The existence of black holes is a disconcerting idea, especially when you consider that billions of them could populate the cosmos.
For decades in the 20th century, eminent physicists refused to believe that black holes could be real, ignoring what mathematics predicted. These skeptics included even Albert Einstein, whose own theory of general relativity made black holes possible.
However, there was one person who showed remarkable prescience about black holes, and he did so long before Einstein was born.
Using only the Newtonian lawsa little-known British cleric named John Michell anticipated these objects astronomically strange in some considerable and surprising ways, back in the 18th century.
Who was Michell, what did he predict, and why were his ideas largely forgotten?
Independent thinker
Michell was born in 1724 in the village of Eakring, England. He was the son of Gilbert Michell, the rector of the parish, and his wife Obedience Gerrard. Educated at home along with his younger brother and sister, John acquired a reputation as a quick and perceptive learner from an early age.
According to historian Russell McCormmach, his father Gilbert liked to quote a family friend who described John as having “the clearest head he had ever met.”
Gilbert valued the independence of thought and described himself as someone “not attached to any body or denomination of men in the world.”
The family followed the latitudinarian christianitya tradition that venerated the reason over excessive doctrine and which originated at Cambridge University under Isaac Newton. So when it came time for John to go to university, he went to Cambridge.
With an abundant supply of cafeterias and an intimate community of just 400 students, the college was an ideal setting for intellectual discourse. Michell remained there for more than 20 years in various positions, studying and teaching in disciplines such as Hebrew, Greek, arithmetic, theology and geology.
It was a committed experimentalist and, as Archibald Geikie, another biographer, says, “he liked to build his own devices… His rooms in the [universidad] “From Queens, with all its implements and machinery, sometimes looked like a workshop.”
It was also during his years at Cambridge that he began to show his capacity for scientific foresight.
In 1750 he published an article on magnetism, where he introduced at least one completely new law (the “inverse square law”) who promoted the application of magnets in navigation. In 1760, he published an article on the Mechanics of earthquakeswhere he described the stratified layers of the Earth now known to make up its “crust” and demonstrated how earthquakes move through these layers in the form of waves.
He also showed a way to estimate the epicenter and focus of the catastrophic Lisbon earthquake of 1755 and explored the idea that Underwater earthquakes could cause tsunamis.
After leaving Cambridge in 1764, he married Sarah Williamson and moved to Thornhill, Yorkshire, to follow in his father’s footsteps as parish rector. Sarah died the following year and Michell remarried Ann Brecknock in 1773.
In addition to his church work, he corresponded with other natural philosophers and intellectuals of the day, including the American polymath Benjamin Franklin.
From a 21st century perspective, the idea of a member of the Christian church being at the centre of scientific life may seem surprising. But, like most 18th century intellectuals, Michell did not make the distinction between religion and science.
No conflict between God and science
The introduction of the telescopes At the beginning of the 17th century it caused great philosophical agitation throughout Europe.
The fixed, observable hierarchy of God’s creation – the Earth and the heavens – was overthrown by what scientific historian Alexandre Koyré calls an “indefinite and even infinite Universe” that was to be understood by observing “its fundamental components and laws.”
But for thinkers like Michell, This revolution did not displace God, It simply renewed its mystery: the natural laws under investigation were still the laws of God.
As Newton had written in 1704: “Our duty to [Dios]as well as that of some towards others, will appear to us through the light of Nature.”
It was this Newtonian Christianity that Michell followed.
As McCormmach says, “the truths of his religion were in accord with the truths of nature.” Thus, in addition to his parish duties, Michell gradually turned his attention to the cosmology and, in particular, on the nature of gravity.
This was the realm in which he produced work that was both revolutionary and prophetic, even long after his own death.
Michell built his own reflecting telescope 3 metres and, in 1767, he was the first to apply the new mathematical methods of statistics to the study of visible stars, demonstrating that clusters such as the Pleiades could not be explained by a random distribution and must be a consequence of gravitational attraction.
In 1783, Michell’s friend Henry Cavendish wrote to him mentioning some difficulties Michell was having with the construction of a new, even larger telescope. “If your health does not permit you to continue with that,” he wrote, “I hope it will at least permit you the easier and less laborious task of weighing the world.”
It sounds like a joke, and perhaps it was intended to be funny, but Cavendish was referring to a real effort.
Michell had been working on a torsion balance, a device that would allow him to estimate the density of planet Earth measuring the gravitational attraction between lead weights. He died before he could use the apparatus, but after his death it passed to Cavendish, who carried out the experiment in 1797.
He calculated the density of the Earth to within 1% of the now accepted value.
The accuracy of Cavendish’s result was not surpassed until 1895, and a variation of Michell’s apparatus is still used today to measure the gravitational constant: the strength of gravitational attraction operating throughout the Universe.
In the same year as Cavendish’s letter, Michell published a paper containing a hypothesis which, though less scientifically enduring, was perhaps the most brilliant in its insight.
Using Newtonian principles, he began by explaining how the density of stars could be established by observing the way their gravitation affected other nearby bodies, for example the orbits of other stars or comets.
Michell then went on to discuss how the behavior of light could be used for similar purposes: “Let us now suppose that the particles of light attract one another in the same manner as all other bodies known to us… of which there can be no reasonable doubt, gravitation being, so far as we know (…), a universal law of nature.”
The particle or “corpuscular” theory of light had been proposed by Isaac Newton some 80 years earlier and, although no one had been able to prove it, it remained the dominant belief in Michell’s time.
Michell explained how the behavior of light under gravity could offer a way to calculate the density of starsat least hypothetically, especially if a star was “large enough to affect the speed of light emanating from it.”
Although the current understanding is that he was wrong about the impact of gravity on the speed of light (it does not slow down), his reasoning was sound.
Following the same principles, Michell deduced (this time correctly) that it was also possible that the gravity of the most massive astral bodies could completely dominate their own light rays.
For a star to achieve this, it would need to be the same density as the Sun and about 500 times its size. Initially, the light would escape from such a star, perhaps heading to nearby orbiting planets, but, Michell explained, “it would have to come back to the star, under its own gravity.”
Since light from such a star could not reach us, “we would not be able to have information with the naked eye,” but we might still be able to detect it from irregularities in the orbits of other nearby astral bodies caused by the gravity of the invisible star, “which would not be easily explained with any other hypothesis.”
These speculations, Michell explained, were “a little outside my present purpose,” but they contain perhaps the closest approximation to the idea of black holes possible under Newtonian physicsnot to mention an outline of a working method for identifying them.
Several black holes have been detected through the orbits of neighboring stars as suggested by Michell. Only in the In recent years, telescopic images have confirmed the indirect evidence.
According to McCormmach, the existence of invisible stars was a relatively common idea among scientists at the time. The same year that Michell published his article, several other astronomers corresponded in which they discussed stars that had become extinct.
In 1805, astronomer Edward Pigott published a paper suggesting the possibility of stars “which have never shown a glimmer of brilliancy.”
Although their true number could never be known, “would it then be too bold or visionary to assume that their number was equal to that of those endowed with light?” he asked.
In France and independently of Michell, the scholar Pierre-Simon Laplace promoted the idea of dark stars in the late 1790s.
However, soon after, new experiments reinforced the idea that light is composed of waves rather than massive particles, and the suggestion that it could be warped or trapped by gravity began to fall out of fashion.
He Michell’s astronomical work fell into oblivion and was not rediscovered until the second half of the 20th century.
Darkness
In his 1994 book “Black Holes and Time Warps,” physicist Kip Thorne describes the “stark contrast” between the enthusiasm with which Michell and his contemporaries embraced the idea of gravitationally invisible stars and the “widespread, almost universal twentieth-century resistance to black holes.”
The crucial difference, he concludes, is that Michell’s dark stars, though exotic, “they did not represent a threat to any cherished belief about nature” nor a challenge to “the permanence and stability of matter.”
As McCormmach points out, modern black holes, by contrast, are precisely that: “a hole in space-time, an infinite pit from which nothing can escape.”
Despite this, McCormach speculates that Michell, “who recognized ‘the infinite variety we find in the works of creation,’ would have no problem with our black holes.”
There is no way to test this claim, but given Michell’s extraordinary scientific imagination and his commitment to the Newtonian tradition of reason, it seems attractive.
Michell He died on April 21, 1793 at the age of 68.having remained rector at Thornhill until the end.
Other intellectuals of his time were – and are – much better known. They published more frequently and on more popular subjects. Michell, on the other hand, followed his instinct.
In McCormmach’s words, “He dealt with the scientific problems that interested himin any field, and pursued them as far as he wanted and no further; and published his work when he wanted, and only when he was completely satisfied with it.”
This explains to some extent the oblivion that weighed on his figure after his death: sacrificed impact and fame in the name of intellectual freedom.
As the Alexandrian astronomer Ibn al-Haytham had observed 700 years before Newton, the “seeker after truth” is not one who puts his trust in authorities, “but rather he who is suspicious of his faith in them… he who submits to discussion and demonstration.” Following this tradition, Michell, like his father, was self-taught and protected his scientific integrity by remaining detached from any “body or denomination of men.”
The Michell’s independence allowed him another freedom essential to original thought: that of imagination. According to McCormmach, he chose astronomy specifically because it offered new perspectives for theory. In his passion for scientific imagination, Michell anticipated the creativity of today’s theoretical physicists. As Einstein said in 1929, “Imagination surrounds the world.”
*This article was published on BBC Future. Click here to read the original version.
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