Resolution of the Rutherford Transmutation Myth by Steven B
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Resolution of the Rutherford Transmutation Myth by Steven B. Krivit / July 14, 2020 Copyright © New Energy Times 2020 For 85 years, a widespread myth existed, in textbooks and, later, on the Internet, about one of the most significant physics discoveries in the 20th century. By the 1910s, the old view that the atom was indivisible had been shattered: Scientists were learning that the atom contained even smaller components. One by one, the electron, proton, and neutron were discovered. Among many great accomplishments by New Zealand physicist Ernest Rutherford was an experiment that proved the existence of what he later named the proton. Soon after, an experiment took place that revealed that the centuries-old dream of alchemy was, in fact, possible. Man's desire to transmute one element into another was no longer relegated to the domain of scoundrels claiming to turn lead into gold. A scientist showed that, in fact, such transformations legitimately belonged to the domain of credible science. For 85 years, most of the science community believed that this discovery belonged to Rutherford. It did not. The credit goes, instead, to a research fellow working in his laboratory named Patrick Blackett. I am not the only person to have carefully read the original scientific papers and understood precisely what Rutherford and Blackett each did. But when I learned that most science historians recorded that history incorrectly, I decided to correct the myth. This is what happened. Eric Boyle, U.S. Department of Energy I am certain that an email I sent on March 13, 2017, to Eric W. Boyle, Ph.D., chief historian in the Department of Energy's Office of History and Heritage Resources, came as quite a surprise. I told him that a Web page that fell under his responsibility contained a significant historical error. I told him that the page said that one of the most famous physicists in history, Ernest Rutherford, had made the discovery of artificial transmutation of elements and that Rutherford had performed an experiment that transmuted nitrogen into oxygen. The page even included a portion of an Atomic Energy Commission-sponsored comic book reinforcing this idea. 1 I told Boyle that the experiment was actually performed by a research fellow named Patrick Blackett who was working in Rutherford's lab. (Blackett, 1925) The novel ability to deliberately transmute one element to another was a monumental event in the history of physics. Two decades earlier, researchers had observed that radioactive elements could spontaneously decay and leave behind a new element; this was transmutation by nature. But to have the power to deliberately transmute one element to another had significance greater by an order of magnitude; it signaled that, despite centuries of unscientific claims of transmutation by alchemists, a scientifically legitimate process for controlled transmutation existed. Moreover, these initial experiments planted the seed that, in less than a decade, blossomed into the new field of high-energy physics. Blackett's experiment was tedious and time-consuming, but when John Cockcroft and Ernest Walton built a new apparatus in 1932, they crossed the next threshold in transmutation research. Their apparatus allowed them to perform transmutations far more rapidly, by using artificially accelerated particles, and this device opened the door to high-energy physics. (Cockcroft and Walton, 1932) Thus, James Dacey, a science journalist with Physics World, was not understating the facts when he wrote, "Rutherford’s third big contribution was to effectively become the world’s first alchemist when he transformed nitrogen into oxygen." (Dacey, 2011) The only problem was that Dacey didn't know that the experiment had been performed by Blackett. This was not Dacey's fault, and the error on the Department of Energy page was not Boyle's fault, either. 2 From 1917 to 1919, while at the University of Manchester, Rutherford performed experiments in which he observed the emission of what he later named the proton. (Rutherford, 1919) He performed these experiments, made the correct observations, and published the results that unequivocally established him as the discoverer of the proton. Rutherford knew that the proton was ejected from the nitrogen nucleus when it was bombarded with a high-energy alpha particle. But he didn't know what underlying reaction mechanism had caused it. Rutherford made some guesses about the reaction, but they turned out to be wrong. We can only assume that he suspected a transmutation reaction was taking place, but he mentioned nothing about transmutation in the set of four papers he published in the June 1919 issue of Philosophical Magazine. These were the four papers in which he reported his discovery of what he shortly after named the proton. We know for certain that the