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The French physicist Charles Augustin de Coulomb made three reports on electricity and magnetism to France’s Royal Academy of Sciences. His third paper described an experiment with a torsion balance, which showed that the device would spontaneously discharge due to the action of the air rather than defective insulation. -
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The first evidence for radioactivity – images formed by Becquerel’s uranium salts -
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Julius Elster and Hans Geitel designed a key experiment where they found that surrounding a gold leaf electroscope with a thick metal box would decrease its spontaneous discharge. From this observation, they concluded that the discharge was due to highly penetrating ionizing agents outside of the container. -
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On 30 June 1905 the German physics journal Annalen der Physik published a paper by a young patent clerk called Albert Einstein. The paper, Zur Elektrodynamik bewegter Körper, (On the Electrodynamics of Moving Bodies) set out Einstein's theory of Special Relativity, which explains the relationship between space and time -
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In 1909 Theodor Wulf, a Jesuit priest, designed and built a more sensitive and more transportable electrometer than the gold leaf electroscopes. He measured the ionization of the air in various locations in Germany, Holland and Belgium, concluding that his results were consistent with the hypothesis that the penetrating radiation was caused by radioactive substances in the upper layers of the Earth’s crust. -
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To measure ionizing radiation away from the earth’s surface, several researchers took to the air in balloon flights in the first decade of the 20th century. One of these pioneers, Albert Gockel, measured the levels of ionizing radiation up to a height of 3000 metres. -
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Domenico Pacini making a measurement on 20 October 1910 -
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In 1911 and 1912 Austrian physicist Victor Hess made a series of ascents in a balloon to take measurements of radiation in the atmosphere. -
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In the 1920s, physicists were trying to apply Planck's concept of energy quanta to the atom and its constituents. -
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Using a cloud chamber, Dimitry Skobelsyn took the first photographs of tracks left by cosmic rays.