When supermassive black holes merge, they create a low thrum of gravitational waves that permeates the universe, and we may have just spotted it for the first time
Source:
https://www.newscientist.com/article/2264633-we-may-have-found-hints-of-gravitational-waves-permeating-the-universe/?utm_campaign=RSS%7CNSNS&utm_source=NSNS&utm_medium=RSS&utm_content=home