following year, when he presented his Bakerian Lecture on June 3, 1920, he was thinking about transmutation, and he speculated that the reaction process traveled downward on the periodic table, leaving behind lighter elements. For example, Rutherford said that the residual nitrogen nucleus might have turned into carbon. (Rutherford, 1920) We know for certain that the following year, at the April 1921 Solvay Conference, Rutherford spoke about transmutation with his colleagues. One of his peers, physicist Jean-Baptiste Perrin, argued that the transmutation process would go upward on the periodic table, leaving behind heavier elements: Mr. Rutherford’s experiments seem to prove that we must reject that notion of a simple impact. The alpha projectile, due to its high velocity, and despite a very strong electric repulsion, can reach the immediate vicinity of the nucleus with its speed significantly reduced. At that moment, a “transmutation” takes place, probably consisting of an intranuclear rearrangement with the nucleus’ possible capture of the incident alpha (as we don’t know what becomes of it). (Perrin, 1921) After hearing what Perrin said, Rutherford tentatively agreed with him: "It could very well be that the alpha particle enters into some sort of temporary combination with the nucleus." Rutherford therefore had every reason to believe that transmutation reactions were occurring in these experiments. He also knew that the experiments he had performed at the University of Manchester using the scintillator detector had not provided the detail necessary to resolve the underlying mechanism and to 3 resolve the identity of the residual particle after the alpha-bombardment. But he knew which detector would do the trick: the Wilson cloud detector. Rutherford first assigned the task to Takeo Shimizu, a Japanese physicist working at the Cavendish laboratory, but when Shimizu had to return to Japan, Rutherford reassigned the project to Blackett. (Lovell, 1975) Three years ago, on March 14, 2017, I explained to Boyle the general idea of what had happened, and I sent him a PDF copy of Chapter 23 from my book Lost History. I also showed Boyle what Rutherford had written in 1925 when Blackett published his results: Since the proof that protons can be expelled from the nuclei of many light elements, the fate of the bombarding alpha particle after the disintegration has been a matter of conjecture. To throw light on this question, Blackett has recently photographed the tracks of more than 400,000 alpha particles in nitrogen. ... In these photographs, the fine track of the proton was clearly visible, and also that of the recoiling nucleus, but in no case was there any sign of a third branch due to the escaping alpha particle. He concluded that the alpha particle was captured in a collision which led to the ejection of a proton. ... These experiments suggest ... that the alpha particle is captured by the nucleus. If no electron is expelled, the resulting nucleus should have a mass 14 + 4 - 1 = 17 and a nuclear charge 7 + 2 - 1 = 8 — that is, it should be an isotope of oxygen. It thus appears that the nucleus may increase rather than diminish in mass as the result of collisions in which the proton is expelled. (Rutherford, 1925, 76, Studies) Blackett had detected the telltale particle tracks that informed him of the reaction mechanism and showed him that the reaction product was an isotope of oxygen. Blackett thus informed the scientific world of his discovery in his 1925 paper. Rutherford, in his experiments at Manchester, could not possibly have detected the evidence of transmutation or the reaction process because he had not used a detector capable of providing that information. Boyle responded to me the same day three years ago and made plans to take the matter seriously: Thank you for this thorough and conscientious reply and for all of the information and citations related to this history. I will analyze the matter with my colleagues, and if our conclusion is similar to your conclusion, we will make the corrections. As this is a website hosted by another unit within DOE, and in partnership with our Office of Classification, this 4 process will have to go through a couple of reviews before the changes are made. We will also be evaluating this page with a number of other pages so the review won't proceed until everything is ready for one bulk submission. It's difficult to predict how long this will take, but I would guess about 3-6 months. Six months later, on October 11, 2017, Boyle wrote back to me: "We’ve drafted some text for the revision of the website and thought we’d share it with you to get your feedback. ... Let me know what you think, and we’ll continue to move forward with trying to get things changed." I thought Boyle had done an exemplary job and wrote back, "I have read it carefully, and I cannot suggest a single improvement or correction." The revised page went live on October 30.