“In the light of [current research on atomic structure] the physicists have, I think, some justification for their faith that they are building on the solid rock of fact, and not, as we are often so solemnly warned by some of our scientific brethren, on the shifting sands of imaginative hypothesis.” – Ernest Rutherford
With the retirement of J.J. Thomson in 1919 from the Cavendish Laboratory, Rutherford was offered the job as head of the laboratory. During the negotiations with Rutherford, Thomson wrote to him, saying, “There is very keen hope that you may see your way to come to Cambridge. Nothing would give me more pleasure as to have my successor be my most distinguished pupil.” Returning to Cambridge would be a homecoming for the young man from New Zealand who had first walked the halls of the laboratory twenty-four years earlier as a colonial scholar. The Cavendish Laboratory was part of Cambridge University and was Great Britain’s premier physical sciences laboratory. It had been funded by the wealthy Cavendish family and was set up by its first director, the famous Scottish physicist James Clerk Maxwell. The end of the war had brought an onslaught of new students, who now numbered six hundred. Many were Americans wanting to resume their studies and get on with their lives after the awful war.
As his fame spread, Rutherford had many occasions to give public lectures. One such occasion was the 1920 Bakerian lecture at the Royal Society. In the lecture, he spoke of the artificial transmutations he had recently induced with assistance of alpha particles. He also gave a prediction regarding the existence of a yet undiscovered particle that resides in the atom: “Under some conditions it may be possible for an electron to combine [with a proton] much more closely [than in the case of a hydrogen atom], forming a kind of neutral doublet. Such an atom would have very novel properties. Its external field would be practically zero, except very close to the nucleus, and in consequence it should be able to move freely through matter…The existence of such atoms seems almost necessary to explain the building of the heavy elements.”
It would be a dozen years before Rutherford’s “neutral doublet,” or neutron, as it would be called, would be discovered. Rutherford’s second in charge at the Cavendish, James Chadwick, who followed him from Manchester, would take up the search for the elusive new particle. Chadwick’s road to discovery of the neutron was long and troublesome. The electrically neutral particle did not leave observable tails of ions as they passed through matter; essentially, they were invisible to the experimenter. Chadwick would take many wrong turns and go down many blind alleys on his quest for the neutron, telling one interviewer, “I did a lot of experiments about which I never said anything…Some of them were quite stupid. I suppose I got that habit or impulse or whatever you’d like to call it from Rutherford.” Finally, all the pieces of the nuclear puzzle fell into place and in February of 1932, Chadwick published a paper titled, “The Possible Existence of a Neutron.” Rutherford’s model of the atom was now in focus. At its core, that atom had positively charged protons, along with neutrons, and surrounding the core or nucleus were electrons, equal in number to the protons, that completed the outer shell of the atom.
At this point, Rutherford had become one of the most eminent scientists in Europe, making him a victim of his own success—little time for science and too much time spent in the tedium of administration and ceremony. As an elder statesman of science, he campaigned for Cambridge University to grant women the same privileges as men. He supported the freedom of the British Broadcasting Corporation from government censorship, served on its panel of advisors, and gave regular talks on science. As chairman of the advisory Council of the British Department of Scientific and Industrial Research, he advised the government on scientific matters and promoted the opening of additional research laboratories throughout the United Kingdom.
Rutherford had become an international scientific celebrity and while it was good for science in general, he found little time for his own research. In 1925, the year he was elected to a five-year term as president of the Royal Society, he made twenty separate appearances in England and turned down dozens of other possible speaking engagements. He produced only one paper longer than a page that year, none in 1926, and none in 1928. Though Rutherford’s own research diminished, work at the Cavendish was going full throttle. With Rutherford at the helm and Chadwick his second in command, they were able to attract the best and brightest young scientists, rebuild and expand the laboratories, and propel the students to achieve great advances. The list of Nobel Prize winners from the Cavendish that benefited from Rutherford’s guiding hand is long, with some of the notables being: Fredrick Soddy, 1921; Neils Bohr, 1922; Paul Dirac, 1933; Chadwick, 1935; John Cockcroft and Ernst Walston, 1951; and many more.
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Another young man who fell under Rutherford’s spell was the Russian Peter Kapitsa, the twenty-seven-year-old electrical engineer who had come to the Cavendish in 1921 as part of a Russian mission to buy laboratory equipment. After some convincing on the part of Kapitsa, Rutherford agreed to take him on as a researcher. The young Russian was part of the growing wave of “big science” researchers who were moving beyond the table top experiments to develop powerful industrial style tools to probe matter. Kapitsa’s area of interest was in the production of very high magnetic fields.
Kapitsa spent fifteen years with Rutherford, and the two developed a close friendship. Kapitsa made large electro-magnets that were capable of creating the most intense magnetic fields yet known. Unfortunately, little of scientific value came from his work with high magnetic fields. Kapitsa eventually shifted his work to the burgeoning area of the study of gases at very low temperatures, or cryogenics.
Kapitsa often traveled to Russia for reasons scientific and personal. On one such trip to his homeland, Soviet authorities decided to detain him. The Soviets wanted his skill as an engineer to bring modern electrical power technology to the Soviet Union. Rutherford spent months working the political scene to get Kapitsa back to the Cavendish. His efforts were futile, and it would be decades after Rutherford’s death before Kapitsa would be able to return to England to visit his old friends at the Cavendish.
Not long after Kapitsa had left England for good, Rutherford received a letter from Kapitsa’s wife, recounting the dismal state of her husband, saying, “If he did not commit suicide in Russia during the last year it was not for love of me or the children, it was only for love of you, not to let you down after all you did for him, after all the trust you put in him.” Rutherford repeatedly wrote his captive Russian colleague, encouraging him to get to work and telling him that being in a laboratory was his only hope. Kapitsa did just that; he accepted a position as director of Physical Problems of the Soviet Institute of Science. He would go on to accomplish great things in science. In 1978 he would be awarded a Nobel Prize in physics for his work in low-temperature research, which he had started at the Cavendish decades before.