John Michell
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John Michell (; 25 December 1724 – 21 April 1793) was an
English English usually refers to: * English language * English people English may also refer to: Peoples, culture, and language * ''English'', an adjective for something of, from, or related to England ** English national ide ...
natural philosopher Natural philosophy or philosophy of nature (from Latin ''philosophia naturalis'') is the philosophical study of physics Physics is the natural science that studies matter, its fundamental constituents, its motion and behavior throu ...
and clergyman who provided pioneering insights into a wide range of scientific fields including
astronomy Astronomy () is a natural science that studies astronomical object, celestial objects and phenomena. It uses mathematics, physics, and chemistry in order to explain their origin and chronology of the Universe, evolution. Objects of interest ...
,
geology Geology () is a branch of natural science concerned with Earth and other astronomical objects, the features or rocks of which it is composed, and the processes by which they change over time. Modern geology significantly overlaps all other Ear ...
,
optics Optics is the branch of physics that studies the behaviour and properties of light, including its interactions with matter and the construction of instruments that use or detect it. Optics usually describes the behaviour of visible, ultraviole ...
, and
gravitation In physics, gravity () is a fundamental interaction which causes mutual attraction between all things with mass or energy. Gravity is, by far, the weakest of the four fundamental interactions, approximately 1038 times weaker than the stron ...
. Considered "one of the greatest unsung scientists of all time", he is the first person known to have proposed the existence of
black hole A black hole is a region of spacetime where gravitation, gravity is so strong that nothing, including light or other Electromagnetic radiation, electromagnetic waves, has enough energy to escape it. The theory of general relativity predicts t ...
s, and the first to have suggested that earthquakes travelled in (seismic) waves. Recognizing that
double star In observational astronomy, a double star or visual double is a pair of stars that appear close to each other as viewed from Earth, especially with the aid of optical telescopes. This occurs because the pair either forms a binary star (i.e. a bi ...
s were a product of mutual gravitation, he was the first to apply
statistics Statistics (from German language, German: ''wikt:Statistik#German, Statistik'', "description of a State (polity), state, a country") is the discipline that concerns the collection, organization, analysis, interpretation, and presentation of ...
to the study of the cosmos. He invented an apparatus to measure the
mass of the Earth An Earth mass (denoted as M_\mathrm or M_\oplus, where ⊕ is the standard astronomical symbol for Earth), is a unit of mass equal to the mass of the planet Earth. The current best estimate for the mass of Earth is , with a relative uncertainty ...
, and explained how to manufacture an artificial magnet. He has been called the father both of
seismology Seismology (; from Ancient Greek σεισμός (''seismós'') meaning "earthquake" and -λογία (''-logía'') meaning "study of") is the scientific study of earthquakes and the propagation of elastic waves through the Earth or through other ...
and of
magnetometry A magnetometer is a device that measures magnetic field or magnetic dipole moment. Different types of magnetometers measure the direction, strength, or relative change of a magnetic field at a particular location. A compass is one such device, ...
. According to one science journalist, "a few specifics of Michell's work really do sound like they are ripped from the pages of a twentieth century astronomy textbook." The
American Physical Society The American Physical Society (APS) is a not-for-profit membership organization of professionals in physics and related disciplines, comprising nearly fifty divisions, sections, and other units. Its mission is the advancement and diffusion of k ...
(APS) described Michell as being "so far ahead of his scientific contemporaries that his ideas languished in obscurity, until they were re-invented more than a century later". The Society stated that while "he was one of the most brilliant and original scientists of his time, Michell remains virtually unknown today, in part because he did little to develop and promote his own path-breaking ideas".


