Nature2014-06-27 1:46 PM

测量牛顿引力常数G的一个新方法 Precision measurement of the Newtonian gravitational constant using cold atoms


牛顿引力常数G (亦称为万有引力常数或“big G”)是一个基本物理常数,用在两个物体之间的引力计算中。有几种方法能够以高精度测量G,但这些测量结果不一致,这可能是由于不同实验中未知误差的介入。为了识别并最终消除产生这些偏差的系统性误差,Gabriele Rosi及同事利用通过激光冷却的原子实施的量子干涉法(这是与以前的测量方法根本不同的一种实验方法)完成了对G的高精度测量。他们以~0.015%的精度获得了一个G值,接近传统测量方法的精度,并且还有进一步做相当大改进的可能性。虽然这个结果尚未解决测量结果不一致的问题,但这样一个根本不同的方法的使用却有望找到困扰了以前测量工作的系统性误差。


About 300 experiments have tried to determine the value of the Newtonian gravitational constant, G, so far, but large discrepancies in the results have made it impossible to know its value precisely. The weakness of the gravitational interaction and the impossibility of shielding the effects of gravity make it very difficult to measure G while keeping systematic effects under control. Most previous experiments performed were based on the torsion pendulum or torsion balance scheme as in the experiment by Cavendish in 1798, and in all cases macroscopic masses were used. Here we report the precise determination of G using laser-cooled atoms and quantum interferometry. We obtain the value G = 6.67191(99) × 10−11 m3 kg−1 s−2 with a relative uncertainty of 150 parts per million (the combined standard uncertainty is given in parentheses). Our value differs by 1.5 combined standard deviations from the current recommended value of the Committee on Data for Science and Technology. A conceptually different experiment such as ours helps to identify the systematic errors that have proved elusive in previous experiments, thus improving the confidence in the value of G. There is no definitive relationship between G and the other fundamental constants, and there is no theoretical prediction for its value, against which to test experimental results. Improving the precision with which we know G has not only a pure metrological interest, but is also important because of the key role that G has in theories of gravitation, cosmology, particle physics and astrophysics and in geophysical models.






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