Sir James Hopwood Jeans (11 September 187716 September 1946) was an English

physicist A physicist is a scientist who specializes in the field of physics, which encompasses the interactions of matter and energy at all length and time scales in the physical universe. Physicists generally are interested in the root or ultimate cau ...

astronomer An astronomer is a scientist in the field of astronomy who focuses their studies on a specific question or field outside the scope of Earth. They observe astronomical objects such as stars, planets, moons, comets and galaxies – in either ...

and

mathematician A mathematician is someone who uses an extensive knowledge of mathematics in their work, typically to solve mathematical problems. Mathematicians are concerned with numbers, data, quantity, structure, space, models, and change. History On ...

Early life

Born in

Ormskirk Ormskirk is a market town in the West Lancashire district of Lancashire, England, north of Liverpool, northwest of St Helens, southeast of Southport and southwest of Preston. Ormskirk is known for its gingerbread. Geography and administ ...

Lancashire Lancashire ( , ; abbreviated Lancs) is the name of a historic county, ceremonial county, and non-metropolitan county in North West England. The boundaries of these three areas differ significantly. The non-metropolitan county of Lancas ...

, the son of

William Tulloch Jeans William Tulloch Jeans (1848–1907) was a British parliamentary journalist and author. Career Jeans was parliamentary correspondent for ''The Globe'', and was widely known for and consulted on his knowledge of parliamentary principle. In their 1 ...

, a parliamentary correspondent and author. Jeans was educated at Merchant Taylors' School, Wilson's Grammar School,

Camberwell Camberwell () is a district of South London, England, in the London Borough of Southwark, southeast of Charing Cross. Camberwell was first a village associated with the church of St Giles and a common of which Goose Green is a remnant. This ...

and

Trinity College, Cambridge Trinity College is a constituent college of the University of Cambridge. Founded in 1546 by King Henry VIII, Trinity is one of the largest Cambridge colleges, with the largest financial endowment of any college at either Cambridge or Oxford. ...

. As a gifted student, Jeans was counselled to take an aggressive approach to the Cambridge Mathematical Tripos competition:

Career

Jeans was elected

Fellow A fellow is a concept whose exact meaning depends on context. In learned or professional societies, it refers to a privileged member who is specially elected in recognition of their work and achievements. Within the context of higher education ...

of Trinity College in October 1901, and taught at Cambridge, but went to

Princeton University Princeton University is a private research university in Princeton, New Jersey. Founded in 1746 in Elizabeth as the College of New Jersey, Princeton is the fourth-oldest institution of higher education in the United States and one of the ...

in 1904 as a professor of applied mathematics. He returned to Cambridge in 1910. He made important contributions in many areas of physics, including quantum theory, the theory of

radiation In physics, radiation is the emission or transmission of energy in the form of waves or particles through space or through a material medium. This includes: * ''electromagnetic radiation'', such as radio waves, microwaves, infrared, visi ...

and

stellar evolution Stellar evolution is the process by which a star changes over the course of time. Depending on the mass of the star, its lifetime can range from a few million years for the most massive to trillions of years for the least massive, which is cons ...

. His analysis of rotating bodies led him to conclude that

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 summarize ...

's theory that the solar system formed from a single cloud of gas was incorrect, proposing instead that the planets condensed from material drawn out of the sun by a hypothetical catastrophic near-collision with a passing star. This theory is not accepted today. Jeans, along with

Arthur Eddington Sir Arthur Stanley Eddington (28 December 1882 – 22 November 1944) was an English astronomer, physicist, and mathematician. He was also a philosopher of science and a populariser of science. The Eddington limit, the natural limit to the lumi ...

, is a founder of British

cosmology Cosmology () is a branch of physics and metaphysics dealing with the nature of the universe. The term ''cosmology'' was first used in English in 1656 in Thomas Blount's ''Glossographia'', and in 1731 taken up in Latin by German philosopher ...

