Four Thousand and Seven Horizons (2007) by Lizzie Hughes
From the artist's statement
4,007 photographic images (one for each ten Kilometers of the earth's circumference) were sourced from photo sharing websites. The images, largely holiday snaps, were cropped to exclude any geographical, architectural or other reference points and the resulting images re-scaled (so that the horizon ran directly through the center of the frame) before being ordered on a time-line according to color. With the images being sourced from unknown locations across the globe, the work aims to document an imaginary line, which ultimately describes the curvature of the earth.