**James Jeans** worked on astronomy as well as thermodynamics, heat and other aspects of radiation.

- William Jeans was a parliamentary journalist of Scottish descent who wrote two books on the lives of scientists.
- Jeans was educated in Merchant Taylor's School in London which he entered in 1890.
- Jeans went to Trinity College Cambridge in October 1896 having won a mathematical scholarship.
- Although he would not return again to pure mathematics, Jeans wrote a paper on the theory of numbers while an undergraduate.
- Both Jeans and Hardy were awarded a Smith's prize with 'unspecified relative merit'.
- Jeans was awarded an Isaac Newton Studentship in astronomy and optics, then in 1901 he was elected a Fellow of Trinity.
- Already while he was still an undergraduate Jeans had gained experience in experimental physics having worked in the Cavendish Laboratory during the academic year 1899-1900.
- During this period of forced rest due to the tuberculosis, Jeans worked on his first major text The dynamical theory of gases.
- It was a book which incorporated much of Jeans own researches.
- The dynamical theory of gases is far more than an account of Jeans' own research.
- The book benefits from Jeans' expertise in several areas: his physical intuition, his mathematical skills, and not least his ability to write with extraordinary clarity.
- In 1905 Jeans published a paper in the Philosophical Magazine which showed the impossibility of the ether reaching thermal equilibrium with matter.
- Of course Jeans' paper can be seen as a mathematical "proof" that classical physics does not suffice, but it is interesting to note that his pre-quantum ideas concerning the very long time required for systems to come into equilibrium and the observed breakdown of equipartition in specific heat measurements on molecular gases have been used again in relatively recent times more than 80 years after Jeans introduced them.
- We should also note that Jeans' paper was written after the Michelson-Morley experiment disproved the existence of the ether, and in the same year that Einstein published the special theory of relativity.
- Jeans was appointed a Lecturer in Mathematics at Cambridge in 1904, then he lectured at Princeton from 1905 until 1909 where he was Professor of Applied Mathematics.
- In 1909 Jeans returned to England and the following year he was appointed Stokes Lecturer in Applied Mathematics at Cambridge.
- Certainly Jeans continued to produce a remarkable output, and he wrote an excellent report on Radiation and Quantum Theory for the Physical Society in 1914.
- In 1917 Jeans won the Adams Prize from the University of Cambridge for his essay entitled Problems of cosmogony and stellar dynamics.
- The high work-load was taking its toll, however, and in 1917 Jeans began to show his first signs of heart problems.
- There was a long running scientific argument between Jeans and Eddington over the mechanism by which energy was created in stars.
- Jeans favoured, incorrectly as it turned out, the theory that the energy was the result of contraction while Eddington, correctly of course, believed it resulted from a slow process of annihilation of matter.
- Jeans' work in fluids led him to believe that Laplace's nebular hypothesis for the creation of the solar system was incorrect.
- As we have noted Jeans worked on thermodynamics, heat and other aspects of radiation, publishing major works on these topics and on applications to astronomy.
- In 1928 Jeans was knighted.
- After 1929 Jeans gave up original research and spent most of his time writing popular texts; he wrote nine such texts in all.
- Really despite his work in astronomy and physics, Jeans always thought as a mathematician and always considered himself a mathematician.
- The work examines what Jeans calls the 'mechanical age' from Newton to Einstein the 'new physics' of Planck, Rutherford, and Niels Bohr and 'From appearance to reality' with Bohr, Heisenberg, de Broglie, Schrödinger, and Dirac.
- Although Jeans never published original contributions to quantum theory, he showed in such popular books that he had kept up with the developments in this area.
- However after a second heart attack in September Jeans died in his home.
- The honours which Jeans received are far too numerous to give a full record here.

Born 11 September 1877, Ormskirk, Lancashire, England. Died 16 September 1946, Dorking, Surrey, England.

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Astronomy, Origin England, Physics

**O’Connor, John J; Robertson, Edmund F**: MacTutor History of Mathematics Archive