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Eddington, Arthur Stanley

Eddington, Arthur Stanley

(b. Kendal, England, 28 December 1882; d. Cambridge, England, 22 November 1944)

astronomy, relativity.

Eddington was the son of a Somerset Quaker, Arthur Henry Eddington, headmaster of Stramongate School in Kendal from 1878 until his death in 1884, and of Sarah Ann Shout, whose forebears for seven generations had been north-country Quakers. Following the death of her husband, Mrs. Eddington took Arthur Stanley, not yet two, and her daughter Winifred, age six, back to Somerset, where they made their home at Weston-super-Mare. In the atmosphere of this quiet Quaker home, the boy grew up. He remained a Quaker throughout his life.

Eddington’s schooling was fortunate. Brynmelyn School, to which he went as a day boy, had three exceptionally gifted teachers who imparted to him a keen interest in natural history, a love of good literature, and a splendid foundation in mathematics. Reserved and studious by nature, Eddington was also physically active, playing on the first eleven at both cricket and football and enjoying long bicycle rides through the Mendip Hills. Before he was sixteen, he won an entrance scholarship to Owen’s College (now the University of Manchester), where again he was fortunate in his teachers—Arthur Schuster in physics and Horace Lamb in mathematics. In the autumn of 1902, with an entrance scholarship, Eddington went into residence at Trinity College, Cambridge.

After two years of intensive concentration on mathematics under the guidance of the distinguished coach R. A. Herman, who stressed both the logic and the elegance of mathematical reasoning, Eddington sat the fourteen papers of the tripos examinations in 1904. He won the coveted position of first wrangler, the first time that a second-year man had attained this distinction. In 1905 he gained his degree and proceeded to coach pupils in applied mathematics and to lecture in trigonometry during the following term.

In February 1906 Eddington took an appointment as chief assistant at the Royal Observatory, Greenwich, where he remained until 1913. Here he obtained thorough training in practical astronomy and began the pioneer theoretical investigations that placed him in the forefront of astronomical research in a very few years. Besides his participation in the regular observing programs, Eddington had two special assignments: he went to Malta in 1909 to determine the longitude of the geodetic station there, and to Brazil in 1912 as leader of an eclipse expedition. Two further tests of his ability as a practical astronomer came after his return to Cambridge as Plumian professor of astronomy and director of the observatory. During the war years Eddington completed single-handed the transit observations for the zodiacal catalog. In 1919 he organized the two eclipse expeditions that provided the first confirmation of the Einstein relativity formula for the deflection of light in a gravitational field.

During these years Eddington was elected to fellowships in the Royal Astronomical Society (1906) and the Royal Society (1914). He was knighted in 1930, and his greatest honor, the Order of Merit, was conferred on him eight years later.

Eddington was president of the Royal Astronomical Society from 1921 to 1923 and of the Physical Society and the Mathematical Association from 1930 to 1932. In 1938 he became president of the International Astronomical Union. After his death an annual Eddington Memorial Lectureship was established and the Eddington Medal was struck for annual award, the first recipient being a former pupil of Eddington’s, Canon Georges Lemaître of Louvain.

Eddington never married. After his appointment in 1913 to the Plumian professorship in Cambridge, he moved into Observatory House as director of the observatory and brought his mother and sister to live with him. Here he remained until the autumn of 1944, when he underwent a major operation from which he did not recover.

Of Eddington’s scientific work, particularly in the field of stellar structure, E. A. Milne wrote in 1945 that he “brought it all to life, infusing it with his sense of real physics and endowing it with aspects of splendid beauty.... Eddington will always be our incomparable pioneer.” His intuitive insight into the profound problems of nature, coupled with his mastery of the mathematical tools, led him to illuminating results in a wide range of problems: the motions and distribution of the stars, the internal constitution of the stars, the role of radiation pressure, the nature of white dwarfs, the dynamics of pulsating stars and of globular clusters, the sources of stellar energy, and the physical state of interstellar matter. In addition, he was the first interpreter of Einstein’s relativity theory in English, and made his own contributions to its development; and he formulated relationships between all the principal constants of nature, attempting a vast synthesis in his provocative but uncompleted Fundamental Theory.

