In telling a story about physics and some of its significance for a life of awareness I’ll start with an idea of the philosopher Immanuel Kant (1724 – 1804). Kant, in my mind, is associated with impenetrable German which translates into impenetrable English. To find some clarity about Kant’s ideas one turns to Wikipedia, where the opening paragraph of the Kant entry explains his main ideas in an uncharacteristically comprehensible way. One of these ideas is that we are born into this world with our minds prepared to understand space, time, and causality. And with this kind of mental conditioning we can make sense of simple phenomena, and, indeed, pursue science. This insight predates Darwin’s theory of evolution which offers a plausible explanation for it, by some sixty-odd years, and was thus a remarkable insight on the part of Kant. Another Kant idea that is relevant to our story is his distinction between what he calls phenomena and noumena. Quoting from Wikipedia, “… our experience of things is always of the phenomenal world as conveyed by our senses: we do not have direct access to things in themselves, the so-called noumenal world.” Of course, this is only one aspect of Kant’s thought, but the aspect that seems to me most relevant to what might be meant by physical reality. Kant was a philosopher’s philosopher, totally dedicated to deepening our understanding of what we may comprehend about the world and morality by purely rational thought. He was born in Königsberg, East-Prussia, at the time a principality on the Baltic coast east of Denmark and north of Poland-Lithuania; and died there 80 years later. Legend has it that during his entire life he never traveled more than 10 miles from his home. The Wikipedia article refutes this slander: Kant actually traveled on occasion some 90.1 miles from Königsberg.
The massive extent of Kant’s philosophy leaves me somewhat appalled, particularly since I understand little of it and because what I perhaps do understand seems dubious at best and meaningless at worst. What Kant may not have realized is the idea that the extent and nature of the noumenal world is relative to the times in which one lives. Kant was born 3 years before Isaac Newton died, so by the date of his birth the stage was well set for the age of classical physics. During his life classical mechanics was developed largely by two great mathematicians, Joseph-Louis Lagrange (1736 – 1813) and Pierre-Simon Laplace (1747 – 1849). Looking back from Kant’s time to the ancient world one sees an incredible growth of the phenomenal world, with the Copernican revolution, a deepening understanding of planetary motion, and Newton’s Laws of mechanics. In the time since Kant lived laws of electricity and magnetism, statistical mechanics, quantum mechanics, and most of present-day science were developed. This advance raises a question. Does the growth of the phenomenal world entail a corresponding decrease in the noumenal world or are phenomena and noumena entirely independent of one another? Of course, I’d like to have it both ways, and can do so by imagining two senses of noumena. To get an idea of the first original idea, I will tell a brief story. In the early 1970’s we were visited at Auburn University by the great physicist, John Archibald Wheeler, who led a discussion in our faculty meeting room. I was very impressed by Dr. Wheeler. To me he seemed a “tiger”, totally dedicated to physics, his students, and to an awareness of what lay beyond our comprehension. At one point he pointed to the tiles on the floor and said to us physicists, something like, “Let each one of you write your favorite physics laws on one of these tiles. And after you’ve all done that, ask the tiles with their equations to get up and fly. They will just lie there; but the universe flies.” Wheeler had doubtless used this example on many prior occasions, but it was new to me and seems to get at the meaning of noumena as a realm independent of anything science can ever discover. On the other hand, as the realm of phenomena that we do understand has grown, we can regard noumena simply as a “blank” in our knowledge, a blank which can be filled in as science, so to speak, peels back the layers of an “onion” revealing the understanding of a larger world, and at the same time, exposing a new layer of ignorance to attack. This second sense of the word in no way diminishes the ultimate mystery of the universe. In fact, it appears to me that the quest for ultimate understanding in the face of the great mystery is what gives physics (and science) a compulsive, even addictive, fascination for its practitioners. Like compulsive gamblers experimental physicists work far into the night and theorists endlessly torture thought. Certainly, the idea that we could conceivably uncover ever more specifics into the mystery of ultimate being is what drew me to the area. That, as well as the idea that if one wants to understand “everything”, physics is a good place to start.