. In 1928, Jeans was the first to conjecture a

steady state cosmology In cosmology, the steady-state model, or steady state theory is an alternative to the Big Bang theory of evolution of the universe. In the steady-state model, the density of matter in the expanding universe remains unchanged due to a continuous ...

based on a hypothesized continuous creation of matter in the universe. In his book ''Astronomy and Cosmology'' (1928) he stated: "The type of conjecture which presents itself, somewhat insistently, is that the centers of the nebulae are of the nature 'singular points' at which matter is poured into our universe from some other, and entirely extraneous spatial dimension, so that, to a denizen of our universe, they appear as points at which matter is being continually created." This theory fell out of favour when the 1965 discovery of the

cosmic microwave background In Big Bang cosmology the cosmic microwave background (CMB, CMBR) is electromagnetic radiation that is a remnant from an early stage of the universe, also known as "relic radiation". The CMB is faint cosmic background radiation filling all spac ...

was widely interpreted as the tell-tale signature of the

Big Bang The Big Bang event is a physical theory that describes how the universe expanded from an initial state of high density and temperature. Various cosmological models of the Big Bang explain the evolution of the observable universe from the ...

. His scientific reputation is grounded in the monographs ''The Dynamical Theory of Gases'' (1904), ''Theoretical Mechanics'' (1906), and ''Mathematical Theory of Electricity and Magnetism'' (1908). After retiring in 1929, he wrote a number of books for the lay public, including ''The Stars in Their Courses'' (1931), ''

The Universe Around Us ''The Universe Around Us'' is a science book written by English astrophysicist Sir James Jeans, first published in 1929 by the Syndics of the Cambridge University Press. Editions * First Edition...1929 ...Reprinted...1929, 1930 * Second Edit ...

'', ''Through Space and Time'' (1934), ''The New Background of Science'' (1933), and ''

The Mysterious Universe ''The Mysterious Universe'' is a popular science book by the British astrophysicist Sir James Jeans, first published in 1930 by the Cambridge University Press. In the United States, it was published by Macmillan Publishers (United States), Macmil ...

.'' These books made Jeans fairly well known as an expositor of the revolutionary scientific discoveries of his day, especially in relativity and

physical cosmology Physical cosmology is a branch of cosmology concerned with the study of cosmological models. A cosmological model, or simply cosmology, provides a description of the largest-scale structures and dynamics of the universe and allows study of f ...

. In 1939, the

Journal of the British Astronomical Association The ''Journal of the British Astronomical Association'' is a peer-reviewed scientific journal of astronomy published by the British Astronomical Association since October 1890. It is currently edited by Philip Jennings and publishes original resear ...

reported that Jeans was going to stand as a candidate for parliament for the Cambridge University constituency. The election, expected to take place in 1939 or 1940, did not take place until 1945, and without his involvement. He also wrote the book ''Physics and Philosophy'' (1943) where he explores the different views on reality from two different perspectives: science and philosophy. On his religious views, Jeans was an agnostic

Freemason Freemasonry or Masonry refers to fraternal organisations that trace their origins to the local guilds of stonemasons that, from the end of the 13th century, regulated the qualifications of stonemasons and their interaction with authorities ...

Personal life

Jeans married twice, first to the American poet

Charlotte Tiffany Mitchell Charlotte ( ) is the most populous city in the U.S. state of North Carolina. Located in the Piedmont region, it is the county seat of Mecklenburg County. The population was 874,579 at the 2020 census, making Charlotte the 16th-most popu ...

in 1907, who died, and then to the Austrian

organ Organ may refer to: Biology * Organ (biology), a part of an organism Musical instruments * Organ (music), a family of keyboard musical instruments characterized by sustained tone ** Electronic organ, an electronic keyboard instrument ** Hammond ...

ist and

harpsichord A harpsichord ( it, clavicembalo; french: clavecin; german: Cembalo; es, clavecín; pt, cravo; nl, klavecimbel; pl, klawesyn) is a musical instrument played by means of a keyboard. This activates a row of levers that turn a trigger mechanism ...

ist Suzanne Hock (better known as

Susi Jeans Susi may refer to: * 933 Susi, a minor planet orbiting the Sun *Susi Air, an Indonesian airline * Sydney University Stellar Interferometer, an optical interferometer in Sydney, Australia People Given name * Susi Erdmann (born 1968), German luger ...

