MacTutor
JOSEPH LARMOR was born at Magheragall in Co. Antrim on 1857 July 11. He graduated at Queen's College, Belfast, and proceeded to St. John's College, Cambridge. He was Senior Wrangler in 1880, the second place being taken by J. J. Thomson. He immediately became Professor of Natural Philosophy at Queen's College, Galway, and Fellow of St. John's College. He remained at Galway for five years, and then returned to St. John's College as College Lecturer. In 1903 he became Lucasian Professor on the death of Sir G. G. Stokes. He was knighted in 1909. He retired in 1932, but stayed in Cambridge for a year or two before going back to Northern Ireland, where he remained until his death on 1942 May 19, except for one brief visit to Cambridge.
His chief work, Æther and Matter, was published in 1900, and incorporated much of three mammoth papers in the Philosophical Transactions. A full account of this part of his work has been given by Sir Arthur Eddington in the Royal Society's Obituary Notices. It may be said to have marked the end of the various mechanical models of the ether that crowded nineteenth century physics. Larmor's model had a gyroscopic stability and enabled him to explain why light can show only transverse waves without longitudinal ones. It could be imitated by a model containing a sufficient number of gyrostats; it is not very clear from his writings whether he wanted it to be. The essential point was that he was able to assign a form to the energy that would give the right differential equations. He continually insisted on the necessity of reducing everything to the Principle of Least Action, which is out of fashion these days. But the principle has the great recommendation that when a form has once been chosen for the energy it is possible to see at a glance what is relevant; all irrelevant quantities automatically cancel. He made the outstanding discovery that a certain linear transformation of the coordinates and time leaves Maxwell's equations unaltered to the second order of small quantities, the transformation being that completed by Lorentz and shown to be exact. Larmor's contribution covers the whole of the experimental facts within the experimental uncertainty, and if verifiable prediction is a consideration in the assignment of proper names the transformation might well be called the Larmor-Lorentz transformation. From this result the theory of relativity sprang. Larmor was also the principal creator of classical electron theory – the electron was predicted long before Thomson observed it. In particular he gave the classical theory of the Zeeman effect.
Not many of his papers are directly astronomical or geophysical. He gave the general form of the correction of the period of the Eulerian nutation for the elasticity of the Earth, a further correction for the fluidity of the ocean, and the equations for the effects of changes of the products of inertia on the axis of instantaneous rotation. In two papers with Col. E. H. Hills (later Grove-Hills) he adopted the standpoint that the correct treatment of the problem of the variation of latitude is to use the observed displacements to calculate the changes of the direction of the axis of maximum moment of inertia with respect to the Earth's surface. In other words, instead of separating out the annual component directly from the observations by harmonic analysis, they treated all disturbances together, whether regular or irregular, by numerical differentiation of the observed displacements. The corresponding free vibration has a period of 14 months, and consequently a disturbing couple produces a much larger displacement if its period is a year than a couple of equal amplitude with a shorter period. Their treatment was equivalent to estimating the couples from the displacements, and therefore the annual terms were much less conspicuous in their results than in the original data, being comparable in magnitude with the irregular variations lasting a few months. The chief value of their work is that it showed the importance of this background of irregular variation, which is still not understood.
Larmor also offered two suggestions about the Kimura term in the variation of latitude, one that it is due to the annual melting of polar ice, the other that it is due to local refraction over the dome of the telescope.
One rather long paper, with N. Yamaga, deals with the analysis of sunspot frequencies, and maintains that a regular periodicity of 11.1 years dominated the whole record of 160 years except for a discrepant interval from 1776 to 1798. One fundamental paper showed that electric conductivity in the upper atmosphere would not account for the transmission of electric waves around the Earth, and appealed to the oscillations of free ions instead. These could produce much more reflexion with less damping.
His papers are difficult to read on account of diffuseness and prolixity of style. The same applied to his lectures, which suffered badly by comparison with those of Bromwich on similar subjects; though it is probable that Bromwich himself had been greatly inspired by Larmor, he was a far better expositor of Larmor's ideas than Larmor was. In conversation and at a committee he could be quite clear sometimes all too clear. He dearly loved an argument, and never forgot that he came from Northern Ireland. Of his handwriting it can only be said that few people could deal with it better than the compositor who rendered "it would be" as "."
He always maintained an interest in public affairs, resembling in this his greatest predecessor. He represented Cambridge University in Parliament from 1911 to 1922, and afterwards was a frequent correspondent to The Times. The present writer remembers vividly his plaintive query over the Food and Drugs Act about whether there was any scientific evidence that boric acid did anybody any harm.
