pulsar timing arrays

4

Mysteriously Quiet Space Baffles Researchers

“The emission of gravitational waves in these systems is a consequence of Einstein’s theory of General Relativity. Combine the existing observations with the calculation for the emission, and you get an estimate for the background noise from gravitational waves. The pulsar timing measurements we make from pulsars within our own galaxy should be sensitive to this noise from the gravitational waves. But the new measurement — the null result — is inconsistent with all existing models for the gravitational wave background in this frequency range.”

We live in a Universe full of galaxies, supermassive black holes, and violence. The violence is particularly relevant here, because every so often, these galaxies merge, and if they each contain a supermassive black hole, the gravitational wave “ripples” that get sent through space will literally shake and affect everything that’s in them. If you had a perfect clock — something that kept time perfectly that you could watch “tick” — you’d expect to see the timing of these ticks be affected. Astrophysics gives us these clocks: millisecond pulsars, in great abundance. Yet the Parkes Pulsar Timing Array project has just completed an 11-year survey of thousands of them, and found no evidence of the gravitational waves they were expecting.