the Maya knew the time taken by the moon to orbit the earth. Their estimate of this period was 29.528395 days - extremely close to the true figure of 29.530588 days computed by the finest modern methods.11 The Mayan priests also had in their possession very accurate tables for the prediction of solar and lunar eclipses and were aware that these could occur only within plus or minus eighteen days of the node (when the moon's path crosses the apparent path of the sun).