The Roofed Spherical Sundial and the Greek Geometry of Curves

Abstract

Greco-Roman sundials existed in a great variety of forms, but in most of the common types
the curves traced through the day by the Sun’s projection at the various stages of the year
were circles, straight lines, or conic sections, that is, the kinds of line most commonly investigated in Greek geometry. The variety known as roofed spherical sundials has day curves of a more complicated character; nevertheless, the mathematicians of the time could have investigated their properties by means of trigonometrical and projective resources attested in texts such as Ptolemy’s Almagest and Pappus’s Collection.

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