On a Possible Mode of Detecting a Motion of the Solar System through the Luminiferous Ether. In a Letter to Mr. D. P. Todd,’ pp. 109-110 in Proceedings of the Royal Society of London, Vol. XXX, No. 200, December 1879 – January 1880.

London: Harrison & Sons, 1880.

First edition, in the very rare original printed wrappers, of Maxwell’s last paper, “published posthumously in the Proceedings of the Royal Society, [which] concerned a means of measuring the speed of the Earth through the hypothetical aether, and was the inspiration for Michelson and Morley’s famous experiment. The null result of that experiment was to lead to the Special Theory of Relativity” (Longair, Maxwell’s Enduring Legacy, p. 71). “Maxwell’s words had stimulated Michelson to carry out one of the great experiments of physics” (Longair, CavMag, p. 13). “The paper was in fact by George Stokes, reporting a letter which Maxwell sent to Mr. D[avid] P[eck] Todd of the Nautical Almanac Office in Washington dated 19 March 1879. The main body of the letter concerns the use of accurate timing of the eclipses of Jupiter’s satellites as a means of measuring the speed of light plus the Earth’s motion through the ether. This required an accurate knowledge of the orbits of Jupiter’s satellites. Maxwell writes, ‘I have therefore taken the liberty of writing to you, as the matter is beyond the reach of anyone who has not made a special study of the satellites.’ But, more germane is the remark in an earlier paragraph. ‘... in the terrestrial methods of determining the velocity of light, the light comes back along the same path again, so that the velocity of the earth with respect to the ether would alter the time of the double passage by a quantity depending on the square of the ratio of the earth’s velocity to that of light, and this is quite too small to be observed’ … Albert Michelson recognised that, contrary to Maxwell’s assertion, very small path differences could be detected by optical interferometry. In his paper on the first version of the experiment of 1881 [‘The Relative Motion of the Earth and the Luminiferous Ether,’ American Journal of Science, 22, 120-129], Michelson states explicitly that: ‘The following is intended to show that, with a wave-length of yellow light as a standard, the quantity [the path difference between the light rays] − if it exists − is easily measurable” (ibid., p. 12). But Michelson made an error in his calculations in 1881 and realised that an improved version of the experiment was necessary; this he carried out with Morley in 1887 (‘On the Relative Motion of the Earth and the Luminiferous Ether,’ American Journal of Science, 34, 333-345). The offered paper was published simultaneously in the Royal Society’s Proceedings and in the journal Nature (Vol. 21, p. 315).

“Maxwell’s (1831-79) influence in suggesting the Michelson-Morley ether-drift experiment is widely acknowledged, but the story is a curiously tangled one. It originates in the problem of the aberration of starlight. During the course of a year the apparent positions of stars, as fixed by transit measurements, vary by ±20.5 arc-seconds. This effect was discovered in 1728 by [James] Bradley (1693-1762). He attributed it to the lateral motion of the telescope traveling at velocity v with the earth about the sun. On the corpuscular theory of light the motion causes a displacement of the image, while the particles travel from the objective to the focus, through an angular range v/c just equal to the observed displacement [c is the velocity of light]. An explanation of aberration on the wave theory of light is harder to come by. If the ether were a gas like the Earth’s atmosphere (as was first supposed), it would be carried along with the telescope and one scarcely would expect any displacement. [Thomas] Young (1773-1829) in 1804 therefore proposed the ether must pass between the atoms in the telescope wall “as freely perhaps as the wind passes through a grove of trees.” The idea had promise, but in working it out other phenomena needed to be considered, many of which further illustrate the difficulties of classical ethers …

“In 1859 [Hippolyte] Fizeau (1819-96) proved experimentally that the velocity of light in a moving column of water is greater downstream than upstream. A natural supposition is that the water drags the ether along with it. This contradicts Young’s hypothesis in its most primitive form; however, the modified velocity was not c + w but c + w(1 – 1/μ2), where μ is the refractive index of water [and w is the velocity of the water], and that tallied with a more sophisticated theory of aberration due to [Augustin-Jean] Fresnel (1788-1827). Fresnel held the conviction (not actually verified until 1871) that the aberration coefficient in a telescope full of water must remain unchanged, which on Young’s theory it does not. He was able to satisfy that requirement by combining Young’s hypothesis with the further assumption that refraction is due to condensation of the ether in ordinary matter, the ether density in a medium of refractive index μ being μ2 times its value in free space. With the excess ether carried along by matter one obtains the quoted formula, which in consequence is still known as the “Fresnel drag” term, though it stands on broader foundations, as [Joseph] Larmor (1857-1942) afterwards proved. Indeed Fresnel’s condensation hypothesis is logically inconsistent with another principle that became accepted in the 1820s, namely, that the ether, to convey transverse but not longitudinal waves, must be an incompressible solid. A dissatisfaction with Fresnel’s “startling assumptions” made [George] Stokes (1819-1903) in 1846 propose a radically new theory of aberration, treating the ether as a viscoelastic substance, like pitch or glass. For the rapid vibrations of light the ether acts as a solid, but for the slow motions of the solar system it resembles a viscous liquid, a portion of which is dragged along with each planetary body. A plausible circuital condition on the motion gives a deflection v/c for a beam of light approaching the earth, identical with the displacement that occurs inside the telescope in the other theories.