Early life, education and professional positions

John Michell was born in 1724 in
Eakring Eakring is a village and civil parish in the Newark and Sherwood district of Nottinghamshire, England. Its population at the 2011 Census was 419. There was sizeable oil production there in the mid-20th century. Geography The village lies between ...
, in Nottinghamshire, the son of Gilbert Michell, a priest, and Obedience Gerrard. Gilbert was the son of William Michell and Mary Taylor of
Kenwyn Kenwyn ( kw, Keynwynn) is a settlement and civil parish in Cornwall, England. The settlement is a suburb of the city of Truro and lies 0.5 mi (1 km) north of the city centre, within Truro parish, whereas Kenwyn parish covers an area w ...
, Cornwall; Obedience was the daughter of Ralph and Hannah Gerrard of London. He was educated at
Queens' College, Cambridge Queens' College is a constituent college of the University of Cambridge. Queens' is one of the oldest colleges of the university, founded in 1448 by Margaret of Anjou. The college spans the River Cam, colloquially referred to as the "light s ...
, and later became a Fellow of Queens'. He obtained his
M.A. A Master of Arts ( la, Magister Artium or ''Artium Magister''; abbreviated MA, M.A., AM, or A.M.) is the holder of a master's degree awarded by universities in many countries. The degree is usually contrasted with that of Master of Science. Tho ...
degree in 1752, and his B.D. degree in 1761. He was Tutor of the college from 1751 to 1763; Praelector in Arithmetic in 1751; Censor in Theology in 1752; Praelector in Geometry in 1753; Praelector in Greek in 1755 and 1759; Senior Bursar in 1756; Praelector in Hebrew in 1759 and 1762; Censor in Philosophy and Examiner in 1760. "He was nominated Rector of St Botolph's, Cambridge, on 28 March 1760, and held this living until June 1763." From 1762 to 1764, he held the Woodwardian Chair of Geology till he was obliged to relinquish it on his marriage. There is no surviving portrait of Michell; he is said to have been "a little short Man, of a black Complexion, and fat".He was thus described by a contemporary commentator: "John Michell, BD is a little short Man, of a black Complexion, and fat; but having no Acquaintance with him, can say little of him. I think he had the care of St. Botolph's Church Cambridge, while he continued Fellow of Queen's College, where he was esteemed a very ingenious Man, and an excellent Philosopher. He has published some things in that way, on the
Magnet A magnet is a material or object that produces a magnetic field. This magnetic field is invisible but is responsible for the most notable property of a magnet: a force that pulls on other ferromagnetic materials, such as iron, steel, nickel, ...
and
Electricity Electricity is the set of physical phenomena associated with the presence and motion of matter that has a property of electric charge. Electricity is related to magnetism, both being part of the phenomenon of electromagnetism, as described ...
." Cole MSS XXXIII, 156, British Library.
In 1910, Sir
Edmund Whittaker Sir Edmund Taylor Whittaker (24 October 1873 – 24 March 1956) was a British mathematician, physicist, and historian of science. Whittaker was a leading mathematical scholar of the early 20th-century who contributed widely to applied mathema ...
observed that during the century after
Isaac Newton Sir Isaac Newton (25 December 1642 – 20 March 1726/27) was an English mathematician, physicist, astronomer, alchemist, theologian, and author (described in his time as a "natural philosopher"), widely recognised as one of the grea ...
's death, "the only natural philosopher of distinction who lived and taught at Cambridge was Michell", although his "researches seem to have attracted little or no attention among his collegiate contemporaries and successors, who silently acquiesced when his discoveries were attributed to others, and allowed his name to perish entirely from Cambridge tradition". Michell proceeded to take up clerical positions in Compton and then Havant, both in Hampshire. During this period he unsuccessfully sought positions at Cambridge, and as
Astronomer Royal Astronomer Royal is a senior post in the Royal Households of the United Kingdom. There are two officers, the senior being the Astronomer Royal dating from 22 June 1675; the junior is the Astronomer Royal for Scotland dating from 1834. The post ...
. In 1767, he was appointed rector of St. Michael's Church of Thornhill, near Leeds, Yorkshire, England, a post he held for the rest of his life. He did most of his important scientific work in Thornhill, where he died on 21 April 1793, aged 68. He is buried there. After local pressure, a blue plaque went up on the church wall to commemorate him.


