Among other interests, Robert A. Millikan, Caltech cofounder and the Institute’s first Nobel laureate, was captivated by a kind of radiation initially believed to emanate from Earth. When electric charges associated with it were detected in the air, this cast doubt on its earthly origins. Millikan helped design a tiny electroscope to record charges at extreme altitudes. He had four built in the Caltech physics shop in 1922 and sent them aloft via balloons. Data from the two that reached the stratosphere suggested that the radiation must originate in space. Millikan dubbed it “cosmic rays.” The name stuck, although scientists later proved that the radiation is made of charged atomic fragments rather than rays.
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Recording Electroscope
From the Archives: Among other interests, Robert A. Millikan, Caltech cofounder and the Institute’s first Nobel laureate, helped design a tiny electroscope to record electrical charges at extreme altitudes.
