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Arthur Eddington
Times obituary
CAMBRIDGE PROFESSOR OF ASTRONOMY
Sir Arthur Stanley Eddington, O.M., D.Sc., F.R.S., Plumian Professor of Astronomy at Cambridge University, died at Cambridge yesterday. He was a gifted astronomer whose original theories and powers of mathematical analysis took his science a long way forward; he was a brilliant expositor of physics and astronomy, able to communicate the most difficult conceptions in the simplest and most fascinating language; and he was an able interpreter to philosophers of the significance of the latest scientific discoveries.
Born on December 28, 1882, at Kendal, Westmorland, he was the son of Arthur H. Eddington, headmaster of the Friends' School in Kendal, where, towards the end of the eighteenth century, John Dalton, founder of the atomic theory, had been assistant master and later joint manager Eddington was educated at Bryn Melyn, Weston-super-Mare, and at Owens College, Manchester, where he won all the honours it had to offer, culminating in first place in the brilliant physics class list of 1902. His literary gifts were also marked, his proficiency in Greek indicating that, had he so chosen, he could have made his mark in the humanities no less than in science. Next, he went to Trinity College, Cambridge, where he became a scholar and, in 1904, was Senior Wrangler. The next year, he obtained a First Class in Part II of the Mathematical Tripos. He took the B.Sc. degree from London University, obtaining a scholarship for physics in the final honour examination. He was Smiths Prizeman at Cambridge in 1907 and, in the same year, was elected to a Fellowship at Trinity.
Eddington's astronomical work was done in two places admirably suited to combining practice with theory. From 1906 to 1913, he was chief assistant at the Royal Observatory, Greenwich, and there laid a sound observational foundation for his future work. In 1913 he was elected Plumian Professor of Astronomy at Cambridge, and the directorship of the University Observatory fell to him the next year. His original work was along four main lines: the investigation of stellar systems, a study of the internal constitution of the stars, an extension of the theory of relativity, and a linking of atomic structure with cosmogony. The thoroughness of his groundwork is shown by a paper in 1910 in which he analyzed the 6,188 stars of Professor Boss's preliminary general catalogue. As a result of his studies of the proper motions of the so-called fixed stars, he postulated (following Kapteyn) that the stars did not move indiscriminately but tended to follow two favoured directions, forming two "star streams. "
In 1916 Eddington began studying the radiative equilibrium of stars. He developed the hypothesis that the equilibrium of a star is the result of a balance between the inward forces of gravitation and the outward pressure of radiation from the star's central regions. The outer matter of the star tends to fall towards the centre under its own weight, but radiation from the centre preserves equilibrium. This balancing of forces also permitted an explanation of the fact that the masses of the various stars are not greatly dissimilar but are mostly of the order of a thousand quadrillion tons. It involved the conclusion that large stars were tenuous and small stars dense.
One of Eddington's most brilliant discoveries was a correlation between the mass and luminosity of stars, which he announced in 1924. This showed not only that the absolute luminosity of a star increased with its mass, but that the luminosity per unit mass also increased. The law, a remarkable combination of theory and observation, gave astronomers a means of calculating the masses of the thousands of stars whose luminosities could be accurately measured. Eddington extended his work in this direction to cover the Cepheid variables, stars like Cephei which pulsate in a definite period. It was found that Cepheid variables of the same period in different parts of the universe were closely similar, and so Eddington graphically described them as "standard candles."
In 1917 Eddington received from de Sitter a copy of Einstein's famous paper on the theory of relativity, and at that time it was probably the only copy in England. He was immediately won to the theory, and his "report" to the Physical Society in 1918 made many more converts. His brilliant exposition led Einstein to commend him as the best interpreter of the theory. But he did more than expound; he confirmed the theory by observation and extended it mathematically. His particular contribution to relativity was a generalization of Weyl's theory by which electromagnetic phenomena had been included with gravitation in the geometry of the world. Einstein had represented gravitational forces as the result of certain features in the chrono-geometry of the world (the curvature of space). By dispensing with various assumptions and working with a more general geometry, Weyl was able to include electromagnetism in the geometrical scheme. Basing himself on the notion of parallel displacement and adopting the axiom of affine geometry, Eddington generalized Weyl's ideas, thus giving a conceptual or graphical representation of physical phenomena which allowed a new insight into them. The most outstanding feature of the theory is the notion of a unit of interval at every point in space-time: what is called a metre at any place and in any direction is a constant fraction of the radius of curvature of space-time for that place and direction.
