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James Jeans
Times obituary
A BRILLIANT EXPOSITOR OF SCIENCE
The death of Sir James Jeans, O.M., at his home at Dorking yesterday, deprives science of a man whose mathematical investigations of problems in cosmogony, radiation, and molecular dynamics were penetrating and original, while his lucid exposition of the newer physics and astronomy charmed hundreds of thousands of readers in many lands.
James Hopwood Jeans was born at Southport on September 11, 1877. His father, William Tullock Jeans, who lived at Tulse Hill, London, was a parliamentary journalist. Jeans went to Merchant Taylors' School from 1890 to 1896; at first he took the classical side, but soon found the mathematical side suited him better. He also developed an interest in experimental chemistry and had a boy's ambition to be an engineer. Such interests were unusual in a Taylorian, but when he became a scholar at Trinity College, Cambridge, in 1896 they found full room for development. He was bracketed second Wrangler in 1898 with J. F. Cameron, later Master of Caius, both being beaten by R. W. H. T. Hudson, who was elected a Fellow of St. John's College. Jeans took a First Class in Part II of the Mathematical Tripos in 1900 and was elected Isaac Newton Student at the University. The following year saw him Second Smith's Prizeman to G. H. Hardy, who had been one place below him in the list of Wranglers, and he was elected a Fellow of Trinity. He became a University Lecturer in Mathematics in 1904.
From 1905 to 1909 he was out of the country as Professor of Applied Mathematics at Princeton University, United States, but in 1910 was recalled to Cambridge as Stokes Lecturer in Mathematics He obtained the Adams Prize in 1917 for a brilliant essay published as "Problems of Cosmogony and Stellar Dynamics." In 1919 he became Secretary of the Royal Society, a Fellowship he had been elected to in 1906. He retired in 1929 and from his home at Dorking gave popular expositions of science and of what seemed to him its philosophical significance, which made his name famous around the world.
One of Jeans's first scientific undertakings was to confirm Lord Rayleigh's law governing the distribution of energy radiated from a black body at different wavelengths. At the same time, Planck had convinced himself of the soundness of Rayleigh's proof and had become suspicious of the classical premises on which it was based. The result was Quantum Theory. In the dynamical theory of gases, Jeans gave a proof of the law of equipartition of energy and the first satisfactory proof of Maxwell's law governing the distribution of velocities among molecules. The law was communicated by Maxwell to the British Association as far back as 1859, but Maxwell's original proof, as well as one devised later, introduced illicit assumptions. Jeans's proof, based on general dynamical considerations, was given in 1903. His studies in this subject were gathered together in 1904 into "The Dynamical Theory of Gases." While at Princeton, Jeans published his "Elementary Treatise on Theoretical Mechanics" in 1906 and his "Mathematical Theory of Electricity and Magnetism" in 1908, a widely used textbook. Its successive editions are an indication of the growth of quantum theory, the significance of which Jeans was one of the first people in this country to grasp. At a time when it was still greatly suspected, his report in 1914 to the Physical Society entitled "Radiation and the Quantum Theory" won many adherents.
Jeans's most original work, however, was in the field of cosmogony, to which he devoted two treatises, his Adams Essay, published in 1919, and "Astronomy and Cosmogony," published in 1928. He mathematically examined the stability of rotating masses of liquid, notably pear-shaped figures, including both incompressible and compressible fluids, and later gave a complete account of stellar evolution. He showed how gravitational instability in a chaotic mass of gas would give rise to the spiral nebulae, and how the same cause would lead to the formation of stars in the outer regions of the spiral nebulae, such as have since been observed. He further showed that the normal effect of increasing rapidity of rotation, due to shrinking age, would be for a star to break up into two forming a binary system. But his most notable achievement was his explanation, following Chamberlin and Moulton, of planets and their satellites as being due to tidal forces raised in a star by the close passage of another star. Such a close passage would draw out gaseous arms which might break off and condense into bodies having the relative size of the sun! planets. Tides raised in the planet were similarly invoked to explain the origin of the satellites. Our own moon remains anomalous and may require an actual collision of a star with our sun, but the thoroughness of Jeans's mathematical investigations gave the coup de grâce to the nebular hypothesis of Kant and Laplace. That hypothesis had been greatly modified, but its central principle, that the origin of planets was to be sought in the increasing rotation of the parent body, had remained intact until Chamberlin and Moulton's planetisimal hypothesis. Incidentally, Jeans' theory showed that planetary systems must be very rare.
Jeans contributed a fertile idea to the discussion of the source of stellar radiation. As early as 1904 he had suggested that radioactivity might be explained by the combination and mutual annihilation of two ether strains of opposite kinds, that is, in the coalescence of a positive and negative ion, which would result in the disappearance of a certain amount of mass." The novel hypothesis proved unnecessary in the field of radioactivity, but in 1918 he calculated the amount of radiation which would be set free by the diminution of the sun's mass by 1 percent, showing that the sun would have an extra radiative life of 150,000,000,000 years. In 1928 he amplified this suggestion for the source of stellar energy. Although highly conjectural, it is widely accepted because no other theory gives the stars an adequate life. Jeans also saw the annihilation of matter as the source of cosmic radiation. He took part in developing the theory of the radiative equilibrium of stars and the theory that stellar atoms might be stripped wholly or partly of their electrons. He believed that in the stars there were radioactive atoms of atomic numbers higher than any known on earth.
