This amazing installation at the Tate modern in London is amazing, but as usual, with anything experimental it has been closed amid fears of people breathing in the ceramic dust,it will be the latest of a number of such headaches with interactive art in the Tate Modern's Turbine Hall. There was nervousness in 2006 when people slid down Carsten Höller's 24m slides, and a year later concern over Doris Salcedo's 167m crack in the floor led to signs being put up urging visitors to be careful.