George Johnstone Stoney
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George Johnstone Stoney (February 15, 1826 – July 5, 1911) was an Irish physicist famous for introducing the term electron in 1874.[1][2] He worked at the National University of Ireland, Galway.
Stoney was born on 15 February 1826 at Oak Park, near Birr, County Offaly, in the Irish midlands. He attended Trinity College, Dublin, graduating with a B.A. in 1848 and an M.A. in 1852. In 1848 he became an assistant to the Earl of Rosse at Birr Castle, County Offaly, where Rosse had built and operated the 'Leviathan', the world's largest telescope in its day.
In 1852, Stoney became Professor of Natural Philosophy at Queen's College Galway (now the National University of Ireland, Galway). In 1857, he moved to Dublin as Secretary of the Queen's University; he subsequently became superintendent of Civil Service Examinations in Ireland, a post he held until his retirement in 1893. In this year, he took up residence in London.
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[edit] Scientific Work
Stoney published seventy-five scientific papers in a variety of journals, making significant contributions to cosmic physics and to the theory of gases. In 1891, he proposed the term 'electron' to describe the fundamental unit of electrical charge, and his contributions to research in this area laid the foundations for the eventual discovery of the particle by J.J. Thomson in 1905. He was elected a Fellow of the Royal Society in 1861, and served as Vice-President of the Society for 1898-9.
Stoney's most important scientific work was the conception and calculation of the magnitude of the atom or particle of electricity, for which he coined the term "electron". He also estimated the number of molecules in a cubic millimetre of gas, at room temperature and pressure, from data obtained from the kinetic theory of gases.
[edit] The Stoney Scale
Contemporary physics has settled on the Planck scale as the most suitable scale for a unified theory. The Planck scale was however anticipated by George Stoney [Stoney G. On The Physical Units of Nature, Phil.Mag.11,381-391,1881]. Like Planck after him, Stoney realized that large-scale effects such as gravity and small-scale effects such as electromagnetism naturally imply an intermediate scale where physical differences might be rationalized. This intermediate scale comprises units of mass, length, time etc., yet mass is the cornerstone.
The Stoney mass 
(expressed in contemporary terms):
where kC is Coulomb's constant, e is the elementary charge and G is the gravitational constant, and where 
is the fine-structure constant and 
is the Planck mass.
Like the Planck scale, the Stoney scale functions as a symmetrical link between microcosmic and macrocosmic processes in general and yet it appears uniquely oriented towards the unification of electromagnetism and gravity . Thus for example whereas the Planck length is the mean square root of the reduced Compton wavelength and half the gravitational radius of any mass, the Stoney length is the mean square root of the 'electromagnetic radius' (see Classical electron radius) and half the gravitational radius of any mass:
where 
is the reduced Planck's constant and c is the speed of light. It should be noted however that these are only mathematical constructs since there must be some practical limit to how small a length can get. If the Stoney length is the minimum length then either a body's electromagnetic radius or its half gravitational radius is a physical impossibility, since one of these must be smaller than the Stoney length. If Planck length is the minimum then either a body's reduced Compton wavelength or its half gravitational radius is a physical impossibility since one of these must be smaller than the Planck length. Moreover, the Stoney length and Planck length cannot both be the minimum length.
According to contemporary convention, Planck scale is the scale of vacuum energy, below which space and time do not retain any physical significance. This prescription mandates a general neglect of the Stoney scale within the scientific community today. Previous to this mandate, Hermann Weyl made a notable attempt to construct a unified theory by associating a gravitational unit of charge with the Stoney length. Weyl's theory led to significant mathematical innovations but his theory is generally thought to lack physical significance [O'Raifeartaigh L. The Dawning of Gauge Theory, Princeton Uni Press, 1997][Gorelik G. 'Herman Weyl and Large Numbers in Relativistic Cosmology', Einstein Studies in Russia, Ed Balashov Y. and Vizgin V., Boston (Birkhaeuser)2002].
[edit] Later life
Stoney died on 5 July 1911 at his home in Notting Hill, London. After cremation, his ashes were buried in Dundrum, County Dublin.
[edit] Other
Craters on Mars and the Moon are named in his honour.
Stoney was the uncle of the physicist George FitzGerald, and distantly related to Alan Turing.
[edit] See also
[edit] References
- ^ Jammer, Max (1956). Concepts of Force - A Study of the Foundations of Dynamics. New York: Dover Publications, Inc.. ISBN 048640689X.
- ^ Stoney, G.J. (1881). "On the Physical Units of Nature." Phil. Mag. [5] 11, 384.
[edit] Publications
- Stoney, George Johnstone, "On a Supposed Proof of a Theorem in Wave-motion". Philosophical Magazine, 5(43), pp. 368-373 (1897).
[edit] Literature
- Alex Keller: The Infancy of Atomic Physics. Hercules in His Cradle, Oxford University 1983. ISBN 0-19-853904-5
[edit] External link
- Of the "Electron", or Atom of Electricity - by G. J. Stoney, Philosophical Magazine, Series 5, Volume 38, p. 418-420, October 1894
