to test for possible violations of Newton's inverse-square law. An anomalous gravity gradient was observed. We cannot unambiguously attribute it to a breakdown of Newtonian gravity because we have shown that it might be due to unexpected geological features in the rock below the ice.
64 citations
TL;DR: Signals reported as evidence for a non-newtonian 'fifth' force at a North Carolina television tower and elsewhere can be explained in a conventional way by postulating small density variations underground.
Abstract: Signals reported as evidence for a non-newtonian 'fifth' force at a North Carolina television tower and elsewhere can be explained in a conventional way by postulating small density variations underground. The assumptions employed in earlier analyses which pointed to a failure of the inverse square law are examined and found to be difficult to justify.
27 citations
TL;DR: In this article, the authors present an algorithm for interpolation and downward continuation of magnetic anomaly data that works within a statistical framework, assuming that the magnetic anomaly is a realization of a random stationary field whose power spectral density (PSD) we can estimate; by using the PSD the algorithm produces an array incorporating as much of the information contained in the data as possible while avoiding the introduction of unnecessary complexity.
Abstract: A two- or three-dimensional treatment of magnetic anomaly data generally requires that the data be interpolated onto a regular grid, especially when the analysis involves transforming the data into the Fourier domain. We present an algorithm for interpolation and downward continuation of magnetic anomaly data that works within a statistical framework. We assume that the magnetic anomaly is a realization of a random stationary field whose power spectral density (PSD) we can estimate; by using the PSD the algorithm produces an array incorporating as much of the information contained in the data as possible while avoiding the introduction of unnecessary complexity. The algorithm has the added advantage of estimating the uncertainty of every interpolated value. Downward continuation is a natural extension of the statistical algorithm. We apply our method to the interpolation of magnetic anomalies from the region around the 95.5°W Galapagos propagating rift onto a regular grid and also to the downward continuation of these data to a depth of 2200 m. We also note that the observed PSD of the Galapagos magnetic anomalies has a minimum at low wave numbers and discuss how this implies that intermediate wavelength (65 km < λ < 1500 km) magnetic anomalies are weaker than suggested by one dimensional spectral analysis of single profiles.
14 citations
TL;DR: In this article, a geophysical experiment was conducted in a 2-km-deep hole in the Greenland ice cap at depths between 213 m and 1673 m to test for possible violations of Newton's inverse-square law.
Abstract: A geophysical experiment was conducted in a 2-km-deep hole in the Greenland ice cap at depths between 213 m and 1673 m to test for possible violations of Newton's inverse-square law. A detailed ice-sounding radar survey was carried out to 5 km from the hole and merged with regional airborne radar data to define the basement interface. Highly accurate gravity measurements were carried out to 15 km from the hole to detect lateral density changes in the bedrock. The measurements were controlled with very accurate satellite and conventional positioning techniques. The basement interface model was input into a Newtonian computation to correct the observed gravity for known earth structure resulting in an anomalous gravity gradient of +3.87 mGal. A 3 dimensional ideal body analysis of the surface and borehole gravity data provided a means of bounding all possible Newtonian solutions for lateral density variation below the ice. Solutions with regional gravity offsets greater than or equal to10 mGal and density contrasts less than or equal to0.30 g/cm/sup 3/ are possible. We cannot unambiguously attribute the anomalous gradient to a breakdown of Newtonian gravity because there remains the possibility it is due to unexpected geological features in the rock below themore » ice. 11 refs., 6 figs., 1 tab.« less
1 citations