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The equinox takes place when the sun is even with the Earths Ecuador. It happens twice a year, March 20th or 21st and September 22nd or 23rd. At this point, the two poles of the earth are at the same distance from the sun, and this makes the sunlight fall equally on both hemispheres.
During the equinox, day and night are of the same length in all parts of the world and when this happens is the change of season.
The equinox at Chichen Itza, is a archaeo-astronomical phenomenon; the evening of March 21st and September 22nd, days before the begining of the spring and fall equinoxes respectively, one can see on the northern stairway of el Castillo at Chichen Itza a serpentine Solar projection, consisting of seven triangles of light, inverted, as a result of the sunset shadow cast by the nine platforms of the building.
Culminating with sunbeams illuminating the serpent’s head carved in stone at the base of the pyramid. It can be seen for 5 days around the time of the equinox, it begins about 3 hours before sunset when the light wave from above begins to close slowly to form seven isosceles triangles. These can be observed completed only 10 minutes before gradually disappearing.
This phenomenon represents the descent of the god Kukulkan, the local version of the feathered serpent, from the sky to the underworld through the world of men. The Mayans worshiped his presence on earth with offerings and religious services.
The rest of the pyramids facades are much damaged therefore no phenomenon of light and shadow is seen on them however it is likely that if restored, one would see the rise of the serpent in the equinoctial sunrises.
If you visit us in Bahia Principe Riviera Maya the third week of March, this is an event not to be missed!
Images source: El siglo de torreon