Scientific work

In 1750, Michell published at Cambridge a work of some eighty pages entitled "A Treatise of Artificial Magnets", in which he presented an easy and expeditious method of producing magnets that are superior to the best natural magnets. Besides the description of the method of magnetization which still bears his name, this work contains a variety of accurate observations about magnetism, and features a lucid exposition of the nature of magnetic induction. At one point, Michell attempted to measure the radiation pressure of light by focusing sunlight onto one side of a compass needle. The experiment was not a success: the needle melted.


Geology and seismology

Until the late 20th century Michell was considered important primarily because of his work on geology. His most important geological essay, written after the
1755 Lisbon earthquake The 1755 Lisbon earthquake, also known as the Great Lisbon earthquake, impacted Portugal, the Iberian Peninsula, and Northwest Africa on the morning of Saturday, 1 November, Feast of All Saints, at around 09:40 local time. In combination with ...
, was entitled "Conjectures concerning the Cause and Observations upon the Phaenomena of Earthquakes" (''
Philosophical Transactions ''Philosophical Transactions of the Royal Society'' is a scientific journal published by the Royal Society. In its earliest days, it was a private venture of the Royal Society's secretary. It was established in 1665, making it the first journa ...
'', li. 1760). In this paper he introduced the idea that earthquakes spread out as waves through the Earth, and that they involve the offsets in geological strata now known as faults. He was able to estimate both the epicentre and the focus of the Lisbon earthquake, and may also have been the first to suggest that a tsunami is caused by a submarine earthquake. Michell's essay not only provided insights on earthquakes but also, more broadly, represented an advance in the understanding of the geology of the Earth's crust. He recognized that the Earth is composed "of regular and uniform strata", some of which have been interrupted by upheavals. "The most important part of Michell's Earthquake paper", in the view of one commentator, "is the account which it contains of what is now known as 'the crust of the Earth.'" Exhibiting a remarkable knowledge of the geological strata in various parts of England and abroad, he drew on his own observations to advance the understanding of sedimentary stratigraphy and was the first to define the Mesozoic stratigraphy in the U.K. In 1760, as a result of this work, he was elected a member of the Royal Society. A 1788 letter to
Henry Cavendish Henry Cavendish ( ; 10 October 1731 – 24 February 1810) was an English natural philosopher and scientist who was an important experimental and theoretical chemist and physicist. He is noted for his discovery of hydrogen, which he termed "infl ...
indicated that Michell continued to be interested in geology several decades after his paper on earthquakes.


Magnetism

Michell studied magnetism and discovered the "inverse-square law", the fact that the magnetic force exerted by each pole of a magnet decreases in proportion to the square of the distance between them. His 1750 paper ''Treatise of Artificial Magnets'', which was written for seamen and instrument makers and intended as a practical manual on how to make magnets, included a list of the "Properties of Magnetical Bodies" that represented a major contribution to the understanding of magnetism.


Gravity

Michell devised a torsion balance for measuring the mass of the Earth, but died before he could use it. His instrument passed into the hands of his lifelong friend
Henry Cavendish Henry Cavendish ( ; 10 October 1731 – 24 February 1810) was an English natural philosopher and scientist who was an important experimental and theoretical chemist and physicist. He is noted for his discovery of hydrogen, which he termed "infl ...
, who first performed in 1798 the experiment now known as the
Cavendish Experiment The Cavendish experiment, performed in 1797–1798 by English scientist Henry Cavendish, was the first experiment to measure the force of gravity between masses in the laboratory and the first to yield accurate values for the gravitational consta ...
. Placing two 1-kg lead balls at the ends of a six-foot rod, he suspended the rod horizontally by a fibre attached to its centre. Then he placed a massive lead ball beside each of the small ones, causing a gravitational attraction that led the rod to turn clockwise. By measuring the rod's movement, Cavendish was able to calculate the force exerted by each of the large balls on the 1-kg balls. From these calculations, he was able to provide an accurate estimate of the gravitational constant and of the mass and average density of the Earth. Cavendish gave Michell full credit for his accomplishment. In 1987, gravity researcher A. H. Cook wrote:
The most important advance in experiments on gravitation and other delicate measurements was the introduction of the torsion balance by Michell and its use by Cavendish. It has been the basis of all the most significant experiments on gravitation ever since.


