Measurements Of The Eccentricities Of The Attracting Masses And The Susceptibilities In The Determining G

The gravitational constant G is an important fundamental physics constant closely related to theoretical physics, astrophysics and geophysics,the precise measurement of G is faced with various kinds of difficulties and challenges, however.In the determination of G, the densites of the attracting masses can not be completely distributed evenly, so there will be an uncertainty to G when the coupling coefficient is computed on the assumption that their densities are evenly distributed. Generally speaking, there will be a small eccentricity between the center of mass and the geometric centre in an object, if its density is not evenly distributed. The eccentricities of a spherical attracting mass and two cylindrical attracting masses are measured by an electronic balance (Mettler ToledoPR2004), with the results as =(0.31±0.05)μm, =(10.5±2.6)μm, =(6.5±3.7)μm. The uncertainties of the eccentricities to G are discussed finally.In the precise gravitational experiment, susceptibility measurements are always needed to be performed to decrease and examine the effect of the magnetism of instruments to the experimental results. Using an electronic balance (Mettler-Toledo AT106), we examined volume susceptibilities of some materials often used in the gravitational experiments by a comparing method. The lower limit of the measurable range of susceptibility can be extended to the 10-7 order by this method, and the effect from background noise to the results is greatly reduced.This project is supported by the National Science Foundation of China under Grant No.19835040 and No. 10121503.