Ernest Rutherford

Summary

Ernest Rutherford, First Baron of Nelson Rutherford, OM, PC, FRS, PRS (30 August 1871 Spring Grove, New Zealand – 19 October 1937 Cambridge, England, United Kingdom) was a British physicist born in New Zealand.

Rutherford was given the opportunity for education from childhood and used it to succeed in his studies. He did his own research while still a student and was accepted into his first research group as a postgraduate student at the University of Cambridge, England. This was the beginning of the physicist”s research into radioactivity. These continued throughout his life at various universities around the world, producing major achievements.

Among the great discoveries in physics, he is credited with the discovery of the atomic nucleus in an experiment now known as the Rutherford experiment. He studied radioactivity and was the first to introduce the terms alpha, beta and gamma radiation. Rutherford was the first to discover that half of radioactive material decays in a constant time (half-life). Rutherford also discovered the proton and hypothesized the existence of uncharged particles, neutrons, in the atom. Rutherford was awarded the Nobel Prize in Chemistry in 1908 for his research on the chemistry of radioactive elements.

Ernest was born in Spring Grove, New Zealand, on 30 August 1871. Ernest”s father, James Rutherford, and mother, Martha Thompson, had both emigrated with their parents to New Zealand in the mid-19th century, father James from Scotland at the age of 4 and mother Martha from England at the age of 13. Ernest was born into a middle-class family. According to various sources, his father worked as a farmer and flax miller during his lifetime and also ran his own sawmill, where the young Ernest also worked extensively. Ernest was surrounded by hard-working people with good technical skills. His father also repaired and maintained machinery and parts for various mills. His mother was a teacher who taught all her children to read and write. There were 12 children born into the Rutherford family, five girls and seven boys. Ernest was the fourth child and the second eldest son. Three of Ernest”s brothers died in infancy, one at birth and two were sadly drowned on a family trip. This led to Ernest”s mother”s depression, from which she never recovered during her lifetime.

The Rutherford children all received a good education because their parents valued education. The parents” appreciation was because father James never had the opportunity and mother Martha did. His mother believed that ”all knowledge is power”. Ernest spent his school years in the country schools of the place where he lived until 1886 (Foxhill Primary School 1876-81, Havelock Primary School 1882-86). He received his first science book from school at the age of 10. In the same year, Rutherford built his own miniature cannon, which fortunately exploded without causing any damage.

Years of study

In 1887, on his second attempt, 15-year-old Ernest was awarded a Marlborough Board of Education scholarship to Nelson College, a private secondary school. He moved away from home and studied successfully in all subjects, especially mathematics and science. While studying, he was a keen rugby player. After leaving school in 1890, again on his second attempt, Ernest succeeded in gaining a scholarship to Canterbury College in Christchurch, one of four New Zealand universities. At Canterbury, Rutherford was fortunate to be taught by brilliant professors who really got him interested in scientific research. During his three-year degree, he studied Latin, French and mathematics. In 1892 he graduated (Bachelor of Arts) in mathematics, applied mathematics, Latin, English, French and physics. Thanks to his excellent grades, he was awarded a scholarship for one year of postgraduate studies (“Honours” year). During this additional year, Mr Rutherford completed a Bachelor of Science in Geology and Chemistry. He also studied further mathematics and physics while carrying out independent research, focusing mainly on the theory of electricity and magnetism. His main research at that time was on high-frequency magnetic induction and magnetic viscosity of iron and steel, on which he also published his first papers. During his research he also developed some new physics devices, including a detector for fast current pulses. It was around this time that he met and fell in love with Mary Newton, the daughter of the owner of the flat where he was studying.

