The earliest sundials known from archaeological records are shadow clocks used in ancient Egypt and Babylon around 1500 BC. In about 700 BC, the Old Testament describes a sundial, the ‘dial of Ahaz’, in Isaiah 38:8 and 2 Kings 20:11. In 240 BC the Greek astronomer Eratosthenes made the first good measurement of the size of Earth. By noting the angles of shadows in two cities on the summer solstice, and using his knowledge of geometry, he made a remarkably accurate calculation of the Earth’s circumference. In Handbook for Contemporary Photography (1977) Arnold Gassan used the degree of definition of shadows (from very sharp to no shadows) to devise a four scale film development plan that controlled the density of highlights.
Photo: Sundial, Avignon, France, March 2011