Early history of cosmic particle physics

The discovery of cosmic rays is a standard example of ‘one man’s noise is another man’s signal’. From the apparently minor leakages of electricity from well-insulated detectors came a subject of great importance for modern science: the detection of a so-called ‘radiation’ coming from not just beyond the Earth’s atmosphere but from deep cosmic space. Furthermore, a radiation of energy density rivalling that of starlight. Our goal is to examine the history of the subject from the period of ‘pre-discovery’ in the years from 1900 to 1912, through the discovery itself up to the 1940’s when particle physics was continued with accelerators. The crucial role of ‘new techniques’, principally the Wulf electrometer and the Wilson cloud chamber and their use in precission studies by Hess, Kolhörster, Anderson and Blackett are described. The arguments about the veracity of Hess’s claim for an extra-terrestrial origin are included, as well as the developments leading to the inspired discovery of the positron and the muon. The question of ‘origin’ is also examined, from the contention by Hess that the Sun was not responsible, to the idea – still held – that supernovae are involved.