Black holes were first conceived by English polymath John Michell in a paper completed in May 1783. Michell thought that the speed of light corpuscles emitted from a star was affected by the star’s gravitational attraction and, based on a then-reasonable estimate for the speed of light, he concluded, “If the semi-diameter of a sphere of the same density with the sun were to exceed that of the sun in the proportion of 500 to 1 … all light emitted from such a body would be made to return towards it, by its own proper gravity.”1 Thirteen years later Pierre Simon Laplace offered an independent proof for the existence of “invisible bodies” that could trap light.
According to the modern perspective of general relativity, a sphere of mass M will become a light-trapping black hole when its radius shrinks to the so-called Schwarzschild radius R = 2GM/...
