Gravitational waves from colossal black holes found using 'cosmic clocks'

You can't see or feel it, but everything around you -- including your own body -- is slowly shrinking and expanding. It's the weird, spacetime-warping effect of gravitational waves passing through our galaxy. New results are the first evidence of the gravitational wave background -- a sort of soup of spacetime distortions pervading the entire universe and long predicted to exist by scientists.