Ernest Marsden was born in Rishton, Lancashire, England, on 19 February 1889, the son of Phoebe Holden and her husband, Thomas Marsden, a cotton weaver. From his earliest schooldays Ernest showed unusual ability and won scholarships to Queen Elizabeth Grammar School, Blackburn, and then to Victoria University of Manchester.
He had begun the honours course in physics when in 1907 the professor, Arthur Schuster, altruistically resigned his chair in order to attract to the university a greater man: Ernest Rutherford. The New Zealander was at the height of his powers; as well as being a brilliant experimental physicist he was a boisterous, exuberant character with a rare gift to attract and inspire others in the scientific quest. Marsden was one of the first of a growing band of students and researchers drawn to work with Rutherford at Manchester.
In 1909, the final year of his degree course, Marsden was assigned to work with Rutherford's research assistant, Hans Geiger, to undertake experiments on the particles emitted during radioactive decay. They confirmed that the heavier, positively charged alpha particles passed straight through thin metal foils, but Rutherford suggested that Marsden check whether any were deflected back. Such an effect seemed impossible under current ideas of the structure of the atom, but when Marsden set up his experiment he found that a few of the alpha particles were indeed deflected right back. Rutherford was astonished and delighted at this unexpected result and after pondering on it for months he conceived his nuclear model of the atom, in which most of its mass is concentrated in a minute, positively charged central nucleus. The demonstration of large deflections of alpha particles, published by Geiger and Marsden in 1909, thus became recognised as one of the crucial experiments of twentieth-century physics and made their names known to scientists worldwide.
After he graduated BSc with first-class honours in 1909, Marsden gained a position as lecturer in physics at the University of London, but was soon drawn back to Rutherford's laboratory, becoming his research assistant in 1912 when Geiger left. With a succession of students they explored the new field of atomic physics. In 1914 Marsden was awarded a DSc for these researches. Though still Rutherford's devoted disciple (he was to remain so for the rest of his life), Marsden was now looking to his own career. A year earlier, on 4 August 1913 at Rishton, he had married Margaret Sutcliffe, an elementary-school teacher, and established a home in Manchester. In 1915 Marsden, on Rutherford's recommendation, was appointed professor of physics at Victoria University College in Wellington, New Zealand.
Ernest and Maggie Marsden arrived in Wellington in May 1915, but he waited only for the end of term and the birth of the first of their two children to volunteer for war service. In 1917 he was seconded to the Royal Engineers, joining other physicists in a special sound-ranging section that had been formed to use scientific methods to locate enemy guns. Marsden served in France to the end of the war, rising to temporary major and winning the Military Cross.
Back at Victoria University College Marsden became known as a lively and inspiring lecturer and also managed, despite the limited facilities there, to carry out research both in his familiar field of radioactivity and in some new topics of local interest. He also demonstrated considerable skill at finding the support and resources required for new projects. Within two years he had gained approval for a new physics wing at the college and building was under way. But for Marsden the excitement was always in the chase rather than the finish. He liked to initiate a new project and fire others with enthusiasm and ideas, and then leave them to carry it on. In 1922 he astonished his colleagues by relinquishing his professorial chair to take the position of assistant director of education.
In the Department of Education Marsden made particular efforts to improve technical and university education, and to introduce scientific methods, such as intelligence testing of secondary school entrants. He also remained very active in scientific circles, and was appointed to many inquiries and committees on both education and research. From 1921 he was a member of the Board of Science and Art, and in 1925 was secretary of the Royal Commission on University Education in New Zealand and chairman of a committee of officials reporting on scientific research for industry. Marsden was also an important local contact for the visiting experts from Britain who advised the government on reorganisation of science at this time: Rutherford (now Sir Ernest) and Sir Frank Heath, head of the British Department of Scientific and Industrial Research. When Heath's recommendations for co-ordination of research along the lines followed in Britain were adopted by the government, Marsden was an obvious choice to head the new structure. On the passing of the Scientific and Industrial Research Act in August 1926 he was appointed secretary of both the Council and the Department of Scientific and Industrial Research (DSIR).
Initially Marsden's main role was in co-ordinating and supporting research carried out in other institutions. Political and economic imperatives demanded that the main emphasis be on assisting primary industries, and within two years Marsden had successfully negotiated joint funding arrangements with industry groups to establish new dairy, wheat and leather research institutes. Other research investigations were supported by grants obtained from the Empire Marketing Board, which administered a fund established in 1926 by the British government in lieu of trade preferences promised to the dominions. Marsden was particularly successful in gaining such outside grants and using them to obtain matching government funding, but under the financial stringency of the 1930s this became a constant struggle.
