Sir Arthur Stanley Eddington
(28 December 1882 – 22 November 1944) was an English astronomer, physicist, and mathematician. He was also a
philosopher of science and a populariser of science. The
Eddington limit
The Eddington luminosity, also referred to as the Eddington limit, is the maximum luminosity a body (such as a star) can achieve when there is balance between the force of radiation acting outward and the gravitational force acting inward. The stat ...
, the natural limit to the
luminosity
Luminosity is an absolute measure of radiated electromagnetic power (light), the radiant power emitted by a light-emitting object over time. In astronomy, luminosity is the total amount of electromagnetic energy emitted per unit of time by a st ...
of stars, or the radiation generated by accretion onto a compact object, is named in his honour.
Around 1920, he foreshadowed the discovery and mechanism of nuclear fusion processes in stars, in his paper "The Internal Constitution of the Stars".
[The Internal Constitution of the Stars A. S. Eddington The Scientific Monthly Vol. 11, No. 4 (Oct., 1920), pp. 297–303 ] At that time, the source of stellar energy was a complete mystery; Eddington was the first to correctly speculate that the source was fusion of hydrogen into helium.
Eddington wrote a number of articles that announced and explained
Einstein's theory of
general relativity
General relativity, also known as the general theory of relativity and Einstein's theory of gravity, is the geometric theory of gravitation published by Albert Einstein in 1915 and is the current description of gravitation in modern physics ...
to the English-speaking world.
World War I
World War I (28 July 1914 11 November 1918), often abbreviated as WWI, was List of wars and anthropogenic disasters by death toll, one of the deadliest global conflicts in history. Belligerents included much of Europe, the Russian Empire, ...
had severed many lines of scientific communication, and new developments in German science were not well known in England. He also conducted
an expedition to observe the
solar eclipse of 29 May 1919
A total solar eclipse occurred on Thursday, May 29, 1919. With the duration of totality at maximum eclipse of 6 minutes 50.75 seconds, it was the longest solar eclipse since May 27, 1416. A longer total solar eclipse would later occur on June 8 ...
that provided one of the earliest confirmations of general relativity, and he became known for his popular expositions and interpretations of the theory.
Early years
Eddington was born 28 December 1882 in
Kendal
Kendal, once Kirkby in Kendal or Kirkby Kendal, is a market town and civil parish in the South Lakeland district of Cumbria, England, south-east of Windermere and north of Lancaster. Historically in Westmorland, it lies within the dale of t ...
,
Westmorland
Westmorland (, formerly also spelt ''Westmoreland'';R. Wilkinson The British Isles, Sheet The British IslesVision of Britain/ref> is a historic county in North West England spanning the southern Lake District and the northern Dales. It had an ...
(now
Cumbria
Cumbria ( ) is a ceremonial and non-metropolitan county in North West England, bordering Scotland. The county and Cumbria County Council, its local government, came into existence in 1974 after the passage of the Local Government Act 1972. ...
), England, the son of
Quaker
Quakers are people who belong to a historically Protestant Christian set of denominations known formally as the Religious Society of Friends. Members of these movements ("theFriends") are generally united by a belief in each human's abili ...
parents, Arthur Henry Eddington, headmaster of the Quaker School, and Sarah Ann Shout.
His father taught at a Quaker training college in Lancashire before moving to Kendal to become headmaster of Stramongate School. He died in the
typhoid
Typhoid fever, also known as typhoid, is a disease caused by ''Salmonella'' serotype Typhi bacteria. Symptoms vary from mild to severe, and usually begin six to 30 days after exposure. Often there is a gradual onset of a high fever over several d ...
epidemic which swept England in 1884. His mother was left to bring up her two children with relatively little income. The family moved to
Weston-super-Mare where at first Stanley (as his mother and sister always called Eddington) was educated at home before spending three years at a preparatory school. The family lived at a house called Varzin, 42 Walliscote Road, Weston-super-Mare. There is a commemorative plaque on the building explaining Sir Arthur's contribution to science.
In 1893 Eddington entered Brynmelyn School. He proved to be a most capable scholar, particularly in mathematics and English literature. His performance earned him a scholarship to Owens College, Manchester (what was later to become the
University of Manchester
The University of Manchester is a public university, public research university in Manchester, England. The main campus is south of Manchester city centre, Manchester City Centre on Wilmslow Road, Oxford Road. The university owns and operates majo ...
) in 1898, which he was able to attend, having turned 16 that year. He spent the first year in a general course, but turned to
physics
Physics is the natural science that studies matter, its fundamental constituents, its motion and behavior through space and time, and the related entities of energy and force. "Physical science is that department of knowledge which ...
for the next three years. Eddington was greatly influenced by his physics and mathematics teachers,
Arthur Schuster and
Horace Lamb. At Manchester, Eddington lived at Dalton Hall, where he came under the lasting influence of the Quaker mathematician J. W. Graham. His progress was rapid, winning him several scholarships and he graduated with a BSc in physics with First Class Honours in 1902.
Based on his performance at Owens College, he was awarded a scholarship to
Trinity College, Cambridge
Trinity College is a constituent college of the University of Cambridge. Founded in 1546 by King Henry VIII, Trinity is one of the largest Cambridge colleges, with the largest financial endowment of any college at either Cambridge or Oxford. ...
, in 1902. His tutor at Cambridge was
Robert Alfred Herman and in 1904 Eddington became the first ever second-year student to be placed as
Senior Wrangler. After receiving his M.A. in 1905, he began research on
thermionic emission in the
Cavendish Laboratory
The Cavendish Laboratory is the Department of Physics at the University of Cambridge, and is part of the School of Physical Sciences. The laboratory was opened in 1874 on the New Museums Site as a laboratory for experimental physics and is named ...
. This did not go well, and meanwhile he spent time teaching mathematics to first year engineering students. This hiatus was brief. Through a recommendation by
E. T. Whittaker, his senior colleague at Trinity College, he secured a position at the Royal Observatory in Greenwich where he was to embark on his career in astronomy, a career whose seeds had been sown even as a young child when he would often "try to count the stars".
