A Sundial that Shows Solstice

Reply Tue 26 Jun, 2012 08:37 am
A Sundial that Shows Solstice
Image Credit & Copyright: Jean-Marc Mari

Explanation: What time is it? If the time and day are right, this sundial will tell you: SOLSTICE. Only then will the Sun be located just right for sunlight to stream through openings and spell out the term for the longest and shortest days of the year. And that happened last week and twice each year. The sundial was constructed by Jean Salins in 1980 and is situated at the Ecole Supérieure des Mines de Paris in Valbonne Sophia Antipolis of south-eastern France. On two other days of the year, watchers of this sundial might get to see it produce another word: EQUINOXE.

Sundial of the month July

Streak-of-light sundial

In this horizontal sundial in France, streaks of light are used to read the sundial.

The streaks are produced each hour by the central system of metal sheets.
It is easy to see that the main direction of all those sheets is equal to the direction of an ordinary pole style.

On each hour, the sun is in a specific shadow plane.

The sheets are so arranged that every hour, for a short time, the sun can shine through the openings between the sheets, producing a streak of light.

There are a large number of cut-aways in the construction. They form the word equinoxe around the beginning of spring and autumn, and the word solstice around the beginning of summer and winter.

This streak-of-light sundial is less suited to read intervening time. For this reason, there is an ordinary sundial on the other side, as shown below.

Fer de Vries

Design: Jean Salins de Marseille
Address: Ecole des Mines, Sophia Antipolis, Frankrijk
Source: Internet


On two other days of the year, watchers of this sundial might get to see it produce another word:


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