Ernest Rutherford: father of nuclear science

Commemorated on the New Zealand $100 note, Ernest Rutherford was responsible for a series of discoveries in the fields of radioactivity and nuclear physics.

Ernest Rutherford (1871 - 1937) discovered alpha and beta rays, set forth the laws of radioactive decay, and identified alpha particles as helium nuclei. Most importantly, he postulated the nuclear structure of the atom. Experiments done in Rutherford's laboratory demonstrated that when alpha particles are fired into gas atoms, a few are violently deflected, implying a dense, positively charged central region containing most of the atomic mass.

Early life

Ernest Rutherford was born on August 30 1871 in the South Island city of Nelson. He was the fourth child in a family of 12. His father James Rutherford was a Scottish wheelwright and his mother, Martha, an English schoolteacher.

Rutherford received his early education in public schools, gaining a university scholarship in 1889. He graduated from the University of New Zealand in 1893 with an M.A. including a double first in mathematics and physical science. In 1894, he was awarded an 1851 Exhibition Science Scholarship, enabling him to go to Trinity College, Cambridge, as a research student at the Cavendish Laboratory under J.J. Thomson.

In 1898, he moved to Canada to take up the Macdonald Chair of Physics at McGill University, Montreal, where he did the work which gained him the Nobel Prize in Chemistry 1908.

In the summer of 1900 he travelled to New Zealand to visit his parents and marry Mary Newton. When his daughter Eileen, their only child, was born the next year, he wrote to his mother "it is suggested that I call her ‘Ione' after my respect for ions in gases."

Contributions in Physics

Rutherford was one of the first to design highly original experiments with high-frequency, alternating currents. His second paper, Magnetic Viscosity, contains a description of a time-apparatus capable of measuring time intervals of a hundred-thousandth of a second.

At Cambridge Rutherford's talents were soon recognised by Professor Thomson. He invented a detector for electromagnetic waves. He worked with Thomson on the behaviour of the ions observed in gases which had been treated with X-rays, and on the mobility of ions in relation to the strength of the electric field. In 1898 he reported the existence of alpha and beta rays in uranium radiation and indicated some of their properties.

In Montreal, his work on radioactive bodies, particularly on the emission of alpha rays, was continued in the Macdonald Laboratory. With R.B. Owens he studied the "emanation" of thorium and discovered a new noble gas, an isotope of radon, which was later to be known as thoron.

From 1900 till 1903 he was joined by Frederick Soddy (Nobel Prize in Chemistry 1921) where they collaborated on research into the transmutation of elements. Ernest Rutherford had demonstrated that radioactivity was the spontaneous disintegration of atoms. He noticed that a sample of radioactive material invariably took the same amount of time for half the sample to decay — its "half-life" — and created a practical application for this phenomenon using this constant rate of decay as a clock, which could then be used to help determine the actual age of the Earth which turned out to be much older than most scientists at the time believed.

Rutherford returned to England in 1907 to become Langworthy Professor of Physics in the University of Manchester. There he did the experiments along with Hans Geiger and Ernest Marsden (Geiger-Marsden experiment) that discovered the nuclear nature of atoms.

It was his interpretation of this experiment that led him to the Rutherford model of the atom having a very small positively charged nucleus orbited by electrons.

He became the first person in 1919 to transmute one element into another when he converted nitrogen into oxygen through the nuclear reaction N(α,p)O.

In 1921, while working with Niels Bohr, Rutherford theorised about the existence of neutrons, which could somehow compensate for the repelling effect of the positive charges of protons by causing an attractive nuclear force and thus keeping the nuclei from breaking apart.

An inspiring leader of the Cavendish Laboratory, he steered numerous future Nobel Prize winners towards their great achievements. Under him, Nobel Prizes were awarded to Chadwick for discovering the neutron (in 1932), Cockcroft and Walton for splitting the atom using a particle accelerator and Appleton for demonstrating the existence of the ionosphere.

Awards and merits

Rutherford was knighted in 1914. He was appointed to the Order of Merit in 1925, and in 1931 he was created First Baron Rutherford of Nelson, New Zealand, and Cambridge. Amongst his many honours, he was awarded the Rumford Medal (1905) and the Copley Medal (1922) of the Royal Society, the Bressa Prize (1910) of the Turin Academy of Science, and honorary doctorates from several universities worldwide.

Rutherford's chief recreations were golf and motoring.

He died in Cambridge England on October 19, 1937. His ashes were buried in the nave of Westminster Abbey, close to the tombs of Sir Isaac Newton and Lord Kelvin.

Lord Rutherford’s portrait is on the New Zealand 100 dollar note.