In my understanding, the story of physics during my lifetime and the 30 years preceding my birth is the story of a massive, earthshaking revolution. Thomas Kuhn’s The Structure of Scientific Revolutions, mentioned in earlier posts is a story of many shifts in scientific perception which he calls revolutions. In his terms what I’m talking about here is a “super-duper-revolution”, a massive shift in understanding whose import is still not fully realized in our society at large at the present time. Most of the ”revolutions” that Kuhn uses as examples affect only scientists in a particular field. For example, the fall of the phlogiston theory and the rise of Oxygen in understanding fire and burning was a major revolution for chemistry, but had little effect on the culture of society at large. Similarly, in ancient times the rise of Ptolemaic astronomy mostly concerned philosophers and intellectuals. The larger society was content with the idea that gods or God controlled what went on in the heavens as well as on earth. The Copernican revolution, on the other hand, was earth shaking (super-duper) for the entire society, mainly because it called into question theories of how God ran the universe and because it became the underpinning of an entirely new idea of what was “real”. Likewise, the scientific revolution of the 16th and 17th centuries was earthshaking to the entire society, which, however, as time wore on into the 18th and 19th centuries became accustomed to it and assumed that the classical, Newtonian “clockworks” universe was here to stay forever however uncomfortable it might be to artists and writers, who hoped to live in a different, more meaningful world of their own experience, rejecting scientific “reality” as something which mattered little in a spiritual sense. Who could have believed that in the mid 1890’s after 300 years (1590 – 1890, say) of continued, mostly harmonious development the entire underpinning of scientific reality was about to be overturned by what might be called the quantum revolution. Yet that is what happened in the next forty years (1895 – 1935) with continuing advances and consolidation up to the present day. (From now on I’ll use the abbreviation QM for Quantum Mechanics, the centerpiece of this revolution.) Of course, as with any great revolution, all has not been smooth. Many of the greatest scientists of our times, most notably Albert Einstein and Erwin Schrödinger, found the tenets of the new physics totally unacceptable and fought them tooth and nail. In fact, there is at least one remaining QM puzzle epitomized by “Schrödinger’s Cat” about which I hope to have my say at some point.
It is my hope that readers of this blog will find excitement in the open possibilities that an understanding of the revolutionary physical “reality” we currently live in suggests. In talking about it I certainly don’t want to try “reinvent the wheel” since many able and brilliant writers have told portions of the story. What I can do is give references to various books and URL’s that are with few exceptions (which I’ll note) great reading. I’ll have comments to make about many of these and hope that with their underpinning, I can tell this story and illuminate its relevance for what I’ve called Western Zen.
The first book to delve into is The Quantum Moment: How Planck, Bohr, Einstein, and Heisenberg Taught us to Love Uncertainty by Robert P. Crease and Alfred Scharff Goldhaber. Robert Crease is a philosopher specializing in science and Alfred Goldhaber is a physicist. The book, which I’ll abbreviate as TQM, tells the history of Quantum Mechanics from its very beginning in December, 1900, to very near the present day. Copyrighted by W.W. Norton in 2014 it is quite recent, today as I write being early November, 2018. The story this book tells goes beyond an exposition of QM itself to give many examples of the effects that this new reality has had so far in our society. It is very entertaining and well written though, on occasion it does get slightly mathematical in a well-judged way in making quantum mechanics clearer. A welcome aspect of the book for me was the many references to another book, The Conceptual Development of Quantum Mechanics by Max Jammer. Jammer’s book (1966) is out of print and is definitely not light reading with its exhaustive references to the original literature and its full deployment of advanced math. Auburn University had Jammer in its library and I studied it extensively while there. I was glad to see the many footnotes to it in TQM, showing that Jammer is still considered authoritative and that there is no more recent book detailing this history. Recently, I felt that I would like to own a copy of Jammer so found one, falling to pieces, on Amazon for fifty odd dollars. If you are a hotshot mathematician and fascinated by the history of QM, you will doubtless find Jammer in any university library.