“Some time in 1862 or 1863 Maxwell read Fizeau’s paper and thought out an experiment to detect the ether wind. Since refraction is caused by differences in the velocity of light in different media, one might expect the Fresnel drag to modify the refraction of a glass prism moving through the ether. Maxwell calculated that the additional deflection in a 60° prism moving at the earth’s velocity would be 17 arc-seconds. He arranged a train of three prisms with a return mirror behind them in the manner of his portable “colour-box”, and set up what would now be called an autocollimator to look for the deflection, using a telescope with an illuminated eyepiece in which the image of the crosshair was refocused on itself after passing to and fro through the prism. The displacement from ether motion could be seen by mounting the apparatus on a turntable, where the effect would reverse on rotating through 180°, giving an overall deflection after the double passage of 2½ arc-minutes: easily measurable. Maxwell could detect nothing, so in April 1864 he sent Stokes a paper for the Royal Society concluding that “the result of the experiment is decidedly negative to the hypothesis about the motion of the ether in the form stated here.”

“Maxwell had blundered. Though he did not then know it, the French engineer [François] Arago (1786-1853) had done a crude version of the same experiment in 1810 (with errors too large for his result to have real significance), and Fresnel had based his theory on Arago’s negative result. Stokes knew all this, having written an article on the subject in 1845; he replied, pointing out Maxwell’s error, which had been to overlook the compensating change in density that occurs because the ether satisfies a continuity equation at the boundary. Maxwell withdrew the paper. He did give a description of the experiment three years later, with a corrected interpretation, in a letter to the astronomer William Huggins (1824-1910) … There the matter rested until the last year of Maxwell’s life. Then in his article “Ether” for the Encyclopaedia Britannica, he again reviewed the problem of motion through the ether. The only possible earth-based experiment was to measure variations in the velocity of light on a double journey between two mirrors. Maxwell concluded that the time differences in different directions, being of the order of v2/c2, would be too small to detect. He proposed another method from timing the eclipses of the moons of Jupiter, which he later described in more detail in a letter to the American astronomer D. P. Todd (1855-1939), published after his death in the Royal Society Proceedings and in Nature. His statements there about the difficulties of the earth-based experiment served as a challenge to the young Albert Michelson (1852-1931), who at once invented his famous interferometer to do it.

“The negative result of the experiment swung Michelson and everyone else behind Stokes’ theory of aberration. In 1885, however, [Hendrik] Lorentz (1853-1928) discovered that Stokes’ circuital condition on the motion of the ether is incompatible with having the ether stationary at the Earth’s surface. Lorentz advanced a new theory combining some of Stokes’ ideas with some of Fresnel’s; he also pointed out an oversight in Michelson’s (and Maxwell’s) analysis of the experiment, which halved the magnitude of the predicted effect, bringing it near the limits of the observations. Michelson and [Edward] Morley (1838-1923) then repeated the experiment with many improvements. Their conclusive results were published in 1887” (Everitt, James Clerk Maxwell. Physicist and Natural Philosopher, pp. 118-122).

“In the 1962 reprint of Michelson's book Studies in Optics, Harvey B. Lemon wrote in his introduction: ‘To the complete astonishment and mystification of the scientific world this refined experiment also yielded absolutely negative results. Again must we note at this point the universal confidence with which any experimental fact announced by Michelson was instantly accepted. Not for twenty years did anyone have the temerity to challenge his conclusion.’ This may well be part of the reason that there is no explicit reference to the Michelson-Morley experiment in Einstein’s great paper of 1905 on the Special Theory of Relativity – Michelson’s null result instantly became one of the established facts in the thorny problem of understanding the nature of the ether” (Longair, CavMag, p. 13).

Longair, ‘Maxwell, the Ether and the Michelson-Morley Experiment,’ CavMag, Issue 12, August 2014, pp. 12-13.

8vo (218 x 140 mm), pp. 151 with one folding plate. Original printed wrappers, front wrapper darkened and a little frayed, front joint worn, rear wrapper fine, internally fresh and clean.

Item #4303

Price: $1,750.00

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