Double stars

Michell was the first person to apply the new mathematics of statistics to the study of the stars, and demonstrated in a 1767 paper that many more stars occur in pairs or groups than a perfectly random distribution could account for. He focused his investigation on the
Pleiades The Pleiades (), also known as The Seven Sisters, Messier 45 and other names by different cultures, is an asterism and an open star cluster containing middle-aged, hot B-type stars in the north-west of the constellation Taurus. At a distance of ...
cluster, and calculated that the likelihood of finding such a close grouping of stars was about one in half a million. He concluded that the stars in these double or multiple star systems might be drawn to one another by gravitational pull, thus providing the first evidence for the existence of binary stars and star clusters. His work on double stars may have influenced his friend
William Herschel Frederick William Herschel (; german: Friedrich Wilhelm Herschel; 15 November 1738 – 25 August 1822) was a German-born British astronomer and composer. He frequently collaborated with his younger sister and fellow astronomer Caroline H ...
's research on the same topic.


Black holes

In a paper for the ''Philosophical Transactions of the Royal Society of London'', read on 27 November 1783, Michell was the first to propose the existence of
black hole A black hole is a region of spacetime where gravitation, gravity is so strong that nothing, including light or other Electromagnetic radiation, electromagnetic waves, has enough energy to escape it. The theory of general relativity predicts t ...
s, which he called "dark stars". Having accepted Newton's corpuscular theory of light, which posited that light consists of minuscule particles, he reasoned that such particles, when emanated by a star, would be slowed down by its gravitational pull, and 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 calculated that this would be the case with a star more than 500 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: Michell suggested 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 proposed that astronomers could detect "dark stars" by looking for star systems which behaved gravitationally like two stars, but where only one star could be seen. Michell argued that this would show the presence of a "dark star". It was 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. Michell's ideas about gravity and light interested William Herschel, who tried to test them with his powerful telescopes. A few years after Michell came up with the concept of black holes, the French mathematician
Pierre-Simon Laplace Pierre-Simon, marquis de Laplace (; ; 23 March 1749 – 5 March 1827) was a French scholar and polymath whose work was important to the development of engineering, mathematics, statistics, physics, astronomy, and philosophy. He summarized ...
suggested essentially the same idea in his 1796 book, ''Exposition du Système du Monde''. It has been written that Michell was so far ahead of his time in regard to black holes that the idea "made little impression" on his contemporaries. "He died in quiet obscurity", states the American Physical Society, "and his notion of a 'dark star' was forgotten until his writings re-surfaced in the 1970s."


Telescopes

Michell constructed telescopes for his own use. One of them, a
reflecting telescope A reflecting telescope (also called a reflector) is a telescope that uses a single or a combination of curved mirrors that reflect light and form an image. The reflecting telescope was invented in the 17th century by Isaac Newton as an alternati ...
with a 10-foot focal length and a 30-inch aperture, was bought by the distinguished astronomer
William Herschel Frederick William Herschel (; german: Friedrich Wilhelm Herschel; 15 November 1738 – 25 August 1822) was a German-born British astronomer and composer. He frequently collaborated with his younger sister and fellow astronomer Caroline H ...
after Michell's death. The two men had many interests in common, and exchanged letters at least twice, but only one record suggests that they ever met. Herschel recorded having visited and seen Michell's telescope while in the area in 1792; Michell was already frail, and his telescope was in disrepair. Herschel bought the telescope the following year, for £30.


