The rare clock that follows the equation ...

  • Piazza Dante Alighieri, Napoli, Italia
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What we call noon is actually a Conventional noonday. Conventional because each solar day does not have the same duration as the previous one,therefore the instant noon, would always be different.A difference of a few seconds but if calculated over a span of months can be as much as 15 minutes. The difference between solar noon and conventional noon on Mars for example can be as much as 50 minutes.The equation of time precisely encapsulates this difference. The entrance to Vittorio Emanuele Boarding School in Dante Square is surmounted by a Torrino with two clocks. The very small clock, made in 1853, is unique in Europe because it precisely marks the equation of time. ( During the course of the year, the time indicated by a sundial fluctuates with respect to its regular flow indicated by a clock by a value ranging from +16 minutes and 33 seconds (between October 31 and November 1) to -14 minutes and 6 seconds (between February 11 and 12), moving from -3' 66" (between May 13 and 15) to +6' 53" (July 25 and 26). This deviation is called the equation of time and is the consequence of the combined action between the tilt of the axis and the eccentricity of the Earth's orbit. The visual representation of this equation is the analemma or by another name lemniscate, when the sine wave closes forming an eight). The other planets also have their own specific equation of time.

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