Sir James Chadwick


Sir James Chadwick
(1891-1974)

Born in Bollington, England. Intended to study math, but entered physics line by mistake in 1908, and ended up with a Master of Science from the University of Manchester, 1912. Thereupon he received a Research Student Fellowship, which led him to Berlin. There he worked with Geiger, whose famous Geiger counter Chadwick employed, within a few months of arriving, for an important discovery concerning the beta radiation spectrum, at age 23. This discovery was doubted by almost all physicists but (Rutherford and) Einstein,who found the discovery quite important and enigmatic, after Chadwick explained it to him in German. Chadwick was interned months later, after the start of WWI, throughout which he suffered from malnutrition, leaving him in poor health for much of the rest of his life. The Germans did allow him to continue his research, and he examined, among other things, German radioactive toothpaste. Liberated after the 1918 armistice, he was swiftly hired by Rutherford at the Cavendish Laboratory, Cambridge. There Chadwick succeeded in proving the correctness of Rutherford's theory, that an element's atomic number is equal to the charge of its nucleus, ie. that protons exist. He received his Ph.D. in 1921, and two years later was named the first ever Assistant Director of Physics Research, becoming the de facto Director as Rutherford aged. After a search lasting eight years he discovered the neutron in 1932, and, largely for this achievement, would always be known as the ideal experimentalist; Madame Curie's daughter might have preceded Chadwick in this, but she incorrectly interpreted her results. This discovery, while immediately seen to be important, has been particularly underrated from the standpoint of its timing, since subsequent history may have been quite different had the neutron been discovered even a year later than it was. Had the ensuring breakthroughs in nuclear physics, such as the creation of the first chain reaction, been likewise delayed even a year, the A-bomb might have been ready for use, non in August 1945, but in August 1946, too late to have been used against Japan. Without the memory of the horror of Hiroshima to deter war between the Soviets and the West, such a war probably would have occurred; one way or the other, such a war would have made the world a very different place than it is now.

In 1935 Chadwick left Cambridge for the University of Liverpool, where he used his Nobel Prize money to buy a cycletron, and, after the start of WWII, he explored the possibility of building an A- bomb; his motivation was a concern that the Allies would be naked if Heisenberg etc. could build a bomb for Hitler.

After the outbreak of WWII, he was chief advisor to the group of British officials weighing the option of investing much of Britain's limited resources in development of an atomic bomb. His reputation in the U.S. for cautious judgement was such that, when his "MAUD Report" reached the U.S., the report persuaded administration officials of the feasibility of a fission device even before Pearl Harbor. As the British official history later put it, in Spring 1941,U.S. officials "urged that Chadwick, with his great prestige, should go to America. 'Send Chadwick' was the call from Washington--a call that was to be repeated to great effect in 1943". H.M. Government preferred to retain Chadwick to keep alive the native bomb program in the U.K., a decision later regretted; by the time Chadwick arrived in the U.S, the need for his expertise and stature had become less desperate.

See

Brown, Andrew, The Neutron and the Bomb (Oxford, 1997) the first
(but major) biography of Chadwick;

reviews of this book include
Calder, Nigel, "The Accidental Physicist", New Scientist,
12 July 1997

Gowing, Margaret, Britain and Atomic Energy 1939-1945,
the official history of the British bomb effort
Groves, Gen. Leslie, Now It Can Be Told (Harper, 1962)
and
Lawren, William, The General and the Bomb: A Biography of
General Leslie R. Groves, Director of the Manhattan Project (Dodd,
Mead & Co., 1988)


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