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J. J. Thomson Quotes (1856-1940)
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About J. J. Thomson
Sir Joseph John Thomson, OM, FRS (18 December 1856 β 30 August 1940), often known as J. J. Thomson, was an English physicist and Nobel laureate in physics, credited with the discovery and identification of the electron, the discovery of the first subatomic particle, isotopes, and the invention of the mass spectrometer.
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βThe difficulties which would have to be overcome to make several of the preceding experiments conclusive are so great as to be almost insurmountable.β
βIf, in the very intense electric field in the neighbourhood of the cathode, the molecules of the gas are dissociated and are split up, not into the ordinary chemical atoms, but into these primordial atoms, which we shall for brevity call corpuscles; and if these corpuscles are charged with electricity and projected from the cathode by the electric field, they would behave exactly like the cathode rays.β
βAs the cathode rays carry a charge of negative electricity, are deflected by an electrostatic force as if they were negatively electrified, and are acted on by a magnetic force in just the way in which this force would act on a negatively electrified body moving along the path of these rays, I can see no escape from the conclusion that they are charges of negative electricity carried by particles of matter.β
βThe discovery by Monsieur and Madame Curie that a sample of radium gives out sufficient energy to melt half its weight of ice per hour has attracted attention to the question of the source from which the radium derives the energy necessary to maintain the radiation; this problem has been before us ever since the original discovery by Becquerel of the radiation from uranium.β
βThis example illustrates the differences in the effects which may be produced by research in pure or applied science. A research on the lines of applied science would doubtless have led to improvement and development of the older methodsβthe research in pure science has given us an entirely new and much more powerful method. In fact, research in applied science leads to reforms, research in pure science leads to revolutions, and revolutions, whether political or industrial, are exceedingly profitable things if you are on the winning side.β
βI have described at some length the application of Positive Rays to chemical analysis; one of the main reasons for writing this book was the hope that it might induce others, and especially chemists, to try this method of analysis. I feel sure that there are many problems in chemistry, which could be solved with far greater ease by this than any other method. The method is surprisingly sensitive β more so than even that of spectrum analysis, requires an infinitesimal amount of material, and does not require this to be specially purified; the technique is not difficult if appliances for producing high vacua are available.β
βWe see from Lenard's table that a cathode ray can travel through air at atmospheric pressure a distance of about half a centimetre before the brightness of the phosphorescence falls to about half its original value. Now the mean free path of the molecules of air at this pressure is about 10-5 cm., and if a molecule of air were projected it would lose half its momentum in a space comparable with the mean free path. Even if we suppose that it is not the same molecule that is carried, the effect of the obliquity of the collisions would reduce the momentum to half in a short multiple of that path. Thus, from Lenard's experiments on the absorption of the rays outside the tube, it follows on the hypothesis that the cathode rays are charged particles moving with high velocities, that the size of the carriers must be small compared with the dimensions of ordinary atoms or molecules. The assumption of a state of matter more finely subdivided than the atom of an element is a somewhat startling one; but a hypothesis that would involve somewhat similar consequencesβviz. that the so-called elements are compounds of some primordial elementβhas been put forward from time to time by various chemists.β
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J. J. Thomson on Electron
J. J. Thomson on Force field (physics)
βIf, in the very intense electric field in the neighbourhood of the cathode, the molecules of the gas are dissociated and are split up, not into the ordinary chemical atoms, but into these primordial atoms, which we shall for brevity call corpuscles; and if these corpuscles are charged with electricity and projected from the cathode by the electric field, they would behave exactly like the cathode rays.β
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J. J. Thomson on Chemistry
βI have described at some length the application of Positive Rays to chemical analysis; one of the main reasons for writing this book was the hope that it might induce others, and especially chemists, to try this method of analysis. I feel sure that there are many problems in chemistry, which could be solved with far greater ease by this than any other method. The method is surprisingly sensitive β more so than even that of spectrum analysis, requires an infinitesimal amount of material, and does not require this to be specially purified; the technique is not difficult if appliances for producing high vacua are available.β
J. J. Thomson on Poynting vector
βI have in my "Recent Researches on Electricity and Magnetism" calculated the amount of momentum at any point in the electric field, and have shown that if N is the number of Faraday tubes passing through a unit area drawn at right angles to the direction, B the magnetic induction, ΞΈ the angle between the induction and the Faraday tubes, then the momentum per unit volume is equal to N B sin ΞΈ, the direction of the momentum being at right angles to the magnetic induction and also to the Faraday tubes. Many of you will notice that the momentum is parallel to what is known as Poynting's vectorβthe vector whose direction gives the direction in which energy is flowing through the field.β
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J. J. Thomson on John Strutt, 3rd Baron Rayleigh
βThere are some great men of science whose charm consists in having said the first word on a subject, in having introduced some new idea which has proved fruitful; there are others whose charm consists perhaps in having said the last word on the subject, and who have reduced the subject to logical consistency and clearness. I think by temperament Lord Rayleigh belonged to the second group.β
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The Electrical World on J. J. Thomson
βCathode Rays... he adheres to the hypothesis that the rays are due to the violent projection of the negatively charged particles from the cathode. In another abstract from presumably the same lecture, he states that in the cathode discharge the matter is in something beyond the ordinary state and that the carriers of the discharge in a cathode ray are not atoms but something very much smaller; his conclusions are that the particles carrying the charge must be in a much more finely divided state than the ordinary molecule and possibly may be the primordial element; the numerical ration of the mass of the particle to the charge carried is about 1,100 times less than that deduced electrolytically for the hydrogen ion, showing that either the charge must be very great or the particle very small, and it is the latter which he thinks is the case.β
Dianna Preston on J. J. Thomson 3 quotes
βHis reluctance to pay for elaborate or expensive equipment, perhaps the result of an impoverished childhood, had established the legendary "sealing wax-and-string" tradition of the Cavendish, where everyday materials were ingeniously used to make and patch up experimental equipment, with sealing wax proving particularly useful for vacuum seals.β
Richard Reeves on J. J. Thomson 2 quotes
βNotes on Recent Researches in Electricity and Magnetism, published in 1883, had won him enough acclaim at the age of twenty-seven that he was named director of the [Cavendish] laboratory the next year.β
Edmund Taylor Whittaker on J. J. Thomson 2 quotes
βJ. J. Thomson, by a rotating-mirror method, succeeded in measuring the velocity of the cathode rays, finding it to be 1.9 x 107 cm./sec.; a value so much smaller than that of the velocity of light that it was scarcely possible to conceive of the rays as vibrations of the aether.β
About J. J. Thomson
Sir Joseph John Thomson, OM, FRS (18 December 1856 β 30 August 1940), often known as J. J. Thomson, was an English physicist and Nobel laureate in physics, credited with the discovery and identification of the electron, the discovery of the first subatomic particle, isotopes, and the invention of the mass spectrometer.