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80 years on: the neutron

It was only 80 years ago – one human lifetime – that Sir James Chadwick discovered the neutron. PhysOrg has the story.

“In 1932, Chadwick’s work led him to the discovery of a previously unknown particle in the atomic nucleus that was crucial to the fission of uranium 235.

It became known as the neutron because it carries no electric charge, allowing it to split the nuclei of even the heaviest elements.

Current University physics Research Fellow, Dr. Peter Rowlands assesses Chadwick’s findings, 80 years on. He said: “The immediate impact was that it completed the understanding of the structure of both the atom and the atomic nucleus. It also made sense of isotopes or atomic species with the same chemical properties but different masses. And it provided a probe that was able to penetrate deeper into the nucleus because it was electrically neutral and so was not repelled like the positively charged alpha particle. Within a few years, neutrons had been shown to cause fission of certain nuclei with a release of large amounts of energy. This had momentous consequences both for the peaceful use of nuclear energy and for military application.””

Chadwick was one of the Manhattan Project scientists. The story of that project is well told in The Manhattan Project: The Birth of the Atomic Bomb in the Words of Its Creators, Eyewitnesses, and Historians. That book is a compendium of sources by an organization formed in 2002 to try to preserve Manhattan Project history. It is well worth reading to gain an insight into the social atmosphere of the time and the challenges that had to be overcome.

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