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  • Review of Alcubierre Drive Experimentation and Proposals for Tabletop Generation of Gravitational Waves

    Abstract

    Abstract

    There is renewed interest in the Alcubierre Drive prompted by interferometer experimentation conducted by Harold White in NASA Eagleworks Lab. We attempt to replicate the research used by White to develop the same experiment and attempt to achieve similar results. Although the metric proposed by Alcubierre appears to be valid, it is dogged by a number of questions regarding its physical realizability. Because White does not publish his calculations for space-time warping caused by electromagnetic energy, we research and derive our own sensitivity requirements for detecting warp fields. We provide a basis for modeling warp field experiments. Examination of methods included gravitational wave detection through the use of laser, atom, and neutron interferometry as well as resonant-mass detectors while maintaining the primary requirement that the experiment must fit in a tabletop. We found that a resonant-mass detector made of a high frequency phonon trapping acoustic cavity (Goryachev & Tobar, 2014; sensitivity of \(10^{-22}\) Hz) was the most feasible instrument to perform tabletop experimentation. Measuring high-frequency gravitational waves was the simplest approach to measuring results. Additionally, using the Gertsenshtein equation for converting electromagnetic energy to gravitational waves, we calculate that the magnetic flux density of an electric clock is well within the sensitivity range of Goryachev & Tobar’s device (approximately \(10^{-18}\) Hz), opening the possibility for small scale experimentation. After establishing experimental requirements, we propose two experiments to further advance Alcubierre experimentation: 1) a proof of spacetime warping sensitivity using an electromagnetic source; and 2) a scalable quantum optical squeezing technique for producing negative energy densities built on work by E. Davis et al., O. Firstenberg et al., and L. H. Ford et al.

    Introduction

    adjust this so it talks about how experimentation needs to be taken to a realistic tabletop level

    Since the 1994 publication of the Alcubierre solution to the Einstein Field Equations - the Alcubierre Drive (Alcubierre, 1994) - a handful of proposals and experiments have been published attempting to demonstrate the realizability of faster-than-light travel. Early proposals included a focus on zero-point energy (H.E. Puthoff, 1998). In the late 2000s, organizations such as Icarus Interstellar and the Tau Zero foundation have charted fields of interest for faster-than-light travel. A class of recent experiments, EM warping and measurement using laser interferometry (White, 2015), are of particular interest and examining their feasibility is particularly useful for advancing Alcubierre drive experimentation.

    Harold White is using several methods of experimentation (including Twyman-Green and Fabry-Perot interferometry) to measure spacetime warping in a similar geometry to the Alcubierre solution. However, many objections have been raised against the instrumentation and results, including interference from a change in the refractive air index (Lee & Cleaver, 2014). The authors of this paper were not able to obtain White’s calculations that would allow examination of his predicted warping - and resulting phase shift using laser interferometry - that White is attempting to measure. Given the lack of evidence to support positive results, there’s reason to attempt replication of White’s experiments and methods.

    Because gravity is a property of spacetime geometry, a foundation for Alcubierre experimentation can be built on existing lines of research in gravitational instrumentation. The COW experiment demonstrated remarkable pioneering in neutron interferometry and gravitational measurement (Colella, Overhauser, and Werner, 1974). Since the 1960s, continued improvements have been made to Weber’s original 1966 proposal for a resonant-mass detector to measure gravitational waves (Aguiar, 2014). It’s important to make the distinction that White’s experiment is attempting to directly measure spacetime distortion on a laser’s path, whereas other laser interferometers such as LIGO are designed to detect residual gravitational phenomenon, or gravitational waves. However, the method of detection is irrelevant since a positive result requires verification of the Alcubierre geometry and not necessarily replication of White’s experimental design.