Speaker
Description
The discovery of the neutron in 1932 represents a watershed moment in the history of modern physics, fundamentally altering our understanding of the atomic nucleus and the forces of nature. This contribution explores the historical evolution of the neutron concept, beginning with Ernest Rutherford’s 1920 Bakerian Lecture, where he first hypothesized a "neutral doublet" to resolve discrepancies in atomic mass and nuclear charge.
The analysis traces the experimental challenges of the 1920s and early 1930s, focusing on the pivotal roles played by Bothe and Becker’s "beryllium radiation" and the subsequent interpretations by Irène and Frédéric Joliot-Curie. While the Joliot-Curies observed the projection of protons from paraffin wax, they initially misidentified the radiation as high-energy gamma rays. It was James Chadwick’s rigorous experimentation and conservation-based reasoning at the Cavendish Laboratory that finally identified the particle as having a mass similar to the proton but no electric charge.
By examining primary sources and contemporary scientific debates, this contribution highlights the transition from a "proton-electron" nuclear model to the "proton-neutron" paradigm. This shift not only solved the "nitrogen anomaly" but also paved the way for the development of nuclear energy and the rise of "Big Science" in the mid-20th century.