James Hopwood Jeans

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James Hopwood Jeans
giving the 1933Royal Institution Christmas Lectures
Born September 11, 1877(1877-09-11)
Ormskirk, Lancashire, England
Died September 16, 1946 (aged 69)
Dorking, Surrey, England
Nationality England
Fields astronomy
Institutions Princeton University

Sir James Hopwood Jeans OM FRS MA DSc ScD LLD[1] (September 11, 1877 in Ormskirk, Lancashire – September 16, 1946 in Dorking, Surrey [2]) was an English physicist, astronomer and mathematician.

Educated at Merchant Taylors' School, Northwood, Wilson's Grammar School,[3] Camberwell and Trinity College, Cambridge, 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. Jeans was the first to propose a steady state cosmology based on a hypothesized continuous creation of matter in the universe.[citation needed] 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.

Contents

[edit] 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}

[edit] Quotes

"The stream of knowledge is heading towards a non-mechanical reality; the universe begins to look more like a great thought than like a 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."

"Life exists in the universe only because the carbon atom possesses certain exceptional properties." (The Mysterious Universe, in page 19 of the Pelican Books 1938 reprint of the Second Edition of 1931 which was preceded by the 1930 first edition).

Regarding reverse time travel: "One must stand stiller than still." (Through Space and Time).

"Everything that has been said, and every conclusion that has been tentatively put forward, is quite frankly speculative and uncertain. We have tried to discuss whether present-day science has anything to say on certain difficult questions, which are perhaps set for ever beyond the reach of human understanding. We cannot claim to have discerned more than a very faint glimmer of light at the best; perhaps it was wholly illusory, for certainly we had to strain our eyes very hard to see anything at all. So that our main contention can hardly be that the science of to-day has a pronouncement to make, perhaps it ought rather to be that science should leave off making pronouncements: the river of knowledge has too often turned back on itself." (the closing sentences in page 188 of The Mysterious Universe, 1938 Pelican Books reprint of 1931 Second Edition, which was after the First Edition of 1930)

[edit] Works

[edit] Awards and honours

[edit] See also

[edit] References

  1. ^ Sir James Jeans 1938 (reprint of 1931's edition of 1930 book): The Mysterious Universe.
  2. ^ GRO Register of Deaths: SEP 1946 5g 607 SURREY SE - James H. Jeans, aged 69
  3. ^ Allport, D.H. & Friskney, N.J. "A Short History of Wilson's School", Wilson's School Charitable Trust, 1987, pg 234

[edit] External links

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