17.1. A Little Bit about Lorentz#
Look at the picture of this kindly gentleman. It’s a picture of Hendrik Lorentz taken when he visited Cornell University. The universal accounts of Lorentz match the image that this photograph projects: a nice man. A father figure – indeed, Einstein viewed him as such. This mild-mannered Lion was the King of Electrodynamics and the acknowledged leader of theoretical physics until his death.
“At the turn of the century, H. A. Lorentz was regarded by theoretical physicists of all nations as the leading spirit; and this with the fullest justification. No longer, however, do physicists of the younger generation fully realise, as a rule, the determinant part which H. A. Lorentz played in the formation of the basic principles of theoretical physics. The reason for this curious fact is that they have absorbed Lorentz’ fundamental ideas so completely that they are hardly able to realise to the full the boldness of these ideas, and the simplification which they brought into the foundations of the science of physics.” Albert Einstein
Lorentz entered the University of Leiden in 1870…but after two years went back to his home town in Arnhem – where he taught high school evening classes. Remarkably, he then worked on his doctorate alone on his own while doing the teaching.
His 1875 PhD thesis was a complete re-thinking of Maxwell’s original theory. What Maxwell wrote was incredibly obscure – impossible to read today. I tried years ago… even if one gets past the obscure basis of his model, it’s pages and pages for one formula, done over and over again. Just a mammoth mess. Paul Ehrenfest, a friend of Einstein’s called it an “intellectual jungle.” That’s kind.
While it’s easy to dismiss it because of its impenetrability, not since Newton had there been such a new way of trying to describe the physical world and, like Newton, Maxwell had one foot in the past and one foot in a completely uncertain, and novel future. Language and technique were being invented on the fly and one has to wonder that if he’d lived longer, he might have cleaned up his original, extensive work.
Keep in mind that Maxwell only knew about bulk matter: finite-sized pith balls of charged material. Hunks of iron magnets. Stuff you could hold in your hand. He was only barely able to envision the unity of optics, magnetism, and electricity that he’d birthed, let alone the connection with radiant heat or ultraviolet light or any other form of electromagnetism.
Maxwell was committed to the ether, but his was a very strange ether: there was an ether of empty space and a separate, but coupled, ether of materials like glass. Matter was not composite, it was bulk and carried its own ether medium.
Lorentz tamed all of this.
On the basis of his thesis – again, remember, self-taught – he was made professor of mathematical physics at Leiden in 1878 and remained there until he retired in 1912. He married Aletta Kaiser, whose father was the Director of (what’s now called) the amazing Rijksmuseum. They had two daughters, one of whom became a physicist, and a son. One of his biggest distractions was fending off the dozens of job offers from universities in Europe and the United States. But he stayed.
17.1.1. Electrons Were Lorentz’s Idea…before there were electrons#
Lorentz’ original notion was that there was only one ether and there was matter, which was separate but connected in a speculative way. He envisioned that matter consisted of individual charges and that electromagnetic radiation was caused by the acceleration of those charges. He didn’t call them “electrons” and didn’t have a picture of electrons and protons in atoms – just that some particulate charges inside matter. (The electron was discovered by Thomson in 1897, but the atomic picture wasn’t proposed until 1913.)
Maxwell didn’t say any of this, Lorentz did. He further calculated what kind of radiation would occur if a material were in a magnetic field which matched the effect of Sodium vapor which was placed in a B field by Peter Zeeman. Zeeman was Lorentz’ student and it was a partnership of experiment and explanation that gained them both the Nobel Prize in 1902. We call it the Zeeman Effect (the splitting of atomic spectral lines by a magnetic field) and quantum mechanics become the detailed explanation within the context of atomic theory.
A part of Lorentz’ theory was the calculation that forces that electric charges would experience that we called the Lorentz Force earlier. It’s not wrong – and many times it’s used – to call electromagnetism the Maxwell-Lorentz equations.
For Lorentz, the ether was required but there was only one. He replaced Maxwell’s complicated substance with that single, fixed ether and the individual charges. Their electromagnetic radiation then propagated in the ether so it coupled ether with matter through those charges. The equations that resulted, with some notational innovations (like vector calculus) added by Helmholtz, became the E&M that’s taught to physicists and engineers today.
Perhaps now you can appreciate how Lorentz’ electron theory formed the basis of his treatment of the Michelson-Morley Experimental results. His commitment to electrically charged molecular objects and the realization that forces on them could be affected by motion (Lorentz Force) that it was reasonable to assume that the physical dimensions of Michelson’s interferometer’s materials would change as they (and their charged constituents) passed through the ether.
Hence we still call this effect “Lorentz Contraction” and the equations that he figured out that would explain that effect, the “Lorentz Transformations.”
His life which ended at the age of 74 years old in 1928 was celebrated in a huge funeral in Haarlem where he had retired, although while still lecturing at Leiden.
Let’s let his son report that day:
Never before had there been such a general mourning in the Netherlands at the passing of a theoretical scientist, as there was at my father’s death. I myself saw women from the lower classes in Leyden, as well as men from the upper classes, who were not able to control their emotions.
On the day of the funeral, by instruction of the Postmaster General of the Netherlands, the tele graph service throughout the country was closed from twelve noon to 12.03. Thus the funeral of my father became almost a royal homage.
An abstract from the account printed in one of our prominent newspapers will give the readers an impression of the occasion.
“Today Haarlem has buried its great citizen Lorentz and has paid homage to this scholar in a manner both touching and dignified. Already in the early morning an unusual activity was noticeable in the city. Automobiles and carriages travelled back and forth, and it was significant that there was hardly an automobile to be had for those desiring one. From many buildings, such as the Town Hall, the Main Church, the Railway Station and the Cavalery Barracks flags were flown half-mast. In the main streets lanterns draped with crape were burning. Long before the appointed hour thousands and again thousands of people had gathered along the road, while there was great activity about and at the cemetery.
At the moment that the procession started, the bells of a number of churches, Protestant as well as Roman Catholic, spread their mournful notes of the city. The thousands of people along the road took off their hats in token of deep respect when the procession passed.
There were tributes from around the world, but let’s let Einstein speak his piece:
“For me personally he meant more than all the others I have met on my life’s journey. Just as he mastered physics and mathematical structures, so he mastered also himself, — with ease and perfect serenity. His quite extraordinary lack of human weaknesses never had a depressing influence on his fellow-men. Everyone felt his superiority; no one felt depressed by it. For, although he had a keen insight into human nature and human relationships, he had a charitable kindness towards it all. His influence was never a dominating, but always a serving, helping one. He was exceedingly conscientious, without, however, making any particular matter appear unduly important. From this, he was protected by his fine sense of humour, which reflected itself in his eyes and in his smile.”
That smile and those eyes.