James Hopwood Jeans

Britannica Concise Encyclopedia: Sir James Hopwood Jeans

(born Sept. 11, 1877, London, Eng. — died Sept. 16, 1946, Dorking, Surrey) British physicist and mathematician. After teaching at Cambridge and Princeton, he worked as a research associate at the Mount Wilson Observatory (1923 – 44). He proposed that matter was continuously created throughout the universe (see steady-state theory). He wrote on a wide variety of phenomena but is perhaps best known as a writer of popular books about astronomy.

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Biography: Sir James Hopwood Jeans

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The English mathematician, physicist, and astronomer Sir James Hopwood Jeans (1877-1946) made important contributions to the development of quantum theory and to theoretical astrophysics, especially to the theory of stellar structure.

On Sept. 11, 1877, James Jeans was born in Ormskirk, Lancashire, the son of a parliamentary journalist. He was brought up in a strict, very religious Victorian home atmosphere. A precocious child, he was reading by age 4 and had a remarkable ability to memorize numbers. At an early age he also became interested in physics, as well as in mechanical devices, especially clocks - the subject of a short book he wrote at age 9.

In 1897 Jeans entered Trinity College, Cambridge, and in 1903 received his master's degree. In 1904 he was appointed university lecturer in mathematics at Cambridge; and in 1906, at the very early age of 28, he was elected a fellow of the Royal Society - all this in spite of the fact that during 1902-1903 tuberculosis of the joints forced him to go to several sanatoriums. During his illness, from which he completely recovered, he wrote his first book, The Dynamical Theory of Gases.

Jeans taught applied mathematics at Princeton University, N.J., from 1905 to 1909. He returned to Cambridge as Stokes lecturer in 1910 but 2 years later relinquished the position and thereafter devoted full time to research and writing.

In 1907 Jeans married Charlotte Tiffany Mitchell; she died in 1934, leaving one daughter. The following year he married Suzanne Hock, a concert organist, with whom Jeans wrote his very popular and informative book Science and Music (1938). They had two sons and a daughter.

In the first period of his scientific life (1901-1914), Jeans's interests were centered mainly on the kinetic theory of gases and the theory of radiation, especially applied to the new quantum theory of Max Planck and others. Through a vigorous interchange of ideas, Lord Rayleigh and Jeans, in 1905, separately derived what later came to be called the Rayleigh-Jeans law. Despite the fact that this law implied a failure of classical theory when applied to blackbody radiation, Jeans, during the ensuing years, repeatedly attempted to sustain classical theory instead of accepting quantum theory. Only after Henri Poincaré's 1912 paper on the quantum theory did Jeans become convinced. Two years later Jeans wrote a brief but comprehensive Report on Radiation and the Quantum Theory, which, after World War I, was extremely influential in convincing physicists of the importance of the new quantum ideas.

During the war years Jeans experienced his finest hour as a scientist - now a theoretical astrophysicist. His researches on stellar structure were most significant, especially his proof that a rotating incompressible mass will, with increasing rotational velocity, first become pearshaped and then cataclysmically fission into two parts (one model for a single star evolving into a double-star system). This and other important results, including a tidal encounter nebular hypothesis that replaced the classical Kant-Laplace nebular hypothesis, were published in his 1919 Adams Prize essay, Problems of Cosmogony and Stellar Dynamics.

The next decade of Jeans's life (1918-1928) was marked by a rather sharp decrease in his reputation as a theoretical astrophysicist. Already, in 1917, he had a famous debate with Arthur S. Eddington on stellar structure and, though not really apparent at the time, Jeans by and large emerged the loser. In 1929 Jeans turned to popular science writing, especially in astronomy, and soon became very successful. His Universe around Us ushered in a series of eight books between 1929 and 1942. All are stimulating expositions, though they suffer in one degree or another from presenting the results of scientific research a bit too dogmatically, thereby giving a distorted picture of such research in progress.

Jeans was awarded numerous honorary degrees and professional offices. He was knighted in 1928 and won the coveted Order of Merit in 1939. He was a modest and unassuming man and a devoted father. Jeans died on Sept. 16, 1946, at his home in Dorking, Surrey.

James Hopwood Jeans
Born	11 September 1877(1877-09-11) Ormskirk, Lancashire, England
Died	16 September 1946 (aged 69) Dorking, Surrey, England
Nationality	England
Fields	astronomy
Institutions	Princeton University
Known for	Rayleigh-Jeans law

Background

Educated at Merchant Taylors' School, Northwood, Wilson's Grammar School,^[3] Camberwell and Trinity College, Cambridge,^[4] he finished Second Wrangler in the university in the Mathematical Tripos of 1898. He taught at Cambridge, but went to Princeton University 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 and stellar evolution. His analysis of rotating bodies led him to conclude that 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 with Arthur Eddington, is a founder of British cosmology. In 1928 Jeans was the first to conjecture a steady state cosmology based on a hypothesized continuous creation of matter in the universe.^[5] This theory was ruled out when the 1965 discovery of the cosmic microwave background was widely interpreted as the tell-tale signature of the Big Bang.

