More than a century before Albert Einstein revolutionized physics with his theory of general relativity, and nearly two centuries before astronomers accepted the existence of black holes, an English clergyman and scientist named John Michell proposed a startling idea. In 1783, Michell suggested that some stars might possess such immense gravity that even light could not escape from them. These invisible objects, which he called "dark stars," bear a remarkable resemblance to what we now know as black holes.
Visualisation of a black hole. Credit: NASA's Goddard Space Flight Center/Jeremy Schnittman
John Michell was born in 1724 in the village of Eakring, in Nottinghamshire, the son of Gilbert Michell, the parish rector, and his wife Obedience Gerrard. His early education was imparted at home alongside his younger brother and sister. Later, when the time came for Michell to enter university, he chose the prestigious Queens' College, Cambridge.
Michell stayed in Cambridge for more than 20 years in various posts, studying and teaching across disciplines including Hebrew, Greek, arithmetic, theology and geology. In 1767, he was appointed rector of St. Michael's Church of Thornhill, near Leeds, a post he held for the rest of his life. It was here, where he did most of his important scientific work.
In 1750, Michell published an eighty-page treatise on artificial magnets, in which he presented an easy and expeditious method of producing magnets that are superior to the best natural magnets. Michell also made several accurate observations about magnetism, such as the face that force between magnetic poles follows an inverse-square law.
In the aftermath of the devastating Lisbon earthquake of 1755, Michell published a ground-breaking study arguing that earthquakes propagate through the Earth as waves. At a time when many natural disasters were still explained in philosophical or theological terms, he approached the problem scientifically and used observations to support his conclusions. His work laid the foundations of modern seismology and earned him election to the Royal Society in 1760.
In 1767, Michell became the first scientist to apply statistical analysis to the distribution of stars. Studying groups such as the Pleiades, he demonstrated that many stars appeared too closely associated to be mere chance alignments. He concluded that they were physically connected and bound together by gravity. This was the first evidence for the existence of binary star systems and star clusters, an idea later confirmed by observations and now fundamental to astronomy.
Michell was also an important contributor to the Cavendish Experiment. He designed and built the torsion-balance apparatus intended to measure the gravitational attraction between masses and determine the Earth's density. Michell died before he could perform the experiment, and the apparatus passed to his friend Henry Cavendish, who successfully carried it out in 1797–1798. The torsion balance later became one of the most important instruments in the history of gravitational research.
But perhaps Michell’s most astonishing insight concerned the nature of stars.
At the time, scientists generally followed Isaac Newton's view that light consisted of tiny particles, known as corpuscles. Since gravity acted upon ordinary matter, Michell reasoned that it should also act upon these particles of light. Using Newton's law of gravity, Michell considered the concept of escape velocity, the speed required to break free from a body's gravitational pull. For Earth, this velocity is about 11.2 kilometers per second. For the Sun, it is much higher. Michell asked a simple question: What if a star were so massive that its escape velocity exceeded the speed of light?
If light consisted of particles, then those particles would be unable to escape the star's gravity. Any light emitted from the surface would be pulled back, rendering the star completely invisible.
In a paper presented to the Royal Society in 1783, Michell calculated that a star with the same density as the Sun but roughly 500 times larger in radius would possess this extraordinary property. Such an object would exist, exert gravity, and interact with neighbouring stars, yet remain forever hidden from view. In modern language, he had essentially described a black hole.
Michell referred to these hypothetical objects as “dark stars”. What makes his proposal particularly impressive is that he did not stop at the theoretical prediction. He also considered how such objects might be detected.
Since the dark star itself could not be seen, Michell suggested astronomers should search for visible stars whose motions indicated the gravitational influence of an unseen companion. This idea closely resembles a method today used to discover black hole candidates. Modern astronomers often infer the presence of a black hole by observing the motion of nearby stars orbiting an invisible object.
In effect, Michell proposed not only the existence of black-hole-like objects but also a strategy for finding them.
More than 130 years later, Einstein's theory of general relativity transformed our understanding of gravity. Instead of being a force acting across space, gravity became a consequence of the curvature of spacetime.
In 1916, the German physicist Karl Schwarzschild found a solution to Einstein's equations describing the gravitational field around a spherical mass. His work revealed a critical boundary known today as the Schwarzschild radius. For an object compressed within this radius, not even light can escape.
Remarkably, when Michell's Newtonian calculation is performed using the speed of light as the escape velocity, it yields exactly the same radius as Schwarzschild's relativistic solution. The underlying physics is entirely different, yet the numerical result is identical. It remains one of the most striking coincidences in the history of science.
Michell's concept of the "dark star" attracted little attention and was soon forgotten. One reason was the decline of Newton's corpuscular theory of light, on which the idea was based. During the 19th century, the wave theory of light gained widespread acceptance, making it difficult for scientists to imagine gravity trapping light in the manner Michell had proposed. Although the French mathematician Pierre-Simon Laplace later arrived at a similar concept independently, it too faded into obscurity. Only in the 20th century, after the development of general relativity, did the notion of black hole was born.
Michell's scientific papers were surprisingly few in number, yet each contained ideas decades or even centuries ahead of their time. He anticipated black holes, pioneered seismology, provided the first evidence for binary stars, developed the torsion balance later used to weigh the Earth, and advanced the study of magnetism.
Had his ideas received greater attention during his lifetime, John Michell might today be remembered alongside Newton, Herschel, and Cavendish as one of the defining scientific minds of the 18th century.
References:
# John Michell. Wikipedia
# The Country Parson Who Conceived of Black Holes. American Museum of Natural History
# November 27, 1783: John Michell anticipates black holes. American Physical Society
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