First Atom Split
Ernest Rutherford became the first person to artificially split the atom at Cambridge
April 01, 1917
The Experiment That Changed Physics
On April 14, 1932, British physicists John Cockcroft and Ernest Walton became the first people to split the atom artificially. Working at the Cavendish Laboratory in Cambridge, they built a particle accelerator and used it to fire protons at lithium atoms. The result was exactly what nuclear theory had predicted: the lithium atoms broke apart, releasing energy. The experiment confirmed Einstein's famous equation E=mc², proving that mass and energy are interchangeable.
What Splitting the Atom Actually Means
An atom is the smallest unit of a chemical element. For centuries, scientists believed atoms were indivisible — the word "atom" comes from a Greek word meaning uncuttable. When Cockcroft and Walton proved that atomic nuclei could be broken apart, it opened an entirely new field of physics. Scientists began to understand that the forces holding atomic nuclei together contained vast amounts of energy that could, in theory, be released.
From Lab Experiment to World-Changing Technology
The splitting of the atom set in motion a chain of discoveries that led to nuclear reactors and nuclear weapons within just over a decade. The Manhattan Project, launched in 1942, used this science to build the first atomic bombs. Cockcroft and Walton received the Nobel Prize in Physics in 1951. Their experiment is one of the most consequential moments in scientific history — a discovery made in a basement laboratory that reshaped the entire 20th century. Learn about the first nuclear power plant that followed.