The forward march of human knowledge has deepened our understanding of the universe and flung wide the floodgates of technological advance: we have established that the world came into being more than 4.5 billion years ago; we have deciphered the Rosetta Stone; travelled to the moon; eliminated smallpox and isolated the 'fat gene'. But in every domain of inquiry there remain a myriad things that we do not know, and which lurk tantalizingly beyond the bounds of our understanding. In The Things that Nobody Knows, William Hartston takes us on a guided tour of 501 gaps in our knowledge of cosmology, mathematics, animal behaviour, medical science, music, art, language and literature. As well as explaining our ignorance of the answers to such questions as 'What is Dark Energy?', 'Is colour a product of the mind?', 'Was there ever a real Pope Joan?' and 'Why are so many male giraffes gay?', he considers the likelihood of light being shed on these mysteries in the future. Both cerebrally satisfying and more-ishly dip-into-able, rigorously researched but also serendipitously playful, The Things that Nobody Knows is the perfect gift book for intellectually inquisitive people of all ages.