ERNEST RUTHERFORD and the Birth of MODERN PHYSICS

By Matthew Wright

Scribe UK. 331 pages. £20. ISBN-13: ‎ 978 1 915590 96 1

Reviewed by Tony Roberts

The most well-known of twentieth century scientists are generally theoretical physicists. They are famous for overturning classical physics and introducing quantum mechanics, which has revolutionised technology and brought us everything from nuclear energy to electronics. The great experimental physicists on the other hand are not quite household names (Lisa Meitner and Louis Alvarez, for instance). Yet in the lab they are essential. They design experiments and apparatus, and test hypotheses. Of these, possibly the most famous — to layman like myself — are Marie Curie and the subject of Matthew Wright’s new book, Ernest Rutherford (‘the father of the atom’).

Readers of Wright are offered more than a biography. He also gives an accessible and brief introduction to what Thomas Kuhn famously described as a new ‘paradigm’ in physics (‘paradigm’ referring to ‘a major shift of theory’). This one began in the late nineteenth century and provides the context for an examination of Rutherford’s impressive contribution. Wright’s cast includes Newton and James Clerk Maxwell, as well as J.J. Thomson, the Curies, Einstein, Bohr (his one-time student) and Heisenberg, as well as collaborators and students whose work can be viewed as part of his legacy. Wright also offers ‘sidebars’ on such issues as ‘Explaining Ions’, ‘Electromagnetic Induction’, ‘Evolving Atomic Models 1808-1911’, and the ever contradictory ‘Schrödinger’s Cat’. Then there is a useful glossary.

In Newton’s worldview, space and time were absolute, electricity and magnetism were separate and hardly understood, and light consisted of corpuscles. In the 1860s, the Scottish physicist and mathematician Maxwell unified electricity and magnetism into a single theory and showed that electromagnetic waves, such as light, travel at a fixed speed determined by the properties of the vacuum.

Maxwell’s equations were not compatible with Newton’s ideas because they assume this fixed speed. This inconsistency later led Einstein to conclude that space and time must differ for different observers, giving rise to his work on relativity. Maxwell’s electromagnetism thus became one of the foundations of modern science.

Initially, however, as Wright relates, late nineteenth century physicists found themselves seeking to reconcile classical physics with Maxwell’s work. Defeated in that, they turned to applying his ideas firstly to the growing interest in radioactivity. This required new thinking and explanations of phenomena like the aether, which had been supposed a medium through which light travelled.  Now the push was to go deeper, to the fundamental particles being discovered by Rutherford through his data-rich studies of radioactivity and, subsequently, the nuclear atom.

Rutherford was born in 1871 in a New Zealand less primitive than his legend would have it, the fourth of twelve children of a farmer and flax mill owner and a schoolteacher. As a boy he built a camera, explored clocks and, under the influence of a science textbook, developed his lifelong interest in mechanisms and measurement. His education seems to have been a matter of high achievement and good luck with scholarships. These were vital, given the uncertainty of Rutherford’s father’s livelihood. The first took him to a boy’s boarding school, Nelson College (1887-89), the second to Canterbury College, where he earned a B.A., M.A., and B.Sc. Although the College was a small institution, the town of ‘Christchurch introduced Rutherford to metropolitan life.’ The ‘hot topic of the era’ was electrodynamics (the study of electromagnetic forces in motion). He spent six months on measuring the depth at which iron and other were metals were magnetised and then explored the rate at which magnetisation travelled through metal.

While modest, the young Rutherford was also very ambitious. His dream was to become a Fellow of the Royal Society and to win a Nobel Prize. Both of these he achieved. His major problem was that in the early days ‘he had trouble communicating clearly on the spot, meaning he struggled to perform well in exams and sell himself to potential employers’. Fortunately, the inventive brilliance he painstakingly applied to his work carried him through the challenges.