It is important to remember how rudimentary was much of our knowledge of astrophysics and of stellar movements at the beginning of this century. Proper motion or transverse motion had been known since the time of Halley and radial velocity since Doppler, but the assumption of William Herschel of random motion of the stars relative to the sun had been abandoned of necessity by Kapteyn in 1904. Schwarzschild attempted to show that the radial velocity vectors could be represented as forming an ellipsoid. This problem of the systematic motions of the stars was the subject of Eddington’s first theoretical investigations. He chose to work with proper motions and isolated two star streams or drifts. In 1917 he compared the two theories thus:

The apparent antagonism between the two-drift and the ellipsoidal hypotheses disappears if we remember that the purpose of both is descriptive. Whilst the twodrift theory has often been preferred in the ordinary proper motion investigations on account of an additional constant in the formulae which gives it a somewhat greater flexibility, the ellipsoidal theory has been found more suitable for discussions of radial velocities and the dynamical theory of the stellar system [Monthly Notices of the Royal Astronomical Society, 77 , 314].

Eddington’s remarkable statistical analyses of proper-motion data fully confirmed the existence of the two star streams, and he was able to determine their directions and relative numbers. He went on to other problems, such as the distribution of stars of different spectral classes, planetary nebulae, open clusters, gaseous nebulae, and the dynamics of globular clusters. In his first book, Stellar Movements and the Structure of the Universe (1914), Eddington brought together all the material of some fifteen papers, most of which had been published in the Monthly Notices of the Royal Astronomical Society between 1906 and 1914. The cosmological knowledge of the period was summarized and the most challenging problems were delineated, and he clearly declared his preference for the speculation that the spiral nebulae were other galaxies beyond our Milky Way, which was itself a spiral galaxy.

Eddington’s great pioneer work in astrophysics began in 1916. His first problem was radiation pressure, the importance of which had been pointed out a decade earlier by R. A. Sampson. A theory of the radiative equilibrium of the outer atmosphere of a star was subsequently developed by Schwarzschild in Germany. Eddington delved deeper, in fact to the very center of a star, showing that the equation of equilibrium must take account of three forces— gravitation, gas pressure, and radiation pressure. Replacing the assumption of convective equilibrium of Lane, Ritter, and Emden with radiative equilibrium, he developed the equation that is still in general use. At that time he felt justified in assuming that perfect gas conditions existed in a giant star, and he adopted Emden’s equation for a polytropic sphere with index n = 3. This is still referred to as Eddington’s model of a star. Not until 1924 did he realize that this assumption and, therefore, this model were also applicable to dwarf stars.

That matter under stellar conditions would be highly ionized had been recognized by several astronomers, but it was Eddington who first incorporated this into the theory of stellar equilibrium by showing that high ionization of a gas reduced the average molecular weight almost to 2 for all elements except hydrogen.

Finding that the force of radiation pressure rose with the mass of the star, and with startling rapidity as the mass exceeded that of our sun, Eddington concluded that relatively few stars would exceed ten times the sun’s mass and that a star of fifty times the solar mass would be exceedingly rare. To obtain a theoretical relation between mass and luminosity of a star, some assumption was necessary about internal opacity. At first he regarded opacity as mainly a photoelectric phenomenon, a view that drew strong criticism; but when Kramers’ theory of the absorption coefficient became available, Eddington adapted it to the stellar problem, introducing his “guillotine” factor, and obtained his important mass-luminosity relation, announced in March 1924. Since the observational data for dwarf stars, as well as for giant stars, closely fitted the theoretical curve, he announced that dwarfs also must be regarded as gaseous throughout, in spite of their densities exceeding unity. He realized that the effective volume of a highly or fully ionized atom is very small, and hence deviations from perfect gas behavior will occur only in stars of relatively high densities. The mass-luminosity relation has been widely used and is still of immense value, although its applicability has been somewhat limited in recent years by the more detailed classification of both giants and dwarfs and by the recognition of the distinctive characteristics, for example, of subdwarfs, which do not conform to the mass-luminosity relation.