He was secretary of the electors to the Isaac Newton Studentship for a long period, and in that capacity his indirect influence on astronomy was much greater than appeared through his personal contributions. He was always helpful to the young research worker, in spite of his underlying belief that real science came to an end with Lord Kelvin.
He was elected a Fellow of the Society on 1899 February 10.
HAROLD JEFFREYS.
His chief work, Æther and Matter, was published in 1900, and incorporated much of three mammoth papers in the Philosophical Transactions. A full account of this part of his work has been given by Sir Arthur Eddington in the Royal Society's Obituary Notices. It may be said to have marked the end of the various mechanical models of the ether that crowded nineteenth century physics. Larmor's model had a gyroscopic stability and enabled him to explain why light can show only transverse waves without longitudinal ones. It could be imitated by a model containing a sufficient number of gyrostats; it is not very clear from his writings whether he wanted it to be. The essential point was that he was able to assign a form to the energy that would give the right differential equations. He continually insisted on the necessity of reducing everything to the Principle of Least Action, which is out of fashion these days. But the principle has the great recommendation that when a form has once been chosen for the energy it is possible to see at a glance what is relevant; all irrelevant quantities automatically cancel. He made the outstanding discovery that a certain linear transformation of the coordinates and time leaves Maxwell's equations unaltered to the second order of small quantities, the transformation being that completed by Lorentz and shown to be exact. Larmor's contribution covers the whole of the experimental facts within the experimental uncertainty, and if verifiable prediction is a consideration in the assignment of proper names the transformation might well be called the Larmor-Lorentz transformation. From this result the theory of relativity sprang. Larmor was also the principal creator of classical electron theory – the electron was predicted long before Thomson observed it. In particular he gave the classical theory of the Zeeman effect.
Not many of his papers are directly astronomical or geophysical. He gave the general form of the correction of the period of the Eulerian nutation for the elasticity of the Earth, a further correction for the fluidity of the ocean, and the equations for the effects of changes of the products of inertia on the axis of instantaneous rotation. In two papers with Col. E. H. Hills (later Grove-Hills) he adopted the standpoint that the correct treatment of the problem of the variation of latitude is to use the observed displacements to calculate the changes of the direction of the axis of maximum moment of inertia with respect to the Earth's surface. In other words, instead of separating out the annual component directly from the observations by harmonic analysis, they treated all disturbances together, whether regular or irregular, by numerical differentiation of the observed displacements. The corresponding free vibration has a period of 14 months, and consequently a disturbing couple produces a much larger displacement if its period is a year than a couple of equal amplitude with a shorter period. Their treatment was equivalent to estimating the couples from the displacements, and therefore the annual terms were much less conspicuous in their results than in the original data, being comparable in magnitude with the irregular variations lasting a few months. The chief value of their work is that it showed the importance of this background of irregular variation, which is still not understood.
Larmor also offered two suggestions about the Kimura term in the variation of latitude, one that it is due to the annual melting of polar ice, the other that it is due to local refraction over the dome of the telescope.
One rather long paper, with N. Yamaga, deals with the analysis of sunspot frequencies, and maintains that a regular periodicity of 11.1 years dominated the whole record of 160 years except for a discrepant interval from 1776 to 1798. One fundamental paper showed that electric conductivity in the upper atmosphere would not account for the transmission of electric waves around the Earth, and appealed to the oscillations of free ions instead. These could produce much more reflexion with less damping.
His papers are difficult to read on account of diffuseness and prolixity of style. The same applied to his lectures, which suffered badly by comparison with those of Bromwich on similar subjects; though it is probable that Bromwich himself had been greatly inspired by Larmor, he was a far better expositor of Larmor's ideas than Larmor was. In conversation and at a committee he could be quite clear sometimes all too clear. He dearly loved an argument, and never forgot that he came from Northern Ireland. Of his handwriting it can only be said that few people could deal with it better than the compositor who rendered "it would be" as "."
He always maintained an interest in public affairs, resembling in this his greatest predecessor. He represented Cambridge University in Parliament from 1911 to 1922, and afterwards was a frequent correspondent to The Times. The present writer remembers vividly his plaintive query over the Food and Drugs Act about whether there was any scientific evidence that boric acid did anybody any harm.
He was secretary of the electors to the Isaac Newton Studentship for a long period, and in that capacity his indirect influence on astronomy was much greater than appeared through his personal contributions. He was always helpful to the young research worker, in spite of his underlying belief that real science came to an end with Lord Kelvin.
He was elected a Fellow of the Society on 1899 February 10.
HAROLD JEFFREYS.
Joseph Larmor's obituary appeared in Journal of the Royal Astronomical Society 103:2 (1943), 67-69.