Astronomy
In January 1906, Eddington was nominated to the post of chief assistant to the
Astronomer Royal at the
Royal Greenwich Observatory
The Royal Observatory, Greenwich (ROG; known as the Old Royal Observatory from 1957 to 1998, when the working Royal Greenwich Observatory, RGO, temporarily moved south from Greenwich to Herstmonceux) is an observatory situated on a hill in ...
. He left Cambridge for Greenwich the following month. He was put to work on a detailed analysis of the
parallax
Parallax is a displacement or difference in the apparent position of an object viewed along two different lines of sight and is measured by the angle or semi-angle of inclination between those two lines. Due to foreshortening, nearby object ...
of
433 Eros
Eros (minor planet designation: (433) Eros), provisional designation is a stony asteroid of the Amor group and the first discovered and second-largest near-Earth object with an elongated shape and a mean diameter of approximately . Vis ...
on
photographic plate
Photographic plates preceded photographic film as a capture medium in photography, and were still used in some communities up until the late 20th century. The light-sensitive emulsion of silver salts was coated on a glass plate, typically thinn ...
s that had started in 1900. He developed a new statistical method based on the apparent drift of two background stars, winning him the
Smith's Prize
The Smith's Prize was the name of each of two prizes awarded annually to two research students in mathematics and theoretical physics at the University of Cambridge from 1769. Following the reorganization in 1998, they are now awarded under the n ...
in 1907. The prize won him a fellowship of Trinity College, Cambridge. In December 1912
George Darwin, son of
Charles Darwin
Charles Robert Darwin ( ; 12 February 1809 – 19 April 1882) was an English naturalist, geologist, and biologist, widely known for his contributions to evolutionary biology. His proposition that all species of life have descended ...
, died suddenly and Eddington was promoted to his chair as the
Plumian Professor of Astronomy and Experimental Philosophy
The Plumian chair of Astronomy and Experimental Philosophy is one of the major professorships in Astronomy at Cambridge University, alongside the Lowndean Professorship (which is now mainly held by mathematicians). The chair is currently held at t ...
in early 1913. Later that year,
Robert Ball, holder of the theoretical
Lowndean chair also died, and Eddington was named the director of the entire
Cambridge Observatory
Cambridge Observatory is an astronomical observatory at the University of Cambridge in the East of England. It was established in 1823 and is now part of the site of the Institute of Astronomy. The old Observatory building houses the Institute ...
the next year. In May 1914 he was elected a
fellow of the Royal Society
Fellowship of the Royal Society (FRS, ForMemRS and HonFRS) is an award granted by the judges of the Royal Society of London to individuals who have made a "substantial contribution to the improvement of natural knowledge, including mathemati ...
: he was awarded the
Royal Medal
The Royal Medal, also known as The Queen's Medal and The King's Medal (depending on the gender of the monarch at the time of the award), is a silver-gilt medal, of which three are awarded each year by the Royal Society, two for "the most important ...
in 1928 and delivered the
Bakerian Lecture
The Bakerian Medal is one of the premier medals of the Royal Society that recognizes exceptional and outstanding science. It comes with a medal award and a prize lecture. The medalist is required to give a lecture on any topic related to physical ...
in 1926.
Eddington also investigated the interior of
star
A star is an astronomical object comprising a luminous spheroid of plasma (physics), plasma held together by its gravity. The List of nearest stars and brown dwarfs, nearest star to Earth is the Sun. Many other stars are visible to the naked ...
s through theory, and developed the first true understanding of stellar processes. He began this in 1916 with investigations of possible physical explanations for
Cepheid variable stars. He began by extending
Karl Schwarzschild
Karl Schwarzschild (; 9 October 1873 – 11 May 1916) was a German physicist and astronomer.
Schwarzschild provided the first exact solution to the Einstein field equations of general relativity, for the limited case of a single spherical non-r ...
's earlier work on radiation pressure in
Emden polytropic models. These models treated a star as a sphere of gas held up against gravity by internal thermal pressure, and one of Eddington's chief additions was to show that radiation pressure was necessary to prevent collapse of the sphere. He developed his model despite knowingly lacking firm foundations for understanding opacity and energy generation in the stellar interior. However, his results allowed for calculation of temperature,
density
Density (volumetric mass density or specific mass) is the substance's mass per unit of volume. The symbol most often used for density is ''ρ'' (the lower case Greek letter rho), although the Latin letter ''D'' can also be used. Mathematicall ...
and
pressure
Pressure (symbol: ''p'' or ''P'') is the force applied perpendicular to the surface of an object per unit area over which that force is distributed. Gauge pressure (also spelled ''gage'' pressure)The preferred spelling varies by country a ...
at all points inside a star (thermodynamic
anisotropy), and Eddington argued that his theory was so useful for further astrophysical investigation that it should be retained despite not being based on completely accepted physics.
James Jeans contributed the important suggestion that stellar matter would certainly be
ionized, but that was the end of any collaboration between the pair, who became famous for their lively debates.
Eddington defended his method by pointing to the utility of his results, particularly his important
mass–luminosity relation In astrophysics, the mass–luminosity relation is an equation giving the relationship between a star's mass and its luminosity, first noted by Jakob Karl Ernst Halm. The relationship is represented by the equation:
:\frac = \left(\frac\right)^a
wh ...
. This had the unexpected result of showing that virtually all stars, including giants and dwarfs, behaved as
ideal gases. In the process of developing his stellar models, he sought to overturn current thinking about the sources of stellar energy. Jeans and others defended the
Kelvin–Helmholtz mechanism, which was based on classical mechanics, while Eddington speculated broadly about the qualitative and quantitative consequences of possible proton–electron annihilation and nuclear fusion processes.
Around 1920, he anticipated the discovery and mechanism of nuclear fusion processes in stars, in his paper "The Internal Constitution of the Stars".