Eddington had calculated the diameters of several giant red stars as early as the summer of 1920. In December, G. E. Hale wrote him of the Pease and Anderson interferometer measurement of α Orionis on 13 December “in close agreement with your theoretical value and probably correct within about 10 per cent.” Later Eddington applied his calculations to the dwarf companion of Sirius, obtaining a diameter so small that the star’s density came out to 50,000 gm./cc., a deduction to which he said most people had mentally added “which is absurd!” However, in the light of his 1924 realization of the effects of high ionization, he claimed these great densities to be possible and probably actually to exist in the white dwarf stars. He therefore wrote W. S. Adams, asking him to measure the red shift in the Mount Wilson spectra of Sirius B, since, if a density of 50,000 or more did exist, then a measurable Einstein relativity shift to the red would result. Adams hastened to comply, and wrote Eddington that the measured shifts closely confirmed the calculated shift and, hence, confirmed both the third test of relativity theory and the immense densities that Eddington had calculated. (This exchange of historic letters in 1924 and 1925 is recorded in Arthur Stanley Eddington, pp. 75–77.)

A direct consequence of this work was the challenge it presented to physicists, a challenge taken up in 1926 by R. H. Fowler, who achieved a brilliant investigation of the physics of super-dense gas, afterward called “degenerate” gas, by employing the newly developed wave mechanics of Schrödinger.

A consequence of Eddington’s mass-luminosity relation was his realization that a time scale of several trillion (i.e., 1012) years was essential for the age of stars if the then current Russell-Hertzsprung sequence of stellar evolution was to be retained. Except in the rare case of a nova or supernova that hurls out much of its matter, the loss of mass by a star is due to radiation. For a massive O or B class star to radiate itself down to a white dwarf, at least a trillion years would be required. This brought into the limelight the theory of conversion of matter into radiation by annihilation of electrons and protons, a hypothesis that appears to have been first suggested by Eddington in 1917. For seven years, in spite of severe criticism in Great Britain, he defended the general idea that the chief source of stellar energy must be subatomic. After 1924 many astronomers and physicists turned their attention to this. In 1934, after the discovery of the positron, Eddington urged abandonment of the electron-proton annihilation theory, on the ground that electron-positron annihilation was not only a more logical supposition but also an observed fact. In 1938 came the famous carbon-nitrogen-oxygen-carbon cycle of Hans Bethe, elegantly solving some of the problems of stellar energy and invoking the electronpositron annihilation hypothesis.

In 1926 Eddington published his great compendium, The Internal Constitution of the Stars (reprinted in 1930). In this book he drew attention to the unsolved problems partially treated in his investigations, among them the problem of opacity and the source or sources of stellar energy, which he called “two clouds obscuring the theory.” Another obstinate problem was the phase relation of the light curve and the velocity curve of a Cepheid variable. In 1918 and 1919 he had published papers on the mathematical theory of pulsating stars, explaining many observed features of Cepheid variables but not the phase relation. He returned to this problem in 1941, when more was known about the convective layer and he could apply the physics of ionization equilibrium within this layer with encouraging results.

Other problems dealt with in these years were the central temperatures and densities of stars and the great cosmic abundance of hydrogen (recognized independently by Strömgren). Eddington developed a theory of the absorption lines in stellar atmospheres, extending earlier work of Schuster and Schwarzschild. This made possible the interpretation of many observed line intensities. When the “nebulium” lines were identified by Bowen in 1927 as the result of so-called forbidden transitions in ionized nitrogen and oxygen atoms, Eddington explained how and why these emission lines can be produced within the highly rarefied gases that constitute a nebula. Another line of adventurous thinking concerned the existence, composition, and absorptive and radiative properties of interstellar matter. He calculated the density and temperature and showed that calcium would be doubly ionized, with only about one atom in 800 being singly ionized. He discussed the rough measurement of the distance of a star by the intensity of its interstellar absorption lines, a relation soon confirmed by O. Struve and by J. S. Plaskett

In the field of astrophysics Eddington undoubtedly made his greatest—but by no means his only—contributions to knowledge. Here he fashioned powerful mathematical tools and applied them with imagination and consummate skill. But during these same years his mind was active along other lines; thus we have his profound studies on relativity and cosmology, his herculean but unsuccessful efforts to formulate his Fundamental Theory, and his brilliant, provocative attempts to portray the meaning and significance of the latest physical and metaphysical thinking in science.

