Technology Review: By measuring the timing of pulsar signals and looking for variations, some astronomers believe that they will be able to find evidence that gravitational waves have passed through pulsar star systems. George Hobbs at the Australia Telescope National Facility in Epping and other astronomers are aware that they face significant difficulties, however. They have to compare actual measurements against model predictions, then account for any differences that may be caused by such factors as interstellar turbulence and variances in timing methods. Hobbs believes that any remaining differences would be the result of gravitational waves. He points out that there will be more data to work with as new pulsars are discovered and ever-more-sensitive radio telescopes are built.