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"[C]ontinued scientific progress is possible only if one appreciates the `difficulties that had to be circumvented in order to reach' the modern theories" Barbara Doran

Joseph Larmor (1857-1942) was a theoretical physicist and mathematician who began the twentieth century as the fourteenth holder of the Lucasian Chair. He attended Queens' College in Belfast where he obtained a B.A and an M.A. From there he moved to St. John's College, Cambridge, where he was senior wrangler and won the Smith's Prize. He was elected a fellow in 1880 and was appointed university lecturer in 1885. The years between were spent at Queens' College, Galway, as a professor of natural philosophy.¹

Larmor was to be the last of a breed of nineteenth century physicists whose work foreshadowed experiments and discoveries to come. His main contributions were presented in his book Aether and Matter, and in his major three part paper A Dynamical Theory of the Electric and Luminiferous Medium. He won the Adams Prize for an essay titled On the Theory of the Aberration of Light, which later became the book Aether and Matter .

The contemporaries of Larmor were such men as J.J. Thomson, William Thomson (Lord Kelvin), James Clerk Maxwell, Sir George Stokes and Hendrick Lorentz. All contributed great ideas toward the development of our understanding of the physical world. But it was Larmor's young followers who began the revolution in physics that marked the twentieth century.

Larmor took the Lucasian Chair in 1903, just two years before Einstein published his papers on light quantum and relativity. At the time Larmor stepped into the Chair, the atom was not yet understood: most of the nineteenth century had been filled with discoveries of light, rays, electromagnetism, and thermodynamics. He was active in the London Mathematical Society from his election in 1884, holding several offices: council member, 1887-1912; vice president 1890 and 1891; treasurer 1892-1914; and president 1914. In 1914 he was awarded the DeMorgan Medal by the Society. The Royal Society elected Larmor to membership in 1892 and he served as secretary from 1901 to 1912. The Royal Society awarded him the Royal Medal in 1915 and the Copley Medal in 1921. The Crown knighted Larmor in 1909. He served in Parliament as the representative of Cambridge from 1911 to 1922.² Larmor was active in college affairs, maintaining membership on the council of St. John's for many years.³

One of Larmor's achievements was as the driving force to get Ernest Rutherford into Cambridge after World War II. Rutherford had split the atom, demonstrating his genius and elevating his status among scientists. Larmor reasoned that since J.J. Thomson was stepping down as leader of the Cavendish Laboratory, Rutherford was the man to replace him. His efforts were successful, providing the Cavendish with a needed boost.⁴

Larmor's major work is in three papers published in a series, all with the title A dynamical theory of the electric and luminiferous medium ⁵ and in his book. Aether and Matter ⁶ Throughout Larmor's work, there is an underlying theme: the principle of least action. This is also known as Hamilton's principle , after William Hamilton (1805-1865), recognizing Hamilton's contributions in mechanics and optics utilizing this idea.⁷ . The principle basically states that a particle's motion over short time intervals will minimize the action integral.⁸

At the time, Larmor was held in high regard, having published many papers that made important contributions. The ether was still accepted and ideas such as electrons were not common. There was no real understanding of the makeup of matter and energy. He proposed that the electrical charge of an electron might be the measure of its mass. Today, electrons are measured in electron volts (eV), as are all particles.

" Larmor effected a new synthesis called the electron theory of matter and developed its radical implication regarding the nature of mass, the structure of the atom and its relation to radiation, the kinetic theory of heat (equipartition), and the electrodynamics of moving bodies."⁹ The mass of an electron is actually 0.511 MeV and the proton is 938.3 MeV, where MeV is Million electron volts.

The writings of Aristotle explained that the heavens were composed of the ether, also known as the quintessence. This ether had been postulated to explain the workings of the universe that surrounded the earth and was supposed to be some sort of medium inside of which the universe existed. The original debates in ancient times were over the nature of the ether, but the general agreement was that it existed. The ether was believed to be divided in spheres, naturally perfect, rotating without friction. No one, or at least very few, posed questions as to whether the spheres were hard or soft. The planets were regions of high density in the transparent ether. There were debates over earthly matter and heavenly matter, if one believed that the ether was a form of matter. The medieval period kept alive the belief in the ether since Aristotle's works were the basis for education. The only changes were in what was believed to be the character of the ether and the addition of a quantitative approach to its analysis.¹⁰

The world of science still believed in the ether until Larmor's time. The ether was thought to be the mechanism used to explain how light waves traveled. It could be considered in the same way as water which provides a medium for waves to travel. He worked hard to find a suitable theory of the ether, but he was unable to discover direct evidence of the motion of the earth through the ether. He presented a partial explanation which led to the theories that were part of Albert Einstein's Theory of Relativity. Larmor was one of the last to really believe in strict Newtonian mechanics. During his lifetime relativity and quantum mechanics took hold of physics.

