Feasibility of measuring the Shapiro time delay over meter-scale distances

TL;DR

This paper explores the possibility of measuring the Shapiro time delay, a space-time curvature effect, over meter-scale distances using advanced gravitational wave detectors like LIGO, which could enable laboratory-scale tests of general relativity.

Contribution

It demonstrates the feasibility of detecting the Shapiro time delay at laboratory scales with existing laser interferometers and provides a design example for such an experiment.

Findings

Advanced LIGO can detect the Shapiro delay caused by a rotating mass.

A feasible experimental setup for measuring space-time curvature at meter scales.

First proposal to observe gravitational effects on a laboratory distance scale.

Abstract

The time delay of light as it passes by a massive object, first calculated by Shapiro in 1964, is a hallmark of the curvature of space-time. To date, all measurements of the Shapiro time delay have been made over solar-system distance scales. We show that the new generation of kilometer-scale laser interferometers being constructed as gravitational wave detectors, in particular Advanced LIGO, will in principle be sensitive enough to measure variations in the Shapiro time delay produced by a suitably designed rotating object placed near the laser beam. We show that such an apparatus is feasible (though not easy) to construct, present an example design, and calculate the signal that would be detectable by Advanced LIGO. This offers the first opportunity to measure space-time curvature effects on a laboratory distance scale.