Einstein’s famous 1915 paper on the general theory of relativity came to England in 1916, when deSitter, in Holland, sent a copy to Eddington, who was secretary of the Royal Astronomical Society. Immediately recognizing its importance and the revolutionary character of its implications, Eddington threw himself into a study of the new mathematics involved, the absolute differential calculus of Ricci and Levi-Civita. He was soon a master of the use of tensors and began developing his own contributions to relativity theory. At the request of the Physical Society of London, he prepared his Report on the Relativity Theory of Gravitation (1918), the first complete account of general relativity in English. He called it a revolution of thought, profoundly affecting astronomy, physics, and philosophy, setting them on a new path from which there could be no turning back. A second edition (1920) contained the results of the eclipse expeditions of 1919, which had appeared to confirm the bending of light in a gravitational field, as predicted by Einstein’s theory; it also contained a warning that the theory must meet the test of the reddening of light emitted from a star of sufficient density. This test was met when the measurements on Sirius B made by W. S. Adams at Eddington’s request were announced in 1924.

Eddington published a less technical account of relativity theory, Space, Time and Gravitation, in 1920. This book brought to many readers at least some idea of what relativity theory was and where it was leading in cosmological speculation. It showed, too, how Eddington’s mind had already entered philosophical grooves in which it continued to run—his selective subjectivism, almost universally repudiated, and his logical theory of structure, “a guiding illumination,” in the words of Martin Johnson, who added, “As elucidator of the logical status of physics, Eddington led well his generation.”

In 1923 came Eddington’s great book, Mathematical Theory of Relativity. Einstein said in 1954 that he considered this book the finest presentation of the subject in any language, and of its author he said, “He was one of the first to recognize that the displacement field was the most important concept of general relativity theory, for this concept allowed us to do without the inertial system.”

In this book Eddington gave the substance of the original papers of Einstein, deSitter, and Weyl but departed from their presentations to give a “continuous chain of deduction,” including many contributions of his own, both in interpretation and in derivation of equations. With intuitive brilliance he modified Weyl’s affine geometry of world structure by means of a new mathematical procedure, parallel displacement, which in itself was a not unimportant contribution to geometry. This led to his explanation of the law of gravitation (Gμν = λgμν) as implying that our practical unit of length at any point and in any direction is a definite fraction of the radius of curvature for tha point and direction, so that the law of gravitation is simply the statement of the fact that the world radius of curvature everywhere supplies the standard with which our measure lengths are compared. This led subsequently to his theoretical determination of the cosmic constant λ. Assuming the principle that the wave equation determining the linear dimensions of an atomic system must give these dimensions in terms of the standard world radius, he obtained a value for λ in terms of the atomic constants that appear in the ordinary form of the wave equation.

This fascination with the fundamental constants of nature—the gravitation constant, the velocity of light, the Planck and Rydberg constants, the mass and charge of the electron, for example—and the basic problem of atomicity had driven Eddington to seek this bridge between quantum theory and relativity. Having found it, he eventually established relationships between all these and many more constants, showing their values to be logically inevitable. From seven basic constants Eddington derived four pure numbers, including the famous 137 forever associated with his name. This is the fine structure constant. He evolved the equation 10m2 – 136m + 1 = 0, the coefficients of which are in accordance with the theory of the degrees of freedom associated with the displacement relation between two charges and the roots of which give the ratio of masses of proton and electron as 1847.60. He showed that the packing factor for helium should be 136/137. Later Eddington identified the total number of protons and electrons in the universe with the number of independent quadruple wave functions at a point; he evaluated this constant as 3/2 × 136 × 2256, which is a number of the order of 1079. In all, he evaluated some twenty-seven physical constants.

As all this work proceeded, Eddington published a succession of books, both technical and nontechnical, dealing with the above problems and also with the new problems that were arising in cosmological theories. The spherical Einstein universe was found to be unstable, and in 1927 Georges Lemaître published in an obscure journal his cosmology of an expanding universe, the result of the catastrophic explosion of a primeval atom containing all the matter of the universe. He sent a reprint to Eddington only in 1930. Immediately his own modification of this became the basis of all of Eddington’s further work in this field. In 1928 Dirac published his new interpretation of the Heisenberg symbols q and p, an approach to a recondite subject that sent Eddington’s mind racing off in a new direction. He developed a theory of matrices providing “a simple derivation of the first order wave equation, equivalent to Dirac’s but expressed in symmetrical form” and also “a wave equation which we can identify as relating to a system containing electrons with opposite spin.” He then developed his E-number theory, which proved to be a powerful tool in much subsequent work.

