J. J. Thomson Dies: Electron Discoverer Who Revolutionized Physics

J. J. Thomson left behind the discovery of the electron, a finding that overturned the ancient belief that atoms were indivisible and launched the entire field of subatomic physics. His Cavendish Laboratory at Cambridge became the world's foremost training ground for physicists, producing seven Nobel laureates including his own son. Thomson's 1897 experiment with cathode rays demonstrated that atoms contained smaller, negatively charged particles, which he called "corpuscles" before the scientific community settled on "electron." The discovery was revolutionary because it dismantled the 2,400-year-old assumption, stretching back to Democritus, that atoms were the fundamental, indivisible building blocks of matter. Thomson proposed the "plum pudding" model, imagining electrons embedded in a positively charged sphere like raisins in a pudding. His student Ernest Rutherford would later disprove this model with the gold foil experiment, but Thomson's fundamental insight that atoms had internal structure opened the door to everything that followed: radioactivity, quantum mechanics, nuclear energy, and semiconductors. As director of the Cavendish Laboratory from 1884 to 1919, Thomson mentored a generation of physicists who won seven Nobel Prizes, an unmatched record of scientific mentorship. His own Nobel Prize came in 1906 for his work on gas conductivity. His son George Paget Thomson won the Nobel Prize in Physics in 1937 for demonstrating that electrons behaved as waves, making them the first father-son pair to win Nobel Prizes in the same discipline.