The Museo Galileo’s Monumental Sundial restored thanks to OFFICINE PANERAI

Thanks to the support of Panerai, it has not only been possible to restore the original appearance of this fascinating artefact, which was designed by Luise Schnabel and Filippo Camerota and constructed in 2007, but also to create an interesting video explaining the operation of this complicated Sundial, available on the Museo Galileo

THE SUNDIAL OF THE MUSEO GALILEO

The sundial is an instrument of ancient origin for measuring time, consisting of a style mounted on a dial. It is read by observing the shadow produced by the style, making use of the fact that the Sun marks the passage of time by appearing to rotate uniformly round the Earth.

The sundial of the Museo Galilei consists of a dial traced on the pavement and a gnomon formed of two large bronze stele which symbolizes the day and the night. The stele for daytime, facing south, towards the Arno, contains a vertical meridian line on which the shadow of the tail of a “lucifer”, a fantastic animal half-lizard and half-snake, indicates midday for each period of the year. The stele for the night, facing north, contains a representation of the two constellations which enable the Pole Star to be identified: Ursa Major, the Great Bear, and Ursa Minor, the Little Bear. The wind rose at the base of the gnomon indicates the directions for geographical orientation.

On the ground, a meridian line of travertine marble and brass flanked by the signs of the zodiac in glass and marble extends for about 15 metres from the entrance of the museum, where the winter solstice is marked, to the base of the gnomon, where the summer solstice is marked. The curved lines of travertine marble which cross the meridian line indicate the date. The radial lines of brass, which form a grid with the curves of the solstices, indicate the hours.

The materials used for constructing the meridian symbolise the seasons and the four elements are marble for autumn and earth, glass for winter and water, the grey stone pietra grigia for spring and air, and bronze for summer and fire.

HOW IT WORKS

It is the shadow of the glass polyhedron mounted on top of the large bronze gnomon which indicates the time and the date. The hours from 9 a.m. to 2 p.m. are marked on the brass radial lines. The date is indicated by the transverse lines of travertine marble which mark the daily course of the Sun in various periods of the year, precisely when it enters each sign of the zodiac.

The length of the shadow cast by the gnomon varies with the passing of the days and the seasons, indicating true solar time in the place in which it is located; this is different from the time indicated by a watch or clock, which is known as mean time. True solar time has a periodic variation which can be a quarter of an hour or more compared to mean time.

In the period when summer time is in effect, in addition to the astronomical variations, one hour must be added to the time indicated. For example, true midday in the month of February will be indicated by the sundial at about 12, while in the month of July it will be at about 13.20 summer time.

To read the hour and the date, the hour line and the calendar curve closest to the gnomon’s shadow are identified. When the shadow does not fall exactly on an hour line, the halfhour or quarter-hour can be read reasonably accurately by dividing the space between the two hour lines into two or four parts. The date too can be read accurately by referring to the signs of the zodiac and to the beginning of the months marked along the meridian line.

OFFICINE PANERAI