4.0 Electromagnetism Comes of Age

The Possibility Becomes A Reality

“It is to be hoped that some author with a genius for popular exposition will soon write a ‘New Electromagnetism’ with action at a distance strictly tabooed…. Such a work would be electromagnetism up to date, and its possibility would be largely due to Oliver Heaviside.”

George Francis FitzGerald, (1851–1901)
The Electrician, August 11, 1893

FitzGerald’s pessimism turned to optimism [[i]], and by the time of his 1893 quote he had become a champion of the Maxwellian worldview. Why? Because behind the scenes, an unemployed telegrapher who quit his job in 1874 picked up where Maxwell left off. We’ve already encountered him, for his work is the filter through which we understand and interpret what Maxwell really meant. Oliver Heaviside (1850–1925) moved back in with his parents and would never again hold a “real” job, yet this twenty-something savant revolutionized electromagnetism by putting Maxwell’s abstract ideas to practical use.

Telegraphy was the “Victorian Internet.” Like today’s Internet, telegraphy spawned a host of other technical, business, and social innovations [[ii]]. The first transatlantic telegraph line, completed with enormous cost in 1858, failed due to poor design and poor understanding of the underlying science. Only after the American Civil War in 1866 did a line finally connect Europe to America. Technologists made progress but were hampered by confusing results. Signals would propagate faster going one way on a cable, and slower sent in the opposite direction. Different frequency signals propagated at different speeds. This “phase distortion” hampered telegraphy and made the emerging technology of telephony unusable beyond short distances.

Figure 4.1: Oliver Heaviside (1850–1925) revolutionized electromagnetism by refining Maxwell's ideas and by figuring out how to put Maxwell's theory to practical use [[iii]].

Heaviside solved all these technical problems and more. In the 1870s, he developed the “Telegraphers’ Equation” which applied Maxwell’s thinking to develop an electromagnetic wave theory of telegraphy.

Heaviside’s mature treatment of transmission lines, originally published in 1886-1887, occupies a considerable fraction of the second volume of his Electrical Papers [[iv]]. His discovery of the condition for distortionless propagation met with considerable resistance, however. Conventional wisdom called for reduction of loss and inductance to maximize performance, yet Heaviside defied the wisdom of “practical” engineers to argue that adding inductive loading was the key to reducing distortion. Figure 4.1 presents a rare photograph of the elusive engineer.

Heaviside first attempted to publish his results in a joint article with his older brother, Arthur West Heaviside (1844–1923). However, the British Government Post Office (GPO) not only employed the elder Heaviside, but also held a monopoly on telegraphy in the United Kingdom. William Henry Preece (1834–1913), Chief Engineer of the GPO, championed a rival (incorrect) theory and refused permission for Arthur to publish. Oliver eventually published his result in a trade magazine, The Electrician, with considerable sarcasm directed at Preece. There is little more entertaining in the electromagnetic literature than an epic Heaviside rant. For several years the controversy raged.

Ultimately, Heaviside was vindicated. In a few short years, he received professional recognition for his genius. Heaviside’s work made long distance telephony a possibility. Regrettably, the recognition did not include financial compensation for his discovery. Credit went to Michael I. Pupin (1858–1935) who in 1899 patented inductive loading (a decade after Heaviside’s discovery) and sold the rights to AT&T for $500,000 [[v]]. Paul Nahin (1940–   ) presents this story in detail in his excellent book on Heaviside [[vi]].

Perhaps even more important, Heaviside developed the very language of alternating current electronics in particular and electromagnetism in general. Students of electronics will be familiar with terms like impedance, inductance, permittivity, and conductance – all coined by Heaviside in his writings.

Of still greater importance were his mathematical innovations. In 1884, John Henry Poynting (1852–1914), preempted Heaviside by discovering the law governing the flow of energy in electromagnetic fields. Poynting presented his law in a long, pedantic, and difficult to follow paragraph:

The aim of this paper is to prove that there is a general law for the transfer of energy, according to which it moves at any point perpendicularly to the plane containing the lines of electric and magnetic force, and that the amount crossing the unit of area per second of this plane is equal to the product of the intensities of the two forces, multiplied by the sine of the angle between them, divided by 4π; while the direction of flow of energy is that in which a right-handed screw would move if turned round from the positive direction of the electromotive to the positive direction of the magnetic intensity [[vii]].

Figure 4.2: Poynting and Heaviside discovered that the electromagnetic energy flows at right angles to the electric and magnetic field intensities.

The following year, Heaviside presented the same result. Expressed in the language of the vector analysis Heaviside pioneered, the directed energy flow per area (S) is related to the electric field vector (E) and the magnetic field vector (H) according to a vector cross product: S = E × H [[viii]]. In a mere five characters, Heaviside expressed the same concept that took Poynting a paragraph.

Heaviside’s revolution was a bit like the earlier transition from Roman to Hindu-Arabic numerals. Roman numerals make mathematical analysis more challenging. Imagine multiplying XIII by XIII to obtain CLXIX, or performing bookkeeping with nearby numbers of substantially different length. The introduction of Hindu-Arabic numerals to the West by the famed Italian mathematician, Fibonacci (~1175–~1250), enabled the development of accounting and spurred the explosive economic growth of the Renaissance. Heaviside’s compact vector notation revolutionized electromagnetism. We’ve already seen that what we today call “Maxwell’s” Equations are actually Heaviside’s cleaned up and streamlined interpretation of Maxwell’s less elegant presentation.

Next time 4.1 Heaviside, Poynting, & Energy Flow: “When energy goes from place to place, it traverses the intermediate space.”

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References

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[i] FitzGerald, George, “On the Possibility of Originating Wave Disturbances in the Ether by Means of Electric Forces,” From the Scientific Transactions of the Royal Dublin Society, read May 5, 1882. See Collected Works, p. 101.
“It seems further highly probable that the energy of varying currents is in part radiated into space and so lost to us.”

[ii] Standage, Tom, The Victorian Internet, New York: Walker and Company, 1998.

[iii] See https://commons.wikimedia.org/wiki/File:Oheaviside.jpg

[[iv]]        Heaviside, Oliver, Electrical Papers vol. 2, New York: Macmillan and Co., 1892.

[[v]]        Hunt, Bruce J., “Oliver Heaviside: A First Rate Oddity,” Physics Today, November 2012, pp. 48–54.

[[vi]]        Nahin, Paul, Oliver Heaviside: The Life, Work, and Times of an Electrical Genius of the Victorian Age, Baltimore: The Johns Hopkins University Press, 2002, Chapter 8.

[[vii]]       Poynting, John Henry, “On the Transfer of Energy in the Electromagnetic Field,” Philosophical Transactions, vol. 175, 1884, pp. 343-361. Collected in Collected Scientific Papers by John Henry Poynting, Cambridge At the University Press, 1920, pp. 175-193, see p.

[[viii]]      Heaviside, Oliver, Electrical Papers, Vol. 1, London: Macmillan and Co. 1892, pp. 429–556. Original published in The Electrician, 1885-1886.