Starting a recurring thread on BLACK HOLES. From history to our modern understanding and, in between, any bizarre facts about it.
1. The idea of "dark stars" - from where light cannot escape - became obvious since we figured in the late 1600s that the speed of light is indeed finite. Here is a quote by philosopher-scientist John Michell from 1784.
(Source: Wikipedia)
2. After Einstein published his breakthrough paper on Special Theory of Relativity in 1905, it was known: (i) nothing travels faster than the speed of light, (ii) speed of light is constant for all observers. Therefore, a "dark star" is 'black' for all observers of the Universe.