No account of Jeans's life would be complete without mention of his popular books. Their phenomenal sales were equalled only by a few imaginative or religious works. Jeans's literary success might have been predicted from his treatises, where the non-mathematical sections can be enjoyed even by the layman. As expositions of science, these popular books are unexcelled. But they also include Jeans's philosophical deductions from modern science, which are contentious. He emphasized the part played by mathematics in science to a degree hardly equalled since Pythagoras. Because the laws of astronomy were mathematical laws, it seemed to him that God must be thought of as a pure mathematician, which was merely a modern form of anthropomorphism. He elevated the Second Law of Thermodynamics to a position of supreme importance, and so held that the universe was running down to a dead level of energy; many of his colleagues felt unable to be so dogmatic. The fact that the most important physical laws are today expressed in statistical fashion led him to decry causal laws and to announce a general indeterminism in nature; here he had the two most eminent physicists of the day, as well as many of their colleagues, against him. Finally, Jeans tended towards a form of idealism in which matter was derived from consciousness; this belief might be legitimate enough in itself, but was not a valid deduction from current science. These opinions could be, and were, easily criticized. But it should not be forgotten how infinitely preferable they were to the barren skepticism into which so many men of science had sunk, and how great a part Jeans played in rescuing science from that morass.
Jeans lectured on many foundations. From 1925 to 1927 he was president of the Royal Astronomical Society. He was knighted in 1928 and was awarded the Order of Merit in 1939. In 1934 he presided over the British Association, and his exposition of his philo- sophy at the Aberdeen meeting roused much attention. He was an honorary Fellow of the Institute of Physics and was given honorary doctorates by the Universities of Oxford, Manchester chester, Aberdeen, St. Andrews, Dublin, and Johns Hopkins. In 1923 he was made a Research Associate of Mount Wilson Observa- tory, California.
Jeans married in 1907 Charlotte Tiffany, daughter of Alfred Mitchell, of New London, Connecticut. She died in 1934, leaving one daughter. In 1935 he married Susi, daughter of Oskar Hock, of Vienna, by whom he had two sons and a daughter.
A BRILLIANT EXPOSITOR OF SCIENCE
The death of Sir James Jeans, O.M., at his home at Dorking yesterday, deprives science of a man whose mathematical investigations of problems in cosmogony, radiation, and molecular dynamics were penetrating and original, while his lucid exposition of the newer physics and astronomy charmed hundreds of thousands of readers in many lands.
James Hopwood Jeans was born at Southport on September 11, 1877. His father, William Tullock Jeans, who lived at Tulse Hill, London, was a parliamentary journalist. Jeans went to Merchant Taylors' School from 1890 to 1896; at first he took the classical side, but soon found the mathematical side suited him better. He also developed an interest in experimental chemistry and had a boy's ambition to be an engineer. Such interests were unusual in a Taylorian, but when he became a scholar at Trinity College, Cambridge, in 1896 they found full room for development. He was bracketed second Wrangler in 1898 with J. F. Cameron, later Master of Caius, both being beaten by R. W. H. T. Hudson, who was elected a Fellow of St. John's College. Jeans took a First Class in Part II of the Mathematical Tripos in 1900 and was elected Isaac Newton Student at the University. The following year saw him Second Smith's Prizeman to G. H. Hardy, who had been one place below him in the list of Wranglers, and he was elected a Fellow of Trinity. He became a University Lecturer in Mathematics in 1904.
From 1905 to 1909 he was out of the country as Professor of Applied Mathematics at Princeton University, United States, but in 1910 was recalled to Cambridge as Stokes Lecturer in Mathematics He obtained the Adams Prize in 1917 for a brilliant essay published as "Problems of Cosmogony and Stellar Dynamics." In 1919 he became Secretary of the Royal Society, a Fellowship he had been elected to in 1906. He retired in 1929 and from his home at Dorking gave popular expositions of science and of what seemed to him its philosophical significance, which made his name famous around the world.
One of Jeans's first scientific undertakings was to confirm Lord Rayleigh's law governing the distribution of energy radiated from a black body at different wavelengths. At the same time, Planck had convinced himself of the soundness of Rayleigh's proof and had become suspicious of the classical premises on which it was based. The result was Quantum Theory. In the dynamical theory of gases, Jeans gave a proof of the law of equipartition of energy and the first satisfactory proof of Maxwell's law governing the distribution of velocities among molecules. The law was communicated by Maxwell to the British Association as far back as 1859, but Maxwell's original proof, as well as one devised later, introduced illicit assumptions. Jeans's proof, based on general dynamical considerations, was given in 1903. His studies in this subject were gathered together in 1904 into "The Dynamical Theory of Gases." While at Princeton, Jeans published his "Elementary Treatise on Theoretical Mechanics" in 1906 and his "Mathematical Theory of Electricity and Magnetism" in 1908, a widely used textbook. Its successive editions are an indication of the growth of quantum theory, the significance of which Jeans was one of the first people in this country to grasp. At a time when it was still greatly suspected, his report in 1914 to the Physical Society entitled "Radiation and the Quantum Theory" won many adherents.
