Rutherford, Ernest, 1st Baron Rutherford of Nelson and Cambridge

Rutherford, Ernest, 1st Baron Rutherford of Nelson and Cambridge (1871-1937), British physicist, who became a Nobel laureate for his pioneering work in nuclear physics and for his theory of the structure of the atom.

Rutherford was born to a Scottish father and an English mother in Nelson, New Zealand, on August 30, 1871, on a small homestead in simple surroundings. His father was a farmer prepared to undertake skilled handiwork, such as wheelwrighting, and later operated a ropewalk; his mother was a schoolteacher. At 16, Rutherford went on a scholarship to Nelson College, where he shone in mathematics, and in 1889 he won a scholarship to Canterbury College, Christchurch, then one of the constituent colleges of the University of New Zealand. In 1893 he took a double first in mathematics and mathematical physics, and showed his future flair in experimental work by studying the magnetization of iron in a rapidly alternating magnetic field, and developing a sensitive magnetic detector of (Hertzian) radio waves. In 1895 he left New Zealand with an 1851 Exhibition Scholarship to the University of Cambridge. His award went initially to another student who, luckily for Rutherford and for the history of physics, could not take up the scholarship. Rutherford’s move to the Cavendish Laboratory, in Cambridge, had been made possible by a recent change in the university’s regulations that allowed graduates from other universities to obtain a degree by doing research there: the first to take advantage were Paul Langevin and Rutherford.

At the Cavendish Laboratory, Rutherford at first continued his New Zealand work. His magnetic detector, now part of a frequency meter, was exhibited at the laboratory in 1896. His work on the detection of radio waves was in advance of Guglielmo Marconi, but Rutherford decided to switch to the exciting new study of radioactivity, discovered in 1896 by the French physicist Antoine Henri Becquerel. He found that the “Becquerel rays” were different from the X-rays of Wilhelm Roentgen, as they consisted of two main types, which he named alpha and beta particles. In 1898, Rutherford was appointed research professor of physics at McGill University, Montreal. He stayed there for nine intensively fruitful years that culminated in his Nobel Prize for chemistry in 1908.

In 1899, Rutherford discovered a radioactive gas, later to be named radon, but his most important work was in nuclear physics. His main associate was the chemist Frederick Soddy. This resulted in Rutherford’s “disintegration” theory in 1902 in which he postulated that in the course of emitting alpha and beta particles, atoms of one element were spontaneously disintegrated into the atoms of another radioactive element of lower atomic weight. His findings were initially received with extreme scepticism. Rutherford took up the physics chair at the University of Manchester in 1907, and stayed there until 1919. Two of the physicists that joined his team were Hans Geiger and Niels Bohr. Rutherford and Geiger devised the first version of the Geiger counter to count the number of alpha particles and other ionizing radiation. In 1911, Rutherford put forward his nuclear model of the atom in which he proposed that almost all of its mass was concentrated in a nucleus, but this model was still based on classical electrodynamics. The application of quantum physics by Bohr resulted in the Rutherford-Bohr model in which the electrons were placed in stable circular orbits (energy states) around the atomic nucleus. This model was further modified in 1926 by Erwin Schrödinger, who by applying wave mechanics replaced Bohr’s well-defined orbits with probability “clouds”, also known as “orbitals”.

When World War I began, the physicists from Rutherford’s team volunteered for war work. One of them, A. B. Wood, would become one of the navy’s chief scientists after the war in the then newly established Royal Navy Scientific Service. Rutherford joined a civilian group working for the Admiralty developing acoustic methods for detecting submarines, and in 1916, with William Henry Bragg, patented a hydrophone (an underwater microphone). Rutherford also suggested the development of piezoelectric transducers for active ultrasonic echo-ranging, which eventually became sonar submarine detection in World War II.

In 1919, Rutherford was appointed director of the Cavendish Laboratory, at Cambridge. In one of the epochal experiments in nuclear physics, he bombarded nitrogen gas with alpha particles and obtained atoms of an isotope of oxygen as well as protons. This transmutation of nitrogen into oxygen was the first artificially induced nuclear reaction. It inspired intensive research into nuclear transformations and into the nature of radiation. In 1920, Rutherford predicted the existence of the neutron, which was discovered by James Chadwick in 1932. Also in 1932, John Cockcroft and Ernest Walton used a high-voltage accelerator to split the atom artificially by means of highly accelerated protons (the nuclei of hydrogen atoms). In 1934 nuclear fusion was achieved for the first time by Rutherford when by bombarding deuterium (heavy hydrogen) with deuterons he produced tritium (H³, the third isotope of hydrogen) and the light isotope of helium (He³). This breakthrough was based on the theoretical work of George Gamow, who argued that according to wave mechanics lower energies would be more efficient at splitting the atomic nucleus.

Rutherford was elected a fellow of The Royal Society in 1903 and served as its president from 1925 to 1930. Apart from the Nobel Prize, he received many honours. He was knighted in 1914 and created a baron in 1931. He died in London on October 19, 1937, and was buried in Westminster Abbey. The rutherford, a unit of radioactivity, was named in his honour. The unstable chemical element with the atomic number 104 is named Rutherfordium.

Rutherford published several books: Radioactivity (1904); Radioactive Transformations (1906), which constituted his Silliman Lectures at Yale University; Radiation from Radioactive Substances (1930), with James Chadwick and Charles Drummond Ellis, which became a standard text; The Electrical Structure of Matter (1926); The Artificial Transmutation of the Elements (1933); and The Newer Alchemy (1937).