How to Know Sunrise and Sunset times from a Sun Clock and Calendar (SCandC)

E. E. MOLA; I. M. IRURZUN; P. L. DAMMIG QUIÑA

Physics Education

Institute of Physics (IOP)

Año: 2011

0031-9120

The purpose of this article is to describe the construction of a Sun Clockand Calendar (SCandC) that will allow an Observer of it not only to know the timebut also the simmetry properties of the Sun-Earth relative movement. A set of circlesdrawn on the SCandC will allow the Observer to know their associated dates as wellas to perform a visual interpolation between any pair of consecutive circles to estimatean intermediate date. By introducing the Sunrise and Sunset Horizon Lines in theSCandC the Observer will be able to know the Sunrise and Sunset times during mostof the year. The Observer will also be able to appreciate the difference in time durationbetween the Spring -Summer and Autumn - Winter periods, as a consequence ofKepler´s Second Law as well as to observe that there is a small difference betweenthe circle radius of equidistant dates from the solstices in the Spring- Summer vsAutumn-Winter periods as a consequence also of Kepler´s Second Law The equationsderived in the present article will be tested against data from a particular Lighthouse.