Lord of the atoms

by Rebecca Priestley / 15 November, 2008
Rebecca Priestley celebrates the Nobel Prize awarded to one of the greatest ever scientists - and a humanitarian hero.
Ernest Rutherford
Ernest Rutherford. Photo/Tourist and Publicity. Ref: 1/2-035078-F. Alexander Turnbull Library, Wellington, New Zealand. http://natlib.govt.nz/records/23218542


On December 10, 1908, Ernest Rutherford, a 37-year-old physicist with a handsome black moustache and a smart tailcoat suit, was presented with the Nobel Prize in Chemistry by the King of Sweden.

In his presentation speech, the president of the Royal Academy of Sciences noted that Rutherford's discoveries "led to the highly surprising conclusion that a chemical element, in conflict with every theory hitherto advanced, is capable of being transformed into other elements". At the formal banquet following the prize-giving, Rutherford joked that the fastest transformation he had ever encountered was his own instant one from physicist to chemist.

Rutherford, then professor of physics at Manchester University, was awarded the chemistry prize for work that included the discovery that elements can be transformed, through radioactivity, into different elements. Rutherford worked at the boundary of physics and chemistry, so after deciding the physics prize should go to Gabriel Lippmann for his method of colour photography, the Nobel Prize judges deemed Rutherford worthy of the chemistry prize and his transformation from physicist to chemist was effected.

A century on, and Rutherford remains New Zealand's most famous scientist, the subject of more than 40 memoirs or biographies, and the first of three New Zealand-born Nobel laureates. We recognise his face - it features on our $100 note and various postage stamps - and he has even had a chemical element named after him, but how much do we really know about Ernest Rutherford and his achievements?

New Zealand's most remarkable scientist was born in Brightwater, near Nelson, in 1871 to James Rutherford, who worked at various times as a flax-miller, mechanic and wheelwright, and Martha, a former teacher. Education was important to the Rutherfords, and Martha taught all the Rutherford children reading, writing and arithmetic before they started school. A series of scholarships took Rutherford to Nelson College, then to the University of New Zealand's Canterbury College in Christchurch where he used a small room beneath a staircase - now immortalised as "Rutherford's Den" - for research.

Rutherford's next scholarship was the most important. The Exhibition of 1851 Scholarship gave the young New Zealander £150 a year for two years, enabling him to study at Cambridge University's Cavendish Laboratory under Professor JJ Thomson.

By the end of the 19th century, gentlemen scientists who focused on natural history, chemistry and geology dominated New Zealand science. The country was at the end of a 10-year depression, and the Government saw science, and the few professional scientists, mainly as a means of boosting economic development. In 1895, however, when Rutherford arrived at Cambridge, Europe was poised for a revolution in physics.

He initially worked on electromagnetism and wireless signalling, but following Wilhelm Röntgen's sensational discovery of X-rays - a mysterious form of energy that could penetrate wood and paper but not bones or metals - Rutherford, too, began working with this form of electromagnetic radiation. Röntgen's discovery was soon followed by Henri Becquerel's observation that uranium compounds spontaneously emitted similar rays, and Marie and Pierre Curie's isolation of the radioactive elements polonium and radium.

By 1897, Thomson, Rutherford's professor, had concluded that an electric current was a fast-moving stream of minuscule particles, later called electrons, which he determined had a mass 2000 times smaller than the smallest known particle, the hydrogen atom. Thomson then developed a radical new "plum pudding" model of the atom - previously believed to be nature's smallest particle - with negatively charged electrons dispersed like raisins in a solid, spherical positively charged atom.

The work of scientists like Röntgen, Becquerel, the Curies and Thomson was part of a scientific revolution that blew apart classical physics by revealing there was a world inside the atom. The challenge for physical scientists like Rutherford was to determine the nature of the "X-rays" and "Becquerel rays" - what the Curies had called "radioactivity".

Rutherford began his own investigation of the subatomic world by studying the radiations emitted by the elements uranium and thorium, and concluded there were two distinct forms of radiation - alpha radiation, which he determined was a stream of positively charged helium atoms, or alpha particles; and the more penetrating beta radiation, a stream of negatively charged electrons.

