John Bell lived in Ireland for only 21 years, but throughout his life he remembered his Irish upbringing with fond memories, pride and gratitude.

Irish Physics and the Irish Tradition

Ireland has a very respectable tradition in physics, and particularly mathematical physics [1]. As early as the eighteenth century, Robert Boyle is usually given credit for establishing the experimental tradition in physics [2, 3]. Through the nineteenth century, luminaries such as William Rowan Hamilton [4], James MacCullagh [5], Thomas Andrews [6], George Francis FitzGerald [7, 8] and Joseph Larmor [9] all made very important contributions to the establishment of physics as an intellectual discipline in its own right, while it should not be forgotten that although the academic careers of George Gabriel Stokes [10],William Thomson [Lord Kelvin] [11] and John Tyndall [12] were spent in England or Scotland, all had Irish origins which they never forgot.

An important aspect of Irish mathematical physics in the nineteenth century was the existence of the so-called Irish tradition, which consisted of studying the wave theory of light and the ether. It was a tradition that was to be important for John Bell and it was to transcend what may be described as the most important event in nineteenth century physics – James Clerk Maxwell's theory of electromagnetism, and his conclusion that light was an electromagnetic wave [13]. The work of MacCullagh and Hamilton was performed in the 1830s and 1840s, while Maxwell's mature work was not to emerge until the 1860s.

MacCullagh improved the theory of Christian Huygens and Augustine Fresnel, being able first to derive the laws of reflection and refraction of light at the surfaces of crystals and metals, and then to write down equations for a light-bearing ether that justified his previous work. He was also able to handle the phenomenon of total internal reflection, and his model of the ether involved an effect that he called ‘rotational elasticity’, which was easy to describe mathematically but difficult to picture physically [14].

MacCullagh is probably not very well known even among physicists. One physicist, though, who was well aware of his achievements was Richard Feynman.