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, Through Space and Time (1934), The New Background of Science (1933), and The Mysterious Universe. These books made Jeans fairly well known as an expositor of the revolutionary scientific discoveries of his day, especially in relativity and physical cosmology.

He also wrote the book "Physics and Philosophy" (1943) where he explores the different views on reality from two different perspectives: science and philosophy.

He married twice, first the American poet Charlotte Mitchell in 1907, then the Austrian organist and harpsichordist Suzanne Hock (better known as Susi Jeans) in 1935.

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 but notably in Mathematics and Sciences.

Major accomplishments

One of Jeans' major discoveries, named Jeans length, is a critical radius of an interstellar cloud 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.

$\lambda_J=\sqrt{\frac{15k_{B}T}{4\pi Gm\rho}}$

Jeans came up with another version of this equation, called Jeans mass or Jeans instability, 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 blackbody radiation to the temperature of the emission source.

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

Books

Available online from the Internet Archive:

1904. The Dynamical Theory of Gases
1906. Theoretical Mechanics
1908. Mathematical Theory of Electricity and Magnetism

Other:

1929. The Universe Around Us
1930. The Mysterious Universe
1931. The Stars in Their Courses
1933. The New Background of Science
1937. Science and Music
1942. Physics and Philosophy

Awards and honours

Gold Medal of the Royal Astronomical Society in 1922.
He was knighted in 1928.
Member of the Order of Merit
The crater Jeans on the Moon is named after him, as is the crater Jeans on Mars.
President of the 25th session of the Indian Science Congress in 1938.
The String Quartet No.7 by Robert Simpson was written in tribute to him on the centenary of his birth, 1977.

References

^ Sir James Jeans 1938 (reprint of 1931's edition of 1930 book): The Mysterious Universe.
^ GRO Register of Deaths: SEP 1946 5g 607 SURREY SE - James H. Jeans, aged 69
^ Allport, D.H. & Friskney, N.J. "A Short History of Wilson's School", Wilson's School Charitable Trust, 1987, pg 234
^ Jeans, James Hopwood in Venn, J. & J. A., Alumni Cantabrigienses, Cambridge University Press, 10 vols, 1922–1958.
^ Astronomy and Cosmogony, Cambridge U Press, p 360

Jeans, James Hopwood. (1947). The Growth of Physical Science. Cambridge University Press (reissued by Cambridge University Press, 2009; ISBN 9781108005654)
Jeans, James Hopwood. (1942). Physics and Philosophy. Cambridge University Press (reissued by Cambridge University Press, 2009; ISBN 9781108005678)
Jeans, James Hopwood. (1940). An Introduction to the Kinetic Theory of Gases. Cambridge University Press (reissued by Cambridge University Press, 2009; ISBN 9781108005609)
Jeans, James Hopwood. (1937). Science and Music. Cambridge University Press (reissued by Cambridge University Press, 2009; ISBN 9781108005692)
Jeans, James Hopwood. (1934). Through Space and Time. Cambridge University Press (reissued by Cambridge University Press, 2009; ISBN 9781108005715)
Jeans, James Hopwood. (1933). The New Background of Science. Cambridge University Press (reissued by Cambridge University Press, 2009; ISBN 9781108005722)
Jeans, James Hopwood. (1931). Stars in Their Courses. Cambridge University Press (reissued by Cambridge University Press, 2009; ISBN 9781108005708)
Jeans, James Hopwood. (1930). The Mysterious Universe. Cambridge University Press (reissued by Cambridge University Press, 2009; ISBN 9781108005661)
Jeans, James Hopwood. (1928). Astronomy and Cosmogony. Cambridge University Press (reissued by Cambridge University Press, 2009; ISBN 9781108005623)
Jeans, James Hopwood. (1925). Mathematical Theory of Electricity and Magnetism. Cambridge University Press (reissued by Cambridge University Press, 2009; ISBN 9781108005616)
Jeans, James Hopwood. (1926). Atomicity and Quanta. Cambridge University Press (reissued by Cambridge University Press, 2009; ISBN 9781108005630)
Jeans, James Hopwood. (1919). Problems of Cosmology and Stellar Dynamics. Cambridge University Press (reissued by Cambridge University Press, 2009; ISBN 9781108005685)
Jeans, James Hopwood. (1904). The Dynamical Theory of Gases. Cambridge University Press (reissued by Cambridge University Press, 2009; ISBN 9781108005647)

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