Artist Katie Paterson deals with themes of time, space and nature. For her Future Library project, she has secured authors including Margaret Atwood, Karl Ove Knausgaard, Elif Shafak and Han Kang to each create a piece of writing which will only be revealed 100 years from the time of writing. She talks to Danielle Radojcin about how the authors responded differently to the brief, how the public can participate, and how the mysterious project is evolving in response to environmental threats and taken on a life of its own.