Ernest Rutherford

Ernest Rutherford, 1st Baron Rutherford of Nelson, was a New Zealand physicist and chemist who was a pioneering researcher in both atomic and nuclear physics. He has been described as "the father of nuclear physics" and "the greatest experimentalist since Michael Faraday." In 1908, he was awarded the Nobel Prize in Chemistry "for his investigations into the disintegration of the elements, and the chemistry of radioactive substances."
Rutherford's discoveries include the concept of radioactive half-life, the radioactive element radon, and the differentiation and naming of alpha and beta radiation. Together with Thomas Royds, Rutherford is credited with proving that alpha radiation is composed of helium nuclei. In 1911, he theorised that atoms have their charge concentrated in a very small nucleus. He arrived at this theory through his discovery and interpretation of Rutherford scattering during the gold foil experiment performed by Hans Geiger and Ernest Marsden. In 1912, he invited Niels Bohr to join his lab, leading to the Bohr model of the atom. In 1917, he performed the first artificially induced nuclear reaction by conducting experiments in which nitrogen nuclei were bombarded with alpha particles. These experiments led him to discover the emission of a subatomic particle that he initially called the "hydrogen atom", but later renamed the proton. He is also credited with developing the atomic numbering system alongside Henry Moseley. His other achievements include advancing the fields of radio communications and ultrasound technology.
Rutherford became Director of the Cavendish Laboratory at the University of Cambridge in 1919. Under his leadership, the neutron was discovered by James Chadwick in 1932. In the same year, the first controlled experiment to split the nucleus was performed by John Cockcroft and Ernest Walton, working under his direction. In honour of his scientific advancements, Rutherford was recognised as a baron of the United Kingdom. After his death in 1937, he was buried in Westminster Abbey near Charles Darwin and Isaac Newton. The chemical element rutherfordium was named after him in 1997. In 1999, he was named the tenth greatest physicist of all time.

Early life and education

Ernest Rutherford was born on 30 August 1871 in Brightwater, New Zealand, the fourth of twelve children of James Rutherford, an immigrant farmer and mechanic from Perth, Scotland, and Martha Thompson, a schoolteacher from Hornchurch, England. Rutherford's birth certificate was mistakenly written as 'Earnest'. He was known by his family as Ern.
When Rutherford was age 5, he moved to Foxhill, New Zealand, and attended Foxhill School. At 11 in 1883, the Rutherford family moved to Havelock, a town in the Marlborough Sounds. The move was made to be closer to the flax mill Rutherford's father developed. Ernest studied at Havelock School.
In 1887, on his second attempt, he won a scholarship to study at Nelson College. On his first examination attempt, he had the highest mark of anyone from Nelson. When he was awarded the scholarship, he had received 580 out of 600 possible marks. After being awarded the scholarship, Havelock School presented him with a five-volume set of books titled The Peoples of the World. He studied at Nelson College between 1887 and 1889, and was head boy in 1889. He also played in the school's rugby team. He was offered a cadetship in government service, but he declined as he still had 15 months of college remaining.
In 1889, after his second attempt, he won a scholarship to study at Canterbury College, University of New Zealand, between 1890 and 1894. He participated in its debating society and the Science Society. At Canterbury, he was awarded a complex B.A. in Latin, English and Maths in 1892, a M.A. in Mathematics and Physical Science in 1893, and a B.Sc. in Chemistry and Geology in 1894.
Thereafter, Rutherford invented a new form of a radio receiver, and in 1895 he was awarded an 1851 Research Fellowship from the Royal Commission for the Exhibition of 1851, to travel to England for postgraduate study in the Cavendish Laboratory at the University of Cambridge. In 1897, he was awarded a B.A. Research Degree and the Coutts-Trotter Studentship from Trinity College, Cambridge.

Career and research

When Rutherford began his studies at Cambridge, he was among the first 'aliens' allowed to do research at the university, and was additionally honoured to study under J. J. Thomson.
With Thomson's encouragement, Rutherford detected radio waves at, and briefly held the world record for the distance over which electromagnetic waves could be detected, although when he presented his results at the British Association meeting in 1896, he discovered he had been outdone by Guglielmo Marconi, whose radio waves had sent a message across nearly.

