A sundial is based on a pretty simple idea, but works pretty consistently. The post stuck into the base is called the gnomon. Gnomon is a Greek word for "one who knows". The sun hits the gnomon all through the day and the shadow lands on various lines on the base, revealing the hour. The curve of the sundial is flattest in the summer and widest in the winter because of the sun's angle. Follow our easy directions in the hands-on section to make your own!