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Ernest Rutherford
"The Newtan of Atomic Physics"
 
 
 
Dr Subodh Mahanti

 

“It is given to but few men to achieve immortality, still less to achieve Olympian rank, during their own lifetime. Lord Rutherford achieved both. In a generation that witnessed one of the greatest revolutions in the entire history of science he was universally acknowledged as the leading explorer of the vast infinitely complex universe within the atom, a universe that he was first to penetrate.”

The New York Times


“Ernest Rutherford is one of the most illustrious scientists of all time. He is to the atom what Darwin is to evolution, Newton to mechanics, Faraday to electricity and Einstein to relativity. His pathway from rural child to immortality is a fascinating one”

Dr John A.Campbell of the Physics Department, University of Canterbury,
New Zealand and the author of the book, "Rutherford : Scientist Supreme"



Ernest Rutherford was one of the first and most creative researchers in atomic physics. He is regarded as one of the greatest experimentalists of all times. He was also great scientific theorista, whose ideas were based on rigorous experimentation. Einstein called him “a second Newton.” Rutherford’s pioneering discoveries shaped modern science, created nuclear physics and changed our understanding about the structure of the atom. He discovered the transmutation of elements that is elements are not immutable, they can change their structure naturally by changing from heavy elements to slightly lighter elements. He was first to split the atom, he converted nitrogen into oxygen. He discovered alpha and beta rays. He set forth the laws of radioactive decay. He identified alpha particles as helium nuclei. Rutherford proposed the nuclear model of the atom. Rutherford’s model, a small nucleus surrounded by orbiting electrons, became the basis for how we see the atom today.

His many other lesser known discoveries such as dating the age of Earth were enough to make a scientist famous. The first method invented to detect individual nuclear particles by electrical means, the Rutherford-Geiger detector, evolved into the Geiger-Muller tube. The modern smoke detector can be traced back to 1899 when, at McGill University in Canada, Rutherford blew tobacco smoke into his ionisation chamber and observed the change in ionisation

Among his associates were the following 12 Nobel Laureates: Edward Appleton, Patrick Blackett, Niels Bohr, James Chadwick, John Cockroft, Peter Kapitza, Cecil Powell, George Paget Thomson, Ernest Walton, Otto Hahn, G de Hevesy and Frederick Soddy. Among his other famous students were H. G. J. Moseley and Chaim Weizmann. Moseley, who died in action in the First World War in 1915 at the age of 27, demonstrated the fundamental importance of the atomic number. Moseley described Moseley's law for frequency of x-ray spectral lines.

Rutherford had an extraordinary capacity of work. His students nicknamed him “the crocodile”, because they thought, “the crocodile cannot turn its head…it must always go forward with all devouring jaws.”

Rutherford in his appearance was far from a scientist. Weizmann described Rutherford as being “youthful, energetic, boisterous. He suggested anything but a scientist. He talked readily and vigorously on any subject under the Sun, often without knowing anything about it… He was quite devoid of any political knowledge or feelings, being entirely taken up with his epoch-making scientific work. He was a kindly person but did not suffer fools gladly.” James Chadwick wrote : “ In appearance Rutherford was more like a successful businessman or Dominion farmer than a scholar…when I knew him he was of massive build, had thinning hair, a moustache and a ruddy complexion. He wore lose, rather baggy clothes, except on formal occasions. A little under six feet in height, he was noticeable but by no means impressive…it seemed impossible for Rutherford to speak softly. His whisper could be heard all over the room, and in any company he dominated through the sheer volume and nature of his voice, which remained tinged with an antipodean flavour despite his many years in Canada and England. His laughter was equally formidable.”

Rutherford was born on August 30, 1871 at Bridgewater, a small town close to Nelson, New Zealand. His father James Rutherford, a Scottish wheelwright (a person who makes and repairs wheels and wheeled vehicles), had migrated with his family to New Zealand in 1840s. Rutherford’s mother Martha Rutherford (nee Thomson), who with her widowed mother, also emigrated to New Zealand in 1855. In 1877 Rutherford family moved to Foxhill, Nelson Province. Rutherford attended Foxhill School, Nelson Province (1877-1883). In 1883, the family moved to Havelock, Marlborough Sounds, also near Nelson, where Rutherford attended Havelock School (1883-1886). In his early years Rutherford did not show any special inclination towards science. Ioan James wrote: “In his spare time the boy enjoyed tinkering with clocks and making models of the waterwheels his father used in his mills. By the age of ten he had read a scientific textbook, but otherwise there was not yet any sign of special interest in science; he was expecting to become a farmer when he grew up.”

