Spin may reveal black hole history
Multiple mergers may create pairs that coalesce to make gravitational waves
![merging black hole simulation](https://i0.wp.com/www.sciencenews.org/wp-content/uploads/2017/01/013017_ec_blackholemerger_feat_free.jpg?fit=860%2C460&ssl=1)
MERGERS REPEAT Pairs of black holes that merge to create gravitational waves could have formed from a sequence of prior black hole mergers. Now scientists have some up with a method for testing that idea.
R. Hurt/Caltech-JPL