Non-Newtonian Forces

University Of Washington, Seattle WA

Investigators

Abstract

A primary goal of modern physics is to understand at the most fundamental level possible the nature and behavior of matter and energy, the basic components of our universe. Empirical tests of Einstein's weak-field (Newtonian) gravity play an important role in judging possible extensions of this understanding, embodied in the so-called Standard Model of fundamental interactions. Even small deviations from Newtonian behavior could constitute evidence for violation of the Standard Model as currently formulated. Deviations have not yet been found, but the possibilities for expecting such anomalies at a low level abound in the theoretical literature over the past decade. The goal of this project is to bring to operation an experiment that will substantially restrict the viability of these speculations by setting at least an order-of-magnitude more stringent upper limit on the strength of putative non-Newtonian interactions than now established. Alternatively, these more precise measurements could uncover previously undetected deviations. Either outcome would advance fundamental understanding of matter and energy. In collaboration with a group at UC Irvine, new advances in measurement precision using cryogenic techniques have been exploited, methods to dramatically reduce systematic effects have been developed, and a new laboratory facility that provides an ultra-low vibration environment that allows exploitation of these substantial improvements has been established. The instrumentation has only a single moving part, a precisely configured quartz mass suspended by a thin filament. State-of-the-art electro-optic technology is used to monitor the rotation of this mass about the filament axis with extreme sensitivity. It is the absence of such a rotation, under carefully controlled conditions, that constitutes the experimental manifestation of Newtonian behavior -- violation (and possible evidence for new physics) is indicated by even the smallest movement. Hence, the sensitivity of this test depends on how small a rotation angle can reliably be detected. To provide an illustration of the project's measurement capability, this minimum detectable rotation is comparable to the angle subtended by the width of a human hair located at the top of the Washington Monument as viewed from the center of the State of Washington. All these activities involve young scientists -- post-docs, graduate and undergraduate students -- as well as corporate partners Battelle Laboratories, Boeing Airplane Co. and institutional sponsor Pacific Northwest National Laboratory, all involved in efforts to extend the quality of the research and educational outreach as broadly as possible.