cosmic radiation


August 15, 2022

Cosmic rays, also called cosmic radiation, are subatomic particles from outer space whose energy is very high due to their great speed. They were discovered when it was found that the electrical conductivity of the earth's atmosphere is due to ionization caused by high-energy radiation. In 1911, Victor Franz Hess, an Austrian physicist, showed that atmospheric ionization increases proportionally to altitude. He concluded that the radiation must have come from outer space. The discovery that the intensity of radiation depends on altitude indicates that the constituent particles of the radiation are electrically charged and that they are deflected by the Earth's magnetic field. Ernest Rutherford and his collaborators, contrary to and prior to Hess's experiences, assumed that the ionization observed by the spectroscope was due to terrestrial radioactivity, since, measurements made in 1910 at the base and apex of the Eiffel Tower, That's how they detected it. Robert Andrews Millikan coined the expression cosmic rays after his own measurements, which concluded that they were indeed of very distant origin, even outside the solar system.


After the discovery of radioactivity by Henri Becquerel in 1896, it was accepted that atmospheric electricity —air ionization— was caused exclusively by radiation generated in turn by radioactive elements in the ground and by radioactive gases or isotopes of radon that those produce. Subsequent measurement, during the 1900s to 1910s, of the ionization rate (rhythm of air ionization) with respect to altitude showed a decrease that could be explained by the absorption of ionizing radiation by intervening air.


In 1909, Theodor Wulf developed the first electrometer. This was an instrument designed to measure the rate of ion production within a hermetically sealed container. Wulf used this instrument to show that the levels of ionizing radiation at the top of the Eiffel Tower were higher than at its base. However, his article, published in the Physikalische Zeitschrift, did not find wide acceptance. In 1911, Domenico Pacini observed simultaneous variations in the rate of ionization over a lake, over the sea, and at a depth of 3 meters below the surface. From the observed underwater descent, Pacini concluded that some of the ionization is due to sources other than terrestrial radioactivity.[1] Later, in 1912, Victor Hess raised three improved-precision Wulf electrometers[2] to an altitude of 5,300 meters using a hot air balloon and found that the rate of ionization was approximately four times higher than that which could be measured at ground level. from the ground.[2] Hess also ruled out the Sun as the responsible radiation source by re-ascent in a balloon during a near-total solar eclipse. When the Moon was blocking most of the visible solar radiation, Hess was still able to measure an ionization rate increasing with height,[2] and concluded: "The best explanation for the result of my observations is given by the assumption of that radiation of enormous penetrating power enters our atmosphere from above". In 1913-1914, Werner Kolhörster confirmed Hess's first observations by measuring the increase in the rate of ionization at 9 km altitude. Hess received the Nobel Prize in Physics in 1936, for his discovery.[3][4] Hess's balloon flight took place on August 7, 1912. Exactly 100 years later, on August 7, 2012, the Mars Science Laboratory vehicle measured ionizing radiation levels for the first time on another planet using its RAD ( Radiation Assessment Detector.