Tests of the gravitational inverse square law and equivalence principle, and cryogenic torsion pendulum development

在发展低温扭摆作为引力物理学研究的一般工具的同时，将扩大一项引力物理学基本定律的实验室试验方案。 研究计划包括：1）15厘米量级质量分离的引力平方反比关系的测试，2）在各种范围内弱等效原理的测试，包括实验室质量，附近的山脉和太阳的引力场源， 3)完成对引力常数G的测量。 这些项目是在一个遥远的地下实验室（巴特尔引力物理实验室，BGPL）进行的，该实验室是在太平洋西北国家实验室的支持下准备的，该实验室位于华盛顿里奇兰附近一个孤立的环境保护区的一个前耐克导弹掩体中。 大部分工作是与华盛顿大学的保罗·博因顿的引力物理小组合作完成的。牛顿引力定律的平方反比距离依赖性的表观引力偏差的发现可能标志着自然界中新的基本力的存在，对物理定律具有深远的影响。 同样，如果发现违反了弱等效原理，即所有物体在引力场中以相同的加速度下落，也会产生深远的影响。 这个原理是爱因斯坦广义相对论的基石，许多现代引力理论都预测它在某种程度上会失败。 引力常数G的测量将有助于解决在过去二十年中对这个基本常数进行的大量测量之间的重大差异。 在这项工作中使用的低温扭摆的技术发展将是潜在的好处，在广泛的实验研究中，它是非常重要的测量小的宏观力与极端灵敏度。

A program of laboratory tests of fundamental gravitational physics laws is to be extended, in parallel with development of the cryogenic torsion pendulum as a general tool for research in gravitational physics. Included in the research program are: 1) a test of the inverse square distance dependence of the gravitational force for mass separation on the order of 15 centimeters, 2) tests of the weak equivalence principle over various ranges, for gravitational field sources which include laboratory masses, a nearby mountain, and the sun, and 3) completion of a measurement of the gravitational constant G. These projects are conducted in a remote underground laboratory (Battelle Gravitational Physics Laboratory, BGPL) which has been prepared with support from the Pacific Northwest National Laboratory in a former Nike missile bunker on an isolated environmental preserve near Richland, Washington. Most of this work is done in collaboration with the gravitational physics group of Paul Boynton at the University of Washington.A discovery of deviation of the apparent gravitational force from the inverse square distance dependence of Newton's law of gravity could signal the existence of new fundamental forces in Nature, with profound implications for the laws of physics. Similarly, discovery of a violation of the weak equivalence principle which asserts that all objects fall with the same acceleration in a gravitational field, would have profound implications. This principle, which is a foundation stone of Einstein's theory of General Relativity, is predicted by many modern theories of gravitation to fail at some level. The measurement of the gravitational constant G will help resolve significant discrepancies among a number of measurements of this fundamental constants made in the last two decades. Technological development of the cryogenic torsion pendulum used in this work will be of potential benefit to a wide range of experimental research in which it is important to measure small macroscopic forces with extreme sensitivity.