In 1887, Ernest won a scholarship to attend Nelson College, which was rather an English grammar school. This scholarship, which Rutherford won on his second attempt, was the only scholarship available to assist a Marlborough boy to attend secondary school. He studied three years at the Nelson College. He won, again on second attempt, one of the ten scholarships available nationally to assist attendance at a college of the University of New Zealand. This scholarship enabled him to attend the Canterbury College (1890-1894) in Christchurch. He studied Pure and Applied Mathematics, Physics, Latin, English and French. He was a regular player of rugby. He participated in the activities of a student debating society called the Dialectic Society. He also participated in the activities of the recently formed Science Society. In 1892 he passed BA.

His mathematical ability won him the one Senior Scholarship in Mathematics available in New Zealand. This made possible for him to study for his Master's degree. He studied both mathematics and physics. Rutherford was much influenced by one of his teachers Alexander Bickerton, who was a liberal freethinker. As a part of the physics course requirement Rutherford had to carry out an original investigation. Inspired by Nikola Tesla’s use of his high frequency Tesla coil to transmit power without wires, Rutherford decided to find out whether iron was magnetic at very high frequencies of magnetising current. As a part of this investigation Rutherford developed two devices; a timing device which could switch circuits in less than one hundred thousandth of a second and a magnetic detector of very fast current pulses. In 1893, Rutherford obtained a Master of Arts degree with double First Class Honours, in Mathematics and Mathematical Physics and in Physical Science (Electricity and Magnetism).

Rutherford wanted to be a school teacher. However, even after trying three times he failed to obtain a permanent school-teacher’s job. For a brief period he toyed with the idea of pursuing a career in medicine. He was also thinking to carry out more research in electrical science and to meet his financial requirements he thought of taking up private tutoring. Rutherford taught briefly at the local high school. In a tiny basement workshop Rutherford began investigating the radio waves earlier discovered by Hertz. He devised a magnetometer capable of detecting radio signals over short distances. The device could be used in lighthouse-to-shore communication. Rutherford did not knew that the device had already been developed by Joseph Henry. Rutherford decided to try for the scholarship given by the Royal Commissioners for the Exhibition of 1851. These scholarships allowed graduates of universities in the British Empire to go anywhere in the world and work subjects seemingly useful for industries in their home. For the graduate students of the Universities of New Zealand one scholarship was available every second year. A candidate had to be enrolled at the University for becoming eligible for applying for the scholarship. Thus in 1894 Rutherford returned to Canterbury College where he took geology and chemistry for a B.Sc degree. For the research work required of a candidate, Rutherford decided to extend his researches carried out for his MA degree. There were two candidates for the only scholarship available for the students of the New Zealand University—Rutherford and James Maclaurin of Auckland University College. The scholarship was first offered to Maclaurin. However, the terms of the scholarship were not acceptable to Maclaurin and so he declined the offer. Rutherford being the only other candidate was awarded the scholarship.

Rutherford left New Zealand in 1895. Before leaving New Zealand, Rutherford had established himself as an outstanding researcher and innovator working at the forefront of electrical technology. He decided to work with J J Thomson of Cambridge University’s Cavendish Laboratory. His decision to work with Thomson was influenced by the fact that Thomson was the leading authority of electromagnetic phenomena, in which Rutherford had developed an interest. Rutherford happened to be the Cambridge University’s first non-Cambridge-graduate research student.

Thomson, who was quick to realise Rutherford’s exceptional ability as a researcher invited him to become a member of the team to study of the electrical conduction of gases. Rutherford developed several ingenious techniques to study the mechanism whereby normally insulating gases become electrical conductors when a high voltage is applied across them. Rutherford used X-rays, immediately they were discovered, to cause electrical conduction in gases. He repeated his experiments with radioactive rays after their discovery in 1896. He became interested in understanding the the phenomenon of radioactivity itself. In 1898 Rutherford discovered two distinct radioactive rays—alpha and beta rays.
In 1898, Rutherford accepted a professorship at McGill University in Montreal, Canada. The laboratories at McGill were very well equipped. The laboratory was financed by a tobacco millionaire who considered smoking a disgusting habit. Rutherford described the laboratory there as ‘the best of its kind in the world’, and used it to work on radioactive emissions.

