By assuming that each atom consisted of a small, positively charged central region (the nucleus) that was surrounded at great distance by orbiting electrons, Rutherford simultaneously transformed all previous scientific understanding of matter and established the world-changing new field of nuclear physics. Rutherford was born on August 30, 1871, near Nelson, New Zealand. Rutherford earned a scholarship in 1889 to Canterbury College of the University of New Zealand, Wellington, and graduated from that institution with a double master of arts degree in mathematics and physical science in 1893. The following year he also received a bachelor of science degree.
He received a scholarship in 1894 that allowed him to travel to Trinity College at Cambridge University, in England, where he became a research student at the Cavendish Laboratory under Sir Joseph John (J. J.)Thomson (1856–1940). Rutherford, a skilled experimental physicist, collaborated with Thomson in performing pioneering studies on the ionization of gases exposed to X-rays. In 1897, Rutherford received his B.A. research degree from Cambridge. A year later, he reported the existence of alpha rays and beta rays in uranium radiation. Throughout his long and productive career, Rutherford made many pioneering discoveries in nuclear physics. He also created the basic language scientists still use in describing radioactivity, emanations from the atomic nucleus, and various constituents of the nucleus, such as the proton and the neutron. His discovery of positively charged alpha rays and negatively charged beta rays in 1898 marked the beginning of his great contributions to the field.
Rutherford traveled to Montreal, Canada, in 1898 to accept the chair of physics at McGill University. In Canada, Rutherford found adequate samples of radium with which to conduct his research on radioactivity, especially alpha particle emissions. In 1900, Frederick Soddy (1877–1956) arrived at McGill and began his approximately two-year-long research effort under Rutherford. Their collaboration produced many papers and the all important disintegration theory of radioactive decay—sometimes called the law of radioactive decay. Their work associated radioactivity with the statistically predictable transformation of one radioactive element (the parent) into another (the daughter). Rutherford characterized the rate of transformation with a physical property he called the radioactive substance’s “half-life.” Early in the twentieth century, any hypothesis about the spontaneous transformation of matter might easily be viewed as nothing short of alchemy. However, Rutherford’s eloquence and skill as a researcher allowed the concept of radioactive decay to gradually take hold within the scientific community.
Rutherford was an inspiring leader who steered many future Nobel laureates toward their great achievements in nuclear physics or chemistry. Soddy, for example, would later (in 1913) introduce the Nobel Prize– winning concept of the isotope, which greatly relieved the growing confusion concerning all the “new” radioactive elements that were suddenly appearing. Otto Hahn (1879–1968) worked under Rutherford at McGill from 1905 to 1906. As a result of his research in Canada, Hahn became a more proficient radiochemist, who would go on to win a Nobel Prize for discovering nuclear fission in 1938. At McGill, Hahn discovered a number of new radioactive substances and was able to establish their positions in the series of radioactive transformations associated with uranium- and thorium-bearing minerals.
The complex radioactive decay phenomena exhibited by minerals containing uranium or thorium offered Rutherford a great challenge and a great research opportunity. He most capably responded to that challenge. In 1903, he became a fellow of the British Royal Society, and, in 1905, he published Radio-Activity, a book that influenced nuclear research for many years. Finally, he earned the 1908 Nobel Prize in chemistry for his “investigations into the disintegrations of the elements and the chemistry of radioactive substances.” As a physicist, however, he was a little unhappy that some of his best work in describing the phenomenon of radioactivity was perceived by the Nobel Prize Committee more as a breakthrough in chemistry than in physics. According to Rutherford, “All science is either physics or stamp collecting.”
He returned to England in 1907 and became professor of physics at the University of Manchester. Starting in about 1909, two students began a series of alpha particle–scattering experiments in Rutherford’s Manchester laboratory, the interpretation of which would allow Rutherford to completely transform existing knowledge of the atom. Rutherford had suggested an alpha particle–scattering experiment to the British–New Zealander scientist Ernest Marsden (1888–1970) and the German physicist Hans Geiger (1882–1945). Responding to their mentor, Marsden and Geiger bombarded a thin gold foil with alpha particles and diligently recorded the results. They were amazed when about 1 in 8,000 alpha particles bounced back in their direction. This should occur under J. J. Thomson’s “plum pudding” model of the atom, which assumed that the atom was a uniform mixture of matter embedded with positive and negative charges, much like raisins in a plum pudding. However, Rutherford quickly grasped the significance of these results and later remarked that this experiment was “as if you fired a 15-inch naval shell at a piece of tissue paper and the shell came right back and hit you.”
n 1919, Rutherford became director of the Cavendish Laboratory at Cambridge University. He transformed the famous laboratory into a world center for nuclear research and personally guided many future Nobel laureates, including John Cockcroft (1897–1967), Ernest Walton (1903–1995), and Chadwick, down promising avenues of investigation. Rutherford was knighted in 1914; King George V of Britain bestowed the Order of Merit (OM) upon him in 1925; and he was made First Baron Rutherford of Nelson, New Zealand, and Cambridge, England, in 1931. He died on October 19, 1937, in Cambridge as a result of postoperative medical complications. As a lasting tribute to the man who did so much to establish the field of nuclear physics, Rutherford’s ashes were placed in the nave of Westminster Abbey, near the resting places of two other great scientists, Sir Isaac Newton and Lord Kelvin. Element 104, identified in 1969 by researchers at the Lawrence Berkeley Laboratory in California, was named rutherfordium (Rf) in his honor.
Charles Thomson Rees Wilson (1869 – 1959)
