April 12, 2013
Maya Long Count, Modern European Calendars United By Wood
Brett Smith for redOrbit.com — Your Universe Online
Throughout history, different civilizations have had their own calendars they´ve used to mark time, with some civilizations going through multiple calendars during the course of their history.
"The Long Count calendar fell into disuse before European contact in the Maya area," said co-author Douglas J. Kennett, a professor of environmental archaeology at Pennsylvania State University. "Methods of tying the Long Count to the modern European calendar used known historical and astronomical events, but when looking at how climate affects the rise and fall of the Maya, I began to question how accurately the two calendars correlated using those methods."
In 1905, Joseph Goodman posited the Goodman-Martinez-Thompson (GMT) correlation that aligned the two calendars. After several modifications, scientists in the 1950s tested the method using early radiocarbon dating techniques. They found a wide range of error in the method, leaving the validity of GMT an open question.
Using a high-resolution, mass spectrometry carbon-14 dating and a calibration using tree growth rates, the scientists were able to show GMT is indeed correct.
To reach their conclusion, the researchers took four samples from an elaborately carved wooden ceiling found in the ancient Mayan city of Tikal. Because atmospheric carbon-14 is incorporated into a tree as it grows, the carbon-14 content of the wood varies as a reflection of the historical conditions the tree it came from experienced.
The samples were analyzed using the fluctuating calcium concentrations found in the incremental growth of the tree rings that are the result of fluctuating rainy seasons. The analysis allowed the scientists to fit four radiocarbon dates to the “wiggles” in the calibration curve, giving the team a more accurate age for connecting the Maya Long Count dates to the European calendars.
The entire process was made difficult by the differences in the atmospheric radiocarbon content between the northern and southern hemispheres.
"The complication is that radiocarbon concentrations differ between the southern and northern hemisphere," Kennett said. "The Maya area lies on the boundary, and the atmosphere is a mixture of the southern and northern hemispheres that changes seasonally. We had to factor that into the analysis."
After compensating for hemispheric differences, the team found the ceiling was carved between 658 and 696. They were also able to find a correlation with GMT European dates, indicating the GMT was a good method for linking the Long Count and European calendars.
After aligning the two calendars, the researchers noted in their report the events recorded in various Maya locations "can now be harmonized with greater assurance to other environmental, climatic and archaeological datasets from this and adjacent regions and suggest that climate change played an important role in the development and demise of this complex civilization.”
Unlike the European calendar date, which is based in days, months and years, the Long Count date is written as five components: Bak'tun (144,000 days), K'atun (7,200 days), Tun (360 days), Winal (20 days) and K'in (1 day).