Gravitational Waves in the Night Sky

Nanograph and the other arrays are looking for correlations among many many pulsars. They want to see an overall effect where a bunch of pulsars are squeezed towards us and a bunch are squeezed away from us. These could be gravitational waves from like the mergers of supermassive black holes things that could have been washing over us basically our entire existence but we could not detect even with LIGO and Virgo.