Less Is More
Ludwig Boltzmann was one of the greatest theoretical physicists of the late 19th and early 20th centuries. We owe to Boltzmann, for example, our present understanding of entropy as being the progression of the colliding molecules of, say, a gas toward configurations of greater and greater randomness, something that is also known as the second law of thermodynamics. Boltzmann had the misfortune, however, to have as a colleague at the University of Vienna the physicist-philosopher Ernst Mach, who, although not a scientist of the first rank, had influenced people like Einstein with his skeptical views of established physical theories.
One of the theories that Mach was then skeptical of was just the sort of molecular mechanics that Boltzmann was creating. The two clashed, and Boltzmann later wrote, “I once engaged in a lively debate on the value of atomic theories with a group of academicians, including Hofrat Professor Mach, right on the floor of the academy [of science] itself. . . . Suddenly Mach spoke out from the group and laconically said: ‘I don’t believe that atoms exist.’ This sentence went round and round in my head.” When confronted, Mach was fond of asking, “Haben Sie einen gesehen?”--”Have you seen one?” A question that neither Boltzmann nor anyone else at the time could respond to.
If Boltzmann had only been able to live until the end of this century--he committed suicide in 1906 at 62--he would have been able to respond “yes” to this question. In the last decade, techniques have been developed, such as the so-called scanning tunneling microscope, that reveal configurations of atoms at the same level of reality that an ordinary telescope reveals the existence of the moon. But, if Mach were still alive, he could engage Boltzmann in lively debates as to whether the modern physicist’s version of the atom--the quark--exists. The chemical atom--the atom of Boltzmann--long ago in this century gave up its place as the ultimate indivisible unit of matter. Even the neutrons and protons that constitute the atomic nucleus have a complex “divisible” structure.
The structures of protons and neutrons apparently consist of “atomic” units--quarks. But do they exist? What does this question even mean? If it means can you see one?--can you see an isolated quark?--and if the present theories are right, then the answer is no. Because no individual quark will ever emerge from its confinement, you are free, if you want, to say that they don’t exist.
Considerations of this kind have been a part of atomic theory from its beginnings in ancient Greece. (A parallel development started about the same time in India.) It has always seemed to me that it would be a wonderful thing to have a book, or a course, devoted to just this subject--the historical atom. The only book that I know of on the subject, at least aside from the one under review here, is “The World of the Atom”--a two-volume collection of papers edited by H. A. Boorse and L. Motz, who supplied a running commentary. I much admire this collection, but the papers are, for the most part, too technical for the general reader to follow. Now, the late Bernard Pullman (he died in 1996), professor of quantum chemistry at the Sorbonne, has written “The Atom in the History of Human Thought”--a panoramic view of the atomic paradigm from the Greeks to the quarks in about 400 pages.
Stylistically most of the book resembles a collection of somewhat disjointed encyclopedia entries rather than one single overarching vision. As a physicist, I had no trouble following the scientific arguments, although I did not think it was necessary for Pullman to use several of his valuable pages on some of the details of modern quantum chemistry. But, as Jean Cocteau remarked, poets are constrained to sing from their family trees. However, I found a good deal of the philosophy in “The Atom” very heavy lifting indeed. After reading this statement from Kant, for example, “Matter is impenetrable, because of its original force of expansion, but this force is only the consequence of the repulsive forces of each point of space filled with matter. But the space that matter fills is mathematically divisible to infinity, that is to say, its parts can be distinguished to infinity (in accordance with general proofs, even though they cannot be moved, and hence not separated . . . , “ I was tempted to send out for a pizza.
Things are made worse by the fact that, like many other students, Pullman follows quotations like this with almost equally impenetrable opposing views from scholars that I, at least, have never heard of and have no way of evaluating. The only writer I ever read on such matters who could make them both comprehensible and interesting was Bertrand Russell and, alas, Pullman is no Bertrand Russell.
From time to time, Pullman does emerge from the shadows, and one gets a sense of what a book like this could have been. An example is his discussion of Galileo. We all know that Galileo was condemned by the Catholic Church because he proclaimed--with very great vigor--that the Earth moves around the sun. What is less familiar is that Galileo was also condemned by the church because he was an atomist. This was brought into prominence a few years ago when an Italian historian of science, Pietro Redondi, discovered a document in the Vatican archives that was an anonymous denunciation of Galileo for his belief in the reality of atoms. Redondi wrote a book, “Galileo Heretic,” in which he claimed that it was really Galileo’s atomism, and not his astronomy, that was at the root of his problems with the church. The issue had to do with the Eucharist dogma of transubstantiation, which had been elevated to canon law in the mid-16th century at the Council of Trent. If one was an atomist, how could one then claim that the atoms of bread and wine--indivisible and indestructible--were transformed into the blood and body of Christ? (Incidentally, until the late 1920s, with the advent of quantum chemistry and the elucidation of the nature of the chemical bond between atoms, it was equally mysterious how any atomic elements transformed themselves chemically.)
Pullman appears to have examined these documents himself and has come to the conclusion that though Galileo was certainly under suspicion as an atomist he was nonetheless condemned for his astronomy and because of his generally intransigent attitude. On this he writes with authority and conviction. “I consider it naive and wrong to see Galileo’s trial as a kind of Greek tragedy, a one-on-one battle between ‘blind faith’ and ‘enlightened reason.’ There was a powerful group whose hostility toward Galileo was relentless.” So much for style, now for content.