On completing his PhD, Rutherford took a position in Canada, as professor of physics at McGill University in Montreal. Here, he identified the emanation from thorium as a new gaseous element, radon. Working with chemist Frederick Soddy, he determined that in the pro-cess of emitting radiation, an element is spontaneously transformed, either into an isotope (a physically different form of the element) or into another element.

This remarkable discovery, which Rutherford and Soddy described as "modern alchemy", helped explain the seemingly inexhaustible supply of energy from radio-active elements like radium. They also discovered that all the radio-active elements have a distinct "half-life" - the time it takes for half of the atoms of the original sample to decay into an isotope or new element. The half-lives of the elements they tested varied wildly: uranium's half-life was calculated at 4.5 billion years, radium's at 1620 years, and a decay product of thorium at just 22 minutes.

The Nobel Prize in Chemistry that Rutherford won, awarded once he was physics professor at Manchester University, was "for his investigations into the disintegration of the elements and the chemistry of radioactive substances" - but some of his best work was yet to come.

"He had an uncanny ability to get inside the sub-atomic world in his mind," says Paul Callaghan, professor of physical sciences at Victoria University. "He consequently designed experiments which were right on target. To Rutherford, atoms and nuclei were real palpable things."

One of science's most famous experiments was designed and supervised by Rutherford in his university laboratory in Manchester. Working with his student Ernest Marsden (who later became head of New Zealand's Department of Scientific and Industrial Research) and assistant Hans Geiger, Rutherford designed an experiment to look for evidence of alpha particles directly reflected from a metal surface.

Marsden observed that a tiny fraction of alpha particles fired at a thin gold foil was deflected straight back, instead of all of them passing straight through, as would have been expected. Although Callaghan mischievously points out that to design the ex-periment you must have first expected the result, Rutherford later described this result as being "almost as incredible as if you had fired a 15-inch shell at a piece of tissue paper and it came back and hit you".

Rutherford subsequently came up with a new theory for the structure of the atom, proposing an atom with a centralised concentration of mass and a positive charge - which he called the nucleus - surrounded by empty space and a sea of orbiting negatively charged electrons. In 1913, Danish physicist Niels Bohr extended Rutherford's model of the atom by fixing the energy levels at which electrons could orbit the nucleus; just a few years after the atom was widely believed to be indivisible, the "Rutherford-Bohr" model, with its small central nucleus and orbiting electrons, became the new accepted model of the atom.

This new model of the atom was so remarkable, it later inspired English physicist Sir Arthur Eddington to remark: "Lord Rutherford is usually credited with having discovered the nucleus in the atom. I think he put it there."

After working on the British sonar project during World War I, Rutherford returned to atomic science and conducted another of his genius experiments. While bombarding nitrogen atoms with alpha particles, he realised the nitrogen atoms were absorbing the alpha particles, emitting a hydrogen nucleus and being converted from nitrogen atoms into oxygen atoms. As Rutherford's biographer, physicist John Campbell, says, he "became the world's first successful alchemist and the first person to split the atom".

In 1919, Rutherford returned to the Cavendish Laboratory at Cambridge University - this time as director - where he remained for the rest of his career.

Rutherford was feted in 2008 as part of the 100th anniversary of his being awarded the Nobel Prize in Chemistry. November 10 marks the centenary of the Royal Swedish Academy's decision to award Rutherford, and December 10 the presentation of the prize in Stockholm.

The centenary was celebrated in London with a public lecture and an exhibition at the Royal Society of London (of which Rutherford is a past president) and with a cocktail party at New Zealand House, which featured a display put together by Rutherford's Den staff.

At Otago University, some of New Zealand's top scientists - including 13 past winners of New Zealand's top science prize, the Rutherford Medal for Science and Technology - gathered for the Rutherford Symposium. The University of Canterbury, Rutherford's alma mater, hosted the inaugural Rutherford Lecture, the first of what became an annual event.