Other professional activities

Michell also wrote a paper on surveying that his biographer has described as "elegant" in theory. Michell was elected a member of the Royal Society. He was first invited to meetings of the Royal Society in 1751 as a guest of Sir George Savile, who would become his patron. He later attended meetings "one to four times a year", while at Cambridge. His paper on the cause of earthquakes was read before the Society beginning on 28 February 1760, leading to a recommendation by Savile and another member that Michell be invited to join the Society. He was elected a member on 12 June 1760. Michell followed his work in seismology with work in astronomy, and after publishing his findings in 1767 he served on an astronomical committee of the Royal Society. More recently, Michell has become known for his letter to Cavendish, published in 1784, on the effect of gravity on light. This paper was rediscovered in the 1970s and is now recognised as anticipating several astronomical ideas that had been considered to be 20th century innovations. Michell is now credited with being the first to study the case of a heavenly object massive enough to prevent light from escaping (the concept of
escape velocity In celestial mechanics, escape velocity or escape speed is the minimum speed needed for a free, non- propelled object to escape from the gravitational influence of a primary body, thus reaching an infinite distance from it. It is typically ...
was well known at the time). Such an object, which he called a dark star, would not be directly visible, but could be identified by the motions of a companion star if it was part of a binary system. The classical minimum radius for escape assuming light behaved like particles of matter is numerically equal to the
Schwarzschild Radius The Schwarzschild radius or the gravitational radius is a physical parameter in the Schwarzschild solution to Einstein's field equations that corresponds to the radius defining the event horizon of a Schwarzschild black hole. It is a characteristic ...
in
general relativity General relativity, also known as the general theory of relativity and Einstein's theory of gravity, is the geometric theory of gravitation published by Albert Einstein in 1915 and is the current description of gravitation in modern physics ...
. Michell also suggested using a
prism Prism usually refers to: * Prism (optics), a transparent optical component with flat surfaces that refract light * Prism (geometry), a kind of polyhedron Prism may also refer to: Science and mathematics * Prism (geology), a type of sedimentary ...
to measure what is now known as
gravitational redshift In physics and general relativity, gravitational redshift (known as Einstein shift in older literature) is the phenomenon that electromagnetic waves or photons travelling out of a gravitational well (seem to) lose energy. This loss of energy ...
, the gravitational weakening of starlight due to the surface gravity of the source. Michell acknowledged that some of these ideas were not technically practical at the time, but wrote that he hoped they would be useful to future generations. By the time that Michell's paper was rediscovered nearly two centuries later, these ideas had been reinvented by others.


