The Great year has been a fascinating topic since Plato
The Great year also happens to match up with ( be coincident with ) wicked variations in global climate during ice ages etc., but has yet to be proven. While the mean temperature (integral) only varies a few degrees, the peak to peak variation (derivative) varies wildly during these periods.
The speculation has several larger and longer seasonal climate variations, gradually changing over thousands of years of cycle wave length impacting weather globally.
c00l chit