Cosmic rays - 100 years of discovery
A century ago - as scientists raced to find out where different types of radiation came from - an Austrian physicist took his electroscopes up in a hot air balloon and made a discovery that was to change thinking for good.
High in the sky, Victor Hess discovered that background radiation came from space - and not, as had been thought, from the ground here on Earth.
Take a look at how cosmic rays were first understood - and see how far our knowledge has come since then - with Simon Peeters, a senior lecturer in Physics and Astronomy at the University of Sussex.
Continue reading the main storyClick bottom right for image information. Images courtesy Science Photo Library, Getty Images, Nasa, Google, Aspera and the Pierre Auger Observatory.
Music by KPM Music. Slideshow production by Paul Kerley and Darren Baskill. Publication date 8 August 2012.
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