Friday, March 27, 2015

The Mayan Calendar

The Mayans are an incredible civilization that achieved amazing feats in science and astronomy; one of them was the development of the Mayan calendar. The Mayans were a pre-Columbian civilization located in Central America that was obsessed with the cosmos. That obsession influenced everything from their pyramids (which each had four 91-step staircases and a platform on top, making 365 steps in all) to when they were going to plant and harvest. Their astronomical knowledge was extremely advanced for their time; for example, they could predict solar eclipses and solstices hundreds of years in advance. For example, Harvey Bricker, author of "Astronomy in the Maya Codices," found a Mayan calendar that dated to the 11th or 12th century that accurately predicted a solar eclipse to within a day in 1991, centuries after the Mayan civilization had ended.

The Mayan calendar dates back to the 5th century BC and is still in use today in a few Mayan communities. The Mayan calendar actually does not consist of one but rather of three calendars: the Tzolkin, the Haab, and the Long Count. The Tzolkin is the divine calendar that consists of 260 days, divided into 20 periods of 13 days each. It was used to determine the time for religious ceremonies and it is related to nine moon cycles and the zenith of the Sun. The Haab is a 365 days solar calendar that is divided into 18 months of 20 days each and one month of five days. There is evidence that they knew that a year was not exactly 365 days but their primitive numerical system did not allow them to calculate the exact length of a year. The Long Count is an astronomical calendar that was used to calculate longer periods of time since the other two restarted every 52 years. The Long Count had a period of 1,870,756 days (5,125.36 solar years) or 13 b'ak'tuns, which was referred to as the universal cycle. It started on August 11, 3114 BC, the day the Mayans believed mankind was created and ended on December 21, 2012 with the universe destroyed and recreated. The mystery lies not in why the world did not end but how were they so precise to calculate the end to be exactly on the winter solstice.

The Mayans did not have complex instruments for charting the position of celestial objects; their observations were with the naked eye. They may have had rudimentary instruments such as crossed sticks but not instruments such as sextants. Although they did use their buildings as instruments, they aligned the temples to help observers monitor the position of celestial objects, like the Sun or Venus. Two of the corners pointed in the direction of the Sun (one pointed towards the Sun as it rose, the other as it set) so that on the Spring and Autumn equinox, at the rising and setting of the Sun, the corners of the structure casts a shadow in the shape of a plumed serpent or Quetzalcoatl along the west side of the north staircase. On these two annual occasions, the shadows from the corner tiers slither down the northern side of the pyramid with the Sun's movement to the serpent's head at the base.

Still the question arises: how did the Mayans do it? We still do not know exactly the answer to this question but it is truly amazing that they were able to do things like create extremely precise calendars, calculate the solstices and equinoxes, and calculate when the Earth and Mercury are aligned hundreds of years in advance.

- José Uribe