James Jeans

Sir James Jeans OMFRS
Born	James Hopwood Jeans (1877-09-11)11 September 1877 Ormskirk,Lancashire,England
Died	16 September 1946(1946-09-16)(aged 69) Dorking,Surrey,England
Alma mater	Merchant Taylors' School;Cambridge University
Known for	Jeans equations Jeans escape Jeans instability Jeans mass Jeans length Jeans's theorem Rayleigh–Jeans law Method of image charges Tidal hypothesis
Awards	Smith's Prize(1901) Adams Prize(1917) Royal Medal(1919)
Scientific career
Fields	Astronomy, mathematics, physics
Institutions	Trinity College, Cambridge;Princeton University
Notable students	Ronald Fisher

Sir James Hopwood JeansOMFRS(11 September 1877 – 16 September 1946) was an Englishphysicist,astronomerandmathematician.

Early life

Born inOrmskirk,Lancashire,the son ofWilliam Tulloch Jeans,a parliamentary correspondent and author. Jeans was educated atMerchant Taylors' School,Wilson's Grammar School,CamberwellandTrinity College, Cambridge. As a gifted student, Jeans was counselled to take an aggressive approach to theCambridge Mathematical Triposcompetition:

Early in theMichaelmas termof 1896,Walkersent for Jeans andHardyand advised them to take Part I of the Mathematical Tripos in two years. He told them that he could not guarantee that they would come out higher than fifteenth in the list ofwranglers,but he understood that they would never regret it. They accepted his advice, and went toR. R. Webb,the most famous private coach of the period... At the end of his first year, [Jeans] told Walker that he had quarrelled with Webb, his coach. Walker accordingly took Jeans himself, and the result was a triumph:... Jeans was bracketed second wrangler withJ. F. Cameron... [and]R.W.H.T. HudsonwasSenior WranglerandG. H. Hardyfourth wrangler.

Career

Jeans was electedFellowof Trinity College in October 1901,and taught at Cambridge, but went toPrinceton Universityin 1904 as a professor of applied mathematics. He returned to Cambridge in 1910.

He made important contributions in many areas of physics, includingquantum theory,the theory ofradiationandstellar evolution.His analysis of rotating bodies led him to conclude thatPierre-Simon Laplace'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 withArthur Eddington,is a founder of Britishcosmology.In 1928, Jeans was the first to conjecture asteady state cosmologybased on a hypothesized continuous creation of matter in the universe.In his bookAstronomy and Cosmogony(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 thecosmic microwave backgroundwas widely interpreted as the tell-tale signature of theBig Bang.

His scientific reputation is grounded in the monographsThe Dynamical Theory of Gases(1904),Theoretical Mechanics(1906), andMathematical Theory of Electricity and Magnetism(1908). After retiring in 1929, he wrote a number of books for the lay public, includingThe Stars in Their Courses(1931),The Universe Around Us,Through Space and Time(1934),The New Background of Science(1933), andThe Mysterious Universe.These books made Jeans fairly well known as an expositor of the revolutionary scientific discoveries of his day, especially inrelativityandphysical cosmology.

In 1939, theJournal of the British Astronomical Associationreported that Jeans was going to stand as a candidate for parliament for theCambridge 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 bookPhysics 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 agnosticFreemason.

Personal life

Jeans married twice, first to the American poet Charlotte Tiffany Mitchell in 1907, who died,and then to the AustrianorganistandharpsichordistSuzanne Hock (better known asSusi Jeans) in 1935. Susi and Jeans had three children: George, Christopher, and Catherine.As a birthday present for his wife, he wrote the bookScience and Music.

Death

Jeans died in 1947 with the presence of his wife andJoy Adamson,who suggested to the widow to create adeath maskof Jeans. It is now held by theRoyal Society.

Major accomplishments

One of Jeans' major discoveries, namedJeans length,is a critical radius of aninterstellar cloudin 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.

$\lambda _{\rm {J}}={\sqrt {\frac {15k_{\rm {B}}T}{4\pi Gm\rho }}}$

Jeans came up with another version of this equation, called Jeans mass orJeans instability,that solves for the critical mass a cloud must attain before being able to collapse.

Jeans also helped to discover theRayleigh–Jeans law,which relates the energy density ofblack-body radiationto the temperature of the emission source.

$f(\lambda )=8\pi c{\frac {k_{\rm {B}}T}{\lambda ^{4}}}$

Jeans is also credited with calculating the rate ofatmospheric escapefrom a planet due to kinetic energy of the gas molecules, a process known asJeans escape.

Idealism

Jeans espoused a philosophy of science rooted in the metaphysical doctrine ofidealismand opposed tomaterialismin his speaking engagements and books. His popular science publications first advanced these ideas in 1929'sThe Universe Around Uswhen he likened "discussing the creation of the universe in terms of time and space," to, "trying to discover the artist and the action of painting, by going to the edge of the canvas." But he turned to this idea as the primary subject of his best-selling1930 book,The Mysterious Universe,where he asserted that a picture of the universe as a "non-mechanical reality" was emerging from the science of the day.

The Universe begins to look more like a great thought than like a great machine. Mind no longer appears to be an accidental intruder into the realm of matter... we ought rather hail it as the creator and governor of the realm of matter.

