Where is the sun at noon?


Where is the sun at noon?


Submitted by


Michel Darche
Regis Goiffon

Have you already remarked that the middle of the day (or solar noon) is not always at the same time on your watch? The sunset is sooner on December 10 than at the winter solstice. If you observe the Sun at noon every day, then its position draws a figure eight curve, called analemma, with endpoints at the winter and summer solstices.

The equation of time is the difference between the solar noon and the official noon.

This difference is explained by two phenomena:

  • Since Kepler, we know that the orbit of the Earth is an ellipse with the sun located at one focus. The Earth travels faster when it is closer to the sun, i. e. during the boreal winter: the real days are then shorter than the official days.
  • The Earth’s axis is at an angle of 23.5 ° with respect to the axe normal to the plane where it rotates around the Sun (the ecliptic plane). The solar days are then longer than the mean days around the summer and winter solstices. 

These daily differences add up during the year.

This module is part of the MPE exhibition. You can rent this module for a lumpsum fee. A detailed manual how to rebuild this module will be shared.


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