When Hans Geiger and Ernest Marsden direct alpha particles at a thin gold foil, the expectation is that almost all of them will pass straight through. Most do. But a small number deviate sharply, and some particles return back. The result overturns ideas about the atom and makes Ernest Rutherford one of the most important scientists of the 20th century.
He died on October 19, 1937, in Cambridge, at the age of 66. His ashes were interred in Westminster Abbey, near the graves of Isaac Newton and Lord Kelvin.
From a New Zealand farm to Cambridge
Rutherford was born on 30 August 1871 in Spring Grove, now Brightwater, New Zealand. He was the fourth of 12 children in a family in which his father worked as a coachman and farmer, and his mother was a teacher. As a child, Ernest helped on the farm, but received a good education and won a scholarship to the University of New Zealand.
In 1894, he went to England on a research scholarship to the Cavendish Laboratory in Cambridge. There he worked under the supervision of Joseph John Thomson, who a few years later would be awarded the Nobel Prize for the discovery of the electron. Rutherford quickly established himself with his experiments on radioactivity.
The Nobel Prize is just the beginning
In 1908, Rutherford received the Nobel Prize in Chemistry for his research on the decay of elements and the chemistry of radioactive substances. The distinction is a kind of paradox for a man who would later go down in history primarily as the father of nuclear physics.
In his early research, he distinguished between two types of radiation, which he called alpha and beta rays. His work with radioactive substances also helped formulate the idea that radioactive decay proceeds in a regular manner. In his Nobel lecture, Rutherford wrote: “We can confidently conclude that the alpha particle is an ejected helium atom.“
The moment when the atom turns out to be almost empty
The experiment with metal foil, carried out in 1909 under Rutherford's leadership, showed something unexpected: the atom is not uniformly filled with positive charge, as the then-current model suggested. In 1911, the scientist proposed a new explanation - almost all the mass and positive charge are concentrated in an extremely small nucleus, and the rest of the atom is almost empty space.
Later, Rutherford described his surprise with the image of an artillery shell fired at a sheet of paper and returning to the shooter. It is the rare deviations, not the many particles that pass through, that reveal the structure of matter.
The teacher of the next generation
In 1917, Rutherford observed the first artificially induced nuclear reaction by bombarding nitrogen with alpha particles. The result led to the identification of the proton, and in 1919 he published his detailed study.
From 1919, Rutherford directed the Cavendish Laboratory. There, his students and collaborators made further decisive strides: James Chadwick discovered the neutron in 1932, and John Cockcroft and Ernest Walton succeeded in artificially causing the splitting of an atomic nucleus. Thus, the legacy of the New Zealand physicist continues to develop even after his death.
Sources: aps.org, sciencenews.org, apnews.com