James Hopwood Jeans
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Sir James Hopwood Jeans (September 11, 1877 in Ormskirk, Lancashire – September 16, 1946 in Dorking, Surrey) was a British physicist, astronomer, and mathematician.
Educated at Merchant Taylors' School, Northwood and Trinity College, Cambridge, he finished second 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 excellence in cosmology, a fact which persists down to the present day. Jeans was the first to propose a steady state cosmology based on a hypothesized continuous creation of matter in the universe. 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.
[edit] Major accomplishments
One of Jean's 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.
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.
[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).
Regarding reverse time travel: "One must stand stiller than still." (Through Space and Time).
[edit] Works
- The Dynamical Theory of Gases (1904)
- Theoretical Mechanics (1906)
- Mathematical Theory of Electricity and Magnetism (1908)
- The Stars in Their Courses (1931)
- The Universe Around Us, Through Space and Time (1934)
- The New Background of Science (1933)
- The Mysterious Universe
[edit] Awards and honours
- Gold Medal of the Royal Astronomical Society in 1922.
- He was knighted in 1928.
- Jeans crater on the Moon is named after him, as is Jeans crater 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.
[edit] See also
[edit] References
[edit] External links
- MacTutor (St. Andrews Univ.): More biographical information.
