SPACE.COM - Ancient Mexicans closely watching the sun from only a single location tracked the seasons and operated a farming calendar that fed millions.
The Mexica, or Aztecs, used the mountains located in the Basin of Mexico, now known as Mexico City, as a solar observatory. By keeping track of the sunrise against the peaks of the Sierra Nevada mountains, they achieved incredible accuracy in monitoring seasonal variations in weather, like dry springs and summer monsoons, and even accounting for leap years. Such precision was vital, as planting crops too early or too late could have been disastrous for the about 3 million people living in the Basin before the Spanish arrived in 1519.
"We concluded they must have stood at a single spot, looking eastwards from one day to another, to tell the time of year by watching the rising sun," Exequiel Ezcurra, an ecologist at the University of California, Riverside and lead author on the new research, said in a statement.