Jeans's most original work, however, was in the field of cosmogony, to which he devoted two treatises, his Adams Essay, published in 1919, and "Astronomy and Cosmogony," published in 1928. He mathematically examined the stability of rotating masses of liquid, notably pear-shaped figures, including both incompressible and compressible fluids, and later gave a complete account of stellar evolution. He showed how gravitational instability in a chaotic mass of gas would give rise to the spiral nebulae, and how the same cause would lead to the formation of stars in the outer regions of the spiral nebulae, such as have since been observed. He further showed that the normal effect of increasing rapidity of rotation, due to shrinking age, would be for a star to break up into two forming a binary system. But his most notable achievement was his explanation, following Chamberlin and Moulton, of planets and their satellites as being due to tidal forces raised in a star by the close passage of another star. Such a close passage would draw out gaseous arms which might break off and condense into bodies having the relative size of the sun! planets. Tides raised in the planet were similarly invoked to explain the origin of the satellites. Our own moon remains anomalous and may require an actual collision of a star with our sun, but the thoroughness of Jeans's mathematical investigations gave the coup de grâce to the nebular hypothesis of Kant and Laplace. That hypothesis had been greatly modified, but its central principle, that the origin of planets was to be sought in the increasing rotation of the parent body, had remained intact until Chamberlin and Moulton's planetisimal hypothesis. Incidentally, Jeans' theory showed that planetary systems must be very rare.
Jeans contributed a fertile idea to the discussion of the source of stellar radiation. As early as 1904 he had suggested that radioactivity might be explained by the combination and mutual annihilation of two ether strains of opposite kinds, that is, in the coalescence of a positive and negative ion, which would result in the disappearance of a certain amount of mass." The novel hypothesis proved unnecessary in the field of radioactivity, but in 1918 he calculated the amount of radiation which would be set free by the diminution of the sun's mass by 1 percent, showing that the sun would have an extra radiative life of 150,000,000,000 years. In 1928 he amplified this suggestion for the source of stellar energy. Although highly conjectural, it is widely accepted because no other theory gives the stars an adequate life. Jeans also saw the annihilation of matter as the source of cosmic radiation. He took part in developing the theory of the radiative equilibrium of stars and the theory that stellar atoms might be stripped wholly or partly of their electrons. He believed that in the stars there were radioactive atoms of atomic numbers higher than any known on earth.
No account of Jeans's life would be complete without mention of his popular books. Their phenomenal sales were equalled only by a few imaginative or religious works. Jeans's literary success might have been predicted from his treatises, where the non-mathematical sections can be enjoyed even by the layman. As expositions of science, these popular books are unexcelled. But they also include Jeans's philosophical deductions from modern science, which are contentious. He emphasized the part played by mathematics in science to a degree hardly equalled since Pythagoras. Because the laws of astronomy were mathematical laws, it seemed to him that God must be thought of as a pure mathematician, which was merely a modern form of anthropomorphism. He elevated the Second Law of Thermodynamics to a position of supreme importance, and so held that the universe was running down to a dead level of energy; many of his colleagues felt unable to be so dogmatic. The fact that the most important physical laws are today expressed in statistical fashion led him to decry causal laws and to announce a general indeterminism in nature; here he had the two most eminent physicists of the day, as well as many of their colleagues, against him. Finally, Jeans tended towards a form of idealism in which matter was derived from consciousness; this belief might be legitimate enough in itself, but was not a valid deduction from current science. These opinions could be, and were, easily criticized. But it should not be forgotten how infinitely preferable they were to the barren skepticism into which so many men of science had sunk, and how great a part Jeans played in rescuing science from that morass.
Jeans lectured on many foundations. From 1925 to 1927 he was president of the Royal Astronomical Society. He was knighted in 1928 and was awarded the Order of Merit in 1939. In 1934 he presided over the British Association, and his exposition of his philo- sophy at the Aberdeen meeting roused much attention. He was an honorary Fellow of the Institute of Physics and was given honorary doctorates by the Universities of Oxford, Manchester chester, Aberdeen, St. Andrews, Dublin, and Johns Hopkins. In 1923 he was made a Research Associate of Mount Wilson Observa- tory, California.
Jeans married in 1907 Charlotte Tiffany, daughter of Alfred Mitchell, of New London, Connecticut. She died in 1934, leaving one daughter. In 1935 he married Susi, daughter of Oskar Hock, of Vienna, by whom he had two sons and a daughter.
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