Probabilities of the Quantum World (Pt-3)
Summarizing the Masterpiece by Daniel Danin
[To refresh, Part-2 of this series is here. Text in such square brackets is my commentary. Rest of it is a faithful documentation of the most fascinating story ever told of the Quantum Revolution]
[At the end of Part-2, we had just entered the atomic age with the discovery of X-rays, radioactivity and the electron]
The Cambridge professor J. J. Thomson recalled forty years later after his discovery of the electron that he had made the first report about the existence of these particles during the evening session of the Royal Institute on Friday April 30th, 1897. Much later, a prominent physicist old Thompson that he had thought at the moment that Thomson’s report was a hoax. Thomson was not surprised, since he himself was very reluctant to give such an interpretation of his experiments; only when he was satisfied that there was no other way of accounting for the experimental data did he report that he believed in the existence of bodies smaller than atoms.
[I put myself in Thomson’s shoes for a moment. I have data that indicates that what the entire scientific community believes to be a fact, i.e., atoms are the smallest we can go to & that nothing is smaller than atoms, is in-fact, not true. What would I have done? Most likely I would have chicken’d out. But Thomson kept at it; Diligently coming up with one plausible explanation after another. Only after all else failed did he propose the existence of electrons; a structure that was smaller than the atom! Integrity and Honesty are the two hallmark qualities of a great Scientist.]
So, what was the scientist disturbed by? Indeed, a hundred and fifty years ago, in 1750, Franklin, famous for his lightning rods, made a reasonable speculation that electric “matter” consisted of extremely fine particles. In 1891, six years before Thomson’s report, his compatriot Stoney gave a name to this hypothetical particle, calling it an “electron”. Thomson did not even need a new name for his particles. He should not have been so ‘reluctant’ about his discovery…
It sounds fantastic but Wilhelm Roentgen [the one who discovered X-rays] refuted the discovery of “the bodies smaller than atoms”! In his laboratory in Wurzburg where he had recently made his famous discovery [X-rays], Roentgen did not allow his students and workers to even mention “electrons”. In 1900 when he transferred to Munich, this prohibition went with him.
By the end of World War One (1914–1918) the German people were starving as Germany neared collapse. The 73-year-old Roentgen was losing his strength through malnutrition. His Dutch friends sent him butter and sugar. However, he felt that it was improper to care for her personal well-being while those around him suffered and he gave away these food parcels. His moral sense was always unwavering.
[The War wrecked havoc all around. Little do we realize how disastrous it was for the Scientific community at the frontier of our understanding of Nature.]
In contrast to the classicist Roentgen, the free-thinker Einstein saw that the electron was a stranger in the country of classical electrodynamics. Einstein did not want to deprive this stranger of a residence permit for physics: he was interested what the electron could tell about the laws of the still unknown country he came from.
Ten years after the discovery of Thomson’s particles,
in the year 1907, thirty-six-year-old Ernest Rutherford came to Manchester University to become head of a laboratory there; a twenty-two-year-old student at Copenhagen University, Niels Bohr, was still in his fourth year of studies; and at the University of Vienna a twenty-year-old Erwin Schrodinger was in his second year. In Paris a fifteen-year-old Louis de Broglie still had another year before finishing at the lycee while in Munich a six-year-old Werner Heisenberg was playing checkers. Lev Landau was not yet born and quantum physics was in its cradle.
The discovery of the electron made it possible, at last, to start visualizing the atom and to develop plausible models for it. Here is an entry from the diary of a student at the University of Strasbourg:
“January 22, 1887.
Each atom… is a complete solar system, that is, it consists of different atom-planets which revolve at different speeds around the central planet, or move periodically in any other way.”
That was a young student from Moscow, Pyotr Lebedev who later became famous as the first experimenter to measure the extremely small pressure of light.
Naturally, J. J. Thomson who brought electrons onto the physical scene began at once, as early as 1898, constructing a model of an atom. But he was not tempted with profound astronomical parallels; his role for electrons in the atom was quite prosaic; that of ‘raisins in a dough’. But if the negatively charged electrons in Thomson’s model were the raisins, what was the dough? It was atomic space itself, ‘a sphere with uniform positive electrisation’. It provided for the electrical neutrality of the atom as a whole: any model had to satisfy this physical requirement.
