Daedalus: Gravity waving to us

Abstract

Physicists are still exasperated by the elusiveness of gravitational waves. Laser interferometers and resonating metal bars have so far failed to detect them. Einstein showed that a gravitational field can be detected by its bending of light. A distant galaxy in the same line of sight as a nearer one can form an 'Einstein ring' image around it; the light is deviated in passing through the nearer galaxy's gravitational field. If an Einstein ring is ever found around an empty patch of sky, a clump of dark matter will have been discovered. Similarly, says Daedalus, the light from a distant star or galaxy should be deviated in phase with any gravitational waves through which that light passes. An observer would see the object apparently vibrating back-and-forth in the sky, in time with the gravitational waves.