Collaborative Research: Measuring G with a Magneto-Gravitational Trap

引力是科学家们用数学描述的第一种力，用来解释月球、行星和恒星的运动。几百年后，引力仍然被认为是人们最不了解的力。它不能在物理学的不同理论中得到一致的描述，甚至它的强度也知之甚少。牛顿的引力常数，它量化了引力的强度，也许是宇宙中测量最差的基本属性。这个项目旨在极大地提高我们对这个常数的认识，这是自1798年亨利卡文迪什使用扭转天平进行测量以来技术上最重大的变化。该奖项资助的测量可能在物理学和天文学的许多领域都有价值，正在开发的新实验工具可能会导致用于测量极小力和加速度的新仪器，用于研究地球和惯性导航。此外，这些实验所要求的对细节的关注使其成为未来STEM工作者的绝佳训练场。该项目的最终目标是开发一种测量牛顿引力常数G的新系统，并以前所未有的精度（百万分之十或更高）测量G。该方法利用了最近开发的光学机械系统：悬浮在超高真空下的磁引力阱中的二氧化硅微球。微球的机械振荡将被用于摆动时间方法，以确定G从振荡频率的变化时，场质量被带到附近的被困粒子。该系统具有多种功能，使其几乎成为精密测量的理想选择，包括振荡频率可小于1 Hz，与周围环境隔离，以及其他自由度，可用作内置探头以校正漂移。之所以选择拟议的衡量战略，是因为它对科学界具有透明度。首先，系统的简单性使其易于理解和分析。其次，大部分数据将包含在记录的图像序列中;在重新分析组件时几乎没有隐藏的反馈回路或其他困难。为了确保对新测量方法的信心，所有数据和分析代码都将完整地存储并免费提供给其他研究人员。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Gravity was the first force mathematically described by scientists as an explanation for the motion of the moon, planets, and stars. Hundreds of years later, gravity is still considered to be the most poorly understood force. It cannot be consistently described across different theories in physics, and even its strength is poorly known. The Newtonian constant of gravitation, which quantifies the strength of gravity, is perhaps the most poorly measured fundamental property of the universe. This project seeks to greatly improve our knowledge of this constant with the most significant change in technique since the experiments of Henry Cavendish in 1798, who used a torsion balance for his measurements. The measurement funded by this award may be of value across many areas of physics and astronomy, and the new experimental tools being developed may lead to new instruments for measuring extremely small forces and accelerations for use in studying the earth and for inertial navigation. Further, the attention to detail required in these experiments makes them an exceptional training ground for tomorrow's STEM workers.The ultimate goal of this project is to develop a new system for measuring the Newtonian constant of gravitation G, and to make a measurement of G to unprecedented accuracy (10 parts per million or better). The approach leverages a recently-developed optomechanical system: a silica microsphere suspended in a magneto-gravitational trap under ultra-high vacuum. The mechanical oscillation of the microsphere will be used in the time-of-swing method to determine G from the change in oscillation frequency when field masses are brought near the trapped particle. The system has multiple features that make it nearly ideal for precision measurements, including an oscillation frequency that can be made less than 1 Hz, isolation from the surrounding environment, and other degrees of freedom to act as a built-in probe to correct for drifts. The proposed measurement strategy was chosen for its transparency to the scientific community. First, the simplicity of the system makes it simple to understand and analyze. Second, most of the data will be contained in sequences of images which are recorded; there are almost no hidden feedback loops or other difficulties in reanalyzing components. To ensure confidence in the new measurement, all data and analysis code will be stored and made freely available to other researchers in their entirety.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.