Thomson had to modify his model. After six years, in 1904, he allowed electrons to revolve in individual small groups or rings. But still the model was far from being plausible. Its irreparable drawback was the idea of positively charged space. But the answer was still unclear, nor revealed in experiment. Until Rutherford came…
He was a student of J.J. — the first overseas student in ancient Trinity College in Cambridge. When the twenty-four-year-old son of a New Zealand farmer appeared there in 1895 the old Cambridge hands looked askance at the newcomer. But soon Cambridge would hear the words of an eminent physicist:
“We have got a rabbit here from the Antipodes and he is burrowing mighty deep.”
The New Zealander’s imagination was captured by news brought from France — radioactivity. This broke new ground. And he distinguished two types of charged rays in the strange radiation of Uranium denoting them with Greek letters ‘alpha’ and ‘beta’. He showed that alpha rays were beams of heavy particles with a doubled positive charge while the beta rays were beams of light particles with a single negative charge. It was he who discovered that radioactivity was the spontaneous decay of complex atoms which proceeded according to the statistical laws of chance. As a young man of just over thirty, with a still younger Frederick Soddy, he proved the amazing idea that in each event of such radioactive decay the age-old dream of alchemists is fulfilled, that is, the transmutation of chemical elements.
The eminent astrophysicist Arthur Eddington once said at a dinner of the Royal Society that electrons were, probably, just a ‘speculative concept’ and did not exist in reality. Rutherford sprang to his feet,
“Not exist? not exist? Why, I can see the little beggars as plainly as I can see that spoon in front of me.”
Rutherford seemed to have profoundly personal feelings towards all the unseen inhabitants of the submicroscopic world. When in 1932 his student James Chadwick discovered the neutron that (the now knighted) Rutherford had predicted and Bohr gladly recognized the reality of the newborn neutral particles, Sir Ernest in his answer cordially thanked the Dane as it there were a newborn in the Rutherford family. It took 10 years to establish the main properties of his favorite alpha particles. Their mass is four times that of the Hydrogen atom. Their charge is positive and twice that of the electron: +2. Their velocity when they escape a radioactive atom is ten to twenty thousand kilometers per second. They have the same chemical properties as the Helium which was first discovered in the sun spectra and only years after that on Earth…
[10 years of work! In today’s laboratories all these data could be collected in a month — if not in a day.]
In the summer of 1906, Rutherford’s thoughts were stimulated by an unforeseen and almost unnoticeable event: a narrow beam of alpha particles that widened on having passed through a thin mica leaf. That is all that happened. A fraction of the alpha particles had deflected by two degrees from the perpendicular. Two degrees is nothing much to talk about. It was massive microbullets that were deflected and their velocities were enormous. But why?
[It takes astute awareness to even recognize and ask a question of a seemingly trivial event. Every event brings with it two things: something to be learned and an emotional response to it. Usually we hold onto the second and the first totally passes us by.]
[But why? Such a simple yet powerful question. It reminds me of a story in Surely You’re Joking Mr. Feynman, in the book it’s called the 7-percent solution. I am going by memory here but the story is that Feynman was working on a tough problem and he came up with a theory that brought the prediction to within 7% of the data. And he struggled with getting his theory fine tuned for better accuracy to agree with the measured data. One day he was discussing this with his (also physicist) sister and she asked him a question, “Which way?”. This question propelled Feynman towards the eventual answer!! Which way!! Is it 7% higher or 7% lower! That’s it. She asked the right question and the brilliant mind of Feynman latched onto the solution. We hardly ever ask the right question. Well, we’re hardly ever as brilliant as Feynman which is a bigger issue, but anyway.]
[I’ve heard many Spiritual Masters say the same thing: The Answer Usually Is In The Question]
Less than three years later, in 1909, Rutherford asked his student Ernest Marsden,
“See if you can get some effect of alpha particles directly reflected from a meta surface”.
In 1909, even Rutherford did not believe his own intuition. Direct reflection of alpha particles [the little beggars] from a thin leaf of metal foil meant that they returned back to the radioactive source!
“It was quite the most incredible event that has ever happened to me in my life. It was almost as incredible as if you had fired a 15-inch shell at a piece of tissue paper and it can came back and hit you.”
