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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
- Dardo, Mauro, Nobel Laureates and Twentieth-Century Physics.
Cambridge: Cambridge University Press, 2004.
- 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.
- James, Ioan, Remarkable Physicists: From Galileo to Yukawa,
Cambridge: Cambridge University Press, 2005.
- Jones, Geoff, Jones, Marry, and Acaster, David, Chemistry,
Cambridge: Cambridge University Press, 1993.
- The Cambridge Dictionary of Scientists (second Edition), Cambridge:
Cambridge University Press, 2002.
- Chambers Biographical Dictionary (Centenary Edition), New York:
Chambers Harrap Publishers Ltd., 1997.
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