Radioactivity

Again under Thomson's leadership, Rutherford worked on the conductive effects of X-rays on gases, which led to the discovery of the electron, the results first presented by Thomson in 1897. Hearing of Henri Becquerel's experience with uranium, Rutherford started to explore its radioactivity, discovering two types that differed from X-rays in their penetrating power. Continuing his research in Canada, in 1899 he coined the terms "alpha ray" and "beta ray" to describe these two distinct types of radiation.
In 1898, Rutherford accepted the Macdonald Chair of Physics at McGill University in Montreal, Canada, on Thomson's recommendation. From 1900 to 1903, he was joined at McGill by the young chemist Frederick Soddy for whom he set the problem of identifying the noble gas emitted by the radioactive element thorium, a substance which was itself radioactive and would coat other substances. Once he had eliminated all the normal chemical reactions, Soddy suggested that it must be one of the inert gases, which they named thoron. This substance was later found to be ²²⁰Rn, an isotope of radon. They also found another substance they called Thorium X, later identified as ²²⁴Rn, and continued to find traces of helium. They also worked with samples of "Uranium X", from William Crookes, and radium, from Marie Curie. Rutherford further investigated thoron in conjunction with R.B. Owens and found that a sample of radioactive material of any size invariably took the same amount of time for half the sample to decay, a phenomenon for which he coined the term "half-life". Rutherford and Soddy published their paper "Law of Radioactive Change" to account for all their experiments. Until then, atoms were assumed to be the indestructible basis of all matter; and although Curie had suggested that radioactivity was an atomic phenomenon, the idea of the atoms of radioactive substances breaking up was a radically new idea. Rutherford and Soddy demonstrated that radioactivity involved the spontaneous disintegration of atoms into other, as yet, unidentified matter.
In 1903, Rutherford considered a type of radiation, discovered by French chemist Paul Villard in 1900, as an emission from radium, and realised that this observation must represent something different from his own alpha and beta rays, due to its very much greater penetrating power. Rutherford therefore gave this third type of radiation the name of gamma ray. All three of Rutherford's terms are in standard use today – other types of radioactive decay have since been discovered, but Rutherford's three types are among the most common. In 1904, Rutherford suggested that radioactivity provides a source of energy sufficient to explain the existence of the Sun for the many millions of years required for the slow biological evolution on Earth proposed by biologists such as Charles Darwin. The physicist Lord Kelvin had argued earlier for a much younger Earth, based on the insufficiency of known energy sources, but Rutherford pointed out, at a lecture attended by Kelvin, that radioactivity could solve this problem. In 1907, he returned to Britain to take the Langworthy Professorship at the Victoria University of Manchester.
In Manchester, Rutherford continued his work with alpha radiation. In conjunction with Hans Geiger, he developed zinc sulfide scintillation screens and ionisation chambers to count alpha particles. By dividing the total charge accumulated on the screen by the number counted, Rutherford determined that the charge on the alpha particle was two. In late 1907, Ernest Rutherford and Thomas Royds allowed alphas to penetrate a very thin window into an evacuated tube. As they sparked the tube into discharge, the spectrum obtained from it changed, as the alphas accumulated in the tube. Eventually, the clear spectrum of helium gas appeared, proving that alphas were at least ionised helium atoms, and probably helium nuclei.
In 1910 Rutherford, with Geiger and mathematician Harry Bateman published
their classic paper describing the first analysis of the distribution in time of radioactive emission, a distribution now called the Poisson distribution.

Model of the atom

Rutherford continued to make ground-breaking discoveries long after receiving the Nobel prize in 1908. Under his direction in 1909, Hans Geiger and Ernest Marsden performed the Geiger–Marsden experiment, which demonstrated the nuclear nature of atoms by measuring the deflection of alpha particles passing through a thin gold foil. Rutherford was inspired to ask Geiger and Marsden in this experiment to look for alpha particles with very high deflection angles, which was not expected according to any theory of matter at that time. Such deflection angles, although rare, were found. Reflecting on these results in one of his last lectures, Rutherford was quoted as saying: "It was quite the most incredible event that has ever happened to me in my life. It was almost as incredible as if you fired a 15-inch shell at a piece of tissue paper and it came back and hit you." It was Rutherford's interpretation of this data that led him to propose the nucleus, a very small, charged region containing much of the atom's mass.
In 1912, Rutherford was joined by Niels Bohr. Bohr adapted Rutherford's nuclear structure to be consistent with Max Planck's quantum hypothesis. The resulting Bohr model was the basis for quantum mechanical atomic physics of Heisenberg which remains valid today.