As a postgraduate student at university

After university, Rutherford”s ambition was to become a researcher at the Cavendish Laboratory at Cambridge University in England. His wish was fortunately fulfilled when James Maclaurin, one of the other applicants, turned down the post because he did not agree to the terms of the scholarship. So Rutherford left New Zealand for England and became the first postgraduate to graduate outside Cambridge (1895-98). Thus Rutherford began his research work with Professor J.J. Thompson”s research group at the Cavendish Laboratory, University of Cambridge. As an ambitious graduate student, he was the first to successfully transmit and receive electromagnetic waves. In his research, he succeeded in transmitting electromagnetic waves over a distance of half a mile, a world record at the time. In addition to showing that an oscillatory discharge magnetised iron, Rutherford discovered that a magnetised needle lost its magnetism in a magnetic field produced by an alternating current. This made the needle a detector of electromagnetic radiation, a fact that had also been discovered at the same time by the German physicist Heinrich Hertz in his laboratory. Rutherford”s results were simpler and had more commercial potential. When Rutherford heard about the discovery of X-rays by the German Wilhelm Röntgen, he was happy to move on, at J.J. Thompson”s request, to study the effect of X-rays on the conduction of electricity in gases. Thompson and Rutherford”s studies led to the observation of ionisation, the decomposition of atoms and molecules into positive and negative parts (ions) and the attraction of these charged particles to opposing electrodes. Rutherford”s research also focused on ion-producing radiation, ultraviolet radiation and radiation emitted by uranium. Rutherford discovered that the radiation emitted by uranium was much more complex than previously thought. He soon began to understand the concept of radioactivity, which became his main interest and hence his life”s work. In 1898, he discovered that radioactive atoms, in his research uranium atoms, emit two types of radiation. He named them alpha (α) and beta (β) radiation. Very soon, beta radiation turned out to be fast electrons. For several years thereafter, scientists focused their attention on studying alpha and beta radiation. In addition to his research work, he and J.J. Thompson were able to attend meetings of the Royal Society and the British Association. This gave him the opportunity to share his research results and demonstrate his talent, and he left a lasting mark on the University of Cambridge.

Research and achievements in universities

McGill University, Montreal, Canada (1898-1907)

University of Manchester, England (1907-19)

University of Cambridge, Cavendish Laboratory, England (1919-1937)

In 1898, Rutherford took up a professorship at McGill University in Montreal, Canada (1898-1907), which had well-equipped laboratories and so Rutherford moved across the ocean. He recruited a young chemist, Frederick Soddy, to assist him in his research, and a graduate student, Harriet Brooks, as his assistant. With their help, he demonstrated the mystery of radioactive decay: atoms of some elements spontaneously decay into atoms of lighter elements. This was one of the breakthroughs of his career. After discovering that the final decay product of uranium is lead, Rutherford realised that by measuring the relative proportions of uranium and lead in minerals and the rate of decay of uranium atoms, the age of minerals could be determined. Radioactive dating of soil samples is still an important part of geological research today. As a result of studies on the decay of heavy elements, the concept of half-life, the time it takes for half of the atomic nuclei of a radioactive substance to decay into other atomic nuclei, was developed.

Between 1902 and 1903, Rutherford and Soddy developed the theory of decay as an explanation for radioactivity, which is considered Rutherford”s greatest achievement at McGill University. In alchemy and transition element theory, atoms were considered to be stable, but Rutherford and Soddy argued that radioactive energy came from within the atom and that the spontaneous emission of alpha and beta particles marked the chemical transformation of atoms from one element to another. The overwhelming evidence from experimental studies stifled the doubters. Rutherford thought that the alpha particle was the major contributor to this chemical change because of the concrete mass of the alpha particle. He identified a positive charge on the alpha particle, but could not yet determine whether it was a hydrogen or helium ion.

During his time at McGill University, Rutherford took on more and more research students, including women, of whom there were few at the university at the time. She was a sought-after speaker and journalist. He was elected a Fellow of the Royal Society of Canada in 1900 and of the Royal Society of London in 1903. He also wrote the most important textbooks on radioactivity during this period. His first book Radioactivity was published in 1904. He was awarded grants, medals and many job offers. Later, in 1908, he was awarded the Nobel Prize in Chemistry for his research on the decomposition of elements and his chemical results on radioactive substances. A bewildered Rutherford often told friends that the fastest change he knew of was his transition from physicist to chemist.

In 1900, Rutherford returned briefly to New Zealand to marry his beloved Mary Newton. Their only child Eileen was born in 1901. The couple visited New Zealand in 1905 to renew ties with their families.