The last decade of his life was almost wholly occupied with his quest for precise connections between the cosmological constants and the constants of atomic physics. In 1933 he had published his small popular book "The Expanding Universe," a subject which has taken such a firm hold on the imaginations of astronomers, both observational and theoretical. In that book he had developed his views of phenomena that might be expected in a finite, expanding spherical universe of the type first suggested by Einstein, later investigated by a distinguished pupil of Eddington's, Canon (then Abbé) G. Lemaitre of Louvain. According to this model—which is not accepted by all astronomers—external galaxies (more often known as spiral nebulae) are receding from one another, much as would a distribution of spots on the surface of a rubber balloon that was being inflated, with the difference that in nature the surface of the balloon is replaced by three-dimensional space. Great interest attaches to the radius of the balloon, in such a model, its rate of expansion, and the total number of spots on it; that is the radius of curvature of space, Hubble's space constant describing the ratio of recession-velocity to distance for any individual galaxy, and the mean density of matter in space. These are the "cosmological constants." The "physical constants" principally concerned are the masses of the proton and electron and their charges of electricity; and fittingly uniting the two sets, as it careers through the vast cosmical spaces, is light, represented by its velocity. Astronomers are agreed that the Newtonian "constant of gravitation" - whether really constant or not - can be calculated in terms of the other cosmological constants and the speed of light, but Eddington was alone, almost, in believing that there was a deeper connection between these constants and those fundamental laboratory constants whose existence was first demonstrated by the former Master of Eddington's own college of Trinity, Sir J. J. Thomson. Again and again Eddington in recent papers had returned to this theme.
In 1943 he published a notable complete account of his researches in his lectures before the Dublin Institute for Advanced Studies, entitled "The Combination of Relativity Theory and Quantum Theory." Last June he gave an account before the Royal Astronomical Society of "The Recession Constant of the Galaxies," in which he brought up to date his work published in 1931; this paper contains an amusing account, in Eddington's characteristic forms of expression, of a "timetable of the universe," setting forth the various times that have elapsed, according to his theory, between the epoch at which the universe "burst," or ceased to consist of causally influencing parts, and (for example) the extreme limit of past time (the so-called epoch of creation), or the date after which light could not travel right around the universe. It is fair to say that these researches have not carried anything like complete conviction to his contemporaries, either to those working on similar lines or to those who are out-and-out critics. But there is little doubt that magnificent fields of investigation have been opened up by the genius of Eddington—stellar motions, stellar interiors, relativity, the frontiers between metaphysics and pure science, and his name will be an inspiration to the rising generation of astronomers and to the generations that are to follow them,
Eddington's own researches and those of his contemporaries were summed up as he went along in a number of deservedly popular books, some addressed to specialists, others to the general public. He was elected a Fellow of the Royal Society in 1914 and was awarded its Royal Medal in 1928. He was an honorary D.Sc. of a number of universities: and he was president of the Royal Astronomical Society from 1921 to 1923, and of the Physical Society from 1930 to 1932. In 1930 he was knighted, and in 1938 was given the O.M.
CAMBRIDGE PROFESSOR OF ASTRONOMY
Sir Arthur Stanley Eddington, O.M., D.Sc., F.R.S., Plumian Professor of Astronomy at Cambridge University, died at Cambridge yesterday. He was a gifted astronomer whose original theories and powers of mathematical analysis took his science a long way forward; he was a brilliant expositor of physics and astronomy, able to communicate the most difficult conceptions in the simplest and most fascinating language; and he was an able interpreter to philosophers of the significance of the latest scientific discoveries.
Born on December 28, 1882, at Kendal, Westmorland, he was the son of Arthur H. Eddington, headmaster of the Friends' School in Kendal, where, towards the end of the eighteenth century, John Dalton, founder of the atomic theory, had been assistant master and later joint manager Eddington was educated at Bryn Melyn, Weston-super-Mare, and at Owens College, Manchester, where he won all the honours it had to offer, culminating in first place in the brilliant physics class list of 1902. His literary gifts were also marked, his proficiency in Greek indicating that, had he so chosen, he could have made his mark in the humanities no less than in science. Next, he went to Trinity College, Cambridge, where he became a scholar and, in 1904, was Senior Wrangler. The next year, he obtained a First Class in Part II of the Mathematical Tripos. He took the B.Sc. degree from London University, obtaining a scholarship for physics in the final honour examination. He was Smiths Prizeman at Cambridge in 1907 and, in the same year, was elected to a Fellowship at Trinity.
Eddington's astronomical work was done in two places admirably suited to combining practice with theory. From 1906 to 1913, he was chief assistant at the Royal Observatory, Greenwich, and there laid a sound observational foundation for his future work. In 1913 he was elected Plumian Professor of Astronomy at Cambridge, and the directorship of the University Observatory fell to him the next year. His original work was along four main lines: the investigation of stellar systems, a study of the internal constitution of the stars, an extension of the theory of relativity, and a linking of atomic structure with cosmogony. The thoroughness of his groundwork is shown by a paper in 1910 in which he analyzed the 6,188 stars of Professor Boss's preliminary general catalogue. As a result of his studies of the proper motions of the so-called fixed stars, he postulated (following Kapteyn) that the stars did not move indiscriminately but tended to follow two favoured directions, forming two "star streams. "
In 1916 Eddington began studying the radiative equilibrium of stars. He developed the hypothesis that the equilibrium of a star is the result of a balance between the inward forces of gravitation and the outward pressure of radiation from the star's central regions. The outer matter of the star tends to fall towards the centre under its own weight, but radiation from the centre preserves equilibrium. This balancing of forces also permitted an explanation of the fact that the masses of the various stars are not greatly dissimilar but are mostly of the order of a thousand quadrillion tons. It involved the conclusion that large stars were tenuous and small stars dense.
