It has been 145 years since the birth of Ernest Rutherford, the discoverer of the atomic structure, who greatly contributed to the study of radioactivity and opened the era of nuclear research
“Einstein spoke of him with great respect, and used to call him Newton II. Unlike Einstein, who focused on precise calculations, Rutherford was an experimental genius, one of the biggest,” wrote the scientist Chaim Weizmann, who later became the first president of Israel and who knew the two physicists personally. “He had a sixth sense when it came to experimentation, and everything he touched – turned to gold.”
Ernest Rutherford was born on August 30th 1871 in the young British settlement in New Zealand; he was the fourth of twelve children to parents who were brought over as children from Britain to help establish the new colony. His father was an engineer and over the years focused on the professional production of flax string. His mother was a very popular teacher, and therefore Ernest and his siblings received a thorough education from both sides - his mother's teaching and his father’s technical and hands-on knowledge. The family was not rich, but Rutherford was able to put himself through high school thanks to scholarships for excellence, and then again for a bachelor's degree at the University of New Zealand in Christchurch. His level of excellence in mathematics and physics paved the way to an accelerated master’s degree track, and in 1893 he received a master's degree in both fields, with a specialization in electricity and magnetism.
During his studies he was influenced by Serbian-American inventor Nikola Tesla, a pioneer of the study of the relationship between electricity and magnetism. The young New Zealand student followed in his footsteps and developed two new devices - a simple device for measuring very short periods of time (1/100,000 of a second) by switching between electric circuits, and a magnetic detector for electric currents.
Despite his success in research, Rutherford had difficulty finding employment. He could not get a job teaching, and had to settle for giving private lessons to fund his research. Eventually he returned to university because he had heard about a scholarship that allowed students from all over the British Empire to study and work wherever they wish, in return for their contribution of knowledge to their country of origin.
Rutherford enrolled in undergraduate studies again, this time in geology and chemistry, and applied for a widely coveted scholarship, of which only one student from New Zealand was entitled, once every two years. Of the two candidates Rutherford’s opponent was chosen, James Maclaurin from the University of Auckland. But Maclaurin had just married and got a job in Auckland so decided to give up the scholarship, and it eventually was awarded to the only remaining candidate. Rutherford decided to take the opportunity to study at the prestigious Cavendish Laboratory at University of Cambridge.
Secrets of radiation
Rutherford came to Cambridge in 1895, and chose to work under the guidance of Joseph John Thomson (J.J. Thomson), a physicist who will later be remembered as the discoverer of the electron. He perfected the detector he built in New Zealandand turned into a radio-wave receiver. He also developed methods to transmit radio waves over long distances, and thus competed with Marconi, who today we recognize as the inventor of radio.
Rutherford later developed a method to detect electromagnetic radiation. By working together with Thomson, he demonstrated that treated with different gases, X-rays (X-rays were discovered shortly before) give off different electrical conductivity properties, and hence X rays are actually another form of light radiation, i.e. electromagnetic radiation. Today we know that the energy of the radiation destabilizes the gas atoms, causing them to absorb or emit electrons, turning them into ions – electrically charged atoms. Therefore it is called “ionizing radiation”.
In 1896, French physicist Henri Becquerel discovered a new type of radiation. When studying the properties of uranium salts, he spotted by chance that they caused photographic plates to turn black though they were not exposed to light, making him realize that they emit some kind of radiation. He continued his work on the study of radiation with the couple Pierre and Marie Curie, who coined the term - radioactivity (in 1903 Becquerel and the Curie couple were awarded the Nobel Prize in Physics for this discovery and for their research). Rutherford was also interested in this new radiation, and found that in fact there are two different types of radiation: alpha rays, which are very short range and are easy to stop even with a sheet of paper, and beta rays, which have a very long range and penetration capabilities allowing them to pass through even metal. Shortly afterwards it became clear that beta radiation is the flux of electrons - the newly discovered particle by Thomson (for which he received the 1906 Nobel Prize in Physics).
In 1898 Rutherford's research was again interrupted. The funds for the two-year scholarship he received had run out, so he had to obtain additional financing. The stringent rules of the University of Cambridge did not allow him to apply for a position before he had worked at the institution for four years (Cambridge changed this rule one year later). In the absence of funding for an additional year, Rutherford decided to travel to Canada, where he was offered a job at McGill University in Montreal. The position also allowed him to bring across Mary Georgina Newton, his fiancé from New Zealand. Their only daughter, Eileen, was born in 1901.
Breakdown and success
In Canada, Rutherford continued his study of radioactive radiation and discovered that it is also composed of a third kind of radiation. The new type of radiation (gamma) was even stronger than X rays – that is, its wavelength is shorter. He also discovered a radioactive gas that was unknown until then, radon. In the following years he continued work in Canada with the British scientist Frederick Soddy, and together they cracked the mystery of radioactivity, proving that in this process a heavy atom breaks down into two lighter atoms, with the emission of the smaller particles along with energy.
When he understood this fission process and studied its products, Rutherford conceived a method to calculate the age of geological samples according to the concentrations of radioactive material they contain, a method which its principles are still used today. These studies earned Rutherford world recognition in 1908 and he was awarded the Nobel Prize for his contribution to the study of decay of atoms and the chemistry of radioactive elements.
