Ernest Rutherford

• 1. Introduction

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  Ernest Rutherford was born on the 30th of August 1871 in Brightwater, New Zealand, the fourth of twelve children, and he died with a burial spot beside Isaac Newton and Charles Darwin in Westminster Abbey. That journey from a farm in rural New Zealand to the inner sanctum of British science is the arc of one of the most consequential experimental lives in history. His birth certificate misspelled his first name as "Earnest". His family called him Ern. The irony is that few scientists have ever taken the structure of matter more seriously.

  What did Rutherford actually discover? How did a man trained in Latin and rugby become the person who proved atoms have a nucleus, named the proton, predicted the neutron, and split the atom - all in a single career spanning four decades? And what does it mean that a 1933 speech he gave about how useless atomic energy was inspired the very scientist who would later conceive the nuclear chain reaction?

  Those are the questions worth sitting with.

• 2. A Farm Boy's Education

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  At age 11, in 1883, Rutherford's family moved to Havelock in the Marlborough Sounds so his father could be nearer to the flax mill he operated. The family had already moved once before, when Ernest was five, from Brightwater to Foxhill. These were the early years of a boy who would spend his entire scientific career uprooting received ideas about matter itself.

  Scholarships were the pathway. On his first attempt at a scholarship to Nelson College, Rutherford scored the highest mark of anyone from Nelson. He still did not win it that year. On his second attempt in 1887 he did win, and when the award was announced he had received 580 out of a possible 600 marks. Havelock School celebrated by presenting him with a five-volume set titled The Peoples of the World.

  At Nelson College, Rutherford was head boy in 1889 and played rugby. He was offered a cadetship in government service but turned it down because he still had 15 months left of college. That refusal - choosing education over early employment - set the entire trajectory. After a second attempt, he won a scholarship to Canterbury College, University of New Zealand, where he studied from 1890 to 1894 and emerged with three degrees: a Bachelor of Arts in Latin, English and Mathematics in 1892; a Master of Arts in Mathematics and Physical Science in 1893; and a Bachelor of Science in Chemistry and Geology in 1894.

  From Canterbury, Rutherford invented a new form of radio receiver and used that work as the basis for winning an 1851 Research Fellowship in 1895, which sent him to the Cavendish Laboratory at Cambridge.

• 3. Radioactivity Named and Measured

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  At Cambridge, Rutherford was among the first researchers admitted without a Cambridge degree - one of the first so-called "aliens" allowed to do research there. He studied under J. J. Thomson, and when Thomson presented the discovery of the electron in 1897, Rutherford's work on how X-rays affect gases had contributed to that finding.

  Hearing of Henri Becquerel's experiments with uranium, Rutherford began probing its radioactivity and found two distinct types of radiation that differed from X-rays in their penetrating power. In 1898 he accepted the Macdonald Chair of Physics at McGill University in Montreal, and in 1899 he named these two types: alpha rays and beta rays. Those names remain in use today.

  At McGill, from 1900 to 1903, Rutherford worked alongside the chemist Frederick Soddy. Soddy was tasked with identifying the noble gas emitted by radioactive thorium. After eliminating all ordinary chemical reactions, Soddy concluded it had to be one of the inert gases; they named it thoron, later identified as an isotope of radon. Working further with the physicist R. B. Owens, Rutherford observed something startling: a radioactive sample of any size always took the same amount of time for exactly half of it to decay. In thoron's case that was 11 minutes. He coined the term "half-life" to describe this constant. Rutherford and Soddy published this as the "Law of Radioactive Change", and in doing so overturned a centuries-old assumption - that atoms were indestructible. They showed that radioactivity was the spontaneous disintegration of one type of atom into another.

  In 1903, Rutherford classified a third type of radiation - originally noticed but unnamed by French chemist Paul Villard in 1900 - as something distinct from alpha and beta rays because of its vastly greater penetrating power. Rutherford named it the gamma ray. All three names are standard today. The following year, in 1904, he proposed that radioactivity could supply the energy needed to sustain the Sun for the millions of years that biological evolution required - directly addressing the physicist Lord Kelvin's argument that the Earth was too young for Darwin's theory to hold. Rutherford made this point at a lecture that Kelvin himself attended.

• 4. The Gold Foil and the Nucleus

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  Under Rutherford's direction in 1909, Hans Geiger and Ernest Marsden fired alpha particles at a sheet of thin gold foil. No theory of matter at the time predicted anything other than minor deflections. Some alpha particles came back almost the way they had come. Rutherford later described his reaction: "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."

  Rutherford's interpretation of those high-deflection angles led to his 1911 proposal that the atom has a very small, heavily charged nucleus at its center containing most of the atom's mass. The rest of the atom is largely empty space. In developing the tools for this work, Rutherford and Geiger had also built zinc sulfide scintillation screens and ionization chambers to count individual alpha particles. By dividing the total accumulated charge by the number of particles counted, Rutherford established that the charge on the alpha particle was two. In late 1907, he and Thomas Royds had already shown that alpha particles were ionized helium atoms and probably helium nuclei, by allowing them to accumulate in an evacuated tube until the spectrum of helium gas appeared clearly.

  In 1912, Rutherford invited Niels Bohr to join his laboratory. Bohr took Rutherford's nuclear structure and reconciled it with Max Planck's quantum hypothesis, proposing that electrons move in specific orbits around the nucleus. The Bohr model that resulted became the foundation for Heisenberg's quantum mechanical atomic physics.