The Nature of the Physical World (1928) and The Expanding Universe (1933) deal with the above ideas and his, epistemological interpretation. New Pathways in Science (1935) and The Philosophy of Physical Science (1939) carried his ideas further. All these books are rich in literary excellence and in the sparkle of his imagination and humor, as well as being gateways to new ideas and adventures in thinking.

His technical book The Relativity Theory of Protons and Electrons (1936), based almost wholly on the spin extension of relativity, spurred Eddington to evolve a statistical extension. Thus, during his last years he worked indomitably toward his dream—“Bottom’s dream,” he called it—his vision of a harmonization of quantum physics and relativity. The difficulties were immense and, as we now know, the greatest complexities of nuclear physics and subatomic particles were not yet discovered. But he took hurdle after hurdle as he saw them, with daring leaps, always landing, as he believed, surefootedly on the far side, even though he could not demonstrate his trajectories with mathematical rigor.

The obscurities and gaps in logical deduction in Fundamental Theory have discouraged most scientists from taking it seriously, but a few able men— Whittaker, Lemaître, Bastin, Kilmister, Slater—have seen Eddington’s vision and have felt it worthwhile to explore further. Slater isolated an erroneous numerical factor in Eddington’s work, a factor of 9/4 which modified the calculated recessional constant that had agreed reasonably well with the Mount Wilson observed value. Thus, in 1944, although he did not realize it himself, Eddington’s theory had really demanded the change in the distance scale of the universe that Baade announced in 1952 from observational studies of the Cepheid variables in the Andromeda galaxy.

Eddington’s biographer has referred to Fundamental Theory as an “unfinished symphony” standing as a challenge to “the musicians among natural philosophers of the future.” His mystical approach to all experience necessarily embraced the sensual, the mental, and the spiritual. He believed that truth in the spiritual realm must be directly apprehended, not deduced from scientific theories. His Swarthmore Lecture to the Society of Friends, published as Science and the Unseen World (1929), and his chapter entitled “The Domain of Physical Science” in Science, Religion and Reality (1925), as well as passages throughout his books, reveal a deeply sincere, mystical, yet essentially simple, approach to consideration of the things of the spirit. In the search for truth, whether it be measurable or immeasurable, “It is the search that matters,” he wrote. “You will understand the true spirit neither of science nor of religion unless seeking is placed in the forefront.”


I. Original Works. Eddington’s books are Stellar Movements and the Structure of the Universe (London, 1914); Report on the Relativity Theory of Gravitation (London, 1918); Space, Time, and Gravitation (Cambridge, 1920); Mathematical Theory of Relativity (Cambridge, 1923); The Internal Constitution of the Stars (Cambridge, 1926); Stars and Atoms (Oxford, 1927), Eddington’s only popular account of astrophysical researches; The Nature of the Physical World (Cambridge, 1928); Science and the Unseen World (London, 1929); The Expanding Universe (Cambridge, 1933, 1940); New Pathways in Science (Cambridge, 1935); Relativity Theory of Protons and Electrons (Cambridge, 1936); The Philosophy of Physical Science (Cambridge, 1939); and Fundamental Theory, Edmund T. Whittaker, ed. (Cambridge, 1946), published posthumously.

II. Secondary Literature. Writings on Eddington or his work include Herbert Dingle, The Sources of Eddington’s Philosophy (Cambridge, 1954), an Eddington Memorial Lecture; A. Vibert Douglas, Arthur Stanley Eddington (Edinburgh and New York, 1956), a biography that includes a comprehensive list of Eddington’s books and more than 150 scientific papers on pp. 193–198 and a genealogical table, pp. 200–201; Martin Johnson, Time and Universe for the Scientific Conscience (Cambridge, 1952), an Eddington, Memorial Lecture; C. W. Kilmister, Sir Arthur Eddington, in Selected Readings in Physics series (London, 1966); C. W. Kilmister and B. O. J. Topper, Eddington’s Statistical Theory (Oxford, 1962); S. R. Milner, Generalized Electrodynamics and the Structure of Matter (Sheffield, 1963); J. R. Newman, Science and Sensibility, I (London, 1961); A. D. Ritchie, Reflections on the Philosophy of Sir Arthur Eddington (Cambridge, 1947), an Eddington Memorial Lecture; Noel B. Slater, Eddington’s Fundamental Theory (Cambridge, 1957); Edmund Whittaker, From Euclid to Eddington (Cambridge, 1949), and Eddington’s Principle in the Philosophy of Science (Cambridge, 1951), an Eddington Memorial Lecture; and J. W. Yolton, The Philosophy of Science of A. S. Eddington (The Hague, 1960).