At McGill University, Rutherford’s first important discovery was radon, a radioactive gas and a member of the family of noble gases. In this he was assisted by his first research student, Harriet Brookes and R. B. Owens, McGill’s professor of electrical engineering. Rutherford jointly with Frederick Soddy discovered the disintegration theory of radioactivity, a phenomenon in which some heavy atoms spontaneously decay into slightly lighter atom. He, assisted by Otto Hahn, monitored the sequence of decay products. In 1904, Rutherford published his book on “Radioactivity”, in which he set forth the principles of radioactivity. This was the first textbook on the subject and which defined the fields for decades. The book was considered as a classic as soon as it appeared. Lord Raleigh while reviewing the book wrote: “Rutherford’s book has no rival as an authoritative exposition of what is known of the properties of radio-active bodies. A very large share of that knowledge is due to the author himself. His amazing activity in that field has excited universal admiration. Scarcely a month had passed for several years without some important contribution from his pupils he has inspired, on this branch of science; and what is more wonderful still, there has been in all this vast mass of work scarcely a single conclusion which has since been shown to be ill-founded….”

In 1907, Arthur Schuster offered to relinquish the Langworthy chair of physics at the University of Manchester on condition that Rutherford was invited to succeed him. The University authorities accepted the condition of Schuster and Rutherford accepted the offer. Rutherford spent fourteen productive years at the Manchester University. The discoveries made at the Manchester University included the demonstration of the identity of alpha particles as ionized (doubly positively charged) helium atoms (with his student Thomas Royds), a theory of scattering of alpha particles, and the nuclear model of the atom. Radioactivity was originally discovered by Henry Becquerel in uranium in 1896 and then in thorium by G. C. Schmidt (1865-1949). Subsequently two more radioactive elements viz., radium and polonium were discovered by Pierre and Marie Curi. Rutherford’s studies demonstrated that the radioactive emission consisted of at least two kinds of rays—alpha rays and beta rays. Later a third kind of radioactive rays, gamma rays was discovered. Rutherford jointly with Soddy proposed that radioactive decay occurs by successive transformation, with different and random amounts of time spent between ejection of the successive rays. The time spent may vary from years to a fraction of a second. The radioactive decay is a random process but it is governed by an average time in which half of the atoms of a given sample would decay.

At the Manchester University, Rutherford continued his researches on alpha particles at the McGill University. He and two of his colleagues Geiger and E. Marsden (1889-1970), were carrying out an experiment in which they shot alpha particles at a very thin piece of gold foil, in vacuum. To their surprise they found that most of the alpha particle passed through the gold foil in a straight line, some passed through the gold foil but changed their direction slightly and a small number (1 in 8000 particles) actually bounced back. Based on this experiment Rutherford concluded that the atom must be mainly empty space and that the positive charge was not spread out but it was located in the centre. Rutherford describing his astonishment at the results wrote: “It was quite the most incredible event that ever happened to me in my life. It was as incredible as if you fired a 15-inch shell at a piece of tissue paper and it came back and hit you. On consideration, I realized that this scattering backwards must be the results of a single collision, and when I made calculations I saw that it was impossible to get anything of that order of magnitude unless you took a system in which the mass of the atom was concentrated in a minute nucleus.” In 1911Rutherford proposed that atoms possess a very small but massive structure at their centre, holding all the positive charge that is required to balance the combined negative charge of all the electrons circling around the positively charged centre (nucleus). This was the first correct structure of the atom.

Rutherford’s research group at Manchester included Niels Bohr, who extended Rutherford’s model into the theory of atomic structure that became the guiding principle in nuclear physics for a decade; Gyorgy Hevesy, who developed the technique of radioactive tracers and defined the concept of isotopes; and Henry Moseley, whose work on characteristic X-rays established the concept and the significance of atomic number. While recalling his days at Rutherford’s laboratory at Manchester, Bohr wrote: “The effect (the large-angle scattering of alpha particles) though to all intents insignificant was disturbing to Rutherford, and he felt it difficult to reconcile with the general idea of atomic structure then favoured by the physicists. Indeed it was not the first, nor has it been the last, time that Rutherford’s critical judgment and intuitive power have called forth a revolution in science by inducing him to throw himself with his unique energy into the study of a phenomenon, the importance of which would probably escape other investigators on account of the smallness and apparently spurious nature of the effect. This confidence in his judgment and our admiration for his powerful personality was the basis for the inspiration felt by all in his laboratory, and made us all try our best to deserve the kind and untiring interest he took in the work of everyone. However modest the result might be, an approving word from him was the greatest encouragement for which any of us could wish.”

