Did the Pulsar Timing Array actually detect colliding primordial black holes?
The universe is filled with gravitational waves. We know this thanks to the North American Nanohertz Observatory for Gravitational Waves (NANOGrav), which recently announced the first observations of long-wavelength gravitational waves rippling through the Milky Way. The waves are likely caused by supermassive black hole mergers, but can we prove it? Most of the gravitational … Read more