His experiments with a new form of radio receiver led to a major career boost. In 1895 Rutherford was awarded a fellowship at Cavendish Laboratory in Cambridge, England, where he met J.J. Thomson (‘very pleasant in conversation… not fossilised at all’) and where, in 1887, he was awarded a Research Degree. At Cambridge he continued exploring the potential of his electromagnetic detector. Eventually he turned from radio waves to Thomson’s interest in radioactivity. In both areas his competitors (Marconi and the Curies) had made international reputations before him. With Thomson he explored ‘ways that X-rays —which appeared to be an electromagnetic phenomenon—could further explore the nature of matter’. Thomson identified the first subatomic particle, the electron, in 1897. Through examining radiation emissions from uranium, Rutherford discovered two ‘rays’ (particles), the alpha and beta.

He had gained invaluable experience from Thomson, but found his dwindling funds a pressing problem. Consequently, he accepted a professorship in Canada in September 1898, two years before his marriage. At McGill University he continued his radiation studies (a by-product was a discovery which eventually led to ionising smoke detectors). One significant discovery was the ‘half-life’ of radioactive material. Rutherford also suspected, before he could prove by experiment, that the driving force behind radiation was the energy inside atoms, which were thought at the time to be solid. Ever competitive, he pushed his team to beat the Curies to the secret of radioactivity. He was at the same time generous in crediting the work of collaborators, much of which he had in fact instigated.

In 1907 Rutherford returned to England to take a chair at the Victoria University of Manchester.  Here he would be closer to the heart of science investigation, while also being able to disseminate discoveries through his papers more readily. The following year came the Nobel Prize in Chemistry for his work on the atom. Experiments led him to develop a model of its basic structure in which a tiny nucleus held the mass and empty space filled the rest. Around this nucleus, he predicted lightweight, negatively charged particles (Thomson’s electrons), orbiting like planets. In 1911 Rutherford identified the nucleus through gold-foil alpha-scattering experiments conducted by his assistants Hans Geiger and Ernest Marsden under his direction. With the coming of the war, he was redirected to work for much of the time on what would ultimately become sonar.

In 1917 Rutherford performed the first artificial nuclear reaction, converting nitrogen into oxygen. He had shown that ‘radioactivity was the result of the natural breakdown in certain elements.’ In the process, ‘having disintegrated the nucleus,’ which was responsible for it, ‘he confirmed the existence of a new subatomic particle, which he later dubbed the proton’ (He would predict the neutron in 1920). The importance of this was ground-breaking: ‘Ernest Rutherford’s explanation of radioactivity was a pivotal moment in the history of modern physics. For the first time a physicist had fully overturned classical conceits with an irrefutable array of hard data, showing that the new approach —in which everything was reconsidered in terms of electromagnetic theory —was able to produce valid explanations. And he had done so with irrefutable evidence built from painstaking research. In the process Rutherford laid the essential foundations for both nuclear physics and the broader field of particle physics.’

As Wright explains, all along Rutherford had been on ‘a consistent journey of exploration across a single broad theme’. His preoccupation with the nucleus of the atom was his attempt to understand what he was observing. While his discoveries informed the work of the theoretical physicists like Einstein, Bohr and others, as an experimentalist, a hands-on man, Rutherford could be amused or cynical about the role of theorists.

In 1920 he left Manchester to take over the Cavendish laboratory, where his administrative duties led him to rely on assistants even more than previously. At the same time, ‘The main problem that Rutherford and other experimentalists shared by the late 1920s was less to do with theory than the hard fact that long-standing methods for investigating the sub-atomic world were reaching their limits.’ Much more power was needed to investigate the nucleus. They needed to design equipment which could accelerate charged particles to enormous velocities to smash the particles into atoms, in order to observe the tracks of energies that emerged. This would lead to the first cyclotron in 1931 (and then eventually to the synchrotrons like the Large Hadron Collider at CERN).

During a visit to Sydney in 1925, Rutherford was described as a ‘tall, clear-eyed florid giant with boyish personality. absolutely radiating optimism… six feet of cheerful New Zealander.’ In 1931 he became Lord Rutherford. He died six years later. At his death, Einstein paid the generous tribute of describing him as ‘a second Newton’.

Matthew Wright’s ERNEST RUTHERFORD and the Birth of MODERN PHYSICS is both very informative and a pleasure to read. Warmly recommended.