One of Eddington's most brilliant discoveries was a correlation between the mass and luminosity of stars, which he announced in 1924. This showed not only that the absolute luminosity of a star increased with its mass, but that the luminosity per unit mass also increased. The law, a remarkable combination of theory and observation, gave astronomers a means of calculating the masses of the thousands of stars whose luminosities could be accurately measured. Eddington extended his work in this direction to cover the Cepheid variables, stars like Cephei which pulsate in a definite period. It was found that Cepheid variables of the same period in different parts of the universe were closely similar, and so Eddington graphically described them as "standard candles."
In 1917 Eddington received from de Sitter a copy of Einstein's famous paper on the theory of relativity, and at that time it was probably the only copy in England. He was immediately won to the theory, and his "report" to the Physical Society in 1918 made many more converts. His brilliant exposition led Einstein to commend him as the best interpreter of the theory. But he did more than expound; he confirmed the theory by observation and extended it mathematically. His particular contribution to relativity was a generalization of Weyl's theory by which electromagnetic phenomena had been included with gravitation in the geometry of the world. Einstein had represented gravitational forces as the result of certain features in the chrono-geometry of the world (the curvature of space). By dispensing with various assumptions and working with a more general geometry, Weyl was able to include electromagnetism in the geometrical scheme. Basing himself on the notion of parallel displacement and adopting the axiom of affine geometry, Eddington generalized Weyl's ideas, thus giving a conceptual or graphical representation of physical phenomena which allowed a new insight into them. The most outstanding feature of the theory is the notion of a unit of interval at every point in space-time: what is called a metre at any place and in any direction is a constant fraction of the radius of curvature of space-time for that place and direction.
The last decade of his life was almost wholly occupied with his quest for precise connections between the cosmological constants and the constants of atomic physics. In 1933 he had published his small popular book "The Expanding Universe," a subject which has taken such a firm hold on the imaginations of astronomers, both observational and theoretical. In that book he had developed his views of phenomena that might be expected in a finite, expanding spherical universe of the type first suggested by Einstein, later investigated by a distinguished pupil of Eddington's, Canon (then Abbé) G. Lemaitre of Louvain. According to this model—which is not accepted by all astronomers—external galaxies (more often known as spiral nebulae) are receding from one another, much as would a distribution of spots on the surface of a rubber balloon that was being inflated, with the difference that in nature the surface of the balloon is replaced by three-dimensional space. Great interest attaches to the radius of the balloon, in such a model, its rate of expansion, and the total number of spots on it; that is the radius of curvature of space, Hubble's space constant describing the ratio of recession-velocity to distance for any individual galaxy, and the mean density of matter in space. These are the "cosmological constants." The "physical constants" principally concerned are the masses of the proton and electron and their charges of electricity; and fittingly uniting the two sets, as it careers through the vast cosmical spaces, is light, represented by its velocity. Astronomers are agreed that the Newtonian "constant of gravitation" - whether really constant or not - can be calculated in terms of the other cosmological constants and the speed of light, but Eddington was alone, almost, in believing that there was a deeper connection between these constants and those fundamental laboratory constants whose existence was first demonstrated by the former Master of Eddington's own college of Trinity, Sir J. J. Thomson. Again and again Eddington in recent papers had returned to this theme.
In 1943 he published a notable complete account of his researches in his lectures before the Dublin Institute for Advanced Studies, entitled "The Combination of Relativity Theory and Quantum Theory." Last June he gave an account before the Royal Astronomical Society of "The Recession Constant of the Galaxies," in which he brought up to date his work published in 1931; this paper contains an amusing account, in Eddington's characteristic forms of expression, of a "timetable of the universe," setting forth the various times that have elapsed, according to his theory, between the epoch at which the universe "burst," or ceased to consist of causally influencing parts, and (for example) the extreme limit of past time (the so-called epoch of creation), or the date after which light could not travel right around the universe. It is fair to say that these researches have not carried anything like complete conviction to his contemporaries, either to those working on similar lines or to those who are out-and-out critics. But there is little doubt that magnificent fields of investigation have been opened up by the genius of Eddington—stellar motions, stellar interiors, relativity, the frontiers between metaphysics and pure science, and his name will be an inspiration to the rising generation of astronomers and to the generations that are to follow them,
Eddington's own researches and those of his contemporaries were summed up as he went along in a number of deservedly popular books, some addressed to specialists, others to the general public. He was elected a Fellow of the Royal Society in 1914 and was awarded its Royal Medal in 1928. He was an honorary D.Sc. of a number of universities: and he was president of the Royal Astronomical Society from 1921 to 1923, and of the Physical Society from 1930 to 1932. In 1930 he was knighted, and in 1938 was given the O.M.
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