Ironically, Rutherford received the Nobel Prize in Chemistry, believing that the field was inferior to physics. Rutherford used to joke and say that of all the transformations (atomic) he investigated, the fastest change was from a physicist to a chemist.
In addition to the fame that the scientific progress brought Rutherford, he finally had financial well-being. Many universities and research institutions in the United States tried to woo him, while McGill University constantly increased his salary in order to remain competitive. The scientist who grew up in modest circumstances having to fight all his life for scholarships and living stipends, was finally free from financial worries.
Back to Britain
Only one thing bothered Rutherford while in Canada – the remoteness – the focus of global science was clearly in Western Europe. This was the main factor that motivated his return to Britain in 1907, and he got a job at the University of Manchester. There he completed the decoding of radioactive radiation demonstrating that alpha radiation is actually nuclei of helium atoms (we now know that they are composed of two protons and two neutrons). Together with his student Hans Geiger, Rutherford developed an electronic system to detect individual radioactive particles. This method is the basis for the radioactive measuring device developed later by Geiger, and to this day still named in his honor - the Geiger counter.
In 1914, Rutherford was awarded knighthood. Shortly after the First World War broke out. Sir Ernest joined the British Royal Navy and was commissioned to explore methods of acoustic technology to detect submarines. In this study he registered his only patent, underwater sonar, which belonged to the British Navy.
Towards the end of the war Rutherford returned to researching atoms. He bombarded nitrogen atoms with alpha particles, and discovered as a result some became oxygen atoms. Rutherford thus became the first person in history that changed the nucleus of an atom to achieve one element from another. However, all his achievements to date were dwarfed by his major breakthrough – deciphering the atomic structure.
The father of nuclear physics. Rutherford (on the right) at Cavendish Laboratory | Source: Science Photo Library
A nuclear secret
At this point, scientists knew that the atom consisted of positive heavy particles (protons) and negative light particles (electrons), but they did not know how they were arranged inside (the missing charged particle, the neutron, was only identified in 1932). Thomson proposed the most widely accepted atomic structure at the time, where negative particles lie like seeds of a watermelon in a positive mass (this model is sometimes called the “plum pudding model”, and compares electrons to raisins evenly dispersed in dough).
A series of brilliant experiments conducted mainly by Geiger and another student, Ernest Marsden, led by Rutherford, they fired a beam of alpha particles into a very thin sheet of gold, beyond which they placed a particle detector. The researchers hypothesized that if the model is right, the positive alpha particles will pass through the sheet of gold, because the negative charge and the positive atom itself will balance each other and not interfere with the particles that pass through. At first it seemed an accurate assessment. However, when they moved the detector they found that about one of 8,000 alpha particles could not pass through the gold but bounced backwards or sideways. The finding led Rutherford to reflect on the atomic structure, and he eventually came to the conclusion that most of the atom's mass is concentrated in the dense nucleus, which occupies only a fraction of the volume of the atom, and surrounding this are the electrons. This model explains why most of the alpha particles pass through the gold sheet, and only the few that hit the nucleus flew away. The most amazing finding was the understanding that the most of the atom is only vacuum. Scientists tend to simulate the atom as an empty football stadium, where the nucleus is like a tiny pea in the center of the field, and the electrons are only a small number of spectators running fast in the stands.
In 1919, Rutherford came full circle, replacing the Cavendish Lab director, Thomson, at University of Cambridge, where he first began his scientific endeavors outside of New Zealand. Among the other works of this period, it was Rutherford's partner Niels Bohr that predicted the existence of the neutron, which was officially discovered in 1932. He continued to nurture young researchers and felt great satisfaction when his successors completed the atomic model he developed. Rutherford was also very active in other areas, including the promotion of equal rights for women in Cambridge and contributed to helping new scientists get started all around the British Empire. In 1933 he contributed to helping scientists flee the Nazi regime.
In 1930, his daughter Eileen died from complications giving birth to her fourth son, when she was only 29. This tragedy overshadowed the rest of his life. At the age of 66, on October 19, 1937, he died from complications of an inguinal hernia. His ashes were buried in the basement of Westminster Abbey in London, along with other eminent scientists, including Sir Isaac Newton and Lord Kelvin. “His death is one of the largest losses in the history of British science,” eulogized by his former teacher, J.J. Thomson, who himself died three years later, exactly on Rutherford’s birthday, and was buried next to him.
Rutherford's name is commemorated in many ways: naming rights for education and research institutions, scholarships and scientific awards are in his memory, streets bear his name, the New Zealand one hundred dollar bill dons his portrait as well as craters on the Moon and Mars are named after him. In 1997, the chemical element number 104 was named after him, and he entered the short and most prestigious list of scientists commemorated in the periodic table.
Rutherford was a modest man, and many of his colleagues and his students said he had helped them in various fields and contributed to the advancement and development of their ideas without seeking recognition for himself. If they asked him, he would say the best commemoration is continuing his research. Indeed his many discoveries paved the way for nuclear fission of the atom, and the opening of a new era in science – the nuclear era.