How to identify modern sculptures?

'Art cannot be modern. Art is primordially eternal." Modern art represents an evolving set of ideas among a number of painters, sculptors, writers, and performers who - both individually and collectively - sought new approaches to art making. Although modern art began, in retrospect, around 1850 with the arrival of Realism, approaches and styles of art were defined and redefined throughout the twentieth century. Practitioners of each new style were determined to develop a visual language that was both original and representative of the times.