Today we celebrate the life and work of New Zealand’s greatest scientist, Lord Ernest Rutherford – the father of nuclear physics. In the words of the author John Campbell, “He is to the atom what Darwin is to evolution, Newton to mechanics, Faraday to electricity and Einstein to relativity.”
Rutherford was responsible for three fundamental contributions to the field: (1) he explained radioactivity as the spontaneous disintegration of the atom; (2) he determined the structure of the atom; and (3) he was the first to split the atom.
Ernest Rutherford was born on 30 August 1871 in the South Island town of Nelson, New Zealand. His father James Rutherford, the son of a Scottish immigrant, came to New Zealand at the age of four, while his mother, Martha Rutherford (née Thompson) emigrated with her widowed mother from England when she was thirteen. The Rutherfords, in the words of dad James, wanted “to raise a little flax and a lot of children”. Not sure how they managed on the flax, but they certainly lived up to their aspirations in the children department – young Ernest was the second son, and fourth child, of no less than twelve Rutherford children.
Rutherford excelled academically, winning a scholarship to the Canterbury College of the University of New Zealand. After completing his basic university studies through the University of New Zealand, he successfully applied for another scholarship, which enabled bim to go to the UK to complete his postgraduate studies at the Cavendish Laboratory, University of Cambridge.
While working with Professor JJ Thompson, Rutherford discovered that radioactive uranium gave off two separate types of emissions – he named these alpha and beta rays. Beta rays were subsequently identified as high speed electrons.
Radioactivity and the spontaneous disintegration of the atom
In 1898 Rutherford accepted a professorship at McGlll University in Montreal, Canada. It was here, with the help of a young chemist, Frederick Soddy, that he conducted the research that gained him the 1908 Nobel Prize in Chemistry, investigating “the disintegration of the elements and the chemistry of radioactive substances”. (Soddy himself later received the 1921 Nobel Prize in Chemistry.)
Determining the structure of the atom
A subsequent move to Manchester, England, to be nearer to what he considered the main centres of science, saw Rutherford taking on a professorship at the Manchester University. With his research assistant, Ernest Marsden, he investigated the scattering of alpha rays (something he first noticed while still at McGill). They noticed some alpha rays would ‘bounce back’ when hitting even a thin gold film – this was a most surprising result, with Rutherford likening it to firing a large naval shell at a tissue paper, and seeing it bounce back. This led to him developing his concept of the ‘nucleus’, his greatest contribution to physics. According to this concept the whole mass of the atom, and all its positive charge, is concentrated in a miniscule point at its centre, which he termed the nucleus.
The Danish physicist Niels Bohr began working with Rutherford, and he adapted Rutherford’s nuclear structure to include electrons in stable formation around the nucleus. The Rutherford-Bohr model of the atom, with some improvements from Heisenberg, remains valid to this day.
Splitting the atom
In 1919, during his last year at Manchester, Rutherford noted that the nuclei of certain light elements, like nitrogen, would disintegrate when bombarded by alpha particles coming from a radioactive source, and that during this process fast protons were emitted. By doing this, Rutherford became the first person to split the atom. Patrick Blackett (winner of the 1948 Nobel Prize in Physics) later proved that splitting the nitrogen atom actually transformed it into an oxygen isotope, so Rutherford effectively became the first to deliberately transmute one element into another.
Rutherford received the knighthood in 1914; he was appointed to the Order of Merit in 1925, and in 1931 he was raised to the peerage as Lord Rutherford of Nelson. A proud New Zealander despite living and working abroad for most of his academic career, he chose to include in his coat of arms a Kiwi, a Maori Warrior and Hermes Trismegistus, the patron saint of knowledge and alchemists.
He died in Cambridge on October 19, 1937, leaving his wife Mary Newton, and only child Eileen.
A great scientist, Rutherford’s contribution is perhaps best summarised in his eulogy in the New York Times:
“It is given to but few men to achieve immortality, still less to achieve Olympian rank, during their own lifetime. Lord Rutherford achieved both. In a generation that witnessed one of the greatest revolutions in the entire history of science he was universally acknowledged as the leading explorer of the vast infinitely complex universe within the atom, a universe that he was first to penetrate.”