Marsden was also responsible for the Geological Survey, Dominion Laboratory, Dominion Observatory and other research units that had been transferred to the DSIR from other departments. Not all government science had been transferred; the Department of Agriculture, in particular, retained its scientific staff, insisting that they had an advisory as well as a research role. However, Marsden gradually managed (with the help of agitation from some of the scientists, and the leverage of Empire Marketing Board funding) to bring its plant research under DSIR co-ordination. After the election of the Labour government in November 1935 he was able to expand the DSIR's role in undertaking state-funded research. Plant research was transferred entirely to DSIR control and reorganised into five new divisions. Other new divisions were formed by splitting off specialist units, for instance the Soil Survey Division (1936) and Plant Chemistry Laboratory (1938). He began moves to transfer animal research from the Department of Agriculture as well, but this particular campaign was lost after he became caught up in defence work.
This began early in 1939 when New Zealand was invited to send a physicist to Britain to be briefed on a secret new defence development. There were few physicists in the government service (Marsden had until now been unable to gain approval for a physical laboratory in the DSIR, but had contrived to appoint some promising young physicists to other divisions), and it was decided that only Marsden himself was senior enough for such a mission. He flew to London and joined other dominion scientific representatives being shown the new technology of radar. Quickly gaining an understanding of its technical principles and potential, Marsden recommended that rather than waiting on Britain for the supply of radar equipment, New Zealand should move to develop some of its own. He continued his round of the British defence laboratories, making contacts with old scientific friends and new ones, and wangling the necessary information, plans and components.
He returned to New Zealand shortly after war was declared and, leaving the routine administration of the DSIR to his deputy, F. R. Callaghan, set about organising a radar development programme along with a multitude of other scientific projects for the war effort. Many of these were in fields of physical science and engineering previously undeveloped in New Zealand, and they not only succeeded in meeting urgent wartime needs, but later provided the basis for the DSIR's assistance to postwar industrial development. Marsden, as always, was particularly effective in initiating new projects, picking the right people for the job and inspiring them with his ideas and enthusiasm. However, this enthusiasm sometimes led him to promise more than his scientists could deliver – or his authority allowed. In 1943 he persuaded the commander of allied forces in the South Pacific, Admiral W. F. Halsey, to make use of New Zealand radar there. His scientists worked miracles to produce the sets, but the New Zealand chiefs of staff were not pleased at having to supply the crews to man them.
During the war Marsden travelled frequently to Britain and the United States to keep in touch with developments in radar and other scientific and technological fields. He was inquisitive and persistent, and made full use of his connections with the many other Rutherford students who were now in key scientific positions in Britain and elsewhere. Through such contacts and his own understanding of developments in physics Marsden got wind of the secret British and American programme to develop an atomic bomb, and boldly suggested that New Zealand scientists could assist. In April 1944, when the British needed more scientists for their teams in the American Manhattan project and the smaller Anglo-Canadian project at Montreal, Marsden's offer was taken up, and a group of the ablest scientists and engineers from the radar programme were sent to join them. As with other wartime projects, he was alert to the potential postwar benefits of New Zealand involvement, and at the end of the war gained initial agreement to the establishment of an atomic energy research unit in the DSIR. But in 1947 when, with the support of his Rutherford connections in Britain, Marsden proposed building a reactor in New Zealand, the government was not convinced.
At this point Marsden made another of his unconventional career shifts. He now dominated New Zealand science to an extent unequalled since James Hector in the 1870s. In May 1947 he had been elected president of the Royal Society of New Zealand – and was thus at the head of both the department and the academy of science. However, his wartime work and lengthy travels abroad had introduced him to the higher circles of science in Britain, and had also distanced him from the growing pains of the DSIR, where he now faced a backlog of irritating problems and criticisms of his administration. In September Marsden persuaded his minister – without much difficulty – to let him step down as secretary of the DSIR and return to London to take a scientific liaison position there. Resuming a role rather like his wartime one, he became in effect an ambassador of science for New Zealand, making contacts and collecting information for scientific projects, and representing the country on international committees and conferences.
Although enjoying the brighter scientific lights in Britain, Marsden still remained attached to New Zealand. In 1954, when he reached 65, he returned to retire. He was still full of vigour and ideas, although his wife, Maggie, was ailing with heart disease; she died on 7 November 1956. Marsden remained busy on numerous advisory committees (including the DSIR's council), and returned to research on radiation. His contributions to science and New Zealand had been recognised by many honours, including a fellowship of the Royal Society of London in 1946, and in 1958 he was appointed Knight Bachelor. On 26 July that year at Eastbourne, Wellington, he married Joyce Winifred Chote, who was 30 years his junior. She assisted him in his researches and joined him on his travels. As the guest of research institutes around the world he continued investigations on natural radiation and its effects on human health. Vivacious, quick-thinking and approachable, he retained his exuberant enthusiasm and energy while becoming an elder statesman of science, honoured as one who had been there with Rutherford at the birth of nuclear physics.
A severe stroke in 1966 left him confined to a wheelchair, but he still maintained his contacts with local and international scientists. Ernest Marsden died at his home at Lowry Bay, Wellington, on 15 December 1970, survived by his second wife, Joyce, and a daughter and a son from his first marriage.