A. Vibert Douglas

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"Eddington, Arthur Stanley." Complete Dictionary of Scientific Biography. . 23 Jun. 2017 <>.

"Eddington, Arthur Stanley." Complete Dictionary of Scientific Biography. . (June 23, 2017).

"Eddington, Arthur Stanley." Complete Dictionary of Scientific Biography. . Retrieved June 23, 2017 from

Eddington, Arthur Stanley


(b. Kendal, United Kingdom, 28 December 1882;

d. Cambridge, United Kingdom, 22 November 1944), astronomy, astrophysics, relativity, science and religion. For the original article on Eddington see DSB, vol. 4.

Scholarship following the original DSB article provided new insights into Eddington’s educational background, his work in relativity and the 1919 eclipse expedition, his role in teaching and training physicists, his contributions to stellar physics, and the significance of his popular and philosophical writings.

Education . An important feature of Eddington’s education was his location in Manchester, which just before and during his time was the site of a movement known as the “Quaker Renaissance.” This involved a body of Quakers who argued that their religious tradition needed to embrace modernity. In particular, they sought harmonious relationships between religion and “modern thought” (largely science). Eddington was mentored by the leaders of this movement such as John William Graham, and their emphasis on values of mysticism, internationalism, pacifism, and civic engagement can be seen in many parts of Eddington’s career.

Relativity and the 1919 Eclipse Expedition . By the early 2000s, it was clear that Eddington’s advocacy of Albert Einstein and relativity was also a defense of internationalism in science, which he felt was seriously threatened by Great War jingoism. Eddington’s Quaker values of pacifism and internationalism made supporting Einstein’s theory a religious task as well as a scientific one, which helps explain why Eddington was virtually alone among British scientists in embracing German science during the war. He thus promoted the 1919 eclipse expedition as a landmark of scientific internationalism triumphing over war, in addition to its technical significance.

A controversial topic has been whether Eddington’s interest in relativity led him to manipulate the data of the expedition to provide a favorable outcome. This accusation of fraud usually rests on the rejection as unreliable of one of the three sets of data brought back in 1919. It is noted by critics that that discarded set was the only one of the three which did not support Einstein’s prediction, and Eddington is typically accused of a conspiracy to hide the unfavorable results. However, this claim ignores several important issues. First, the data were discarded because of optical problems during the eclipse observation in Brazil. These problems were noted in the field by the observers there (who did not include Eddington) long before the photographs were analyzed as being favorable or unfavorable to Einstein. Further, all three sets of data were made publicly available to the scientific community, and there were no objections from contemporary astronomers about the rejection of the corrupted data. Astronomers around the world were able to make their own measurements of the plates and agreed with Eddington’s analysis. It seems that the conspiracy theory is based on a misunderstanding of the optical techniques and data analysis methods in use at the time. Eddington’s contemporaries, well versed in the tacit knowledge involved in such difficult measurements, understood that the eclipse expedition results were well within the contemporary standards of scientific practice.

Teaching and Training . Historians interested in scientific training and pedagogy have examined Eddington’s difficulty in learning the technical details of general relativity without direct contact with Einstein. He took nearly two years to become skilled enough to make original contributions in the theory, even though he had significant advantages over most of his British colleagues: he had been taught differential geometry as an undergraduate, and was introduced to general relativity through Willem de Sitter, who had important experience in presenting Einstein’s theory in a comprehensible fashion. A tight relationship between Eddington’s pedagogy and his scientific work can be seen in the fact that Eddington’s first two books on relativity were almost certainly slight elaborations of his lecture notes for the first classes he taught on relativity. Virtually an entire generation of British scientists learned relativity from Eddington, and important aspects of his teaching can be traced through later developments in physics and astronomy.

