Scientists have detected two unusual black hole mergers showing signs of “second-generation” origins — meaning each large black hole likely formed from an earlier merger. The gravitational-wave signals also matched Einstein’s predictions on spinning black holes, offering fresh proof of general relativity and new insights into how black holes grow in crowded st…Scientists have detected two unusual black hole mergers showing signs of “second-generation” origins — meaning each large black hole likely formed from an earlier merger. The gravitational-wave signals also matched Einstein’s predictions on spinning black holes, offering fresh proof of general relativity and new insights into how black holes grow in crowded st…