John Michell first proposes the idea that…

November 1783 CE

John Michell first proposes the idea that there are such things as black holes, which he calls "dark stars", in a paper for the Philosophical Transactions of the Royal Society of London, read on November 27, 1783.

Having accepted Newton’s corpuscular theory of light, which posits that light consists of minuscule particles, he reasons that such particles, when emanated by a star, would be slowed down by its gravitational pull, and thought that it might therefore be possible to determine the star's mass based on the reduction in speed.

This insight led in turn to the recognition that a star's gravitational pull might be so strong that the escape velocity would exceed the speed of light.

Michell has calculated that this would be the case with a star more than five hundred times the size of the Sun.

Since light would not be able to escape such a star, it would be invisible.

In his own words:

If there should really exist in nature any bodies, whose density is not less than that of the sun, and whose diameters are more than 500 times the diameter of the sun, since their light could not arrive at us; or if there should exist any other bodies of a somewhat smaller size, which are not naturally luminous; of the existence of bodies under either of these circumstances, we could have no information from sight; yet, if any other luminous bodies should happen to revolve about them we might still perhaps from the motions of these revolving bodies infer the existence of the central ones with some degree of probability, as this might afford a clue to some of the apparent irregularities of the revolving bodies, which would not be easily explicable on any other hypothesis; but as the consequences of such a supposition are very obvious, and the consideration of them somewhat beside my present purpose, I shall not prosecute them any further.
("On the Means of Discovering the Distance, Magnitude, &c. of the Fixed Stars, in Consequence of the Diminution of the Velocity of Their Light, in Case Such a Diminution Should be Found to Take Place in any of Them, and Such Other Data Should be Procured from Observations, as Would be Farther Necessary for That Purpose. By the Rev. John Michell, B. D. F. R. S.” In a Letter to Henry Cavendish, Esq. F. R. S. and A. S." (PDF), Philosophical Transactions of the Royal Society of London 74 :35-57)

Michell suggests that there might be many "dark stars" in the universe, and today astronomers believe that black holes do indeed exist at the centers of most galaxies.

Similarly, Michell proposes that astronomers can detect "dark stars" by looking for star systems that behave gravitationally like two stars, but where only one star can be seen.

Michell argues that this will show the presence of a "dark star".

It is an extraordinarily accurate prediction.

All of the dozen candidate stellar black holes in our galaxy (the Milky Way) are in X-ray compact binary systems.

A dozen years after Michell comes up with the concept of black holes, the French mathematician Pierre-Simon Laplace will suggest essentially the same idea in his 1796 book, Exposition du Système du Monde.