# Arthur Eddington : biography

### 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 Lemaitre’s 1927 paper postulating an expanding or contracting universe and Hubble’s work on the recession on 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

During the 1920s until his death, he increasingly concentrated on what he called "fundamental theory" which was intended to be a unification of quantum theory, relativity, cosmology, and gravitation. At first he progressed along "traditional" lines, but turned increasingly to an almost numerological 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 and the charge of the electron 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, also pursued this line of investigation, which has become known as the Dirac large numbers hypothesis, and some scientists even today believe it has something to it.

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, 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 is estimated at 1/137.035999679(94).

Eddington believed he had identified an algebraic basis for fundamental physics, which he termed "E-numbers" (representing a certain group – a Clifford algebra). These in effect incorporated spacetime 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.

He did not complete this line of research before his death in 1944, and his book entitled *Fundamental Theory* was published posthumously in 1948. Eddington died in Cambridge, England and is buried at the Parish of the Ascension Burial Ground in Cambridge, in the same grave as his mother Sarah Eddington 1852 – 1924, and his sister Winifred.

### Eddington number (cycling)

Eddington is credited with devising a measure of a cyclist’s long distance riding achievements. The Eddington Number in this context is defined as E, the number of days a cyclist has cycled more than E miles. For example an Eddington Number of 70 would imply that a cyclist has cycled more than 70 miles in a day on 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 best E-number is a very impressive 84.Physics World (Institute of Physics) July 2012 page 15

The construct of 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.