We live in a world of three dimensions – up and down, side to side, and backwards and forwards, or any other three directions that are at right angles to each other. It’s easy to imagine something in one dimension, such as a straight line, or two dimensions, such as a square drawn on a sheet of paper. But how can we possibly learn to see in an extra dimension to those we’re familiar with? Where is this additional direction that’s perpendicular to the three we know?