In 'The War of the Worlds' by H.G. Wells, a brutal alien army invades Earth, intent on colonising the planet  First published as a novel in 1898, the story tapped into fears that advances in technology would herald a new age of warfare. It was a critique of imperialism, written in journalistic style. A 1939 radio adaptation by Orson Wells caused panic. Today we continue to believe we may not be alone in the universe, making this a science fiction classic.