How do we know black holes exist? In September 2015, the LIGO gravitational wave detectors in the US made a measurement of two black holes smashing together. No matter what the orientation of the disc, you will see it as a ring because of the black hole’s strong gravity. “Einstein’s theory of general relativity fits all the observations made so far related to black holes. Maybe black holes millions of times more massive are different.

Source: The Express Tribune April 09, 2019 12:00 UTC