Personal life

Michell was a man of "wide latitude in religious belief". He was described by a contemporary as "a little short man, of black complexion, and fat", and was "esteemed a very ingenious Man, and an excellent Philosopher." During his years at Thornhill, he welcomed visitors including
Benjamin Franklin Benjamin Franklin ( April 17, 1790) was an American polymath who was active as a writer, scientist, inventor, statesman, diplomat, printer, publisher, and political philosopher. Encyclopædia Britannica, Wood, 2021 Among the leading inte ...
,
Joseph Priestley Joseph Priestley (; 24 March 1733 – 6 February 1804) was an English chemist, natural philosopher, separatist theologian, grammarian, multi-subject educator, and liberal political theorist. He published over 150 works, and conducted exp ...
,
Jan Ingenhousz Jan (or John) Ingenhousz or Ingen-Housz FRS (8 December 1730 – 7 September 1799) was a Dutch-born British physiologist, biologist and chemist. He is best known for discovering photosynthesis by showing that light is essential to the process ...
, and
Henry Cavendish Henry Cavendish ( ; 10 October 1731 – 24 February 1810) was an English natural philosopher and scientist who was an important experimental and theoretical chemist and physicist. He is noted for his discovery of hydrogen, which he termed "infl ...
(the discoverer of hydrogen). Michell wrote to Franklin in 1767 describing his first visit to Thornhill, "the place I told you I was going to remove to". Priestley lived in nearby Birstall for a time. It was at Michell's rectory opposite the church that Priestley and Ingenhousz met for the first time. At the same meeting
John Smeaton John Smeaton (8 June 1724 – 28 October 1792) was a British civil engineer responsible for the design of bridges, canals, harbours and lighthouses. He was also a capable mechanical engineer and an eminent physicist. Smeaton was the fir ...
was introduced to Benjamin Franklin and together they viewed the canal that Smeaton had just finished constructing nearby. Michell also helped Smeaton revise his book on the
Eddystone Lighthouse The Eddystone Lighthouse is a lighthouse that is located on the dangerous Eddystone Rocks, south of Rame Head in Cornwall, England. The rocks are submerged below the surface of the sea and are composed of Precambrian gneiss. View at 1:50000 ...
. Michell's first wife was Sarah Williamson (1727–1765), daughter of Luke Williamson and Sutton Holmes, "a young lady of considerable fortune", whom he married in 1764 and who unfortunately died only a year later, in 1765. On 13 February 1773, in Newark, Nottinghamshire, he married Ann Brecknock (1736-1805), daughter of Matthew and Ann Brecknock of Nottinghamshire. They had one child, Mary, who married Sir Thomas Turton of Leeds, son of William Turton Esq. of Kingston Lisle, Berkshire, and Jane Clarke of Hertford, Hertfordshire. Michell's younger brother Gilbert was a merchant in London who later lived with Michell in Thornhill, where the two brothers were active in local real estate, purchasing many properties in the West Riding of Yorkshire.


Biographies

Michell is the subject of the book ''Weighing the World: The Reverend John Michell of Thornhill'' (2012) by Russell McCormmach.


Selected publications

*''Observations on the Comet of January 1760 at Cambridge'', ''
Philosophical Transactions ''Philosophical Transactions of the Royal Society'' is a scientific journal published by the Royal Society. In its earliest days, it was a private venture of the Royal Society's secretary. It was established in 1665, making it the first journa ...
'' (1760) *''Conjectures Concerning the Cause and Observations upon the Phaenomena of Earthquakes'', ibid. (1760) *''A Recommendation of Hadley's Quadrant for Surveying'', ibid. (1765) *''Proposal of a Method for measuring Degrees of Longitude upon Parallels of the Equator'', ibid. (1766) *''An Inquiry into the Probable Parallax and Magnitude of the Fixed Stars'', ibid. (1767) *''On the Twinkling of the Fixed Stars'', ibid. (1767) *


References


Sources

* * Eisenstaedt, Jean, ''Avant Einstein Relativité, lumière, gravitation'', Paris: Seuil (2005) * * *
Christa Jungnickel Christa Jungnickel (11 April 1935 – 12 August 1990) was a German-American historian of science. Life Jungnickel was originally from Germany, one of three daughters of a German soldier who was lost in Russia during World War II. As a teenager, ...
and
Russell McCormmach Russell Keith McCormmach (born 9 October 1933), the husband of the late Christa Jungnickel, is an American historian of physics. McCormmach grew up in Walla Walla, Washington and studied physics at Washington State College with bachelor's degree i ...
,
Cavendish
', American Philosophical Society, Philadelphia, 1996, . * * *


External links



Description of Michell's theory of black holes * * ttps://books.google.com/books?id=Zo0SDb-UdE8C&pg=PA92 John Michell biography, from "Our Place in the Universe" by Norman K. Glendenning* {{DEFAULTSORT:Michell, John 1724 births 1793 deaths 18th-century British astronomers English geologists 18th-century English Anglican priests Fellows of the Royal Society Alumni of Queens' College, Cambridge Fellows of Queens' College, Cambridge Woodwardian Professors of Geology