Cosmic radiation is an umbrella term for all ionizing radiation located between
the celestial bodies in the universe. Cosmic radiation also hits the earth,
but the atmosphere ensures that most of the cosmic radiation does not reach the earth surface.
The energy of this radiation ranges from around 109 electronvolts to
several times 1020electronvolts.
The name, coined by the American physicist Robert Andrew Millikan (1868 - 1953),
is derived from the Greek word kosmos (κόσμος), meaning "world".
History
In 1912, the Austrian physicist Victor Franz Hess (1883 - 1964) carried
an electrometer to an altitude of 5300 m in a free balloon flight.
He found the ionization rate increased fourfold over the rate at ground level and
concluded that the radiation enters from outside our solar system into the atmosphere.