[ At that time, the source of stellar energy was a complete mystery; Eddington correctly speculated that the source was fusion of hydrogen into helium, liberating enormous energy according to Einstein's equation . This was a particularly remarkable development since at that time fusion and thermonuclear energy, and even the fact that stars are largely composed of ]hydrogen
Hydrogen is the chemical element with the symbol H and atomic number 1. Hydrogen is the lightest element. At standard conditions hydrogen is a gas of diatomic molecules having the formula . It is colorless, odorless, tasteless, non-to ...
(see metallicity
In astronomy, metallicity is the abundance of elements present in an object that are heavier than hydrogen and helium. Most of the normal physical matter in the Universe is either hydrogen or helium, and astronomers use the word ''"metals"'' as ...
), had not yet been discovered. Eddington's paper, based on knowledge at the time, reasoned that:
:# The leading theory of stellar energy, the contraction hypothesis, should cause stars' rotation to visibly speed up due to conservation of angular momentum
In physics, angular momentum (rarely, moment of momentum or rotational momentum) is the rotational analog of linear momentum. It is an important physical quantity because it is a conserved quantity—the total angular momentum of a closed sy ...
. But observations of Cepheid variable stars showed this was not happening.
:# The only other known plausible source of energy was conversion of matter to energy; Einstein had shown some years earlier that a small amount of matter was equivalent to a large amount of energy.
:# Francis Aston had also recently shown that the mass of a helium
Helium (from el, ἥλιος, helios, lit=sun) is a chemical element with the symbol He and atomic number 2. It is a colorless, odorless, tasteless, non-toxic, inert, monatomic gas and the first in the noble gas group in the periodic ta ...
atom was about 0.8% less than the mass of the four hydrogen atoms which would, combined, form a helium atom, suggesting that if such a combination could happen, it would release considerable energy as a byproduct.
:# If a star contained just 5% of fusible hydrogen, it would suffice to explain how stars got their energy. (We now know that most "ordinary" stars contain far more than 5% hydrogen.)
:# Further elements might also be fused, and other scientists had speculated that stars were the "crucible" in which light elements combined to create heavy elements, but without more accurate measurements of their atomic mass
The atomic mass (''m''a or ''m'') is the mass of an atom. Although the SI unit of mass is the kilogram (symbol: kg), atomic mass is often expressed in the non-SI unit dalton (symbol: Da) – equivalently, unified atomic mass unit (u). 1&n ...
es nothing more could be said at the time.
All of these speculations were proven correct in the following decades.
With these assumptions, he demonstrated that the interior temperature of stars must be millions of degrees. In 1924, he discovered the mass–luminosity relation In astrophysics, the mass–luminosity relation is an equation giving the relationship between a star's mass and its luminosity, first noted by Jakob Karl Ernst Halm. The relationship is represented by the equation:
:\frac = \left(\frac\right)^a
wh ...
for stars (see Lecchini in '). Despite some disagreement, Eddington's models were eventually accepted as a powerful tool for further investigation, particularly in issues of stellar evolution. The confirmation of his estimated stellar diameters by Michelson in 1920 proved crucial in convincing astronomers unused to Eddington's intuitive, exploratory style. Eddington's theory appeared in mature form in 1926 as ''The Internal Constitution of the Stars'', which became an important text for training an entire generation of astrophysicists.
Eddington's work in astrophysics in the late 1920s and the 1930s continued his work in stellar structure, and precipitated further clashes with Jeans and Edward Arthur Milne. An important topic was the extension of his models to take advantage of developments in quantum physics
Quantum mechanics is a fundamental theory in physics that provides a description of the physical properties of nature at the scale of atoms and subatomic particles. It is the foundation of all quantum physics including quantum chemistry, qua ...
, including the use of degeneracy physics in describing dwarf stars.
Dispute with Chandrasekhar on existence of black holes
The topic of extension of his models precipitated his dispute with Subrahmanyan Chandrasekhar
Subrahmanyan Chandrasekhar (; ) (19 October 1910 – 21 August 1995) was an Indian-American theoretical physicist who spent his professional life in the United States. He shared the 1983 Nobel Prize for Physics with William A. Fowler for " ...
, who was then a student at Cambridge. Chandrasekhar's work presaged the discovery of black hole
A black hole is a region of spacetime where gravity is so strong that nothing, including light or other electromagnetic waves, has enough energy to escape it. The theory of general relativity predicts that a sufficiently compact mass can def ...
s, which at the time seemed so absurdly non-physical that Eddington refused to believe that Chandrasekhar's purely mathematical derivation had consequences for the real world. Eddington was wrong and his motivation is controversial. Chandrasekhar's narrative of this incident, in which his work is harshly rejected, portrays Eddington as rather cruel and dogmatic. Chandra benefited from his friendship with Eddington. It was Eddington and Milne who put up Chandra's name for the fellowship for the Royal Society which Chandra obtained. An FRS meant he was at the Cambridge high-table with all the luminaries and a very comfortable endowment for research. Eddington's criticism seems to have been based partly on a suspicion that a purely mathematical derivation from relativity theory was not enough to explain the seemingly daunting physical paradoxes that were inherent to degenerate stars, but to have "raised irrelevant objections" in addition, as Thanu Padmanabhan
Thanu Padmanabhan (10 March 1957 – 17 September 2021) was an Indian theoretical physicist and cosmologist whose research spanned a wide variety of topics in gravitation, structure formation in the universe and quantum gravity. He published ...
puts it.
Relativity
During World War I
World War I (28 July 1914 11 November 1918), often abbreviated as WWI, was List of wars and anthropogenic disasters by death toll, one of the deadliest global conflicts in history. Belligerents included much of Europe, the Russian Empire, ...
, Eddington was secretary of the Royal Astronomical Society
(Whatever shines should be observed)
, predecessor =
, successor =
, formation =
, founder =
, extinction =
, merger =
, merged =
, type = NG ...
, which meant he was the first to receive a series of letters and papers from Willem de Sitter regarding Einstein's theory of general relativity. Eddington was fortunate in being not only one of the few astronomers with the mathematical skills to understand general relativity, but owing to his internationalist and pacifist views inspired by his Quaker religious beliefs, one of the few at the time who was still interested in pursuing a theory developed by a German physicist. He quickly became the chief supporter and expositor of relativity in Britain. He and Astronomer Royal Frank Watson Dyson organized two expeditions to observe a solar eclipse in 1919 to make the first empirical test of Einstein
Albert Einstein ( ; ; 14 March 1879 – 18 April 1955) was a German-born Theoretical physics, theoretical physicist, widely acknowledged to be one of the greatest and most influential physicists of all time. Einstein is best known for d ...
's theory: the measurement of the deflection of light by the sun's gravitational field. In fact, Dyson's argument for the indispensability of Eddington's expertise in this test was what prevented Eddington from eventually having to enter military service.
When conscription was introduced in Britain on 2 March 1916, Eddington intended to apply for an exemption as a conscientious objector
A conscientious objector (often shortened to conchie) is an "individual who has claimed the right to refuse to perform military service" on the grounds of freedom of thought, conscience, or religion. The term has also been extended to objec ...
. Cambridge University authorities instead requested and were granted an exemption on the ground of Eddington's work being of national interest. In 1918, this was appealed against by the Ministry of National Service. Before the appeal tribunal in June, Eddington claimed conscientious objector status, which was not recognized and would have ended his exemption in August 1918. A further two hearings took place in June and July, respectively. Eddington's personal statement at the June hearing about his objection to war based on religious grounds is on record. The Astronomer Royal, Sir Frank Dyson, supported Eddington at the July hearing with a written statement, emphasising Eddington's essential role in the solar eclipse
A solar eclipse occurs when the Moon passes between Earth and the Sun, thereby obscuring the view of the Sun from a small part of the Earth, totally or partially. Such an alignment occurs during an eclipse season, approximately every six mon ...
expedition to Príncipe
Príncipe is the smaller, northern major island of the country of São Tomé and Príncipe lying off the west coast of Africa in the Gulf of Guinea. It has an area of (including offshore islets) and a population of 7,324 at the 2012 Census; in May 1919. Eddington made clear his willingness to serve in the Friends' Ambulance Unit, under the jurisdiction of the British Red Cross
The International Red Cross and Red Crescent Movement is a Humanitarianism, humanitarian movement with approximately 97 million Volunteering, volunteers, members and staff worldwide. It was founded to protect human life and health, to ensure re ...
, or as a harvest labourer. However, the tribunal's decision to grant a further twelve months' exemption from military service was on condition of Eddington continuing his astronomy work, in particular in preparation for the Príncipe expedition. The war ended before the end of his exemption.
After the war, Eddington travelled to the island of Príncipe off the west coast of Africa to watch the solar eclipse of 29 May 1919
A total solar eclipse occurred on Thursday, May 29, 1919. With the duration of totality at maximum eclipse of 6 minutes 50.75 seconds, it was the longest solar eclipse since May 27, 1416. A longer total solar eclipse would later occur on June 8 ...
. During the eclipse, he took pictures of the stars (several stars in the Hyades cluster include Kappa Tauri of the constellation Taurus) in the region around the Sun. According to the theory of general relativity
General relativity, also known as the general theory of relativity and Einstein's theory of gravity, is the geometric theory of gravitation published by Albert Einstein in 1915 and is the current description of gravitation in modern physics ...
, stars with light rays that passed near the Sun would appear to have been slightly shifted because their light had been curved by its gravitational field. This effect is noticeable only during eclipses, since otherwise the Sun's brightness obscures the affected stars. Eddington showed that Newtonian gravitation could be interpreted to predict half the shift predicted by Einstein.
Eddington's observations published the next year allegedly confirmed Einstein's theory, and were hailed at the time as evidence of general relativity over the Newtonian model. The news was reported in newspapers all over the world as a major story. Afterward, Eddington embarked on a campaign to popularize relativity and the expedition as landmarks both in scientific development and international scientific relations.
It has been claimed that Eddington's observations were of poor quality, and he had unjustly discounted simultaneous observations at Sobral, Brazil, which appeared closer to the Newtonian model, but a 1979 re-analysis with modern measuring equipment and contemporary software validated Eddington's results and conclusions. The quality of the 1919 results was indeed poor compared to later observations, but was sufficient to persuade contemporary astronomers. The rejection of the results from the Brazil expedition was due to a defect in the telescopes used which, again, was completely accepted and well understood by contemporary astronomers.
Throughout this period, Eddington lectured on relativity, and was particularly well known for his ability to explain the concepts in lay terms as well as scientific. He collected many of these into the ''Mathematical Theory of Relativity'' in 1923, which Albert Einstein
Albert Einstein ( ; ; 14 March 1879 – 18 April 1955) was a German-born theoretical physicist, widely acknowledged to be one of the greatest and most influential physicists of all time. Einstein is best known for developing the theor ...
suggested was "the finest presentation of the subject in any language." He was an early advocate of Einstein's general relativity, and an interesting anecdote well illustrates his humour and personal intellectual investment: Ludwik Silberstein
Ludwik Silberstein (1872 – 1948) was a Polish-American physicist who helped make special relativity and general relativity staples of university coursework. His textbook '' The Theory of Relativity'' was published by Macmillan in 1914 with a ...
, a physicist who thought of himself as an expert on relativity, approached Eddington at the Royal Society
The Royal Society, formally The Royal Society of London for Improving Natural Knowledge, is a learned society and the United Kingdom's national academy of sciences. The society fulfils a number of roles: promoting science and its benefits, re ...
's (6 November) 1919 meeting where he had defended Einstein's relativity with his Brazil-Príncipe solar eclipse calculations with some degree of scepticism, and ruefully charged Arthur as one who claimed to be one of three men who actually understood the theory (Silberstein, of course, was including himself and Einstein as the other). When Eddington refrained from replying, he insisted Arthur not be "so shy", whereupon Eddington replied, "Oh, no! I was wondering who the third one might be!"[As related by Eddington to Chandrasekhar and quoted in Walter Isaacson "Einstein: His Life and Universe", p. 262]
Cosmology
Eddington was also heavily involved with the development of the first generation of general relativistic cosmological models. He had been investigating the instability of the Einstein universe when he learned of both Lemaître's 1927 paper postulating an expanding or contracting universe and Hubble's work on the recession of the spiral nebulae. He felt the cosmological constant must have played the crucial role in the universe's evolution from an Einsteinian steady state to its current expanding state, and most of his cosmological investigations focused on the constant's significance and characteristics. In ''The Mathematical Theory of Relativity,'' Eddington interpreted the cosmological constant to mean that the universe is "self-gauging".
Fundamental theory and the Eddington number
During the 1920s until his death, Eddington increasingly concentrated on what he called " fundamental theory" which was intended to be a unification of quantum theory, relativity, cosmology, and gravitation
In physics, gravity () is a fundamental interaction which causes mutual attraction between all things with mass or energy. Gravity is, by far, the weakest of the four fundamental interactions, approximately 1038 times weaker than the stron ...
. At first he progressed along "traditional" lines, but turned increasingly to an almost numerological
Numerology (also known as arithmancy) is the belief in an occult, divine or mystical relationship between a number and one or more coinciding events. It is also the study of the numerical value, via an alphanumeric system, of the letters in w ...
analysis of the dimensionless ratios of fundamental constants.
His basic approach was to combine several fundamental constants in order to produce a dimensionless number. In many cases these would result in numbers close to 1040, its square, or its square root. He was convinced that the mass of the proton
A proton is a stable subatomic particle, symbol , H+, or 1H+ with a positive electric charge of +1 ''e'' elementary charge. Its mass is slightly less than that of a neutron and 1,836 times the mass of an electron (the proton–electron mass ...
and the charge of the electron
The electron ( or ) is a subatomic particle with a negative one elementary electric charge. Electrons belong to the first generation of the lepton particle family,
and are generally thought to be elementary particles because they have n ...
were a "natural and complete specification for constructing a Universe" and that their values were not accidental. One of the discoverers of quantum mechanics, Paul Dirac
Paul Adrien Maurice Dirac (; 8 August 1902 – 20 October 1984) was an English theoretical physicist who is regarded as one of the most significant physicists of the 20th century. He was the Lucasian Professor of Mathematics at the Univer ...
, also pursued this line of investigation, which has become known as the Dirac large numbers hypothesis.
A somewhat damaging statement in his defence of these concepts involved the fine-structure constant, ''α''. At the time it was measured to be very close to 1/136, and he argued that the value should in fact be exactly 1/136 for epistemological reasons. Later measurements placed the value much closer to 1/137, at which point he switched his line of reasoning to argue that one more should be added to the degrees of freedom
Degrees of freedom (often abbreviated df or DOF) refers to the number of independent variables or parameters of a thermodynamic system. In various scientific fields, the word "freedom" is used to describe the limits to which physical movement or ...
, so that the value should in fact be exactly 1/137, the Eddington number. Wags at the time started calling him "Arthur Adding-one". This change of stance detracted from Eddington's credibility in the physics community. The current CODATA value is 1/
Eddington believed he had identified an algebraic basis for fundamental physics, which he termed "E-numbers" (representing a certain group – a Clifford algebra
In mathematics, a Clifford algebra is an algebra generated by a vector space with a quadratic form, and is a unital associative algebra. As -algebras, they generalize the real numbers, complex numbers, quaternions and several other hyperco ...
). These in effect incorporated spacetime
In physics, spacetime is a mathematical model that combines the three dimensions of space and one dimension of time into a single four-dimensional manifold. Spacetime diagrams can be used to visualize relativistic effects, such as why differ ...
into a higher-dimensional structure. While his theory has long been neglected by the general physics community, similar algebraic notions underlie many modern attempts at a grand unified theory. Moreover, Eddington's emphasis on the values of the fundamental constants, and specifically upon dimensionless numbers derived from them, is nowadays a central concern of physics. In particular, he predicted a number of hydrogen atoms in the Universe 136 × 2256 ≈ 1.57 1079, or equivalently the half of the total number of particles protons + electrons. He did not complete this line of research before his death in 1944; his book ''Fundamental Theory'' was published posthumously in 1948.
Eddington number for cycling
Eddington is credited with devising a measure of a cyclist's long-distance riding achievements. The Eddington number in the context of cycling is defined as the maximum number E such that the cyclist has cycled at least E miles on at least E days.
For example, an Eddington number of 70 would imply that the cyclist has cycled at least 70 miles in a day on at least 70 occasions. Achieving a high Eddington number is difficult since moving from, say, 70 to 75 will (probably) require more than five new long distance rides, since any rides shorter than 75 miles will no longer be included in the reckoning. Eddington's own life-time E-number was 84.
The Eddington number for cycling is analogous to the ''h''-index that quantifies both the actual scientific productivity and the apparent scientific impact of a scientist.[
]
Philosophy
Idealism
Eddington wrote in his book ''The Nature of the Physical World'' that "The stuff of the world is mind-stuff."
The idealist
In philosophy, the term idealism identifies and describes metaphysical perspectives which assert that reality is indistinguishable and inseparable from perception and understanding; that reality is a mental construct closely connected to ...
conclusion was not integral to his epistemology but was based on two main arguments.
The first derives directly from current physical theory. Briefly, mechanical theories of the ether and of the behaviour of fundamental particles have been discarded in both relativity and quantum physics. From this, Eddington inferred that a materialistic metaphysics was outmoded and that, in consequence, since the disjunction of materialism or idealism are assumed to be exhaustive, an idealistic metaphysics is required. The second, and more interesting argument, was based on Eddington's epistemology, and may be regarded as consisting of two parts. First, all we know of the objective world is its structure, and the structure of the objective world is precisely mirrored in our own consciousness. We therefore have no reason to doubt that the objective world too is "mind-stuff". Dualistic metaphysics, then, cannot be evidentially supported.