— James Jeans,The Mysterious Universe,

In a 1931 interview published inThe Observer,Jeans was asked if he believed that life was an accident or if it was, "part of some great scheme." He said that he favored, "the idealistic theory that consciousness is fundamental, and that the material universe is derivative from consciousness," going on to suggest that, "each individual consciousness ought to be compared to a brain-cell in auniversal mind."

In his 1934 address to the British Association for the Advancement of Science meeting in Aberdeen as the Association's president, Jeans spoke specifically to the work ofDescartesand its relevance to the modern philosophy of science. He argued that, "There is no longer room for the kind ofdualismwhich has haunted philosophy since the days of Descartes. "

When Daniel Helsing reviewedThe Mysterious Universefor Physics Today in 2020, he summarized the philosophical conclusions of the book, "Jeans argues that we must give up science’s long-cherished materialistic and mechanical worldview, which posits that nature operates like a machine and consists solely of material particles interacting with each other." His evaluation of Jeans contrasted these philosophical views with modern science communicators such asNeil deGrasse TysonandSean Carrollwho he suggested, "would likely take issue with Jeans’s idealism."

Awards and honours

• Fellow of the Royal Societyin May 1906
• Bakerian LecturetoRoyal Societyin 1917.
• Royal Medalof theRoyal Societyin 1919.
• Hopkins Prizeof theCambridge Philosophical Society1921–1924.
• Gold Medal of the Royal Astronomical Societyin 1922.
• He wasknightedin 1928.
• Franklin Medalof theFranklin Institutein 1931.
• In 1933 Jeans was invited to deliver theRoyal Institution Christmas LectureonThrough Space and Time.
• Mukerjee Medal of theIndian Association for the Cultivation of Sciencein 1937.
• President of the 25th session of theIndian Science Congressin 1938.
• Calcutta Medal of theIndian Science Congress Associationin 1938.
• Lorimer Medal of theAstronomical Society of Edinburghin 1938for which he gave the Lorimer Lecture:The Depths of Space.
• Member of theOrder of Meritin 1939.
• The craterJeanson the Moon is named after him, as is the craterJeanson Mars.
• The String Quartet No.7 byRobert Simpsonwas written in tribute to him on the centenary of his birth, 1977.

Bibliography

The Astronmical Horizonhttps://www.amazon.co.uk/dp/B000NIS57O?ref=myi_title_dp-The Philip Maurice Deneke Lecture 1944 - Published Oxford University Press 1945

• The Growth of Physical Science.Cambridge University Press. 2009 [1947].ISBN978-1-108-00565-4.
• Physics and Philosophy.Courier Corporation. 1981 [1942].ISBN978-0-486-24117-3.
• An Introduction to the Kinetic Theory of Gases.CUP Archive. 1982 [1940].ISBN978-0-521-09232-6.
• Science and Music.Cambridge University Press. 1937.
• Through Space and Time.Cambridge University Press. 2009 [1934].ISBN978-1-108-00571-5.
• The New Background of Science.CUP Archive. 1953 [1933]. GGKEY:HCUUR8F8EL0.
• Stars in Their Courses.Cambridge University Press. 2009 [1931].ISBN978-1-108-00570-8.
• The Mysterious Universe.CUP Archive. 1944 [1930]. GGKEY:LXRDCH5GSZR.
• Astronomy and Cosmogony.Cambridge University Press. 2009 [1928].ISBN978-0-521-74470-6.
• Mathematical Theory of Electricity and Magnetism.Cambridge University Press. 2009 [1925].ISBN978-1-108-00561-6.
• Atomicity and Quanta.Cambridge University Press. 2009 [1926].ISBN978-1-108-00563-0.
• Problems of Cosmology and Stellar Dynamics.Cambridge University Press. 2009 [1919].ISBN978-1-108-00568-5.
• The Dynamical Theory of Gases.CUP Archive. 1925 [1904]. GGKEY:6UDJTT06BSL.
• The Universe Around Us.Macmillan. 1929.
• The Depths of Space, The Lorimer Lecture(PDF).Astronomical Society of Edinburgh. 1938. p. 15.Retrieved12 January2022.

Sources

• Allport, Denison Howard; Friskney, Norman J (1987).A Short History of Wilson's School.Wilson's School Charitable Trust.
• Bell, E.T. (1986).Men of Mathematics.Simon and Schuster.ISBN978-0-671-62818-5.The Great Architect of The Universe now begins to appear as a pure mathemetician(quoting Jeans, The Mysterious Universe, p. 134).
• Teilhard De Chardin, Pierre(2004).The Future of Man.Image Books/Doubleday.ISBN978-0-385-51072-1.We can hardly wonder, in the circumstances, that agnostics such as Sir James Jeans and Marcel Boll, and even convinced believers like Guardini, have uttered expressions ol amazement (tinged with heroic pessimism or triumphant detachment) at the apparent insignificance of the phenomenon of Life in terms of the cosmos— a little mold on a grain of dust...
• Milne, E. A.(2013) [1952].Sir James Jeans: A Biography.Cambridge University Press.ISBN978-1-107-62333-0.

External links

• Works by James JeansatFaded Page(Canada)
• Britannica articleincludes photo
• Portraits of James Jeansat theNational Portrait Gallery, London

Works of Jeans available online from theInternet Archive

• 1904.The Dynamical Theory of Gases
• 1906.Theoretical Mechanics
• 1908.Mathematical Theory of Electricity and Magnetism
• 1947.The Growth of Physical Science