Ernest Rutherford, Lord
Rutherford of Nelson
(born: August 30, 1871 / died: October 19, 1937)
|Ernest Rutherford was born in Brightwater, near Nelson, New Zealand
The creator of modern atomic physics and forerunner of the nuclear age, one of the greatest scientists of the twentieth century.Awarded the Nobel Prize in Chemistry in 1908 and a baronetcy, choosing the title Baron Rutherford of Nelson, in 1931.
In the words of Einstein, "a second Newton". The man who "tunneled into the very material of God": inventor, experimenter and Nelson farm boy.
Rutherford’s strengths as a scientist are legion. A prolific, practical inventor and scientific theorist whose ideas were based on rigorous experimentation; one of the original "demo or die" scientists; turning conjecture into fact. He attributed his willingness to experiment and find unorthodox solutions to his hardscrabble background in rural New Zealand: "We don’t have the money, so we have to think".
Ernest Rutherford’s three major discoveries shaped modern science, created nuclear physics and changed the way that we envisage the structure of the atom today.
Rutherford’s first discovery was that elements are not immutable, but can change their structure naturally, changing from heavy elements to slightly lighter elements. This led to him being awarded the Nobel Prize for Chemistry in 1908, at the age of 37, for his work on the transmutation of elements and the chemistry of radioactive material.
His second discovery, the nuclear model of the atom, became the basis for how we see the atom today: a tiny nucleus surrounded by orbiting electrons.
He built on this discovery for his third great achievement, the splitting of the atom, making him, as John Campbell says in his biography of Rutherford in The Dictionary of New Zealand Biography, "the world’s first successful alchemist".
|Rutherford’s advances in the study of radioactive
atoms (most notably discovering that two different emissions, named alpha
and beta rays, emanate from radioactive atoms) and his genius for experimentation
secured his reputation, even compared to his brilliant mentor Thomson. In
1898, at the age of 27, Rutherford moved to McGill University in Montreal,
where he was offered the position of Professor of Physics.
The McGill years, from 1898 to 1907, were significant for it was at McGill that he made the first of his three major discoveries. Assisted by chemist Frederick Soddy, he unravelled the mysteries of radioactive atoms. Going against a popularly accepted belief that elements were immutable (as the derivation of the word atom implies: from the Greek tomos, to cut, and a meaning not; therefore something unsplittable - a conceptual billiard ball), Rutherford showed that some heavy atoms spontaneously decay into slightly lighter, and chemically different, atoms. His book on this subject, Radioactivity, was published in 1904, followed by others in 1906 and 1930. It was this discovery and his work on the chemistry of radioactive materials, that led to him being awarded the Nobel Prize in Chemistry in 1908 for his "investigations into the disintegration of the elements, and the chemistry of radioactive substances."
In 1907, Rutherford was lured back to England, at the age of 36, to become Professor of Physics at Manchester University.
In 1907 Rutherford began a debate with physicist Antoine Becquerel on how alpha particles, reacted when they were ejected from radioactive material. Discovering that alpha particles tended to bounce off air molecules, he surmised that there had to be something at the centre of atoms to deflect them. He tested his assumptions by bouncing alpha particles off a sheet of gold leaf and determined that the most powerful part of an atom was a very small, heavy, core at its centre, a central electric charge concentrated at a point - the nucleus. This was surrounded by a cloud of electrons made up of an opposing electrical charge.
This concept of opposite charges which, as David Eliot Brody and Arnold R Brody noted, "marks the beginning of the modern understanding of the structure of the atom", was Rutherford’s second great discovery. As Campbell says, "the nuclear model of the atom had been born".
This orbiting model was the most revolutionary idea of Rutherford’s career, as Nigel Costley, writing in the Sunday Star Times, relates:
"Prior to Rutherford the best model of the atom was JJ Thomson's plum pudding which pictured it in a thin cloud of positive charges, with electrons dotted amongst it, like so many raisins in a plum pudding.
"Rutherford’s experiments showed the pudding idea was wrong, replacing it with a solar system model. An incredibly dense positively charged nucleus lay at the centre which was tiny compared to the whole atom; like a postage stamp in a football field.
"Through his studies of radioactivity in the 1890s he discovered alpha particles which became, in his skilled and determined hands, the chief weapon in prising out the secrets of the sub-atomic world. These particles were known to be 7400 [closer to 7273] times heavier than electrons and when he fired them in huge numbers at a strip of very thin gold foil, it was expected they would effortlessly pass straight through.
"However a surprisingly high number were deflected [...]. Rutherford was astonished: "It was as if you fired a 15-inch shell at a sheet of tissue paper and it came back to hit you." From these deflections he was able to calculate the size of the nucleus."
During World War I Rutherford worked on acoustic methods of detecting submarines and developed several new technologies. He then drew on a lifetime’s strengths in practical experimentation for the third great breakthrough of his career.
Radioactivity had shown that some atoms spontaneously split, but in 1917 (reported 1919) the committed alchemist Rutherford, as McLauchlan writes, "detected the transmutation of one elementary material, nitrogen, into another, oxygen, which was induced artificially when the nitrogen atom was bombarded by the natural alpha articles of radium." Rutherford was, as he describes the process himself with typical understatement, "playing with marbles." He was using alpha particles to eject protons from materials containing hydrogen when he found the same thing happened in nitrogen (which doesn't contain hydrogen). But more importantly the proton came out at higher energy than it could have received by collision.
In that year Rutherford had written to Niels Bohr that, "... I am also trying to break up the atom by this method ... Regard this as private."
Effectively Rutherford had "broken up" or split the atom. With
this experiment, he was the first human to create a "nuclear reaction", though
a weak one. From Rutherford's first discovery onwards he had swept away
accepted models of the stable atom, altered the course of modern science
and made possible the development of nuclear physics. Once more Rutherford's
demonstrations had changed the way we viewed and conceived of the world,
breaking through the gross world of matter into the subtle world of atoms.