The quantum revolution occurred in two great waves. The first wave, called the “old quantum theory” started with Planck’s December, 1900, paper on black body radiation and ended in 1925 with Heisenberg’s paper on Quantum Mechanics proper. From 1925 through about 1932, QM was developed by about 8 or so geniuses bringing the subject to a point equivalent to Newton’s Principia for classical mechanics development. Besides the four physicists of the Quantum Moment title, I’ll mention Louis de Broglie, Wolfgang Pauli, PAM Dirac, Max Born, Erwin Schrödinger. And there were many others.
A point worth mentioning is that The Quantum Moment concentrates on what might be called the quantum weirdness of both the old quantum theory and the new QM. This concentration is appropriate because it is this weirdness that has most affected our cultural awareness, the main subject of the book. However, to the physicists of the period 1895 – 1932, the weirdness, annoying and troubling as it was, was in a way a distraction from the most exciting physics going on at the time; namely, the discovery that atoms really exist and have a substructure which can be understood, an understanding that led to a massive increase in practical applications as well as theoretical knowledge. Without this incredible success in understanding the material world the “weirdness” might have well have doomed QM. As we will mention below most physicists ignore the weirdness and concentrate on the “physics” that leads to practical advances. Two examples of these “advances” are the atomic bomb and the smart phone in your pocket. In the next few paragraphs I will fill in some of this history of atomic physics with its intimate connection to QM.
The discovery of the atom and its properties began in 1897 as J.J. Thomson made a definitive breakthrough in identifying the first sub-atomic particle, the lightweight, negatively charged electron (see Wikipedia). Until 1905, however, many scientists disbelieved in the “reality” of atoms in spite of their usefulness as a conceptual tool in understanding chemistry. In the “miracle year” 1905 Albert Einstein published four papers, each one totally revolutionary in a different field. The paper of interest here is about Brownian motion, a jiggling of small particles, as seen through a microscope. As a child I had a very nice full laboratory Bausch and Lomb microscope, given by my parents when I was about 7 years old. In the 9th grade I happened to put a drop of tincture of Benzoin in water and looked at it through the microscope, seeing hundreds of dancing particles that just didn’t behave like anything alive. I asked my biology teacher about it and after consulting her husband, a professor at the university, she told me it was Brownian motion, discovered by Robert Brown in 1827. I learned later that the motion was caused because the tiny moving particles are small enough that molecules striking them are unbalanced by others, causing a random motion. I had no idea at time how crucial for atomic theory this phenomenon was. It turns out that the motion had been characterized by careful observation and that Einstein showed in his paper how molecules striking the small particles could account for the motion. Also, by this time studies of radioactivity had shown emitted alpha and beta particles were clearly sub-atomic, beta particles being identical with the newly discovered electrons and the charged alpha particles turning into electrically neutral helium as they slowed and captured stray electrons.
Einstein’s other 1905 papers were two on special relativity and one on the photoelectric effect. As strange as special relativity seems with its contraction of moving measuring sticks, slowing of moving clocks, simultaneity dependent upon the observer to say nothing of E = mc², this theory ended up fitting comfortably with classical Newtonian physics. Not so with the photoelectric effect.
