Ernest Rutherford

A farm boy from Nelson

Ernest Rutherford was born on 30 August 1871 near Nelson, on the South Island of New Zealand, the fourth of twelve children in a flax-milling family. He grew up digging potatoes, mending fences, and reading every book he could get his hands on. Scholarships carried him through Nelson College and then Canterbury College in Christchurch, where he built crude radio detectors in a damp basement and graduated with a double first in mathematics and physical science.

In 1895 a single envelope changed his life. An “1851 Exhibition” scholarship sent him to J. J. Thomson’s Cavendish Laboratory in Cambridge. The story Rutherford liked to tell was that he was digging potatoes when his mother handed him the cable; he flung the spade aside and said, “That’s the last potato I’ll dig.”

Cambridge, then Canada

At the Cavendish he stood out at once: tall, loud, willing to wrestle a brass apparatus into shape at three in the morning. Thomson set him on radio waves, then on the new “Becquerel rays” coming out of uranium. By 1899 Rutherford had sorted those rays into two species, the heavy easily-stopped one he called alpha and the lighter penetrating one beta. The names stuck for a century.

In 1898 he took a chair at McGill University in Montreal. With the chemist Frederick Soddy he showed that radioactive elements actually transmute, one element decaying into another, in defiance of every chemistry textbook of the day. In 1908 the Nobel Committee gave him the prize, not in Physics but in Chemistry, for the work on radioactive substances. Rutherford laughed about it for the rest of his life. He liked to say he had observed many transformations in his career, but the fastest was his own from physicist to chemist on the night of the announcement.

Ernest Rutherford, 1st Baron Rutherford of Nelson (30 August 1871 – 19 October 1937), 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."

Manchester and a piece of tissue paper

In 1907 Rutherford crossed back to England to take the chair at Manchester. He inherited a thriving radioactivity group and quickly made it the loudest, most productive laboratory in Europe. Two of the people he set to work were Hans Geiger and an undergraduate named Ernest Marsden.

The project Rutherford gave them in 1909 sounded routine. Fire alpha particles from a radium source at a sheet of gold foil only a few hundred atoms thick. Count the deflections. Thomson’s “plum pudding” atom had no concentration of charge anywhere, so everyone expected the alphas to sail through with only the mildest of nudges.

Geiger and Marsden saw something strange. Most alphas did go straight through. But a tiny fraction, roughly one in eight thousand, bounced nearly straight back. Rutherford described it later in the most quoted sentence of experimental physics:

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.

He stewed on the numbers for eighteen months. In May 1911, in a paper in Philosophical Magazine, he proposed the nuclear atom: a tiny, dense, positively charged core containing nearly all the mass, with the electrons occupying the cavernous volume around it. The atom was mostly empty space. The pudding was gone.

Bohr arrives

In March 1912 a young Dane with a half-finished thesis appeared at Manchester. Niels Bohr had been miserable at Cambridge under Thomson; Rutherford greeted him like a long-lost nephew, listened to his objections, and put him on the staff for the spring. Rutherford was loud, expansive, profane, openly proud of his colonial bluntness. Bohr was quiet and slow-spoken, qualifying every clause until a sentence had three careful subordinates. They argued and argued, and out of those arguments came the 1913 trilogy in which Bohr quantised the orbits of the Rutherford atom and explained the spectrum of hydrogen.

Rutherford never quite believed the postulates. He once asked Bohr, straight-faced, how an electron knew which orbit it was going to jump to before it jumped. But he backed the younger man without reservation, and the partnership became the template for what a great physics group could look like.

Splitting the atom

In 1917, while serving on anti-submarine committees during the First World War, Rutherford fired alpha particles into nitrogen gas and detected the unmistakable signature of hydrogen nuclei coming out. The alpha had knocked a proton free; the nitrogen had been transmuted into oxygen. The phrase “splitting the atom” entered popular use. He published in 1919, the same year he moved south to take Thomson’s old chair at the Cavendish in Cambridge.

For the next eighteen years he ran the Cavendish like a benevolent naval captain. The students he trained in that period read like a roll call of the next quarter-century of physics: James Chadwick, who discovered the neutron in 1932; John Cockcroft and Ernest Walton, who built the first accelerator and artificially split lithium the same year; Mark Oliphant, who later co-discovered tritium; Pyotr Kapitza, who built up low-temperature physics until Stalin recalled him in 1934.

The death of a heavyweight

Rutherford died on 19 October 1937, aged sixty-six, after a botched operation on a strangulated hernia. He had been raised to the peerage in 1931 as Baron Rutherford of Nelson, and the story around the Cavendish was that he had insisted on waiting for a surgeon of equal rank. By the time the right man arrived it was too late. His ashes were buried in Westminster Abbey near Isaac Newton and Lord Kelvin. Element 104 was officially named rutherfordium in 1997.

The book character is worth holding in your head. Rutherford was the opposite of every cliché about quiet European theorists: a tall, loud colonial who paced his lab roaring at apparatus, sang “Onward, Christian Soldiers” off-key whenever an experiment came right, and intimidated younger physicists by sheer volume. Yet the mentor who took the slowest-spoken Dane in Europe and gave him the freedom to invent the quantum atom was the same man. The pairing of Rutherford and Bohr in 1912 and 1913 is one of the most consequential mentor-student relationships in twentieth-century science, and it worked precisely because they did not resemble each other in the slightest.

At the opening session of the 1938 Indian Science Congress, which Rutherford had been expected to preside over before his death, astrophysicist James Jeans spoke in his place and deemed him "one of the greatest scientists of all time", saying: