- Reeves, Richard.
A Force of Nature.
New York: W. W. Norton, 2008.
ISBN 978-0-393-33369-5.
-
In 1851, the
Crystal Palace Exhibition
opened in London. It was a showcase of the wonders of industry and culture of
the greatest empire the world had ever seen and attracted a multitude of
visitors. Unlike present-day “World's Fair” boondoggles, it
made money, and the profits were used to fund good works, including
endowing scholarships for talented students from the far reaches of the
Empire to study in Britain. In 1895, Ernest Rutherford, hailing from
a remote area in New Zealand and recent graduate of Canterbury College in
Christchurch, won a scholarship to study at Cambridge. Upon learning of
the award in a field of his family's farm, he threw his shovel in the
air and exclaimed, “That's the last potato I'll ever dig.” It was.
When he arrived at Cambridge, he could hardly have been more out of place.
He and another scholarship winner were the first and only graduate students
admitted who were not Cambridge graduates. Cambridge, at the end of the
Victorian era, was a clubby, upper-class place, where even those pursuing
mathematics were steeped in the classics, hailed from tony public schools,
and spoke with refined accents. Rutherford, by contrast, was a rough-edged
colonial, bursting with energy and ambition. He spoke with a bizarre
accent (which he retained all his life) which blended the Scottish brogue
of his ancestors with the curious intonations of the antipodes. He
was anything but the ascetic intellectual so common at
Cambridge—he had been a fierce competitor at rugby, spoke
about three times as loud as was necessary (many years later, when the
eminent Rutherford was tapped to make a radio broadcast from
Cambridge, England to Cambridge, Massachusetts, one of his associates
asked, “Why use radio?”), and spoke vehemently on any and
all topics (again, long afterward, when a ceremonial portrait was
unveiled, his wife said she was surprised the artist had caught him with
his mouth shut).
But it quickly became apparent that this burly, loud, New Zealander was
extraordinarily talented, and under the leadership of
J.J. Thomson,
he began original research in radio, but soon abandoned the field to
pursue atomic research, which Thomson had pioneered with his
discovery of the electron. In 1898, with Thomson's recommendation,
Rutherford accepted a professorship at McGill University in
Montreal. While North America was considered a scientific backwater in
the era, the generous salary would allow him to marry his fiancée,
who he had left behind in New Zealand until he could find a position which
would support them.
At McGill, he and his collaborator
Frederick Soddy,
studying the
radioactive decay of thorium, discovered that radioactive decay was
characterised by a unique
half-life, and
was composed of two distinct components which he named
alpha
and beta
radiation. He later named the most penetrating product of
nuclear reactions
gamma rays.
Rutherford was the first to suggest, in 1902, that radioactivity resulted from
the transformation of one chemical element into another—something
previously thought impossible.
In 1907, Rutherford was offered, and accepted a chair of physics at
the University of Manchester, where, with greater laboratory resources
than he had had in Canada, pursued the nature of the products of
radioactive decay. By 1907, by a clever experiment, he had identified
alpha radiation (or particles, as we now call them) with the
nuclei of helium atoms—nuclear decay was heavy atoms being
spontaneously transformed into a lighter element and a helium nucleus.
Based upon this work, Rutherford won the Nobel Prize in Chemistry
in 1908. As a person who considered himself first and foremost an
experimental physicist and who was famous for remarking, “All
science is either physics or stamp collecting”, winning the
Chemistry Nobel had to feel rather odd. He quipped that while he
had observed the transmutation of elements in his laboratory, no
transmutation was as startling as discovering he had become a
chemist. Still, physicist or chemist, his greatest work was yet to
come.
In 1909, along with
Hans Geiger
(later to invent the Geiger counter)
and
Ernest Marsden,
he conducted an experiment where high-energy
alpha particles were directed against a very thin sheet of gold foil.
The expectation was that few would be deflected and those only slightly.
To the astonishment of the experimenters, some alpha particles were
found to be deflected through large angles, some bouncing directly back
toward the source. Geiger exclaimed, “It was almost as incredible
as if you fired a 15-inch [battleship] shell at a piece of tissue paper
and it came back and hit you.” It took two years before Rutherford
fully understood and published what was going on, and it forever changed
the concept of the atom. The only way to explain the scattering results
was to replace the early model of the atom with one in which a diffuse
cloud of negatively charged electrons surrounded a tiny, extraordinarily
dense, positively charged nucleus (that word was not used
until 1913). This experimental result fed directly into the development
of quantum theory and the elucidation of the force which bound the
particles in the nucleus together, which was not fully understood until
more than six decades later.
In 1919 Rutherford returned to Cambridge to become the head of the
Cavendish Laboratory,
the most prestigious position in experimental
physics in the world. Continuing his research with alpha emitters, he
discovered that bombarding nitrogen gas with alpha particles would
transmute nitrogen into oxygen, liberating a proton (the nucleus of
hydrogen). Rutherford simultaneously was the first to deliberately
transmute one element into another, and also to discover the proton.
In 1921, he predicted the existence of the neutron, completing the
composition of the nucleus. The neutron was eventually discovered by
his associate,
James Chadwick,
in 1932.
Rutherford's discoveries, all made with benchtop apparatus and a
small group of researchers, were the foundation of nuclear physics.
He not only discovered the nucleus, he also found or predicted its
constituents. He was the first to identify natural nuclear transmutation
and the first to produce it on demand in the laboratory. As a teacher
and laboratory director his legacy was enormous: eleven of his students
and research associates went on to win Nobel prizes. His students
John Cockcroft
and Ernest Walton
built the
first particle accelerator
and ushered in the era of “big science”. Rutherford not
only created the science of nuclear physics, he was the last person to
make major discoveries in the field by himself, alone or with a few
collaborators, and with simple apparatus made in his own laboratory.
In the heady years between the wars, there were, in the public mind,
two great men of physics: Einstein the theoretician and Rutherford
the experimenter. (This perception may have understated the contributions
of the creators of quantum mechanics, but they were many and less known.)
Today, we still revere Einstein, but Rutherford is less remembered (except
in New Zealand, where everybody knows his name and achievements). And
yet there are few experimentalists who have discovered so much in
their lifetimes, with so little funding and the simplest apparatus.
Rutherford, that boisterous, loud, and restless colonial, figured out
much of what we now know about the atom, largely by himself, through a
multitude of tedious experiments which often failed, and he should
rightly be regarded as a pillar of 20th century physics.
This is the thousandth book to appear since I began to keep the
reading list
in January 2001.
February 2015 