"Get your head out of the clouds," we're sometimes told when we're daydreaming – but it's dreamers who have shaped our world. Without humanity's daydreamers, we'd still be in the Dark Ages: no advanced technology, no human rights, no deeper understanding of the universe. Dreamers make us stop and think, and they even keep us entertained – because it's dreamers, perhaps, who best understand what makes us laugh and cry.
, one of the modern world's greatest dreamers, died two years ago today. In his honor, we present a quiz about him and his fellow visionaries, the folks who have proudly stuck their heads in the clouds in order to make the world better.