Larmor's name is used in connection with the Larmor Precession, the Larmor Frequency, Larmor's Theorem and Larmor's Formula. The Larmor Precession is the phenomenon used to explain triplication and polarization of spectral lines discovered by Pietar Zeeman, with related theoretical work by H.A. Lorentz, when a very strong magnetic field was applied to sodium. Zeeman eventually won the Nobel Prize for his work. The Larmor Frequency is the result of the calculation omega =(e/2m) B. The omega is the angular momentum of an electron and the B is the magnetic field. Larmor showed that with several orbiting electrons, some orbits would be accelerated and some slowed down, and some would not be affected, ending up with a net effect of either zero or a very small amount. However, the spectral lines would be separate for the different speeds. This led Larmor to postulate the electrons as orbiting around some center, one first to do so and to have a theoretical and experimental basis for it.¹¹ Larmor's Theorem is an extension of this, omega =-(e/2m) B, that states for any charged particle with the same e/m ratio subject to electric and magnetic fields, the effect of the magnetic field can be negated a transformation of the frame of reference with this formula.¹² Larmor's Formula gives a way to calculate the power radiated(P) by an electron's acceleration in terms of charge (e), speed of light (c) and the acceleration (a). Although now, it must be viewed as not useful in terms of relativity, it still works at speeds less than close to the speed of light. (P= 2/3 e^2 a^2 c^3) is the actual formula. He is remembered for contributions to electrodynamics and electron theory.¹³ He made major contributions to electron theory and progress towards what is now known as the Lorentz transformations. Larmor was the first to propose an electrical theory of matter. Unfortunately for Larmor, Einstein published his papers on relativity and the development of quantum theory got under way. Both of these advances overshadowed his work. Furthermore, he rejected the direction of Einstein's work. In the 1920s the work of Larmor and his students came to a close.¹⁴

Larmor had chosen to build his electron theory, which was essentially in the correct direction, in the context of the ether, which was not the correct environment. The fundamental change was from the mechanical view of the ether to the electrical view of the ether. "[He] gradually made specific his conception that the electric charge interrupts the continuity and uniformity of the ether without destroying it."¹⁵ He kept his loyalty to the traditional idea of the ether rather than make a break with the past with the new knowledge he had developed. It was a situation similar to the early eighteenth century when British mathematicians continued to use Newton's method of notation in calculus. Blind loyalty in the face of new knowledge is a dangerous game, especially when competitors are not fettered by such constraints. Larmor stood on the doorstep of a new frontier, but chose not to cross it. Thus, he is remembered as the end of an era rather than the beginning.

When George Stokes and Lord Kelvin died, Larmor finished editing their works. He revised the works of Henry Cavendish that had originally been edited by James Clerk Maxwell. He also edited the works of James Thomson. Larmor wrote substantial obituaries of Josiah Gibbs (1905), George Stokes (1903), and Lord Kelvin (1908).

Footnotes

1. Dictionary of National Biography (London: Oxford University Press, 1882).
2. Dictionary of National Biography.
3. Dictionary of National Biography.
4. C. Brooke, 186.
5. Larmor 1894,1896,1898
6. Larmor 1900.
7. Andrew Warwick, "Frequency, theorem and formula: remembering Joseph Larmor in electromagnetic theory," Notes and Records of the Royal Society of London 47 (1992): 49-60.
8. Robert James, Mathematics Dictionary, 5th ed. (New York: Van Nostrand Reinhold, 1992), 194.
9. Doran i
10. David Lindberg, The Beginnings of Western Science (Chicago: University of Chicago, 1992), 250.
11. Warwick, 53.
12. Warwick 1993 53.
13. Charles Gillispie, Dictionary of Scientific Biography (New York: Charles Scribner's Sons, 1980), 39.
14. Warwick, 573.
15. Doran 354