Stellar Physics . Early twenty-first century historians of astronomy and physics have stressed that one of the difficulties Eddington encountered in his development of stellar models was that the physics of the day did not allow for a complete description of stellar interiors. This incompleteness led many physicists and astronomers holding to a deductive model of scientific truth to simply discard the problem as unworkable. For example, James Jeans argued that a physical model could not involve any unknown or partially understood agencies.

Eddington persevered and built a methodology on the idea that theories were pragmatic, approximate tools and did not need to be deductively certain. He constructed

his theoretical models on a variety of physical assumptions (often based on novel, hypothetical physics such as quantum mechanics), all designed to bring model and observation together as quickly as possible. Eddington argued that his method produced useful results (such as the mass-luminosity relation and the correct radii of stars) and avoided the sterile rigidity of the deductive approaches favored by his opponents. The debates over the sources of stellar energy provide a useful case study in the difficulty Eddington had in establishing his new theoretical astrophysics and in how he skillfully deployed cutting-edge work from both astronomy and physics.

Eddington’s later work in stellar physics led to his controversial exchanges with Subrahmanyan Chandrasekhar on the properties of dwarf stars and degenerate matter. The story has usually been told based on Chandrasekhar’s personal recollections and typically accuses Eddington of intentional cruelty and racist motivations in rejecting the Indian scientist’s theory. However, there is no evidence to suggest that this was the case. Eddington was famously vigorous in intellectual debate, and he treated Chandrasekhar just as he did his other rivals James Jeans and Edward Arthur Milne. Further, there is no reason to assume racism: for several years Eddington was the head of an organization which worked for Indian liberation.

Popular and Philosophical Writings . Eddington’s popular and philosophical works were analyzed closely by the early 2000s with respect to their cultural, intellectual, and social context. They were shown to not be completely idiosyncratic, but rather coherent parts of ongoing debates in interwar Britain. In the wake of the Great War, the cultural position of science was seriously contested.

Eddington’s popular books and lectures were designed to defend a liberal position in which science was perfectly compatible with traditional values, thus retaining both religion and science as critical elements of British identity and culture. He was particularly concerned with rejecting Marxist, materialist appropriations of science and their deterministic implications. However, he also rejected classical natural theology with its proofs of religion and rigid dogmatism. Eddington argued from a novel interpretation of positivism that religious experience and scientific experience were equally valid parts of human life, but that neither could prove any particular sectarian dogma. This ecumenical, reassuring position was quite popular in the interwar period with the last surge of liberal theology, but became less relevant with the death of that movement around World War II.


Bowler, Peter. Reconciling Science and Religion: The Debate in Early-Twentieth-Century Britain. Chicago: University of Chicago Press, 2001. Broad study of the relationship between science and religion in the interwar period.

Graham, Loren. Between Science and Values. New York: Columbia University Press, 1981. Chapters 2 and 3 discuss Eddington, particularly in contrast to Soviet expositors of relativity.

Hufbauer, Karl. “Astronomers Take up the Stellar-Energy Problem, 1917–1920.” Historical Studies in the Physical Sciences 11 (1981): 277–303.

Kenat, Ralph. “Physical Interpretation: Eddington, Idealization and the Origin of Stellar Structure Theory (Realism).” PhD diss., University of Maryland College Park, 1987.

Paul, Erich Robert. The Milky Way Galaxy and Statistical Cosmology. Cambridge, U.K.: Cambridge University Press, 1993. Discusses Eddington’s work in statistical cosmology.

Stanley, Matthew. “An Expedition to Heal the Wounds of War: The 1919 Eclipse Expedition and Eddington as Quaker Adventurer.” Isis 94 (2003): 57–89.

———. Practical Mystic: Religion and Science in the Life and Work of A. S. Eddington. Chicago: University of Chicago Press, 2007.

———. “So Simple a Thing as a Star: The Eddington-Jeans Debate over Astrophysical Phenomenology.” British Journal for the History of Science (2007).

Warwick, Andrew. Masters of Theory: Cambridge and the Rise of Mathematical Physics. Chicago: University of Chicago Press, 2003. Chapter 9 examines Eddington’s work on relativity in a pedagogical context.

Wilson, David. “On Removing ‘Science’ and ‘Religion’ from the Discussion of Science and Religion: The Cases of Eddington and Jeans.” In Facets of Faith and Science, edited by Jitse M. van der Meer. Lanham, MD: Pascal Centre for Advanced Studies in Faith and Science, University Press of America, 1996.

