Imagine a flat, 2-dimensional world, where everyone and everything exists on a planer surface, able to see all around, except, that is, for up or down. The late 19th-century writer, Edwin Abbott Abbot called such a place “Flatland,” in his novel of the same title. To the inhabitants of Flatland, a square appears to be an impenetrable border. There doesn’t seem to be any way in or out. To a being of three dimensions, the square is open, and its borders are not barriers at all.