But, second, not only can we not know that the objective world is nonmentalistic, we also cannot intelligibly suppose that it could be material. To conceive of a dualism entails attributing material properties to the objective world. However, this presupposes that we could observe that the objective world has material properties. But this is absurd, for whatever is observed must ultimately be the content of our own consciousness, and consequently, nonmaterial.
Ian Barbour
Ian Graeme Barbour (1923–2013) was an American scholar on the relationship between science and religion. According to the Public Broadcasting Service his mid-1960s ''Issues in Science and Religion'' "has been credited with literally creating t ...
, in his book ''Issues in Science and Religion'' (1966), p. 133, cites Eddington's ''The Nature of the Physical World'' (1928) for a text that argues the Heisenberg Uncertainty Principles provides a scientific basis for "the defense of the idea of human freedom" and his ''Science and the Unseen World'' (1929) for support of philosophical idealism
In philosophy, the term idealism identifies and describes metaphysical perspectives which assert that reality is indistinguishable and inseparable from perception and understanding; that reality is a mental construct closely connected to ide ...
"the thesis that reality is basically mental".
Charles De Koninck
Charles De Koninck (29 July 1906 – 13 February 1965) was a Belgian-Canadian Thomist philosopher and theologian. As director of the Department of Philosophy at the Université Laval in Quebec, he influenced Catholic philosophy in French Canada a ...
points out that Eddington believed in objective reality existing apart from our minds, but was using the phrase "mind-stuff" to highlight the inherent intelligibility of the world: that our minds and the physical world are made of the same "stuff" and that our minds are the inescapable connection to the world. As De Koninck quotes Eddington,
Indeterminism
Against Albert Einstein
Albert Einstein ( ; ; 14 March 1879 – 18 April 1955) was a German-born theoretical physicist, widely acknowledged to be one of the greatest and most influential physicists of all time. Einstein is best known for developing the theor ...
and others who advocated determinism
Determinism is a philosophical view, where all events are determined completely by previously existing causes. Deterministic theories throughout the history of philosophy have developed from diverse and sometimes overlapping motives and cons ...
, indeterminism—championed by Eddington—says that a physical object has an ontologically undetermined component that is not due to the epistemological
Epistemology (; ), or the theory of knowledge, is the branch of philosophy concerned with knowledge. Epistemology is considered a major subfield of philosophy, along with other major subfields such as ethics, logic, and metaphysics.
Episte ...
limitations of physicists' understanding. The uncertainty principle
In quantum mechanics, the uncertainty principle (also known as Heisenberg's uncertainty principle) is any of a variety of mathematical inequalities asserting a fundamental limit to the accuracy with which the values for certain pairs of physic ...
in quantum mechanics
Quantum mechanics is a fundamental theory in physics that provides a description of the physical properties of nature at the scale of atoms and subatomic particles. It is the foundation of all quantum physics including quantum chemistry, ...
, then, would not necessarily be due to hidden variables but to an indeterminism in nature itself.
Popular and philosophical writings
Eddington wrote a parody of ''The Rubaiyat of Omar Khayyam
''Rubáiyát of Omar Khayyám'' is the title that Edward FitzGerald gave to his 1859 translation from Persian to English of a selection of quatrains (') attributed to Omar Khayyam (1048–1131), dubbed "the Astronomer-Poet of Persia".
Altho ...
'', recounting his 1919 solar eclipse experiment. It contained the following quatrain
A quatrain is a type of stanza, or a complete poem, consisting of four lines.
Existing in a variety of forms, the quatrain appears in poems from the poetic traditions of various ancient civilizations including Persia, Ancient India, Ancient Gree ...
:
During the 1920s and 30s, Eddington gave numerous lectures, interviews, and radio broadcasts on relativity, in addition to his textbook '' The Mathematical Theory of Relativity'', and later, quantum mechanics. Many of these were gathered into books, including ''The Nature of the Physical World'' and ''New Pathways in Science''. His use of literary allusions and humour helped make these difficult subjects more accessible.
Eddington's books and lectures were immensely popular with the public, not only because of his clear exposition, but also for his willingness to discuss the philosophical and religious implications of the new physics. He argued for a deeply rooted philosophical harmony between scientific investigation and religious mysticism, and also that the positivist nature of relativity and quantum physics provided new room for personal religious experience and free will. Unlike many other spiritual scientists, he rejected the idea that science could provide proof of religious propositions.
He is sometimes misunderstood as having promoted the infinite monkey theorem
The infinite monkey theorem states that a monkey hitting keys at random on a typewriter keyboard for an infinite amount of time will almost surely type any given text, such as the complete works of William Shakespeare. In fact, the monkey would ...
in his 1928 book ''The Nature of the Physical World'', with the phrase "If an army of monkeys were strumming on typewriters, they might write all the books in the British Museum
The British Museum is a public museum dedicated to human history, art and culture located in the Bloomsbury area of London. Its permanent collection of eight million works is among the largest and most comprehensive in existence. It docum ...
". It is clear from the context that Eddington is not suggesting that the probability of this happening is worthy of serious consideration. On the contrary, it was a rhetorical
Rhetoric () is the art of persuasion, which along with grammar and logic (or dialectic), is one of the three ancient arts of discourse. Rhetoric aims to study the techniques writers or speakers utilize to inform, persuade, or motivate parti ...
illustration of the fact that below certain levels of probability, the term ''improbable'' is functionally equivalent to ''impossible''.
His popular writings made him a household name in Great Britain between the world wars.
Death
Eddington died of cancer in the Evelyn Nursing Home, Cambridge, on 22 November 1944. He was unmarried. His body was cremated at Cambridge Crematorium (Cambridgeshire) on 27 November 1944; the cremated remains were buried in the grave of his mother in the Ascension Parish Burial Ground
The Ascension Parish Burial Ground, formerly known as the burial ground for the parish of St Giles and St Peter's, is a cemetery off Huntingdon Road in Cambridge, England. Many notable University of Cambridge academics are buried there, includ ...
in Cambridge.
Cambridge University's North West Cambridge Development has been named " Eddington" in his honour.