Matthew Stanley

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Sir Arthur Stanley Eddington

Sir Arthur Stanley Eddington

The English astronomer Sir Arthur Stanley Eddington (1882-1944) greatly advanced theoretical astrophysics as a consequence of his original contributions to the theory of relativity and his studies on the internal constitution of stars.

Arthur S. Eddington was born on Dec. 28, 1882, at Kendal, Westmorland. His father was the headmaster and proprietor of a school where John Dalton once taught. Arthur was a precocious child, and by his own account had mastered the 24 x 24 multiplication table before he could read. He received his bachelor's degree in 1902 from Owens College, Manchester, and immediately proceeded to Trinity College, Cambridge. At Cambridge he placed first in the mathematical tripos examination in his second year, an unprecedented achievement. In 1905 he took his bachelor's degree from Cambridge University; in 1907 he became Smith's Prize winner and was elected a fellow of Trinity College; and in 1909 he obtained his master's degree.

In 1906 Eddington was appointed chief assistant at the Royal Observatory at Greenwich. He remained there for 7 years, gaining much practical astronomical experience. While there he initiated a program for determining latitude variation of stars which, with modifications, is still in force today, and engaged in theoretical researches on the systematic motions and distributions of the stars recorded in the Groombridge Catalog. These last studies formed the basis of his Smith's Prize essay and culminated in his book Stellar Movements and the Structure of the Universe (1914). One important result was that he confirmed Jacobus Kapteyn's 1904 conclusion that there are two star streams in the Milky Way.

In 1913 Eddington was appointed Plumian professor of astronomy at Cambridge; a year later he became director of the Cambridge Observatory and was elected a fellow of the Royal Society. During World War I he began studies on Albert Einstein's general theory of relativity and on stellar structure. As secretary of the Royal Astronomical Society, Eddington received for publication a copy of Einstein's paper of 1915, the only one to reach England during the war. By the end of the war Eddington had become one of the few men to master Einstein's general theory, had made original contributions to it, and had written the first account of it in English.

In 1919 Eddington led the famous solar eclipse expedition to West Africa and proved, as Einstein's theory demanded, that starlight is deflected in passing close to a massive body such as the sun. Later, Eddington generalized H. Weyl's theory of the electromagnetic field, and in 1925 W. S. Adams spectroscopically verified Eddington's 1924 prediction of a large gravitational red shift of the light emitted by Sirius's white dwarf companion. In 1930 Eddington proved that an Einstein universe is unstable, thereby lending support to the concept of an expanding universe.

In 1915 Eddington also began studying the internal constitution of stars, a subject largely of his own creation. During the ensuing years he demonstrated, for example, the importance of radiation pressure in helping thermal pressure maintain a star's stability against gravitational collapse. He, as well as Harlow Shapley, showed that variable stars change their brightness because they pulsate. He also derived his famous mass-luminosity law, which shows that the more massive a star, the brighter it is.

Eddington was a master of popular science writing, a talent which he exploited especially after 1927. He also increasingly expounded his controversial philosophical and theological convictions. Moreover, spurred on by Paul Dirac's 1928 discovery of the relativistic wave equation for the electron, Eddington during the last 16 years of his life attempted to wed relativity to quantum theory in what came to be called his fundamental theory. Undisturbed by the criticism that this elegant but speculative theory evoked, Eddington pursued it to the end. Few today accept it, but its positive elements may one day be reborn in different form.

Eddington was knighted in 1930 and received numerous honors throughout his life, including the coveted Order of Merit in 1938. He remained a bachelor and died in Cambridge on Nov. 22, 1944.

Further Reading

A full-length biography of Eddington is Allie Vibert Douglas, The Life of Arthur Stanley Eddington (1956). For a shorter biographical sketch see H. C. Plummer's obituary notice in the Biographical Memoirs of the Fellows of the Royal Society, vol. 5 (1945-1948). See also John W. Yolton, The Philosophy of A. S. Eddington (1960).

Additional Sources

Chandrasekhar, S. (Subrahmanyan), Eddington, the most distinguished astrophysicist of his time, Cambridge; New York: Cambridge University Press, 1983. □

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