During the First World War (1914-1918) helped to mobilize British scientists for participating in the war effort. He led a delegation of British and French scientists to Washington. Rutherford worked on sonic methods for detecting submarines. In 1919, Rutherford returned to Cambridge to succeed Thomson as Cavendish Professor of Physics and Director of the Cavendish Laboratory at the Cambridge University. Within months after his return from the war research, Rutherford discovered that nuclei could be disintegrated by artificial means. He disintegrated nitrogen nuclei by striking with alpha particles into carbon nuclei. Later jointly with Chadwick, Rutherford showed that most light atoms could be broken by alpha particles. Like in Manchester, Rutherford built a strong research group at the Cavendish Laboratory. In addition to Chadwick, who on his own proved the existence of neutron in 1932, the group included John Douglas Cockroft (1897-1967) and Ernest Thomas Sinton Walton (1903-1995), who made the first the accelerator that disintegrated an atom with an accelerated particle beam; Charles Thomson Rees Wilson (1869-1959), the inventor of the cloud chamber; Patrick Maynard Stuart Blackett (1897-1974), the discoverer of positron; Pjotr Leonidovich Kapitza (1894-1984), who made the world’s most powerful magnet; and Francis Aston (1877-1945) who demonstrated experimentally the agrrement between apparent atomic and true isotopic weights.

Ray Spangenburger and Diane K. Moser wrote: “Rutherford’s idea of an atomic nucleus was a zinger, one for which he has earned the title, “the Newton of atomic physics”. It seemed to solve all the problems with the raisins-in-poundcake model of atoms. Yet even this model had a few problems. To build a more accurate vision of nature of the atom would require the application of an amazing concept called “the quantum” set forth by a somewhat dour German scientist named Max Planck. Like Roentgen’s X-rays, this idea would virtually turn physics upside-down, with implications not just for the concept of atoms, but virtually everything about our understanding of how world works.”

Rutherford was elected a Fellow of the Royal Society of London in 1903 at the early age of thirty-two. In 1904, he was awarded the Rumford Medal by the Royal Society. He was awarded the 1908 Nobel Prize “for his investigations into the disintegration of the elements, and the chemistry of radioactive substances”. He was given Nobel Prize in Chemistry and not in Physics. Arne Westgren, a chemist of the Swedish Academy of Science wrote: “Rutherford had also been suggested by several nominations for the Physics Prize, but at a joint meeting the two Nobel Committees decided that it would be most suitable, considering the fundamental importance of his work for chemical research, to award him the Prize for Chemistry.” Rutherford himself was very much surprised by the decision of the Nobel Foundation to award him Prize in Chemistry. In his Nobel banquet speech, on 11 December 1908, Rutherford said: “…. [he had] dealt with many different transformations with various periods of time, but that the quickest he had met was his own transformation in one moment from a physicist to a chemist.” He was knighted in 1914. He was awarded the Order of Merit in 1921. In 1922, he received the Copley Medal of the Royal Society. He served as the President of the Royal Society from 1925 to 1930 and subsequently he became the chairman of the important advisory council which had been set up to allocate public money for the support of scientific and industrial research in the United Kingdom. In1931, he was made Baron Rutherford of Nelson, a place in New Zealand from where he came. The element with atomic number 104 was named after Rutherford.

Rutherford died on October 19, 1937. He was buried in Westminister Abbey close to Isaac Newton. We would like to end this write-up by quoting James Chadwick on Rutherford. Chadwick wrote: “He (Rutherford)…a volcanic energy and an interest enthusiasm—his most obvious characteristic—and an immense capacity for work. A `clever’ man with these advantages can produce notable work, but he would not be Rutherford. Rutherford had no cleverness—just greatness. He had the most astonishing insight into physical processes, and in a few remarks he would illuminate a whole subject. There is a stock phrase—“to throw light on a subject.” This is exactly what Rutherford did. To work with him was a continual joy and wonder. He seemed to know the answer before the experiment was made, and was ready to push on with irrestible urge to the next. He was indeed a pioneer—a word he often used—at his best in exploring an unknown country, pointing out the really important features and leaving the rest for others to survey at leisure. He was, in my opinion, the greatest experimental physicist since Faraday.”

References

  1. Dardo, Mauro, Nobel Laureates and Twentieth-Century Physics. Cambridge: Cambridge University Press, 2004.

  2. Heilbron, J. L., “Rutherford, Ernest (1871-1937)” in The Oxford Companion to the History of Modern Science edited by J. L. Heilbron, Oxford: Oxford University Press, 2003.

  3. James, Ioan, Remarkable Physicists: From Galileo to Yukawa, Cambridge: Cambridge University Press, 2005.

  4. Jones, Geoff, Jones, Marry, and Acaster, David, Chemistry, Cambridge: Cambridge University Press, 1993.

  5. The Cambridge Dictionary of Scientists (second Edition), Cambridge: Cambridge University Press, 2002.

  6. Chambers Biographical Dictionary (Centenary Edition), New York: Chambers Harrap Publishers Ltd., 1997.