In Nelson, Campbell, also Rutherford Birthplace Project convenor, previewed a documentary about the scientist, based on Campbell's 1999 biography and directed by Gillian Ashurst. The Royal Society of New Zealand marked the centenary with a Rutherford-themed annual science honours dinner, at which the 2008 Rutherford Medal was awarded, along with the year's other top science medals and prizes. Guest of honour at the dinner were Rutherford's great-granddaughter Professor Mary Rutherford Fowler, who marked the November 10 centenary in Christchurch by launching her lecture tour as the Royal Society of New Zealand's 2008 Distinguished Speaker, where she spoke on the subject of "Rutherford in the 21st century".

Fowler, a geophysics professor from the University of London, comes from a long line of distinguished physicists. Both her parents were physicists - "we talked about science at home, especially physics ... [it] was just superb fun," she says. Her mother stopped work to raise a family, but her father, Peter Fowler, was a physics professor at the University of Bristol. His father, Ralph Fowler, was a physics professor at Cambridge University, who was married to Rutherford's daughter, Eileen.

It's a tall order for the work of a scientist who died in 1937 to have such relevance in 2008, but Fowler points out that "Rutherford's work is behind so much of the way we look at the planet today". One of the issues Fowler will address in her lectures around New Zealand is climate change.

"Much of our worry about climate change comes from the discovery that the Earth's climate can shift very quickly. This knowledge comes from the isotopic record as recorded in ice cores and deep-sea sediment cores."

It was Rutherford, along with his McGill University colleague Frederick Soddy, who discovered radioactive isotopes. Rutherford's ideas also lay behind the discovery of deuterium, or heavy hydrogen, whose ratio to regular hydrogen is now analysed in ice and sediment cores to determine past temperatures. Greenhouse gas issues inevitably lead to issues of energy. "Like it or not, one of the routes out of the greenhouse problem is nuclear power, especially for nations like China which have few other options except coal," says Fowler.

Rutherford is often called the father of nuclear physics but he didn't live to see nuclear energy or nuclear weapons. Nor did he anticipate them. Despite his earlier joke that "some fool in a laboratory might blow up the universe unawares", by 1933, when the possibility of energy from the atom was being considered, he dismissed such talk, saying, "Anyone who expects a source of power from the transformation of these atoms is talking moonshine."

As well as being a great scientist, Rutherford, despite his imposing figure and booming voice, was an exceptionally collegial fellow. "He pioneered the modern way of doing science, with an inspiring mentor working in collaboration with younger students and researchers", says Paul Callaghan. "He mentored a generation of brilliant scientists - nine of his PhD students won Nobel Prizes."

His collegiality extended beyond his own laboratory. "Rutherford helped make science an international community," Fowler says of her great-grandfather. "One of his last and greatest actions was to lead the effort to bring scientists out of Nazi Germany. He and his friend Albert Einstein, along with many leading British scientists, saved about a thousand people who, by virtue of religion, political opinion or race, became unable to work. He'd write to small universities in obscure places saying, more or less, 'I hear you need someone. He's on the boat.' Faced with a command from Rutherford, who could say no?" At least one of the scientists Rutherford helped, physicist Max Born, subsequently won his own Nobel Prize.

Rutherford continued to be recognised throughout his career, winning many medals and awards. He was elected a Fellow of the Royal Society of London in 1903 and served as president from 1926 to 1931. He was knighted in 1914 and in 1931 was elevated to the peerage, choosing the title Lord Rutherford of Nelson in recognition of his birthplace.

He died in 1937, aged 66, still working as director of the Cavendish Laboratory at Cambridge University where he started his international career. As John Campbell describes it, Rutherford "died of fame". Suffering from a strangulated hernia, he was admitted to hospital but was left to wait eight hours for a titled Harley St surgeon to arrive. Sir Thomas Dunhill came in by train and operated but a few days later Rutherford died. Had the local Cambridge surgeons been allowed to operate he may have recovered.

 

"His work laid the foundation of modern understandings of chemistry and physics," says Paul Callaghan. "He is our greatest scientist, and one of the greatest scientists who ever lived."

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