Measurement of Newton's Constant Using a Torsion Balance with Angular Acceleration Feedback

The ISLAND (Inverse Square Law And Newtonian Dynamics) Space Explorer is a new concept to test the gravitational Inverse Square Law at: (1) submillimeter scale and (2) at the largest Solar System scales (dozens of Astronomical Units --AU). The main idea is to embark a torsion pendulum at the center of gravity of a dedicated, possibly drag-free and attitude-controlled, interplanetary probe whose gravitational environment is accurately probed by, and corrected for thanks to six...

In this paper, we introduce the experiment based on a sensitive torsion pendulum for measuring and calibrating small forces at nanonewton scale. The force standard for calibration is the universal gravitation between four masses separated by known distances. It is realized by two test masses suspended as the part of torsion pendulum and two source masses on a rotation table. Two force generation mechanisms, optical force from radiation pressure and electrostatic force by capa...

We report on the design and sensitivity of a new torsion pendulum for measuring the performance of ultra-precise inertial sensors and for the development of associated technologies for space-based gravitational wave observatories and geodesy missions. The apparatus comprises a 1 m-long, 50 um-diameter, tungsten fiber that supports an inertial member inside a vacuum system. The inertial member is an aluminum crossbar with four hollow cubic test masses at each end. This structu...

We report the performance of an instrument that employs a torsion balance for probing a non-standard force in the sub-micrometre range. High sensitivity is achieved by using a torsion balance that has a long torsional period, strong magnetic damping of all vibrational motions and a feedback system that employs an optical lever. In torsion balance experiments, the distance fluctuations during measurements and the accuracy to which the absolute distance is determined are crucia...

In spite of two hundred years of considerable efforts directed towards improvement in the experimental techniques, gravitational measurements have provided unsettled results for Newton's gravitational constant G. Analysis of the published (over ~75 years) small-scale gravitational measurements, presented in this report, unveils a large secular increase in the gravitational force, that reveals itself as a formal increase in the Newton's constant G at a rate 'G dot per G' = (1....

About a dozen measurements of Newton's gravitational constant, G, since 1962 have yielded values that differ by far more than their reported random plus systematic errors. We find that these values for G are oscillatory in nature, with a period of P = 5.899 +/- 0.062 yr, an amplitude of (1.619 +/- 0.103) x 10^{-14} m^3 kg^{-1} s^{-2}, and mean-value crossings in 1994 and 1997. However, we do not suggest that G is actually varying by this much, this quickly, but instead that s...

In 1687, Isaac Newton published the universal law of gravitation stating that two bodies attract each other with a force proportional to the product of their masses and the inverse square of the distance. The constant of proportionality, G, is one of the fundamental constants of nature. As the precision of measurements increased the disparity between the values of G, gathered by different groups, surprisingly increased. This unique situation was reflected by the 1998 CODATA d...

String theory, as well as the string inspired brane-world models such as the Randall-Sundrum (RS) one, suggest a modification of Newton's law of gravitation at small distance scales. Search for modifications of standard gravity is an active field of research in this context. It is well known that short range corrections to gravity would violate the Newton-Birkhoff theorem. Based on calculations of RS type non-Newtonian forces for finite size spherical bodies, we propose a tor...

Progress and plans are reported for a program of gravitational physics experiments using cryogenic torsion pendula undergoing large amplitude torsional oscillation. The program includes a UC Irvine project to measure the gravitational constant G and joint UC Irvine - U. Washington projects to test the gravitational inverse square law at a range of about 10 cm and to test the weak equivalence principle.

We tested the gravitational $1/r^2$ law using a stationary torsion-balance detector and a rotating attractor containing test bodies with both 18-fold and 120-fold azimuthal symmetries that simultaneously tests the $1/r^2$ law at two different length scales. We took data at detector-attractor separations between $52~\mu$m and 3.0 mm. Newtonian gravity gave an excellent fit to our data, limiting with 95\% confidence any gravitational-strength Yukawa interactions to ranges $< 38...