Summary: Cosmic rays were discovered in 1912 by the physicist Victor Hess. The Earth is under constant bombardment from this radiation coming from beyond our atmosphere. Cosmic rays can cause damage to satellites and electronic devices on Earth, but the study of cosmic rays has led to major breakthroughs in particle physics. Today physicists are still trying to establish where these highly energetic particles come from. Melvyn Bragg is joined by Carolin Crawford, Gresham Professor of Astronomy and a member of the Institute of Astronomy at the University of Cambridge; Alan Watson, Emeritus Professor of Physics at the University of Leeds and Tim Greenshaw, Professor of Physics at the University of Liverpool.