Rutherford never wanted to stay still for long and he often had new alternative possibilities in mind. North America had a good scientific community, but the centre of terrestrial physics was in Europe. England attracted him again. England was closer to the main centres of science and had both more and better graduate students. In 1907, when Rutherford was offered the post of head of the University of Manchester, he accepted.

At the University of Manchester, Rutherford refocused his research on alpha, beta and gamma radiation and how these types of radiation could provide new insights into the nature of atoms. He left radiochemistry to other scientists and returned to physics. Rutherford succeeded in proving in his physical studies what he had long suspected. The alpha particle was a helium atom without its electrons. However, he wanted better evidence to support his findings and carried out several new experiments with his research team. Together with Hans Geiger, Rutherford developed an electrical detector, the “electrometer”, to detect ionised particles. With this instrument he was able to determine experimentally important physical constants, including the Avogadro constant. Later, Geiger completed with Walther Mϋller an instrument for measuring radioactivity, the Geiger (Mϋller) tube, which is still a universal instrument for measuring radioactivity today. Rutherford, under Geiger”s guidance, commissioned his young student Ernest Madsen to measure the relative number of alpha particles with respect to the scattering angle and to determine whether any alpha radiation would be reflected back from the metals (now known as the Rutherford experiment). Madsen found that some of the alpha radiation was reflected back from the metals and even directly back from the thin gold film. This result surprised even Rutherford a little. From these results, he concluded in 1911 that almost all the mass of an atom is concentrated in its tiny nucleus, which is 1,000 times smaller than the atom itself, and so most of the atom would be empty space. The nucleus of the atom had been discovered. This second great discovery by Rutherford gave him lasting fame. In 1912, the Danish physicist Niels Bohr visited Rutherford”s laboratory and a year later demonstrated the importance of Rutherford”s findings. Bohr proved that radioactivity originated in the nucleus of the atom and chemical properties in the electrons orbiting the nucleus. He used Rutherford”s quantum idea to create an orbital model of the electrons in the atom. Thus a new atomic model was created. Rutherford and Bohr”s atomic models are still in today”s chemistry and physics textbooks. In addition, Rutherford scattering is still used to aid microelectronics devices used to detect nuclear particles and atomic orbitals.

In the year of the outbreak of World War I (1914-1918), Rutherford was knighted. During the war, he conducted research for the government, developing acoustic methods for detecting submarines. This information was then shared with the Americans. At the same time he tried unsuccessfully to persuade young scientists that it would be better to use them to develop and research wartime challenges rather than have their lives and scientific talent destroyed in the trenches. Towards the end of the war in 1917, Rutherford returned to the practice of atomic science. While bombarding light atoms with alpha radiation, Rutherford noticed that the resulting ejected particles had a higher energy than the alpha radiation and guessed that the particles were hydrogen nuclei (protons H+). From this observation, he concluded that the bombardment had also converted nitrogen atoms into oxygen atoms. He had therefore succeeded in using alpha particles (He2+) to convert an element into another element in a nuclear reaction. Rutherford thus became the world”s first successful alchemist and the first to split the nucleus, giving him a lasting scientific reputation. These findings were published after the war in 1919.

After the war in 1919 he returned to his university research roots and had the honour of filling the post of Professor of Experimental Physics at Cambridge and the post of Director of the Cavendish Laboratory, succeeding the famous Sir J. J. Thomson. His time was now also taken up with administrative duties, so he no longer had as much time to concentrate on research as before.

Rutherford invited James Chadwick, a graduate student from Manchester, to join him in Cavendish to continue their joint research. In laboratory experiments they bombarded light atoms with alpha radiation, causing changes in their structure, but they failed to penetrate the nuclei of heavier elements with alpha radiation. The mutual charges between the alpha radiation and the nuclei of the heavier atoms seemed to repel each other. In addition, they could not determine whether the alpha particle was reflected back, or whether it merged with the nucleus to be bombarded anyway. Eventually, in the late 1920s, advances in ecotechnology made it possible to resolve these questions. Meanwhile, in his first decade as a university professor and laboratory director, Rutherford”s main focus was on setting up first-class research groups. He proved to be a humane and supportive leader who made sure that students took credit for the research he mentored. He campaigned at the university for women to have the same rights as men.

