James Chadwick

Biography

Sir James Chadwick (20 October 1891 – 24 July 1974) was a British experimental physicist known for discovering the neutron in 1932, a discovery that earned him the Nobel Prize in Physics in 1935. Born in Bollington, England, he became one of the most important scientists of the twentieth century, contributing to both nuclear physics and the development of atomic weapons. He passed away in Cambridge in 1974 after more than fifty years in his field.

Chadwick studied at the Victoria University of Manchester, graduating in 1911 under Ernest Rutherford, who is often called the father of nuclear physics. He continued his education there and earned his MSc in 1913. That year, he received an 1851 Research Fellowship, which allowed him to travel to Berlin to study beta radiation under Hans Geiger. With Geiger's new counter, Chadwick found that beta radiation produced a continuous energy spectrum, rather than distinct lines, a discovery important for atomic theory. His time in Germany was cut short due to World War I, during which he was held at the Ruhleben camp for nearly four years.

After the war, Chadwick went to the Cavendish Laboratory at the University of Cambridge with Rutherford, earning his Doctor of Philosophy degree from Gonville and Caius College in June 1921. He worked as Rutherford's assistant director of research at the Cavendish Laboratory for over ten years, during which the lab attracted top physicists globally. His major achievement came in 1932 when he proved the existence of the neutron, a neutrally charged particle in the atomic nucleus whose presence had been theorized but not confirmed. He also measured the neutron's mass and anticipated its potential medical use, especially in cancer treatment.

In 1935, Chadwick left Cambridge to become a physics professor at the University of Liverpool, where he upgraded the department and built a cyclotron. He played a vital role in wartime nuclear research, writing the final draft of the MAUD Report in 1941, which convinced the United States government to invest in atomic bomb development. He then led the British scientists working on the Manhattan Project during World War II. For his contributions to nuclear physics and the war effort, he was knighted in 1945. He married Aileen Maud Stewart-Brown, and they remained together for the rest of his life. Among his awards were the Hughes Medal (1932), the Copley Medal (1950), the Faraday Medal (1950), the Franklin Medal (1951), the Melchett Medal (1946), Fellowship of the Royal Society (1927), the Companion of Honour (1970), and the Pour le Mérite for Sciences and Arts.