Planck’s Discovery of a Black Body Formula
In December, 1900, Max Planck started the quantum revolution by finding a physical basis for a formula he had guessed earlier relating the radiated energy of a glowing “black body” to its temperature and the frequencies of its radiation. A “black body” is made of an ideal substance that is totally efficient in radiating electro-magnetic waves. Such a body could be simulated experimentally with high accuracy by measuring what came out of a small hole in the side of an enclosed oven. To find the “physics” behind his formula Planck had turned to statistical mechanics, which involves counting numbers of discrete states to find the probability distribution of the states. In order to do the counting Planck had artificially (he thought) broken up the continuous energy of electromagnetic waves into chunks of energy, hν, ν being the frequency of the wave, denoted historically by the Greek letter nu. (Remember: the frequency is associated with light’s color, and thus the color of the glow when a heated body gives off radiation) Planck’s plan was to let the “artificial” fudge-factor h go to zero in the final formula so that the waves would regain their continuity. Planck found his formula, but when he set h = 0, he got the classical Raleigh-Jeans formula for the radiation with its “ultra-violet catastrophe”. The latter term refers to the Raleigh-Jeans formula’s infinite energy radiated as the frequency goes higher. Another formula, guessed by Wien, gave the correct experimental results at high frequencies but was off at lower frequencies where the Raleigh-Jeans formula worked just fine. To his dismay what Planck found was that if he set h equal to a very small finite value, his formula worked perfectly for both low and high frequencies. This was a triumph but at the same time, a disaster. Neither Planck nor anyone else believed that these hν bundles could “really” be real. Maybe the packets came off in bundles which quickly merged to form the electromagnetic wave. True, Newton had thought light consisted of a stream of tiny particles, but over the years since his time numerous experiments showed that light really was a wave phenomenon, with all kinds of wave interference effects. Also, in the 19th century physicists, notably Fraunhofer, invented the diffraction grating and with it the ability to measure the actual wave length of the waves. The Quantum Moment (TQM) has a wonderfully complete detailed story of Planck’s momentous breakthrough in its chapter “Interlude: Max Planck Introduces the Quantum”. TQM is structured with clear general expositions followed by more detailed “Interludes” which can be skipped without interrupting the story.
Einstein’s 1905 photoelectric effect paper assumed that the hν quanta were real and light actually acted like little bullets, slamming into a metal surface, penetrating, colliding with an atomic electron and bouncing it out of the metal where it could be detected. It takes a certain energy to bounce an electron out of its atom and then past the surface of the metal. What was experimentally found (after some tribulations) was that energy of the emerging electrons depended only on the frequency of the light hitting the surface. If the light frequency was too low, no matter how intense the light, nothing much happened. At higher frequencies, increasing the intensity of the light resulted in more electrons coming out but did not increase their energy. As the light frequency increased the emitted electrons were more energetic. It was primarily for this paper that Einstein received his Nobel Prize in 1921.
A huge breakthrough in atomic theory was Ernest Rutherford’s discovery of the atomic nucleus in the early years of the 20th century. Rather than a diffuse cloud of electrically positive matter with the negatively charged electrons distributed in it like raisins (the “plum pudding” model of the atom) Rutherford found by scattering alpha particles off gold foil that the positive charge of the atom was in a tiny nucleus with the electrons circling at a great distance (the “fly in the cathedral model”). There was a little problem however. The “plum pudding” model might possibly be stable under Newtonian classical physics, while the “fly in the cathedral” model was utterly unstable. (Note: Rutherford’s experiment, though designed by him, was actually carried out between 1908 and 1913 by Hans Geiger and Ernest Marsden at Rutherford’s Manchester lab.) Ignoring the impossibility of the Rutherford atom physics plowed ahead. In 1913 the young Dane Niels Bohr made a huge breakthrough by assuming quantum packets were real and could be applied to understanding the hydrogen atom, the simplest of all atoms with its single electron circling its nucleus. Bohr’s model with its discrete electron orbits and energy levels explained the spectral lines of glowing hydrogen which had earlier been discovered and measured with a Fraunhofer diffraction grating. At Rutherford’s lab it was quickly realized that energy levels were a feature of all atoms, and the young genius physicist, Henry Moseley, using a self-built X-ray tube to excite different atoms refined the idea of the atomic number, removing several anomalies in the periodic table of the time, while predicting 4 new chemical elements in the process. At this point World War I intervened and Moseley volunteered for the Royal Engineers. One among the innumerable tragedies of the Great War was the death of Moseley August 10, 1915, aged 27, in Gallipoli, killed by a sniper.
