*In late 2015 (and announced in 2016), the LIGO instruments directly detected gravitational waves allegedly from colliding [[black hole]]s. See [[Gravitational waves]]. Unlike the waves from orbiting pulsars, that could only be detected by the loss of rotation energy, the waves from colliding black holes were strong enough to be detected directly. There is inherent circularity in this approach, however, because it relies on assumptions about the existence and nature of black holes which cannot be verified independently. | *In late 2015 (and announced in 2016), the LIGO instruments directly detected gravitational waves allegedly from colliding [[black hole]]s. See [[Gravitational waves]]. Unlike the waves from orbiting pulsars, that could only be detected by the loss of rotation energy, the waves from colliding black holes were strong enough to be detected directly. There is inherent circularity in this approach, however, because it relies on assumptions about the existence and nature of black holes which cannot be verified independently. |