ABSTRACT
Astronomers were limited to studying radiation in the visible range of the electromagnetic spectrum. Cosmic rays were discovered in 1912 by the Austrian physicist Victor Hess, who was anxious to find out why electrometers at ground level always recorded a certain amount of background. Gamma rays represent the most energetic form of electromagnetic radiation, at wavelengths shorter than those of X-rays – that is to say, below 0.01 nm. For obvious reasons, no optical telescope can detect X-rays, because the X-ray photons would simply penetrate the telescope mirror. Ultra-violet observations were subsequently made from the American satellites of the orbiting astronomical observatory series. Infra-red astronomy has become a vitally important part of modern research. Radio waves from the Sun were first detected in 1942 by a British team led by J. S. Hey; originally the effects were thought to be due to German jamming of British radar.