In 1925, Rutherford travelled for the last time, to Australia and New Zealand. During his six-week visit to New Zealand he gave several public lectures. Wherever he lectured, he received a respectful reception. The halls were packed with people who wanted to hear him talk about the structure of the atom. Rutherford declared that he had always been proud to be a New Zealander. He expressed his support for education and research and recommended that scientific research be done that would benefit farmers. As a result of his support, an Institute of Scientific and Industrial Research was established in New Zealand in 1926. During his visit to New Zealand, he also spent time supporting his ailing parents.

The Rutherfords” only daughter Eileen was married to Ralph Fowler, a mathematical physicist at Cavendish Laboratory. They had four children, all of whom were highly educated. Sadness fell on the Rutherford family when Eileen died of a blood clot in 1930, aged just 29, nine days after the birth of her youngest child and just two days before Christmas 1930. On New Year”s Day that year, Rutherford was created a baronet, Baron Rutherford of Nelson, but this honour was overshadowed by the sadness of her daughter”s death.

As technology developed, the 1930s was the golden age of Rutherford”s research teams. In 1932, James Chadwick discovered the neutron, demonstrating that the nucleus was composed of protons and neutrons. Rutherford had predicted the existence of the neutron a decade earlier and guided Chadwick in his research by telling him what properties the neutron should have. In the same year, John Cockcroft and Ernest Walton succeeded in splitting the lithium atom by bombarding it with protons, the nuclei of the hydrogen atom, accelerated to very high speeds by a high-voltage accelerator. The lithium atom split into two alpha particles. The pair were later awarded the Nobel Prize in Physics in 1951 for their work.

After the invention of the cloud chamber (by English physicist Charles Wilson, Nobel Prize in Physics in 1927), visual evidence of what actually happened in collisions was obtained. The English physicist Patrick Blackett used the cloud chamber to study 400 000 alpha particle collisions and found that most of them were ordinary elastic collisions. However, some of the collisions did result in decay. In these, alpha radiation penetrated the nucleus of the target ion, after which the nucleus split in two. This was a very important step in understanding nuclear reactions and Blackett was awarded the Nobel Prize in Physics in 1948 for his results. A great scientific era had begun under Rutherford”s guidance. Years earlier, Rutherford had assumed that to penetrate the nucleus of an atom would require particles accelerated by a few million volts to match the energy of the particles removed from the radioactive atom. To this end, for years he pressed his country”s industry to develop high-voltage sources. However, George Gamow and Norman Feather, in their own research, made a discovery which showed that lower-energy particles were more effective at penetrating the nucleus of the atom. Rutherford commissioned a low-voltage particle accelerator with a much better particle flow. As a result, Gilbert Lewis was able to experiment with heavier hydrogen, deuterium and tritium, and light helium (He-3). As a result, in 1932 Rutherford, Australian physicist Mark Oliphant and German chemist Paul Harteck collaborated to achieve the first fusion reaction. They bombarded deuterium (2H) with deuterons (2H+) to produce tritium (3H). Rutherford hoped that nuclear fission, which could efficiently release energy from uranium, would not be discovered until humans could live in harmony with their neighbours. However, this was achieved only a few years after his death.

Epilogue

Rutherford had a few interests besides science, mainly golf and motoring. He was a liberal but not politically active, although he was a member of the Advisory Board of the Government Institute for Scientific and Industrial Research and Chairman of the Academic Auxiliary Council.

During his lifetime, Rutherford received many scientific awards and honorary doctorates in many countries, as well as grants from many societies and organisations. Several buildings have been named after him and he has appeared on postage stamps in four different countries and on New Zealand banknotes. The element rutherfordium is named in his honour.

Rutherford died in Cambridge at the age of 66 on 19 October 1937 from complications of hernia surgery and was buried in Westminster Abbey, London. Lady Rutherford retired to her old age in her native New Zealand in Christchurch, where she died in 1954.

“It was almost as unbelievable as bombarding tissue paper with 15-inch projectiles and having them bounce back and hit me.” (Rutherford said his experiment was the result of research that led to the discovery of the atomic nucleus.)

Publications

Sources

  1. Ernest Rutherford
  2. Ernest Rutherford