Augusto Righi was an Italian physicist who played an important role in the development of electromagnetism and, thus, indirectly influenced wireless telegraphy. Between 1893 and 1896, Righi developed Hertz’s work and made it more exact, using a new type of oscillator, which could generateelectromagnetic waves of a few centimeters.
Righi was the first experimenter to obtain double refraction ofelectromagnetic waves. Augusto Righi was born on August 27, 1850, in Bologna, Italy. He received his degree in engineering at the age of 22 from the Bologna University. He was teaching physics from 1873 to 1880 at the Bologna Technical Institute, from 1880 to 1885 at the Palermo University, and from 1885 to 1889 at Padua University and then at the University of Bologna. Augusto Righi was appointed to the Chair of Physics at the Faculty of Science, University of Bologna, in 1899. He taught in Bologna for 32 years and published more than 250 scientific papers.
Among them many related to electricity and electromagnetism (Righi’s papers on line):
– a group of papers on Volta effect (from 1874 to 1887)
– three memories on electric discharge in gases at atmospheric pressure (from 1876 to 1886)
– papers on theories of capacitors and induction machines (1879)
– a memory on magnetisation of steel (1880)
– two memories on electric shadows (1881-82)
– two memories on Kerr effect (starting from 1884)
– nine memories on photoelectric effect (1888-89)
– two memories on electromagnetic and electrodynamic forces (1889-1890)
– a series of memories on electric sparks (1891-92-95)
– a classical textbook of the Electromagnetism entitled “Optics of the electrical oscillations” (1897)
– a paper on the Zeeman effect (1898)
– two notes on an experimental method for the study of absorption of light in a magnetic field (1898)
– a paper on wireless telegraphy entitled “The wireless Telegraphy ” (1903)
– a paper on the electromagnetic mass of the electron (1906)
– a paper on movement in an electromagnetic field of a system electron-positive ion (1910)
– a book on “Electro-atomic phenomena in magnetic field” (1918)
Righi in his lab
Augusto Righi applied his talents to experimental work in electro-magnetic studies and solid-state physics. He was the first scholar to demonstrate the hysteresis effect of iron and magnetic materials and his contributions to the study of Hall and Kerr effects brought to light some basic aspects that were later explained later by electronic theory.
After Hertz announced his discovery of electromagnetic waves, Righi investigated them, especially their optical properties, and published the results in a treatise, Optice Elettrica, in 1897. He noticed that the smaller the spheres on the exciters, the shorter the waves, approaching those of light. Righi propagated electric waves as short as 2.5 centimeters, whereas Hertz had produced them 30 centimeters in length. Righi improved the Hertz oscillator that generated the waves; he placed the spark gap in vaseline oil and made the waves more consistent and steady.
Augusto Righi and Bernardo Dessau in the lab
Using his ‘sphere oscillator’ Augusto Righi carried out a series of famous experiments which proved Maxwell’s theories to be correct. This work was of fundamental importance in the training of the young scientist, Guglielmo Marconi, who carried out his early research in Righi’s laboratory.
Righi’s three sparks oscillator, c. 1900
Two columns of plastic material upon a black, painted, mahogany base vertically support the oscillating system through brass screw rings. Unlike Hertz’s oscillator, which used the oscillation of only one electromagnetic discharge in the air, Righi’s oscillator consists of a system with three sparks, and the oscillating discharge does not take place in the air.
The oscillator consists of four metal spheres, which are insulated from each other: the larger ones, each emerged halfway in paraffin oil, are in the centre and the smaller ones are at the extremities. By connecting the smaller spheres to the secondary circuit of a Ruhmkorff coil, the system starts oscillating: the interruption of the discharge in the paraffin oil electromagnetically induces an attenuated discharge in the opposite direction.
Every opening and closing of the coil’s switch, therefore, generates a new series of dampened oscillations. The oscillations are generated only in the case of an instantaneous discharge. The surface of the sphere must therefore be smooth to avoid leakages due to roughness. The immersion into the paraffin oil favours the production of an instantaneous discharge, a more uniform emission of electricity, and hampers the deterioration of the surfaces of the spheres caused by the sparks (in the case of Hertz’s oscillator the surface must be frequently cleaned).
The origin of this instrument is linked directly to the experimentalverification of the electromagnetic theory of light developed by the famous Scottish physicist J.C. Maxwell (1831-1879). The first experimental verification of this theory was made by the German physicist Henrich Hertz (1857-1894) who used an oscillator and a resonator to verify in a series of experiments (1886-1889) that the electric waves reflected, refracted and interfered just as beams of light do.
In his verification Hertz used mirrors, lenses, and prisms of very encumbering dimensions and also an oscillator with metal spheres that was able to produce a wave with a minimum length of 66 cm. A more accurate verification of Maxwell’s hypothesis was given only in 1893 by the physicist Augusto Righi of Bologna due to changes and improvements he had made to the instruments used. In particular, in order to reduce the wave length produced by Hertz’s oscillator and to reduce the size of the optical apparatus needed to prove the theory, he made a new oscillator, or a spark gap with three sparks, to reduce the capacity and the self-induction.
The oscillator consisted of two central metal spheres that emerged into a container filled with paraffin oil, through which the oscillatory discharge was produced. The idea was not new (Righi himself had mentioned the previous attempts by the Geneva physicists De la Rive and Sarasin). However, it quickly led the physicist from Bologna to work with wave lengths of about 10 cm until he produced microwaves that were 26 mm long and until he proved the complete analogy between the “electric waves” and the radiations of light and heat.
Augusto Righi contributed a new detector by cutting thin lines on the back of a mirror, dividing the metallic surface with a diamond point into narrow discontinuous strips. This provided a spark-distance much finer than could be attained by a micrometer gap, hence affording greater sensitivity.
Righi detector, c.1897
But it is said that Righi’s work in generation and detection of electric waves was not in itself as important as the fact that it was partly through him that Marconi found encouragement. Although Marconi was never enrolled as a student at the University of Bologna, he did hear Righi lecture. Actually, Augusto Righi and Guglielmo Marconi had close relations for a long period of time.
Augusto Righi and Marconi in Villa Griffone
During the last years of his life Righi began experiments on the conduction of gases under various conditions of pressure and ionization in magnetic field. From 1918 he concentrated on the Michelson-Morley experiment, criticizing it and suggesting modifications. He was fascinated by the theory of relativity, though he believed that the theory lacked convincing experimental support. Righi was a member of several national scientific associations, such as the prestigious Accademia dei Lincei.
Righi died in Bologna on June, 8, 1920.
Postal stamps memorizing Augusto Righi and his contribution to wireless telegraphy.