Brief Interlude: It is enlightening to understand the milieu in which the quantum revolution and the Great War occurred. A good read is The Fall of the Dynasties – The Collapse of the Old Order: 1905 – 1922 by Edmond Taylor. Originally published in 1963, the book was reissued in 2015. The book begins with the story of the immediate cause of the war, an assassination in Sarajevo, Bosnia, part of the dual monarchy Austria-Hungary empire; then fills in the history of the various dynasties, countries and empires involved. One imagines what it would be like to live in those times and becomes appalled by the nationalistic passions of the day. While explicating the seemingly mainstream experience of living in the late 19th and early 20th century, and the incredible political changes entailed by the fall of the monarchies and the Great War, the aspects of the times, which we think of, these days, as equally revolutionary are barely mentioned. These were modern art with its demonstration that aesthetic depth lay in realms beyond pure representation, the modern novel and poetry, the philosophy of Wittgenstein which I’ve discussed above and perhaps most revolutionary of all, the fall of classic physics and rise of the new “reality” of modern physics which we are talking about in this post. (With his deep command of the relevant historical detail for his story the author does, however, get one thing wrong when he briefly mentions science. He chooses Einstein’s relativity of 1905 but calls it “General Relativity” putting in an adjective which makes it sound possibly more exciting than plain “relativity”. The correct phrase is “Special Relativity” which indeed was quite exciting enough. General Relativity didn’t happen until 1915.)
Unlike the second world war the first was not a total war and research in fundament physics went on. The mathematician turned physicist Arnold Sommerfeld in Munich generalized Bohr’s quantum rules by imagining the discrete electron orbits as elliptical rather than circular and taking their tilt into account, giving rise to new labels (called quantum numbers) for these orbits. The light spectra given off by atoms verified these new numbers with a few discrepancies which were later removed by QM. During this time and after the war ended, physicists became concerned about the contradiction between the wave and particle theories of light. This subject is well covered in TQM. (See the chapter “Sharks and Tigers: Schizophrenia”. It is easy to see the problem. If one has surfed or even just looked at the ocean, one feels or sees that a wave carries energy along a wide front, this energy being released as the wave breaks. This kind of energy distribution is characteristic of all waves, not just ocean waves. On the other hand, a bullet or billiard ball carries its energy and momentum in a compact volume. Waves can interfere with each other, reinforcing or canceling out their amplitudes. So, what is one to make of light which makes interference patterns when shined through a single or double slit but acts like a particle in the photoelectric effect or, even more clearly, like a billiard ball collision when a light quantum, called a photon, collides with an electron, an effect discovered by Arthur Compton in 1923. To muddy the waters still further, in 1922 the French physicist Louis de Broglie reasoned that if light can act like either a particle or wave depending on circumstances, by analogy, an electron, regarded hitherto as strictly a particle, could perhaps under the right conditions act like a wave. Although there was no direct evidence for electron waves at the time, there was suggestive evidence. For example, with the Bohr model of the hydrogen atom if one assumed the lowest, “ground state” orbit was a single electron wave length, one could deduce the entire Bohr theory in a new, simple way. By 1924 it was clear to physicists that the “old” quantum mechanics just wouldn’t do. This theory kept classical mechanics and classical wave theory and restricted their generality by imposing “quantum” rules. With both light and electrons being both wave and particle, physics contained an apparent logical contradiction. Furthermore, though the “old” theory had successes with its concept of energy levels in atoms and molecules, it couldn’t theoretically deal at all with such seemingly simple entities as the hydrogen molecule or the helium atom which experimentally had well defined energy levels. The theory was a total mess. It was in 1925 that the beginnings of a completely new, fundamental theory made its appearance leading shortly to much more weirdness than had already appeared in the “old quantum” theory. In the next post I’ll delve into some of the story of the new QM.