[This was Rutherford’s master stroke. He suggested conducting such a senseless experiment to Marsden who was then a barely twenty year old. Marsden was working as an assistant to an experienced scientist from Germany, Hans Geiger (of the Geiger counter fame). It would be tactless to suggest seemingly senseless work to an experienced scientist — a possible failure could harm his reputation. But it it quite another matter to give the job to somebody new, for whom a failure would soon be forgotten.]
[The sheer genius of Rutherford in the extreme sensitivity of adversely affecting someone’s reputation seems to have been lost in the annals of History.]
The efforts of young Marsden were not wasted. Soon Geiger eagerly started to help is assistant. About two years later, at the end of 1910 or the beginning of 1911, Geiger recalled a memorable day:
“One day Rutherford, obviously in the best of spirits, came to my room and told me that he now knew what the atom looked like.”
[Let this sink in for a moment. Rutherford, at the moment, was the only person in the whole wide world who had glimpsed past the veil of ignorance and decoded a secret of Nature. What an incredible understatement it is to say … “obviously in the best of spirits”!!
I remember the day when I finally cracked the problem of the so called phenomenon of observed Negative Rejection in Membrane Ultrafiltration. Best of Spirits you say??! I could not sleep that night. I was tossing and turning going over how I would write this up in a paper. The next day I was up at the crack of dawn. I literally sprinted to my office and wrote the first draft of a paper to Chemical Engineering Science in less than three hours flat! I remember that day; it was the 13th day of April, 1999 in the quaint city of Agen, France.]
Rutherford’s open model of the atom was a clear improvement over Thomson’s raisin-dough model. By the way, Rutherford first heard of the of the open atom model in a letter from Australia back in 1904. The letter was from his future friend William Bragg.
In the open atom, the negative electrons and still unknown carriers of positive charge should be at great distance from each other. To make a comparison with the solar system is easy. The majority of alpha particles would pass through the empty space without touching anything. In the submicroscopic world, the forces of gravity are negligibly small and electrical forces are paramount. Rutherford had estimated these forces when they found a deflection of the alpha ray by 2 degrees. But deflection by 180 degrees, “Terrifying forces must act inside the atom…” he repeated sometimes.
Rutherford’s model of the atom had a problem. The energy of the electron motion in the planetary motion must be continuously spent by the radiation to occur according to classical laws of electromagnetism. If it is so, the electron will inevitably fall into the nucleus. Rutherford understood that what he saw was a doomed atom.
In May 1911, Rutherford declared to all physicists from the pages of the Philosophical Magazine published in London t he knew what the atom looked like. But he warned at the beginning of the report:
“The question of stability of the atom proposed need not be considered at this stage…”
That meant: ‘Ladies and Gentlemen, I appreciate that my atom would not stand your criticism at the moment. It is doomed. But our science still has tomorrow as well as today!’ He ended his warning with the words:
“… the stability will obviously depend upon the minute structure of the atom and on the motion of the constituent charged particles.”
[What a stand-up chap! He knew what his critics would say and he totally disarmed them by recognizing their point of view right at the get-go.]
In the autumn of 1911, 23 outstanding physicists from Europe came together for the first Solvay Congress in Brussels. Of course Rutherford was also invited to that congress of 1911. A month and a half later he wrote to his friend William Bragg:
“I was rather struck in Brussels by the fact that continental people… do not worry their heads about the real cause of the thing.”
But the physicists who did not ‘worry their heads’ at the first Solvay Congress were Albert Einstein, Max Plank, Hendrik Lorentz, Henri Poincare, Marie Curie, Paul Langevin and Walther Nernst… Such a disparaging remark about this highbrow congregation indicates that the rabbit from the Antipodes was quite hurt.
Nothing happened in Brussels. It was half a year since the May issue of Philosophical Magazine had appeared but nobody said a word about the planetary model of the atom in Brussels. It looked as if it was one of those failures which are so clearcut and unforgivable that they pass tactfully unmentioned in the scientific community — particularly if a highly esteemed scientist has failed.
But one should say that almost nothing discussed at that congress in Brussels was beyond dispute or readily comprehensible. The theme considered was ‘Radiation and quanta’.
The new word ‘Quantum’ was introduced by Professor Max Planck.
… To be Continued
[Oh ya… for the Medium uninitiated, please leave a couple of “claps” below if you like this and would be interested in the subsequent part(s). Thanks.]
