Ernest Rutherford (30 Aug 1871–19 Oct 1937) was a New Zealand born British physicist who is considered to be the father of nuclear physics. Through numerous experiments, Rutherford changed our understanding of the atom. Rutherford discovered the atom was mostly space with a nucleus and electrons. Rutherford discovered properties of radiation, half-life and performed the first artificially induced nuclear reaction when he transformed nitrogen atoms into oxygen atoms. His work was a pivotal moment in the development of nuclear energy, radiation and the sub-atomic level of physics. His work was also instrumental in later quantum physics.
Rutherford was born in Brightwater, near Nelson in New Zeland to an English mother and Scottish father. He studied at Canterbury College, the University of New Zealand where he gained a BA, MA and BSc. After Canterbury, he gained a scholarship to study at the University of Cambridge, where he worked and studied at the Cavendish Laboratory under renowned physicist J.J. Thomson. During his time in Cambridge, Rutherford was at the cutting edge of detecting radio waves over distance.
In 1898, Rutherford took a position at McGill University in Montreal, Canada before returning to the University of New Zealand. At the outbreak of the First World War, he was chair of physics at the Victoria University of Manchester. During the war, he worked on a top-secret project to detect submarines underwater. Rutherford developed techniques in secret labs in Manchester which could detect sound waves in water and enable ships to detect the presence of submarines in water. The sonar detection was critical in both World World Wars due to the submarine threat posed by the Germans. His work was covered by the Official Secrets Act, and it wasn’t known until after his death. Even during the First World War, he continued his own research into the nature of the atom. On one occasion, he arrived late for a meeting with military officials, with customary relish he dismissed his lateness by saying his experiments (on slitting the nucleus of the atom) were “far greater than that of the war!”
Splitting the atom
“I have broken the machine and touched the ghost of matter.”
Ernest Rutherford, quoted in A Force of Nature: The Frontier Genius of Ernest Rutherford by Richard Reeves
In 1918, while working in Manchester, Ernest Rutherford was the first person to knowingly split the nucleus of an atom. He bombarded nitrogen with naturally occurring alpha particles from radioactive material. The nitrogen was converted to oxygen.
In 1932, two of his students John Cockroft and Ernest Walton, working under Rutherford’s direction, were the first to split the nucleus by artificial means. They used a particle accelerator to bombard lithium with protons -producing two alpha particles.
After the First World War, he returned to the Cavendish laboratory in Cambridge.
Radioactivity was first discovered in 1896 by the French scientist Antoine Henri Becquerel. However, Becquerel never developed this – beyond the knowledge of uranium compounds breaking down. Rutherford was intrigued at the possibilities and took up the subject. He discovered that the radioactive emissions comprised of two fast-moving particles which he termed alpha and beta rays.
“Radioactivity is shown to be accompanied by chemical changes in which new types of matter are being continually produced. … The conclusion is drawn that these chemical changes must be sub-atomic in character.”
– Rutherford, Philosophical Magazine (September 1902)
Another very important discovery for science was the awareness that there was a very powerful energy released from the atomic behaviour. Previously scientist assumed energy had an external source and came from chemical reactions. But, Rutherford showed that behaviour in the atom itself could unleash a great wave of ‘atomic’ energy. This knowledge was critical in the development of atomic energy and atomic bombs.
Rutherford’s experiments also showed that individual atoms could change their atomic structure. This changed the perception that atoms were indestructible. Rutherford created experiments which showed Uranium atoms transforming into lead through radioactive decay. Through measuring rates of decay, he was able to formulate a concept known as ‘half-life period’ – which showed how long it took for 50% of atoms to decay. This became useful for radioactive dating, e.g. carbon dating.
In 1903, he published “Law of Radioactive Change,” which along with Frederick Soddy, demonstrated how radioactivity meant atoms spontaneously changed into another unknown matter. He was awarded the Nobel Prize in Chemistry in 1908 for this work of radioactivity and disintegration.
The atom had long been considered the smallest unit of matter in the universe, but Rutherford showed that an atom was actually comprised of mostly space with nuclei and alpha particles orbiting around. (Niels Bohr later described the atom to be like a mini-universe, Bohr made use of Rutherford’s research).
“The first point that arises is the atom. I was brought up to look at the atom as a nice hard fellow, red or grey in colour, according to taste. In order to explain the facts, however, the atom cannot be regarded as a sphere of material, but rather as a sort of wave motion of a peculiar kind.”
Gold Foil experiment
In 1909, Rutherford, along with Hans Geiger and Ernest Marsden, experimented with alpha particles being directed at a sheet of gold. They found that the harder alpha particles could go straight through the gold sheet, but some (about 1 out of 8,000) alpha particles were reflected back. Rutherford repeated this experiment numerous times, and with mathematical proof was able to show that the alpha particles which went straight through were going through the empty space of the atom. The particles which were reflected were hitting the dense nucleus of the atom. It was a revolutionary moment in science to realise most matter is empty space! Even gold – one of the hardest and most solid objects in the world was comprised of gold atoms which were mostly space.
Even Rutherford was surprised at his findings writing:
“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.”
as quoted in Rutherford and the Nature of the Atom (1964)
Rutherford was a charismatic figure who had great faith in his own abilities. He never suffered from false modesty but was acutely aware of his groundbreaking research and development of physics. When a colleague commented on Rutherford’s ability to always be on the ‘crest of a wave’ of scientific research. Rutherford replied. “Well, why not? After all, I made the wave, didn’t I.’ By his fellow scientists, he was nicknamed ‘The Crocodile’ for always looking ahead.
Rutherford married Mary Georgina in 1900. They had one daughter Eileen Mary (1901–1930). He was president of the Royal Society from 1925-1930.
He died in 1937 from an infected hernia. He passed away one year before the fission of uranium nucleus in Berlin in 1938, which turned nuclear physics into a weapon of war. Ironically, during the First World War, he had stated about the potential of atomic energy that he hoped man would not discover how to unless the power of atomic energy until “man was living at peace with his neighbours.”
A Force of Nature: The Frontier Genius of Ernest Rutherford
A Force of Nature: The Frontier Genius of Ernest Rutherford
by Richard Reeves at Amazon
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