) in 1935. Susi and Jeans had three children: George, Christopher, and Catherine. At Merchant Taylors' School there is a James Jeans Academic Scholarship for the candidate in the entrance exams who displays outstanding results across the spectrum of subjects, notably in mathematics and the sciences.

Major accomplishments

One of Jeans' major discoveries, named

Jeans length In stellar physics, the Jeans instability causes the collapse of interstellar gas clouds and subsequent star formation, named after James Jeans. It occurs when the internal gas pressure is not strong enough to prevent gravitational collapse of a ...

, is a critical radius of an

interstellar cloud An interstellar cloud is generally an accumulation of gas, plasma, and dust in our and other galaxies. Put differently, an interstellar cloud is a denser-than-average region of the interstellar medium, the matter and radiation that exists in the ...

in space. It depends on the temperature, and density of the cloud, and the mass of the particles composing the cloud. A cloud that is smaller than its Jeans length will not have sufficient gravity to overcome the repulsive gas pressure forces and condense to form a star, whereas a cloud that is larger than its Jeans length will collapse. :

\lambda_J=\sqrt

Jeans came up with another version of this equation, called Jeans mass or

Jeans instability In stellar physics, the Jeans instability causes the collapse of interstellar gas clouds and subsequent star formation, named after James Jeans. It occurs when the internal gas pressure is not strong enough to prevent gravitational collapse of ...

, that solves for the critical mass a cloud must attain before being able to collapse. Jeans also helped to discover the Rayleigh–Jeans law, which relates the energy density of

black-body radiation Black-body radiation is the thermal electromagnetic radiation within, or surrounding, a body in thermodynamic equilibrium with its environment, emitted by a black body (an idealized opaque, non-reflective body). It has a specific, continuous spe ...

to the temperature of the emission source. :

f(\lambda) = 8\pi c \frac

Jeans is also credited with calculating the rate of

atmospheric escape Atmospheric escape is the loss of planetary atmospheric gases to outer space. A number of different mechanisms can be responsible for atmospheric escape; these processes can be divided into thermal escape, non-thermal (or suprathermal) escape, and ...

from a planet due to kinetic energy of the gas molecules, a process known as Jeans Escape.

Idealism

In an interview published in ''

The Observer ''The Observer'' is a British newspaper published on Sundays. It is a sister paper to ''The Guardian'' and '' The Guardian Weekly'', whose parent company Guardian Media Group Limited acquired it in 1993. First published in 1791, it is the ...

'' (London), when asked the question "Do you believe that life on this planet is the result of some sort of accident, or do you believe that it is a part of some great scheme?", he replied:

Awards and honours

Fellow of the Royal Society Fellowship of the Royal Society (FRS, ForMemRS and HonFRS) is an award granted by the judges of the Royal Society of London to individuals who have made a "substantial contribution to the improvement of natural knowledge, including mathemati ...

in May 1906 *

Bakerian Lecture The Bakerian Medal is one of the premier medals of the Royal Society that recognizes exceptional and outstanding science. It comes with a medal award and a prize lecture. The medalist is required to give a lecture on any topic related to physical ...

Royal Society The Royal Society, formally The Royal Society of London for Improving Natural Knowledge, is a learned society and the United Kingdom's national academy of sciences. The society fulfils a number of roles: promoting science and its benefits, re ...

in 1917. *

Royal Medal The Royal Medal, also known as The Queen's Medal and The King's Medal (depending on the gender of the monarch at the time of the award), is a silver-gilt medal, of which three are awarded each year by the Royal Society, two for "the most important ...

of the

in 1919. *

Hopkins Prize Hopkins is an English, Welsh and Irish patronymic surname. The English name means "son of Hob". ''Hob'' was a diminutive of ''Robert'', itself deriving from the Germanic warrior name ''Hrod-berht'', translated as "renowned-fame". The Robert s ...

of the

Cambridge Philosophical Society The Cambridge Philosophical Society (CPS) is a scientific society at the University of Cambridge. It was founded in 1819. The name derives from the medieval use of the word philosophy to denote any research undertaken outside the fields of l ...

1921–1924. *

Gold Medal of the Royal Astronomical Society The Gold Medal of the Royal Astronomical Society is the highest award given by the Royal Astronomical Society (RAS). The RAS Council have "complete freedom as to the grounds on which it is awarded" and it can be awarded for any reason. Past awar ...

in 1922. * He was

knight A knight is a person granted an honorary title of knighthood by a head of state (including the Pope) or representative for service to the monarch, the Christian denomination, church or the country, especially in a military capacity. Knighthood ...

ed in 1928. *

Franklin Medal The Franklin Medal was a science award presented from 1915 until 1997 by the Franklin Institute located in Philadelphia, Pennsylvania, U.S. It was founded in 1914 by Samuel Insull. The Franklin Medal was the most prestigious of the various awar ...

of the

Franklin Institute The Franklin Institute is a science museum and the center of science education and research in Philadelphia, Pennsylvania. It is named after the American scientist and statesman Benjamin Franklin. It houses the Benjamin Franklin National Memori ...

in 1931. * In 1933 Jeans was invited to deliver the Royal Institution Christmas Lecture on ''Through Space and Time''. * Mukerjee Medal of the Indian Association for the Cultivation of Science in 1937. * President of the 25th session of the Indian Science Congress in 1938. * Calcutta Medal of the

Indian Science Congress Association Indian Science Congress Association(ISCA) is a premier scientific organisation of India with headquarters at Kolkata, West Bengal. The association started in the year 1914 in Kolkata and it meets annually in the first week of January. It has a ...

in 1938. * Lorimer Medal of the

Astronomical Society of Edinburgh The Astronomical Society of Edinburgh (ASE) is an association of amateur astronomers and other individuals interested in astronomy, which is based in Edinburgh, Scotland. The objectives are to encourage astronomical study and observation and to ...

in 1938 for which he gave the Lorimer Lecture: ''The Depths of Space''. * Member of the

Order of Merit The Order of Merit (french: link=no, Ordre du Mérite) is an order of merit for the Commonwealth realms, recognising distinguished service in the armed forces, science, art, literature, or for the promotion of culture. Established in 1902 by ...

in 1939. * The crater

Jeans Jeans are a type of pants or trousers made from denim or dungaree cloth. Often the term "jeans" refers to a particular style of trousers, called "blue jeans", with copper-riveted pockets which were invented by Jacob W. Davis in 1871 and pa ...

on the Moon is named after him, as is the crater

on Mars. * The String Quartet No.7 by Robert Simpson was written in tribute to him on the centenary of his birth, 1977.

Bibliography

* * * * * * * * * * * * * * *

References

Sources

* * (quoting Jeans, The Mysterious Universe, p. 134). * *

External links

*
Britannica article
includes photo * ;Works of Jeans available online from the

Internet Archive The Internet Archive is an American digital library with the stated mission of "universal access to all knowledge". It provides free public access to collections of digitized materials, including websites, software applications/games, music, ...

*1904.
The Dynamical Theory of Gases
' *1906.
Theoretical Mechanics
' *1908.
Mathematical Theory of Electricity and Magnetism
' *1947.
The Growth of Physical Science
' {{DEFAULTSORT:Jeans, James Hopwood 1877 births 1946 deaths 20th-century English mathematicians Alumni of Trinity College, Cambridge British agnostics 20th-century British astronomers British physicists English agnostics English Freemasons English physicists Fellows of the Royal Society Fellows of Trinity College, Cambridge Fluid dynamicists Idealists Knights Bachelor Members of the Order of Merit Metaphysicians Ontologists People educated at Merchant Taylors' School, Northwood People educated at Wilson's School, Wallington People from Ormskirk Philosophers of mathematics Philosophers of mind Philosophers of science Presidents of the British Science Association Presidents of the Royal Astronomical Society Princeton University faculty Recipients of the Gold Medal of the Royal Astronomical Society Royal Medal winners Second Wranglers