The actor Paul Eddington was a relative, mentioning in his autobiography (in light of his own weakness in mathematics) "what I then felt to be the misfortune" of being related to "one of the foremost physicists in the world".
Obituaries
Obituary 1
by Henry Norris Russell, ''Astrophysical Journal
''The Astrophysical Journal'', often abbreviated ''ApJ'' (pronounced "ap jay") in references and speech, is a peer-reviewed scientific journal of astrophysics and astronomy, established in 1895 by American astronomers George Ellery Hale and Jam ...
'' 101 (1943–46) 133
Obituary 2
by A. Vibert Douglas, '' Journal of the Royal Astronomical Society of Canada,'' 39 (1943–46) 1
Obituary 3
by Harold Spencer Jones and E. T. Whittaker, ''Monthly Notices of the Royal Astronomical Society
''Monthly Notices of the Royal Astronomical Society'' (MNRAS) is a peer-reviewed scientific journal covering research in astronomy and astrophysics. It has been in continuous existence since 1827 and publishes letters and papers reporting orig ...
'' 105 (1943–46) 68
Obituary 4
by Herbert Dingle, '' The Observatory'' 66 (1943–46) 1
* ''The Times
''The Times'' is a British daily national newspaper based in London. It began in 1785 under the title ''The Daily Universal Register'', adopting its current name on 1 January 1788. ''The Times'' and its sister paper '' The Sunday Times'' ( ...
'', Thursday, 23 November 1944; pg. 7; Issue 49998; col D: Obituary (unsigned) – Image of cutting available at
Honours
Awards
*Smith's Prize
The Smith's Prize was the name of each of two prizes awarded annually to two research students in mathematics and theoretical physics at the University of Cambridge from 1769. Following the reorganization in 1998, they are now awarded under the n ...
(1907)
* Bruce Medal of Astronomical Society of the Pacific (1924)
* Henry Draper Medal of the National Academy of Sciences
The National Academy of Sciences (NAS) is a United States nonprofit, non-governmental organization. NAS is part of the National Academies of Sciences, Engineering, and Medicine, along with the National Academy of Engineering (NAE) and the Nat ...
(1924)
* Gold Medal of the Royal Astronomical Society (1924)
*Foreign membership of the Royal Netherlands Academy of Arts and Sciences
The Royal Netherlands Academy of Arts and Sciences ( nl, Koninklijke Nederlandse Akademie van Wetenschappen, abbreviated: KNAW) is an organization dedicated to the advancement of science and literature in the Netherlands. The academy is housed ...
(1926)
*Prix Jules Janssen
The Prix Jules Janssen is the highest award of the Société astronomique de France (SAF), the French astronomical society.
This annual prize is given to a professional French astronomer or to an astronomer of another nationality in recognition ...
of the Société astronomique de France
The Société astronomique de France (SAF; ), the French astronomical society, is a non-profit association in the public interest organized under French law ( Association loi de 1901). Founded by astronomer Camille Flammarion in 1887, its purpose ...
(French Astronomical Society) (1928)
*Royal Medal
The Royal Medal, also known as The Queen's Medal and The King's Medal (depending on the gender of the monarch at the time of the award), is a silver-gilt medal, of which three are awarded each year by the Royal Society, two for "the most important ...
of the Royal Society
The Royal Society, formally The Royal Society of London for Improving Natural Knowledge, is a learned society and the United Kingdom's national academy of sciences. The society fulfils a number of roles: promoting science and its benefits, re ...
(1928)
*Knighthood
A knight is a person granted an honorary title of knighthood by a head of state (including the Pope) or representative for service to the monarch, the church or the country, especially in a military capacity. Knighthood finds origins in the ...
(1930)
*Order of Merit
The Order of Merit (french: link=no, Ordre du Mérite) is an order of merit for the Commonwealth realms, recognising distinguished service in the armed forces, science, art, literature, or for the promotion of culture. Established in 1902 by ...
(1938)
*Hon. Freeman of Kendal
Kendal, once Kirkby in Kendal or Kirkby Kendal, is a market town and civil parish in the South Lakeland district of Cumbria, England, south-east of Windermere and north of Lancaster. Historically in Westmorland, it lies within the dale of t ...
, 1930[''Who's who'' entry for A.S. Eddington.]
Named after him
*Lunar crater Eddington
*asteroid
An asteroid is a minor planet of the inner Solar System. Sizes and shapes of asteroids vary significantly, ranging from 1-meter rocks to a dwarf planet almost 1000 km in diameter; they are rocky, metallic or icy bodies with no atmosphere. ...
2761 Eddington
*Royal Astronomical Society
(Whatever shines should be observed)
, predecessor =
, successor =
, formation =
, founder =
, extinction =
, merger =
, merged =
, type = NG ...
's Eddington Medal
The Eddington Medal is awarded by the Royal Astronomical Society for investigations of outstanding merit in theoretical astrophysics. It is named after Sir Arthur Eddington. First awarded in 1953, the frequency of the prize has varied over the year ...
*Eddington mission The Eddington mission was a European Space Agency (ESA) project that planned to search for Earth-like planets, but was cancelled in 2003. It was named for the noted astronomer Arthur Eddington, who formulated much of the modern theory of stellar atm ...
, now cancelled
*Eddington Tower, halls of residence at the University of Essex
*Kendal, Eddington Astronomical Society, an amateur society based in his hometown of Kendal
Kendal, once Kirkby in Kendal or Kirkby Kendal, is a market town and civil parish in the South Lakeland district of Cumbria, England, south-east of Windermere and north of Lancaster. Historically in Westmorland, it lies within the dale of t ...
*Eddington, a house (group of students, used for in-school sports matches) of Kirkbie Kendal School
*Eddington, new suburb of North West Cambridge, opened in 2017
Service
*Gave the Swarthmore Lecture in 1929
*Chairman of the National Peace Council 1941–1943
*President of the International Astronomical Union; of the Physical Society of London, Physical Society, 1930–32; of the Royal Astronomical Society, 1921–23
*Romanes Lecturer, 1922
*Gifford lectures, Gifford Lecturer, 1927
In popular culture
* Eddington is a central figure in the short story "The Mathematician's Nightmare: The Vision of Professor Squarepunt" by Bertrand Russell, a work featured in ''The Mathematical Magpie'' by Clifton Fadiman.
