A young Austrian scientist named Victor Franz Hess rightly considers that these experiments are not sufficient. In 1912 he uses a free balloon to carry out measurements at higher altitudes. At 5300 meters, the signal had become twice as intense as on the ground.
Hess knows that his intuition was correct : the radioactivity at high altitudes comes from outer space, and when coming down it is attenuated by the dense layers of the lower atmosphere. This irrefutable experiment is improved by Hess himself who demonstrates that his result remains unchanged at night and during an eclipse.
Around Millikan the physicists are now convinced that new particles of various mass and charge are still to be discovered. Millikan himself coins the wording Cosmic rays for this new family of physical objects. The teams perfect their experiments in the labs : in 1932 Carl David Anderson working for Millikan identifies the positron, a particle of same mass as the electron but of opposite charge.
Millikan was awarded the Nobel Prize in Physics in 1923 for his measurement of the charge of the electron which is one of the most fundamental bases of modern physics and for his work on the photoelectric effect. Hess and Anderson shared the same award in 1936.
The Nobel medal and diploma of VF Hess, offered as usual in one lot, are estimated $ 300K for sale by Bonhams on June 7 in New York, lot 182. Let us remind that the Nobel medal and diploma attributed to James Chadwick in 1935 for the discovery of the neutron were sold for $ 330K including premium by Sotheby's on June 3, 2014.