Clearly choices have to be made in a book of about 400 pages that covers the history of the atom from Thales to Heisenberg. I can only say that I would have made different choices. I would have readily sacrificed many of the pages devoted by Pullman to the almost useless commentaries of the 19th century French positivist Auguste Comte (a fierce anti-atomist whose ideas bordered on the absurd) for serious elucidation of what the Mach-Boltzmann debates were really about--something Pullman barely mentions.
You could get the impression from his book that Mach was some sort of a fool and that the issues were trivial. They weren’t, and they are with us still. In the 19th century, there were really two atoms--the physicist’s atom and the chemist’s atom. The chemist’s atom can be traced to the work of early-19th century scientists such as the Briton John Dalton or the Frenchman Joseph-Louis Gay-Lussac or the Italian Amedee Avogadro. The chemist’s atom--the idea that gases like hydrogen or oxygen were made up of like molecules--accounted for the fact that when these gases combined into, say, water vapor, given volumes of hydrogen and oxygen would always produce the same volume of water vapor, never something in between. You did not have to know the mass or size of these atoms. You just had to know that they were there to make this deduction.
On the other hand, the physicist’s atom--the one that Boltzmann used in his statistical mechanical considerations--had a size and mass. It was a real particle. The difference was stated with great clarity by Einstein in his so-called “Autobiographical Notes,” in which he reviewed this debate. Einstein wrote, “In chemistry only the ratios of the atomic masses played any role, not their absolute magnitudes, so that [for the chemists] atomic theory could be viewed more as a visualizing symbol than as knowledge concerning the factual construction of matter.” Mach had no complaint whatever about the chemist’s atom. Indeed, he had no complaint about the physicist’s atom either so long as it was regarded as a “visualizing symbol.” We know this because in 1912 Mach and Einstein met in Vienna and discussed the issue. The meeting was arranged by my first teacher in physics, Philipp Frank, who had been a student of Boltzmann’s and was a friend and colleague of Einstein’s. Frank often spoke of this meeting, which took place when Mach was more than 70 and partially paralyzed by a stroke. Mach told Einstein that he accepted the utility of the atomic model in physics. What he didn’t accept was the existence of atoms. This conflict is given little attention in Pullman’s book.
I much admire the fact that Pullman treats both Indian and Arabic atomic speculations. One is not sure of their independence from their European counterparts, but it is fascinating to read about their similarities. What Pullman does not consider is why none of these early speculations led anywhere. It is true that after Lucretius’ famous poem about atoms, “On the Nature of Things” written in the first century BC, until the 17th century no real progress was made in atomic theory in Europe either. But then there was an explosion--a renaissance of which we are still a part. Nothing like this occurred in the Orient. There are no Indian Galileos or Newtons who burst forth to create a scientific miracle. I refuse to believe that this is for lack of genius. Genius can be found anywhere. It transcends race or gender. However, for scientific genius to flourish, a context is needed: organized scientific institutions. You must have a tradition, and until recently in a country like India there was none. There might well have been Indian Newtons, but there was no Cambridge University for them to develop in. This is certainly worth some discussion in a book on the history of atomic ideas.
The book also neglects radioactivity, a term coined by Marie Curie. The French have elevated Madame Curie to secular sainthood. I have not yet found a French biographer of Madame Curie who is prepared to discuss candidly the fact that, after her husband Pierre died in 1906, she had an affair with the theoretical physicist Paul Langevin, who was married and the father of several children. When it was discovered, it was such a scandal that members of the Swedish National Academy asked Madame Curie not to accept the second Nobel Prize, which they had just awarded her in 1911. She refused. I don’t fault Pullman for not discussing Curie’s sex life, which is not really germane to the history of the atom.
What I do fault him for is not making clear the revolution in the concept of the atom caused by the discovery of radioactivity. Radioactivity manifested several paradoxes, some of which Pullman discusses and some, equally important, that he does not discuss. Where did the energy come from? How could these apparently inert material objects continue to emit indefinitely energetic radiation? Here Curie’s ideas were completely befuddled. But this befuddlement was related to something else: her refusal to consider the destructibility of single atoms. She was persuaded that radioactivity was some sort of bulk phenomenon of matter. For her, individual atoms were still indivisible.
It took the genius of the New Zealand-born experimental physicist Ernest Rutherford, along with his young colleague Frederick Soddy, to realize that what was happening was that individual atoms were spontaneously dividing themselves! The energy being created was coming from the loss of mass in this process, atom by atom, according to Einstein’s formula E = mc 2 . You were forced to look at the notion of an atom in an entirely new way. Unfortunately, Pullman’s laconic treatment of this is totally inadequate.
Finally, there is the biggest lacuna of all. If you ask anyone why this is called the Atomic Age, you will be told immediately that it is because of the bomb. That is where the idea of the atom has led us. Perhaps, considering the self-destructive nature of the human race, this was inevitable. But that a book called “The Atom in the History of Human Thought” has nothing in it about this borders on the absurd. So, though I admire Pullman’s courage in trying to write a book like this, I only wish it had been better.