* He was portrayed by David Tennant in the television film ''Einstein and Eddington'', a co-production of the BBC and HBO, broadcast in the United Kingdom on Saturday, 22 November 2008, on BBC2.
* His thoughts on humour and religious experience were quoted in the adventure game ''The Witness (2016 video game), The Witness'', a production of the Thelka, Inc., released on 26 January 2016.
* ''Time (magazine), Time'' placed him on the cover on 16 April 1934.
Publications
* 1914. ''Stellar Movements and the Structure of the Universe''. London: Macmillan.
* 1918.
Report on the relativity theory of gravitation
'. London, Fleetway Press, Ltd.
* 1920. ''s:Space Time and Gravitation, Space, Time and Gravitation: An Outline of the General Relativity Theory''. Cambridge University Press.
* 1923, 1952. The Mathematical Theory of Relativity. Cambridge University Press.
* 1925. ''The Domain of Physical Science''. 2005 reprint:
* 1926.
Stars and Atoms
'. Oxford: British Association.
* 1926. ''The Internal Constitution of Stars''. Cambridge University Press.
* 1928. ''The Nature of the Physical World''. MacMillan. 1935 replica edition: , University of Michigan 1981 edition: (1926–27 Gifford lectures)
* 1929.
Science and the Unseen World
'. US Macmillan, UK Allen & Unwin. 1980 Reprint Arden Library . 2004 US reprint – Whitefish, Montana : Kessinger Publications: . 2007 UK reprint London, Allen & Unwin (Swarthmore Lecture), with a new foreword by George Francis Rayner Ellis, George Ellis.
* 1930. ''Why I Believe in God: Science and Religion, as a Scientist Sees It''.
Arrow/scrollable preview.
* 1933. ''The Expanding Universe: Astronomy's 'Great Debate', 1900–1931''. Cambridge University Press.
* 1935. ''New Pathways in Science''. Cambridge University Press.
* 1936. ''Relativity Theory of Protons and Electrons''. Cambridge Univ. Press.
* 1939. ''Philosophy of Physical Science''. Cambridge University Press. (1938 Tarner lectures at Cambridge)
* 1946. ''Fundamental Theory''. Cambridge University Press.
See also
Astronomy
*Chandrasekhar limit
The Chandrasekhar limit () is the maximum mass of a stable white dwarf star. The currently accepted value of the Chandrasekhar limit is about ().
White dwarfs resist gravitational collapse primarily through electron degeneracy pressure, compar ...
*Eddington luminosity (also called the Eddington limit)
*Gravitational lens
*Outline of astronomy
*Stellar nucleosynthesis
*Timeline of stellar astronomy
*List of astronomers
Science
*Arrow of time
*Classical unified field theories
*Degenerate matter
*Dimensionless physical constant
* Dirac large numbers hypothesis (also called the Eddington–Dirac number)
* Eddington number
*Introduction to quantum mechanics
*Luminiferous aether
*Parameterized post-Newtonian formalism
*Special relativity
*Theory of everything (also called "final theory" or "ultimate theory")
*Timeline of gravitational physics and relativity
*List of experiments
People
*List of science and religion scholars
Other
*Infinite monkey theorem
*Numerology#Numerology in science, Numerology
*Ontic structural realism"Structural Realism"
entry by James Ladyman in the ''Stanford Encyclopedia of Philosophy''
References
Further reading
* Durham, Ian T., "Eddington & Uncertainty". Physics in Perspective (September – December). Arxiv, ''History of Physics''
*
* Lecchini, Stefano, "How Dwarfs Became Giants. The Discovery of the Mass–Luminosity Relation" ''Bern Studies in the History and Philosophy of Science'', pp. 224. (2007)
*
* Stanley, Matthew. "An Expedition to Heal the Wounds of War: The 1919 Eclipse Expedition and Eddington as Quaker Adventurer." ''Isis'' 94 (2003): 57–89.
* Stanley, Matthew. "So Simple a Thing as a Star: Jeans, Eddington, and the Growth of Astrophysical Phenomenology" in ''British Journal for the History of Science'', 2007, 40: 53–82.
*
External links
*
*
*
*
Trinity College Chapel
University of St Andrews, Scotland.
Arthur Stanley Eddington
The Bruce Medalists.
* Russell, Henry Norris, "
Review of The Internal Constitution of the Stars
by A.S. Eddington''". Ap.J. 67, 83 (1928).
Experiments of Sobral and Príncipe repeated in the space
project in proceeding in fórum astronomical.
*
* [http://www.allais.info/priorartdocs/eddington.htm Eddington books: ''The Nature of the Physical World'', ''The Philosophy of Physical Science'', ''Relativity Theory of Protons and Electrons'', and ''Fundamental Theory'']
{{DEFAULTSORT:Eddington, Arthur Stanley
1882 births
1944 deaths
Alumni of Trinity College, Cambridge
Alumni of the Victoria University of Manchester
British anti–World War I activists
British astrophysicists
British conscientious objectors
British Christian pacifists
Corresponding Members of the Russian Academy of Sciences (1917–1925)
Corresponding Members of the USSR Academy of Sciences
British Quakers
20th-century British astronomers
Fellows of Trinity College, Cambridge
Fellows of the Royal Astronomical Society
Fellows of the Royal Society
Foreign associates of the National Academy of Sciences
Knights Bachelor
Members of the Order of Merit
Members of the Royal Netherlands Academy of Arts and Sciences
People from Kendal
Presidents of the Physical Society
Presidents of the Royal Astronomical Society
Recipients of the Bruce Medal
Recipients of the Gold Medal of the Royal Astronomical Society
British relativity theorists
Royal Medal winners
Senior Wranglers
20th-century British physicists
Plumian Professors of Astronomy and Experimental Philosophy
Presidents of the International Astronomical Union