• 5. The Proton and the Neutron

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  In 1913, Rutherford and H. G. Moseley developed the atomic numbering system together, using cathode rays to bombard various elements with electrons and observing that each element responded in a distinct, consistent way. Their conclusion - that each element is defined by the properties of its inner structure - was the first assertion of what would later be understood as the atomic nucleus.

  In 1917, working at Manchester shortly before moving to Cambridge, Rutherford began the experiments that would lead to the discovery of the proton. He found that when alpha particles struck nitrogen nuclei, particles were ejected that had unit charge and one-quarter the momentum of the alpha particles. He initially called this ejected particle the "hydrogen atom", since hydrogen nuclei were the lightest known positive charge carriers. In 1920 he formally postulated it as a new fundamental particle and named it the proton, confirming and extending the 1898 work of Wilhelm Wien.

  Also in 1920, working with Niels Bohr, Rutherford theorized that a neutral particle must exist inside the nucleus - something to counteract the repulsion between positively charged protons and hold nuclei together. He named this hypothetical particle the neutron in his 1920 Bakerian Lecture. The known mass of nuclei was roughly twice what protons alone could account for, and "nuclear electrons" seemed unable to explain how they could be trapped inside the nucleus. It was not until 1932 that James Chadwick, Rutherford's associate at the Cavendish Laboratory, proved the neutron's existence by bombarding beryllium with alpha particles. Chadwick received the Nobel Prize in Physics for this discovery in 1935.

• 6. Cavendish and the Atom Split

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  Rutherford returned to Cambridge in 1919 as Cavendish Professor of Physics, succeeding J. J. Thomson in the role. He held that position until his death in 1937. The Cavendish Laboratory under Rutherford became a kind of factory for foundational physics. Beyond Chadwick's neutron, the laboratory also produced the first controlled splitting of the atomic nucleus, carried out in 1932 by John Cockcroft and Ernest Walton using a particle accelerator they built themselves. Nobel prizes followed for all three of those achievements.

  Patrick Blackett, a research fellow under Rutherford, used natural alpha particles to demonstrate induced nuclear transmutation. Later Rutherford's team used protons from an accelerator to demonstrate artificially induced nuclear reactions. In a 1933 speech - printed in The Times on the 12th of September 1933 - Rutherford described the energy released when lithium was split by protons as enormous, but dismissed the whole enterprise as a "very poor and inefficient way of producing energy." He said that anyone who looked for a practical power source in atomic transformation was "talking moonshine."

  Leó Szilárd later reported that reading this speech was what prompted him to imagine a controlled energy-producing nuclear chain reaction. Rutherford's dismissal, in other words, may have been the provocation that launched nuclear energy as a concept. Rutherford died too early to witness what followed from it.

• 7. Personal Life and Death

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  Rutherford married Mary Georgina Newton on the 1st of January 1900 at St Paul's Anglican Church in Papanui, Christchurch. He had been engaged to her before leaving New Zealand for Cambridge. They had one daughter, Eileen Mary, born in 1901. Eileen married the physicist Ralph Fowler and died in 1930 during the birth of her fourth child. Rutherford's hobbies were golf and motoring.

  During his Manchester years he lived in the suburb of Withington on Wilmslow Road. The house received a blue plaque in 2012 and is now called Rutherford Lodge.

  For some period before his death, Rutherford had a small hernia that he declined to have treated. It eventually strangulated, causing acute illness. He underwent emergency surgery in London but died in Cambridge four days later, on the 19th of October 1937, at the age of 66. Physicians recorded the cause as intestinal paralysis. After cremation at Golders Green Crematorium, he was buried in Westminster Abbey near Newton, Darwin, and other British scientists. The chemical element rutherfordium, atomic number 104, was named in his honor in 1997. Since 1999, his portrait has appeared on the New Zealand one hundred-dollar note.

• 8. The Measure of a Legacy

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  At the 1938 Indian Science Congress - the session Rutherford had been expected to chair before his death - the astrophysicist James Jeans stepped in and offered an assessment: "to match Rutherford's work in quantity as well as in quality, we must go back to Newton." Jeans praised what he called Rutherford's "flair for the right line of approach to a problem" and described him as "ever the happy warrior."

  Rutherford won the Nobel Prize in Chemistry in 1908 for his investigations into the disintegration of elements and the chemistry of radioactive substances. In the decades before and after that prize, he collected the Rumford Medal, the Elliott Cresson Medal, the Matteucci Medal, the Copley Medal, the Franklin Medal, the Faraday Medal, and the Wilhelm Exner Medal. King George V made him a Knight Bachelor in 1914, awarded him the Order of Merit in 1925, and elevated him to Baron Rutherford of Nelson in 1931. In 1999, he was ranked the tenth greatest physicist of all time.

  His six books spanned from Radio-activity in 1904 to The Newer Alchemy, published the year he died. The concept of the nuclear structure of the atom, the half-life, the naming of alpha, beta, and gamma radiation, the proton, and the theoretical prediction of the neutron are all traceable back to Rutherford - many of them discovered while his Nobel-winning peers were still working out the implications of his previous discovery. His final book appeared in 1937; James Chadwick's neutron, proven with beryllium and alpha particles three years after Rutherford predicted it, remains the particle that makes nuclear reactors possible.