It is only since global media and digital communications became accessible to ordinary populations - with Telstar, jumbo jets, the pc and mobile devices - that humans have been able to experience their own world as planetary in extent. What does it mean to be one species on one planet, rather than a patchwork of scattered, combative and mutually untranslatable cultures? One of the most original and prescient thinkers to tackle cultural globalisation was Juri Lotman (1922-93). On the Digital Semiosphere shows how his general model of the semiosphere provides a unique and compelling key to the dynamics and functions of todays globalised digital media systems and, in turn, their interactions and impact on planetary systems.